Microbiology Compilation Flashcards
commensals of the mouth
- strep viridans
- candida
- neisseria
- anaerobes
bowel commensals
- Enterococci
- Anaerobes: clostridium and bacteroides
- Coliforms
gamma haemolysis
alpha haemolysis
name 4 methods for detecting bacteria
- chromogenic media
- MALDI-TOF
- PCR
- whole genome sequencing
non/lactose fermenter enterobacteriaceae
- Lactose fermenters: E. coli, Klebsiella, Enterobacter
- Non-lactose fermenters: Salmonella, Proteus
what are 3 encapsulated bacteria
- h influenza b
- pneumococcal
- neisseria meningitidis
hyposplenism makes host susceptible to infections from encapsualted organisms
name 2 spirochaetes
treponema pallidum
borrelia burgodorferi (lyme disease)
what are most false blood cultures due to
contamination with skin commensals due to poor technique
how is influenza confirmed
nasopahryngeal swab and doing PCR
when is CSF examined
- when there is suspicion of possible meningitis - via lumbar puncture
- wouldnt normally do this in the clinical setting
- check child with clotting screen first
indications for urine dipstick
- avoid in the elderly
- avoid in catheterized patients as it is often colonised
- not the test of choice in sepsis
indication for urine catheter samples
- do not send unless it is considered to be a source of infection and the patient appears infected
indications for urine culture
- complicated infection
- male infection
- recurrent UTI in female
what is the aim of antimicrobial stewardship
optimal selection, dosage, and duration of treatment - prudent prescribing
and explaining, reassuring and educating the large group of patients who dont need ABx
4Ds of antimicrobial therapy
what does de-escalation involve
- moving from IV to oral - IV therapy must be reviewed every 12-24 hours
- moving to a narrower spectrum
- watch microbiology results
indications for IV route
- sepsis
- oral compromised
- post surgery
- ostemyelitis
- febrile with neutropenia or IS
IV just gives faster systemic absorption
define pharmacodynamics
the relationship between infection outcome and drug outcomes
define pharmacokinetics
effect of body’s processes on the drug
minimum inhibitory concentration
- a measure of the potency of the drug against a given pathogen
- the concentration required to kill 99.9% of organisms within 18-24 hours (tube/well containing pathogen visually clear)
what type of dosing gives optimal outcomes
- high dosages for shorter duration
- longer increases risk for C diff and resistance
- keeping to recommended dose interval is important in effectiveness
what can too high dosing cause
harm
resistance
outline the start SMART then FOCUS diagram
action of beta lactams
inhibit cell wall biosynthesis by binding to the enzymes that cross link peptidoglycans
are beta lactams bacteriostatic or cidal
bacteriocidal
what is penicillin allergy due to
degradation product of beta lactams, true allergy exists in <0.05%
aztreonam
- beta lactam
- can be used in penicillin type 1 allergy
- active against Gram negative bacteria
- used in Gentamicin resistance
how do bacteria develop resistance to beta lactams
synthesise a beta lactamase, this breaks open the beta lactam ring and inactivates the drug
eg MRSA
how can beta lactam resistance be overcome
ABx are given with a beta lactamase eg clavulanic acid
what are ESBL susceptible to
carbapenems
how can resistance be acquried to an ABx
- Organism specific rate of mutation, some are hypermutators
- Random mutations that can be induced by antibiotics
- Bacterial burden – mutation is more likely if there is a higher bacterial load
- Efflux pumps
what sites are harder for ABx to get to
in general, tight junctions eg CNS, eyes, prostate
gentamicin toxicity
kidneys and CNVIII - dizziness and deafness
- contraindicated in renal problems - can only be given for a max of 24 hours
how long in total can gentamicin be given for
72 hours
which ABx can cause tendonitis
quinolones - achilles and extensor knee mechanism?
which ABx have anti toxin effects
clindamycin and linezolid
common adverse effects of ABx
nausea and vomiting
C Diff causing ABx
- all ABx carry some risk
- 4 C’s - Ciprofloxacin (fluoroquinolones), Clindamycin, Cephalosporins (Ceftriaxone) and Co-amoxiclav
- remember levofloxacin
- kill off the normal gut bacteria and allow the overgrowth of C diff
- PPIs - reduce the acid produced in the stomach which is normally the first line of defence
does treatment time influence the risk of C diff
yes - longer treatment
also hospitalization time
IC
how long after ABx may C diff occur
up to 12 weeks
C diff infection
- c diff are gram positive, spore forming, anaerobic rods that produce toxins A and B
- toxin A in an enterotoxin and toxin B causes bloody diarrhoea
- these cause an inflammatory response in the large intestine that leads to increased vascular permeability and pseudomembrane formation
clinical features of C diff infection
range from mild diarrhoea to profuse, watery, haemorrhagic colitis
abdominal pain and vomiting
who tends to get C diff infections
elderly women
investigation of C diff
stool toxin
management of C diff infection
mild: oral metronidazole
severe: oral vancomycin ± IV meronidazole
coverage of MRSA
vancomycin - gram positive
