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Clinical strains of Stenotrophomonas maltophilia are often highly resistant to multiple antibiotics and this resistance is steadily rising. Quinolones are included in the group of antimicrobial agents to which this microorganism is developing resistance. Therefore, the aim of this study was to analyze the epidemiological relationship among 22 clinical isolates of S. maltophilia as well as the molecular mechanisms responsible for the acquisition of quinolone-resistance in these strains. The results of the pulsed-field gel electrophoresis (PFGE) showed an heterogenicity of 82% among the strains used in the study. On the other hand, no amino acid changes were found in the quinolone resistance-determining region (QRDR) of either gyrA and parC genes among quinolone-susceptible and -resistant S. maltophilia strains. Besides, the amino acid of the GyrA found in the position equivalent to Ser-83 of E. coli was Gln instead of a Ser or Thr, the amino acids usually encountered in this position among Gram-negative bacteria. The results suggest that there is not a relationship between the presence of this Gln and the resistance to quinolones in S. maltophilia. We can conclude that, contrary to what has been described in other microorganisms, in these S. maltophilia isolates, the development of resistance to quinolones was not related to mutations in the QRDR of gyrA and parC genes. Thus, to our knowledge, this is the first report describing this phenomenon.

Traveler's diarrhea is the most common health problem of international travelers. Although enterotoxigenic Escherichia coli seems to be the most frequent cause of traveler's diarrhea, many other microorganisms, such as Campylobacter jejuni, may cause this infectious disease. Campylobacter jejuni is recognized as a leading cause of enteritis in humans both in developing and in developed countries. However, a few reports on the incidence and antimicrobial resistance of Campylobacter spp. as a cause of traveler's diarrhea have been published. The limited data on the treatment of C. jejuni infections suggest that ciprofloxacin may shorten the duration of symptoms. However, treatment failure associated with the emergence of quinolone-resistant strains of C. jejuni has been documented. The purpose of this study was to determine the prevalence of C. jejuni associated with traveler's diarrhea and to analyze the geographic distribution as well as the clinical features and susceptibility to antibiotics.