Identification of potentially virulent strains of Haemophilus parasuis using a multiplex PCR for virulence-associated autotransporters (vtaA).
Haemophilus parasuis is the aetiological agent of Glässer's disease and is also a commensal of the upper respiratory tract of pigs. Trimeric autotransporter (vtaA) genes have been identified in H. parasuis and divided into three groups on the basis of the translocator domain sequence. In this study, group 3 vtaA genes were demonstrated by PCR in all 157 H. parasuis isolates tested. Group 1 vtaA genes were associated with virulent strains; 52/54 (96%) group 1 vtaA negative field isolates were isolated from the nasal passages of healthy animals, whereas no group 1 vtaA negative field isolates were isolated from cases of Glässer's disease. There was an association between absence of group 1 vtaA, sensitivity to phagocytosis and serum and classification of isolates into nasal cluster C by multilocus sequence typing. A multiplex PCR was developed for diagnosis of H. parasuis at the species level (group 3 vtaA positive) and to differentiate putative non-virulent strains (group 1 vtaA negative). When applied to field samples, the PCR confirmed a high prevalence of H. parasuis in conventionally farmed pigs and demonstrated that almost half of the animals carried potentially virulent strains.
Centre de Recerca en Sanitat Animal (CReSA), UAB-IRTA, Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain. alex.olvera@cresa.uab.cat
Alex
A
Olvera
Sonia
S
Pina
Núbia
N
Macedo
Simone
S
Oliveira
Virginia
V
Aragon
Albert
A
Bensaid
D000818:Animals; D015373:Bacterial Typing Techniques / Q000662:veterinary; D017931:DNA Primers; D006192:Haemophilus Infections / Q000382:microbiology / Q000662:veterinary*; D044137:Haemophilus parasuis / Q000235:genetics / Q000302:isolation & purification*; D060885:Multiplex Polymerase Chain Reaction / Q000662:veterinary; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000032:analysis; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*; D037521:Virulence Factors
D017931:DNA Primers; D012336:RNA, Ribosomal, 16S; D037521:Virulence Factors