Abstract
The fluoroquinolones are potent antimicrobial agents used for the treatment of infections caused by Gram-negative organisms. With the increased use of quinolones, increasing incidences of ciprofloxacin resistance have been reported (Garau et al., 1999). We previously collected 1203 Escherichia coli isolates from 44 hospitals through Taiwan Surveillance of Antimicrobial Resistance I (TSAR I). Of these, 136 (11.3 %), 211 (17.5 %) and 856 (71.2 %) isolates were respectively resistant, reduced-susceptible and susceptible to ciprofloxacin, based upon demonstration of disk diffusion zones of inhibition (Chen et al., 2001; McDonald et al., 2001).
Restriction patterns of chromosomal DNA were analysed by pulsed-field gel electrophoresis (PFGE) to determine the relatedness of 63 E. coli isolates obtained from three hospitals in Taiwan. These isolates consisted of 9, 29 and 25 ciprofloxacin-resistant, -reduced-susceptible and -susceptible isolates, respectively. According to cluster analysis, there was no predominate clone among these 63 isolates and no close relatedness was found among resistant isolates. A total of seven groups (AG) of isolates possessing more than 80 % relatedness (a difference of fewer than three bands) in DNA patterns were identified (Fig. 1). These seven genetically related groups consisted of 12 ciprofloxacin-reduced-susceptible isolates and four susceptible isolates. All groups consisted of two isolates except group C, which consisted of four isolates. There were three groups (groups B, C and F) with distinct, indistinguishable DNA patterns, and no direct or epidemiological linkage among them could be demonstrated. Group C consisted of four ciprofloxacin-reduced-susceptible strains that were isolated from four outpatients at the same hospital with a greater than 90 % relatedness (a difference of fewer than two bands). Two of these isolates had the same DNA patterns and antibiograms. Two reduced-susceptible isolates (strains 0816 and 0886) of group D also had greater than 90 % relatedness and similar antibiograms and were isolated 1 month apart from two outpatients at the same hospital.