Gram-negative Gram-positive Strep penicillin G, penicillin VK ampicillin, amoxicillin Penicillins amoxicillin/clavulanate cloxacillin piperacillin/tazobactam 1st cephalexin, cefazolin 2nd cefuroxime, cefprozil Cephalosporins 3rd ceftriaxone, cefotaxime 3rd ceftazidime 4th cefepime ertapenem Carbapenems imipenem, meropenem vancomycin Other "Grampositive" agents linezolid, daptomycin ciprofloxacin Quinolones levofloxacin moxifloxacin Aminoglycosides gentamicin, tobramycin colistin Polymyxins Sulfonamides Macrolides Lincosamides Tetracyclines and derivatives co-trimoxazole (TMP-SMX) erythromycin clarithromycin, azithromycin clindamycin tetracycline, doxycycline tigecycline Nitroimidazoles metronidazole       ± ±   ±                   ± ± ±       4 H .i n M flue . c nz at ae ar rh Pr al ot is eu E. s co K li le bs ie lla "S PA CE "b Ps ug eu s do m on as O ra la na e G ro ut be an s ae ro C. be di s ffi ci le M yc o Ch pla la sm m a yd op hi la                   ± ±  ±   ±    ± ±   ± ± ± ± ±         ±          1                1  ±2 2 2   1  2 2  1  3 1    1   5            CA(   CA(±) CA( ±                  7   ±          ±              ± 8    6   ±    ±    ±  SYN SYN SYN SYN SYN      ± Atypicals fa ec al is fa ec iu m   E. E. Co N S M RS A O th S. p ne um on ia er e St r ep M SS A Drug / Bug Table Anaerobes Enterococcus Staph    1 1   1 ±                 1 ±          Legend and Acronyms: Notes: CA: May be effective for community-associated MRSA SYN: Synergy (combine with another agent) CoNS: Coagulase-negative Staphylococcus MSSA: Methicillin-sensitive Staph aureus MRSA: Methicillin-resistant Staph aureus "SPACE" bugs: Serratia, P. vulgaris, Providencia, Morganella, Acinetobacter, Citrobacter, Enterobacter 1. These antibiotic may be associated with increased risk for C. difficile infection. 2. Avoid using as monotherapy due to inducible resistance in these bacteria. 3. Ertapenem does not cover Acinetobacter . 4. The activity of meropenem against E. faecalis is variable; no formal susceptibility breakpoints are available. 5. Only enteral (PO or PR) vancomycin (not IV) is effective against C. difficile infection. 6. Requires double coverage with another agent, as resistance can develop rapidly. 7. Colistin does not cover Proteus or Serratia . 8. Tigecycline has variable activity against Proteus .