Genetic variations of avian Pasteurella multocida as demonstrated by 16S-23S rRNA gene sequences comparison

Pasteurella multocida is known as an important heterogenic bacterial agent causes some severe diseases such as fowl cholera in poultry and haemorrhagic septicaemia in cattle and buffalo. A polymerase chain reaction (PCR) assay was developed using primers derived from conserved part of 16S-23S rRNA gene. The PCR amplified a fragment size of 0.7 kb using DNA from nine avian P. multocida  isolates. Sequence alignment of the 16S-23S rRNA genes (ITS) revealed a considerable heterogenicity among the isolates. The percentage of similarity varied from 83.3 to 100% among the isolates. An interesting finding from this study was the presence of an inserted sequence (seven nucleotides) in the 16S-23S rRNA region in 55% of the isolates. According to phylogenic analysis based on ITS sequence alignment, the P. multocida  isolates classified into 2 distinct clusters. The virulence of isolates in cluster II were higher than those in cluster I. Ribotyping of  P. multocida  by using 16S-23S rRNA gene PCR sequencing could be used as a marker in epidemiologic studies.