title: Bactericidal activity of levofloxacin, gatifloxacin, penicillin, meropenem and rokitamycin against Bacillus anthracis clinical isolates.
abstract: This study aimed to evaluate the bactericidal rates of levofloxacin, gatifloxacin, penicillin, meropenem and rokitamycin against seven isolates of Bacillus anthracis clinically isolated between 1960 and 1970. After determination of MIC and MBC, time-kill experiments were carried out. Antimicrobial activity was evaluated at concentrations equal to 1 x, 2 x, 4 x and 8 x MIC after 0, 3, 6, 12 and 24 h of incubation with the drugs. Bactericidal activity was defined as a decrease in bacterial count of at least 3 log10. All the isolates were susceptible to all the antibiotics, by considering the antistaphylococcal breakpoints. Levofloxacin was bactericidal at 1 x MIC after 24 h and at 4 x MIC after 12 h, and gatifloxacin was bactericidal at 2 x MIC after 24 h and at 8 x MIC after 12 h. Meropenem, rokitamycin and penicillin also showed bactericidal activity at concentrations of 4 x and 8 x MIC, respectively, but only after 24 h incubation; after the same time, meropenem and rokitamycin showed a more marked killing than penicillin at 2 x MIC.
authors.affiliation: Laboratory of Clinical Microbiology, L. Sacco Teaching Hospital, University of Milan, Via GB Grassi 74, 20157 Milan, Italy. microbio@mailserver.unimi.it
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Drago
authors.forename: Elena
authors.initials: E
authors.lastname: De Vecchi
authors.forename: Alessandra
authors.initials: A
authors.lastname: Lombardi
authors.forename: Lucia
authors.initials: L
authors.lastname: Nicola
authors.forename: Marilena
authors.initials: M
authors.lastname: Valli
authors.forename: Maria Rita
authors.initials: MR
authors.lastname: Gismondo
mesh_terms: D000881:Anthrax / Q000188:drug therapy / Q000382:microbiology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000890:Anti-Infective Agents / Q000494:pharmacology; D001408:Bacillus anthracis / Q000187:drug effects* / Q000254:growth & development / Q000302:isolation & purification*; D024841:Fluoroquinolones; D000077734:Gatifloxacin; D006801:Humans; D064704:Levofloxacin; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D015644:Miocamycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D015242:Ofloxacin / Q000494:pharmacology; D010406:Penicillins / Q000494:pharmacology; D013845:Thienamycins / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D010406:Penicillins; D013845:Thienamycins; D015644:Miocamycin; D064704:Levofloxacin; D015242:Ofloxacin; D000077731:Meropenem; D000077734:Gatifloxacin; C033383:rokitamycin