Lecture 9: Antibiotics Flashcards
define an antibiotic
a chemical compound made by another microorganism which inhibits or kills bacteria
the majority of antibiotics are derived from which bacterial species?
streptomyces
what does a bacteriostatic agent do?
restricts the growth and reproduction of bacteria but it is the patient’s own immune system which kills off the bacteria and leads to recovery from the infection
what does a bactericidal agent do?
causes bacterial cell death
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examples of bactericidal antibiotics
- penicillin
- gentamicin
- vancomycin
- ciprofloxacin
- metronidazole
examples of bacteriostatic antibiotics
- doxycyline
- calrithromycin
- azithromycin
- linezolid
which antibiotics inhibit cell wall synthesis?
Beta-lactams:
- penicillins
- cephalosporins
- carbapenems
Glycopeptides:
- vancomycin
which antibiotics inhibit protein synthesis?
- gentamicin
- doxycycline
- clarithromycin
- erythromycin
- clindamycin
- chloramphenicol
- linezolid
which antibiotics inhibit DNA synthesis?
- metronidazole
- fluoroquinolones
which antibiotics inhibit folic acid synthesis?
trimethoprim
co-trimoxazole
how do beta-lactams work?
bind to penicillin binding proteins (PBP) in the cell wall or cell cytoplasm, thereby inhibiting cell wall formation
- inhibited by beta lactamases
cephalosporins all cover
Group A, B, C streptococci
Viridans group Streptococci
E.coli
Klebsiella
Proteus mirabilis
cephalosporins are LAME because they dont cover
Listeria
Atypicals
MRSA (except 5G)
Enterococcus
when is meropenem (a carbapenem) indicated?
- active against gram positive, gram negative and pseudomonas
- severe infections: unresponsive to other abx and haematology patients
- lung infections in cystic fibrosis patients.
beta lactam adverse reactions
- mild (5%): rash, fever
- severe (0.05%): anaphylaxis
beta-lactams drug interactions
- carbapenems: valproate and probenecid
- all beta-lactams: typhoid vaccine
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which antibiotic is exclusively used to treat lower urinary tract infections?
nitrofurantoin
gram-positive cocci include
staphylococcus
streptococcus
enterococcus
gram-positive rods include
corny mike’s list of basic cars
corneybacteria
mycobacteria
listeria
bacillus
nocardia
gram-positive anaerobes can be remembered with the CLAP mnemonic:
clostridium
lactobacillus
actinomyces
propionibacterium
list some common gram-negative bacteria
- Neisseria meningitidis
- Neisseria gonorrhoea
- Haemophilia influenza
- E.coli
- Klebsiella
- Pseudomonas aeruginosa
- Moraxella catarrhalis
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the five atypical bacteria causing atypical pneumonia can be remembered with the ‘legions of psitacci MCQs’ mnemonic
legionella pneumophilia
chlamydia psittaci
Mycoplasma pneumoniae
Chlamydophilia pneumoniae
Q fever (coxiella burnetti)
antibiotics used to treat MRSA include:
doxycycline
clindamycin
vancomycin
teicoplanin
linezolid
when is vancomycin used?
- MRSA
- 1st line for gram-positive infections in individuals with penicillin allergy: skin and soft tissue infections, streptococcus meningitis, infective endocarditis
- C.diff when given orally
vancomycin side-effects
red man syndrome:
- flushing
- erythema
- pruritus
- affecting upper body, neck and face > lower body
- myalgia, dyspnea, hypotension
aminoglycosides toxicity e.g. gentamycin, streptomycin
- nephrotoxicity
- ototoxicity/vestibulotoxicity
- neuromuscular blockade
tetracycline class side effects
e.g. doxycycline
- photosensitivity
- gastritis, oesophageal ulceration
- contraindicated in pregnancy
- can cause permanent tooth staining in children < 8
when is erythromycin indicated?
- skin & soft tissue infections
- community acquired pneumonia
when is clarithromycin indicated?
- skin & soft tissue infections
- community acquired pneumonia
- atypical pneumonia: listeria, mycoplasma, psitcossis
- helicobacter pylori
- toxoplasma gondii
when is azithromycin indicated?
- typhoid fever: salmonella typhi and paratyphi
- STI: gonorhoea, chlamydia
macrolides side effects
the mycins except gentamicin
- jaundice
- ototoxicity
- prolonged QT syndrome
- GI disturbance
- avoid clarithromycin and azithromycin in pregnancy unless benefit outweighs risk
when is metronidazole indicated?
bacteria- Clostridium, helicobacter
parasitic- giardia, entameoba
when is trimethoprim used?
UTIs
when is co-trimoxazole used?
- pneumocystis jiroveci pneumonia
- toxoplasmosis
- multi drug resistant organisms e.g. mycobacterium, stenotrophomonas
what is the minimum inhibitory concentration (MIC)?
lowest concentration which prevents visible growth of a bacterium or bacteria
doxycycline spectrum and usage
broad-spectrum
- soft tissue and skin infections
- CAP + atypicals
- genito-urinary infection
- rickettsia
- malaria prophylaxis and treatment
- bone and joint: septic arthritis and osteomyelitis
