Question book 2 Flashcards
Which of the following must be handled in a safety cabinet at containment level 3?
serum from IVDU Toxoplasma serology Sputum for mycobacterial culture Blood from HBV positive patient Blood cultures from patient with fever with recent travel abroad
Sputum for mycobacterial culture
Class II biosafety cabinet, in Containment lab 3
31 year old with suspected TB. Sputum sample sent to the lab
Which statement is true about the sample
ZN stain components release toxic fumes
Auramine stain components release toxic fumes
Sputum should be prepared in class I biosafety cabinet
Sputum should be prepared in class II biosafety cabinet
Sputum should be prepared in class III biosafety cabinet
Sputum should be prepared in class II biosafety cabinet
Mycobacterium TB is a Containment level 3 agent, but only requires prep in Class II cabinet.
Class 4 pathogens eg Ebola, require Class III cabinet which is totally enclosed.
Class I biosafety protects users, but risk of specimen contamination
Class II biosafety protects users and specimen
Class III is fully enclosed, with fixed gloves
What are examples of stains used to help identify mycobacterial species?
ZN - uses carbol fuchsin to stain AFB red, then alcohol to wash, and then methylene blue counterstain
Auramine
Modified Kinyoun cold stain
Which one of these is a mandatory requirement for a CL3 lab?
high efficiency particulate air inlet laminated floor sealable for fumigation shower facilities air lock
sealable for fumigation
HEPA filter required on air leeaving lab, but no filters required on air entering the lab
What standard must packaging adhere to when sending sample by courier?
UN2814 UN2900 UN3291 UN3373 P650
UN3373 - suitable for most blood samples/ sputum whereby the specimen in its current form is unlikely to be life-threatening to courier
UN2814 - used when transporting high consequence pathogens eg brucella, ebola
Samples from HBV patient sent to lab for investigation. What is minimum laboratory safety criteria for processing these samples?
CL 1 CL2 CL 3 Class 2 safety cabinet Class 3 safety cabinet
CL2 - needs higher containment level to reduce risk of lab related injuries
Blood from HBV patient spilled in lab.
What is the best method for disinfection of the blood spill?
Phenolic compounds Alcohol Glutaraldehyde Hypochlorite Peroxymonosulphate
Peroxymonosulphate
Chlorine bleach products often used, but most of these arent registered with regulatory bodies to monitor use
CSF sample for CJD spilled on bench.
What is the best method for disinfection of the spill?
Phenolic compounds Alcohol Glutaraldehyde Hypochlorite Peroxymonosulphate
Hypochlorite
Rest of compounds have no activity, or actually stabilise the prion
When is it recommended to use formaldehyde for decontamination?
Bench top decontamination
Cleaning floor of laboratory
Fumigation
Cleaning of safety cabinets after fungal manipulation
Fumigation - it is the most commonly used substance for this. Requires prolonged time eg 12 hours room sealed over night. Formaldehyde is class 1 carcinogen, so should be avoided in other uses
What is treatment of scabies?
Topical permethrin
oral ivermectin if widespread, or Norwegian scabies
Following wedding party, reports of vomiting 24 hours later, but all report no further vomiting or diarrhoea after further 48 hours.
What is most likely cause?
Campylobacter spp Adenovirus Norovirus Bacillus cereus Staphylococcus aureus
Norovirus
Norovirus and rotavirus have very similar incubation periods of 24 hours, with quick resolution of symptoms
Campylobacter incubation normally 2-5 days
Adenovirus usually incubates 8-10 days
Staph aureus usually occurs 1-2 hours after ingestion
Bacillus cereus occurs 1-5 hours after ingestion
32 year old who works in abbatoir presents with fever.
Which organism is least likely to be the cause?
Brucella abortus Salmonella Typhi Streptococcus suis Coxiella burnetti Mycobacterium bovis
Salmonella Typhi - humans are only known reservoir
18 year old with meningococcal meningitis
Which community contacts will need prophylaxis?
Those who attended same classes as the index case that day
Those who ate lunch with the index case that day
Those who attended a party with the index case the evening before
Those who travelled on the bus next to the index case that day
Those who slept in the dormitory with index case on a field trip last week
Those who slept in the dormitory with index case on a field trip last week
Community contact is within past 7 days. Household contacts or student halls count for this
Sharing same car, sharing meal, same class all do not count
18 year old with meningococcal meningitis
Which community contacts will need prophylaxis?
Those who attended same classes as the index case that day
Those who ate lunch with the index case that day
Those who attended a party with the index case the evening before
Those who travelled on the bus next to the index case that day
Those who slept in the dormitory with index case on a field trip last week
Those who slept in the dormitory with index case on a field trip last week
Community contact is within past 7 days. Household contacts or student halls count for this
Sharing same car, sharing meal, same class all do not count
30 year old male presents with bloody diarrhoea. Shigella spp isolated, and send to reference lab for further sub-speciation.
When should this be notified to public health?
on presentation on discharge on isolating Shigella spp on receipt of reference lab sub-speciation does not need notified to public health
on presentation - bloody diarrhoea with possible common source needs notified to trigger an investigation
What are causes of bloody diarrhoea? (6)
Aeromonas Campylobacter E. coli Salmonella Shigella
Entamoeba histolytica
What are causes of large volume, watery diarrhoea?
Viruses 4
Bacteria 2
Parasite 2
Norovirus
Rotavirus
Astrovirus
Calicivirus
E. coli
Vibrio cholerae
Cryptosporidium
Giardia
Which virus is not killed by alcohol hand gel?
Coxsackie virus Influenza A HCV RSV HBV
Coxsackie virus
Other viruses are enveloped viruses, which are sensitive to detergents, heat, dessication.
Picironaviruses are non-enveloped
Which DNA viruses are non-enveloped?
Adenoviurus Papovavirus Parvovirus Poxviridae Hepadnaviridae
Enveloped
Poxviridae
Hepadnaviridae
Non-enveloped
Adenovirus
Papovavirus
Parvovirus
Which RNA viruses are non-enveloped?
Bunyaviridae Calicivirus Coronaviridae Filoviridae Flaviviridae Orthomyxoviridae Paramyxoviridae Picornavirus Reovirus Retroviruses Rhabodviridae Togaviridae
Calicivirus
Picornavirus
Reovirus
Patient with prolonged hospital stay, and multiple antibiotic courses.
He is colonised carbapenemase-producing Klebsiella pneumoniae, which is confirmed as colistin resistant .
Two further patietns on ward test positive for same organism, on active surveillance. An outbreak is declared.
What is the most likely mechanism of colistin resistance in this organism?
Expression of chromosomal carbapenemase gene
Expression of plasmid containing mcr-1 gene
Porin loss with hyper-expression of AmpC cephalosporinase
Alteration of target site in gram-neg outer membrane
Expression of bla-kpc gene
Expression of plasmid containing mcr-1 gene
mcr-1 gene confers resistance to polymyxins such as colistin.
Rapid spread of resistance suggests plasmid mediated transfer
carbapenemase gene and AmpC gene would not confer resistance to polymyxins
Which gram neg bacteria are intrinsically resistant to colistin?
BBMPS
Burkholderia Brucella Morganella Proteus Serratia
65 year old has glycopeptide resistant enterococcus on rectal swab.
What is the greatest predisposing risk factor for this?
Repeated enemas Metronidazole use Persistent diarrhoea Urinary catheterisation Inflammatory bowel disease
Metronidazole use.
Any antibiotic use increases risk of glycopeptide-resistant enterococcus
Catheterisation increases risk, but not on its own, only in setting of antibiotic usage
65 year old has glycopeptide resistant enterococcus on rectal swab.
What is the greatest predisposing risk factor for this?
Repeated enemas Metronidazole use Persistent diarrhoea Urinary catheterisation Inflammatory bowel disease
Metronidazole use.
Any antibiotic use increases risk of glycopeptide-resistant enterococcus
Catheterisation increases risk, but not on its own, only in setting of antibiotic usage
65 year old found to be colonised with MRSA.
What is greatest predisposing risk of acquiring MRSA
volunteer in day care centre
resident in elderly care home
two pet dogs at home
live with large extended family, including school age children
uncomplicated elective hip operation 12 months ago
resident in elderly care home
generally 20% people are colonised with MRSA.
general public is actually 2%, and elderly/ care home people is 20%
Operation that is uncomplicated, a long time ago, is unlikely to be implicated
65 year old develops diarrhoea with Clostridioides difficile
What is greatest predisposing risk factor
use of probiotics use of PPI use of metformin use of H2 antagonist use of octreotide
use of PPI
65 year old develops diarrhoea with Clostridioides difficile
What is the greatest risk factor for this disease?
previous cephalosporin use previous co-amoxiclav use previous clindamicin use previous ciprofloxacin use previous PPI use
previous clindamicin use
Antibiotics have much higher risk than PPI use
In ranking from most likely to cause: clindamicin by far the worst quinolones cephalosporins penicillins - lowest risk
IPC team are taking a 1-day snap-shot of all infections in inpatient wards at any one time.
What type of study is this?
case-finding study case-control study cohort study prevalence study controlled trial
Prevalence study
Prevalence study is a cross-ectional snapshot of frequency of disease in a population at a particular time.
Does not allow investigation of association or causation
Case-finding study is used to find patients with a certain disease or constellation of symptoms. For example in patients with TB exposure during contact tracing exercise
Outbreak of diarrhoea and vomiting at a wedding. Clinical, epidemiological and dietary information is available about all guests. What is the most appropriate epidemiological investigation to find the cause?
case-control study correlation study cross-sectional study randomised control trial retrospective cohort study
Case-control
Useful when rare outcome - e.g guests who have vomiting and diarrhoea at wedding. Look back at what food they ate
retrospective cohort is more useful if we know the suspected risk factor e.g undercooked chicken. We can look back at groups who ate, and who did not eat the food. And see what the association with symptoms is. These studies compare the occurrence of disease among those who were exposed to a suspected risk factor with
occurrence among those who were not
Patients with pulmonary TB usually need to be in side-room until first two weeks of treatment complete
Do the following patients need to be in side room:
- smear positive sputum
- smear positive induced sputum
- patient who is still smear positive after two weeks of therapy
- smear positive on BAL
Need side room
- smear positive sputum
- smear positive induced sputum
Does not need side room - as long as no immunocompromised patients on ward
- patient who is still smear positive after two weeks of therapy - smear positive but bacteria may be dead
- smear positive on BAL
When investigating a TB patient for contacts, how far back should it stretch?
3 months from first positive sputum sample
Anaesthetics lead wants to introduce a new reusable airway device. Which disinfection method might be most approrpriate?
70% alcohol Gluteraldehyde Porous load autoclave 125 ppm hypochlorite Chlorhexidine
Porous load autoclave - although manufacturer must advise how many times can be cleaned
Airway devices need to be sterile, not just disinfected.
70% alcohol or chlorhexidine or 125 ppm hypochlorite are low level disinfection agents
Gluteraldehyde is high level disinfection, but does not kill bacterial spores.
34 year old with food poisoning, diagnosed with Salmonella Typhimurium
What is advice regarding return to work
3 neg stool samples 6 neg stool samples immediately as long as strict hand hygiene observed immediately after symptoms resolve 48 hours after symptoms resolve
48 hours after symptoms resolve
As this is not Salmonella Typhi
34 year old with food poisoning, diagnosed with Salmonella Typhi
Also works as a nurse
What is advice regarding return to work
3 neg stool samples 6 neg stool samples immediately as long as strict hand hygiene observed immediately after symptoms resolve 48 hours after symptoms resolve
3 neg stool samples
Salmonella Typhi, or Paratyphi requires evidence of clearance
If they are involved in food preparation - require 6 neg stool samples
Stool samples must be 3 weeks after treatment complete, and taken 1 week apart
