Microbiology 4 (Dr Orange) Flashcards
What is the incubation period?
the time between contracting the infection (i.e. swallowing the organsim) and the first clinical symtpoms/ signs of infection
What avoidable circumstances are most infections in the community related to?
Cross-contamination of work surfaces/ utensils
Undercooking (insufficient heat to kill off pathogens), linked to inadequate defrosting of frozen food
Improper storage of food (inadequate refrigeration)
Poor reheating of food
What are the purpose of local microbiology laboratories in terms of when they find a GI infection? (2)
All GI infections reported promptly to local Health Protection Team
All isolates sent to Scottish Reference Lab
Where are all isolates from local labs sent?
Scottish Reference Labs
What do the reference labs do to isolates?
Collect them and perform further typing (linking of isolates across Scotland)
What is the role of health protection teams?
Receive reports of GI infections from local labs and send environmental health officers out to interview patients and find origin of infection
What is a common cause of healthcare-associated diarrhoea?
Clostridium difficile
What age of patients carry C diff as part of their normal bacterial flora?
Infants
Elderly (less commonly)
What causes the patient to become unwell with C diff.?
Production of toxins
What toxins are produced by C diff?
Toxin A (enterotoxin) Toxin B (cytotoxin)
What is the source/ vehicle of infection of C diff?
Present in bowel in small numbers in a number of people
When antibiotics prescribed, it kills off the normal competitive bowel flora allowing C diff to overgrow
Organism produces spores that survive in the environment dn are more resistant to disinfectants
Organism is transmitted from one patient to another
Symptoms of C diff?
Diarrhoea (sometimes bloody)
Abdo pain
Severe cases may progress to pseudomembranous colitis or bowel perforation
Management of C diff?
Depends on severity assessment:
Less severe = oral metronidazole
Severe = oral vancomycin
Prevention of C diff? (4)
Stewardship
Isolate patients
Hand washing (not alcohol)
Cleaning the environment
What type of bacteria is c diff?
Gram positive spore-bearing bacillus (spores more resistant to disinfectants)
There is no one good lab test for C diff? - true/ false
True
What lab tests can be performed for the diagnosis of C diff?
Screening test for presence of the organism (GDH)
If GDH positive, test for presence of toxin (toxin A and B)
Culture can be done if strain needs to be typed - not done routinely
Does the patient have c diff if the screening test is negative?
No
Does the patient have c diff is the screening test pos, toxin test pos?
Positive result
Does the patient have c diff is the screening test pos, toxin test neg?
Indeterminate result
What is the action plan if the lab tests for C diff are indeterminate?
Assess patient
Send repeat specimen (usually also indeterminate result also so have to make clinical decision - faeces usually smells of “horse shit” so ask experienced nurse if they think the patient has C diff
During what season are more cases of C diff seen?
Why is this thought to be the case?
Winter
Increased number of admission and possibly linked to the norovirus
Give an example of a hospital-acquired infection which is nationally surveyed?
C diff (can also occur in the community)
What 2 ribotypes of C diff are hyper-producers of toxin (leading to an increased morbidity and risk of death?
Ribotypes 027 and 078
Viruses that cause diarrhoea? (2)
Rotavirus
Norovirus
What is the commonest cause of Diarhhoea and vomiting in children
Rotavirus
Do you get blood in the stool with rotavirus?
No
How is roravirus spread?
Person-person spread, direct or indirect
What months are the rotavirus more common in?
Winter months
Do adults tend to experience severe symptoms with rotavirus?
No, they tend to get subclinical or mild symptoms (can be severe in immunocompromised children)
How long does rotavirus tend to last?
Around 1 week
Does the rotavirus have a high or low infectious dose?
Low
What features make rotavirus easily spread?
Survives in the environment
Billions shed in faeces when diarrhoea
Why do patients with rotavirus get dehydrated?
Decreased absorption of fluids and increased secretion in bowel causing dehydration
What can patients develop after rotavirus that causes more diarrhoea?
Post-infection malabsorption
How is rotavirus diagnosed?
PCR test on faeces
What is the key management for rotavirus?
Rehydration (orally where possible)
How is the rotavirus vaccine given?
doses?
Who is it not given to?
Orally (live attenuated vaccine excreted in the faeces)
2 doses, age 2 and 3 months
Not given to children > 24 weeks as high risk of intussusception
What is the technical name for the winter vomiting disease?
Norovirus - can occur all year round
what ages does norovirus tend to affect?
All ages (highly infectious)
How is norovirus spread?
Faecal-oral/ droplets routes of spread
Person to person (or contaminated food/ water)
Does norovirus have a low or high infectious dose?
Low
Incubation period of norovirus?
Short - often
What is the symptoms of norovirus?
Sudden onset explosive diarrhoea lasting 2-4 days
Vomiting leading to widespread contamination of environment = outbreaks
Diagnosis of norovirus?
Faeces specimen or vomit swab for PCR
Treatment of norovirus?
Rehydration (especially in the young and elderly)
How long after cessation of symptoms of norovirus are you infectious?
Up to 48 hours (asymptomatic shedding)
When are patients with a diarrhoeal illness most infectious?
When symptomatic with diarrhoea (remember not all diarrhoea is due to infection)
What 2 infections should patients definitely be given a side room with?
C diffiile
Norovirus
(all patients with diarrhoea that might be infectious should be placed in a single room without toilet/ commode) - cohort nursing in bays may be required during outbreaks on wards when there is not enough single rooms available
Wards may be closed
Increased ward cleaning/ disinfection required
What are 2 examples of GI infections with which patients may require admittance to the infectious diseases unit?
Salmonella
E coli O157
What other infections (apart from diarrhoea organisms) mat be spread by the faecal-oral route?
Hepatitis A and E
Resistant bacteria that are carried in the GI tract e.g. vancomycin-resistant enterococci
Highly resistant Gram negative organisms (CPEs)
What is cohort nursing?
All patients with the same infection nursed together with their own team of nurses
What should be used to clean / disinfect a room after a patient with diarrhoea infection has stayed in it?
Hypochlorite
What causes travel related diarrhoea? (3) - parasites
Amoebiasis
Giardiasis
Cryptosporidasis
How to treat traveler diarrhoea?
Single dose of ciprofloxacin
Anti-diarrhoeals
How to treat amoebiasis infection?
metronidazole + remove from lumen using diloxamide fruit or paromycin
How is ameobas spread?
Faecal-oral route
How are amoebas diagnosed?
Exam stool for ova
