Lancefield classification and antimicrobial resistance of hemolytic streptococci isolated from bovine mastitis.

Streptococcal species are known to be responsible for bovine mastitis. The aim of the present study was to determine antimicrobial drug resistance patterns of hemolytic streptococci distributed according to Lancefield serogrouping. Streptococcus sp. strains were isolated from 124 bovine milk samples from 31 cows with subclinical or clinical mastitis submitted to Mehmet Akif Ersoy University Faculty of Veterinary Medicine, Department of Microbiology Laboratory in Burdur province, Turkey from January 2015 to January 2017. A total of 63 Streptococcus sp. were isolated and the most frequently obtained isolates were classified as Lancefield's serogroup B (84.13%), the remaining isolates as serogroup F (15.87%). Out of 63 isolates, 53 (84.13%) showed beta­hemolytic activity whereas 10 (15.87%) alpha­hemolytic activity. Antimicrobial resistance was assessed by disk diffusion test against the most common antibiotics used in the field. Among the 63 Streptococcus sp. tested, the highest antimicrobial resistance patterns were observed for neomycin (95.24%), trimethoprim sulphamethoxazole (87.30%) and gentamicin (69.84%). None of the isolates showed resistance to amoxicillin­clavulanic acid, except for one serogroup F isolate. The resistance rates for the other antimicrobials ranged from 1.59% to 38.04%. A total of 50 isolates exibited multi­drug resistance to ≥ 3 antimicrobial agents tested. Overall, our results suggested that there is an urgent need to enhance awareness among the dairy farmers in choosing the appropriate drug for treating mastitis.

CTX-M-15-Type Extended-Spectrum Beta-Lactamase-Producing Escherichia coli as Causative Agent of Bovine Mastitis.

In the present study, 3 quarter milk samples from 3 cows showing clinical signs of mastitis were investigated. Three Escherichia coli were isolated and were found resistant to ceftiofur and cefquinome. The isolates were detected as extended-spectrum beta-lactamase (ESBL) producers by the Clinical and Laboratory Standards Institute (CLSI) ESBL screening test and combined disc method. CTX-M- and TEM-type beta-lactamase genes (blaCTX-M blaTEM) were detected by polymerase chain reaction in the isolates. Sequencing of blaCTX-M and blaTEM genes showed that the isolates were both TEM-1- and CTX-M-15-type beta-lactamase producers. The isolates were tested by agar disc diffusion test for susceptibility to various classes of antibiotics (aminoglycosides, quinolones, phenicols, folate pathway inhibitors, and tetracyclines), and they were determined as multidrug resistant. Therefore, this is the first report indicating the involvement of multidrug-resistant CTX-M-15-type ESBL-producing E. coli as a cause of bovine mastitis in Turkey.