Bacterial Virulence

Question 1

What do virulence factors contribute to?

Answer 1

The microbes ability to cause pathology

Question 2

What is the function of adhesin?

Answer 2

Enables the binding of the organism to host tissue

Question 3

What is the function of invasion?

Answer 3

Enables the organism to evade a host cell/tissue

Question 4

What is the function of impedin?

Answer 4

Enables the organism to avoid host defence mechanism

Question 5

What is the function of aggressin?

Answer 5

Causes damage to the host directly

Question 6

What is the function of modulin?

Answer 6

Induces damage to the host indirectly

Question 7

What are the factors responsible for the variation in virulence within and between species?

Answer 7

Adhesin
Impedin
Aggressin

Question 8

What are the infections of the skin most commonly?

Answer 8

Gram +ve staphylococcus and streptocuccus

Question 9

What differentiates staph aureus and staph epidermidis?

Answer 9

Coagulase test

Question 10

Where is staph aureus common?

Answer 10

Anterior nares and perineum

Question 11

Where is staph aureus contracted?

Answer 11

Nosocomial and community

Question 12

What is MRSA defined by?

Answer 12

Flucloxacillin resistance

Question 13

Who gets MRSA and where?

Answer 13

Nosocomial
Elderly and immunocompromised 
ICU
surgical patients
IV lines
Dialysis patients

Question 14

Where is staph epidermidis common?

Answer 14

Skin and mucous membrane

Question 15

Who gets staph epidermis?

Answer 15

Nosocomial infection in immunocompromised

Question 16

What is staph epidermidis associated with?

Answer 16

Foreign devices e.g. catheters

Question 17

What does superficial staph aureus look like?

Answer 17

Lesions- boils to abscesses

Question 18

What is the toxinoses risk with S. aureus?

Answer 18

Toxic shock, scared skin syndrome

Question 19

What is the role of fibrinogen binding protein in staph aureus?

Answer 19

Adhesin

Question 20

What is the role of coagulase in staph aureus?

Answer 20

Clots plasma

Question 21

What is the role of leukocidin (PVL) in staph aureus?

Answer 21

Kills leukocytes

Question 22

What is the role of TSST-1 in staph aureus?

Answer 22

Shock, rash, desquamation

Question 23

What is the progression and symptoms of TSST-1?

Answer 23

Rapid progression (48hrs)

High fever

vomiting

diarrhoea

sore throat

muscle pain

Question 24

What is the progression and symptoms of staphylococcal food poisoning?
enterotoxin SeA, SeB, SeC

Answer 24

intoxication
1-5hrs
vomiting diarrhoea

Question 25

Describe SSS

Answer 25

>exfoliation toxins, often neonatal, face, axilla and groin | >ETA & ETB toxins target Desmoglein-1 (DG-1)

Question 26

What is a super antigen?

Answer 26

activate 1 in 5 T cells (normally 1:10,000) Antigen is not processed by PMN and binds directly to MHCII complex outside of conventional binding groove

Question 27

What is the result of super antigen activation?

Answer 27

Massive release of cytokines and inappropriate immune response

Question 28

What are the diagnostic criteria for TSS?

Answer 28

-Fever >39 -Diffuse macular rash and desquamation (diffuse macular erythroderma- suburn) -hypotension =90mmHg in adults ->/=3 organ systems involved liver, muscular, blood, renal, mucous, GI , CNS

Question 29

What are adhesins?

Answer 29

Extracellular matrix molecules are present on epithelial, endothelial surfaces as well as a component of blood clots

Question 30

Name three adhesins

Answer 30

Fibrinogen binding (ClfA ClfB) Collagen binding (CNA) Elastin binding protein (EbpS)

Question 31

What is Panton-Valentine Leukocidin?

Answer 31

PVL bicomponent toxin (lukS and lukF) Specifically toxic to leukocytes

Question 32

What is PVL associated with?

Answer 32

Severe skin infections | e.g. recurrent furunculosis, sepsis/necrotizing fasciitis

Question 33

What are PVL and alpha toxin linked to?

Answer 33

CA-MRSA responsible for necrotising pneumonia and contagious severe skin infections

Question 34

What is necrotising pneunomia?

Answer 34

Preceding influenza like syndrome, neutralising haemorrhagic pneumonia

Question 35

Describe the presentation of necrotising pneumonia?

Answer 35

Rapid progression ARDS Deterioration in pulmonary function Refractory hypoxaemia Multi-organ failure despite antibiotic therapy

Question 36

Describe streptococcus pyogenes?

Answer 36

Gram +ve cocci in chains Catalase negative B haemolysis

Question 37

What infections does streptococcus pyogenes cause?

Answer 37

Impetigo Cellulitis Necrotising faciitis

Question 38

What is the lancefield system,?

Answer 38

Serotyping of cell wall carbohydrates

Question 39

How many major lancefield serotypes are there?

Answer 39

A-H and K-V (20)

Question 40

How are group a lancefield further divided?

Answer 40

M protein antigens - M1 & M3 major serotype - M3 & M18 severe invasive disease - emm typing and emm89 epidemic

Question 41

What are the GAS skin diseases?

Answer 41

Impetigo Cellulitis Erysipelas

Question 42

Describe impetigo

Answer 42

Highly contagious through contact with discharge on the face. infection immediately below surface (stratum corneum-keratin layers)

Question 43

Describe cellulitis

Answer 43

deeper skin infections in the dermis not associated with necrosis

Question 44

Describe erysipelas

Answer 44

Fever, riggers, nausea

Question 45

What are the iGAS diseases?

Answer 45

Invasive group A streptococci - cellulitis - necrotising fasciitis

Question 46

Describe necrotising fasciitis

Answer 46

>Type I, clostridia spp >invasive streptococcus A strains penetrate mucous membrane and develop in lesion >rapidly destroys connective tissue

Question 47

What proteins are responsible for tissue/cell destruction?

Answer 47

Haemolysins | Streptolysin S

Question 48

What is the role of SLS?

Answer 48

Pore forming cytolysis | Toxic to PMN, organelles, platelets, important in animal models

Question 49

What are the virulence factors of Streptococcus pyogenes?

Answer 49

Superantigenic towns Haemolysins Capsule ``` M-protein binds; >factor M >fibrinonectin >fibrinogen >albumin ```

Question 50

Describe TSLS (toxic shock like syndrome)

Answer 50

``` Pyogenic exotoxin -complication of invasive infections -30% mortality -hours to days hypotension to organ failure -SpeB, SpeC ```

Question 51

What is a pyrogen

Answer 51

Agent that causes a raise in body tissue

Question 52

Describe S.aureus toxic shock

Answer 52

- localised infection - no bacteraemia - menstrual TSST-1 - non-menstrual SEB or SEC - pyrogenic toxin

Question 53

Describe S. pyogenes toxic shock

Answer 53

- invasive disease (pharyngitis - SpeA and SpeC most common toxin - pyrogenic toxin

Question 54

What do S. aureus and s. pyogenes toxic shock have in common?

Answer 54

Virulence factor: Superantigen

Question 55

What are the stages of horizontal gene transfer between bacteria?

Answer 55

a. bacterial transformation b. bacterial transduction c. bacterial conjugation