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.

Methicillin and aminoglycoside resistance in Staphylococcus aureus isolates from bovine mastitis and sequence analysis of their mecA genes.

Although methicillin-resistant Staphylococcus aureus (MRSA) were generally isolated from human beings; these agents were recently isolated from various animal species. It has been shown that MRSA isolates are not only resistant to beta-lactam antibiotics, but can also be resistant to the other commonly used antibiotics. In this study, 18 phenotypic methicillin resistant S. aureus isolates from bovine mastitis cases were analyzed by PCR for the presence of mecA gene encoding methicillin resistance and aac (6')/aph(2″), aph(3')-IIIa and ant(4')-Ia genes encoding aminoglycoside resistance. Out of 18 S. aureus isolates (oxacillin MICs, ≥4 µg/ml), 3 were positive for mecA gene. Only one from 3 mecA positive isolates was positive for genes encoding aminoglycoside-modifying enzymes and this isolate carried aac(6')/aph(2″) in combination with aph(3')-IIIa gene. The aph(3')-IIIa gene was detected in 3 isolates. These three isolates carrying the aminoglycoside-modifying enzyme genes were resistant to gentamicin, kanamycin and neomycin. The mecA gene of 3 MRSA isolates was sequenced. All three mecA genes of these isolates were identical to that found in human MRSA strains, except a one-base substitution at nucleotide position 757. From the data presented in this study, it can be concluded that MRSA isolated from bovine mastitis may be originated from human beings, but further studies are needed to investigate the possibility of zoonotic transfer of MRSA.

Clinical and immunological effects of Newcastle disease virus vaccine on bovine papillomatosis.

Newcastle disease virus (NDV) has antineoplastic and immunostimulatory properties, and it is currently being clinically tested in anticancer therapy. In order to analyze the immunostimulatory effects of NDV on bovine papillomatosis, we inoculated 14 cows subcutaneously with an attenuated vaccine containing the LaSota strain of NDV (LS-NDV). Four cows with papillomatosis served as controls. Serum samples were collected from each animal 1 h before and, 7 and 21 days after inoculation. In inoculated cows, on days 7 and 21 the mean antibody titers were log2 2.43 +/- 0.92 and log2 5.57 +/- 0.72 by haemagglutination inhibition (HI), and the mean levels of tumor necrosis factor-alpha (TNF-alpha) were 5.80 +/- 4.19 and 5.39 +/- 2.66 ng/ml by WEHI-164 cytotoxicity assay. Significant differences between inoculated and control animals were evident for antibody titers on day 21 and clinical scores on day 60. A correlation was evident between the TNF-alpha activities and clinical scores on day 21. The clinical observations at day 60 showed that the papillomas in five cows were completely resolved (36%), one animal had no alterations on clinical appearance of the tumor (7%), and papillomas in eight cows were regressed (57%). In conclusion, these results demonstrated that inoculation of LS-NDV vaccine stimulates an antibody response and limited increase in TNF-alpha activity and may enhance clinical recovery in bovine papillomatosis.