Mastitis pathogens in goats and sheep in the Republic of Croatia and their sensitivity to antimicrobials

This paper outlines the results of researching the incidence of mastitis in small ruminants in the Republic of Croatia over a six-year period (2017 to 2022). During this period, microbiological testing was performed on 801 samples of udder secretions from small ruminants in 13 counties and the city of Zagreb, with 178 samples (22.2%) testing positive for mastitis pathogens. Of the total 609 udder secretion samples from goats, mastitis agents were isolated from 150 samples (24.6%), while the 192 udder secretion samples from sheep revealed 28 (14.6%) contained mastitis agents. The highest prevalence of mastitis pathogens in goat udder secretions was found in 2018 (31.8%), and in sheep in 2020 (32.9%). Microbiological testing identified 16 species and genera of bacteria. The most common species were Staphylococcus aureus, isolated from 96 (53.9%) samples, Staphylococcusspp. (46 samples; 25.8%), Streptococcus spp. (7; 3.9%), Klebsiella spp. and Corynebacterium spp. (each 5; 2.8%), Escherichia coli (4; 2.2%), Streptococcus uberis and Proteus spp. (each 3; 1.7%), and Pseudomonas spp. (2; 1.1%). Other species and genera, such as Streptococcus agalactiae, Streptococcus dysgalactiae, Pasteurella spp., Mannheimia haemolytica, Enterococcus spp., Enterobacter and Serratia spp. were isolated sporadically, each from one sample. The isolated bacterial cultures were tested for sensitivity to antimicrobials using the disc-diffusion method to amoxicillin with clavulanic acid, ampicillin, cefaperazone, enrofloxacin, kanamycin, cloxacillin, lincomycin, neomycin, novobiocin, penicillin, streptomycin, sulfamethoxazole withtrimethoprim, and tetracycline. Sensitivity of the isolated agents to the antimicrobials was most pronounced towards cefoperazone and enrofloxacin, regardless of the species or genera of the isolated mastitis agent. The odds of isolating a mastitis agent from goat udder secretions was 1.61 times higher than for sheep (P<0.05). This study confirmed that the occurrenceof mastitis in small ruminants in Croatia is comparable to incidences reported in other Mediterranean countries.