The mutations that are responsible for fluoroquinolone resistance in the gyrA, gyrB, parC, and parE genes of Salmonella enterica serovar Typhi and serovar Paratyphi A were investigated. The sequences of the quinolone resistance-determining region of the gyrA gene in clinical isolates which showed decreased susceptibilities to fluoroquinolones had a single mutation at either the Ser-83 or the Asp-87 codon, and no mutations were found in the gyrB, parC, and parE genes.Fluoroquinolones have become the first-line drugs for the treatment of typhoid fever (3,12,18,23). However, some Salmonella enterica serovar Typhi strains that exhibit decreased susceptibilities to fluoroquinolones have been already reported (2,7,13,21). Furthermore, several clinical treatment failures after the administration of ciprofloxacin and other fluoroquinolones to patients with typhoid fever due to strains with decreased susceptibilities to fluoroquinolones have also been reported (17, 21). The emergence and spread of these organisms have been reported in developing countries. There is evidence that the incidence of strains that are resistant to nalidixic acid and that exhibit decreased susceptibilities to the most recent fluoroquinolones used for the treatment of typhoid fever is increasing. In most strains, the acquired fluoroquinolone resistance was attributed to mutations in the genes encoding DNA gyrase (GyrA, GyrB) (10, 24-26) or DNA topoisomerase IV (ParC, ParE) (8, 9). The purpose of this study was to investigate the association of quinolone resistance with mutations in the genes coding for gyrase and topoisomerase IV of S. enterica serovar Typhi and serovar Paratyphi A, which are especially clinically important serotypes of Salmonella spp.The bacterial strains used in this study were collected from regional public health offices in Japan between 1995 and 2001, and all isolates were obtained from a culture of either blood or stool from individual patients and identified by biochemical tests and serological tests on the basis of standard criteria. S. enterica serovar Typhi Ty2 and ATCC 19430 and S. enterica serovar Paratyphi A NCTC13, NCTC5702, and RIMD 1015 were used as reference and control strains (Tables 1 and 2). The MICs of several fluoroquinolones, including norfloxacin, levofloxacin, ofloxacin, sparfloxa cin, and ciprofloxacin, and nalidixic acid were determined by the Etest (AB Biodisk, Solna, Sweden), according to the instructions of the manufacturer. The quality control strains Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 29213 were included in each test. The criterion for ciprofloxacin resistance was an MIC of Ն4 g/ml, according to the NCCLS breakpoint criteria for members of the family Enterobacteriaceae. The criterion for decreased susceptibility to ciprofloxacin that we used in this study was an MIC between Ն0.25 and Ͻ4 g/ml, and that for ciprofloxacin susceptibility was an MIC Ͻ0.25 g/ml (19,20). An attempt to increase the level of fluoroquinolone resistance was done by culturing the fluoroquinolone-susce...

A total of 111 clinical isolates of Campylobacter jejuni and 10 clinical isolates of Campylobacter coli were characterized by their susceptibility to nine antimicrobial agents and by their plasmid profiles on agarose gel electrophoresis. All of the C. jejuni isolates were susceptible to chloramphenicol, ciprofloxacin, erythromycin, kanamycin, and nalidixic acid, but 55% were tetracycline resistant. In the 10 C. coli isolates, a high prevalence of multiple-antibiotic resistance was noted. Plasmids were found in 82% of the tetracycline-resistant and 15% of the tetracycline-susceptible C. jejuni isolates. Tetracycline resistance in six randomly selected C. jejuni isolates, which contained 50-or 135-kilobase (kb) plasmids, was transferred by conjugation to a Campylobacter fetus subsp. fetus recipient with recovery of a 50-or a 45-kb plasmid from transconjugants. From one multiple-antibiotic-resistant C. coli isolate, resistance to tetracycline, kanamycin, and chloramphenicol was transferred concomitantly with a 58-kb plasmid, pNR9589. Nonconjugative 98-kb plasmids, pNR9131 and pNR9581, from C. coli isolates with resistance to tetracycline, kanamycin, and erythromycin were shown by cloning experiments to code for at least kanamycin resistance. Restriction digests revealed that 50-kb plasmids from tetracycline-resistant C. jejuni isolates were identical, although plasmids from multiple-antibioticresistant C. coli isolates shared partial DNA homology to each other. Cloning of the kanamycin and chloramphenicol resistance genes of pNR9589 into Escherichia coli showed that the two genes are closely linked or clustered. Double-digestion analysis of the fragments encoding the kanamycin resistance of pNR9131, pNR9581, and pNR9589 showed that these three plasmids contain a common fragment related to kanamycin resistance.Campylobacterjejuni is recognized as one of the common causes of acute bacterial enteritis throughout the world (2, 17). More than 200 strains of C. jejuni and a small number of C. coli strains, 60% of which are from children, are isolated every year in Tokyo Metropolitan Toshima General Hospital.Taylor et al. (19, 20) and Tenover et al. (21) demonstrated that tetracycline resistance in C. jejuni is mediated by conjugative R plasmids with a size of 60 kilobases (kb), and more recently, Tenover et al. (22) showed that all tetracycline-resistant C. jejuni harbored R plasmids. Most recently, Taylor (18) mapped the tetracycline resistance plasmid. Studies on plasmid detection in Campylobacter spp.have not yet been carried out in Japan, although clinical and epidemiological studies on Campylobacter spp. have been performed extensively. In the present study, we examined the MICs of nine antimicrobial agents against Campylobacter isolates, the plasmid carriage in these isolates, and the relationship between antimicrobial resistance and plasmid carriage in C. jejuni and C. coli. Moreover, we analyzed three plasmids isolated from multiple-antibiotic-resistant C. coli strains by restriction endonuclease digestion and c...

Medical records, for 2000 and 2001, of symptomatic amoebic patients who were treated at our hospitals in Tokyo, Yokohama and Osaka were studied retrospectively for the purpose of gathering epidemiological data on symptomatic Entamoeba histolytica infection. A total of 58 patients were treated. Fifty-five of them were male, and 96% of the male patients were Japanese. The mean age of patients was 44.9 years old, and 91% of patients contracted the disease in Japan. Fifty-six per cent of the male patients indicated that they were practising homosexuals, and 44% of the male patients denied these practices or left the question unanswered. The serum Treponema pallidum haemagglutination test was positive in 45% of the patients, and antibody to human immunodeficiency virus (HIV) was positive in 45%. Our study revealed that recent symptomatic E. histolytica infection almost exclusively afflicted middle-aged males in the big cities of Japan, that a majority of the patients were probably exposed to the causative organism during homosexual activity, and that an increasing number of patients will be co-infected with HIV.

The antibiotic susceptibilities of 62 strains of Salmonella enterica serovar Typhi and 37 strains of S. enterica serovar Paratyphi A were investigated with 18 antibiotics. Eighteen S. enterica serovar Typhi isolates and five S. enterica serovar Paratyphi A isolates were resistant to one or more antimicrobial agents, among which 10 S. enterica serovar Typhi isolates were nalidixic acid resistant and also showed decreased ciprofloxacin susceptibility.

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