Introduction to the major groups of antimicrobials Flashcards
What are examples of beta-lactams?
penicillins, cephalosporins, carbapenems
What is an example of a quinolone?
ciprofloxacin
What is an example of a macrolide?
erythromycin
What is an example of an aminoglycoside?
gentamicin
What is an example of a glycopeptide?
vancomycin
What is an example of a tetracycline?
oxytetracycline
What are examples of folate antagonist?
trimethoprim / sulphonamide
What is an example of an imidazole?
metronidazole
What are the different types of penicillins?
natural = penicillin G/V=> s pnuemoniae
semi-synthetics
- flucloxacillin => staph aureus (not MRSA)
- Piperacillin + tazobactam (tazocin) => pseudomonas, enterobacteriaceae, s. aureus, anaerobes
- ampicillin, amoxicillin (non-beta lactamase producing enterobacteriaceae, h.influenzae)
- amoxicillin + clavulanic acid (co-amoxiclav) => beta-lactamase producing haemophilus influenzae, s.pneumoniae, s.aureus anaerobes
What are the different types of cephalosporins?
1st gen = cefalexin, cefradine
2nd gen = cefuroxime
3rd gen = cefotaxime, ceftazidine
4th gen = cefpirome
What organisms are resistant to cephalosporins?
ESBL producing organisms
What are some examples of carbapenems and what are they good against?
imipenem
meropenem
ertapenem
generally stable to most GNB beta-lactamases - rare resistance but it is increasing particularly against hospital acinetobacter/pseudomonas and carbapenemase producing klebsiella/e.coli
What are carbepenems not effective against?
no against against MRSA/VRE but covers lots of other common pathogens e.g. s pneumoniae and group A strept
What is avibactam ?
broader spectrum of activity than currently available beta lactamase inhibitors
What is class A of the ambler DNA sequence classification of beta-lactamases?
active site = serine selected examples: - staphylococcal penicillinase - broad spectrum penicilinaes - serine carbapenemases
What is class B of the ambler DNA sequence classification of beta-lactamases?
active site: zinc
selected examples:
- metallo-carbapenemases
What is class C of the ambler DNA sequence classification of beta-lactamases?
active site serine
selected examples:
- chromosomal cephalosporinases AmpC plasmidic
What is class D of the ambler DNA sequence classification of beta-lactamases?
active site = serine
selected examples:
- oxacillinases broad spectrum not inhibited by clav/taz
- OXA-48 carbapenemase
What is penicillin hypersensitivity?
true life threatening is v. rare but dramatic - angioneurotic oedema
10% patients of patients ask will say they are allergic - mainly due to skin rash
skin testing can be used to identify these patients
patients on ampicillin/amoxicillin can get a maculopapular rash ++++glandular fever
can use carbapenems/aztreonam
What are the different types of allergic reaction people could have against penicillin?
immunoglobulin E mediated reaction (immediate) = urticaria, angioedema, wheezing, SOB, anaphylaxis
Non-IgE reaction (delayed) = . exfoliative dermatitis, steven johnsons syndrome, serum sickness, haemolytic anaemia, maculopapular rash etc
What are glycopeptides important for treating?
vancomycin and teicoplanin
- important for MRSA and resistant enterococci
- c diff diarrhoea - used for severe disease orally 125mg QDS as not absorbed
- potentially nephrotoxic (IV only)
What are quinolones important against?
ciprofloxacin, levofloxacin, moxifloxacin
active against gram ve and -ve but NOT MRSA streptococci
useful for UTIs(resistant bacteria)
resistance is rising
pseudomonas - resistance can emerge by mutation, safe but c.diff issues
How do aminoglycosides work?
bind to 30S subunit of mRNA
How do macrolides work?
prevent binding of the 50S subunit to mRNA
How do tetracyclines work?
prevent transport of amino acids into ribosome by tRNA
How does chloramphenicol work?
prevents attachment of amino acids to the polypeptide chain
What are macrolides used for?
erythromycin, clarithromycin
active against s.pneumoniae (+resistance), beta-haemolytic strepts, s.aureus, h influenzae, legionella, mycoplasma
not active against:
- enterobacteriaceae, enterococci, or pseudomonas
What are aminoglycosides effective against?
gentamicin, tobramycin, amikacin
- relatively nephrotoxic - only given od only iv/im
active against pseudomonas, GNBs including some nosocomial staph aureus
not active against streptococci, anaerobes
What are tetracyclines used for?
oxytetracycline, minocycline (better absorbed but expensive), tigecycline (active against MRSA and acinetobacter)
do not give in pregnancy - children teeth
uses: chlamydiae, COPD, Acne
poorly absorbed with antacids
What are some other antibacterial agents “orphans”?
chloramphenicol fusidic acid linezolid mupirocin nitrofurantoin daptomycin fidaxomicin metronidazole
What is chloramphenicol used for?
rarely used in UK
- good against gram +ves
What is fusidic acid used for?
related to steroid hormones - specific activity against staphylococci
What is linezolid used for?
valuable anti-staphylococcal agent - good for MRSA and VRE - oral and IV
- can be toxic over 2 weeks - monitor WBC
What is mupirocin used for?
topical nasal decolonisation of MRSA carriage
What is daptomycin used for?
potent iV anti-MRSA agent v cidal good in endocarditis and foreign body infections, increase CPK sometimes
What is nitrofurantoin used for?
lower UTI - now first in line
What is fidaxomicin used for?
macrocyclic alternative to metronidazole/vancomycin for c. diff - £1300/course
What are sulphomides used against?
widespread resistance - only used against stenotrophomonas and as co-trimoxazole for pneumocystitis jirovecii
What is trimethoprim used for?
cheap, oral, heavily used for UTI
resistance 20-30%
What is co-trimoxazole used for?
trimethoprim combined with sulphamethoxazole
no advantage in UTI
What is metronidazole used for?
active agent almost all anaerobes
long term use => peripheral neuropathy
antabuse effect with alcohol
