Caracterização molecular e fenotípica de Staphylococcus aureus na mastite bovina subclínica
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Data
2016-07-29
Autores
Rossi, Bruna Fernanda [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A mastite é uma inflamação da glândula mamária geralmente causada por infecção bacteriana, levando a grandes perdas econômicas na bovinocultura leiteira, à desvalorização do animal e ao aumento no uso de medicamentos. Um dos principais responsáveis pela mastite bovina é o Staphylococcus aureus e a presença constante desse micro-organismo pode ocasionar a seleção de cepas resistentes. Vários genes estão envolvidos com a produção de fatores de virulência como as hemolisinas, leucotoxinas (toxina de Panton Valentine) e os superantígenos (enterotoxinas e toxina da Síndrome do Choque Tóxico). Assim, o objetivo do estudo foi caracterizar molecularmente e identificar o potencial de virulência e a resistência a antimicrobianos de cepas de S. aureus, isoladas de vacas com mastite subclínica, de uma fazenda, no período de 12 meses. Além disso, foi verificada a persistência de colonização da cepa nos animais, ao longo desse tempo. Foram analisadas 665 amostras de leite de vacas com mastite subclínica e 116 (17,4%) foram positivas para a presença de S. aureus. Os genes que codificam as enterotoxinas clássicas foram observados em 28 (24,1%) das cepas, enquanto o gene da Toxina Panton-Valentine (pvl) foi encontrado em frequência bem menor, de 3,4% (4 cepas) e o tsst (síndrome do choque tóxico) foi encontrado em 54 isolados (46,6%). Foram encontradas 9 (7,8%) cepas meticilina resistente (MRSA), das quais 4 (44,4%) apresentaram o gene mecA e pertenciam ao SCCmec tipo I, enquanto o gene mecC não foi encontrado nas demais cepas MRSA. Em relação à tipagem molecular pelo grupo agr, 68 (58,6%) isolados não foram classificados em nenhum dos 4 grupos existentes e o grupo agrI foi o mais encontrado. Pela técnica de gel de eletroforese em campo pulsado (PFGE), observou-se a persistência de colonização de um mesmo clone em um animal, ao longo de 9 meses. Essa cepa foi classificada como ST 711, pela técnica de Multi Locus Sequence Typing (MLST). A presença de vários clones infectando diferentes animais, ou cepas de um mesmo clone colonizando vários animais, demonstraram práticas higiênicas inadequadas e a presença, nesses clones, de genes que codificam fatores de virulência e resistência aos antimicrobianos, dificultam o controle da mastite. O conhecimento dessas características moleculares, é essencial para o entendimento da circulação desses clones e de suas implicações na saúde pública e animal.
Mastitis is an inflammation of the mammary gland usually caused by bacterial infection, leading high economic losses in dairy cattle due to reduced production of milk, devaluation of the animals and treatment costs. One of the main responsible for bovine mastitis is Staphylococcus aureus and it constant presence can select resistant isolates. Several genes seem to be involved with the production of virulence factors such as hemolysin, leukotoxins (toxin Panton Valentine) and superantigens as the toxin Panton Valentine and (enterotoxin and toxin Toxic Shock Syndrome).Thus, the aim of the study was to characterize molecularly and identify the virulence potencial and resistance to antimicrobials of S. aureus strains isolated from cows with subclinical mastitis in a single farm in 12 months. Furthermore, the persistence of colonization of the strain was observed in the animals during that time. Were analyzed 665 samples of milk from cows with subclinical mastitis and 116 (17.4%) were positive for the presence of S. aureus. The genes encoding the classical enterotoxins were observed in 28 (24.1%) of the strains, while toxin gene Panton-Valentine (pvl) was found at much lower frequency, 3.4% (4 strains). The tsst gene (toxic shock syndrome) was found in 54 isolates (46.5%). Were found 9 (7.8%) methicillin resistant strains (MRSA), of which 4 showed the mecA gene and belonged to Sccmec type I, while the mecC has not yet been researched. In relation to molecular typing by agr group, 68 (58,6%) isolates did not belong to either group and agrI was the most frequent. Electrophoresis pulsed field gel (PFGE) revealed persistent colonization of the same clone in the same animal over 9 months. This strain was classified as ST 711, by Multi Locus Sequence Typing (MLST). The presence of several different clones that infecting different animals, or strains the same clone colonizing several animals, demonstrated inadequate hygiene practice and the presence of these genes in clones that encode of virulence factors and drugs resistance hinder the control of mastitis. Knowledge of these molecular characteristics is essential to understanding the current clones and their implications for animal health.
Mastitis is an inflammation of the mammary gland usually caused by bacterial infection, leading high economic losses in dairy cattle due to reduced production of milk, devaluation of the animals and treatment costs. One of the main responsible for bovine mastitis is Staphylococcus aureus and it constant presence can select resistant isolates. Several genes seem to be involved with the production of virulence factors such as hemolysin, leukotoxins (toxin Panton Valentine) and superantigens as the toxin Panton Valentine and (enterotoxin and toxin Toxic Shock Syndrome).Thus, the aim of the study was to characterize molecularly and identify the virulence potencial and resistance to antimicrobials of S. aureus strains isolated from cows with subclinical mastitis in a single farm in 12 months. Furthermore, the persistence of colonization of the strain was observed in the animals during that time. Were analyzed 665 samples of milk from cows with subclinical mastitis and 116 (17.4%) were positive for the presence of S. aureus. The genes encoding the classical enterotoxins were observed in 28 (24.1%) of the strains, while toxin gene Panton-Valentine (pvl) was found at much lower frequency, 3.4% (4 strains). The tsst gene (toxic shock syndrome) was found in 54 isolates (46.5%). Were found 9 (7.8%) methicillin resistant strains (MRSA), of which 4 showed the mecA gene and belonged to Sccmec type I, while the mecC has not yet been researched. In relation to molecular typing by agr group, 68 (58,6%) isolates did not belong to either group and agrI was the most frequent. Electrophoresis pulsed field gel (PFGE) revealed persistent colonization of the same clone in the same animal over 9 months. This strain was classified as ST 711, by Multi Locus Sequence Typing (MLST). The presence of several different clones that infecting different animals, or strains the same clone colonizing several animals, demonstrated inadequate hygiene practice and the presence of these genes in clones that encode of virulence factors and drugs resistance hinder the control of mastitis. Knowledge of these molecular characteristics is essential to understanding the current clones and their implications for animal health.
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Palavras-chave
S.aureus, Mastitis, MecA, PFGE, MLS, Mastite