Effects of bovine subclinical mastitis caused by Corynebacterium spp. on somatic cell count, milk yield and composition by comparing contralateral quarters.

Subclinical mastitis caused by Corynebacterium spp. (as a group and at the species level) was investigated by evaluating contralateral (healthy and infected) mammary quarters for somatic cell count (SCC), milk yield and composition. Selection of cows with subclinical mastitis caused by Corynebacterium spp. was performed by microbiological culture of composite samples collected from 1242 dairy cows from 21 dairy herds. For each of the selected cows, milk yield was measured and milk samples were collected at the mammary quarter level (i.e., 1140 mammary samples collected from 285 cows) for analysis of milk composition and SCC. The identification of Corynebacterium spp. isolates was performed by 16S rRNA gene sequencing. One hundred and eighty Corynebacterium spp. isolates were identified, of which 167 (92.77%) were C.bovis and eight (4.44%) non-C.bovis; for five of the Corynebacterium spp. isolates (2.77%), sequencing of 16S rRNA genes did not allow identification at the species level. Mammary quarters infected with Corynebacterium spp. as a group had a higher geometric mean SCC (197,900 cells/mL) than healthy contralateral mammary quarters (85,800 cells/mL). Species of Corynebacterium non-C.bovis were infrequently isolated and did not change SCC, milk yield or milk solid contents when evaluated at the contralateral quarter level. Although C.bovis infection showed no effect on milk yield, fat, protein, casein or total solids in milk, it increased SCC and decreased lactose and milk solids non-fat content.

Prevalência e Susceptibilidade Antimicrobiana de Patógenos Causadores de Mastite em Rebanhos Leiteiros / Prevalence and antimicrobial susceptibility of pathogens causing mastitis in dairy herds

Os objetivos do presente estudo foram: a) avaliar a frequência de isolamentos de patógenos causadores de mastite em rebanhos leiteiros comerciais; b) determinar a susceptibilidade antimicrobiana de Staphylococcus spp. e Streptococcus spp. isolados de casos de mastite subclínica c) avaliar o perfil de multirresistência de Staphylococcus spp. e Streptococcus spp. d) Detectar o gene mecA em Staphylococcus spp. resistentes a oxacilina/meticilina; e) avaliar a associação entre as práticas de manejo e tratamento de mastite e a susceptibilidade antimicrobiana de Staphylococcus aureus isolados de rebanhos leiteiros. Foram selecionados para o presente estudo 13 rebanhos leiteiros a partir de um total de 60 rebanhos vinculados a um laticínio da região de Pirassununga/SP. Questionários previamente formulados foram respondidos pelos responsáveis do rebanho para avaliar a associação entre as práticas de manejo e tratamento de mastite e a susceptibilidade antimicrobiana de S. aureus. [...] Os testes de susceptibilidade realizados para as espécies de Staphylococcus spp. e Streptococcus spp. apresentaram alta susceptibilidade para a maioria dos antimicrobianos testados. Com exceção de Streptococcus agalactiae para ampicilina e sulfatrimetropin e os isolados de S. dysgalactiae para tetraciclina e clindamicina. A maioria dos Staphylococcus spp. e Streptococcus spp. não apresentaram perfil de multirresistência. Nenhum dos isolados de Staphylococcus spp. fenotipicamente resistentes a oxacilina/meticilina apresentaram o gene mecA. O maior fator de risco associado à susceptibilidade de S. aureus foi em relação à tetraciclina, penicilina, eritromicina e ampicilina para o não envio de amostras para cultura e antibiograma. Dois fatores de risco importantes identificados foram relacionados à ampicilina, ceftiofur, gentamicina, oxacilina e penicilina para o tratamento de mastite clínica e à enrofloxacina e tetraciclina para o tratamento de vaca seca

The aims of this study were: a) to evaluate the frequency of mastitis pathogens in commercial dairy herds, b) to determine the antimicrobial susceptibility of Staphylococcus spp. and Streptococcus spp. isolated from subclinical mastitis c) to evaluate the profile of multidrug resistance of Staphylococcus spp. and Streptococcus spp. d) to detect the mecA gene in Staphylococcus spp. resistant to oxacillin / methicillin, e) to evaluate the association between management practices and treatment of mastitis, and antimicrobial susceptibility of Staphylococcus aureus isolates from dairy herds. Thirteen dairy herds were selected from a total of 60 dairy farms in the region of Pirassununga / SP. Questionnaires formulated previously were answered by dairy farmers to evaluate the association between mastitis treatment practices and antimicrobial susceptibility. [...] The susceptibility tests performed for the species of Staphylococcus spp. and Streptococcus spp. showed high susceptibility to most antimicrobials tested. With the exception of Streptococcus agalactiae to ampicillin and sulfatrimetropin and isolates of S. dysgalactiae to tetracycline and clindamycin. Most Staphylococcus spp. and Streptococcus spp. did not show multidrug resistance profile. None of Staphylococcus spp. phenotypically resistant to oxacillin / methicillin showed the mecA gene. The major risk factor associated with susceptibility of S. aureus to tetracycline, penicillin, erythromycin and ampicillin was not sending samples for culture and sensitivity. Two important risk factors have been identified related to ampicillin, ceftiofur, gentamicin, penicillin and oxacillin for treatment of clinical mastitis and enrofloxacin and tetracycline for the treatment of dry cow dry cow therapy