Application of ERIC-PCR for the comparison of isolates of Haemophilus parasuis

Objective To validate a polymerase chain reaction (PCR) based method, Enter obacterial Repetitive Intergenic Consensus-PCR (ERIC-PCR), for the fingerpr inting of Haemophilus parasuis strains and to use that method to differenti ate isolates from apparently related outbreaks of Glasser's disease on thre e pig farms. Design ERIC-PCR was evaluated by comparing 15 different strains that repres ented all 15 recognised serovars in the Kielstein-Rapp-Gabrielson (KRG) sch eme for serotyping H parasuis. Next, ERIC-PCR was used to examine 14 Austra lian field isolates of H parasuis; 12 collected from three farms suffering apparently related outbreaks of Glasser's disease and two from two other fa rms with no known connection. Results The 15 serovar reference strains all gave unique, reproducible ERIC -PCR fingerprints. The 12 isolates from the three apparently related outbre aks all gave a single fingerprint, which was distinct from any seen in the 15 serovar reference strains and the two other Australian field isolates in the studied farms. The confirmation that all 12 isolates were the same str ain allowed the development of a prevention and control program that has pr evented the emergence of any further outbreaks of Glasser's disease on the three farms. Conclusion ERIC-PCR is a suitable technique for the differentiation of unre lated strains of H parasuis. The finding that the 12 field isolates of H pa rasuis all shared the same fingerprint is strong evidence that there was a common source of infection on all three farms. This study has shown, for th e first time, that ERIC-PCR is a suitable technique for the sub-typing of H parasuis and useful for studying the epidemiology of outbreaks of Glasser' s disease.