Causes of abortion, stillbirth, and perinatal mortality in horses / Causas de aborto, natimortalidade e morte perinatal em equinos

Causes of abortion, stillbirth, and perinatal mortality in horses were investigated in the Department of Veterinary Pathology of the Federal University of Rio Grande do Sul (SPV-UFRGS) from 2000 to 2015. In this period, 107 cases were analyzed using macroscopic, microscopic, and complementary tests. Of these, 77 were aborted fetuses, 16 were stillbirths, and 14 were perinatal deaths. Conclusive diagnosis was established in 42.8% of the fetuses analyzed, with 28.6% classified as infectious origin, 9.1% as non-infectious, and 5.1% as other. Bacterial infections, especially those related to Streptococcus spp. were the most frequently observed. In stillborn foals, diagnosis was established in 62.5% of cases, and 50% of these were related to non-infectious causes, such as dystocia and birth traumas. As for perinatal mortality, a conclusive diagnosis was reached in 78.57% of cases, and infectious causes associated with bacterial infections accounted for 64.1% of these diagnoses.(AU)

Causas de aborto, natimortalidade e mortalidade perinatal em equinos foram investigadas no Setor de Patologia Veterinária da Universidade Federal do Rio Grande do Sul (SPV-UFRGS) durante o período de 2000 a 2015. Nesse período, foram analisados 107 casos através de exames macroscópico, microscópico e exames complementares, desses 77 correspondiam a fetos abortados, 16 natimortos e 14 mortes perinatais. Diagnóstico conclusivo foi estabelecido em 42,8% dos fetos analisados e classificados como origem infecciosa em 28,6% dos casos, não infecciosa com 9,1% e outros com 5,1% dos casos. As infecções bacterianas, em especial as relacionadas a Streptococcus spp. foram as mais frequentemente observadas. Em potros natimortos, diagnostico foi estabelecido em 62,5% dos casos, e destes, 50% foram relacionados a causas não infecciosas, como distocia e traumas durante o parto. Quanto a mortalidade perinatal, em 78,57% dos casos houve um diagnostico conclusivo, e as causas infecciosas associadas a infecções bacterianas corresponderam a 64,1% desses diagnósticos.(AU)

Causes of abortion, stillbirth, and perinatal mortality in horses / Causas de aborto, natimortalidade e morte perinatal em equinos

Causes of abortion, stillbirth, and perinatal mortality in horses were investigated in the Department of Veterinary Pathology of the Federal University of Rio Grande do Sul (SPV-UFRGS) from 2000 to 2015. In this period, 107 cases were analyzed using macroscopic, microscopic, and complementary tests. Of these, 77 were aborted fetuses, 16 were stillbirths, and 14 were perinatal deaths. Conclusive diagnosis was established in 42.8% of the fetuses analyzed, with 28.6% classified as infectious origin, 9.1% as non-infectious, and 5.1% as other. Bacterial infections, especially those related to Streptococcus spp. were the most frequently observed. In stillborn foals, diagnosis was established in 62.5% of cases, and 50% of these were related to non-infectious causes, such as dystocia and birth traumas. As for perinatal mortality, a conclusive diagnosis was reached in 78.57% of cases, and infectious causes associated with bacterial infections accounted for 64.1% of these diagnoses.

Causas de aborto, natimortalidade e mortalidade perinatal em equinos foram investigadas no Setor de Patologia Veterinária da Universidade Federal do Rio Grande do Sul (SPV-UFRGS) durante o período de 2000 a 2015. Nesse período, foram analisados 107 casos através de exames macroscópico, microscópico e exames complementares, desses 77 correspondiam a fetos abortados, 16 natimortos e 14 mortes perinatais. Diagnóstico conclusivo foi estabelecido em 42,8% dos fetos analisados e classificados como origem infecciosa em 28,6% dos casos, não infecciosa com 9,1% e outros com 5,1% dos casos. As infecções bacterianas, em especial as relacionadas a Streptococcus spp. foram as mais frequentemente observadas. Em potros natimortos, diagnostico foi estabelecido em 62,5% dos casos, e destes, 50% foram relacionados a causas não infecciosas, como distocia e traumas durante o parto. Quanto a mortalidade perinatal, em 78,57% dos casos houve um diagnostico conclusivo, e as causas infecciosas associadas a infecções bacterianas corresponderam a 64,1% desses diagnósticos.

Lung lesions of slaughtered horses in southern Brazil / Lesões pulmonares de equinos de matadouro-frigorífico no Sul do Brasil

Respiratory diseases cause significant veterinary costs, reduce performance and require withdrawal of horses. Yet, studies of the causes of pneumonia in horses are scant. This study aimed to describe the pathological and microbiological features of lung lesions in slaughtered horses in southern Brazil. In this study, 84 samples of lungs were examined, and a conclusive diagnosis was obtained in 74 cases. These were composed of bronchopneumonia in 50 cases, followed by granulomatous eosinophilic pneumonia (9/74), recurrent airway obstruction (7/74), lung fibrosis (4/74), lung hemorrhage (3/74) and pulmonary pythiosis (1/74). Bronchopneumonia had grossly firm focally extensive yellow to dark-red areas, which consisted microscopically of multifocal to coalescing infiltrate of degenerate neutrophils. Streptococcus equi subsp. zooepidemicus was identified in 21 of the 50 cases. Granulomatous eosinophilic pneumonia had multifocal pinpoint firm-hard yellow areas, which microscopically were composed of granulomas with a mineralized center surrounded by collagen fibers and severe infiltrate of eosinophils. Recurrent airway obstruction had mild multifocal pinpoint firm white areas that consisted microscopically of large amounts of mucus inside bronchi and bronchiole. Lung fibrosis had two patterns: focally extensive areas of consolidation and firm nodular areas. Microscopically, the first pattern had interstitial to peribronchial fibrosis, while the second had, in addition to the interstitial fibrosis, a severe pneumocyte hyperplasia and an alveolar infiltrate of neutrophils and macrophages with rare intranuclear inclusion bodies (equine herpesvirus 5, EHV-5). Pulmonary pythiosis presented a focal firm nodular area, with multiple kunkers observed in the cut surface, which corresponded microscopically to areas of necrosis surrounded by a mixed inflammatory infiltrate. At the periphery of the necrotic areas, multiple negatively stained hyphae were observed, which were evidenced through Grocott's stain and immunohistochemistry anti-Pythium insidiosum.(AU)

Doenças respiratórias causam em equinos custos significativos com tratamento veterinário, redução de performance e descarte de animais. No entanto, estudos que abordem as causas de pneumonia em equinos são escassos. O objetivo deste estudo foi descrever os aspectos patológicos e microbiológicos de lesões pulmonares em equinos abatidos em matadouro-frigorífico no Sul do Brasil. Neste estudo, 84 amostras de pulmões foram examinadas, e o diagnóstico conclusivo das condições foi obtido em 74 casos. Esses foram compostos por broncopneumonia em 50 casos, seguido por pneumonia granulomatosa eosinofílica (9/74), obstrução aérea recorrente (7/74), fibrose pulmonar (4/74), hemorragia pulmonar (3/74) e pitiose pulmonar (1/74). A broncopneumonia era caracterizada macroscopicamente por áreas focalmente extensas firmes de coloração amarelada a vermelho-escuras, as quais consistiam microscopicamente em infiltrado multifocal a coalescente de neutrófilos degenerados. Streptococcus equi subsp. zooepidemicus foi identificado em 21 dos 50 casos. A pneumonia eosinofílica granulomatosa era caracterizada por áreas multifocais puntiformes firmes a duras e amareladas, que microscopicamente eram compostas por granulomas com área central mineralizada circundados por fibras de colágeno e infiltrado acentuado de eosinófilos. A obstrução aérea recorrente era caracterizada por discretas áreas puntiformes firmes e brancacentas que consistiam microscopicamente em grande quantidade de muco no interior de brônquios e bronquíolos. A fibrose pulmonar exibia dois padrões: áreas de consolidação focalmente extensas e áreas nodulares firmes. Microscopicamente, o primeiro padrão exibia fibrose intersticial a peribronquial, enquanto no segundo padrão havia, além da fibrose intersticial, intensa hiperplasia de pneumócitos e infiltrado alveolar de neutrófilos e macrófagos com raros corpúsculos de inclusão intranucleares (herpesvírus equino 5, EHV-5). A pitiose pulmonar exibia uma área nodular firme focal com múltiplos kunkers ao corte, os quais correspondiam microscopicamente a áreas de necrose circundadas por infiltrado inflamatório misto. À periferia das áreas necróticas, múltiplas imagens negativas de hifas eram observadas, as quais foram evidenciadas através da coloração de Grocott e imuno-histoquímica anti-Pythium insidiosum.(AU)

Sensibilidad a los antimicrobianos de aislamientos de Streptococcus equi subsp. equi de la provincia de Buenos Aires, Argentina / Antimicrobial susceptibility in isolates of Streptococcus equi subsp. equi from Buenos Aires province, Argentina

Streptococcus equi subsp. equi es el agente etiológico de la adenitis equina, una enfermedad infecciosa que afecta al tracto respiratorio superior y linfonódulos de cabeza y cuello de equinos. La terapia antimicrobiana tradicional incluye como antibiótico de primera elección a la penicilina G (PEN), a la que los estreptococos suelen ser sensibles. El objetivo de este trabajo fue estudiar el perfil de sensibilidad a distintos antimicrobianos de cepas de S. equi que circulan en la provincia de Buenos Aires, Argentina. Se estudiaron 92 aislamientos mediante el método de difusión con discos; los antimicrobianos evaluados fueron PEN, cefotaxima, eritromicina, tetraciclina, enrofloxacina (ENR), trimetroprima-sulfametoxazol (TMS), ciprofloxacina, clindamicina (CLI), estreptomicina (STR) y florfenicol. Se determinó la concentración inhibitoria mínima (CIM) de la PEN y de aquellos antimicrobianos frente a los cuales S. equi mostró resistencia o sensibilidad intermedia. Se obtuvieron altos porcentajes de sensibilidad a todos los antimicrobianos por el método de difusión y valores de CIM por debajo de los puntos de corte para PEN, TMS y CLI. Se identificaron cepas resistentes a ENR y STR, con CIM50, CIM9o y rangos de CIM por encima de los puntos de corte. Los resultados confirman que la PEN podría utilizarse empíricamente, ya que las cepas circulantes en Buenos Aires no mostraron resistencia a este antimicrobiano. Se enfatiza en la relevancia del uso racional de los antibióticos para lograr éxito terapéutico, evitar la cronicidad, la recidiva de infecciones y la aparición de resistencia.

Streptococcus equi subsp. equi is the etiologic agent of strangles, an infectious disease affecting the upper respiratory tract and head and neck lymph nodes of equines. Routine antimicrobial therapy includes penicillin (PEN) as antibiotic of first choice. Streptococci are usually susceptible to PEN and only a few antimicrobial studies had been performed. The aim of this work was to study the antimicrobial susceptibility profile of S. equi from Buenos Aires, Argentina. Ninety-two isolates were studied by the single disk method to PEN, cefotaxime, erythromycin (ERY), tetracycline, enrofloxacin (ENR), trimethoprim sulfamethoxazole (TMS), ciprofloxacin, clindamycin (CLI), streptomycin (STR) and florfenicol. Minimum inhibitory concentration (MIC) to PEN and antibiotics with resistance and intermediate susceptibility were tested. High percentages of susceptibility were obtained by the disk diffusion method and MIC values of PEN, TMS and CLI were found to be under the breakpoint values. Resistant strains of ENR and STR with MIC50, MIC90 and MIC ranges above breakpoints were identified. These findings confirm that PEN may be used empirically because resistant strains were not found in Buenos Aires. Emphasis is placed on the rational use of antibiotics to achieve therapeutic success, to prevent chronicity, recurrence of infections and the emergence of resistance.

Streptococcus uberis: In vitro biofilm production in response to carbohydrates and skim milk / Streptococcus uberis: producción in vitro de biofilm en respuesta a carbohidratos y leche descremada

Streptococcus uberis has become one of the most important environmental pathogens associated with clinical and subclinical bovine mastitis. Biofilm confers to bacteria more resistance to physical and chemical agents as well as to different mechanisms of the innate immune system. The aim of this work was to evaluate the ability of in vitro biofilm production in 32 S. uberis isolates from bovine mastitis and identified by biochemical tests and milk subsequently confirmed by the amplification of the pauA gene. The isolates were cultivated in TMP broth and TMP broth with the addition of 0.5% glucose, 1% sucrose, 1% lactose or 0.5% skim milk in microtiter plates stained with crystal violet. We demonstrated that S. uberis isolated from bovine mastitis are able to produce biofilms in TMP broth and, also that biofilm formation by S. uberis can be significantly enhanced by the addition of 0.5% glucose or 1% sucrose to TMP broth. This may suggest that the carbohydrates in milk or within the ruminant gut might affect the growth mode of S. uberis. In addition, our results showed that in vitro biofilm production under different conditions of supplementation displays variation among the isolates and that each isolate shows a particular profile of biofilm production. This phenotypic heterogeneity in biofilm production exhibited by S. uberis could at least partly explain why this bacterium has the ability to adapt to different niches facilitating survival to diverse and stressful conditions.

Streptococcus uberis es uno de los más importantes patógenos medioambientales asociados a la mastitis bovina clínica y subclínica. El biofilm confiere a las bacterias resistencia a agentes físicos y químicos, como así también a diferentes mecanismos del sistema inmune innato. El objetivo del presente estudio fue evaluar la habilidad de producción de biofilm in vitro de 32 aislamientos de S. uberis recuperados de mastitis bovina, previamente identificados por pruebas bioquímicas y confirmados por la amplificación del gen pauA. Los aislamientos fueron cultivados en caldo TMP sin carbohidratos, y además en caldo TMP con la adición de 0,5% de glucosa, 1% de sacarosa, 1% de lactosa o 0,5% de leche descremada, en placas de microtitulación tenidas con cristal violeta. Se demostró que dichos aislamientos son capaces de producir biofilm en caldo TMP, y además se observó un incremento significativo en la producción de biofilm en caldo TMP suplementado con 0,5% de glucosa o con 1% de sacarosa. Así, los carbohidratos de la leche o los presentes dentro del intestino de los rumiantes podrían afectar el modo de crecimiento de S. uberis. Además, nuestros hallazgos mostraron que la producción de biofilm in vitro en diferentes condiciones de suplementación presenta variabilidad entre los aislamientos de S. uberis y que cada aislamiento muestra un perfil particular de producción de biofilm. Esta heterogeneidad fenotípica en la producción de biofilm de S. uberis podría explicar, al menos en parte, por qué esta bacteria tiene la habilidad de adaptarse a diferentes nichos, lo que le facilita la supervivencia frente a condiciones diversas y estresantes.

Molecular epidemiology of Streptococcus agalactiae isolated from mastitis in Brazilian dairy herds

Abstract Streptococcus agalactiae is one of the most common pathogens leading to mastitis in dairy herds worldwide; consequently, the pathogen causes major economic losses for affected farmers. In this study, multilocus sequence typing (MLST), genotypic capsular typing by multiplex polymerase chain reaction (PCR), and virulence gene detection were performed to address the molecular epidemiology of 59 bovine (mastitis) S. agalactiae isolates from 36 dairy farms located in the largest milk-producing mesoregions in Brazil (Minas Gerais, São Paulo, Paraná, and Pernambuco). We screened for the virulence genes bac, bca, bibA, cfb, hylB, fbsA, fbsB, PI-1, PI-2a, and PI-2b, which are associated with adhesion, invasion, tissue damage, and/or immune evasion. Furthermore, five capsular types were identified (Ia, Ib, II, III, and IV), and a few isolates were classified as non-typeable (NT). MLST revealed the following eight sequence types (STs): ST-61, ST-67, ST-103, ST-146, ST-226, ST-314, and ST-570, which were clustered in five clonal complexes (CC64, CC67, CC103, CC17, and CC314), and one singleton, ST-91. Among the virulence genes screened in this study, PI-2b, fbsB, cfb, and hylB appear to be the most important during mastitis development in cattle. Collectively, these results establish the molecular epidemiology of S. agalactiae isolated from cows in Brazilian herds. We believe that the data presented here provide a foundation for future research aimed at developing and implementing new preventative and treatment options for mastitis caused by S. agalactiae.

Genotipificación y estudio de los genes pauA y sua de aislamientos de Streptococcus uberis de mastitis bovina / Genotyping and study of the pauA and sua genes of Streptococcus uberis isolates from bovine mastitis

This study aimed to determine the clonal relationship among 137 Streptococcus uberis isolates from bovine milk with subclinical or clinical mastitis in Argentina and to assess the prevalence and conservation of pauA and sua genes. This information is critical for the rational design of a vaccine for the prevention of bovine mastitis caused by S. uberis. The isolates were typed by random amplified polymorphic DNA (RAPD) analysis and by pulsed-field gel electrophoresis (PFGE). The 137 isolates exhibited 61 different PFGE types and 25 distinct RAPD profiles. Simpson's diversity index was calculated both for PFGE (0.983) and for RAPD (0.941), showing a high discriminatory power in both techniques. The analysis of the relationship between pairs of isolates showed 92.6 % concordance between both techniques indicating that any given pair of isolates distinguished by one method tended to be distinguished by the other. The prevalence of the sua and pauA genes was 97.8 % (134/137) and 94.9 % (130/137), respectively. Nucleotide and amino acid sequences of the sua and pauA genes from 20 S. uberis selected isolates, based on their PFGE and RAPD types and geographical origin, showed an identity between 95 % and 100 % with respect to all reference sequences registered in GenBank. These results demonstrate that, in spite of S. uberis clonal diversity, the sua and pauA genes are prevalent and highly conserved, showing their importance to be included in future vaccine studies to prevent S. uberis bovine mastitis.

Este estudio pretendió determinar la relación clonal entre 137 aislamientos de S. uberis obtenidos de leche de bovinos con mastitis clínica o subclínica en la Argentina, como así también la prevalencia y la conservación de los genes sua y PauA entre dichos aislamientos. Esta información es crítica para el diseño racional de una vacuna que prevenga la mastitis bovina por S. uberis. Los aislamientos se tipificaron molecularmente por amplificación al azar del ADN polimórfico (RAPD) y mediante electroforesis de campos pulsados (PFGE). Los 137 aislamientos mostraron 61 pulsotipos mediante PFGE y 25 tipos de RAPD diferentes. Los índices de Simpson calculados fueron 0,983 por PFGE y 0,941 por RAPD; esto evidencia el elevado poder discriminatorio de ambas técnicas. El análisis de la relación entre pares de aislamientos mostró un 92,6 % de concordancia entre ambas técnicas, lo que indica que cualquier par de aislamientos que fue distinguido por un método tendió a ser distinguido por el otro. La prevalencia de los genes sua y puaA fue del 97,8 % (134/137) y 94,9 % (130/137), respectivamente. Las secuencias de nucleótidos y de aminoácidos codificados por los genes sua y pauA de los 20 aislamientos de S. uberis seleccionados sobre la base de su tipo de PFGE y RAPD y origen geográfico tuvieron un porcentaje de identidad de entre 95 % y 100 % con respecto a todas las secuencias de referencia registradas en GenBank. Estos resultados demuestran que, a pesar de la diversidad clonal de S. uberis, los genes sua y pauA son prevalentes y están altamente conservados y deberían ser incluidos en futuros estudios de vacunas para prevenir mastitis bovina causada por S. uberis.

Conjugative transfer of resistance determinants among human and bovine Streptococcus agalactiae

Streptococcus agalactiae (GBS) is a major source of human perinatal diseases and bovine mastitis. Erythromycin (Ery) and tetracycline (Tet) are usually employed for preventing human and bovine infections although resistance to such agents has become common among GBS strains. Ery and Tet resistance genes are usually carried by conjugative transposons (CTns) belonging to the Tn916 family, but their presence and transferability among GBS strains have not been totally explored. Here we evaluated the presence of Tet resistance genes (tetM and tetO) and CTns among Ery-resistant (Ery-R) and Ery-susceptible (Ery-S) GBS strains isolated from human and bovine sources; and analyzed the ability for transferring resistance determinants between strains from both origins. Tet resistance and int-Tn genes were more common among Ery-R when compared to Ery-S isolates. Conjugative transfer of all resistance genes detected among the GBS strains included in this study (ermA, ermB, mef, tetM and tetO), in frequencies between 1.10-7 and 9.10-7, was possible from bovine donor strains to human recipient strain, but not the other way around. This is, to our knowledge, the first report of in vitro conjugation of Ery and Tet resistance genes among GBS strains recovered from different hosts.

Phenotypic and genotypic characterization of Streptococcus uberis isolated from bovine subclinical mastitis in Argentinean dairy farms

The aim of this study was to investigate the phenotypic and genotypic characteristics of Streptococcus uberis isolated from subclinical mastitis (SCM) cases, and to examine the possible association between both characteristics. A total of 32 S. uberis were isolated from 772 quarter milk samples (SCM > 250,000 cells/ml) collected from 195 cows selected randomly from 18 dairy farms located in Argentina. The S. uberis strains were characterized phenotypically by the presence of virulence factors as plasminogen activator factor (PAF), hyaluronidase (HYA), capsule (CAP) and CAMP factor, and were further characterized genotypically by pulsed-field gel electrophoresis (PFGE). S. uberis strains expressed plasminogen activator factor, hyaluronidase or capsule (65.5 %, 56.3 %, 59.4 %, respectively), but only 25 % of isolates were CAMP factor positive. Thirteen different virulence profiles were identified on the basis of the combination of virulence factors. Eighteen PFGE patterns with 90% of similarity were identified among 32 S. uberis. A great diversity of virulence profiles and PFGE patterns were present among dairy farms. S. uberis strains with the same PFGE pattern showed different virulence profiles. Bovine S. uberis strains causing SCM included in the present study showed heterogeneity in regard to their phenotypic and genotypic characteristics, and the PFGE patterns are not associated with the virulence profiles.

Caracterización fenotípica y genotípica de Streptococcus uberis aislados de mastitis bovina subclínica en tambos de Argentina. El objetivo de este estudio fue investigar las características fenotípicas y genotípicas de Streptococcus uberis aislados de casos de mastitis subclínica (MSC) y examinar la posible asociación entre ambas características. Un total de 32 cepas de S. uberis fueron aisladas de 772 muestras de leche de cuartos mamarios (MSC > 25 0000 células/ml) colectadas de 195 vacas seleccionadas al azar pertenecientes a 18 tambos lecheros localizados en Argentina. Las cepas de S. uberis fueron caracterizadas fenotípicamente sobre la base de la presencia de factores de virulencia tales como el factor activador del plasminógeno (FAP), la hialuronidasa (HIA), la cápsula (CAP) y el factor CAMP. Además, fueron caracterizadas genotípicamente por electroforesis de campos pulsados (PFGE). Las cepas de S. uberis expresaron el factor activador del plasminógeno, la hialuronidasa o la cápsula (65,5 %, 56,3 % y 59,4 %, respectivamente), pero solo el 25 % fueron CAMP positivas. Sobre la base de la combinación de los factores de virulencia se identificaron 13 perfiles de virulencia diferentes. Asimismo, se identificaron 18 patrones de PFGE con un 90 % de similitud entre las 32 cepas de S. uberis. Se presentó una gran diversidad de perfiles de virulencia y patrones de PFGE entre los tambos. Cepas con el mismo patrón de PFGE presentaron perfiles de virulencia diferentes. Las cepas de S. uberis causantes de MSC en bovinos incluidas en el presente estudio mostraron heterogeneidad con respecto a sus características fenotípicas y genotípicas, y los patrones de PFGE no estuvieron asociados con los perfiles de virulencia.

Intramammary infections during the periparturient period in Argentine dairy heifers / Infecciones intramamarias durante el periparto en vaquillonas en Argentina

Prevalence of intramammary infections at prepartum and postpartum in primigravid heifers from five dairy herds located in the central dairy area of Argentina was determined. Mammary secretion samples from 140 heifers (560 mammary quarters) were obtained 14 days prior to the expected calving day and within 7 days after parturition and subjected to bacteriological analysis. No clinical mastitis cases were detected during the study. The number of infected heifers in at least one mammary quarter at pre and postpartum was 87 (62.2%) and 53 (37.8%), respectively. The most prevalent mastitis pathogens at prepartum among samples yielding a positive bacteriological culture were coagulasenegative staphylococci (69.07%), Staphylococcus aureus (12.71%) and Streptococcus uberis (4.42%). A decrease on isolation frequency of coagulase-negative staphylococci (53.41%) and S. uberis (2.27%) was observed at postpartum, while that of S. aureus showed an increase (21.59%). Presence of intramammary infections appeared to be associated with some management conditions. These results highlighted the need to improve diagnosis and control measures in replacement heifers.

Se determinó la prevalencia al preparto y posparto de infecciones intramamarias causadas por organismos patógenos de mastitis en vaquillonas primíparas de cinco establecimientos lecheros ubicados en la cuenca central santafesina. Se tomaron muestras de secreción mamaria de 140 vaquillonas (560 cuartos mamarios) aproximadamente 14 días antes de la fecha probable de parto y dentro de los 7 días posparto, y se procesaron bacteriológicamente. No se detectaron casos de mastitis clínicas durante el estudio. El número de vaquillonas infectadas en al menos un cuarto mamario al preparto y posparto fue de 87 (62,2%) y 53 (37,8%), respectivamente. Los organismos patógenos más prevalentes al preparto entre las muestras con cultivo bacteriológico positivo fueron estafilococos coagulasa negativos (69,07%), Staphylococcus aureus (12,7%) y Streptococcus uberis (4,42%). Al posparto se observó un descenso en la frecuencia de aislamiento de estafilococos coagulasa negativos (53,41%) y S. uberis (2,27%), mientras que la de S. aureus mostró un aumento (21,59%). La presencia de infecciones intramamarias pareció estar asociada con algunas prácticas de manejo. Estos resultados ponen de manifiesto la importancia de hacer extensivo el diagnóstico y control de la enfermedad a las vaquillonas de reemplazo antes de su ingreso al rodeo en ordeño.

Serotyping and evaluation of the virulence in mice of Streptococcus suis strains isolated from diseased pigs

Um total of 110 amostras de Streptococcus suis isoladas de suínos doentes, no Brasil foram sorotipificadas e analisadas para a virulência. Sorotipificação das amostras resultou na seguinte classificação: 42 amostras do sorotipo 2 (38,2%), 10 amostras do sorotipo 14 (9,1%), sete amostras do sorotipo 9 (6,4%), três amostras de cada sorotipo, 7 e 11 (2,7%), duas amostras de cada sorotipo, 1 e 8 (1,8%) e uma amostra de cada um dos sorotipos, ½, 3, 5, 6 e 10 (0,9%). Reações cruzadas entre os sorotipos 1, 14 e 7 foram observadas em 21 amostras (19,1%). Somente 41,9% das amostras foram patogênicas para camundongos.

Influence of bacterial factors on proliferation of bovine mammary epithelial cells

Effects of bovine mastitis pathogen virulence factors on mammary epithelial cell function are not clearly understood. In this study, the effect of streptococcal lipoteichoic acid (LTA), streptokinase, and Escherichia coli lipopolysaccharide (LPS) on proliferation of a primary bovine mammary epithelial cell culture (BTE) and on an established bovine mammary epithelial cell line (MAC-T) was evaluated. Mammary epithelial cells were cultured in the presence of bacterial virulence factors for 48 h at 37 degrees C. BTE cell proliferation was inhibited by streptococcal LTA at 8 and 16 micrograms/ml whereas MAC-T cell proliferation was reduced significantly by concentrations of LTA > or = 2 micrograms/ml. Streptokinase had no effect on proliferation of either MAC-T or BTE cells and LPS inhibited proliferation of BTE but not of MAC-T cells. Effect of LTA and LPS on mammary epithelial cell proliferation could be relevant during the periparturient period when mammary glands are markedly susceptible to new intramammary infection and when mammary epithelial cells undergo extensive proliferation, differentiation and synthesis of milk components.