Serotyping, Genotyping and Virulence Genes Characterization of Pasteurella multocida and Mannheimia haemolytica Isolates Recovered from Pneumonic Cattle Calves in North Upper Egypt.

Ahmed H Abed,Gamal Wareth,Salwa E Salem,Ahmed M S Menshawy,Eman Khalifa,Fawzy R El-Seedy,Hany M Hassan,Ashraf M Nabih

doi:10.3390/vetsci7040174

Abstract

Pasteurella (P.) multocida and Mannheimia (M.) haemolytica are the most two common pathogenic bacterial agents causing pneumonia in calves. Both bacteria are associated with significant economic losses in the cattle industry due to high morbidity and mortality rates, especially in the case of severe infections. The objectives of the present study were to perform serotyping and genotyping, as well as characterization of the virulence-associated genes in 48 bacterial isolates; 33 P. multocida and 15 M. haemolytica. All strains were isolated from pneumonic cattle calves showing respiratory manifestations such as fever, nasal discharges, and rapid breathing in North Upper Egypt governorates (Beni-Suef and El-Fayoum). PCR was applied as a confirmatory test using a specific universal gene, kmt1, and rpt2 for P. multocida and M. haemolytica, respectively. The results show that 29 (87.9%) P. multocida and 15 (100%) M. haemolytica isolates were positive for the corresponding universal gene. The results of serotyping indicate that 86.2% of P. multocida isolates belonged to serotype B:2, while 13.8% were untyped. Meanwhile, 60% and 40% of M. haemolytica isolates belonged to serotype 2 and serotype 1, respectively. Investigation of virulence-associated genes showed that all the tested P. multocida isolates harbored nanB, omp87, and toxA genes. Four M. haemolytica isolates harbored both gcp and lktC genes and of these, three isolates harbored the ssa gene. Sequencing of toxA gene of P. multocida and lktC gene of M. haemolytica in the current strains indicated a great homology with strains uploaded in gene banks from different hosts and localities worldwide.

Highlights

Bovine respiratory disease (BRD) is a significant cause of morbidity and mortality among beef cattle globally
M. haemolytica isolates were positive for the kmt1 and rpt2 universal genes, respectively (Table 4)
Serotyping of rpt2 PCR-positive M. haemolytica isolates (n = 15) revealed that nine isolates (60%) were M. haemolytica serotype 2 (A:2) and six isolates (40%) were serotype 1 (A:1)

Summary

Introduction

Bovine respiratory disease (BRD) is a significant cause of morbidity and mortality among beef cattle globally. 2020, 7, 174 commensal Gram-negative bacteria in the upper respiratory tract of animals, represent the major bacterial causative agents for BRD [1]. Sudden death within 24–36 h with clear clinical signs may be observed. In chronic cases, they may cause permanent lung damage such as fibrosis, adhesions and/or abscesses that are affecting the performance [1]. Pasteurella multocida is a zoonotic bacterium causing hemorrhagic septicaemia (HS), which is a major disease of cattle and buffaloes occurring as catastrophic epizootics in many African and Asian countries characterized by an acute, highly fatal septicemia with high morbidity and mortality [3]. Serious respiratory tract infections including pneumonia, empyema, and lung abscesses are typically found in patients with underlying pulmonary disease

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