Evaluación de la actividad de diferentes antimicrobianos frente a Streptococcus pneumoniae provenientes de pacientes adultos con neumonía adquirida en la comunidad

steptococcus pneumoniae is the main etiologic bacterial agent of respiratory tract infections and in recent years emergence of isolates with multiple resistance has been observed. during the years 2008 and 2009 we studied 59 s. pneumoniae strains isolated from blood cultures and respiratory materials from patients with pneumonia and tested their susceptibility to different antimicrobials. there was no resistance to parenteral penicillin (intravenous), amoxicillin, ceftriaxone and carbapenems. to oral and parenteral cefuroxime the resistance was 3.4% and 5.1% respectively; 15.2% of the isolates showed intermediate susceptibility to oral penicillin with mics between 0.125 and 1 μg/ml. only 1/59 isolates was resistant to levofloxacin (mic = 8 μg/ml) but it was susceptible to gatifloxacin (mic = 0.5 μg/ml). erythromycin resistance was 20.3% and the predominant phenotype was m (efflux) confirmed by the presence of the mef gene. tetracycline resistance was 6.8% and there was no resistance to tigecycline (cim90 = 0.5 μg/ml). all isolates were susceptible to vancomycin, linezolid and rifampicin. the resistance to trimethoprim-sulfamethoxazole was 21.4%. in conclusion, parenteral (intravenous) penicillin and amoxicillin, independently of the way of administration, remain the antimicrobial β-lactams most suitable for the empirical treatment of pneumonia, while macrolides should be used with caution because of the high proportion of resistance. although levofloxacin resistance remains low, we consider it should only be used in special situations and in adequate doses in order to prevent the selection of resistant mutants.