Methicillin and vancomycin resistant isolates of Staphylococcus aureus and Enterococcus faecalis recovered from bovine mastitis

Abstract

Mastitis is the most costly disease in the dairy industry. Selecting the proper antibiotic treatment is beneficial for economic and avoids the emergence of antimicrobial resistance. The objective of the present study was to investigate the prevalence of methicillin and vancomycin resistant isolates of mastitis-causing Staphylococcus aureus and Enterococcus faecalis as a probable source of transferable vancomycin resistance to staphylococci. A total of sixty-one Staphylococcus aureus and eight Enterococcusfaecalis isolates were investigated for genotypic and phenotypic antimicrobial resistance.Presence of the mecA, vanA and vanBgenes were surveyed by PCR. The MIC (Minimum Inhibitory Concentration) of vancomycin was determined bybroth microdilution test for all the isolates.Moreover, the antibiotic resistance patterns of the isolates to the most common classes of antibiotics used in dairy cattle such as β-lactam, macrolides and tetracyclines were determinedusing the disk diffusion method. Among Staphylococcus aureus isolates, one MRSA (methicillin-resistant Staphylococcus aureus) isolate was detected while 47.5% of isolates were detected as multidrug-resistant. Furthermore, no phenotypic and genotypicvancomycin-resistance Staphylococcus aureus was found. Most of the Enterococcus faecalis isolates (6/8) showed high MIC for vancomycin (in the range of 128- 1024 μg/ml) and one vanA-type Enterococcus faecalis was observed. This study indicates thatsince the source of transferable resistance to vancomycin exists in dairy farms, there is a potential for emerging and spreading VRSA (vancomycin-resistant Staphylococcus aureus) in dairy cattle which is a risk to animal and human health.

Identification of Methicillin-Resistant Staphylococcus aureus in poultry meat portions using Multiplex PCR

“…S. aureus in bovine and poultry isolates exhibiting diverse genotypes could give rise to a distinctive form of infection (9,33). There was a notable correlation between the expression of methicillin resistance at the phenotypic level and the detection of the mecA gene at the genotypic level (10,34).…”

“…Among the isolates, 14 (82.3%) tested positive for mecA genes. In 2023, Khoramian and Razmyar conducted isolation and identification of S. aureus using conventional methods, which were later confirmed through PCR (9). Out of the 220 isolates identified using later agglutination in Rao et al (2022), 217 were verified as S. aureus through PCR targeting the nuc gene, with 21.4% testing positive for the mecA gene (23).…”

“…Antibiotics are potent drugs against infectious diseases and have tremendously improved effects on health care around the world and saved millions of lives. (9). The presence of antimicrobial drug resistance (AMR) in food constitutes a widespread concern with a direct threat to public health and global relevance to overall animal health, especially livestock (10)(11)(12).…”