[Comparative in vitro bacteriostatic and bactericidal activity of levofloxacin and ciprofloxacin against urinary tract pathogens determined by MIC, MBC, Time-Kill curves and bactericidal index analysis].
The Bactericidal Index is a new way to assess bactericidal activity, representing the total bacterial kill over a drug concentration range. The aim of the study was to compare the in vitro activity of LEV with that of CIP against uropathogens determined by MIC, MBC, time-kill curves and BI analysis. A total of 141 strains [E. coli (EC) n=30; Klebsiella spp n=30; P aeruginosa (PA) n=35; P. mirabilis (PM) n=21; E. cloacae n=25] were preliminarily tested for MIC evaluation. MICs were obtained by 100 l microbroth dilution, followed by whole volume transfer for MBC determination. The time-kill tests were determined with 3 isolates each of EC, PA and PM and the killing monitored over 24h. FQs were added to a final concentration of 0.25, 0.5, 1, 2, 4, 8 and 16xMIC. Aliquots were sub-cultured at intervals. To assess the BI, overnight bacterial cultures were diluted to about 107 CFU/ml and set up containing a range of drug concentrations. MIC values of LEV were slightly higher than CIP; MBC/MIC ratio was in the range 1:1/1:2. LEV showed 99.9% killing after 6h against EC and after 3 h against PA at 1xMIC and after 3h at 2xMIC against PM in contrast with CIP (after 3h at 8xMIC). The BI data showed that FQs became more bactericidal with increasing incubation time and evidenced the enhanced bactericidal potency of LEV. A paradoxical effect was observed for all PA and PM strains, with slower killing at high concentrations of LEV (128 g/ml) at 24h and CIP (4 g/ml) at 3h. CIP was more active in terms of MIC values but LEV exhibited similar or even better bactericidal activity when time-kill curves or BI were compared. Calculation of BI allows the bactericidal activity of drugs, at clinically relevant concentrations, to be readily compared.
Noviello
Silvana
S
Dipartimento di Medicina Pubblica Clinica e Preventiva, Sezione di Malattie Infettive, Dottorato di Ricerca in Scienze Farmacologiche e Fisiopatologia Respiratoria, Seconda Università degli Studi di Napoli, Italy.
Ianniello
Filomena
F
Leone
Sebastiano
S
Esposito
Silvano
S
D000890:Anti-Infective Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006801:Humans; D064704:Levofloxacin; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology*; D014552:Urinary Tract Infections / Q000382:microbiology*
D000890:Anti-Infective Agents; D002939:Ciprofloxacin; D064704:Levofloxacin; D015242:Ofloxacin
Attivit  batteriostatica e battericida di levofloxacina verso uropatogeni determinata mediante MIC, MBC, Time-kill curves e analisi dell'indice di batteriocidia.