RESEARCH Table 2. Clinical features of patients with traveler’s diarrhea associated with Aeromonas spp. No. of patients with symptoms/ total patients (n=18) A. veronii A. Overalla Sign or symptom biotype sobria caviae Watery diarrhea 9/9 7/7 16/18 Abdominal cramps 6/9 3/7 10/18 Persistent diarrhea 3/9 5/7 9/18 Fever 6/9 3/7 10/18 Nausea, vomiting, or both 2/9 0/7 3/18 Gross blood in stools 1b/9 0/7 1/18 aAlso includes A. hydrophila and A. jandai. bIn this patient, a Shigella sonnei strain was also isolated. Aeromonas spp. associated with traveler’s diarrhea in tourists traveling to Morocco. Likewise, Yamada et al. (12) found that A. veronii biotype sobria was the Aeromonas species most frequently implicated as a cause of traveler’s diarrhea in Japanese travelers returning from unindustrial- ized countries. In our study, the geographic distribution of Aeromonas species did not favor any predominant area: species were isolated with a similar prevalence in Africa, Latin America, and Asia. However, all four species (A. veronii biotype sobria, A. caviae, A. jandaei, and A. hydrophila) were isolated from patients returning from India. In India, Aeromonas spp. has been identified as an enteric pathogen in 1.8% of patients with diarrhea (13). In a recent study performed in Dhaka (Bangladesh), Aeromonas spp. were significantly associated with diar- rhea, similar to occurrences in other countries (14–17). In our study, 3 (16.7%) of the Aeromonas isolates were detected together with other enteropathogens. This situa- tion allowed us to consider that the symptoms we observed in the patients with traveler’s diarrhea associated with Aeromonas spp. were due to the presence of this Aeromonas organisms. In our study, watery stools, fever, and abdominal cramps were the most common symptoms, which is consistent with other reports (11,18). Albert et al. (18) suggested that isolates of Aeromonas spp. positive for both the alt and ast genes, which encode enterotoxins, were associated with watery diarrhea but that isolates pos- Table 3. Antimicrobial susceptibility of Aeromonas spp. causing traveler’s diarrhea No. of isolates showing susceptibility A. veronii biotype sobria (n=9) A. caviae (n=7) 0 0 9 7 6 5 9 7 9 7 5 5 7 7 Antimicrobial agent Ampicillin Cefotaxime Chloramphenicol Ciprofloxacin Nalidixic acid Tetracycline Trimethoprim/ sulfamethoxazole 554 Emerging Infectious Diseases • Vol. 9, No. 5, May 2003 itive only for the alt gene were associated with loose stools. Fifty percent of the patients with Aeromonas spp. enteritis had persistent diarrhea. Chronic diarrhea lasting more than 1 year caused by A. caviae has been reported (2). A direct link between drinking water and food contam- inated with Aeromonas spp. and gastrointestinal disease has been demonstrated (19). Patients with prolonged enteritis required treatment. A quinolone was the drug of choice, although increased occurrence of quinolone-resistant Aeromonas spp. strains has been reported in industrialized countries (20,21). Regarding the ß-lactam antibiotics, Aeromonas spp. strains analyzed in this study were, as expected, uniformly resist- ant to ampicillin, whereas third-generation cephalosporins, such as cefotaxime, showed good activity. These results are in accordance with those reported by other authors, showing that third-generation cephalosporins are active against Aeromonas spp. (2,22). The percentage of strains with resistance to chloramphenicol, tetracycline, or trimethoprim-sulfamethoxazole ranged from 22.9% to 45%. These levels of resistance are likely related to the extensive use of these antimicrobial agents in unindustrial- ized countries. In summary, A. veronii biotype sobria and A. caviae are the Aeromonas species most frequently associated with traveler’s diarrhea; watery diarrhea, fever, and abdominal cramps are the predominant clinical features. The persist- ence of symptoms makes the use of antimicrobial treat- ment necessary. This work was partially supported by grant FIS00/0997 of Fondo de Investigaciones Sanitarias. Dr. Vila is a professor of microbiology, School of Medicine, University of Barcelona, and consultant to the Clinical Microbiology Laboratory of the Hospital Clinic, Barcelona. His research interests lay in the molecular bases of antimicrobial resístance. References 1. Gascón J, Vila J, Valls ME, Ruiz L, Vidal J, Corachan M, et al. Etiology of traveller’s diarrhea in Spanish travellers to developing countries. Eur J Epidemiol 1993;9:217–23. 2. 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