Antibiotics Flashcards
What does Borelia spp cause
Lyme disease
What causes typhoid
Salmonella typhi
What causes syphillis
Treponema pallidum
What is bronchiectasis
permanent enlargement of parts of the airways of the lung),
What is minimum inhib concentration
the lowest conc of the antibiotic being tested that inhibits growth of the organism in a broth
What is min bactericidal conc
conc: lowest concentration that kills the organism
What drugs are beta lactams
Penicillin, cephalosporin and carbapenem
What is the mechanism of action of beta lactams
Beta lactams act on the cell wall of the bacteria by binding to penicillin binding proteins in the cell membrane. These proteins help synthesise peptidoglycan in the cell wall. In gram negative, the beta lactam must also penetrate outer layer
What is used for chest infection and cellulitis
Penicillin G (pneumococcus)
What is used for s. aureus infection
Flucloaxicllin
When are carbapenems used
Not used unless extremely resistant. Ertrapenem and meropenem.
What are examples of macrolides
erythromycin, clarithromycin, azithromycin (go to for staphylococci and streptococci if patient allergic to penicillin and atypical pneumonia)
What is erthyromycin
Erythromycin (IV and PO): Bacteriostatic macrolide antibiotic interferes with protein synthesis by ribosomal binding
What are azithromycin and clarithromycin
Azithromycin (PO) and clarithromycin (IV, PO) are new macrolides with longer half live and fewer side effects
What are examples of tetracyclines
Oxytetracycline, doxycline, tigecycline
What are oxytetracycline and doxycline
are bacteriostatic and inhibit binding of tRNA to the ribosome. Broad spectrum but resistance frequent. Use for respiratory tract and soft tissue infection. Useful in penicillin-allergic patients who suffer side effects with macrolides.
What is tigecyclin
a recent and potent broad spectrum agent with activity against Gram positive, gram negatives and anaerobes
What are examples of glycopeptides
Vancomycin and teicomycin
What is the mechanism of action of glycopeptides
act on bacterial cell wall, only against gram positive bacteria and mainly used for treatment of MRSA and coagulase negative staphylococcus infection.
What are quinolones
Ciprofloxacin inhibit DNA gyrase, the enzyme that supercoils DNA within bacteria. The organism is disrupted by the unwound DNA. Generally used for gram negative bacteria; activity against gram positive bacteria is weaker
What is the mechanism for trimeoprim and co-trimoxazole
agents block the synthesis of bacterial nucleotides in the pathway of folic acid/nucleotide synthesis. Active against gram negative and gram positive bacteria.
What is trimethoprim used for
UTI
What is co-trimoxazole used for
used for treatment and prophylaxis of Pneumocystis jirovecii pneumonia, Stenotrophomonas maltophilia infection and nocardiosis
What is metronidazole
affects nucleic acid function by breaking DNA strands. Active
against virtually all anaerobes, amoebae and Trichomonas vaginalis.
What is linezolid
an oxazolidinone. Active only against Gram-positive bacteria including
MRSA and glycopeptide-resistant enterococci.
What is chloramphenicol
Owing to bone marrow toxicity reserved for occasional
therapy of meningitis and topical treatment of eye infections.
What is rifampicin
Highly active against Gram-positives. Prosthetic valve endocarditis and
other prosthesis infections; part of 1st line TB regimen.
What is fosfomycin
increasingly used for multi-resistant Gram-negative bacterial infections.
What is fidaxomicin
only for selected cases of severe or recurrent Clostridium difficile diarrhoea
Cases. No other indication.
What is colistin
dispupts bacterial membrane. Reserved for multipl- or pan-resistant GramNegative
infections. No other frequent indication.
What is daptomycin
a lipopeptide. Similar activities to glycopeptides: active only against
Gram-positive bacteria.
What is fusidic acid
staphylococcal infections only. Topical. If systemic: always use with
a second anti-staph agent.
Why is penicillin not active against pseudomonas aeruginosa or escherichia coli?
Pseudomonas can mutate porins to prevent some anti-pseudomonal abx from penetrating the bacterial cell.
Why is penicillin not active against strep pneumoniae
penicillin resistance due to altered PBPs. MRSA produces a new PBP that is not inhbitied by methicillin (flucloaxacillin).
What’s the treatment for TB
Rifampicin 6-12 months
Isoniazid 6-12 months
Pyrazinamide 2 months (increases killing of macrophage, can’t always predict mono-resistance)
Ethambutol 1-2 months
