RESUMEN
Un total de 79 cepas de S. aureus y 47 cepas de Staphylococcus coagulasa negativa (SCN) aislados de muestras de leche de vaca con mastitis subclínica fueron evaluadas para establecer su propiedad para formar biopelícula como uno de los factores de virulencia más importantes. Usando el método de Rojo Congo Agar, 80% de las cepas de S. aureus fueron productores de limo, mientras que en las cepas de SCN el porcentaje fue de 32%. Por el método de microplaca, 55%, 17% y 28% de los aislamientos de S. aureus fueron fuerte, moderadas y débiles productoras de biopelícula, mientras en los SCN el porcentaje fue 43%, 17% y 40%, respectivamente. Se realizó un ensayo de Reacción en Cadena de la Polimerasa (PCR) a todos los aislamientos con la finalidad de identificar el gen A de adhesión intracelular (icaA). En las cepas de S. aureus el gen icaA estuvo presente en el 65% de los aislamientos, y en los SCN en el 11%. La mayoría de las cepas de S. aureus caracterizados en el estudio fueron formadores de biopelícula, lo cual sugiere que está tiene un importante papel en la virulencia de S. aureus aislados de infecciones intramamarias en bovinos del estado Zulia.
A total of 79 S. aureus strains and 47 coagulase negative Staphylococcus (CNS) isolates from cow milk suffering subclinical mastitis were investigated for their ability to form biofilm as one of the most important virulence factors. Using Congo Red Agar method, 80% of S. aureus strains were slime producers, while in CNS was 32%. By microtiter plate method, 55%, 17%, and 28% of S. aureus isolates were strong, moderate, and weak biofilm producers, respectively, while in CNS the percentages were 43%, 17%, and 40%, respectively. All isolates were screened by Polymerase chain reaction (PCR) for amplification of intercellular adhesion gene A (icaA). In S. aureus isolates the icaA gene was present in 65 % while in CNS was 11%. The majority of S. aureus characterized in this study formed biofilm, which suggests that biofilm formation has an important role in the virulence of S. aureus isolated from bovine intramammary infections in Zulia state.
RESUMEN
Objective To investigate the relationship of icaA,aap ,atlE,sarA gene with biofilm phenotype in Staphyloccus epi-dermidis .Methods Tissue culture plates assays were used to assess biofilm-forming ability of 78 Staphyloccus epidermidis strains.The presence of icaA,atlE,aap ,sarA gene was amplified with PCR method,the relationship between these genes and bio-film phenotype was evaluated by χ2 test and the difference of the biofilm OD′s value in TSB and TSB+3% NaCl by icaA + strains and icaA - strains was evaluated by Wilcoxon sign test,respectively.Results The positive rates of icaA,atlE,aap ,sarA gene were 24.4%(19/78),79.5%(62/78),73.8%(57/78),82.1%(64/78),respectively.40 biofilm-positive strains were detected(51.3%), among which 16 strains carried icaA gene,24 strains showed weak biofilm-forming ability.Those genes above with biofilm forma-tion were statistically correlated.Moreover,there was a relation between the icaA gene and the high biofilm-producing phenotype. There was a significant difference between the biofilm OD values in TSB and TSB+3% NaCl by icaA + strains and icaA - strains, respectively.Conclusion Multiple genes are involved in Staphylococcus epidermidis biofilm-positive phenotype,but the icaA gene contributes to the high biofilm-forming phenotype.Biofilm phenotype is also influenced by environmental factors.
RESUMEN
Objective To determine the ability of biofilm formation of Staphylococcus ephtermidis isolates and analyze the correlation between the icaA gene and its expression and biofilm formation. Methods Collecting 205 Staphylococcus epidermidis isolates identified with normal laboratory tests (coagulase-negative, biochemical identification, polymyxin-resistant and novobiocin-sensitive ), the suspected isolates were con-formed with API-Staph. Biofilm production was assessed by incubating the strains on Congo Red Agar (CRA) plates and quantitative biofilm production determined by a 96-well tissue culture plate and biofilm morphous were detected by scanning electron microscope ( SEM ) ; Amplifying partial fragments of icaA genes with PCR; Analyzing the expression levels of icaA gene with RT-PCR through Bio-Rad system and Quantity One software. Results 24 isolates showed positive in CRA tests, 22 isolates were positive in semiquantita- tive adhesion assays and 28 isolates existed icaA gene among 205 isolates of Staphylococcus epidermidis. The icaA-positive strains demonstrated biofilm formation (microcolonies on silica films ) while icaA-negative strains only adhered as individual cells under scanning electron microscope. All 22 strains which showed positive in semiquantitative adhesion assays harbored the icaA gene. The expression levels of icaA gene with RT-PCR in 6 Staphylococcus epidermidis isolates showed a higher tendency in 4 strains which demonstrated positive in semiquantitative adhesion assays than 2 negative strains in semiquantitative adhesion assays. Conclusion The isolations of Staphylococcus epidermidis have the abilities of forming biofilm, and the icaA gene and its normal expression is the important molecular biology foundation of biofilm formation. Other fac-tors maybe involve in the expression of icaA gene in Staphylococcus epidermidis isolates.