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3s2: Infection and Immunity > Week 7 > Flashcards

Week 7 Flashcards

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1
Q

How do we view bacteria?

A

Brightfield - produces image on bright background (commonly used)
Darkfield - produces bright image on dark background no staining and use for live specimens
Phase contract - Refraction and interference caused by structutes in the specimen to create high resolution images without staining. Useful for live organisms and organelles
Differential interference contrast - Interference pattersn to enhance contrast between different features of a specimen to produce high contrat images of living organism with a 3d appearance

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2
Q

What examples of morphologies to classify bacteria?

A

Coccus - round
Bacillus - rod
Vibrio - Curved rod
Spirilliom - spiral

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3
Q

What examples of cell arangements to classify bacteria?

A

Coccus - single coccus
Diplo - pair of
Tetra - grouping of 4
Strepto - Chain of

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4
Q

What is a contrasting use of shape as a name?

A

Two rod-shaped (bacillus) bacteria:
Bacillus subtilis
Escherichia coli

Two spherical (coccoid) bacteria:
Streptococcus agalactiae
Neisseria gonorrhoeae

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5
Q

What is an overview of gram staining?

A

In 1884, Hans Cristian Gram first differentiated between two pathogens by testing different chemical stains
Crystal violet was retained by one, but not the other
Final step: Counterstaining added by Carl Weigert

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6
Q

What is an overview of gram staining method?

A

Step 1 - Crystal violet stains cell purple
Step 2 - Iodine makes dye less soluble so adheres to cell walls
Step 3 - Alcohol decolourises by washing stain away from gram-negative cell walls
Step 4 - Safranin counterstain allows dye to adhere to gram-negative cells

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7
Q

What is an overview of gram postive cell wall?

A

Gram-positive bacteria cell membrane are surrounded by many layers of peptidoglycan, which form a protective shell that is 30–100 nm thick.
The peptidoglycan layer are covalently modified with carbohydrate polymers including wall teichoic acids (WTAs) or functionally related anionic glycopolymers

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8
Q

What is an overview of gram negative cell wall?

A

A thin peptidoglycan layer is present (this is much thicker in gram-positive bacteria)
An outer membrane containing lipopolysaccharides (LPS, lipid A, core polysaccharide, and O antigen) in its outer leaflet and phospholipids in the inner leaflet

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9
Q

What is the difference between peptido-glycan cell wall between negative and positve cell wall?

A

Bacterial cell wall - Peptido-glycan (protein)-(sugar)
Gram-positive - stronger and thicker, pentapeptide intermediate links between tetrapeptides
Gram-negative - thinner and covered by outer membrane direct link between tetrapeptides so between NAGs and NAMs layers

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10
Q

What is an overview of the ways to distinguish bacterial isolates?

A

Gram-staining
Biochemical assays E.g. coagulase, hemolysis
Colony morphology
Sequence typing
Serological typing
Antimicrobial resistance (AMR) phenotypes

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11
Q

What is a description of the gram negative cell wall layers?

A

Inner membrane
Periplasmic space
Outermembrane with LPS and Porins (exchanging)

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12
Q

What are the main gram-negative burdening bacterial infections?

A

Escherichia Coli - ~950,000 deaths
Klebsiella pneumoniae - ~790,000 deaths
Pseudomonas aeruginosa - ~559,000 deaths
Acinetobacter baumanii - ~452,000 deaths

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13
Q

What is an overview of Escherichia Coli?

A

Gram negative enteric, motile, rod-shaped, coliform bacterium
Order: Enterobacterales
Family: Enterobacteriaceae
Two categories: Diarrhoeagenic / Extraintestinal E. coli
Commonly found: gastro-intestinal tract, lower intestine, urinary tract, surface-contamination with faecal material

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14
Q

What are the six distinct ‘pathovars’ of Escherichia coli?

A

Shiga-toxin producing Escherichia coli (STEC)
Enteropathogenic Escherichia coli (EPEC)
Enterohaemorrhagic Escherichia coli (EHEC)
Enterotoxigenic Escherichia coli (ETEC)
Enteroinvasive Escherichia coli (EIEC)
Enteroaggregative Escherichia coli (EAEC)

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15
Q

What are two extraintestinal pathogenic Escherichia coli?

A

Uropathogenic Escherichia coli (UPEC)
Neonatal meningitis Eschericia coli (NMEC)

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16
Q

How does attachment and invasion occur in Enteroaggregative Escherichia coli (EAEC)?

A

Forms biofilm on the surface of epithelial cells
Then secrete cytotoxins and enterotoxins, inclusing ShET1, Pic and PET

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17
Q

How does attachment and invasion occur in Enteropathogenic Escherichia coli (EPEC)?

A

Forms microcolony amogst the microvili of epithelial cell
Induces cell then forms a actin filiments as a pedistal for E.coli to live on where they can be internalised an cause damage through toxins, which causes diarrhea

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18
Q

What structures to Escherichia coli have to attach to cells

A

Fimbriae or pili - 5- 7 nm diameter
Curli - 2-5 nm diameter

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19
Q

What is an overview of the secretion systems in Escherichia coli?

A

Type 1 - Secretes Small molecules or antibiotics into environment
Type 2 - Secretes proteins into environment
Type 3 - Injects virulence effectors into host cell

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20
Q

How can E.coli get into gut eptithelial cell?

A

It can transcytose across M cell
It will be phagocytosed eg by macrophage
It can escape and live in cytoplasm where it can produce IPAB a proapoptopic molecule
Then penetrates epithelial cell and causes problems with virulence factors lie acrtin polymerisation

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21
Q

How does Uropathogenic Escherichia coli (UPEC) cause a reoccurant infection?

A

Uses pili which are recognised by bladder epithelial cells allowing entry
They reduce metabolic rate becoming dormany intracellular bacteria community, which are resisitant to antibiotics, and reescape causing new infection

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22
Q

How can Uropathogenic Escherichia coli (UPEC) make symptoms worse?

A

Shedding of epithelial cells with cystitis and inflammation
Attract polumorphic nuclear lymphocytes which in immune response damage more cells

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23
Q

What is an overview of LPS for immunity?

A

LPS (Lipopolysaccharide) and induces cytokine expression through TLR4
>180 types

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24
Q

What is an overview of flagellin for immunity?

A

Motility, induces cytokine expression through TLR5
>50 flagella subtypes

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25
How do LPS and flagellin trigger severe immunity?
NFkB activation pro-inflammatory cytokines TNF-a Interleukin-1 (IL-1), IL-6, IL-8 Type-1 Interferon (IFN) responses Hyper-inflammation leads to septic shock
26
What is an overview of Extraintestinal Escherichia coli?
Urinary tract infections (UTI) are one of the most common of all infectious diseases 50% of women, 10% of men will have an UTI in their lifetime 85-95% of all urinary tract infections are due to E. coli
27
What are the Stages of ascending UTI, Escherichia coli?
Bladder infection (cystitis) --(Mobilisation via ureters)--> Kidney infection (pyelonephritis) --(Access to blood supply)--> Bloodstream (bacteraemia)--(Spread to vital organs)--> Invasive disease (sepsis, meningitis)
27
What is an overview of Sequence-type 131 (ST131) E. coli?
Emerged in late 2008, globally disseminated, multidrug resistant (MDR) pathogen The predominant strain of MDR E. coli in adults / children. Extended-spectrum beta-lactamase (ESBL), resistant to most front-line antibiotics
28
What are the main causes of Escherichia coli deaths?
Mostly, bloodstream and intra-abdominal
29
What is an overview of Klbsiella pneumoniae?
Named after Edward Klebs, discovered bacteria were the cause of lung infections in late 1800s Gram negative, non-motile, rod-shaped, encapsulated bacterium Order: Enterobacterales Family: Enterobacteriaceae
30
What is an overview of Klebsiella pneumoniae infection?
Aspiration pneumonia – breathing in contaminated material Infection associated with alcohol addiction Sputum appearance of currant jelly
31
What is an overview of Klebsiella pneumoniae growth?
Lives in a wide range of environments, grows aerobically or anaerobically Coloniser of mouth, nasopharynx, gastrointestinal tract Common nosocomial pathogen, opportunistic Readily exchanges DNA with other bacteria
32
What are the two phenotypes of Klebsiella pneumoniae?
Classical Kp known to cause pneumonia and bladder infection Hypervirulent Kp (hvKp) - soft tissue, liver and meningtitis
33
What is an overview of classical Klebsiella pneumoniae?
Multi-drug resistant Encaplulated Vulnerable to phagocytosis and opsonisation
34
What is an overview of hypervirulent Klebsiella pneumoniae?
Overproduces capsule Inhibits phagocytosis and bacterial lysis Membrane attack compelx cant breach outer membrane Not typicaly asscociated with drug resistance
35
What is a problem with Klebsiella pneumoniae drug resistance?
Klebsiella pneumoniae is a key trafficker of drug resistance genes from environmental to clinically important bacteria Occurs in all hosts
36
Why are Escherichia coli and Klebsiella pneumoniae considered an urgent threat?
Resistance to pencillins and cephalosporins Emergence of carbapenem antibiotics (last-line of defence) Also potential in the hypervirulent strains
37
What countries are most effected by Klebsiella pneumoniae?
China (most), Singapore, USA, UK and France
38
What is the cause of most Klebsiella pneumoniae deaths?
Mostly, Pneumonia, bloodstream and intra-dominal
39
What is an overview of Pseudomonas aeruginosa?
Pseudomonas = ‘false germ’ ; aeruginosa = latin for ‘copper rust’ Gram negative, rod-shaped, facultative anerobic, encapsulated bacterium Order: Pseudomonadales Family: Pseudomonadaceae Characteristic green colouration due to synthesis of pigments pyocyanin and pyoverdine
40
What is an overview of Pseudomonas aeruginosa infections?
Pseudomonas aeruginosa is the predominant cause of death and morbidity in Cystic Fibrosis patients Associated with hospital-acquired infection in patients using ventilators Virulence factors include flagellum and Lipopolysaccharide which are immuno-stimulatory
41
What is a problem with clearing Pseudomonas aeruginosa?
Biofilm formation is a major problem for Pseudomonas aeruginosa control Sesile cells which resist external stresses and can then regrow and disperse
42
Why is Pseudomonas aeruginosa hard to control long term?
Highly adaptable pathogen; can undergo hyper-mutation at a rate 1,000 times higher than ‘normal’
43
How can Pseudomonas aeruginosa resist immunity and antibiotics?
Loss of immunogenic structure such as flagella Produce toxins to inhibit immune cells Prevention of LPS forming Mutant antibiotic targets such as gyrase Low membrane permeability
44
How can Pseudomonas aeruginosa survive antibiotics?
Can enter a ’persister’ lifestyle to survive antibiotic treatment
45
What is an overview of the persister lifestyle?
Remain dormant when exposed to antibiotics to wait it out Or they can upregulate antibiotic reistance molecules
46
What is an overview of Pseudomonas aeruginosa antibiotic resistance?
~60% of strains resistance across different penicillins ~42% of strains resistant to carbapenems
47
What are the main causes of Pseudomonas aeruginosa deaths?
Heavily pneumonia (cycstic fibrosis link) and blood stream
48
What is an overview of Acinetobacter baumannii?
Gram negative, short-rod shaped (coccobacillus) bacterium Family: Moraxellaceae Genus: Acinetobacter Found almost exclusively in hospitals Sometimes referred to as Carbapenem-resistant Acinetobacter baumannii (CRAB)
49
How do people get infected with Acinetobacter baumannii?
Ventilators Central-line catheters (vein) Surgery Catheter-UTI
50
How can Acinetobacter baumannii survive decontamination well?
Survives well on surfaces Extreme resistance to desiccation (removal of water) (up to 100 days) Resists disinfectants including hydrogen peroxide, chlorhexidine (hospital-grade antiseptic)
51
What groups are most at risk from Acinetobacter baumannii?
Critically-ill patients Immunocompromised
52
How prevalent are Acinetobacter baumannii infections?
2-4% of all hospital acquired infections due to A. baumannii Globally, 45% of all isolates are multidrug-resistant, up to 70% in some areas
53
Where does Acinetobacter baumannii colonised?
Primarily the respiratory tract Though can invade and infect the bloodstream
54
How can Acinetobacter baumannii resist antibiotics and which mechansim goes to which antibiotic?
Reduction of memebrane permiabilty - betalactams Antimicrobial expulsion - Beta-lactams, rifamycins and tetracyclins Enzymatic modifications - Tetracyclines, Beta-lactams an rifamycins Target site alterations - Tetracylines
55
What is a key different to Acinetobacter baumannii cell surface?
Has a Lipooligosaccharide (LOS) rather than a Lipopolysaccharide (LPS) LOS is truncated LPS, lacks the O antigen
56
What is an overview of innate immune response to Acinetobacter?
Similar to E.coli with TLR4 recognition Upregulation of NG-kamma beta which increase inflamatory cytokines such as TNF, IL-6 and IL-8 which increase immune response
57
What is the relationship between Acinetobacter baumannii and rare metal ions?
Availability of metal ions is central to antimicrobial action of innate immune cells Neutrophils produce and export calprotectin which then bind and prevent infections from getting rare metal ions such as zinc and nickel But Acinetobacter baumannii can produce enzymes to scavenge these metals at a higher affinity Also Acinetibactin a siderophore
58
What is metal intoxication?
After phagocytosis, immune cells like macrophages over concentrate these metals as they are reactive therefore toxic which kill bacteria cell Though Acinetobacter baumannii can overcome this by expelling the metals
59
Why is Acinetobacter baumannii an urget level threat?
Hospital-acquired infections Urgent level threat to antimicrobial resistance 70% of Acinetobacter baumannii cases were people already in hosptial 17% mortality rate
60
What are the main infection types of Acinetobacter baumannii?
30% Pneumonia 20% Pressure ulcer 12% UTI
61
What is an overview of Zosurabalpin (ZAB)
Targets and blocks synthesis of LPS/LOS Not as effective against E.coli or Staphylococcus aureus but effective against Acinetobacter baumannii
62
What is an overview of Enterobacter?
Gram negative, facultatively anaerobic, rod shaped Family: Enterobacteriaceae Genus: Enterobacter 22 species of Enterobacter make up this group such as E. amnigenus, E. arachidis, E. asburiae, E. bugandensis Associated with hospital (nosocomial) infections in susceptible patients
63
What is an overview of Enterobacter taxonomy?
Similar taxonomy (relatedness) to other Enterobacteria such as E. coli and Klebsiella pneumoniae
64
What is an overview of Enterbacter virulence?
Little is known about pathogenicity or virulence factors in Enterobacter spp due to lack of study Flagella, endotoxins (Lipopolysaccharides), hemolysins, type-3 secretion systems all reported Biofilm formation
65
What is an overview of Enterobacter spp antibiotic resistance?
Often called XDR (Extensively drug-resistant) Resistant to Carbapenem, Penicillin and Cephalosporins
66
What is an overview of Salmonella?
Named after Daniel Salmon, discovered bacterium from pig intestine 1880’s Gram negative enteric, motile, rod-shaped, intracellular bacterium Family: Enterobacteriaceae Genus: Salmonella
67
What are the broad categories of salmonella?
Typhoidal, non-Typhoidal Salmonella Pathogen of humans and animals Food-borne illness, systemic infection, gastroenteritis
68
What are the two species of Salmonella?
S. bongori - infects lizards, not normally in humans except young children S. enterica - divided into Salmonella Typhi (typhoid fever) or Salmonella Typhimurium (Non-typhodial salmonella)
69
What is a major symptom of salmonella?
Enteritis in humans Diarrhoea, fever, abdominal (12 - 72h after infection) Lasts 4-7 days. Generally self-limiting
70
What is an overview of salmonella epidemiology?
Second most common food poisoning pathogen - but most deadly!!! 41, 616 cases, 120 deaths/year in UK. Salmonella isolated from 23% GB pigs at abattoir.
71
How much does Salmonella Typhimurium cost NHS?
National cost estimated at £500 million p.a.
72
How does Salmonella Typhimurium spread?
Pathogen distribution through global food distribution and international travel
73
How was Salmonella Typhimurium controlled in UK?
Lion Quality code 1998 Compulsory vaccination Best-before date stamped on eggs On farm and packaging hygiene controls
74
What is an overview of Defra abattoir survey of Salmonella in UK Salmonellaresoviors?
23% Pigs 5% Chickens 1% Cows Salmonellosis increasingly linked to vegetables
75
What is an overview of Salmonella Typhimurium infection?
Ingest > 105 bacteria Bacteria invade mucosal cells Na+ uptake inhibited Cl- secretion increased Loss of water by mucosal cells Increase cAMP levels in mucosal cells
76
What is an overview of the immune response to Salmonella Typhimurium?
Inflammatory response to bacteria in underlying tissue Prostaglandin release by PMNs
77
What is an overview of Salmonella Typhimurium infection?
Salmonella adheres to gut epithelium (Lamina Propria) Salmonella invades epithelial cells Host senses infection (LPS as signal?) Recruits phagocytes Salmonella survives & multiplies inside vacuole (flagellin as signal) Induction of pro-inflammatory response (NF-kB)
78
How does inflammation worsen Salmonella Typhimurium infection?
Inflammation of gut mucosa Epithelial cells undergo necrosis & detach Inflammation accelerates & damages lamina propria Fluid is released into gut lumen causing acute diarrhoea
79
How does Salmonella Typhimurium infect cells?
Uses T3SS1 to invade epithelia Uses a second T3SS2 to generate SCVs (Salmonella-containing vacuole)
80
What is the function of SCVs?
Avoids innate immune defenses Recruits inflammatory cells Depletes resident microbiota via the previous recruitment Colonises the lumen, expands via colonal expansion
81
What is an overview of Salmonella Typhi disease?
Typhoid fever in humans – host restricted. Oral infection - systemic spread to organs. 9 million cases/ year worldwide 110 000 deaths worldwide (2019) Endemic in sub-Saharan Africa, Far East.
82
What is an overview of Salmonella Typhi vaccines?
Single serotype: 2 conjugate vaccines available.
83
Where is Salmonella Typhi most prolific?
India, Pakistan, Southeast Asia and subSaharen Africa
84
What is an overview of Salmonelaa Typhic infection?
Exclusive human pathogen Gram negative flagellated bacilli Non-sporulating facultative anaerobe Ferments glucose without producing gas Reduces nitrate to nitrite Synthesizes peritrichous flagella when motile
85
Where can Salmonella Typhi infect and associated symptoms?
Neurology - Seizures Respiratory - Dry Cough Gastroindestinal - Diarrhoea and Jaundice General - Fever Cardiovascular - Myocarditis
86
What is an overview of Typhoidal Salmonellosis: Enteric Fever?
Incubation: 7-14 days after ingestion Duration: several days Infective Dose = 105 organisms (100,000)
87
What is an overview of Typhoidal Salmonellosis: Enteric Fever symptoms?
1st week: slowly increasing fever, headache, malaise, bronchitis 2nd week: Apathy, Anorexia, confusion, stupor 3rd week: rose spots (1-2 mm diameter on the skin): duration: 2-5 days, variable GI symptoms, such as abdominal tenderness (majority), abdominal pain (20-40% of cases) and diarrhea
88
What are longterm symptoms to Enteric Fever?
Neuropsychiatric - delirium and mental confusion Long term effects - arthritis
89
What is an overview of Typhoidal Salmonellosis disease length?
Late stage complications include intestinal perforation and gastrointestinal hemorrhage Immediate care such as increase antibacterial medications or surgical resection of bowel Majority of bacteria gone from stool in 8 weeks; However, 1-5% become asymptomatic chronic carriers: gallbladder is the primary source of bacterium
90
What is an overview of being a Typhoidal Salmonellosis carrier?
1-4% of untreated patients become chronic carriers (large environmental source of infection – shedding into environment). Excrete for more than 1 year.
91
What are the human health costs of being a Typhoidal Salmonellosis carrier?
Stool carriage is more frequent in people with preexisting biliary abnormalities and these people have a greater incidence of cholecystitis. Greater risk for carcinoma of the gallbladder 6-fold increase in the risk of death due to hepatobiliary cancer.
92
What is an overview of Typhoid Mary?
Infected some 50-120 people working as a cook as an asymptomatic carrier of Salmonella Typhi Estimates of up to 50 people died Typhoid Mary was quarantined for up to 30 years to prevent further infections
93
How does being a Typhoidal Salmonellosis carrier increase gallbladder problems?
They form biofilms around Gallstones where they can burst out and through toxins and immune response damage gallbladder epithelium
94
How is typhoid fever hard to control?
Long time between infection and symptoms Also asymptomatic carriers
95
What are other notable gram-negative pathogens?
Neisseria meningitidis and Neisseria gonorrhea Chlamydia spp Helicobacter pylori Haemophilus influenza Legionella pneumophila
96

3s2: Infection and Immunity (12 decks)

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