C:\documents and settings\francis\my documents\the f-files\postgraduate medicine\otolaryngology\ent notes\ch 5 - microbiology,

ANTIMICROBIAL AGENTS
Penicillins
-Strep pyogenes (B-hemolytic group A) -inactivated by penicillinase (B-lactamase): -S. pneumoniae: becoming increasingly resistant to penicillins and cephalosporins due to protein -methicillin, oxacillin, cloxacillin, dicloxacillin, nafcillin -extend activity spectrum to gram-negative organisms: -resistance in B-lactamase producing organism -clavulanate (amoxil) and sulbactam (ampicillin) -for management of staphylococci, H. influenzae, M. catarrhalis, anaerobic organisms Cephalosporins
-commonly and safely used by pts with history of penicillin rashes highly effective against gram-positive organisms such as streptococci, pneumococci except for penicillin-resistant strains, and staphylococci except MRSA -highly active against gram-positive cocci -H. influenzae and M. catarrhalis including pen-resistant strains -penetrates blood-brain barrier fairly well -cefixime:-oral agent highly effective against H. influenzae and M. catarrhalis -parenteral agent effective against H. influenzae, M. catarrhalis, S. pneumoniae, N. -first choice for treating patients with intracranial and orbital complications of acute -usually less active against gram-positive bacteria -anaerobic bacteria are also relatively resistant A n ti b i o t i c s
-active against S. pyogenes, most S. pneumoniae organisms, S. aureus, H. influenzae, B. fragilis and most anaerobic organisms and the coliforms including P. aeruginosa -used as single agent against infection by unidentified organisms but CSF penetration is not assured Macrolides
-effective for respiratory infections d/t streptococci, most pneumococci, mycoplasmata and chlamydiae, legionellosis, diptheria, and pertussis -extend antimicrobial activity to include H. influenzae and M. catarrhalis Clindamycin
-highly active against gram-positive cocci, including many but not all strains of penicillin-resistant -effective against S. aureus and anaerobic infections of the aerodigestive tract (B. fragilis) Tetracyclines
-effective against Mycoplasma, Chlamydia, and Legionella -stain enamel in forming teeth: avoided in children younger than 10 and pregnant women Quinolones, Fluoroquinolones
-potential for cartilage damage and arthropathy in children -levofloxacin, gatifloxacin, gemifloxacin: -for respiratory and pharyngeal infections -effective against B-hemolytic S. pyogenes, S. pneumoniae, S. aureus, H. influenzae, M. catarrhalis , Mycoplasma, Chlamydia, Legionella, Bordetella pertussis Vancomycin
-highly active against gram-positive cocci including MRSA, penicillin-resistant strains of pneumococci, -high concentrations in patients with renal impairment can cause ototoxicity Metronidazole
-highly active against anaerobic bacteria -all aerobic bacteria are resistant to this agent Aminoglycosides
-used against P. aeruginosa and other hospital-acquired infections m a n a g e m e nt o f H . i n f l u e n z a e b u t n o t o f p n e u TREATMENT STRATEGIES
Otitis Media
-S. pneumoniae, H. influenzae, M. catarrhalis -first line:-amoxil:-most strains of S. pneumoniae -H. influenzae (20% resistant) and M. catarrhalis (80% resistant) -high dose penicillin for penicillin resistant organisms -vancomycin, levofloxacin, gatifloxacin, moxifloxacin, gemifloxacin Sinusitis-acute: -same bacteria as in OM
-pneumococcal infection suspected Rx ceftriaxone, cefuroxime or trovafloxacin -chronic:-anaerobes and S. aureus Pharyngitis
-also N. gonorrhoeae, Mycoplasma, Chlamydia and H. influenzae Tonsillitis-frequently caused by S. pyogenes
Mastoiditis
-pneumococci and H. influenzae tend to intracranial extension Rx ceftriaxone -chronic suppurative otomastoiditis including cholesteatoma: S. aureus, Proteus, B. fragilis and other Suppurative Otitis
-polymyxin for pseudomonal infection and neomycin for S. aureus, Proteus organisms and others

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