Institute of Medical Microbiology, University Hospital (RWTH) Aachen, National Reference Center for Streptococci, Pauwelsstrasse 30, D-52057 Aachen, Germany
Sir,
The incidence of infections caused by pneumococci resistant to penicillin has increased at an alarming rate during the past two decades. In Europe, the highest incidences of resistance to penicillin among clinical isolates of Streptococcus pneumoniae have been recorded in France, Spain and the Slovak Republic.1 The recent development of various fluoroquinolones, such as gatifloxacin, moxifloxacin, trovafloxacin, sparfloxacin, levofloxacin and grepafloxacin, is of interest because of their extended in vitro Grampositive activity.2 Gatifloxacin is a novel 8-methoxy fluoroquinolone and, together with moxifloxacin, represents a new group of fluoroquinolones. In the present study, 174 penicillin-susceptible isolates of S. pneumoniae were randomly selected from a collection of strains obtained from blood cultures of patients with bacteraemic pneumococcal pneumonia as part of the 19921997 national surveillance study of antimicrobial resistance of S. pneumoniae in Germany.3 The antimicrobial susceptibility of 26 pneumococcal isolates showing reduced sensitivity to penicillin G (MIC 0.1 mg/L) was also tested. The MICs of gatifloxacin, ciprofloxacin, levofloxacin, ofloxacin, sparfloxacin, erythromycin, tetracycline and penicillin G were determined by standard agar dilution technique using MuellerHinton agar (Oxoid, Basingstoke, UK) supplemented with 5% sheep blood (Oxoid). Results of MIC determinations are presented in the table. All strains were inhibited by gatifloxacin 1 mg/L (MIC90 0.5 mg/L; MIC range 0.031.0 mg/L). The values were two or three dilution steps lower than the MIC90s obtained with ciprofloxacin (MIC90 4 mg/L; MIC range 0.58 mg/L). In vitro activity of the fluoroquinolones was not influenced by the penicillin susceptibility of strains. Resistance to levofloxacin (MIC
8 mg/L) was not observed; only two isolates (1%) were levofloxacin intermediate (MIC 4 mg/L). According to the recently proposed breakpoints for S. pneumoniae (resistant:
4 mg/L), all strains in this study were susceptible to gatifloxacin.4 The present study demonstrated excellent in vitro activity of gatifloxacin against clinical S. pneumoniae isolates. In a recent international surveillance study, the in vitro activity of gatifloxacin, penicillin, erythromycin and four other peer drugs was tested against 2284 pneumococcal strains isolated in 1997 in Canada, the USA, six Latin American countries and Europe. Gatifloxacin demonstrated uniform potency against pneumococci across all monitored geographical areas (MIC90 0.5 mg/L).5 Nevertheless, wider usage of this class of antibiotics may result in a change of the present excellent resistance situation in pneumococci.6 These data indicate that the resistance of S. pneumoniae to newer fluoroquinolones should be carefully monitored and underscore the risk of uncritical and broad usage of these antibiotics undermining the excellent resistance situation in the near future.
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Notes
J Antimicrob Chemother 2000; 46: 854856
* Corresponding author. Tel: +49-241-8089787; Fax: +49-241-8888-483; E-mail: reinert{at}rwth-aachen.de
References
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