National Committee for Clinical Laboratory Standards (10). Antimicrobial disks (ampicillin 10 µg; cefotaxime 30 µg; chloramphenicol 30 µg; ciprofloxacin 5 µg; nalidixic acid 30 µg; tetracycline 30 µg; and trimethoprim-sul- famethoxazole 1.25/23.75 µg) were obtained from Becton Dickinson (Cockeysville, MD). E. coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853 were used as qual- ity-control strains. Results Distribution and Geographic Origin of Species Causing Traveler’s Diarrhea Aeromonas spp. were isolated as a cause of traveler’s diarrhea in 18 (2%) of 863 patients. A. veronii biotype sobria was isolated in nine patients, A. caviae in seven patients, and A. jandaei and A. hydrophila in one patient each (Table 1). In three of these patients, another enteropathogen was also found: in one patient who had traveled to Mexico, Shigella sonnei was isolated together with A. veronii; in another patient traveling to India, Giardia lamblia was detected together with A. veronii; in the third patient, who had traveled to Thailand, Salmonella Typhimurium was found with A. veronii. The frequency of Aeromonas spp. as a cause of traveler’s diarrhea was sim- ilar in patients returning from Africa (1.7%), Latin America (1.8%), and Asia (2.3%) (Table 1). Clinical Features The signs and symptoms of Aeromonas enteritis in these 18 patients are summarized in Table 2. Sixteen of the 18 patients had watery diarrhea; these were the cases asso- ciated with A. veronii biotype sobria and A. caviae. The patients with enteritis caused by A. hydrophila and A. jan- daei had loose stools. Fifty percent of the patients had fever and abdominal cramps, whereas nausea and vomiting were uncommon complaints. Gross blood was observed in the stools of one patient, but this could be attributed to the RESEARCH S. sonnei isolated in the same stool. In 9 of the 18 patients, diarrhea was persistent. Antimicrobial Susceptibility The antimicrobial susceptibility of Aeromonas spp. iso- lates causing traveler’s diarrhea is shown in Table 3. All strains were resistant to ampicillin but susceptible to cefo- taxime, ciprofloxacin, and nalidixic acid. The susceptibili- ty to chloramphenicol, tetracycline, and trimethoprim-sul- famethoxazole varied. Some 66.6% of A. veronii biotype sobria strains and 71.4% of A. caviae strains were suscep- tible to chloramphenicol; 55.6% of A. veronii biotype sobria strains and 71.4% of the A. caviae strains were sus- ceptible to tetracycline; and 77.8% of A. veronii biotype sobria and 100% of A. caviae were susceptible to trimetho- prim-sulfamethoxazole. Treatment While travelling, two patients received treatment, amoxicillin in one case and amoxicillin plus clavulanic acid in the other. Patients with persistent diarrhea were treated with the following antibiotics: norfloxacin (one patient), ciprofloxacin (six patients), and trimethoprim- sulfamethoxazole (two patients); all recovered. Discussion In this study we describe the prevalence of different types of Aeromonas species associated with traveler’s diar- rhea in a cohort of travelers to a variety of tropical and sub- tropical countries. In contrast, other published studies have often been selective in terms of the types of travelers, geo- graphic areas visited, or attempts to isolate specific microorganisms with the aim of testing antibiotic efficien- cy. In our study, Aeromonas spp. were isolated in 18 (2%) of 863 patients with traveler’s diarrhea. A. veronii biotype sobria and A. caviae were the most frequently isolated species. These findings agree with the results of Hänninen et al. (11), who reported that these were the most common Table 1. Species and geographic distribution of clinical isolates of Aeromonas spp. causing traveler’s diarrhea Geographic area A. veronii biotype sobria (n=9) A. caviae (n=7) A. jandaei ( n=1) Guatemala 1 1 India 2 1a 1a Iran 1 Kenya 1 Mali/Burkina Faso 1 Mexico 2b Nicaragua 1 Paraguay 1 Sahara 1 Senegal 2 Thailand 1 aThis patient traveled to India and Nepal. bOne traveler also visited Guatemala. A. hydrophila (n=1) 1 Emerging Infectious Diseases • Vol. 9, No. 5, May 2003 553