47. Infection Control Practical Flashcards
(66 cards)
Brain heart infusion agar is a growth media for culturing what?
fastidious microorganisms
What pathogenic organism can potentially contaminate dental clinic water supplies?
legionella pneumophilia
When incubating agar plates, why do they have to be placed top down?
to stop condensation settling on agar surface
Nutrient agar is selective for bacteria, fungi, viruses, nothing?
non-selective
Thorough and effective handwashing removes all microorganisms from hand surface?
no
Which of these is not true for Bacillus subtilis?
- gram positive
- rod-shaped
- spore forming
- opportunistic pathogen
- aerobic
opportunistic
The genus Bacillus is one of predominant bacteria genera found where?
soil
Bacillus cereus can cause what?
food poisoning
Bacillus anthracis causes anthrax so is potentially …
a bioterrorism agent
Does heating cells to 80 degrees replicate conditions in an autoclave?
no
Spores are more resistant than vegetative cells to what?
- disinfectants
- drying
- heating
- nutrient deprivation
Reactivation of bacterial spores is called what?
germination
Which of these is spore-forming?
- actinomyces israelli
- clostridium tetani
- helicobacter pylori
- mycobacterium tuberculosis
- staph aureus
- clostridium tetani
Which of these isn’t true about C.diff?
- gram neg
- rod shaped
- spore forming
- causes pseudomembranous colitis
- infection associated to use of antibiotics
- healthcare-associated infection
gram negative
How to kill spores?
- application of moist heat at 100-120 degrees or more for a period of 10-20 minutes
A patient comes in with an advanced periapical advance and acute pain. What is suspected and what is prescribed?
- chance it’s spreading in blood and can cause another infection in brain etc
- to reduce this chance, prescribe antibiotic regime without knowledge of organism
- drain it, send sample to lab and establish sensitivity to antibiotic
- given amoxicillin, clavulanic acid and metronidazole
A patient is prescribed amoxicillin, clavulanic acid then metronidazole, Explain what these do
- amox - moderate-spectrum antibiotic against lots of gram-pos and limited gram-neg
- metro - active against most gram-pos and gram-neg anaerobes
- clav acid - some resistance to beta-lactam-based antibiotics like amox due to bacteria producing a beta-lactamase whydrolysing the lactam ring. this acid binds and inactivates the enzyme doing this
When amoxicillin and clavulanic acid are combined, known as …
- augmentin
or - Co-amoxiclav
Process of antibiotic sensitivity testing
- infecting microorganism is isolated and pure culture is grown in broth to provide sufficient for testing
- approx 100 microlitres spread evenly on agar with specific agar
- suitable range of antibiotics selected and ring placed on agar. incubated overnight - dense bacterial produces ‘lawn’ of bacteria
- during incubation, antibiotic diffuses from ring and if bacteria is sensitive inhibits growth
- metronidazole and others are tested seperately in anaerobic conditions
- clinician reviews choice of antibiotic
Explain mastrings
- the ring used for antibiotic sensitivity testings
- available with predetermined range of antibiotics or can be consumed
- has chloramphenicol, erythromycin, fusidic acid, methicillin, novobiocin, penicillin G, streptomycin, tetracycline
Do mastrings have the same conc of each antibiotic on them?
- amount of each is carefully picked differently
- to reflect amount expected to be achieved at site of action in body
What is a breakout colony in antibiotic sensitivity testing?
- sometimes a few bacteria in sample grow and produce colonies within general area of inhibition
- less dense than the lawn
Define MIC’
- miminum inhibitory concentration
- lowest conc of antibiotic that inhibits growth of test bacteria
- inevitable that some bacteria will be killed but others will survive and grow when sample is cultured on drug-free agar
What is MBC?
- minimum bacteriocidal concentration
- higher than MIC and kills all microorganisms
