Plasmid profile of avian strains of Pasteurella multocida

Abstract

Four isolates of P. multocida (DCl, DC2, FCl and FC2) from avian species (chicken and ducks) were subj ected to various typing methods like biotyping, antibiogram and plasmid profiling. The pathogenicity of the isolates was also ascertained in mice, rabbits chicken and ducks. By biotyping, the isolates were found to belong to two subspecies P. mul tocida subsp. mul tocida and P. mul t.oc i cie subsp. septica. All the isolates fermented xylose and none of them fermented dulcitol. Antibiogram of the isolates was carried out and they wer~ found to be resistant to furazolidone, metronidazole anC nalidixic acid. Some of the isolates are also resistant tc sulpha and trimethoprim. All the isolates were pathogenic to mice on rip injection. Duck isolates (DCl and DC2) were found to be pathogenic to rabbits killing them on fourth and fifth day respectively. The isolates DCl and DC2 were lethal to orally infected chicks within 48 h of administration and P. multocida could e reisolated from these birds. The same isolates killed the SiC injected ducks within 24 and 48 h.

11 The chicken isolates obtained from apparently healthy birds were non pathogenic to rabbits, chicks and ducks. Plasmid profiling revealed the presence of plasmids in three of the four isolates screened. One isolate was plasmid less and another isolate contained five plasmids. The molecular size of the plasmids ranged from 2.69 kb to 7.07 kb. One isolate did not contain plasmids at all. An isolate (FC2) which was not pathogenic to rabbits, chicks and ducks contained plasmids. Isolate FCl which was resistant to six antibiotics did not possess plasmids. Hence plasmids obtained in this study may not be associated with either antibiotic resistance or pathogenicity in experimental animals. A combination of two parameters such as plasmid profile and one of the typing methods, biotyping or antibiogram made it possible to differentiate the isolates. Thus, the plasmid profile analysis with anyone of the typing methods could be used as an epidemiological tool in the differentiation of P. multocida strains of avian origin.