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

(.) and () 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 and 15 . 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, 1, and 2 for and , respectively. The results show that 29 (87.9%) and 15 (100%) isolates were positive for the corresponding universal gene. The results of serotyping indicate that 86.2% of isolates belonged to serotype B:2, while 13.8% were untyped. Meanwhile, 60% and 40% of isolates belonged to serotype 2 and serotype 1, respectively. Investigation of virulence-associated genes showed that all the tested isolates harbored B, 87, and A genes. Four isolates harbored both and C genes and of these, three isolates harbored the gene. Sequencing of A gene of and C gene of in the current strains indicated a great homology with strains uploaded in gene banks from different hosts and localities worldwide.