In Vitro and In Vivo Activities of Newer Fluoroquinolones against Vibrio vulnificus

Abstract

The MICs of six fluoroquinolones as well as minocycline and cefotaxime for 46 clinical isolates of Vibrio vulnificus were determined by the agar dilution method. All the drugs tested had good activities against all isolates, with the MICs at which 90% of the isolates tested were inhibited (MIC 90 s) by five of the fluoroquinolones ranging between 0.03 and 0.06 g/ml. The MIC 90 of lomefloxacin, on the other hand, was 0.12 g/ml. Vibrio vulnificus is a halophilic, gram-negative bacillus recovered from estuarine and seawaters (15). Many cases of V. vulnificus infections have been reported from the coastal areas of the United States (1, 2, 16), Asia (4, 5, 24; Y. C. Chuang, Letter, Clin. Infect. Dis. 15:1072, 1992), and Europe (10, 18). The high prevalence of hepatitis B infections in areas such as Taiwan may also contribute to the high incidence of severe V. vulnificus infections. V. vulnificus characteristically produces three discernible syndromes (2,4,5,20,25): primary sepsis, wound infection, and gastrointestinal illness. The mortality rates are up to 55% in septic patients and 25% in those with wound infections (5).Most of the V. vulnificus isolates are susceptible in vitro to a variety of antibiotics (1, 3, 11, 13, 14; P. R. Hsueh, J. C. Chang, S. C. Chang, S. W. Ho, and W. C. Hsieh, Letter, Eur. J. Clin. Microbiol. Infect. Dis. 14:151-153, 1995). Tetracycline has been recommended as the antimicrobial agent of choice for the treatment of V. vulnificus infection because of the effectiveness of tetracycline for V. cholerae infections. More recently, our in vitro study showed that a combination of cefotaxime and minocycline had a synergistic effect against V. vulnificus (6). A further in vivo study showed that therapy with a combination of cefotaxime and minocycline is more advantageous than singledrug regimens with these agents for the treatment of severe experimental murine V. vulnificus infection (9). Ciprofloxacin has also been used successfully for the treatment of V. vulnificus wound infections (M. C. Meadors and G. A. Pankey, Letter, J. Infect. 20:88-89, 1990). In general, the newer fluoroquinolones developed over the past few years have greater potency, a broader spectrum of antimicrobial activity, greater in vitro efficacy against resistant organisms, and a better safety profile than other antimicrobial agents. Moreover, step-down therapy, a cost-saving alternative, has been claimed to be advantageous. For this reason, the activities of the new fluoroquinolones against V. vulnificus were evaluated in the present study both in vitro and in vivo in comparison with that of cefotaxime-minocycline. MATERIALS AND METHODSDetermination of the MICs of cefotaxime, minocycline, and six newer fluoroquinolones for 46 clinical isolates of V. vulnificus. Clinical isolates of V. vulnificus were collected from Chi Mei Foundation Medical Center, National Cheng Kung University Hospital, and the National Taiwan University Hospital. These strains were originally isolated from blood or from wound or bullous fluid. All isolate...

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