Microbiology Flashcards
Which organism is the commonest cause of food poisoning?
Campylobacter
Which organisms are more likely to cause outbreaks of food poisoning?
Salmonella
E. coli 0157
What is the incubation period for Staph. aureus and Bacillus cereus?
Short
1-6 hours
Staph. aureus produces a toxin which is rapidly absorbed by the stomach. True/False?
True
What is the incubation period for Salmonella and Cl. perfringens?
Medium
12-48 hours
What is the incubation period for Campylobacter and E. coli 0157?
Long
2-14 days
Which foods does Campylobacter mainly colonise?
Poultry
Raw milk
Poor food preparaiton
Is Campylobacter likely to spread from person to person?
No
Which foods does Salmonella mainly colonise?
Poultry
Raw egg
Meat, animal guts
What is the significance of the antigens found on Salmonella?
Different antigens on different strains, so specific antibodies will agglutinate
Which foods does E. coli 0157 colonise?
Beef
Raw milk, water
Wide variety really
Is E. coli 0157 likely to spread from person to person?
Yes
Who is most at risk of complications from E. coli 0157 infection?
Children + elderly
What is the name of the toxin produced by E. coli 0157?
Verotoxin (VTEC)
Which syndrome can result due to verotoxin?
Haemolytic uraemic syndrome
What are the sites of action of antibiotics in a cell?
Cell wall
Cell membrane
Cytoplasm
DNA
What is the main class of antibiotic which acts on the beta-lactam ring on the cell wall of bacteria?
Pencillins
Does antibiotic use lead to antibiotic resistance?
Yes
How does antibiotic use have public health consequences for other people, in terms of resistance?
Resistant bacteria are selected out in presence of antibiotic, and can spread between patients
What is meant by antimicrobial stewardship?
Prescribing optimum dosage and duration of antimicrobial treatment that results in best clinical outcome, prevention of infection and minimal resistance
What is gastroenteritis and what is the consequence regarding absorption?
Inflammation of stomach and small intestine
Limits absorption of nutrients and water
Which out of bacteria, viruses and parasites is the most common cause of gastroenteritis?
Viruses
What is meant by toxin-mediated food poisoning?
Toxin has been preformed by the bacteria on the host before ingestion of food, leading to acute symptoms once the food has been eaten
List common organisms that produce preformed toxins
Stap. aureus
Clostridium perfringens
Bacillus cereus
E. coli 0157
Acute enteritis often presents with fever, diarrhoea, vomiting and abdo pain. Is the diarrhoea usually bloody?
No
Acute colitis often presents with fever, diarrhoea and abdo pain. Is the diarrhoea usually bloody?
Yes
What are the main organisms that cause bloody diarrhoea?
Campylobacter
Shigella
E. coli 0157
Amoebas
What is the usual duration of Campylobacter infection?
5-14 days
Typhoid is an enteric fever like illness caused by which organism?
Salmonella
Which type of culture - urine, stool or blood - is key to diagnosing typhoid?
Blood
Stool and urine would be done too though
Name the 4 main stool investigations for infectious organisms, from most used to least
Stool culture
Stool microscopy
Stool toxin
Stool PCR
Which stool investigation is appropriate for Salmonella, Campylobacter and Shigella?
Stool culture
Which stool investigation is appropriate for Giardia, Amoebas and parasitic infections?
Stool microscopy
Which stool investigation is appropriate for Clostridium Difficile and E. coli 0157?
Stool toxin
Which stool investigation is appropriate for Norovirus?
Stool PCR
Which 3 markers assess the severity of C. difficile infection?
Suspicion of pseudomembranous colitis/toxic megacolon/ileus
WCC greater than 15
High creatinine
What is first line treatment for gastroenteritis?
Oral rehydration or IV fluids
Which antibiotic is commonly used for non-severe C. diff?
Oral metronidazole
Which antibiotic is used for severe C. diff?
Oral vancomycin
NEVER IV
Which antibiotic is used for first recurrence of C. diff infection?
Fidaxomycin
Which organism is the most common cause of traveller’s diarrhoea?
E. coli 0157 (produces VTEC)
Which antibiotic is used for amoeba and giardia infections?
Metronidazole
What is the commonest cause of viral diarrhoea in kids under 3 years old?
Rotavirus
How is rotavirus spread?
Faeco-oral
Which virus is known as the winter vomiting bug?
Norovirus
How is norovirus spread?
Faeco-oral
Droplets
Describe the nature of vomiting that comes with norovirus
Explosive and sudden
Lead to environmental contamination
What is the diagnostic test for rotavirus and norovirus?
PCR, on stool or vomit
Define SIRS (systemic inflammatory response syndrome)
More than 2 of
Temperature over 38 or less than 36
RR over 20
WCC less than 4k or over 12k
Define sepsis
SIRS + suspected/confirmed underlying infectious process
What is involved in the sepsis 6 treatment?
Take blood cultures + FBC + urine output
Give fluids + antibiotics + oxygen
Which antibiotics are given for peritonitis/biliary tract intra-abdominal infection?
IV amoxicillin + metronidazole + gentamicin
vancomycin if pen-allergic
