Table 4.

Recommended antimicrobial therapy for specific pathogens

Organism	Preferred antimicrobials	Alternative antimicrobials
S pneumoniae (MIC <2 μg/mL)	Pencillin G; amoxicillin	Macrolide;* telithromycin cephalosporins (oral-cefpodoxime; cefdinir; cefprozil; cefuroxime, cefditoren; parenteral-cefuroxime, ceftriaxone, cefotaxime); clindamycin; doxycyline; fluoroquinolone†
S pneumoniae (MIC ≥2 μg/mL)	Agents based on susceptibility tests, including cefotaxime, ceftriaxone, fluoroquinolone† telithromycin (orally, for mild infections)	Vancomycin; linezolid; (high dose amoxicillin, 3 g/day, should be effective for strains with MIC 2–4 μg/mL)
H influenzae	Non-β lactamase producing: amoxicillin β lactamase producing: second or third generation cephalosporin; amoxicillin/clavulanate	Fluoroquinolone; doxycycline; azithromycin; clarithromycin‡
M pneumoniae/C pneumoniae	Macrolide; a tetracycline	Fluoroquinolone†
Legionella spp	Fluoroquinolone;§ azithromycin, clarithromycin	Doxycycline
C psittaci	A tetracycline	Macrolide
Cox burnetii	A tetracycline	Macrolide
Enterobacteriaceae	Third generation cephalosporin; carbapenem	β lactam β lactamase inhibitor¶; fluoroquinolone
P aeruginosa	Aminoglycoside plus antipseudomonal β lactam||	Aminoglycoside plus ciprofloxacin; ciprofloxacin or high dose levofloxacin** plus antipseudomonal lactam
Methicillin susceptible S aureus	Anti-staph penicillin††	Cefazolin; clindamycin
Methicillin resistant S aureus	Vancomycin	Teicoplanin; linezolid
Anaerobe (aspiration) Influenza	β lactam β lactamase inhibitor¶; clindamycin Amantadine or rimantadine (influenza A); oseltamivir or zanamivir (influenza A or B)	Carbapenem‡‡

Based on recommendations from IDSA and British Thoracic Society guidelines (choices should be modified based on susceptibility tests results and advice from local specialists. Refer to local references for appropriate doses)

^*Strains with reduced susceptibility to penicillin should have verified in-vitro susceptibility.

^†Levofloxacin, gatifloxacin, moxifloxacin (not a first-line choice for penicillin susceptible strains); ciprofloxacin is appropriate for Legionella, and most gram-negative bacilli (including H influenza).

^‡Azithromycin more active in vitro than clarithromycin for H influenza.

^§Author's preference.

^¶ticarcillin/clavulanate; piperacillin/tazobactam for gram-negative bacilli; ampicillin/sulbactam or amoxicillin/clavulanate appropriate for oral anaerobes. ||ticarcillin, piperacillin, ceftazidime; cefepime, aztreonam, imipenem, meropenem.

^**750 mg one daily.

^††nafcillin, oxacillin flucloxacillin.

^‡‡imipenem/cilastatin; meropenem; ertapenem.