PCR analysis of Pasteurella multocida isolates from an outbreak of pasteurellosis in Indian pigs

Pathology, virulence-associated gene profiling, antimicrobial susceptibility, and pathogenicity of untypeable capsular serotypes of Pasteurella multocida isolated from slaughtered pigs of India

Pasteurella multocida is widely distributed in all pig-rearing countries, affecting the economic viability and profitability of pig production. The present research highlights the molecular characterization and pathology of untypeable capsular serotypes of P. multocida in slaughtered pigs from prominent pig-rearing states of India. The prevalence of Pasteurellosis was 27.17% by Pasteurella multocida specific Pasteurella multocida specific PCR (PM-PCR). assay, while isolation rate was 7.62%. The microscopic lesions of bronchopneumonia, tonsillitis, and the presence of bacterial antigens in immunohistochemistry confirmed P. multocida with pathologies. In capsular typing, the majority of the isolates were untypeable with prevalence of 52.15% and 43.58% in molecular and microbiological methods, respectively. All the isolates showed the uniform distribution of virulence genes such as exbB, nanB, sodC, plpB, and oma87 (100%), while the variations were observed in ptfA, hasR, ptfA, pfhA, hsf-1, and plpE genes. The untypeable isolates showed higher prevalence of hsf-1 gene as compared to others. The untypeable serotypes showed a higher degree of resistance to ampicillin, amoxicillin, and penicillin antibiotics. The mouse pathogenicity testing of untypeable capsular isolates confirmed its pathogenic potential. The higher frequency of pathogenic untypeable isolates with antibiotic resistance profile might pose a serious threat to the pigs, and therefore, preventive measures should be adopted for effective control.

Localization of Pasteurella multocida antigens in the brains of pigs naturally infected with Pasteurellosis revealing a newer aspect of pathogenesis

Pasteurella multocida is an economically important respiratory pathogen of pigs confronting swine industry worldwide. Despite extensive research over the decades, its pathogenesis is still poorly understood. Recent reports have demonstrated the nervous system affection as a newer aspect of pathogenesis by Pasteurella multocida type B:2 in Haemorrhagic Septicemia, but there are no reports of the involvement of nervous system by P. multocida in pigs. Therefore, the study was aimed to explore the neurovirulence of Pasteurella multocida in naturally infected pigs. A total of 15 brains were collected from the natural cases of pig mortality suggestive of Pasteurellosis. Grossly, the leptomeninges were markedly congested and brains were oedematously swollen. Histologically, there was moderate to severe fibrinohaemorrhagic and mononuclear cells exudates present in the leptomeningeal tissue and cerebrospinal spaces. Similar vascular inflammatory lesions (perivascular and perineuronal) along with gliosis, neuronal degeneration and necrosis were noted in various subanatomical sites of the brain (cerebrum, cerebellum, brainstem and spinal cord). The culture and biochemical tests showed the presence of P. multocida within the brain tissue. P. multocida type specific antibody staining in the brain tissues revealed intense distribution of antigens in the inflammatory exudates of meningeal vessels, neurons, glial cells and endothelial cells of the blood vessels contributing its association with neuropathological lesions. Pasteurella multocida specific PCR amplification of capsular polysaccharide gene yielded 460 bp and multiplex PCR showed the involvement of capsular serogroups A &D. All the isolates showed the presence of 10 genes for virulence factors. The disease confirmation of both serotypes was proven by Koch's postulates using Swiss albino mice. Further, histopathological brain lesions along with the immunohistochemical detection of bacterial antigens were corroborated with natural cases of P. multocida as described above. To the best of our knowledge, we first time report the neuroinvasion of P. multocida in naturally infected pigs.

Virulence gene profiling of porcine Pasteurella multocida isolates of Assam

Aim:

The present study was conducted to detect and identify the virulence genes in Pasteurella multocida isolates of porcine origin from Assam.

Materials and Methods:

A total of 21 porcine P. multocida isolates were subjected to capsular typing and detection of virulence-associated genes (pfhA, tbpA, hgbB, toxA, oma87, ompH, and nanB) using various polymerase chain reaction (PCR) methods reported elsewhere. Further, pathogenicity of the porcine isolates of P. multocida was studied in mice. For each strain of P. multocida selected for pathogenicity trial, the group of mice was injected intraperitoneally (i/p) with 0.1 ml of the inoculum prepared from respective field isolates, containing 10⁹ organisms per ml.

Results:

Capsular typing of the isolates by multiplex PCR showed two capsular types, type A (66.66%) and type D (33.33%). All the isolates were positive for outer membrane protein genes, oma87 and ompH genes. Iron acquisition genes, tbpA and hgbB, were detected in 14.28% and 19.04% of the isolates. The dermonecrotoxin encoding gene, toxA, was present in 23.80% of the isolates. Filamentous hemagglutinin encoding gene, pfhA, was detected in 28.57%. The virulence gene distribution pattern of the isolates indicates the important role of the genes in disease pathogenesis.

Conclusion:

From the present study, it can be concluded that toxA gene is an important marker gene for defining the pathogenic potential of P. multocida strains in swine.

Integrated pharmacokinetic-Pharmacodynamic (PK/PD) model to evaluate the in vivo antimicrobial activity of Marbofloxacin against Pasteurella multocida in piglets

Background

Marbofloxacin is a veterinary fluoroquinolone with high activity against Pasteurella multocida. We evaluated it’s in vivo activity against P. multocida based on in vivo time-kill data in swine using a tissue-cage model. A series of dosages ranging from 0.15 to 2.5 mg/kg were administered intramuscularly after challenge with P. multocida type B, serotype 2.

Results

The ratio of the 24 h area under the concentration-time curve divided by the minimum inhibitory concentration (AUC₂₄TCF/MIC) was the best PK/PD index correlated with the in vivo antibacterial effectiveness of marbofloxacin (R2 = 0.9279). The AUC₂₄TCF/MIC necessary to achieve a 1-log₁₀ CFU/ml reduction and a 3-log₁₀ CFU/ml (90% of the maximum response) reduction as calculated by an inhibitory sigmoid E_max model were 13.48 h and 57.70 h, respectively.

Conclusions

Marbofloxacin is adequate for the treatment of swine infected with P. multocida. The tissue-cage model played a significant role in achieving these PK/PD results.

Development of a novel multiplex PCR assay for rapid detection of virulence associated genes of Pasteurella multocida from pigs

As the pathogenicity of Pasteurella multocida is associated with various virulence factors (VFs), the aim of the study was to develop a novel multiplex PCR (m-PCR) assay for the rapid detection of important virulence associated genes (VAGs) of P. multocida isolates from pigs. The target recognized VFs used in the study were diverse adhesins (ptfA and pfhA), toxins (toxA), siderophores (tonB and hgbA), sialidases (nanB, nanH) and outer membrane proteins (ompA, ompH, oma87 and plpB). The primers for the genes encoding these VFs were designed by primer3 software (http://bioinfo.ut.ee/primer3-0.4.0/) using gene sequences available in Genbank. The detection limit of the developed assay was 10(2)  CFU ml(-1) . The m-PCR did not produce any nonspecific amplification products when tested against Bordetella bronchiseptica which also commonly infects pigs. We applied m-PCR to the field samples, and the results obtained were the same as the single PCR results. The developed assay would be very useful for veterinary diagnostic laboratories and for others interested in the rapid virulence profiling of porcine P. multocida isolates circulating in the piggeries.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study reports the development and evaluation of a novel multiplex PCR assay for the rapid detection of 11 important VAGs of Pasteurella multocida isolates from pigs. Rapid and simultaneous detection of recognized VFs of the organism are essential to know the virulo-types of P. multocida isolates circulating in the piggeries. The developed novel assay will be very useful for the rapid detection of VAGs of P. multocida isolates from pigs.

Molecular Epidemiology of Pasteurella multocida Circulating in India by Multilocus Sequence Typing

Multilocus sequence typing (MLST), a sequence-based typing method for bacterial pathogens, is currently the best method for long-term epidemiological study and to understand the population structure of the bacteria. This investigation was carried out to study the diversity of Pasteurella multocida isolates circulating in India. Ten different sequence types (ST) identified in this study are ST 122 from cattle, goat, mithun and pig; ST 50 from pig; ST 9 from cattle and sheep; ST 229 from cattle and goat; ST 71 and ST 277 from cattle; and ST 129, ST 280, ST 281 and ST 282 from avian species. Of these, ST 277, ST 280, ST 281 and ST 282 were identified for the first time. The analysis of results provides novel epidemiological information on the circulation of multiple STs across India. The majority of STs or their variants identified in this study have already been reported from different parts of the globe. This suggests that probably transboundary spread of strains across countries and continents has occurred across evolutionary time and is still happening. The isolation of ST 122 from small ruminants and pigs suggests that these species may be included in the preventive vaccination policy for effective control of haemorrhagic septicaemia in India.

Fatal outbreak of systemic pasteurellosis in a wild boar (Sus scrofa) population from southwest Spain

Pasteurella multocida is a common pathogen of swine that causes specific diseases with great economic impact. However, the importance of this pathogen in wild boar is still unknown. In the current work, an outbreak of systemic pasteurellosis in wild boar with a high mortality rate is described. A total of 23 wild boar of all ages were found dead over a 5-day period on a game estate in southwest Spain (11.11% mortality). Three animals were necropsied and showed subcutaneous edema, a generalized congestion, and fibrin deposits in the peritoneal cavity. Hemorrhages, general congestion, and intravascular thrombosis were microscopically observed. Pasteurella multocida type B was isolated from all of the studied organs. Outbreaks of systemic pasteurellosis have been described in domestic pigs from Asia and Australia, but not to date in Europe. This outbreak suggests that systemic pasteurellosis affecting wild boar populations may be an important cause of mortality.

Pharmacokinetic/pharmacodynamic relationship of cefquinome against Pasteurella multocida in a tissue-cage model in yellow cattle

The cephalosporin antimicrobial drug cefquinome was administered to yellow cattle intravenously (i.v.) and intramuscularly (i.m.) at a dose of 1 mg/kg of body weight in a two-period crossover study. The pharmacokinetic (PK) properties of cefquinome in serum, inflamed tissue-cage fluid (exudate), and noninflamed tissue-cage fluid (transudate) were studied using a tissue-cage model. The in vitro and ex vivo activities of cefquinome in serum, exudate, and transudate against a pathogenic strain of Pasteurella multocida (P. multocida) were determined. A concentration-independent antimicrobial activity of cefquinome was confirmed for levels lower than 4 × MIC. Integration of in vivo pharmacokinetic data with the in vitro MIC provided mean values for the time that drug levels remain above the MIC (T > MIC) in serum was 14.10 h after intravenous and 14.46 h after intramuscular dosing, indicating a likely high level of effectiveness in clinical infections caused by P. multocida of MIC 0.04 μg/mL or less. These data may be used as a rational basis for setting dosing schedules, which optimize clinical efficacy and minimize the opportunities for emergence of resistant organisms.

Pharmacokinetic/pharmacodynamic relationship of marbofloxacin against Pasteurella multocida in a tissue-cage model in yellow cattle

The fluoroquinolone antimicrobial drug marbofloxacin was administered to yellow cattle intravenously and intramuscularly at a dose of 2 mg/kg of body weight in a two-period crossover study. The pharmacokinetic properties of marbofloxacin in serum, inflamed tissue-cage fluid (exudate), and noninflamed tissue-cage fluid (transudate) were studied by using a tissue-cage model. The in vitro and ex vivo activities of marbofloxacin in serum, exudate, and transudate against a pathogenic strain of Pasteurella multocida (P. multocida) were determined. Integration of in vivo pharmacokinetic data with the in vitro MIC provided mean values for the area under the curve (AUC)/MIC for serum, exudate, and transudate of 155.75, 153.00, and 138.88, respectively, after intravenous dosing and 160.50, 151.00, and 137.63, respectively, after intramuscular dosing. After intramuscular dosing, the maximum concentration/MIC ratios for serum, exudate, and transudate were 21.13, 9.13, and 8.38, respectively. The ex vivo growth inhibition data after intramuscular dosing were fitted to the inhibitory sigmoid Emax equation to provide the values of AUC/MIC required to produce bacteriostasis, bactericidal activity, and elimination of bacteria. The respective values for serum were 17.25, 31.29, and 109.62, and slightly lower values were obtained for transudate and exudate. It is proposed that these findings might be used with MIC50 or MIC90 data to provide a rational approach to the design of dosage schedules which optimize efficacy in respect of bacteriological as well as clinical cures.

Septicaemic pasteurellosis in free-range pigs associated with an unusual biovar 13 of Pasteurella multocida

Biochemical profiles, PFGE typing and MLST analysis were used to investigate an outbreak of septicaemic pasteurellosis in a free-range pig farm in Spain. Signs of coughing, dyspnoea and a visible inflammation of the ventral area of the neck (jowl), which acquired a cyanotic and necrotic appearance, were the characteristic findings in affected animals, associated with a high morbidity (70%) and case mortality (95%). Diffuse, haemorrhagic and fibrinous pleuroneumonia and acute, focally extensive and haemorrhagic myositis and panniculitis were observed in the histopathological analysis from three analyzed animals. Pasteurella multocida subsp. multocida, capsular type B, biovar 13 was isolated in pure culture from lung, submandibular tissue (jowl), liver, spleen and kidney tissue from diseased pigs. After PFGE typing, all P. multocida isolates displayed undistinguishable macrorestriction patterns with Bsp120I restriction enzyme demonstrating that the infection was caused by a single strain. With the multihost P. multocida MLST database, all P. multocida isolates were assigned to the new sequence type ST47 which was highly related with other bovine isolates of P. multocida type B associated with haemorrhagic septicaemia. This is the first description of an outbreak of septicaemic pasteurellosis in free-range pigs associated with P. multocida type B of the unusual biovar 13. The communication and complete diagnosis of cases of swine septicaemia and the possible role of pigs as reservoirs of this new pathogen must be evaluated to determine the importance of this disease for pigs.