Characterization of the diversity of Haemophilus parasuis field isolates by use of serotyping and genotyping.
OBJECTIVE
To characterize the genetic diversity of Haemophilus parasuis field isolates with regard to serovar, herd of origin, and site of isolation.


METHODS
Isolates of H parasuis obtained from pigs in 15 North American herds and multi-farm systems.


METHODS
98 H parasuis isolates were genotyped with the enterobacterial repetitive intergeneic consensus based-polymerase chain reaction (ERIC-PCR) technique and serotyped via agar gel precipitation test. Genomic fingerprints were analyzed and dendrograms were constructed to identify strains from the same serovar group, herd of origin, or isolation site and to evaluate the genetic variability within these categories.


RESULTS
Serovar 4 (39%) and nontypeable (NT) isolates (27%) were most prevalent. Thirty-four distinct strains were identified among the 98 isolates, using a 90% similarity cutoff. Strains from serovar 4 and NT isolates had high genetic diversity (12 and 18 strains, respectively). One to 3 major clusters of prevalent strains could be identified in most of the evaluated herds. Haemophilus parasuis strains isolated from the upper respiratory tract were either serovar 3 or NT isolates. Potentially virulent strains (isolated from systemic sites) were either serovars 1, 2, 4, 5, 12, 13, or 14, or NT isolates.


CONCLUSIONS
Although H parasuis had high genetic diversity overall, only a few strains caused disease in these herds. The ERIC-PCR technique was more discriminative than serotyping, and a broad genetic variety was observed within particular serovar groups.
Oliveira
Simone
S
Department of Clinical and Population Sciences, University of Minnesota, Saint Paul, MN 55108, USA.
Blackall
P J
PJ
Pijoan
Carlos
C
D000818:Animals; D016000:Cluster Analysis; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D006190:Haemophilus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D006192:Haemophilus Infections / Q000453:epidemiology / Q000382:microbiology* / Q000662:veterinary*; D009656:North America / Q000453:epidemiology; D010802:Phylogeny; D012703:Serotyping; D013552:Swine / Q000382:microbiology*; D013553:Swine Diseases / Q000453:epidemiology / Q000382:microbiology