Prevalencia bayesiana de Staphylococcus aureus en vacas lecheras en el Valle del Cauca, Colombia

El Staphylococcus aureus es uno de los principales microorganismos causantes de mastitis subclínica en las vacas lecheras. Determinar la prevalencia del S. aureus se hace necesario en vacas de hatos lecheros grandes y pequeños ubicados en la región norte, centro y sur del departamento del Valle del Cauca, Colombia. Se utilizó la metodología del National Mastitis Council recolectando 1070 muestras de leche de 273 vacas en 17 hatos mediante un muestreo polietápico, durante el periódo 2015 - 2016. Se realizó cultivo con todas las muestras recolectadas independientemente del resultado de la prueba de California mastitis test. Se utilizó el análisis bayesiano de los datos para obtener estimaciones más precisas. La prevalencia bayesiana del patógeno S. aureus en vacas lecheras en el Valle del Cauca fue de 31,94% y se tiene un 95% de probabilidad de que el intervalo (30,03 – 37,62%) contenga el valor de dicha prevalencia. La región Norte, Centro y Sur evidenciaron prevalencias de 33%, 34% y 24% respectivamente. En cuanto al tamaño del hato se evidenció que las vacas de los hatos pequeños presentan mayor prevalencia con 47% que las vacas de los hatos grandes 17% a la presencia del patógeno. La alta prevalencia encontrada en las vacas genera un alto impacto en la salud pública debido a una posible contaminación zoonótica por este patógeno.

Clinical Mastitis Incidence in Dairy Cows Housed on Recycled Manure Solids Bedding: A Canadian Cohort Study

Bedding can affect mammary health of dairy cows. The objectives of this study were to evaluate clinical mastitis incidence in cows housed on recycled manure solids bedding and, more specifically, to determine which pathogens were involved. We followed 26 recycled manure solids farms and 60 straw-bedded farms as a comparative group during 1 year (2018–2019). For each episode of clinical mastitis, defined as a visual alteration of the milk, with or without local or systemic signs of infection, producers sampled aseptically the affected quarter, provided some details about the animal, and sent the sample to the research team at the Université de Montréal. We received and analyzed 1,144 milk samples. The samples were cultured according to the National Mastitis Council guidelines and the different colony phenotypes were subsequently identified with mass spectrometry. In 54.6% of CM cases, a single phenotype of bacteria was cultured (pure culture), while two different phenotypes were found in 16.8% of the samples (mixed culture), and no growth was observed in 14.4% of the samples. Samples with three or more phenotypes were considered contaminated and were not included in the pathogen-specific analyses (14.3% of the submitted samples). The most frequently identified bacterial species in pure and mixed culture in farms using recycled manure solids were Streptococcus uberis (16.0%), Escherichia coli (13.8%), Klebsiella pneumoniae (13.2%), Streptococcus dysgalactiae (6.2%), and Staphylococcus aureus (3.4%). In straw farms, the most frequent species were S. aureus (16.6%), S. uberis (11.0%), E. coli (9.1%), S. dysgalactiae (8.0%), and K. pneumoniae (1.1%). The incidence of clinical mastitis (all cases together) was not higher in recycled manure solids farms (14.0 cases/100 cow-year; 95% CI: 8.3–23.7) compared with straw-bedded farms (16.3 cases/100 cow-year; 95% CI: 9.0–29.6). However, K. pneumoniae clinical mastitis episodes were 7.0 (95% CI: 2.0–24.6) times more frequent in recycled manure solids farms than in straw farms. Adjusted least square means estimates were 1.6 K. pneumoniae clinical mastitis cases/100 cow-year (95% CI: 0.8–3.4) in recycled manure solids farms vs. 0.2 cases/100 cow-year (95% CI: 0.1–0.6) in straw-bedded farms. Klebsiella pneumoniae clinical mastitis is in general severe. Producers interested in this bedding alternative need to be aware of this risk.

FONTES DE CONTAMINAÇÃO E CONTÁGIO DE PROTOTHECA ZOPFII EM PROPRIEDADE LEITEIRA

O trabalho teve como objetivo foi determinar fontes de contaminação e contágio de Prototheca zopfii em propriedade leiteira situada na cidade de Ribeirão do Pinhal, Estado do Paraná. Material e Métodos: foram coletadas 33 amostras com suabe estéril de diferentes locais relacionados à produção leiteira. As amostras foram imersas em meio líquido de infusão de cérebro e coração (BHI) e incubadas sob aerofilia em estufa à 37ºC por 24 horas. Após esse período foram repicadas em meio sólido de BHI adicionado a sangue ovino desfibrinado e novamente incubados nas mesmas condições por 48 a 96 horas. Também foram coletadas amostras de leite de dois animais suspeitos e foram processadas conforme método recomendado pelo National Mastitis Council. As análises positivas no crescimento microbiano, foram identificadas segundo as características macro e microscópicas bioquímicas e tintoriais. Resultados: a alga Prototheca zopfii apresentou-se em 31,4% das amostras, inclusive nas mãos dos responsáveis pela ordenha. Conclusão: esta pesquisa demonstra a importância de adotar manejo profilático para garantir higidez dos rebanhos e dos funcionários das propriedades leiteiras.

Relação da idade na presença de bactérias resistentes a antimicrobianos em rebanhos leiteiros no Rio Grande do Sul

A mastite bovina é uma doença importante na bovinocultura de leite, devido à sua alta incidência e perdas econômicas associadas principalmente com a produção de leite reduzida e aos custos do tratamento. O uso de antimicrobianos para o tratamento de casos clínicos e no período seco tem levantado preocupações quanto à seleção de cepas bacterianas resistentes. Isso também pode refletir na saúde pública, uma vez que bactérias resistentes, como o Staphylococcus aureus meticilina-resistente (MRSA), podem ser transmitidas aos seres humanos por contato direto com animais infectados ou produtos lácteos. A resistência das bactérias aos agentes antimicrobianos aumentou, em geral, devido a tratamentos ineficazes. Estudos realizados no Brasil com amostras não planejadas mostram aumento no padrão de resistência, principalmente em S. aureus. A exposição ao tratamento antimicrobiano repetido ao longo das lactações consecutivas de vacas pode ser um fator predisponente para o desenvolvimento da resistência antimicrobiana em bactérias que infectam o úbere. Assim, o objetivo deste estudo foi determinar a possível associação causal entre resistência antimicrobiana em bactérias isoladas a partir do leite bovino e dados como idade e período de lactação. As amostras de leite foram coletadas de 21 rebanhos leiteiros do Rio Grande do Sul, Brasil, selecionados aleatoriamente a partir da população-alvo de 1.656 explorações leiteiras semi-intensivas, estratificada por tamanho do rebanho. A bactéria foi considerada a unidade amostral, e para a estimativa de prevalência foram utilizados os seguintes parâmetros: uma frequência de 35% de Staphylococcus sp. resistentes à penicilina; um nível de confiança de 90%; e uma precisão absoluta de 12%. As bactérias foram isoladas de amostras de leite compostas de todos os quartos mamários de cada vaca após descartar os primeiros três ou quatro jatos de leite. Para acessar os potenciais fatores de risco, características dos animais foram obtidas através de uma entrevista com os produtores. Os exames laboratoriais foram realizados de acordo com as recomendações do National Mastitis Council. Um total de 242 isolados foi obtido de 195 vacas a partir da amostra do rebanho total (251 vacas). A prevalência de infecções foi descrita em grupos de acordo com o perfil epidemiológico: bactérias ambientais, contagiosas e outras. Estas perfizeram 57,3%, 26,3% e 11,2%, respectivamente, dos animais amostrados. Testes de suscetibilidade antimicrobiana contra 12 diferentes antimicrobianos foram realizados em 159 isolados. No total, 30% dos isolados testados mostraram resistência a pelo menos três grupos diferentes de antimicrobianos e foram classificados como multirresistentes. Foram observadas as freqüências mais elevadas de resistência contra a ampicilina para os estafilococos coagulase-negativo, seguida de eritromicina para estafilococos coagulase-positivo e tetraciclina para estreptococos. A análise de regressão logística mostrou uma relação significativa entre a idade das vacas e a presença de estafilococos coagulase-positivo multirresistentes e distribuição de classes diferentes de bactérias nos diferentes estratos etários, o que sugere uma concorrência dinâmica ao longo do tempo (p < 0,05). Animais com três a quatro anos tiveram 13,7 vezes mais chances (IC95% 1,4 - 130,2, p = 0,02) de ter estafilococos coagulase-positivo multirresistentes em comparação com aqueles com dois ou três anos. O tempo de exposição a agentes infecciosos e consequentes terapias sugere uma maior chance de colonização do úbere por patógenos resistentes devido à pressão de seleção repetida durante a vida.

170 NATURALLY OCCURRING CHRONIC MASTITIS COMPROMISES FOLLICULOGENESIS, AFFECTS VASCULARIZATION, AND INTERACTS WITH DIFFERENTIATION FACTOR GDF-9 IN BOVINE OVARIAN STROMA

Recent studies have suggested an association between reproductive failure and mastitis in lactating dairy cows, but our understanding of how mastitis affects reproduction is still limited. In the present study we investigated the effects of naturally occurring chronic mastitis on the population dynamics of ovarian follicles. Ovaries and milk samples were collected from 74 cows at slaughter. Milk samples from each quarter, were analyzed following National Mastitis Council procedures. Based on the presence of major pathogens and somatic cell count results, animals were sorted in 9 groups, but only the 2 extremes were considered for further analysis: uninfected (n = 8) and affected by chronic mastitis (n = 9). Primordial, primary, and secondary follicles were counted and scored on similar surface area of ovary sections for each animal (mean ± SD = 5.65 ± 0.25 cm2). They were analyzed with Fisher’s exact test, and the association between health status and follicle number was estimated by odds ratios ± confidence limits. Vasculature area in the ovarian cortex of healthy and mastitic animals was identified using Bandeiraea simplicifolia-I lectin (BSL-I). Results were quantified with the dedicated software MacBiophotonics image J, NIH, USA, and subsequently analyzed with t-test for statistical significance. Follicles were further characterized by immunostaining with a GDF-9-specific antibody. The intensity of the staining was semi-quantified using a relative scale: 0, 1, and 2 for no, weak, and strong staining, respectively. Our results indicate no (P > 0.05) difference between the numbers of primordial and primary follicles in healthy and affected animals. In contrast, the number of secondary follicles was significantly lower in sick animals (odds ratio 10.50*; P < 0.05), indicating 10 times higher risk for a mastitic animal to have less than 2 secondary follicles per square centimeter. Ovarian stromal vasculature represented the 6.38 ± 0.66% of cortical area in healthy animals v. 4.24 ± 0.37% (P < 0.001) in affected cows. The GDF-9 immunostaining revealed decreased fluorescence intensity in mastitic animals. Our results show that chronic mastitis is associated with considerable alterations in follicle growth and differentiation with a decreased ability of primary follicles to develop into the secondary state in affected animals. This is accompanied by a significant decrease of ovarian vasculature and the down-regulation of the follicle differentiation-associated factor GDF. The present findings substantiate the hypothesis that mastitis can reduce fertility by exerting a negative effect on ovarian function.

I. EFFECTS OF PROCEDURAL VARIATIONS ON ACCURACY AND PRECISION1

The effects of three changes in the optical equipment used for Direct Microscopic Somatic Cell Count in milk (National Mastitis Council method) on performance of the method have been measured and subjected to statistical analysis of probable significance. Replicate slides of six milk samples were counted by eight technicians among the authors' laboratories. Three levels of cell concentration were represented among the samples. No consistent differences in estimated cell concentration were demonstrated in the comparisons of narrow versus wide reticle band, wide field versus Huyghenian eyepieces, or low (high dry) versus high (oil immersion) magnification. In a few instances within each comparison, individual counters produced markedly different results when the optical equipment was modified. These individual biases were large and consistent with regard to change in objective magnification. No evidence was found to preclude use of wide field eyepieces in performing the DMSCC.

ABNORMAL MILK CONTROL–A PROGRESS REPORT

Two phases of a national program on control of abnormal milk are in effect. The third phase is scheduled to take effect July 1, 1970. The program will be evaluated at the May, 1969 meeting of the National Conference on Interstate Milk Shipments (IMS). A report from the IMS Committee on Abnormal Milk Control will serve as a basis for this evaluation. Many organizations are active in abnormal milk work. These include U. S. Public Health Service, U. S. Department of Agriculture, National Mastitis Council, local and state regulatory agencies, and many segments of the dairy industry. The Public Health Service published “Guidelines for the Control of Abnormal Milk” in May, 1968. These guidelines cover the first two phases of the IMS Abnormal Milk Program. Committees of the National Mastitis Council are making significant contributions to the abnormal milk program. Good progress is being made on control of abnormal milk. If reason prevails, the efforts of many organizations and individuals will bring success.

SURVEY OF ABNORMAL MILK PROGRAMS ADMINISTERED BY STATE REGULATORY AGENCIES1,2

Summary Through survey questionnaires, information was obtained about the abnormal milk control programs administered by state regulatory agencies. Responses were received from dairy regulatory officials in 49 states. A majority (67%) of the states did not have a designated abnormal milk regulatory program at the time of this survey, but many were in the process of developing such programs. More concern was evident for the control of abnormal milk in the Grade A supply than for the manufacturing supply. The tests most widely reported for detecting abnormal milk (in order of prominence) were: microscopic leucocyte count, California mastitis test, modified Whiteside test, catalase test, and Wisconsin mastitis test. Standards based on leucocyte counts of 500,000 or 1,000,000/ml were reported by 13 states. Approximately 70% of the responding states indicated that their programs followed the recommendations of the National Mastitis Council; however, others (30%) indicated further studies would be made before abnormal milk regulations could be promulgated.