Microbiology and Infection Flashcards
Which micro-organism is associated with re-heating rice or starchy foods?
Bacillus cereus
Name a common cause of healthcare associated diarrhoea
Clostridium difficile
Which toxins does clostridium difficile produce?
Toxins A and B
When will Clostridium difficile often become a problem for a patient?
After antibiotic use
The bacteria is a normal part of the gut flora in older patients and infants. After antiobiotic use, much of the gut flora is wiped out allowing for C. diff to proliferate more than it normally could in the presence of competition from the natural flora
What are the symptoms like for C. diff infection?
- Pseudomembraneous colitis - swelling/inflammation of the colon
- Diarrhoea - often bloody
- Abdominal pain
- Bowel perforation
What is the treatment for C. diff infection?
Metronidizaole or vancomycin
Why are vacomycin or metronidazole given in tablet form when treating C. diff infection?
To ensure the drug remains int he gut tube as much as possible
In order to prevent C. diff infection, which antibiotics should be avoided?
The 4Cs
- Clindamycin
- Cephalosporins
- Co-amoxiclav
- Ciprofloxacin
How should hands be disinfected?
Throrough handwashing
(not alcohol hand gel)
What are the main characteristics of C. diff?
- Gram +ve
- Bacilli
- Spore bearing
How can C. diff be diagnosed in the labratory?
- Screening for glutamate dehydrogenase (GHD)
- If GHD is present, toxins A and B are tested for
- If the strain needs to be typed, culturing may be necessary
Why would negative results be obtained for C. diff if the pathogen is present?
There is often intermittent release of toxin from the pathogen
Which virus is likely to infect people before the age of 5 and cause diarrhea and vomiting?
Rotavirus
What is the best treatment for rotavirus?
Oral rehydration
It is short lived and self limiting
When in the year is rotavirus most common?
Winter
What condition can children develop post-infection with rotavirus?
Post-infection malabsorption
This can lead to further diarrhoea
How can rotavirus be diagnosed?
PCR
(on faeces, or vomit)
How can rotavirus be prevented?
Via a live attenuated vaccine
2 doses are given to infants at 2 and 3 months
Norvirus has which classic symptom?
Explosive diarrhoea
How is norovirus spread?
- Faecal/oral
- Droplets
- Person to person contact
What is the incubation time for norovirus?
<24 hours
How can norovirus be diagnosed?
PCR
(on faeces or vomit)
In terms of infection control what is the most important thing to remember about norovirus after infection?
There is a period of around 48 hours after infection of asymptomatic shedding
Patients at this stage are still infectious, yet less so than when symptoms were present
Where is infection with norovirus most common?
In enclosed environments involving close contact
Examples include cruise ships, schools are hospitals
Which chart can be used to determine a type of stool?
The Bristol Stool chart
What time range would classified as short incubation?
1-6 hours
Short term incubation is short because of what?
The incubation time is due to release of preformed toxins from micro-organisms and not proliferation
What are two common causes of short-term incubation?
- Staph aureus
- Bacillus cereus
Why is Bacillus cereus commonyl associated with poorly reheated food?
It has heat resistant spores which can survive adverse conditions
Meats, fish and poultry are associated with which length of incubation time?
Short incubation
They can be associated with Bacillus cereus and Staph aureus
Poorly stored food leads to a massive histamine reaction and toxins tmulate outpouring of fluid into the bowel lumen causing profuse diarrhoea
What timeframe would be classed as medium incubation?
12-48 hours
Which two pathogens are commonly associated with food poisoning and medium incubation times?
- Salmonella
- C. perfingens
What timeframe woul dbe classed as a long incubation time?
2-14 days
Which two pathogens are associated with food poisoning and a long incubation time?
- Campylobacter
- E. coli 0157
What is the most common cause of food poisoning?
Campylobacter
(in the UK)
Salmonella causes food poisoning and is associated with what?
Outbreaks
Which bacteria may cause bacteraemia in immunocompromised patients?
- Campylobacter
- Salmonella
These bacteria can be invasive
Where is a camplobacter infection likely to come from?
- Raw milk
- Raw poultry
How can a campylobacter infection be treated?
Macrolide antibiotic such as clarithromycin
Generally it is self limiting
What is the most common species of campylobacter?
C. jejuni