Taxonomic subgroups of Pasteurella multocida correlate with clinical presentation

Abstract

Pasteurella multocida is a small nonmotile gram-negative coccobacillus that is found in the nasopharynx and gastrointestinal tract of many wild and domesticated animals. In humans it most commonly causes cellulitis and localized superficial skin abscesses following an animal bite or scratch. The respiratory tract is the second most common site of infection for PASTEURELLA: Of the more than 17 species of Pasteurella known, Pasteurella multocida subsp. multocida and Pasteurella multocida subsp. septica are among the most common pathogens in humans. With the use of molecular techniques, distinction between different subspecies of P. multocida can be made more easily and accurately. We used the sequence of the 16S ribosomal DNA (rDNA) and repetitive extragenic palindromic sequence-PCR (REP-PCR) to characterize 20 strains (14 of P. multocida subsp. multocida and 6 of P. multocida subsp. septica; the 16S rDNA is identical for P. multocida subsp. multocida and Pasteurella multocida subsp. gallicida but differs from that of P. multocida subsp. septica) isolated from various anatomic sites. We found excellent correlation between the 16S rDNA sequence (a marker for a small conserved region of the genome), REP-PCR (a marker for a large portion of the genome), and biochemical tests (trehalose and sorbitol). We also found a correlation between the clinical presentation and the taxonomic group, with P. multocida subsp. septica more often associated with wounds than with respiratory infections (67 versus 17%, respectively) (P < 0.05, Z test) and P. multocida subsp. multocida more often associated with respiratory infections than with wounds (71 versus 14%, respectively) (P < 0.05, Z test).

FIG. 1.

Gel of REP-PCR products from various clinical isolates. Lanes 1 and 8 represent molecular size markers (Sigma, St. Louis, Mo.). Lanes 2 to 7 (pattern A) were confirmed as P. multocida subsp. septica by 16S rDNA sequence. In contrast lanes 9 to 18 (pattern B) were demonstrated to be P. multocida subsp. multocida. The double bands marked by arrows are between approximately 1,600 and 2,000 bp in size. The asterisk denotes the band migrating slightly below the 1,400-bp marker.

FIG. 2.

Neighbor-joining tree of P. multocida clinical isolates based on their 16S rDNA sequences. The isolates (those designated with a number) are grouped with either P. multocida subsp. multocida or P. multocida subsp. septica based on their 16S rDNA sequence similarity. Type strains are noted by their full genus and species name and are ATCC 43137, ATCC 19427, and ATCC 29977 for P. multocida subsp. multocida, P. multocida subsp. septica, and P. multocida subsp. gallicida, respectively. Escherichia coli is the outgroup.