Antibiotic Therapy* Most common cause of pyelonephritis is E. coli, most common cause of osteomyelitis is S. aureus.* So what antibiotics go along with staph/strep, gram negative rods, and anaerobes?* If you do PCR resting on Egyptian mummies from 5 thousand years ago, you will find there was beta-lactamase in the staphylococcus.* Ampicillin, penicillin, amoxicillin alone is good for streptococcus, but not for staphylococcus.* Antibiotics for staphylococcus and streptococcus are oxacillin, cloxacillin, dicloxacillin, nafcillin (not methicillin).* With methicillin-sensitive staphylococcus, what do you use? Not methicillin. Use ox, clox, diclox, naf. Why dont we use methicillin? Because it causes interstitial nephritis.* Another alternative for staphylococcus and streptococcus (e.g. penicillin allergy) is a beta-lactam drug, first generation cephalosporins like cephalexin, cephadroxil, cefazolin. 5% cross-reaction with penicillins at most and almost never anaphylaxis, so dont worry if the allergy is a little rash.* What if patient says they have a penicillin allergy, that causes a little rash, and hypotension, and stridor, and laryngeal edema so they had to get intubated, then got IV steroids, then dopamine drip in the ICU. For life threatening penicillin allergies, then we should avoid all the beta-lactam antibiotics.* Macrolides: erythromycin, azithromycin, clarithromycin. Macrolides with clindamycin will cover staph/strep, but are not first choice, choice for life-threatening penicillin allergy. Vancomycin works, but should be reserved for methicillin-resistant staph aureus (MRSA). Vancomycin not superior in efficacy to ox/clox/diclox/naf, just superior in its resistance pattern.* Gram negative rods include E. coli, klebsiella, proteus, enterobacter, citrobacter, pseudomonas.* Antibiotics for Gram-negative rods are aztreonam, aminoglycosides (gentamycin, streptomycin, tobramycin, neomycin, amikacin), fluoroquinolones (ciprofloxacin, levofloxacin, trovafloxacin, gatifloxacin, sparfloxacin, moxifloxacin), second-generation cephalosporins (will not cover pseudomonas), third-generation cephalosporins (ceftazidime, ceftriaxone), carbapenems (imipenem, meropenem), extended spectrum penicillins (piperacillin, ticarcillin, azlocillin, mezlocillin).* Carbapenems cover Gram-negative and Gram-positive, but you should not use them for Gram-positive infections (like strep throat) because there are better drugs exclusively for Gram-positives. Do not swat a fly on your friends head with a hammer.* TMP-SMX is only good for uncomplicated cystitis and prophylaxis against pneumocystis pneumonia.* Chloramphenicol is never the right answer, it causes aplastic anemia and Gray Baby Syndrome.* Cephalosporins range from strong Gram-positive coverage at first-generation (poor Gram-negative) to strong Gram-negative coverage at third-generation (poor Gram-positive). Fourth-generation cephalosporins (cefepime) are a combination of first-generation and third-generation, so they cover Gram-positives and Gram-negatives.* Antibiotics for anaerobes are metronidazole (particularly good for abdominal), clindamycin (does not cover bowel well), carbapenems as well. If you have an exclusively anaerobic infection, dont jump to imipenem.* Tetracycline is not the correct choice anymore; use doxycycline instead. Doxycycline used for Lyme (mild disease: rash, facial nerve palsy), Chlamydia, rickettsia, as these are intracellular organisms.* Nitrofurantoin used for UTI in pregnancy, no other use.