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Introduction to Antibiotics (Quinolones (CIPROFLOXACIN, LEVOFLOXACIN, Oral…
Introduction to Antibiotics
Antibiotic
- Natural, synthetic or semisynthetic. Naturally occurring agent which is designed to kill or inhibit microbe
Antimicrobrial agent
- Any drug which inhibits or kills a bacterium, fungus or virus. So they are antibacterial, antifungal and antiviral agents.
Use of Antibiotics
: Treatment (Empiric therapy and Targeted therapy) and Prevention (Prophylaxis)
Antibiotic Spectrum
- Narrow (Penicillin G against gram positive and some gram negative) and Broad (Pipercallin-tazobactam for some gram positive, some gram negative, pseudomonas and anaerobic bacteria).
Antimicrobial Activity
: Bacteriostatic (inhibits bacterial growth eventually leading to bacterial death) and Bactericidal (kills susceptible bacteria which is useful for immunosuppressed patients and for infections such as meningitis and endocarditis
Susceptibility Testing: Disk Diffusion, Minimum Inhibitory Concentration and Genotypic Methods
B-lactams
Penicillins
Standard Penicillin
- Benzylpenicillin. Narrow spectrum for gram postive cocci. Used for the treatment of infections such as endocarditis, meningitis and cellulitis
Anti-staphylcocci-
Flucloxacillin- A narrow spectrum antibiotic which is NOT inactivated by staphylococcal beta-lactamase. Susceptible to S.aureus infections
Aminopencillin
- Amoxicillin, Ampicillin. A broad spectrum antibiotic used for the treatment of UTIs and resp tract infections. For gram negative cocci
Anti-pseudomonal
- Piperacallin
Some bacteria produce beta-lactamase which breaks down the beta lactam ring. So the beta lactam antibiotic should be give with a beta lactamase inhibitor. E.g-
Amoxicillin and Clavulunate= Co-amoxiclav
and
Pipercallin and Tazobactam= Piptazobactam
Cephalosporins
1st- Anti-positive activity, orally active and used to treat resp tract infections and UTIs.
CEFACLOR
2nd- Anti-positive and anti-negative activity. Oral and IV. For respiratory infections and surgical prophylaxis.
CEFUROXIME
3rd- Anti-gram negative activity and less staphlycoccal activity with some streptococcal activity. IV. Meningitis.
CEFOTAXIME
Monobactams
Active against gram negative organisms only and no activity against gram positive organisms or anaerobes. Suitable for patients with penicillin allergy. E.g-
Aztreonam
Carbapenems
Broad spectrum antibiotic against gram positive and gram negative organisms. Stable to beta-lactamases. Cross reactivity in penicillin allergy.
MEROPENEM
,
ERTAPENEM
Glycopeptides
Narrow spectrum
Gram positive organisms
Treatment for MRSA (IV), C.diff (Oral)
VANCOMYCIN
and
TEICOPLANIN
Aminoglycosides
Gram negative bacilli, S.aureus, Mycobacteria, Brucells (but inactive against anaerobes)
To treat intra-abdominal infections and infective endocarditis
GENTAMICIN
Nephrotoxicity and Ototoxicity
Macrolides
Oral or IV
ERTHROMYCIN, CLARITHROMYCIN, AZITHROMYCIN
Resp infections for which beta-lactams are ineffective due to the absence of a cell wall. Treatment for atypical pneumonia
Pseudomonas is always resistant to macrolides
Quinolones
CIPROFLOXACIN, LEVOFLOXACIN
Oral
Gram negative bacilli
UTI and intra-abdominal infections
S.E- Neurological and caution with C.diff
Tetracyclines
Infections caused by Chlamdyia, Rickettesia, Coxiella, Mycoplasma
Growing teeth becomes stained
DOXYCYCLINE
METRONIDAZOLE
Anti-anerobic and anti-protozoal
Intra-abdominal infections and used in combination with prophylaxis in bowel surgery
Inactive against staphylcocci and aerobic GNBs such as E.coli