Specific detection of Pasteurella multocida in chickens with fowl cholera and in pig lung tissues using fluorescent rRNA in situ hybridization

A Pasteurella multocida species-specific oligonucleotide probe, pmhyb449, t argeting 16S rRNA was designed and evaluated by whole-cell hybridization ag ainst 22 selected reference strains in animal tissues. it differentiated P. multocida from other bacterial species of the families Pasteurellaceae and Enterobacteriaceae and also from divergent species of the order Cytophagal es (except biovar 2 strains of Pasteurella avium and Pasteurella canis, whi ch have high 165 rRNA similarity to P. multocida). The potential of the pro be for specific identification and differentiation of P. multocida was furt her detected in formalin-fixed paraffin-embedded lung tissues from experime ntal fowl cholera in chickens and infections in pigs. In chicken lung tissu es P. multocida cells were detected singly, in pairs, as microcolonies, and as massive colonies within air capillaries (septa and lumen), parabronchia l septa, and blood vessels (wall and lumen). In pig lung, postmortem-inject ed P. I,multocida was detected in the alveoli (lumen and wall), and in both animals the bacterial cells were seen in the bronchi, The results showed t hat with the oligonucleotide probe pmhyb449, fluorescent in situ hybridizat ion is a suitable and fast method for specific detection of P. multocida in histological formalin-fixed tissues. The test was replicable and reproduci ble and is recommended as a supplementary test for diagnosis and as a tool in pathogenesis studies of fowl cholera and respiratory tract infections in pigs due to P. multocida.