Identification and antimicrobial resistance profile of Enterobacterales and Staphylococcus spp. isolated from...

Area of Science:

• Veterinary Microbiology
• Food Safety
• Antimicrobial Resistance

Background:

• Subclinical mastitis (SCM) in dairy cows affects milk quality and herd health.
• Raw milk cheese production relies on milk free from resistant pathogens.
• Enterobacterales and Staphylococcus spp. are common causes of bovine mastitis.

Purpose of the Study:

• To identify and evaluate the antimicrobial resistance profile of Enterobacterales and Staphylococcus spp. in raw milk from subclinical mastitis (SCM) cases.
• To investigate bacterial isolates from three dairy farms in Rio de Janeiro supplying raw milk for cheese production.
• To assess the prevalence of specific resistant strains, including MRSA.

Main Methods:

• California Mastitis Test (CMT) for SCM detection.
• Isolation and identification of bacterial strains using Compact-Dry media and MALDI-TOF MS.
• Antimicrobial resistance evaluation via disk diffusion test.

Main Results:

• SCM was detected in mammary quarters across all three farms.
• Staphylococcus aureus was the predominant species on farms A and B.
• Enterobacter roggenkampii was identified for the first time in SCMM and was prevalent on farm C.
• Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin-resistant Staphylococcus chromogenes (MRS) were isolated from farms A and B.

Conclusions:

• The presence of MRSA and MRS in raw milk poses a significant risk to dairy herd health and public health.
• Effective control strategies for resistant bacteria, particularly MRSA/MRS, are crucial for dairy farming.
• Continuous monitoring of antimicrobial resistance in dairy herds is essential for food safety.