Gastro-intestinal microorganisms

Question 1

vibrio cholerae

Answer 1

cholera = severe diarrhoea. ingested in water contaminated by human faeces

Question 2

streptococcus bovis

Answer 2

gamma-haemolytic streptococcus of lancefield group D, which forms part f the normal flora of the lower GIT. cause of infective endocarditis and intra-abdominal sepsis. bacteraemia with S.bovis is occasionally associated with large bowel malignancy.

Question 3

shigella spp

Answer 3

dysentery. gram-negative bacilli. lactose non-fermenting coliforms. 4 species, only endemic one in UK is shigells sonnei –> dystentery (blood and pus in stools). low infestive dose so easily spread, tbreaks characteristically in pre-school nurseries

Question 4

salmonella

Answer 4

coliform (rod-shaped bacteria).. non fermenting gran negative rods. common cause of food poisoning following ingestion of raw eggs or poultry, especially s.enteritidis and s. typhimurium slamonella typhi and s.paratyphi cause enteric fever (typhoid)

Question 5

rotaviruses

Answer 5

most important cause of acute gastroenteritis in infants and young children
predictable annual epidemics in the winter and spring
oral live vaccine @ 2-3 months

Question 6

norovirus

Answer 6

outbreaks of diarrhoea and vomiting

much underdiagnosed with diagnosis by electron microscopy or PCR

Question 7

helicobacter pylori

Answer 7

curved gram negative bacilli
microaerophilic, strongly urease positive
causes gastritis and peptic ulceration

Question 8

e.coli

Answer 8

gram negative bacilli
lactose fermenting coliform, commensal of the GI tract
most common cause of UTI
also causes neonatal meningitis and some strains cause diarrhoea. E.coli 0157 cause bloody diarrhoea and haemolytic uraemic syndrome

Question 9

enterococcus

Answer 9

inhabitants of the human gut. gram positive cocci formerly classed as streptococci

Question 10

enterobacteriaceae

Answer 10

enteric gram negative bacilli aerobic
‘coliforms’
gram negative rods that ferment glucose and are oxidase negative. include E.coli, klebsiella, proetus, salmonella, shigella, Yersinia species

Question 11

clostridium perfringens

Answer 11

spore forming anaerobe
present in normal faeces
toxigenic strains can cause food poisoning. the main cause of gas gangrene but this is rare and most isolates from wounds represent faecal contamination. serious infection treated with penicillin and/ or metronidazole

Question 12

c. difficile

Answer 12

gram positive bacillus, spore forming anaerobe
cause of pseudomembranous colitis and antibiotic-associated diarrhoea
produces toxins and spreads easily in hospital due to spore formation. treated with oral metronidazole or vancomycin

Question 13

campylobacter

Answer 13

curved gram negative bacilli

microaerophilic and grows at42 degrees celcius. commonest bacterial cause of gastroenteritis in uk

Question 14

bacteroides fragilis

Answer 14

gram negative bacillus anaerobe
most predominant organisms in large bowel flora and faeces
often present in mixed intra-abdominal infections. resistant to penicillin but sensitive to metronidazole

Question 15

bacillus cereus

Answer 15

large brick shapes aerobic gram positive bacilli produce spores. causes an entero-toxin mediated food poisoning classically as a result of germination of spores in food that has been kept long for a prolonged time e.g. rice