Etiology of Mastitis and Antimicrobial Resistance in Dairy Cattle Farms in the Western Part of Romania

The present study aimed to determine the bacteria isolated from bovine mastitis and their antimicrobial resistance in the western part of Romania. Clinical mastitis was diagnosed based on local inflammation in the udder, changes in milk, and when present, generalized symptoms. Subclinical mastitis was assessed using a rapid test—the California Mastitis Test. The identification of bacterial strains was performed based on biochemical profiles using API system tests (API 20 E, API Staph, API 20 Strep, API Coryne, API 20 NE (bioMerieux, Marcy l’Etoile, France), and MALDI-TOF mass spectrometry (MS). The prevalent isolated bacteria were Staphylococcus spp. (50/116; 43.19%), followed by Streptococcus spp. (26/116; 22.41%), E. coli (16/116; 13.79%), Corynebacterium spp. (9/116; 7.75%), Enterococcus spp. (10/116; 8.62%), and Enterobacter spp. (5/116; 4.31%). Phenotype antimicrobial resistance profiling was performed used the disc diffusion method. Generally, Gram-positive bacteria showed low susceptibility to most of the antimicrobials tested, except cephalothin. Susceptibilities to penicillins and quinolones were fairly high in Gram-negative bacteria, whereas resistance was observed to macrolides, aminoglycosides, and tetracyclines. The highest number of isolates were multidrug resistant (MDR), the resistance pathotypes identified including the most frequently antimicrobials used in cow mastitis treatment in Romania.