Subclinical Mastitis in Selected Bovine Dairy Herds in North Upper Egypt: Assessment of Prevalence, Causative Bacterial Pathogens, Antimicrobial Resistance and Virulence-Associated Genes

Ahmed H Abed; Ahmed M S Menshawy; Mohamed M A Zeinhom; Delower Hossain; Eman Khalifa; Gamal Wareth; Mohamed F Awad

doi:10.3390/microorganisms9061175

Subclinical Mastitis in Selected Bovine Dairy Herds in North Upper Egypt: Assessment of Prevalence, Causative Bacterial Pathogens, Antimicrobial Resistance and Virulence-Associated Genes

Microorganisms. 2021 May 29;9(6):1175. doi: 10.3390/microorganisms9061175.

Authors

Ahmed H Abed¹, Ahmed M S Menshawy², Mohamed M A Zeinhom³, Delower Hossain⁴, Eman Khalifa⁵, Gamal Wareth^{6

7}, Mohamed F Awad⁸

Affiliations

¹ Bacteriology, Mycology and Immunology Department, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef 62511, Egypt.
² Department of Veterinary Medicine (Infectious Diseases), Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef 62511, Egypt.
³ Food Hygiene and Control Department, Faculty of Veterinary Medicine, Beni-Suef University, Beni-Suef 62511, Egypt.
⁴ Department of Medicine and Public Health, Faculty of Animal Science and Veterinary Medicine, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka 1207, Bangladesh.
⁵ Department of Microbiology, Faculty of Veterinary Medicine, Matrouh University, Matrouh 51511, Egypt.
⁶ Friedrich-Loeffler-Institut, Institute of Bacterial Infections and Zoonoses, Naumburger Str. 96a, 07743 Jena, Germany.
⁷ Faculty of Veterinary Medicine, Benha University, Moshtohor, Toukh 13736, Egypt.
⁸ Department of Biology, College of Science, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia.

Abstract

Mastitis is a significant disease affecting dairy cattle farms in Egypt. The current study aimed to investigate the prevalence and major bacterial pathogens causing subclinical mastitis (SCM) in three bovine dairy herds, with a history of SCM, at three Governorates in North Upper Egypt. The antimicrobial resistance profiles and specific virulence-associated genes causing bovine SCM were investigated. One thousand sixty-quarter milk samples (QMS) were collected aseptically from 270 apparently healthy cows in three farms and examined. The total prevalence of SCM was 46% and 44.8% based on California Mastitis Test (CMT) and Somatic Cell Count (SCC), respectively. Bacteriological examination of CMT positive quarters revealed that the prevalence of bacterial isolation in subclinically mastitic quarters was 90.4% (26 and 64.3% had single and mixed isolates, respectively). The most frequent bacterial isolates were E. coli (49.8%), Staphylococcus aureus (44.9%), streptococci (44.1%) and non-aureus staphylococci (NAS) (37.1%). Antimicrobial susceptibility testing of isolates revealed a high degree of resistance to the most commonly used antimicrobial compound in human and veterinary medicine. Implementation of PCR revealed the presence of mecA and blaZ genes in 60% and 46.7% of S. aureus isolates and in 26.7% and 53.3% of NAS, respectively. Meanwhile 73.3% of streptococci isolates harbored aph(3')-IIIa gene conferring resistance to aminoglycosides and cfb gene. All E. coli isolates harbored tetA gene conferring resistance to tetracycline and sul1 gene conferring resistance to sulfonamides. The fimH and tsh genes were found in 80% and 60%, respectively. A significant association between the phenotypes and genotypes of AMR in different bacteria was recorded. The presence of a high prevalence of SCM in dairy animals impacts milk production and milk quality. The coexistence of pathogenic bacteria in milk is alarming, threatens human health and has a public health significance. Herd health improvement interventions are required to protect human health and society.

Keywords: E. coli; Egypt1; NAS; Staphylococcus aureus; Streptococci; antimicrobial resistance; subclinical mastitis; virulence genes.

Grants and funding

TURSP -2020/111/Taif University