Random amplified polymorphic DNA and amplified fragment length polymorphism analyses of Pasteurella multocida isolates from fatal fowl cholera infections.

Fowl cholera, a disease caused by Pasteurella multocida, continues to be a major problem for the poultry industry. The sources of pathogenic organisms responsible for most sporadic epidemics remain unconfirmed, although attenuated vaccines that retain a low level of virulence have occasionally been implicated in outbreaks of the disease. One of the vaccines most commonly used to prevent fowl cholera is the M-9 strain. In the present study, 61 clinical isolates from turkeys that died of fowl cholera from 1997 to 1999 on 36 Utah farms were analyzed and compared to the M-9 vaccine strain. Genetic analyses of the isolates were done by random amplified polymorphic DNA (RAPD) analysis and amplified fragment length polymorphism (AFLP) fingerprinting. The results of these genetic analyses were correlated with the vaccination status of the flock, isolate serotype, and geographic location. Although both genetic techniques effectively identified similar subtle genomic differences, RAPD analysis provided only 77% of the detail provided by AFLP analysis. While a relationship between genetic profile and serotype was evident, no significant relationship indicating geographic influence was found (P = 0.351). Interestingly, organisms isolated from vaccinated flocks were significantly closer genetically to the M-9 vaccine strain than isolates from unvaccinated birds were (P = 0.020). Statistical analyses revealed that this relationship could not have been determined by serotyping alone (P = 0.320), demonstrating the value of AFLP and RAPD analyses in the characterization of disease-causing strains.