Study on the prevalence of Pasteurella multocida carriers in slaughtered cattle and relationship with their immunity status at Ahvaz abattoir

This study was carried out on 250 slaughtered cattle at Ahvaz abattoir in Khouzestan province of Iran to investigate the occurrence of Pasteurella multocida carriers and relationship with their immunity status. Nasopharyngeal swabs and 10 ml blood samples were taken immediately after slaughter. The swabs were streaked on 5% sheep blood agar plates. Cultures were incubated at 37°C for 24h and the plates were examined for colonies resembling P. multocida. Suspicious colonies were further subcultivated and examined microscopically and biochemically. The isolates were serotyped serologically and their pathogenicity in mice was carried out. Sera samples were tested for the presence of antibody against P. multocida by indirect haemagglutination [IHA] test and sera with a titer of >/= 1:16 were considered as positive. P. multocida was isolated from the nasopharynx of 6 [2.4%] out of 247 healthy cattle examined. There was no relation between infection and sex or age. All of 6 isolates belonged to type B. They were pathogenic for mice and caused death in injected mice within less than 24h after injection. Indirect haemagglutination test revealed the titers of >/= 1:16 of P. multocida antibody in 212 [84.8%] cattle. Among 6 cattle recognized as the carriers of P. multocida, 5 were positive serologically and 2, 2 and one of them had titers 1:128, 1:64, and 1:32, respectively

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

Pathogenicity and immunogenicity of native and mutant strains of Pasteurella multocida, the causative agents of haemorrhagic septicaemia

Haemorrhagic septicaemia [HS] is a fatal systemic disease of cattle and buffaloes. Some control is achieved with administration of alum-precipitated or oil-adjuvanted killed whole-cell vaccines injected subcutaneously. These vaccines, however, provide only short-term immunity and for effective use, they should be administered annually. We constructed an aroA attenuated derivative of a Pasteurella multocida serotype B:2 strain by allelic exchange of the native aroA sequence with aroA sequences disrupted with a kanamycin resistance cassette. This strain was confirmed to be aroA mutant by PCR. The aroA derivative was highly attenuated for virulence in a mouse model of HS and rabbits. Mouse and rabbit challenge experiments showed that i.p. or i.m. vaccination of an aroA strain completely protected mice or rabbits against challenge with a high dose [>1000 LD[50]] of the parent strain

Measuring of free endotoxin in alum-precipitated vaccine of haemorrhagic septicaemia by limulus amebocyte lysate test

Haemorrhagic septicaemia [HS] vaccine which is prepared in Razi Institute is used in endemic areas of Iran. Aluminum-hydroxide gel was used as adjuvant for preparing this vaccine. Post-vaccinal shock reactions were the main complaint after use of this vaccine. In a previous study, we could improve the vaccine by alum-precipitation Pasteurella multocida cells and removing the liquid phase. In this study, the amount of free endotoxin in aluminum-hydroxide and alum-HS vaccines was determined. It was found that endotoxin level was considerably decreased from 0.22 EU/ml to 0.03 EU/ml after alum-precipitation