Microbiolgy Flashcards
which antibiotics are beta lactams (inhibit cell wall formation)?
penicillins
cephalosporins
which antibiotics are bacteriostatic (inhibit protein synthesis)?
aminoglycosides (cause misreading of mRNA)
chloramphenicol
macrolides (e.g. erythromycin)
tetracyclines
fusidic acid
what antibiotics inhibit DNA synthesis?
quinolones (e.g. ciprofloxacin)
metronidazole
sulphonamides
trimethoprim
which antibiotics inhibit RNA synthesis?
rifampicin
what is the mechanism of resistance for penicillin?
Bacterial penicillinase (β-lactamase) cleaves β-lactam ring
what is mechanism of resistance for cephalosporins?
Changes to penicillin-binding-proteins (PBPs), which are types of transpeptidases
what is the mechanism of resistance for macrolides?
Post-transcriptional methylation of the 23S bacterial ribosomal RNA
what is the mechanism of resistance for tetracyclines?
Increased efflux of the bacteria by plasmid-encoded transport pumps, ribosomal protection
what is the mechanism of resistance for sulfonamides
Bacteria increase synthesis of PABA, mutation to gene encoding dihydropteroate synthetase
what is the mechanism of resistance for vancomycin
Alteration to the terminal amino acid residues of the NAM/NAG-peptide subunits (normally D-alanyl-D-alanine) to which the antibiotic binds
Rifampicin
Mutations altering residues of the rifampicin binding site on RNA polymerase
which streptococci have alpha haemolysis? (partial haemolysis)
pneumococcus
streptococcus viridans
which streptococci do beta haemolysis (complete haemolysis)?
Group A - strep pyogenes
Group B - agalactiae
Group D - enterococcus
compare how beta haemolysis would look like to alpha haemolysis in a blood agar tray?
beta will be very yellow and large area
alpha will be smaller area and darker
what is the main route of infection for strep viridans?
GI tract
what criteria is used to asses endocarditis?
DUKE’s criteria
what is FEVER PAIN score used to assess?
Strep Pharyngitis
what is centor criteria used for ?
group A strep
strep pharyngitis
what does enterococcus faecalis cause on blood agar ?
no haemolysis ( gamma haemolytic)
Which of these is not included in the list of ‘typical organisms’ in the major criteria for diagnosing endocarditis
(2 separate positive blood cultures in the absence of alternative source)
Select one:
Staphylococcus aureus
Enterococcus faecalis
Viridans streptococci
Escherichia species
HACEK group organisms
Escherichia species
what does the QSOFA markings indicate?
sepsis
altered mental state
resp rate <30
systolic BP <100
what bacteria is Proton pump inhibitors a risk factor for?
Clostridium difficile
how do you test for clostridium difficile?
Clostridium difficile toxin (CDT) in the stool
what are the risk factors of C.difficile infection?
Antibiotics within the preceding 3 months
Proton pump inhibitors
Prolonged hospitalisation
Immunosuppression
what is the clinical presentation of Haemolytic uraemic syndrome?
acute kidney injury
microangiopathic haemolytic anaemia
thrombocytopenia
what two types of haemolytic uraemic syndrome are there?
typical HUS - secondary caused:
Shiga toxin-producing Escherichia coli (STEC) 0157:H7
pneumococcal infection
HIV
rare: systemic lupus erythematosus, drugs, cancer
atypical HUS (primary caused:
complement dysregulation
how do you diagnose HUS?
full blood count: anaemia, thrombocytopaenia, fragmented blood film
U&E: acute kidney injury
stool culture
looking for evidence of STEC infection
PCR for Shiga toxins
how do you manage HUS?
no antibiotics!
supportive: fluids, blood transfusion and dialysis
what drugs are used in anaerobes only?
- metronidazole
what drugs are used in both anaerobes and aerobes?
- penicillin
- amoxicillin
- clindamycin
- co trimoxazole
- moxiflacin
- ceftriaxone
- cefepime
- tigecylcine
- Piperacillin – tazobactam
what drugs are used in gram positive only?
flucloxacillin
vancomycin
what drugs are used in gram negative only?
azithromycin
erythromycin
give examples of penicillins.
- penicillin
- amoxicillin
- flucloxacillin
- Piperacillin-tazobactam
give examples of sulfonamides.
co-trimoxazole
trimethoprim
give examples of aminoglycosides.
gentamicin
tobramycin
give examples of fluoroquinolones? (quinolones)
moxifloxacin
Ciprofloxacin
Aztreonam
levofloxacin
give examples of CEPHALOSPORINS.
cephazoline
cefuroxime
ceftriaxone
what class is vancomycin part of?
glycopeptides
what are the 4c antibiotics?
Clindamycin
Levofloxacin (fluroquinolones)
Ceftazidime (cephalosporins)
Co-amoxiclav
