Single primer polymerase chain reaction fingerprinting for Pasteurella multocida isolates from laboratory rabbits

Biology and Diseases of Rabbits

Beginning in 1931, an inbred rabbit colony was developed at the Phipps Institute for the Study, Treatment and Prevention of Tuberculosis at the University of Pennsylvania. This colony was used to study natural resistance to infection with tuberculosis (Robertson et al., 1966). Other inbred colonies or well-defined breeding colonies were also developed at the University of Illinois College of Medicine Center for Genetics, the Laboratories of the International Health Division of The Rockefeller Foundation, the University of Utrecht in the Netherlands, and Jackson Laboratories. These colonies were moved or closed in the years to follow. Since 1973, the U.S. Department of Agriculture has reported the total number of certain species of animals used by registered research facilities (1997). In 1973, 447,570 rabbits were used in research. There has been an overall decrease in numbers of rabbits used. This decreasing trend started in the mid-1990s. In 2010, 210,172 rabbits were used in research. Despite the overall drop in the number used in research, the rabbit is still a valuable model and tool for many disciplines.

Comparison of genotypic and phenotypic characterization methods for Pasteurella multocida isolates from fatal cases of bovine respiratory disease

Bovine respiratory disease (BRD) is the most costly disease of beef cattle in North America. Because Pasteurella multocida is a commensal of the upper respiratory tract, it is generally considered an opportunistic pathogen. However, studies in swine indicated that there may be a limited number of strains associated with disease, suggesting that some are more virulent than others. Although this may also be true of isolates from cattle, appropriate typing methods must be established before this possibility can be investigated. The purpose of this study was to compare effectiveness of polymerase chain reaction (PCR) fingerprinting to more traditional approaches for typing bovine P. multocida isolates. Isolates were obtained from 41 cases of fatal BRD and subjected to random amplified polymorphic DNA PCR (RAPD-PCR), whole cell protein (WCP) profiles, outer membrane protein (OMP) profiles, and serotyping. The discrimination index was calculated for each typing method and combinations of each using Simpson's index of diversity. Correlation coefficients were calculated to assess concordance between classification results achieved through genotypic (RAPD-PCR) and phenotypic (WCP, OMP, and serotyping) approaches. All characterization methods were capable of discriminating between isolates. However, there was poor concordance between techniques. There were also few significant associations between typing results and epidemiologic data. Random amplified polymorphic DNA PCR was validated as being a repeatable and reliable means of discriminating between P. multocida isolates obtained from cattle. Isolates obtained from fatal cases of BRD in calves in a commercial feedlot demonstrated significant diversity, justifying additional investigation into whether P. multocida is a strictly opportunistic pathogen in cattle.

Pasteurella multocidaand bovine respiratory disease

Pasteurella multocidais a pathogenic Gram-negative bacterium that has been classified into three subspecies, five capsular serogroups and 16 serotypes.P. multocidaserogroup A isolates are bovine nasopharyngeal commensals, bovine pathogens and common isolates from bovine respiratory disease (BRD), both enzootic calf pneumonia of young dairy calves and shipping fever of weaned, stressed beef cattle.P. multocidaA:3 is the most common serotype isolated from BRD, and these isolates have limited heterogeneity based on outer membrane protein (OMP) profiles and ribotyping. Development ofP. multocida-induced pneumonia is associated with environmental and stress factors such as shipping, co-mingling, and overcrowding as well as concurrent or predisposing viral or bacterial infections. Lung lesions consist of an acute to subacute bronchopneumonia that may or may not have an associated pleuritis. Numerous virulence or potential virulence factors have been described for bovine respiratory isolates including adherence and colonization factors, iron-regulated and acquisition proteins, extracellular enzymes such as neuraminidase, lipopolysaccharide, polysaccharide capsule and a variety of OMPs. Immunity of cattle against respiratory pasteurellosis is poorly understood; however, high serum antibodies to OMPs appear to be important for enhancing resistance to the bacterium. Currently availableP. multocidavaccines for use in cattle are predominately traditional bacterins and a live streptomycin-dependent mutant. The field efficacy of these vaccines is not well documented in the literature.

Molecular characterization of Avian strains of Pasteurella multocida serogroup-A:1 based on amplification of repetitive regions by PCR

Repetitive extragenic palindromic (REP)-PCR (polymerase chain reaction), enterobacterial repetitive intergenic consensus (ERIC)-PCR, and single primer PCR assays were employed to characterize 66 strains of Pasteurella multocida serogroup A:1 isolated from avian species belonging to different regions of India. REP-PCR resulted in amplification of REP sequences from the genome which were in the range of approximately 200 to approximately 3000 bp and accounted for a total of 54 distinguishing profiles (D=0.99). ERIC-PCR analysis also generated amplified products in the range of approximately 200 to approximately 3200 bp categorizing strains into a total of 50 different profiles (D=0.98). Amplification of repetitive regions using a microsatellite primer (GTG)(5), resulted in clear distinctive bands ranging from approximately 200 to approximately 2400 bp. Strains were assigned to 43 profiles (D=0.96). No correlation could be drawn between genotypic profiles and avian hosts with their geographical area of origin. Avian strains of P. multocida serogroup A:1 were found to be highly heterogeneous with diverse profiles. REP-PCR was found to be highly discriminatory and simple method for differentiation of phenotypically similar strains. The present study also indicated that PCR based amplification of repetitive regions of P. multocida is a rapid technique with good discrimination and could be employed directly for routine typing of field isolates from fowl cholera outbreaks.

Detection of multiple strains ofPasteurella multocidain fowl cholera outbreaks by polymerase chain reaction-based typing

Applicability of molecular methods for the detection and differentiation of Pasteurella multocida strains involved in two separate fowl cholera outbreaks in a single poultry farm was investigated. A total of 12 and 18 strains of P. multocida obtained from two separate outbreaks were subjected to phenotypic and genotypic characterization. Phenotypically, all strains were similar; however, DNA-based techniques by employing polymerase chain reaction (PCR) assays were found to be highly specific and sensitive for rapid detection and differentiation of strains. All 30 strains gave amplicons of approximately 460 bp and approximately 1,044 bp specific for P. multocida and capsular serogroup A in the Multiplex Capsular PCR typing system. Molecular typing techniques such as repetitive extragenic palindromic PCR, enterobacterial repetitive intergenic consensus PCR and single primer PCR differentiated all 30 strains into different profiles. However, similar patterns of genome fragments were observed among all strains following restriction endonuclease analysis using the enzyme HpaII. The current investigation revealed involvement of the same and multiple strains of P. multocida in two outbreaks. The results also indicated that molecular methods of detection and typing are rapid in comparison with conventional methods for epidemiological investigations of fowl cholera outbreaks.

Molecular variability among strains of Pasteurella multocida isolated from an outbreak of haemorrhagic septicaemia in India

The applicability of conventional and molecular methods for rapid detection and differentiation of Pasteurella multocida serogroup B isolates involved in an outbreak of haemorrhagic septicaemia affecting Indian buffaloes, was studied. Five isolates were obtained and were subjected to phenotypic and genotypic characterization. None of the five isolates could be differentiated on the basis of cultural, biochemical, pathogenicity and antimicrobial sensitivity patterns. Polymerase chain reaction (PCR)-based techniques were found to be specific and sensitive for rapid detection and differentiation of isolates. Repetitive extragenic palindromic (REP-) PCR, enterobacterial repetitive intergenic consensus (ERIC-) PCR and single-primer PCR differentiated all the five isolates into different profiles. All the isolates involved in the outbreak were found to have a genetic profile different from standard P. multocida strain (P52). However, three isolates had similar profiles, whereas each of the remaining two had a different profile. The study indicates the involvement of multiple strains of P. multocida in a single outbreak of haemorrhagic septicaemia in buffaloes. The results also indicate that molecular methods of detection and typing are superior to conventional methods for rapid epidemiological investigations of haemorrhagic septicaemia.