[In vitro activity of six fluoroquinolones and penicillin against 101 viridans group streptococci characterized by their susceptibility to erythromycin].
The increase in the use of the fluoroquinolones, including for the treatment of lower respiratory tract infections, seems to be associated with a parallel increase in bacterial resistance. We studied the activity of penicillin and six fluoroquinolones against 101 viridans group streptococci isolated from blood (58 erythromycin-susceptible and 43 erythromycin-resistant). The percentage of strains not susceptible to penicillin was 35% and there were statistically significant differences in the percentages of penicillin resistance between erythromycin-susceptible and -resistant strains. The fluoroquinolones studied showed good activity against our viridans group streptococci independent of their susceptibility to erythromycin. The norfloxacin MIC(50) and MIC(90) were 8 and 16 mg/l, respectively. Ofloxacin and ciprofloxacin showed the same activity (MIC(50) 1 mg/l and MIC(90) 2 mg/l); levofloxacin was similar with MIC(50) and MIC(90) of 1 mg/l. The fluoroquinolones with enhanced activity were moxifloxacin and trovafloxacin (MIC(50) 0.12 mg/l and MIC(90) 0.25 mg/l). However, we found two strains resistant to trovafloxacin (MIC = 4 mg/l) that showed reduced susceptibility to all the fluoroquinolones tested, including moxifloxacin (MIC = 2 mg/l). Mutations in the topoisomerase genes parC and gyrA have been shown to occur in strains with reduced susceptibility; therefore, ongoing surveillance for the development of fluoroquinolone resistance in viridans streptococci is necessary.
Rodríguez-Avial
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I
Servicio de Microbiología, Hospital Clínico San Carlos, Facultad de Medicina, Universidad Complutense de Madrid, Martín Lagos s/n, 28040 Madrid, Spain.
Rodríguez-Avial
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C
Picazo
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JJ
D000890:Anti-Infective Agents / Q000494:pharmacology*; D001372:Aza Compounds; D016470:Bacteremia / Q000382:microbiology; D002939:Ciprofloxacin / Q000494:pharmacology; D004351:Drug Resistance; D024901:Drug Resistance, Multiple, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D024841:Fluoroquinolones; D006801:Humans; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D000077266:Moxifloxacin; D009287:Naphthyridines / Q000494:pharmacology; D009643:Norfloxacin / Q000494:pharmacology; D015242:Ofloxacin / Q000494:pharmacology; D010406:Penicillins / Q000494:pharmacology*; D011804:Quinolines; D013290:Streptococcal Infections / Q000382:microbiology; D013291:Streptococcus / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification
D000890:Anti-Infective Agents; D001372:Aza Compounds; D024841:Fluoroquinolones; D009287:Naphthyridines; D010406:Penicillins; D011804:Quinolines; D002939:Ciprofloxacin; D004917:Erythromycin; D064704:Levofloxacin; C080163:trovafloxacin; D015242:Ofloxacin; D009643:Norfloxacin; D000077266:Moxifloxacin