Prevalence of Vibrio Species Isolated from Fecal Specimens of Patients with Diarrhea in Siriraj Hospital during 1994-2001

This is a retrospective study on Vibrio spp. isolated from patients with diarrhea (both inpatients and outpatients) at Siriraj Hospital, Bangkok, Thailand from January 1994 to December 2001. Of the 33,334 fecal specimens sent for culture, 2,229 (6.68%) were positive for pathogenic bacteria. The most commonly isolated bacteria was Vibrio (1,183 of 2,229 isolates, 53%). Of these 1,183 isolates, there were V. parahaemolyticus (420, 35.5%), V. cholerae (Ogawa) (279, 23.6%), V. cholerae 0139 (240, 20.3%), V. cholerae non-01/non-0139 (167, 14.1%), V. fluvialis (44, 3.7%), V. alginolyticus (22, 1.9%) and V. cholerae (Inaba) (11, 0.9%). The prevalence of Vibrio spp. was highest (76.01%) in 1994 and then rapidly decreased (30.51%) in 2001. V. cholerae were susceptible to ampicillin (81.69-99.5%), tetracycline (63.73-100%) except V. cholerae 0139 (29.3%), trimethoprim/sulfamethoxazole (70.05-100%), norfloxacin (100%), ofloxacin (98.09-100%) and ciprofloxacin (98.09-100%). Vibrio spp. other than V. cholerae were susceptible to ampicillin (67.4-30%), tetracycline (61.5-100%), trimethoprim/sulfamethoxazole (81.3-99.4%), quinolones (99.4-100%) and third-generation cephalosporins (100%). (J Infect Dis Antimicrob Agents 2004;21:838.) Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand. Received for publication: October 19, 2004. Reprint request: Somporn Srifuengfung, Ph.D., Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand. Keyword: Vibrio, Vibrio cholerae, Vibrio parahaemolyticus, Vibrio fluvialis, Vibrio alginolyticus INTRODUCTION Vibrio spp. are gram-negative, highly motile curved rods which are natural inhabitants of the marine environment. Pathogenic Vibrio spp. cause 3 major syndromes of clinical illnesses: gastroenteritis, wound infection and septicemia. Many species of Vibrio are considered pathogenic and capable of causing public health problems. Vibrio spp. of clinical relevance include V. cholerae, V. vulnificus, V. parahaemolyticus,V. mimicus and to a lesser extent, 84 J INFECT DIS ANTIMICROB AGENTS Sep.-Dec. 2004 V. furnissii, V. hollisae, V. damsela and V. alginolyticus, respectively.1-4 Early detection and initiation of treatment of Vibrio infections are very important, particularly of V. cholerae because these may rapidly progress to death5 due to severe diarrhea induced by an enterotoxin. Our study reports on the prevalence of Vibrio spp. isolated from patients at Siriraj Hospital, a medical center, Bangkok, Thailand from 1994 to 2001 and their antimicrobial susceptibility patterns. MATERIALS AND METHODS A total of 33,334 fecal samples and rectal swabs were obtained from patients of all age groups with acute diarrhea (both inpatients and outpatients) at Siriraj Hospital during January 1994 and December 2001 according to the laboratory methods.6 All specimens were initially cultured on blood agar, MacConkey agar, SS agar and thioglycolate citrate bile salt sucrose (TCBS) agar. They were also enriched in GN medium (semisolid agar), alkaline peptone water (APW), and incubated for 18-24 hours at 35C. After 6 hours of enrichment in APW, direct plating of the fecal samples was done on TCBS agar, and incubated at 35C for 24 hours. For the identification of Vibrio spp., slide agglutination was performed with V. cholerae polyvalent O1, monospecific Ogawa, Inaba, Hikoshima and O139 antisera. Antimicrobial susceptibility test This was performed on Mueller Hinton agar plates by the disk diffusion method of Kirby and Bauer.7 Ten antimicrobial agents used in this study included ampicillin, chloramphenicol, tetracycline, trimethroprim/ sulfamethoxazole, norfloxacin, ofloxacin, ciprofloxacin, cefotaxime, ceftriaxone, and ceftazidime. Escherichia coli ATCC 25922 was used as a quality control strain every time that clinical isolates were tested. RESULTS During the study period, 33,334 fecal cultures were carried out at Siriraj Hospital. Of these, 2,229 cultures (6.68%) were positive for pathogenic bacteria. The most commonly isolated bacteria was Vibrio spp. (1,183 of 2,229, 53%). The numbers of Vibrio spp. isolated from patients in each year are shown in Table 1. The prevalence of Vibrio spp. was highest (76.01%) in 1994 and then rapidly decreased to 30.51 percent in 2001 (Figure 1). Of Vibrio spp., there were V. parahaemolyticus (420, 35.5%), V. cholerae (Ogawa) (279, 23.6%), V. cholerae O139 (240, 20.3%), V. cholerae non-O1/non-O139 (167, 14.1%), V. fluvialis (44, 3.7%), V. alginolyticus (22, 1.9%) and V. cholerae (Inaba) (11, 0.9%) (Table 2). Table 1. The numbers of Vibrio spp. isolates at Siriraj Hospital during 1994 and 2001. Years 1994 1995 1996 1997 1998 1999 200