33. Bacteriology Flashcards

Question

Where are teichoic acids found?

Answer 1

In the peptidoglycan of Gram-positive bacteria.

Answer 2

* Wall teichoic acid -\> Reaches out from the peptidoglycan layer * Lipoteichoic acid -\> Reaches down from the peptidoglycan layer to the lipid layer of the cell membrane

Answer 3

* Highly variable anionic polymers in the peptidoglycan layer of Gram-positive bacteria * They play a role in: * Cell shape, growth and division * Resistance to antimicrobial peptides

Answer 4

Gram-negative

Answer 5

It is a lipid bilayer: * Inner layer -\> Mostly phospholipids * Outer layer -\> Mostly lipopolysaccharides (LPS)

Answer 6

* Forms a selective barrier against bile and antimicrobial agents * Allows for formation of outer membrane vesicles (OMVs), which can have immunomodulatory effects

Answer 7

It is the target site for the insertion of the membrane attack complex (MAC) and bacterial lysis by complement.

Answer 8

* Elicits inflammatory responses in humans * Elicit complement activation via the alternative pathway * Are involved in virulence and pathogenesis, by for example: * Allowing attachment and invasion * Acting via molecular mimicry to appear like host cells

Answer 9

* Lipid A (endotoxin) * Polysaccharide part: * Core polysaccharide -\> Usually conserved within a species * O antigen -\> Repeating polysaccharide of variable length

Answer 10

* H. pylori -\> Mimic Lewis blood group * Campylobacter -\> Mimic GM1 ganglioside

Answer 11

* It is the Lipid A part of a lipopolysaccharide (LPS) * It leads to systemic inflammatory response syndrome (SIRS): * Fever * Hypotension * Disseminated intravascular coagulation (coagulation of blood throughout the body) * Activation of complement and macrophages In other words, it is responsible for many of the roles of LPS in Gram-negative bacteria.

Answer 12

Endotoxins can bind to: * TLR4 on the surface of host cells -\> Leads to inflammatory cytokine production * Caspase-4 receptors on the inside of cells -\> Leads to cell apoptosis Endotoxins are targeted by antimicrobial peptides (AMPs).

Answer 13

* Helps with identification of bacterium * Susceptibility to complement, drugs and antibiotics * Impacts on immune activation and evasion

Answer 14

* Pathogen-associated molecular patterns / Microbe-associated molecular patterns * These are small molecules that are conserved in all microbes, and activate innate immune responses, protecting the host from infection * They bind to recognition receptors on host cells, including: * TLRs * NLRs * Lectins * RIG‐I

Answer 15

* Peptidoglycan -\> For both types of Gram bacteria * Lipopolysaccharides (LPS) -\> For Gram-negative bacteria

Answer 16

* Toll-like receptors * They are receptors on host cells that play a role in the innate immune system -\> They bind PAMPs/MAMPs, which are highly-conserved sequences in microbes that mark them out as foreign

Answer 17

1. Capsule 2. Flagella 3. Pilli 4. Secretion systems 5. Toxins

Answer 18

* High molecular weight polymers on the surface of bacteria * They are structurally diverse and can be structural mimics of host molecules * They are important in resistance to the host's immune response

Answer 19

They can be targeted by conjugate vaccines.

Answer 20

It lies outside of the cell wall.

Answer 21

* In *Streptococcus pneumoniae* (Gram positive), the capsule provides some resistance to phagocytosis. * In *Neisseria meningitidis* (Gram negative), the capsule provides some resistance to complement lysis (since the complement pathway results in assembly of the MAC complex on the outer membrane of Gram negative bacteria)

Answer 22

Polysaccharides

Answer 23

* Long, thin filaments involved in bacterial motility (swimming/swarming) * Enable bacterial movement through rotation of the filament

Answer 24

* Basal body -\> Embedded in the inner and outer membrane of a Gram-negative bacterium. It can spin to allow movement. * Hook * Filament

Answer 25

The proton motor force (chemiosmosis).

Answer 26

* Spin up to 15,000rpm * Move up to 60 body lengths/sec

Answer 27

Flagellin: * A globular protein that arranges itself in a hollow cylinder to form the filament in a bacterial flagellum. * It is the principal component of bacterial flagellum, and is present in large amounts on nearly all flagellated bacteria.

Answer 28

* It is a MAMP, since it is a TLR5 ligand * Therefore, it can be used as an adjuvant (agent that improves the immune response of a vaccine) in vaccines, since it stimulates local inflammation and immune response

Answer 29

* Filament-containing structures on the surface of bacteria that are projections of the cell membrane * They have important roles in adhesion

Answer 30

Repeating units of pillin

Answer 31

* They are essentially the same * Short pili are also known as fimbriae and are higher in number than long pili

Answer 32

Gram negative

Answer 33

Adhesive tip structures having a shape corresponding to that of specific glycoprotein or glycolipid receptors on a host cell -\> e.g. they might have a lectin domain.

Answer 34

* Pap pilus -\> Upper UTI (kidneys) * Type I pilus -\> Lower UTI (urethra, prostate, bladder)

Answer 35

Type I pilus causes lower UTIs: * The lectin domain of the FimH tip adhesin of the type I pilus of UPEC (uropathogenic E. coli) binds to mannosylated uroplakins (found on plaques) in the bladder. * This allows the UPEC to bind to the bladder, causing the UTI. * Understanding this structure allows the design of anti-infectives.

Answer 36

Multi-protein systems that allow a wide range of substrates to be secreted from the cytosol into the extracellular space.

Answer 37

The cell membrane(s) of bacteria. In Gram-negative bacteria, there is the inner and outer cell membrane, so there is an extra challenge.

Answer 38

* Cell entry [IMPORTANT] * Attachment * Replication * Anti-phagocytic

Answer 39

* Found in many different Gram-negative bacteria * Type 3 secretion systems transport substrates across 3 cell membranes -\> The inner cell membrane, outer cell membrane and the cell membrane of the host * They have a basal body (like flagella do), needle and translocon * Essentially they can be viewed as syringes that pump toxins directly into the host cell * The exact function of the secretion system varies between bacterial species, depending on what substrates are secreted

Answer 40

Factors which poison or intoxicate host cells, killing them or altering their function.

Answer 41

* Exotoxins -\> Secreted protein toxins * Endotoxins -\> Lipopolysaccharides (LPS) from the outer membrane of Gram-negative bacteria (cell-associated)

Answer 42

* In some cases, yes. * In these cases, the disease can be replicated by simply injecting the toxin, and the bacteria causes disease only by release of the toxin. * For example, diphtheria toxin can cause the same changes to the tonsils as diphtheria bacteria. * In other cases, there are many factors involved in the disease.

Answer 43

\*Make sure to add more notes on this!\*

Answer 44

* Capsules -\> Bacterial resistance to phagocytosis and complement * Flagella -\> Motility and activate inflammatory responses * Pili -\> Adhesion to host receptors * Type 3 secretion systems -\> Cell entry/avoidance of phagocytosis * Toxins -\> May be sufficient to mediate disease

Answer 45

No, some cannot be Gram stained. For example: * Mycoplasma -\> Has no cell wall * Chlamydia -\> Intracellular pathogen * Spirochetes -\> Too thin to be visualised * Mycobacterium tuberculosis -\> 'Acid fast', so Gram stain does not get through outer membrane

Answer 46

1. Primary staining with crystal violet -\> Penetrates the cell wall of bacteria, regardless of their structure 2. Staining with Gram's solution -\> This is a mixture of potassium iodide and iodine, which reacts with the crystal violet stain, forming large complexes 3. Decolourisation using alcohol -\> This leads to the break down of the outer membrane in Gram-negative bacteria, so the stain can leak out. In Gram-positive bacteria, the peptidoglycan layer is thicker, so the stain is retained more. 4. Counter staining -\> A red/pink saffranin or carbol fuschin stain is added, allowing Gram-negative bacteria to be seen. Result: * Gram-positive bacteria stain purple * Gram-negative bacteria stain red/pink

Answer 47

A harmless member of the flora.

Answer 48

A commensual in a mutually beneficial relationship.

Answer 49

An organism that is able to cause disease.

Answer 50

* Primary pathogens -\> Cause disease as a result of their presence or activity within the normal, healthy host, and their intrinsic virulence is a necessary consequence of their need to reproduce and spread * Opportunistic pathogens -\> Normally commensal and do not harm the host, but can cause disease when the host's resistance is low.

Answer 51

The degree of damage inflicted by a pathogen.

Answer 52

Lacking virulence.

Answer 53

The number of micro-organisms required to cause disease.

Answer 54

*Staphylococcus aureus* can act as: * Commensal -\> In the airways of about 20% of the population * Opportunistic -\> It can cause line infection (when germs enter the body through a tube placed in a vein to deliver nutrients and medicine) * Primary pathogen -\> It can cause septic arthirits in some patients

Answer 55

The outcome depends on: * Bacterium * Host * Route of infection * Dose * Co-infection Note how the outcome of an infection is dependent on **both** pathogen factors and host factors (such as host innate immunity).

Answer 56

Bacteria that can be pathogens or commensals, depending on conditions.

Answer 57

Commensal bacteria are highly specialised and exist in a highly competitive community, so they are not very genetically diverse, while bacteria in general are very diverse.

Answer 58

* Gram-positive anaerobic bacteria that do not cause disease. * The bacteria are diverse, but are SPECIFIC in the characteristics (i.e. many different types, but all similar) * The few pathogens that are found there are highly specialised, with additional attributes encoded by extra DNA that non-pathogens do not have

Answer 59

Protection against pathogens

Answer 60

* Tropism * Replication * Evasion of immune killing * Toxicity * Transmission (between hosts) * Aquisition of nutrients

Answer 61

The ability of a bacterium to find and establish a niche (intracellularly or extracellularly).

Answer 62

Four criteria that were designed to establish a causative relationship between a microbe and a disease.

Answer 63

In order for a microbe to be confirmed as the cause of a disease: * The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms. * The microorganism must be isolated from a diseased organism and grown in pure culture. * The cultured microorganism should cause disease when introduced into a healthy organism. * The microorganism must be reisolated from the diseased experimental host and identified as being identical to the original specific causative agent. In other words, it's checking at lots of different stages that a pathogen is the one causing the disease.

Answer 64

A set of criteria that must be satisfied to show that a gene found in a pathogenic microorganism codes for a product that is the cause of a given disease. (It differs from Koch's postulates in that Koch's postulates seek to find the microbe causing disease, while molecular Koch's postulates seek to find the exact genes causing disease)

Answer 65

Stanley Falkow

Answer 66

Virulence factors

Answer 67

In order to prove that a gene is the virulence gene that causes a disease, it must be shown that: * The virulence factor is expressed by the pathogen * Deletion of the gene causes attenuation of the virulence * Complementation with the gene should restore virulence

Answer 68

* Respiratory * Faecal-oral * Direct contact * Vector borne

Answer 69

* *Vibrio cholera* * *Clostridium difficile*

Answer 70

Gram negative curved bacterium (O-antigen possessing)

Answer 71

Symptoms: * Sudden onset of fast, watery diarrhoea * No blood or mucous -\> Loss of electrolytes (Described as rice water stool) * May cause death Treatment: * Fluid replacement

Answer 72

Cholera toxin is a type of AB toxin: * It is an A1B5 toxin, so for every 1 A subunit there are 5 B subunits * A subunit is the active component * B subunit allows binding to host cells (remember: B for binding) -\> Binds to GM1 ganglioside

Answer 73

* It releases AB toxins (exotoxins) * The B subunits bind to GM1 gangliosides so the toxin enters the host cell * The A subunit ribosylates G proteins, which maintains them in their active state * Therefore, adenylate cyclase activity is high and cAMP is increased * This opens ion channels in the membrane, leading to loss of chloride ions * Water follows, resulting in diarrhoea

Answer 74

* Toxins that are secreted by certain bacteria, including: * Cholera * Diphtheria * Pertussis toxin (associated with whooping cough) * E. coli * They consist of B subunits, for attachment to the host cell, and A subunits for toxicity within the cell

Answer 75

Gram positive rod, spore-forming

Answer 76

Symptoms: * Diarrhoea * Inflammation of colon * May cause death Treatment: * Stool transplant * Antibiotics

Answer 77

It often follows a course of antibiotics.

Answer 78

Toxin A: * Enterotoxin * Enters host cell via apical surface Toxin B: * Cytotoxin * Enters host cell via basolateral surface In each toxin, there is an enzymatic domain, translocation domain and binding domain.

Answer 79

* The bacterium releases two types of exotoxin -\> Toxin A and toxin B * Both bind to host cell receptors via binding domain -\> This leads to endocytosis into an endosome * The endosome is acidified inside the cell * This leads to cleavage of the toxin, so that the translocation domain is free to insert itself into the membrane of the endosome * This releases the enzymatic domain of the toxin out of the endosome * The enzymatic domain glycosylates G proteins (rho GTPases), which inactivates them * Somehow this leads to diarrhoea and inflammation

Answer 80

The host receptors that *C. diff* binds to were discovered by genome-wide CRISPR–Cas9-mediated screens.

Answer 81

* *Staphylococcus aureas* * *Neisseria meningitidis*

Answer 82

* Surface proteins -\> Tropism + Immune evasion * Secreted proteins -\> Toxicity + Immune evasion

Answer 83

Gram positive

Answer 84

For tropism: * MSCRAMS (microbial surface components recognizing adhesive matrix molecules) -\> Collection of proteins that bind to ECM proteins (such as elastin, colagen, fibronectin) For immune evasion: * Protein A -\> Binds to Fc subunit of IgG, rendering the antibody useless * Coagulase -\> Bind fibrinogen and prothrombin (and activate prothrombin), leading to clot formation around the bacteria. This allows it to reside there and protect it from the immune system.

Answer 85

They are covalently linked to peptidoglycan.

Answer 86

Sortase enzyme attaches the proteins via peptide bonds: * The sortase recognises specific sequences at the C-terminus of the membrane proteins -\> This is an LPXTG motif * It uses this motif to cleave the protein and then attach it to the peptidoglycan by a peptide bond The identification of the LPXTG motif by Olaf Schneewind allowed for the genome to be searched for other potential surface proteins, and therefore search for new vaccine candidates.

Answer 87

* Repeating units of the bacterial receptor bind to repeating units of the matrix proteins -\> Although the interaction is weak, the cumulative avinity is strong * Altering the structure of matrix proteins (such as fibrinogen) -\> This is recognised by integrins, which then mediate uptake of bacteria into cells

Answer 88

* The bacterium secretes inhibitors of complement -\> These act by preventing activation of C5 * There are surface-expressed proteins that target other parts of complement -\> e.g. Levels of immunoglobulins + Inhibitors of C3 conversion

Answer 89

A toxin that targets the small intestine (i.e. the **entero**cytes)

Answer 90

* Enterotoxins -\> Leads to gastroenteritis (food poisoning) * TSST-1 -\> Leads to toxic shock syndrome (TSS) * Exfoliation toxin -\> Leads to Staphylococcus scalded skin syndrome

Answer 91

* A type of bacterial toxin that act by inappropriately activating T-cells. * They do this by forming cross-bridges between MHC molecules on antigen-presenting cells and the T-cell receptor (between conserved regions). * This leads to non-specific activation, leading to mass release of cytokines and upregulation of T-cell activity

Answer 92

Non-O-antigen possessing Gram negative coccus, typically residing in the upper airway

Answer 93

* It is found in about 10% of the population and it does not cause disease in most * In some individuals, it causes severe systemic disease that may involve bacterial meningitis.

Answer 94

There are two features: * The bacterium reaches very high concentrations in the systemic circulation (up to 10¹³ bacteria/individual) * The bacterium blebs (sheds membrane vesicles) as it grows within the body -\> This frees up endotoxin lipid A (part of LPS) from the Gram-negative outer membrane

Answer 95

* The immune response is mainly via the complement pathway * We know this because of high rates of meninogcoccal disease in individuals with complement pathway defects

Answer 96

* The alternative pathway of activation acts as an amplification loop * It is kept in check by negative regulators, such as factor H

Answer 97

* Due to the capsule, of which there are 13 serogroups: * In serogroup B, the bacterial capsule has alpha 2‐8 linked polysialic acid -\> This is the same molecule that is on neural cell adhesion molecule 1 in infancy, meaning that the immune system does not respond to it -\> Molecular mimicry * This also means that vaccines against serogroup B strains are not feasible * The bacteria can also bind complement factor H (via factor H binding protein) -\> This factor is responsible for downregulating complement, so the bacteria are less susceptible to complement. * The bacteria is regulated by temperature via RNA thermocensors -\> These are sequences in the untranslated region of mRNA that fold into a hairpin loop if the temperature is low, so that no translation can happen. If the temperature rises, the RNA is translated.

Answer 98

* These are sequences in the untranslated region of mRNA that fold into a hairpin loop if the temperature is low, so that no translation can happen. * If the temperature rises, the RNA is translated. * Therefore, the immune defence mechanisms are only switched on when the temperature is high (like in the systemic circulation).

Answer 99

Where injection of effectors by the bacterium in the host cell cytoplasm triggers large-scale cytoskeletal rearrangements and ruffles formation allowing the bacterium to be engulfed and internalized. For example, *Shigella* bacterium does this.

Answer 100

* Listeria * Shigella * Salmonella * Mycobacteria * Coxiella * Legionella * Mycobacterium

Answer 101

Once taken up by a phagocyte, the bacterium is within an endosome, which the phagocyte plans to fuse a lysosome with. The bacteria can avoid this by: * Escaping the endosome -\> Shigella, Listeria * Prevent fusion with the lysosome -\> Salmonella, Mycobacteria * Being able to survive in the phagolysosome -\> Coxiella, Legionella, Mycobacterium

Answer 102

* Has a cell wall containing mycolic acids * This prevents fusion of the lysosome with the phagosome that the bacterium is in, so it can survive

Answer 103

* The inflammasome is a complex within host cells that acts to detect and respond to intracellular pathogens * The foreign stimulus binds to a sensor protein, which acts via an adaptor to set off an effector * The effector leads to cleavage of inactive proteins within the cell that they lead to an inflammatory response -\> Cytokines become active * Gasdermin D is also activated -\> This leads to cell lysis (in essence this is tactical suicide of the cell)

Answer 104

* It is a pro-molecule in host cells, in the inactivated state at rest since it is folded over on itself * It is activated by cleavage by inflammatory caspases in response to intracellular pathogens * One domain polymerises to form pores in the cell membrane that lead to cell lysis -\> This is a form of cell suicide in order to protect the cell when it is infected, which also releases inflammatory cytokines

Answer 105

* A form of programmed cell death that occurs when a cell is invaded by intracellular pathogens * It leads to increased inflammatory response due to release of cytokines

Answer 106

It is a way for the pathogen to avoid immune responses.

Answer 107

O-antigen-possessing Gram-negative intracellular bacteria

Answer 108

* *Shigella* -\> Colon * *Salmonella* -\> Small intestine

Answer 109

* Cross the epithelial barrier via M-cells (sentinel antigen-presenting cell that present antigens to macrophages underlying them) * These M-cells are phagocytic by nature * After this, the bacteria are then taken up by macrophages, in which pyroptotic cell death happens (in the case of *Shigella*) * *Sa**lmonella* tend to prefer to stay in the macrophages and replicate there, while *Shigella* prefer to escape * After this, the bacteria invade epithelial cells through the basolateral membrane using the **type 3 secretion system** * Finally, the cell undergo cell-to-cell spread to adjacent cells

Answer 110

* They can lead to inflammatory diarrhoea * This is because they cause pyroptotic cell death (of phagocytes), which leads to release of cytokines that attract neutrophils * This leads to the breakdown of the integrity of the epithelial barrier

Answer 111

It has the ability to polymerise actin, forming foci behind it. This polymerisation of actin drives the movement of the bacterium.

Answer 112

* *Shigella* -\> Cell entry * *Salmonella* -\> Cell entry / Replication

Answer 113

It is encoded in a plasmid, by a 30kb entry region.

Answer 114

* It evolved from *E. coli* 4 separate times, so there are now 4 strains. * Each time this involved the uptake of a plasmid.

Answer 115

Shigella was the bacteria in which LPS activating caspase 4 (and thus causing pyroptosis) was detected. (Shi, 2014)

Answer 116

* LPS -\> Binds to caspase 4 -\> Pyroptosis * Peptidglycan -\> Binds to Nods -\> Inflammasome activation -\> Pyroptosis + Cytokine release

Answer 117

There are two type 3 secretion systems: * For entry -\> SPI-1 * For intracellular replication -\> SPI-2

Answer 118

* The importance of the SPI-2 type 3 secretion system can be deomonstrated by viewing wild-type *Salmonella* and SPI-2 mutant *Salmonella* with green fluorescent protein to demonstrate growth. * The wild-type replicates much faster inside a macrophage, showing the role of SPI-2 in *Salmonella* replication.

Answer 119

*Listeria* -\> Causes food poisoning and more serious diseases in the immunocompromised, elderly and pregnant women

Answer 120

Enter by a zipper mechanism: * Bacteria just adhere to the host cell and then sink into the cell and enter. * This is mediated by internalin A and internalin B After this, the bacteria escape the phagosome (via pores they form) and undergo motility due to actin-mediated motility (manipulation of host cytoskeleton).

Answer 121

(Welch, 2002) Extensive mosaic structure revealed by the complete genome sequence of uropathogenic *E. coli*: * The paper took 3 isolates of *E. coli*: * Standard lab strain * K12 strain (used for cloning in the lab) * Uropathogenic strain * They found that only 40% of genes were core genes, common to all of the strains * The rest were accessory genes that make each strain unique * Therefore, there is a LOT of variation within a species

Answer 122

* The pangenome is the entire gene set of all strains of a species. * It includes genes present in all strains (core genome) and genes present only in some strains of a species (variable or accessory genome).

Answer 123

* Transformation * Transduction * Conjugation

Answer 124

* Cell-to-cell contact between two different strains of bacteria * DNA is transferred via a plasmid * The DNA coding for a mating bridge is on a plasmid * The conjugation machinery recognises an OriT (origin of transfer) on the plasmid * The plasmid is made into a single strand of DNA, before being transferred across * In the recipient, the DNA is made to be double-stranded, so that both the recipient and donor have the plasmid

Answer 125

Many Gram-positive and Gram-negative bacteria, particularly enteric bacteria.

Answer 126

* Transformation is when bacterial cells take up DNA from the environment * Double-stranded DNA in the surroundings are broken down into single-stranded DNA * This single-stranded DNA is then taken up by specific uptake mechanisms

Answer 127

* Neisseria * Streptococcus

Answer 128

* Genes from the bacterium are incorporated into the genome of a bacterial virus (bacteriophage) * The genes are then carried to another host cell when the bacteriophage initiates another cycle of infection

Answer 129

Many Gram-positive and Gram-negative

Answer 130

They have an innate immune system to combat it.

Answer 131

* It uses a range of restriction enzymes * The restriction enzymes cut up DNA which is transduced into the bacterium by phages * It recognises foreign DNA because it is not methylated (most bacterial DNA is methylated by methylases), so the bacterium's DNA is not cut up

Answer 132

CRISPR/Cas: * When a cell is infected by a phage, the sequences of the phage are cut up by the Cas endonuclease and integrated into the CRISPR repeats * The spaces between the repeat sequences form the sequence specificity of the recognition of repeat invasion * This means that the spacing pattern acts as an identifier of any infection in the future [CHECK THIS AND ADD MORE]

Answer 133

Clustered regularly interspaced short palindromic repeat

Answer 134

* The source of DNA for lots of horizontal gene transfer is unknown * In our gut, it is believed to be our own flora that contributes a large amount of DNA, particularly for antibiotic resistance, etc.

Answer 135

It can confer properties such as antibiotic resistance, and lots of virulence is due to that.

Answer 136

* Intergenomic variation is where DNA is introduced into a bacterium from an external source * Intragenomic variation is where DNA mutates or is altered within the bacterium itself

Answer 137

* Point mutation * Phase variation * Antigenic variation

Answer 138

* It is the on/off switching of genes, without changing the sequence. * It is heritable, but it can be reversed!

Answer 139

* Inverter elements * Homopolymeric tracts

Answer 140

* Example: The expression of Type 1 fimbriae in *E. coli*, a fim switch is used to control whether the fimbriae are expressed * If the fim element is inverted, then the promoter elements in the fim do not line up with the fimbriae gene, so it is not expressed * FimB encodes an invertase that switches between the inverted and non-inverted alignment

Answer 141

* Example: In *Neisseria meningitidis*, expression of PorA (an outer membrane protein) is controlled by homopolymeric tracts * Homopolymeric tracts are lengths of repeated nucleotid, either in the promoter or in the open reading frame (ORF) * DNA polymerase has relatively low affinity over repeating sequences, so the length of the tract can increase or decrease during replication * This causes the gene to shift in or out of frame * This can be reversed in subsequent rounds of replication * Aside from this, PorA can be interrupted by insertion of mobile DNA within the bacterium, which enters the ORF and stops translation

Answer 142

The mechanism by which a bacterium alters the proteins or carbohydrates on its surface and thus avoids a host immune response.

Answer 143

The sequence of a gene coding for a protein can change by: * Point mutation * Uptake of DNA by horizontal gene transfer

Answer 144

* Mostly surface structures * But also restriction/modification systems -\> This means that certain bacteria would be more prone to uptake DNA by horizontal gene transfer thatn others

Answer 145

They can't change the genes on purpose, but the bacteria can sense the environment and change gene expression in response.

Answer 146

A fall in intra‐cellular iron levels triggers de‐repression of diphtheria toxin gene.

Answer 147

Bacteria's ability to detect and to respond to cell population density by gene regulation.

Answer 148

Once the bacteria reach a high population density and the stationary phase, the bacteria show bioluminescence.

Answer 149

* Gram positives: Peptides * Gram negatives: Secondary metabolites

Answer 150

* There is evidence that bacteria in the gut can produce decoy molecules that can throw-off the quorum sensing of pathogens, which eliminates them. * This study looked at *Bacillus* as the probiotic (Piewngam, 2018)

Answer 151

* Two component systems are very simple systems used in basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions. * How it works: * Sensor kinase in the membrane detects change in environment * The kinase domain phosphorylates a response regulator, which leads to a response

Answer 152

Interferes with growth and reproduction of a ‘microbe’.

Answer 153

Reduces or eliminates harmful bacteria.

Answer 154

Antibiotics are a type of antimicrobial.

Answer 155

Kills bacteria.

Answer 156

Halts bacterial growth.

Answer 157

The idea that an antibiotic must be effective against the bacterium but not against the host.

Answer 158

* Target not present in the host * System/structure is different from the host * Differential access of target (i.e. easier to access target in bacterium)

Answer 159

* Because it is not profitable. * The drugs that make the most money are those which are used by patients for their whole lives, such as srugs to manage arthiritis. * Antibiotics are curative, meaning that they are used only for a week or two, until the infection is cleared, so they do not make as much money.

Answer 160

* First there was the golden age of antibiotic discovery * This was followed by the void, where companies began to withdrawn from antibiotic research, since it was viewed as there already being enough and it not being profitable

Answer 161

Gram-negative

Answer 162

* In 2016, the WHO produced a list of bacterial species that were most of a threat in terms of developing antibiotic resistance. * Those in the highest category are all Gram-negative.

Answer 163

It is an acronym for the 6 common bacteria that are known to have developed a high degree of antibiotic resistance, so they posed a threat to humans, especailly those immunocompromised.

Answer 164

* The UK Government has produced a 5 year plan (2019-2024) called "Tackling antimicrobial resistance" * The plan calls for more optimal use of antibiotics in animals and agriculture, as well as improved surveillance of AMR

Answer 165

About 10 time more antibiotics are used in agriculture than medicine.

Answer 166

* It is widely believed that antibiotic resistance in animals can contribute significantly to antibiotic resistance in humans * This was contested by (Mather, 2013), when they compared *Salmonella* in humans and in local animals. They found that there was no evidence of transmission of anitbiotic resistance. * Therefore, this paper has been used a lot to support use of antibiotics by large farming companies, especially in lobbying. * However, it has been criticised a lot as a paper, since most of our food does not come from local animals, so it is not ideal to just compare humans to local animals.

Answer 167

* Beta-lactams -\> Inhibition of cell wall synthesis * Macrolides, Aminoglycosides + Chloramphenicol -\> Inhibition of protein synthesis * Sulphonamides -\> Anti-metabolites * Quinolones -\> Inhibitors of nucleic acid synthesis by binding to DNA gyrase * Isoniazid -\> Blocks long-chain mycolic acids * Rifamycins -\> Inhibition of transcription * 2,4-diaminopyridines -\> Inhibition of folate metabolism (and hence of DNA synthesis)

Answer 168

Inhibition of cell wall synthesis: * They are structural analogues of the peptide cross-bridges in peptidoglycan * Therefore, they can preferentially bind to the transpeptidase enzymes (one of the penicillin binding proteins PBPs) * This stops transpeptidation, so the peptidoglycan cannot form * They are BACTERICIDAL Examples: * Penicillins: * Penicillin * Amoxicillin * Benzylpenicillin * Flucloxacillin

Answer 169

They all have this beta-lactam ring.

Answer 170

* Penicillins: * Penicillin * Amoxicillin * Benzylpenicillin * Flucloxacillin * Cephalosporins [EXTRA - Discovered by Abraham in the Dunn school) * Monobactams [EXTRA?] * Carbapenems [EXTRA?]

Answer 171

Gram-positive

Answer 172

* Vancomycin * This works by targetting peptidoglycan directly (as opposed to its synthesis, like with beta-lactams) * It binds to D-alanine D-alanine cross-bridges * It is BACTERISTATIC and specific to Gram-positive bacteria

Answer 173

* It is an antibiotic that targets the D-alanine D-alanine cross-bridges in peptidoglycan. * Antibiotic resistance has developed by including D-lactate instead of alanine.

Answer 174

* Aminoglycosides -\> Gentamicin, Tetracyclin, Streptomycin * Macrolides -\> Erythromycin * Chloramphenicol

Answer 175

* Inhibition of protein synthesis by binding to ribosomes * They are BACTERICIDAL * Examples: * Streptomycin * Tetracyclin * Gentamicin

Answer 176

* Inhibition of protein synthesis by binding to ribosomes * They are BACTERICIDAL/BACTERIOSTATIC * Examples: * Erythromycin

Answer 177

* Inhibition of protein synthesis by inhibiting peptidyl transferase enzyme in ribosomes. * They are BACTERICIDAL/BACTERIOSTATIC

Answer 178

* They inhibit folate synthesis and therefore DNA synthesis * They are BACTERIOSTATIC (but bactericidal when combined with sulfonamides) * Examples: * Trimethoprim

Answer 179

* They inhibit folate synthesis and therefore DNA synthesis * They are BACTERIOSTATIC (but may be bacteriocidal when combined with trimethoprim)

Answer 180

* Sulphonides * Trimethoprim These are often used together.

Answer 181

* Sulphonamide -\> Dihydropteroic acid synthase (DAS) * Trimethoprim -\> Dihydrofolate reductase (DHFR)

Answer 182

* No, it is rarely used because of resistance. * However, it may be combined with trimethoprim, since they both act to reduce DNA synthesis (by blocking production of folate)

Answer 183

* They inhibit transcription * They are BACTERICIDAL or BACTERIOSTATIC * Examples: * Rifampicin

Answer 184

Treatment of tuberculosis.

Answer 185

* They inhibit DNA synthesis by inhibiting DNA gyrase * They are BACTERICIDAL or BACTERIOSTATIC * Examples: * Ciprofloxacin

Answer 186

Treatment of UTIs.

Answer 187

* An antibiotic used for treating anaerobic infections. * Intracellularly, it is converted into a toxic form after being converted by a bacterial enzyme.

Answer 188

* Blocks long-chain mycolic acids (unique to Mycobacteria) * Bactericidal to growing organisms, otherwise bacteriostatic

Answer 189

The derivatives can have a different spectra of activity, bioavailability, and adverse effects.

Answer 190

* Empiric therapy when pathogen is unknown * Synergistic action (cell wall/protein synthesis) * Combining ‐cidal with ‐static in general * Reduce emergence of resistance

Answer 191

* Combination antibiotic therapy is believed to be effective in critical patients, since there is a greater likelihood that the pathogen is susceptible to at least one of the antibiotics, although there is some disagreement about whether the combination of drugs significantly increases their effect due to synergistic actions and whether the combination directly decreases the likelihood of resistance developing as a consequence of cumulative action. * Therefore, it is argued that once a bacterium has been isolated and the degree of drug-resistance experimentally deduced, there is rarely substantial advantage to use of more than one drug that the bacterium is susceptible to. (Tamma, 2012) * This can prevent development of resistance.

Answer 192

* Before the identity of the pathogen is known, many antibiotics are used. They are likely to be broad-spectrum antibiotics. * After the pathogen is identified, just one specific antibiotic is used, to prevent the development of resistance.

Answer 193

The minimum concentration of an antibiotic that must be maintained throughout treatment, in order to ensure that the drug is effective.

Answer 194

* Drug resistance * Elimination of normal microbiota

Answer 195

When multiple applied antibiotics work together to produce an effect more potent than if each antibiotic were applied singly.

Answer 196

When one antibiotic inhibits the use of another, so that they should not be used in combination.

Answer 197

* Decreased uptake * Efflux * Drug inactivation * Target modification * Target amplification

Answer 198

* The cell wall can become more impermeable by changes to the structure and transporters * Mutations in porins in Gram-negative bacteria

Answer 199

* There can be membrane pumps * e.g. Tetracycline can be exported by membrane pumps

Answer 200

Systems made of active transporters that export a wide a variety of substrates from cells and consequently are capable of conferring resistance to a wide range of chemotherapeutic agents.

Answer 201

* There can be production of enzymes to break down the antibiotic * Examples: * Beta-lactamases in penicillin resistance * Phosphotransferases in aminoglycoside resistance

Answer 202

* It can occur due to mutations in the targets for the antibiotic * Examples: * DNA gyrase mutations -\> Prevent quinolones binding * Penicillin binding proteins (transpeptidases) mutations -\> Prevent beta-lactam binding (but can still bind to peptidoglycan)

Answer 203

* The Mec genetic element encodes a different PBP (penicillin binding protein) * This means that the target for penicillins is altered in structure

Answer 204

* The bacteria can express lots of copies of the target for the antibiotic, so that the competitive inhibition of the antibiotic is overcome * e.g. Sulphonamide resistance can be caused by production of lots of the enzyme that sulphonamides inhibit

Answer 205

A mobile DNA element in a bacterium that can capture and carry genes, particularly those responsible for antibiotic resistance.

Answer 206

Integrons have: * An integrase that enables the addition of new DNA to the integron * A promoter that enables expression of the DNA * A recombination site (and a recombination site on the new incoming casette), so that the new DNA can be added to the integron This means that a plasmid can contain multiple resistance genes that the bacterium 'collects'. These can collectively be passed on using the plasmid.

Answer 207

It is really the plasmids, because they are where the antibiotic resistance genes tend to be found.

Answer 208

* Circular, extrachromosomal DNA found in bacteria * Transferable between strains * There are many copies * Move by transformation or conjugation

Answer 209

* Groups of bacteria can form large colonies * These can produce biofilm, which can protect the bacteria from antibiotics

Answer 210

* Dental biofilms * Pneumonia in CF patients * Endocarditis, osteomyelitis * Artificial surfaces: * Catheter‐related infections * Contact lens infections * Prosthetic joints They are difficult to eradicate due to antibiotic resistance and resistance to phagocytosis.

Answer 211

* Avoid unnecessary antibiotics * Know local sensitivities * Narrow spectrum vs. broad spectrum rapid diagnostics -\> So that the change from broad spectrum to narrow spectrum drugs is done at the right time and ASAP * Directly observed therapy (DOTS) * Drug combinations * Antibiotic policies * Develop new drugs

Answer 212

Gram positive: * Streptococcus pneumoniae * Streptococcus pyogenes * Staphylococcus aureus (including MRSA) * Clostridium difficile * Clostridium tetani Gram negative (O-antigen possessing): * Escherichia coli * Shigella * Salmonella Gram negative (Non-O-antigen possessing): * Neisseria gonorrhoeae * Neisseria meningitides Mycobacteria: * Mycobacterium tuberculosis

Answer 213

* Gram positive * Causes: Primary lobular pneumonia

Answer 214

* Gram positive * Causes: * Pharyngitis (sore throat) * Cellulitis (skin infection) * Rheumatic fever * Glomerulonephritis (glomerulus injury) * Features: * CO₂ may regulate the expression of virulence determinants

Answer 215

* Gram positive * Causes: * Abcesses (a form of skin infection) * Surgical wound and burn infections * Food poisoning * Features: * Examples of adhesins, aggressins (e.g. toxins) and antibiotic resistance genes carried by mobile genetic elements (in Staphs & Streps).

Answer 216

Streptococcus pyogenes

Answer 217

Penicillins, such as methicillin.

Answer 218

* Gram positive * Causes: * Clostridium difficile -\> Watery diarrhea * Clostridium tetani -\> Tetanus * Features: * Anaerobic * Spore forming

Answer 219

* Gram negative (O-antigen-possessing) * Causes: * Travellers' diarrhoea * Dysentery (intestinal inflammation and cramps) * Food poisoning * Fever

Answer 220

* Gram negative (O-antigen-possessing) * Causes: * Travellers' diarrhoea * Dysentery (intestinal inflammation and cramps) * Food poisoning * Fever

Answer 221

* Gram negative (O-antigen-possessing) * Causes: * Travellers' diarrhoea * Dysentery (intestinal inflammation and cramps) * Food poisoning * Typhoid fever

Answer 222

* Gram negative (Non-O-antigen-possessing) * Causes: * Gonorrhoea * Features: * There are differences between men and women in terms of asymptomatic carriage * Main steps of infection and transmission cycle, key interactions, importance of sialylation and capsule for evasion (ADD FLASHCARDS)

Answer 223

* Gram negative (Non-O-antigen-possessing) * Causes: * Meningitis * Features: * Main steps of infection and transmission cycle, key interactions, importance of sialylation and capsule for evasion (ADD FLASHCARDS)

Answer 224

Women are much more likely to carry asymptomatic infection.

Answer 225

* Gram staining * Cellular morphology and colony morphology * Catalase * Coagulase * Oxidase * Streptococcal carbohydrate antigen grouping (Lancefield typing)

Answer 226

Media containing bile acids are helpful for identifying bacteria that survive in the small intestine, a feature of many Enterobacteriaceae.

Answer 227

* A medium used to differentiate between Gram-negative bacteria based on their ability to digest lactose. * It contains a pH indicator and lactose. * If the bacteria can digest carbohydrates, acid is produced and the result is pink colonies. * If the bacteria cannot digest carbohydrates, acid is not produced and the result is colourless colonies.

Answer 228

The bacteria can digest carbohydrates, so acid is produced and the result is pink colonies.

Answer 229

The bacteria cannot digest carbohydrates, acid is not produced and the result is colourless colonies.

Answer 230

* Bile salts * This is because MacConkey is useful for distinguishing between Gram-negative bacteria that can grow in the intestine, so bile salts are used to kill any Gram-positive bacteria and those not adapted to living in the intestines

Answer 231

* A test for the presence of a bacterial enzyme that breaks down hydrogen peroxide. * A drop of hydrogen peroxide is applied to a bacterial colony using a glass capillary tube. A positive result is the appearance of bubbles on the surface of the colony. * The ability of bacteria to degrade hydrogen peroxide can directly impact where they can live and the types of infection they cause.

Answer 232

It is where a blood agar is used to test the haemolytic properties of an unknown bacterium.

Answer 233

* It is a.k.a. Streptococcal carbohydrate antigen grouping * It is used to differentiate between the different Streptococcus species, which each show different carbohydrate antigens. * It is an agglutination assay. The latex particles coated with specific antibodies will only agglutinate in the presence of the homologous antigen, and will remain in suspension otherwise. * The results as stated as Group A, Group B, etc.

Answer 234

A test that detects cytochrome oxidase, a transmembrane protein complex of the respiratory electron transport chain, which is present in aerobic organisms that can use oxygen as a terminal electron acceptor.

Answer 235

* It is a test for the urease enzyme * It is used to test for bacteria such as H. pylori * Urease can split urea to generate ammonia and CO2, leading to a rise in pH. The test includes a pH indicator, typically phenol red, which turns red when the pH rises above 8.

Answer 236

* It is a test for the coagulase enzyme * It is used to differentiate between Staphylococcus aureus and a coagulase-negative Staphylococcus * A positive Coagulase test is detected by aggregation/clumping of the latex particles.

Answer 237

* Xylose, Lysine, Deoxycholate * It is used to differentiate between Salmonella and Shigella. * XLD plates contain deoxycholate which is a bile salt, making them selective for Gram-negative bacteria that can grow in the intestine. * XLD also contains a pH indicator (phenol red). Acidification results in yellow colouration, while alkalisation results in pink to red coloration. * Xylose, sucrose and lactose in XLD help differentiate Salmonella and Shigella. As Shigella cannot ferment these carbohydrates, its colonies are red on XLD. * Salmonella can ferment xylose which would result in yellow colonies through acidification. However, Salmonella also metabolises lysine (due to its lysine decarboxylase) which produces cadaverine, raising the pH so Salmonella and Shigella colonies are both red on XLD. * Therefore, the media also contains sodium thiosulphate and ferric ammonium citrate. Salmonella can convert sodium thiosulphate to H₂S. This reduces the ferric ammonium citrate to iron sulphide which has a black colour. Hence, Salmonella form red colonies with black centres.

Answer 238

They do not produce lysine decarboxylase, which the Salmonella use to produce an adequately alkaline environment for H₂S production.

Answer 239

* Gram-positive * Coccus * Negative catalase * Alpha haemolysis + Optochin sensitive -\> Streptococcus pneumoniae * Beta haemolysis + Lancefield type A -\> Streptococcus pyogenes

Answer 240

* Gram-positive * Coccus * Positive catalase * Positive coagulase

Answer 241

* Gram-positive * Bacillus

Answer 242

* Gram-negative * Bacillus * Growth in bile salts * Positive lactose fermentation (MacConkey) * Positive indole test

Answer 243

* Gram-negative * Bacillus * Growth in bile salts * No lactose fermentation (MacConkey) * Negative oxidase test * Negative urease test * No H₂S production

Answer 244

* Gram-negative * Bacillus * Growth in bile salts * No lactose fermentation (MacConkey) * Negative oxidase test * Negative urease test * Positive H₂S production

Answer 245

* Gram-negative * Coccus * Positive oxidase test

Answer 246

HIV -\> There is an increased incidence in HIV patients.

Answer 247

Extensively drug-resistant TB (XDR TB) is a rare type of multidrug-resistant tuberculosis that is a potential danger.

Answer 248

* The total global incidence is decreasing * But co-infection with HIV is increasing and the proportion of cases of XDR TB (Extensively drug-resistant TB) are increasing * This is partly due to collapsing medical systems in the Soviet bloc contributing to the development of XDR TB

Answer 249

Respiratory droplets

Answer 250

* Infection starts in lungs * May also spread to anywhere in body (15% cases): * Central nervous system * Lymphatic system * Genitourinary systems * Bones and joints * Disseminated (miliary TB)

Answer 251

* General symptoms -\> Fever, weight loss, weakness, cachexia * Symtoms of lung infection -\> Cough, chest pain * Symtoms of extra-pulmonary infection -\> Affecting CNS, lymphatic system, genitourinary system, bones and joints

Answer 252

* In all cases, there is a **primary infection** before adaptive immunity kicks in. * After immunity develops, in most cases the bacterial load drops and there is a chronic infection. In around 5% of cases, the adaptive immunity is not sufficient, so there is **primary disease**. * Of those with chronic infection, there are few symptoms, but there is the possibility of reactivation, which leads to **post-primary disease**.

Answer 253

* During primary disease * During post-primary disease

Answer 254

* The mid-zone of the lung. * It forms a small area of granulomatous inflammation, known as a **Ghon focus**. * It can then spread to a regional lymph node.

Answer 255

It is the Ghon focus together with the infected regional lymph node, which are infected in a primary infection of tuberculosis.

Answer 256

It is a Ghon complex seen in tuberculosis primary infection, made up of: 1. Ghon focus 2. Infected regional lymph node

Answer 257

* If the infection is not kept in check, the bacterium can spread from the Ghon focus, or via the bloodstream and through the lungs. * The pleural space, entire airways, retina, CNS and other organs may be affected.

Answer 258

* It is a tuberculosis infection, shown by the infected lymph node. * There is fluid in the pleural cavity, showing that there has been progression to primary disease.

Answer 259

It can lead to deposits on the retina.

Answer 260

* In the CNS, it can lead to meningitis, which is inflammation of the meninges * It can also lead to hydrocephalus This is dangerous because the CSF is a sterile environment usually.

Answer 261

Cavitary lung disease, mostly in the upper lobes of the lungs.

Answer 262

* Age * Malnutrition * HIV * α‐TNF * Steroid therapy

Answer 263

* Cannot be gram stained (sometimes considered Gram positive though) * Causes tuberculosis * Features: * Slow growth * Mycolic acid cell wall * Few surface targets * Resistance to phagolysosomal killing * Macrophage subversion * Primary infection: Ghon focus formation, granuloma formation * Reactivation * Role of T cells in control of replication of tubercle bacillus

Answer 264

Branched rods

Answer 265

4-6 weeks (it is slow-growing)

Answer 266

* Human specific -\> So it is difficult to study in animal models * Slow growing * Difficult to perform molecular genetics * Chronic infection -\> Difficult to study

Answer 267

No, because the mycolic acid in the cell wall does not allow absorption of the stain.

Answer 268

Ziehl-Neelsen stain: * Stain with carbol fuchsin (pink) * Attempt to destain with acid and alcohol mixture -\> Mycobacteria are acid-fast and alcohol-fast, so they should not destain * Counterstain using methylene blue

Answer 269

* Lipoarabinommannan -\> Two sugars attached to a lipid * Mycolic acids -\> Negatively-charged * Glycolipids -\> Associate with the mycolic acids

Answer 270

* Mycobacteria have chromosomal toxin-antitoxin systems (TA) systems that produce a toxin that is harmful to the bacterium, as well as an antitoxin that protects against the toxin * These TA systems are usually found on plasmids, so that when the bacterium loses its plasmid, the toxin out-survives the antitoxin and causes the cell to die -\> Used for plasma maintenance * However, mycobacteria have a TA system on their chromosomes, which may contribute to their slow growth (even if both the toxin and antitoxin are present)

Answer 271

The antitoxins in the bacterium can be targeted, so that the toxins are uncontrolled and lead to bacterial cell suicide.

Answer 272

Granuloma (a.k.a. Ghon focus)

Answer 273

* Macrophages in the lungs (attempt to) phagocytose the Mycobacterium tuberculosis (Mtb) -\> TLR2 recognition of Mtb leads to Myd-88 controlled secretion of TNF-α * This leads to recruitment of circulating monocytes, which differentiate into tissue macrophages * There is then increased vascularity to the area due to VEGF (vascular endothelial growth factor) * (Foamy) Macrophages and helper T cells surround the bacterial cells -\> Helper T cells secrete IFN-γ * A fibrous cuff also forms around the bacterial cells, reducing vascularisation of the bacterial cells -\> This leads to hypoxia that causes the bacteria to become dormant * Langhans multinucleated giant cells appear -\> Due to the joining of macrophages * Eventually, in the centre of the granuloma, caesum appears, which is necrotic material

Answer 274

* Macrophages * Monocytes (which differentiate into tissue macrophages) * Helper T cells * Langhans multinucleated giant cells appear

Answer 275

* Macrophages in the lungs (attempt to) phagocytose the Mycobacterium tuberculosis (Mtb) * TLR2 recognition of Mtb leads to Myd-88 controlled secretion of TNF-α * This leads to recruitment of circulating monocytes, which differentiate into tissue macrophages and begin granuloma formation

Answer 276

The bacterium are trapped in a granuloma, with reduced vascularisation. This means the area is hypoxic, which reduces bacterial replication and causes the bacteria to become dormant.

Answer 277

* Langhans giant cell (Note the spelling) * It is seen in tuberculosis infections -\> Due to the fusion of macrophages, driven by IFN-γ

Answer 278

* They do not have a phagocytic role, so they appear to reduce killing of bacteria * Couldn't find any function online [CHECK]

Answer 279

* They are macrophages that contain lipid bodies * These are formed when Mycobacterium tuberculosis prevents the cell from pumping out LDL cholesterol * The bacteria make use of this LDL cholesterol

Answer 280

It is derived from LDL and most likely released from foamy macrophages.

Answer 281

Macrophages

Answer 282

There are many phagocytic receptors that allow the bacterium to be taken up in phagocytes by phagocytosis.

Answer 283

* TLR2 -\> This is activated by lipoproteins and glycolipids * There is lots of redundancy in the co-receptors, including TLR1

Answer 284

* Prevents acidification of the phagosome at an early stage: * The mechanism for how it does this is poorly understood. * Lipoarabinomannan (LAM) is thought to play a part in this, but dead Mycobacterium tuberculosis cannot fully inhibit phagosome maturation, so there must also be something about the live bacterium. * Can resist antimicrobial stresses: * Enters cell via CR3, which avoids stimulating the oxidative burst * Detoxifies reactive oxygen species by producing superoxide dismutase and catalase * Has heat shock proteins Hsp70 and Hsp60 to refold damaged proteins and uses the proteasome to degrade damaged proteins. * Has DNA repair systems.

Answer 285

* Latex beads coated with lipoarabinomannam (LAM) are phagocytosed but the phagosome does not mature. * Thus, LAM is likely to play a large role in preventing phagocytosis by preventing phagosome maturation.

Answer 286

* Superoxide dismutase * Catalase

Answer 287

* Mostly in a partially acidified, immature phagosome * But there is also some evidence that it might enter the cytosol using an Esat-6 secretion system (type 7 secretion system)

Answer 288

It happens when the immune system is compromised: * Age * Malnutrition * HIV * Steroid therapy This tells us about the importance of CD4+ T cells, TNF signalling and macrophage function in containing the disease. (since if they are removed, the disease increases).

Answer 289

* CD4+ T cells * This explains why HIV patients are at an increased risk of reactivation of latent tuberculosis

Answer 290

Tissue damage is due to increased inflammatory signalling

Answer 291

* Bacille Calmette-Guerin (BCG) -\> Live attenuated bovine tuberculosis bacterium (Mycobacterium bovis) * This bacterium lost its virulence towards human hosts by growth in special culture medium, Middlebrook 7H9 * Efficiency of vaccination is variable (0-80%). * Very efficient against tuberculous meningitis in children, but not so efficient against pulmonary tuberculosis. Not effective in adults.

Answer 292

* Treatment is long (over 6 months) due to chronic infection * Multiple drugs are used (4 drugs initially) to combat the emergence of drug resistance

Answer 293

* A transposable element is a DNA sequence that can change its position within a genome, sometimes creating or reversing mutations and altering the cell's genetic identity and genome size. * Transposition often results in duplication of the same genetic material.

Answer 294

* Pasteurization * Autoclaving * Hypochlorite * Halogenated phenols * Gamma-irradiation

Answer 295

* Debridement is a procedure for treating a wound in the skin. It involves thoroughly cleaning the wound and removing all hyperkeratotic (thickened skin or callus), infected, and nonviable (necrotic or dead) tissue, foreign debris, and residual material from dressings. * It may be used in e.g. necrotizing fasciitis

Answer 296

Septicemia is a clinically significant form of bacteremia complicated by toxemia, fever, malaise, and often shock.

Answer 297

* The toxin acts by modifying host cell GTPase proteins by glucosylation, leading to changes in cellular activities. * This involves actin condensation and cell rounding, which is followed by death of the cell

Answer 298

* EHEC -\> Enterohemorrhagic E. coli * EPEC -\> Enteropathogenic E. coli

Answer 299

* Enterohemorrhagic E. coli (EHEC) causes severe intestinal infection and bloody/non-bloody diarrhoea. * It’s different from other E. coli because it produces a potent toxin called Shiga toxin. * This toxin damages the lining of the intestinal wall, causing bloody diarrhea. * The Shiga toxin acts to block protein synthesis in the host cell.

Answer 300

Enteropathogenic E. coli (EPEC) is the causative agent of watery diarrhoea.

Answer 301

Sialylation and the capsule are important.

33. Bacteriology Flashcards

(335 cards)