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.

A total of 150 samples of raw milk, 75 each of farm and market milk were collected from different farms and supermarkets in Beni-Suef Governorate, in addition to 30 stool samples from milk handlers and 25 milker's hand swabs were examined for the presence of Escherichia coli, E. coli O157:H7, Salmonella, Aeromonas and Yersinia. Isolates were identified biochemically and serologically. The obtained results revealed that E. coli was detected in a percentage of 26.7% and 16% in the examined raw market and bulk farm milk respectively, while in stool and hand swabs samples were 16.6% and 16%, respectively. E. coli O157:H7 and Salmonella spp. failed to be detected in any of the examined samples. Additionally, 45% and 16.7% of the recovered E. coli strains from the examined raw market and farm milk samples were enteropathogenic O166, while 55% and 83.3 were untypable, respectively. On the other hand 60% of human stool samples isolates were O 148 and 40% of the isolates were untypable, while 100% of the hand swab isolates were untypable. The results also exhibits isolation rate of Aeromonas hydrophila in a percentage of 24%, 13.3%, 10% and 16% from market milk, farm milk samples, stool and hand swabs respectively. While Yersinea enterocolitica represent 3.3% in the stool samples only. The public health significance of isolated strains as well as suggested control measures were discussed