Week 8: Digestive system (bacterial)

Question 1

Facultative organisms of mouth and pharynx (3)

Answer 1

Streptococci spp. (eg S. mutans), Neisseria meningitidis, branhamella catarrhalis

Question 2

Anaerobic organisms of mouth and pharynx (3)

Answer 2

Bacteroides, fusubacteria, spirochetes

Question 3

Should bacteria be found on clean teeth?

Answer 3

No

Question 4

What initiates adherence of bacteria to teeth?

Answer 4

Proteins in saliva

Question 5

What causes dental caries (decay)?

Answer 5

Accumulation of microorganisms and their products

Question 6

Streptococcus mutans

Answer 6

Produces dextran from glucose while fructose is broken to lactic acid that breaks enamel, causing tooth decay

Question 7

Dysentery definition

Answer 7

Severe diarrhoea with blood and mucous

Question 8

How do bacteria cause disease after food is cooked?

Answer 8

Bacterial toxins cannot be destroyed by heat.

Question 9

How does shigella cause mucosal abscesses in shigellosis (bacillary dysentery)?

Answer 9

Shigella enters and multiplies inside epithelial cells. The abscess forms as epithelial cells are killed by the infection.

Question 10

4 species of shigella

Answer 10

Dysenteriae, flexneri, sonnei, boydii

Question 11

What toxins are produced by shigella?

Answer 11

Shiga toxins 1 and 2 (ST1 and ST2) aka verotoxins

Question 12

Explain the Kauffman White classification scheme

Answer 12

Used to classify salmonella into serotypes based on O antigen in outer membrane LPS, flagella (H) antigen and virulent (Vi) antigen surrounding O antigen

Question 13

3 main species of salmonella

Answer 13

Typhi, Cholerasuis, enteritis

Question 14

Salmonella is responsible for

Answer 14

Salmonellosis (salmonella gastroenteritis)

Question 15

Where is salmonella found

Answer 15

Raw egg, chicken, meat

Question 16

Typhoid fever cause

Answer 16

Salmonella typhi

Question 17

What differentiates S. typhi from other salmonella?

Answer 17

Multiplies in phagocytic cells compared to intestinal cells

Question 18

What causes cholera and how is it transmitted?

Answer 18

LT toxin of Vibrio cholerae, faecal oral route,

Question 19

Which serotype of V. cholerae causes epidemic and pandemic cholera

Answer 19

Classical O1 serotype

Question 20

Which new strain of V. cholera causes pandemic cholera

Answer 20

O139 (bengal strain)

Question 21

Cholera signs

Answer 21

Rice water diarrhoea

Question 22

Vibrio parahaemolyticus characteristics

Answer 22

Found in sea food, causing food poisoning via heat stable haemolysin (thermostable direct haemolysin aka kanagawa haemolysin)
Requires high NaCl for growth

Question 23

6 types of E. coli

Answer 23

Enteropathogenic (EPEC)
Enterotoxigenic (ETEC)
Enteroinvasive (EIEC)
Enterohaemorrhagic (EHEC)
Enteroaggregative (EAggEC)
Enteroadhesive (EAEC)

Question 24

Where is E. coli normally found in body

Answer 24

GI tract

Question 25

Enteropathogenic EC

Answer 25

Epidemic diarrhoea Identified by serotyping

Question 26

Enterotoxigenic EC

Answer 26

Traveller's diarrhoea Heat labile toxin (LT): antigenic and destroyed by heat, high molecular weight heat stable toxin (ST): non-antigenic, not destroyed by heat, low molecular weight

Question 27

Enterohaemorrhagic EC

Answer 27

Produces cytotoxin VTEC which lyses RBC O157:H7 causes haemorrhagic colitis sand haemolytic uremic syndrome (renal failure) Found in undercooked hamburger meat

Question 28

Enteroinvasive EC

Answer 28

Same mechanism and antigens as shigella Bloody diarrhoea Test: causes keratoconjunctivitis in rodent eyes

Question 29

Enteroaggregative EC

Answer 29

Same mechanism as enteropathogenic EC Adheres to enterocytes Similar toxin to stable toxin (ST) of ETEC

Question 30

Helicobacter pylori

Answer 30

Stomach ulcers and stomach cancer

Question 31

Campylobacter

Answer 31

Normal flora in domestic animals C. jujeni causes food poisoning C. fetus causes abortion in animals

Question 32

Yersinia motility, spore formation, toxins, transmission

Answer 32

Non motile, no spores, enterotoxin and exotoxin, meat and milk

Question 33

Y. enterocolitica disease

Answer 33

Enterocolitis

Question 34

Y. pseudotuberculosis disease

Answer 34

Local and systemic necrosis

Question 35

Y. pestis disease

Answer 35

Plague (black death)

Question 36

Y. enterocolitica

Answer 36

ST enterotoxin Diarrhoea and fever, acute mesenteric lymphadenitis, septicaemia Produces B lactamase so resistant to penicillins and cephalosporins

Question 37

Clostridium perfringens

Answer 37

Intestinal contents of animals Exotoxin causes abdominal pain, diarrhoea and gas gangrene

Question 38

Clostridium difficile

Answer 38

Exotoxins A and B A is an enterotoxin Causes antibiotic associated (pseudomembrane) colitis Opportunistic

Question 39

Bacillus cereus gram and spore status

Answer 39

Gram positive, endospore forming

Question 40

Bacillus cereus habitat

Answer 40

Soil

Question 41

Bacillus cereus disease mechanism

Answer 41

Spores resist killing, produce toxin which causes diarrhoea Contaminated rice