Introduction to Microbial World (Bacteria)

Question 1

what are the relationships between humans and microbiota?

Answer 1

symbiosis = the long-term interaction between 2 different biological species

Question 2

what is an infection?

what is the difference between a primary pathogen and an opportunistic pathogen?

Answer 2

infection: multiplication of a bacterial pathogen within the host

• *primary pathogen:** causes disease when infection - not normally associated with host
• *opportunistic pathogen:** only causes disease in compromised host: sometimes part of normal flora

virulence: quantative ability of a microbe to cause disease

Question 3

what are 4 basic microbes that can cause pathogens?
what kingdom are they each/

Answer 3

• *1. bacteria:** prokaryote
• *2. viruses:** non living
• *3. fungi:** eukaryote
• *4. protoza:** eukaryote

Question 4

how do bacteria store DNA?

other general strucutture like?

• orgenelles like what?
• around outside?

how divide?

Answer 4

• *DNA/RNA:**
• *- single circular chromosome** that lies free in cytoplasm
• *-** sometimes: additional plasmids

structure:

• *-** free floating / non membrane organelles
• cell wall
• can have: flagella (motility)
• pili / fimbriae: adherence
• 70S rb (50S & 30S)

Division:
binary fission

Question 5

what is S of bacteria ribosomes?

Answer 5

70S ribosomes (two subunits with densities of 50S and 30S)

Question 6

what are some bacteria covered in?
what are pili used for?

what are bacteria spores?

Answer 6

some bacteria: capsulate (polysaccaride). evades immune response
pili: adherence to surfaces

bacterial spores: structures very resistant to physical & chemical agents. often go into dormant state. e.g. Bacillus anthracis, C. difficile

Question 7

name functions of bacterial cell wall

what are the two different types of bacterial cell wall?

Answer 7

function:

• protects agaisnt desiccation, osmotic shock & mech. shock
• protection agaisnt host immune system: specifc and non-specific
• adherence to surfaces

types:

• *- gram postive
• gram negative**

Question 8

what determines if bacterial cell wall is gram postive or gram negative?
what else is different between them?

what colours do they stain?

Answer 8

depends on level of peptidoglycan: (and therfore the staining)

• *- thick peptidoglycan:** gram postive - purple stain
  a) just one membrane
  b) lipotechoic acids sticking out
• *- thinner peptidoglycan:** gram negative - negative stain
  a) have inner and outer membranes
  b) lipopolysaccarides sticking out
  c) holes in outermembrane

Question 9

which one of these is gram +ve / -ve?

Answer 9

+ve = left / -ve right

Question 10

what are 3 main shapes of bacteria?

Answer 10

Spherical (cocci)

Cylindrical rod (bacilli)

Curved/spiral (spirochetes)

Question 11

differences between bacteria and eu cells?

Answer 11

• nucleus: eukaryotes - membrane-bounded, bacteria: floating (also plasmids)
• RB: eukaryotes: 80S (60S & 40S), bacteria: 70S (50S & 30S)
• organelles: eukaryotes - mitochondria, golgi apparatus, lysosomes, peroxisomes and ER, bacteria: not those

bacteria divide by binary fission

Question 12

what does gram stain rely on to show differences in bacteria?

what stain do u use for: a) Mycobacteria, b) fungi & c) spirochaetes? (probs dont need to know tbh)

Answer 12

differences in cell wall (amount of peptidoglycan):

• *- gram postive** = purple
• *- gram negative =** pink

• ( a) Mycobacteria: Zielh-Nielson stain
  b) fungi: Cotton blue stain
  c) spirochaetes: darkfield microscopy )*

Question 13

process of gram staining?

Answer 13

Gram stain: Crystal violet –> Iodine –> Ethanol –> Safranin

Question 14

how are gram postive cocci subclassed? how do u test?

Answer 14

gram postive cocci - to differentiate between cocci do catalase test

• streptococci: catalase negative
• straphylocci: straphylocci positiive

subclassify straphylocci further: coagulase stain:

• **straphylocci coagulase +ve
• straphylocci coagulase -ve**

subclassify Streptococci further:: if can lyse blood or not

• *- beta-haemolytic: lyse blood - complete haemolysis
• alpha-haemolytic:: partially lyse blood
• non-haemolytic: dont**

Question 15

how do subdivde & test for different:

a) Staphylococci?
b) streptoccoi?

Answer 15

• *staphylococci**: if can coagulate human serum or not
• • S. aureus (important human pathogen):* coagulates human serum: coagulase positive
• • S. epidermidis (non disease):* does not coagulate human serum: coagulase negative
• *Streptococci:** if can lyse blood or not
• beta-haemolytic: lyse blood - complete haemolysis
• alpha-haemolytic:: partially lyse blood
• non-haemolytic: dont

Question 16

what are staphylococcal disesases - localised and systemic/>

Answer 16

• *localised:
• pyogenic (**pus making)
• abscesses
• wound infections
• follicultis
• *- MSK:**
• osteomyelitis
• *- Resp infection:**
• sinustis
• pneumonia
• *generalised, systemic** (into blood)
• bacteraemia, sepsis, endocarditis (infection of heart)

Question 17

name 3 staphylococcoal diseases that caused by entrotoxins?

Answer 17

1. acute staph. enterocolitis (food pois)

• *2. staphylococcal ‘scalded skin’ syndrome:**
• Ritters disease
• caused by exofoliative exotoxin
• *3. toxic shock sydrome**
• severe immune response to certain strains of staph. cause superantigens: high fever, rash, low BP, coma, multple organ failure

Question 18

difference in structure of steptococci and staphylococci bacteria?

Answer 18

streptococcus: chains
staphylococcus: clusters

Question 19

how are beta-haemolytic steptococci divided?

Answer 19

groups: A-G

depends on which Lancefield antigen is detected on surface

Question 20

disease caused by Streptococcus pyogenes (Group A)?

Answer 20

• Streptococcus pyogenes* (Group A)
• sore throat
• fever
• rash (strawberry tongue) - scarlet fever
• tonislitis
• infection of upper dermis. if on face: erysipelas ; arm: cellulitis. deeper that skin: can develop into sepsis, flesh eating strep

Question 21

gram negative rod bacteria?

2 main groups?

Answer 21

gram negative rods:

• Obligate pathogens:**
  1. Salmonella sp: S. typhi, S. paratyphi*
  2. Shigella sp: S. dysenteriae, S flexneri, S. sonnei, S. boydii
  3. Klebsiella pneumoniae
  4. Yersinia sp: Y. entrocolticia, pseudotuberculosis
• *Opportunistic pathogens** (mostly live in our gut):
  1. Escherichia coli
  2. Enterobacter sp: E. aerogenes, cloacae
  3. Acinetobacter baumanii

Question 22

what are enterobacteriaciae?

Answer 22

Enterobacteriaceae are a large family of Gram-negative bacteria that includes a number of pathogens such as Klebsiella, Enterobacter, Citrobacter, Salmonella, Escherichia coli, Shigella, Proteus, Serratia and other species.

These pathogens are present in the human intestinal tract and are a normal part of the gut flora.

Question 23

what happens when enterobacteriaciae leave gut?

Answer 23

not good !

quite serious:

• wound infection
• UTI
• septicaemia
• neurosurgial meningitis
• pneumonia

Question 24

how can u classify enterobacteriaciae?

Answer 24

• *- fermentors
• non-fermentors**
• *fermentors**:
• bacteria differ in their ability to produce acids from different sugars (monosac, disac, polysac and alchohol fermentation). used to differentiate bacteria.

Question 25

what are multitest ID systems?

Answer 25

- combine dozens or organic / inorganic substrates: determine breakdown by colour changes - e.g. API (analytic profile index) 20: _gives a biochemical code for the metabolic profile of that organism_

Question 26

which bacteria arent detected by gram stain - why? which stain used instead - what shows up?

Answer 26

* *mycobacteria** - waxy cell wall - lipid rich: resistance to drying, antiobiotics and disinfectants, acids and alkalis, survives in macrophages - e.g. *M**ycobacterium tuberculosis* **stain: Ziehl-Neelson stain -**stained bright red (dont take up gram stain: called Acid-fast)

Question 27

why cant use gram stain for spirochaetes? name 2 diseases caused by ^?

Answer 27

too thin cell wall to see with gram stain - *Boreelia burgdoferi:* Lyme disease - *Treponema pallidium:* syphilis

Question 28

what important fungi that can see with gram stain?

Answer 28

*Candida sp:* much bigger cocci than bacteria. cause thrush

Question 29

what is Aspergilliosis?

Answer 29

**Aspergillosis** is an infection caused by a **type of mold (fungus).** The illnesses resulting from aspergillosis infection usually affect the **respiratory system,** but their signs and severity vary greatly.

Question 30

describe basic overview of protozoa which kingdom? how do u classify?

Answer 30

**unicellular eu. organism:** typical eu features but also species specific organelles found in all aq. enviroment (incl. soil and humans) **kingdom:** *Protista* **classify:** locomotion**: -**pseudopodia - flagella - cilia

Question 31

name some protozoal diseases pls (3 types)

Answer 31

**Apicomplexa:** *_Plasmodium sp (malaria),_ Toxoplasma gondii, Cryptosporidium* **Ameobae:** *Entamoeba histolytica* **Flagelletes:** *_Giardia (diarrhea, malabsorbtion), Leishmania_*

Question 32

what are Helminths? how classified?

Answer 32

- helminths: worms (intestinal parasites) - **classifcation:** - trematodes: **flat, non segemented** (e.g. Schisosomiasis) - flukes - cestodes: **flat, segemented** - tapeworms - nematodes: **round and non segmented**

Question 33

how do you diagnose infections?

Answer 33

need: - history of patient (travel, symptoms & duration, animals, food) - clinical exam - lab investigations: _haemotological, biochemical, microbiology / virology_

Question 34

what tests do u use if cant grow microbe (to test) ?

Answer 34

use **serological / immunological diagnosis**: look for antibodies being present / absent. important for _viral infections and hard to grow bacteria_

Question 35

future of bacterial ID? what are the techniques

Answer 35

- **MALDI-Tof MS** (mass spec) * *- molecular tests**: PCR (look for bacterial genes) - _standard PCR, Real-time PCR, Cephoid GeneXpert_ * *- whole genome sequencing - sequencing bacteria on usb things**