Characterization of Pasteurella multocida associated with ovine pneumonia using multi-locus sequence typing (MLST) and virulence-associated gene profile analysis and comparison with porcine isolates.

Pasteurella multocida is a pathogen causing disease in a wide range of hosts including sheep and pigs. Isolates from ovine pneumonia were characterized by MLST (Multi-host and RIRDC databases) and virulence-associated gene (VAG) typing and compared with porcine isolates. Ovine and porcine isolates did not share any STs as determined by both schemes and exhibited different VAG profiles. With the Multi-host database, sixteen STs were identified among 43 sheep isolates with two STs (ST50 and ST19) comprising 53.5% of the isolates, and seven MLST genotypes (ST3, ST11 and ST62 included 75% of the isolates) among the 48 pig isolates. The most frequent VAG profile among sheep isolates was tbpA+/toxA+ (69.8% of isolates) and pfhA+ (62.5%) and hgbB+ (33.3%) among pig isolates. Representative ovine and porcine isolates of those STs identified by the Multi-host scheme were further typed using the RIRDC scheme. Seven STs were identified among the ovine isolates (ST95RIRDC, ST131RIRDC, ST203RIRDC, ST320RIRDC, ST324RIRDC, ST321RIRDC, and ST323RIRDC), with the latter four sequence types being new STs identified in this study, and six STs (ST9RIRDC, ST13RIRDC, ST27RIRDC, ST50RIRDC, and ST74RIRDC and a new sequence type ST322RIRDC) among the porcine isolates. STs identified among ovine isolates have been detected exclusively in small ruminants, suggesting an adaptation to these hosts, while the genotypes identified among pig isolates have been previously identified in multiple hosts and therefore they are not restricted to pigs. The differences in genotypes and VAG profiles between ovine and pig isolates suggest they could represent different subpopulations of P. multocida.