Molecular Characterization of Pasteurella multocida Isolates that Cause Haemorrhagic Septicaemia in Thailand using Pulsed-field Gel Electrophoresis

Abstract

Pasteurella multocida causes haemorrhagic septicaemia (HS), which is a severe epidemic disease in cattle and buffaloes. In this study, serological typing, minimum inhibitory concentration (MIC) and pulsed-field gel electrophoresis (PFGE) were used to characterize 87 HS isolates caused by P. multocida from cattle and buffaloes during 1989 to 2011 in comparison with Thai and Laotian vaccine strains and the reference P. multocida strain P1256. The results of serotyping showed that the majority of the isolates (88.5%) belonged to serotype B: 2 (n = 77) while 11.5% shared with serotype B: 2, 5 (n = 10). MIC results showed that 100% of the isolates were sensitive to enrofloxacin and tilmicosin with MIC90 at 0.25 and 8 μg/ml, respectively, while 100%, 67.8% and 20% resistance were found to penicillin G, tetracycline and doxycycline with MIC90 at 64, 8 and 2 μg/ml, respectively. ApaI-digested PFGE revealed a high degree of homogeneity. Eighty one isolates were PFGE type 4 (93.10%), as well as the Thai and Laotian vaccine strains, 4 isolates were PFGE type 1 (4.60%), 1 isolate was PFGE type 2, and 1 isolate was PFGE type 3. The reference P. multocida strain P1256 belonged to PFGE type 2. In conclusion, a remarkable homogeneity was observed among the HS isolates caused by P. multocida in Thailand over the past 22 years.