Antibiotic resistance trends were examined for Shigella species, nontyphoidal Salmonella species, enterotoxigenic Escherichia coli (ETEC), and Campylobacter species isolates from indigenous persons and travelers in Thailand for up to 15 years. Resistance to trimethoprim-sulfamethoxazole was found in ú90% of Shigella and 40% of ETEC and nontyphoidal Salmonella isolates. Resistance to nalidixic acid was found in 97% -100% of Shigella dysenteriae 1 strains isolated between 1992 and 1995. Ciprofloxacin resistance was detected in 1% of ETEC isolates in 1994 and 1995 and in one of 349 nontyphoidal Salmonella isolates in 1995. Ciprofloxacin resistance among Campylobacter species increased from zero before 1991 to 84% in 1995 (P õ .0001). Azithromycin resistance was found in 7% -15% of Campylobacter isolates in 1994 and 1995, as well as 15% of ETEC and 3% of Salmonella isolates in 1995. Enteric pathogens in Thailand have developed resistance to virtually all antibiotics routinely used in the treatment of diarrhea, as well as the newer fluoroquinolone and macrolide classes of drugs.

We evaluated the use of azithromycin (500 mg) or ciprofloxacin (500 mg) daily for 3 days for the treatment of acute diarrhea among United States military personnel in Thailand. Stool cultures were obtained and symptoms were recorded on study days 0, 1, 2, 3, and 10. Campylobacter species were the most common pathogen isolated (44 isolates from 42 patients). All Campylobacter isolates were susceptible to azithromycin; 22 were resistant to ciprofloxacin. Among the 42 patients with campylobacter infection, there were 2 clinical and 6 bacteriologic treatment failures in the ciprofloxacin group and no treatment failures in the azithromycin group (P = .021 for bacteriologic failures). Overall, azithromycin was as effective as ciprofloxacin in decreasing the duration of illness (36.9 hours vs. 38.2 hours, respectively) and the number of stools (6.4 vs. 7.8, respectively). Among those not infected with Campylobacter species (n = 30), the duration of illness was 32.9 hours vs. 20.7 hours (P = .03) for the azithromycin and ciprofloxacin groups, respectively. Azithromycin is superior to ciprofloxacin in decreasing the excretion of Campylobacter species and as effective as ciprofloxacin in shortening the duration of illness. Azithromycin therapy may be an effective alternative to ciprofloxacin therapy in areas where ciprofloxacin-resistant Campylobacter species are prevalent.

Antimicrobial resistance rates for shigella, campylobacter, nontyphoidal salmonella, and enterotoxigenic Escherichia coli were compared for Vietnam and Thailand from 1996 to 1999. Resistance to trimethoprim-sulfamethoxazole, ampicillin, chloramphenicol, and tetracycline was common. Quinolone resistance remains low in both countries, except among campylobacter and salmonella organisms in Thailand. Nalidixic acid resistance among salmonellae has more than doubled since 1995 (to 21%) in Thailand but is not yet documented in Vietnam. Resistance to quinolones correlated with resistance to azithromycin in both campylobacter and salmonella in Thailand. This report describes the first identification of this correlation and its epidemiologic importance among clinical isolates. These data illustrate the growing magnitude of antibiotic resistance and important differences between countries in Southeast Asia.