47. Infection Control Practical Flashcards
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
MIC and MBC not a part of routine antibiotic sensitivity testing but it’s useful. Why?
- measures antibiotic’s efficacy
- provides essential info regarding delivery of drug
- helpful in determining appearance of resistance
Define ‘antimicrobial’
- includes agents active against range of microorganisms like bacteria, fungi, viruses
The beta lactam ring is absent in what?
- aminopenicillins like amoxicillin
What antibiotic would you use to treat angular cheilitis in a patient that doesn’t wear a denture?
- fusidic acid
What antibiotic should you avoid prescribing to children and pregnant women?
tetracycline
Which method of horizontal gene transfer involves bacteria taking up DNA from local environment?
transformation
Currently, over … people die every year from antimicrobial resistant infections
700,000
Define bactericidal agent
a chemical agent or drug that kills bacteria
Define ‘bacteriostatic agent’
a chemical agent or drug that inhibits growth of bacteria
What is intrinsic resistance?
an innate property of bacterium seen in all strains
Define ‘acquired resistance’
drug resistance is selected for by antibiotic use
Define ‘cross resistance’
resistance to one antibiotic leads to resistance to another
Define ‘multi-resistance’
resistance to several antibiotics via independent mechanisms
Define ‘mutation’
an inheritable change in character of gene - change in sequence of base pairs in DNA molecule
Define ‘selective growth medium’
culture medium that allows certain organism or group of organisms to grow while inhibiting growth of all other organisms
No new classes of antibiotic have been developed since …
1980
The first 3 stages of drug development investigate what?
- dose safety levels
- effectiveness
- commercial value
- side effects
What organisation regulate medicines in UK?
MHRA
- medicines and healthcare products regulatory agency
Clinical trials usually have … phases
4
Drug development can take up to … years and cost … dollars
- 18
- 1 billion
Which antibiotic has a beta lactam ring?
penicillin
Which drug interferes with the process of DNA production in the virus causing herpes labialis?
acyclovir
Aminoglycosides interfere with what bacterial cell process?
protein synthesis
Clavulanic acid binds to and inactivates what?
beta-lactamase enzymes
Nystatin treats infections caused by what microorganisms?
fungi
Which toothpaste ingredient out of chlorhexidine, essential oils, glycerol, stannous fluoride and ticlosan is NOT antibacterial?
glycerol
Which of these is NOT true of chlorhexidine?
- disrupts bacterial cell membranes
- has high substantivity
- shown to be effective in inhibiting plaque growth
- effective in treating periodontal disease
- often found in mouthwash at conc of 0.2%
it is NOT effective in treating periodontal disease
Why is MRSA screened for in the groin?
- sweaty environment
- so salty
Which of these are spore forming?
- clostridium species
- bacillus species
- mycobacterium species
- fusobacterium species
- staphylococcal species
- clostridium
- bacillus
Which of these are antimicrobial?
- iodine
- cetylpyridium chloride
- triclosan
- chlorhexidine
all of the above
Oseltamivir is an anti-viral used to treat what infection?
influenza
What is the target of tetracycline antibiotic?
- protein synthesis
- interferes with function of 30S ribosome subunit
Highly active antiretroviral therapy is used as a combination therapy to treat what?
HIV
Which of these is NOT true about metronidazole?
- can be used in management of severe pericoronitis
- active against anaerobic bacteria
- imidazole antibiotic
- possesses beta-lactam ring
it does NOT possess a beta-lactam ring
How do polyenes combat fungi?
disrupt fungal cell membranes
What do azoles do?
inhibit ergosterol synthesis
What do 5-flucytosine do?
inhibit DNA and protein synthesis in fungi
What do echinocandins do in fungi?
inhibit beta-1,3-D-glucan synthesis
How to achieve pasteurisation?
heat fluid to 66 degrees for 30 mins
Horizontal gene transfer of antibiotic resistance genes via pili directly connecting bacteria is called what?
conjugation
Difference between sterilisation and disinfection
- steri kills all microorganisms including spores
- dis kills or removes pathogenic organisms excluding bacterial spores so they pose no threat of infection
