รูปแบบยีนของเชื้อ Vibrio cholerae O1 ที่ตรวจพบอุบัติซ้ำในจังหวัดตาก ปี 2558 Gene character of Vibrio cholerae O1 in Tak during the initial period of cholera occurrences in 2015 ศิริพร จันทน์โรจน์1*, วราวรรณ วงษ์บุตร2, วัชราภรณ์ คำจุมพล2, วิทยา สวัสดิวุฒิพงศ์3, อารี ทัตติยพงศ์1, สมชาย แสงกิจพร1 และ Kazuhisa Okada2 Siriporn Chantaroj1, Warawan Wongboot2, Watcharaporn Kamjumphol2, Witaya Swaddiwudhipong3, Aree Thattiyaphong1, Somchai Sangkitporn1, and Kazuhisa Okada2 1 สถาบันวิจัยวิทยาศาสตร์สาธารณสุข กรมวิทยาศาสตร์การแพทย์ กระทรวงสาธารณสุข จังหวัดนนทบุรี 2 ศูนย์ความร่วมมือการวิจัยโรคติดต่ออุบัติใหม่และอุบัติซ้ำระหว่างประเทศไทยกับประเทศญี่ปุ่น จังหวัดนนทบุรี 3 โรงพยาบาลแม่สอด จังหวัดตาก 1 National Institute of Health, Department of Medical Sciences, Ministry of Public Health, Nonthaburi, Thailand, 2 Thailand – Japan Research Collaboration Center on Emerging and Re-emerging Infections, Nonthaburi, Thailand, 3 Mae Sot General Hospital, Tak, Thailand Introduction Cholera is a major public health concern worldwide. In Thailand, the rates of cholera incidence were low between 2012 and 2014. However, in September 2015, the first incidence of cholera was reported in the Thai-Myanmar border area called Umphang, in the Tak Province and the number of cases have since increased. In October, there was a community outbreak of cholera in Mae Sot District, which is 200 Km from Umphang. This study was designed to understand the clonal relationships of the isolates associated with the cholera outbreaks reported at these two sites. Method A total of 56 Vibrio cholerae isolates were obtained from patients/contacts in Umphang and Mae Sot between 3 September and 25 November in 2015. These isolates were characterized by serotyping, PCR assay for the virulence and regulatory genes of V. cholerae, drug susceptibility tests, and pulsed-field gel electrophoresis (PFGE). Result All isolates were identified as V. cholerae O1 serotype Ogawa and harbored virulence-associated genes including ctxAB, tcpA, zot, and ace. PFGE with NotI digestion revealed a total of 5 distinct pulsotypes, which were distinct from those of V. cholerae O1 as previously reported in the Tak province. The pulsotypes A11 (13/14, 92.9%) and A13 (40/42, 95.2%) were found predominantly in Umphang and in Mae Sot, respectively. The remaining three isolates exhibited unique patterns (A12, A14, and A15). Antimicrobial susceptibility profiles of both the clusters revealed the same resistance pattern for sulfamethoxazole/trimethoprim, intermediate resistance towards tetracycline and were susceptible to ampicillin, ciprofloxacin and norfloxacin. Figure 1 Hexaplex PCR for detection of species-specific genes and virulence-associated genes in V. cholerae O1 isolates from Umphang and Mae Sot District, Tak. Lane M, 100 bp DNA ladder; lanes 1-4, Umphang isolates; lanes 5-9, Mae Sot isolates; lane 10, positive control (V. cholerae O1, N16961); lane 11, negative control. Table Antimicrobial susceptibility pattern of V. cholerae isolated from cholera patients in Umphang and Mae Sot District, Tak Province. Figure 2 Dendogram showing pulsotypes and similarities of V. cholerae isolates in Umphang and Mae Sot District, Tak Province. In conclusion, cholera outbreaks in the two districts of the Tak province were unrelated and of different origins.