Week 8: Digestive system (bacterial) Flashcards
Facultative organisms of mouth and pharynx (3)
Streptococci spp. (eg S. mutans), Neisseria meningitidis, branhamella catarrhalis
Anaerobic organisms of mouth and pharynx (3)
Bacteroides, fusubacteria, spirochetes
Should bacteria be found on clean teeth?
No
What initiates adherence of bacteria to teeth?
Proteins in saliva
What causes dental caries (decay)?
Accumulation of microorganisms and their products
Streptococcus mutans
Produces dextran from glucose while fructose is broken to lactic acid that breaks enamel, causing tooth decay
Dysentery definition
Severe diarrhoea with blood and mucous
How do bacteria cause disease after food is cooked?
Bacterial toxins cannot be destroyed by heat.
How does shigella cause mucosal abscesses in shigellosis (bacillary dysentery)?
Shigella enters and multiplies inside epithelial cells. The abscess forms as epithelial cells are killed by the infection.
4 species of shigella
Dysenteriae, flexneri, sonnei, boydii
What toxins are produced by shigella?
Shiga toxins 1 and 2 (ST1 and ST2) aka verotoxins
Explain the Kauffman White classification scheme
Used to classify salmonella into serotypes based on O antigen in outer membrane LPS, flagella (H) antigen and virulent (Vi) antigen surrounding O antigen
3 main species of salmonella
Typhi, Cholerasuis, enteritis
Salmonella is responsible for
Salmonellosis (salmonella gastroenteritis)
Where is salmonella found
Raw egg, chicken, meat
Typhoid fever cause
Salmonella typhi
What differentiates S. typhi from other salmonella?
Multiplies in phagocytic cells compared to intestinal cells
What causes cholera and how is it transmitted?
LT toxin of Vibrio cholerae, faecal oral route,
Which serotype of V. cholerae causes epidemic and pandemic cholera
Classical O1 serotype
Which new strain of V. cholera causes pandemic cholera
O139 (bengal strain)
Cholera signs
Rice water diarrhoea
Vibrio parahaemolyticus characteristics
Found in sea food, causing food poisoning via heat stable haemolysin (thermostable direct haemolysin aka kanagawa haemolysin)
Requires high NaCl for growth
6 types of E. coli
Enteropathogenic (EPEC)
Enterotoxigenic (ETEC)
Enteroinvasive (EIEC)
Enterohaemorrhagic (EHEC)
Enteroaggregative (EAggEC)
Enteroadhesive (EAEC)
Where is E. coli normally found in body
GI tract
Enteropathogenic EC
Epidemic diarrhoea
Identified by serotyping
Enterotoxigenic EC
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
Enterohaemorrhagic EC
Produces cytotoxin VTEC which lyses RBC
O157:H7 causes haemorrhagic colitis sand haemolytic uremic syndrome (renal failure)
Found in undercooked hamburger meat
Enteroinvasive EC
Same mechanism and antigens as shigella
Bloody diarrhoea
Test: causes keratoconjunctivitis in rodent eyes
Enteroaggregative EC
Same mechanism as enteropathogenic EC
Adheres to enterocytes
Similar toxin to stable toxin (ST) of ETEC
Helicobacter pylori
Stomach ulcers and stomach cancer
Campylobacter
Normal flora in domestic animals
C. jujeni causes food poisoning
C. fetus causes abortion in animals
Yersinia motility, spore formation, toxins, transmission
Non motile, no spores, enterotoxin and exotoxin, meat and milk
Y. enterocolitica disease
Enterocolitis
Y. pseudotuberculosis disease
Local and systemic necrosis
Y. pestis disease
Plague (black death)
Y. enterocolitica
ST enterotoxin
Diarrhoea and fever, acute mesenteric lymphadenitis, septicaemia
Produces B lactamase so resistant to penicillins and cephalosporins
Clostridium perfringens
Intestinal contents of animals
Exotoxin causes abdominal pain, diarrhoea and gas gangrene
Clostridium difficile
Exotoxins A and B
A is an enterotoxin
Causes antibiotic associated (pseudomembrane) colitis
Opportunistic
Bacillus cereus gram and spore status
Gram positive, endospore forming
Bacillus cereus habitat
Soil
Bacillus cereus disease mechanism
Spores resist killing, produce toxin which causes diarrhoea
Contaminated rice
