Comparison of In Vitro Activities of Gatifloxacin and Ciprofloxacin against Four Taxa of Rapidly Growing Mycobacteria

Abstract

By using current NCCLS broth microdilution methods, we found that gatifloxacin inhibited 90% of the isolates of the Mycobacterium fortuitum group at <0.12 g/ml and 90% of the Mycobacterium chelonae isolates at <4 g/ml. Gatifloxacin was generally fourfold more active than ciprofloxacin. We recommend that both gatifloxacin and ciprofloxacin be tested routinely against rapidly growing mycobacteria.The fluoroquinolones have become increasingly important in the treatment of infections due to mycobacteria. Previous studies involving a wide variety of clinical bacterial isolates and the new 8-methoxy quinolone, gatifloxacin, have shown that gatifloxacin is more active than ciprofloxacin against untreated strains (1, 5) and that its activity (MIC) is less affected overall by mutations responsible for increasing quinolone resistance. Thus, we undertook a comparative study of the in vitro susceptibilities of the rapidly growing mycobacteria (RGM) to gatifloxacin and ciprofloxacin.(A portion of this study was presented at the 41st RGM were identified by using conventional methods, including drug susceptibility patterns (15), carbohydrate utilization tests, and PCR restriction enzyme analysis of a 439-bp sequence (Telenti fragment) of the 65-kDa hsp gene (8, 10).MICs were determined by use of the NCCLS-approved broth microdilution technique (6, 7). MICs of gatifloxacin were 0.12 to 32 g/ml, while those of ciprofloxacin were 0.12 to 16 g/ml (one lot number of panels used contained concentrations of ciprofloxacin of Յ0.25 to 16 g/ml). The MIC breakpoints indicating susceptibility, moderate susceptibility (intermediate), and resistance to gatifloxacin were Յ2, 4, and Ն8 g/ml, and those for ciprofloxacin were Յ1, 2, and Ն4 g/ml (the NCCLS breakpoints for Enterobacteriaceae and Staphylococcus species) (6). Gatifloxacin breakpoints for RGM have not yet been addressed by the NCCLS (7).For quality control tests, Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 were used. Acceptable MIC ranges for S. aureus ATCC 29213 are 0.03 to 0.12 and 0.12 to 0.5 g/ml for gatifloxacin and ciprofloxacin, respectively. Acceptable MIC ranges for E. coli ATCC 25922 are 0.008 to 0.03 and 0.004 to 0.016 g/ml for gatifloxacin and ciprofloxacin, respectively (6).Results for the major species (groups) of pathogenic RGM are shown in Tables 1 and 2. Generally, the MICs of gatifloxacin for all of the RGM except M. abscessus were 1 to 4 dilutions lower than those of ciprofloxacin.

Amoebal Coculture of “ Mycobacterium massiliense ” sp. nov. from the Sputum of a Patient with Hemoptoic Pneumonia

“…However, the clinical relevance of in vitro antibiotic susceptibility testing of "M. massiliense" is unknown; interestingly, the patient was cured after treatment with clarithromycin and minocycline, and "M. massiliense" was susceptible in vitro to these antibiotics. However, "M. massiliense" shared resistance to tobramycin (MIC, Ͼ8 g/ml) and ciprofloxacin (MIC, Ͼ32 g/ml) in common with M. abscessus (5,39,52).…”

Polyphasic Characterization Reveals that the Human Pathogen Mycobacterium peregrinum Type II Belongs to the Bovine Pathogen Species Mycobacterium senegalense

“…Drugs tested included amikacin, ciprofloxacin, sulfamethoxazole, imipenem, cefoxitin, tobramycin, and doxycycline (group A). More-recent isolates were also tested for susceptibility to five newer agents: linezolid (47), levofloxacin, gatifloxacin, meropenem, and clarithromycin (group B) (10,11). Susceptible and resistant breakpoints were those recently recommended by the Clinical Laboratory Standards Institute (CLSI, formerly NCCLS) except for meropenem, levofloxacin, and gatifloxacin, which have not been addressed by the CLSI (27).…”

High Prevalence of Antimicrobial Resistance in Rapidly Growing Mycobacteria in Taiwan

“…Some investigators have reported that in vitro susceptibilities to several of these agents correlated with clinical response to therapy (18,20). Furthermore, some recent in vitro susceptibility studies have demonstrated activity of newly developed antimicrobials (linezolid, telithromycin, tigecycline, and newer fluoroquinolones) against these organisms (3,8,26,28,32).With the increasing clinical importance of RGM responsible for clinical infections at the National Taiwan University Hospital (NTUH) and with an effort to identify potentially useful agents to treat these infections (9, 14, 30), we investigated the in vitro susceptibilities of recent RGM isolates to 15 antimicrobial agents, including those developed recently. …”

“…Some investigators have reported that in vitro susceptibilities to several of these agents correlated with clinical response to therapy (18,20). Furthermore, some recent in vitro susceptibility studies have demonstrated activity of newly developed antimicrobials (linezolid, telithromycin, tigecycline, and newer fluoroquinolones) against these organisms (3,8,26,28,32).…”