Microbiology Flashcards
Campylobacter How does this appear on gram stain? Incidence? What does it cause? Source/vehicle of infection? Treatment? Complication?
Gram negative - looks like little pink seagulls
Commonest cause of bacterial GI infection in the UK
Inflammation of the colon and rectum - bloody diarrhoea, abdo pain, can occasionally get into the blood stream, can mimic appendicitis
Under cooked poultry, unpasteirised milk, water - classic case is under cooked turkey
Self limiting - if systemic illness develops, then give clarithromycin or or ciprofloxacin
Guillain-Barre is a rare but serious complication
Salmonella enterica Mechanism of action? Symptoms? Source of infection? Treatment?
Causes inflammation of ileum and colon - multiply in gut and cause mucosal damage, decreased fluid absorption, increased fluid excretion
D&V, P, fever, septicaemia
Meat, eggs, undercooked poultry, farm animals
Self limiting; if systemic illness, give ciprofloxacin
Shigella sp Incidence? Mechanism of action? What is seen in stool? Source/vehicle of infection? Symptoms? Management?
Outbreaks tend to occur every few years amongst cohorts of vulnerable children
Invades intestinal mucosa causing severe inflammation
Blood and pus in stool
Human-human spread only, tends to occur in young children
Abdo pain, diarrhoea, occasionally bloody
Self limiting, but if systemic illness, give ciprofloxacin
E.coli 0157 What does it commonly cause in the kidneys? Source/vehicle of infection? Symptoms? Management?
Produces an enterotoxin (verotoxin), that damages red cells in the kidney, causing haemolytic-uraemic syndrome (HUS)
carried as part of normal gut flora in cattle - from mince meat/ nursery visits to farms, private water supplies
Abdo pain, bloody diarrhoea
Supportive and symptomatic treatment ONLY - antibiotics may increase the release of verotoxin
Haemolytic Urean Syndrome Who usually gets it? Pathogenesis? Presentation? Bloods?
Under 16 yo
E.coli infection of gut mucosa causes the release of verotoxin, which binds to receptors found on renal and RBCs, inhibiting protein synthesis and causing cell death
Abdo pain, fever, pallor, haemorrhages in skin, oliguria, bloody diarrhoea
High lactate dehydrogenase
Typhoid/paratyphoid fever What organisms cause these and how are they spread? Pathogenesis What are these? Symptoms? Diagnosis? Treatment?
Salmonella typhi, salmonella paratyphi - food and waterborne
Invades gut & lymphatic system, invades blood stream, invades Peyer’s patches in gut
These are febrile illnesses initially causing headache, flu-like symptoms, abdo pain, contipation, then diarrhoea three weeks later, rose spots on trunk,
Blood cultures are key to diagnosis
Antibiotics - resistance to ciprofloxacin is growing in developing countries
Cholera What organism causes it and how does it appear on gram stain? How is it spread? Mechanism? Treatment?
Vibrio cholerae- gram negative curved bacillus
Faeco-oral, e.g. drinking contaminated water
Orgamism produces exotoxin that causes active outpouring of fluid from cells of small intestine, resulting in severe watery diarrhoea (“rice water”)
Fluid and electrolyte replacement is essential; antibiotics are not indicated
Staph aureus
What is the example of spread that Dr Orange gave?
Bakery worker with infected finer touches a cream cake, Staph aureus multiplies in cream cake, producing enterotoxin, which customer ingests, acting on vagus nerve, causing rapid vomiting
Clostridium perfringens
How does it appear on gram stain?
Associated with what food?
Symptoms?
Large gram positive anaerobic bacillus
Inadequately refrigerated re-heated meat gravy
D, P, afebrile
Cryptosporidium
What type of organism?
Spread?
Management?
Parasite
Cows –> water –> man
Can also get from swimming pools, as cysts are resistant to chlorine
Symptomatic treatment only
Giardia lamblia What type of infection? How is it spread? Symptoms? Diagnosis? Management?
Protozoa
Faecal-oral, e.g. MSM, immunosuppression, travel, swimming, cysts in drinking water
Often asymptomatic, but may be bloating, flatulence, abdo pain, loose stools, weight loss, explosive stool, foul smelling
Diagnosis is by stool microscopy for ova and cysts, but more accurately by duodenal aspiration
Oral metronidazole
Enterobius vermicularis ("threadworms")
What type of infection?
TreatmentTiny white worm, seen in school children hint hint
Oral mebendazole
What do you catch Bacillus cereus from?
Rice
What is gastroenteritis?
What causes it?
What are the main clinical problems?
Inflammation of the stomach or intestines - inhibits nutrient absorption causing excessive H20 and electrolyte loss
It can be bacterial; viral; parasitic; poisoning by microbial toxins
Mostly viral, but can be bacterial or parasitic
Fever, abdo pain, diarrhoea, sometimes PR
Toxin mediated food poisoning
What organisms can cause this?
Timing?
Symptoms?
Staph aureus (most common), Clostridium perfringens, Bacillus cereus etc Onset 1-6 hours after exposure, diarrhoea for a few hours, abdo pain, afebrile, resolves in 6-10 hours No blood or pus in faeces
