RESUMO
This study assessed the adhesion and formation of biofilm by five Salmonella enterica strains (S. Enteritidis 132, S. Infantis 176, S. Typhimurium 177, S. Heidelberg 281 and S. Corvallis 297) on polypropylene (PP) and glass (G) surfaces as affected by pH (4-7), NaCl concentration (0-10% w/v) and temperature (8-35⯰C). Sessile counts <3 log CFU/cm2 were considered lack of adhesion (category 1), while countsâ¯≥â¯3 andâ¯<â¯5 log CFU/cm2 corresponded to adhesion (category 2) and countsâ¯≥â¯5 log CFU/cm2 corresponded biofilm formation (category 3). The obtained results categorized in these three responses were used to develop ordinal regression models to predict the probability of biofilm stages on PP- and G-surfaces. The experimental outcomes for lack of adhesion were >90% on PP- and G-surfaces. Generally, adhesion outcomes corresponded to approximately 36% of the total, whereas biofilm outcomes were close to 65% in both PP- and G-surfaces. The biofilm stages varied among the strains studied and with the material surface under the same experimental conditions. According to the generated ordinal models, the probability of adhesion and biofilm formation on PP-surface by the five S. enterica strains tested decreased at pH 4 or 5 in NaCl concentrations >4% and at a temperature <20⯰C. On G-surface, the probability of adhesion increased pH 6 or 7, in the absence of NaCl and temperatures <20⯰C, while, the probability of biofilm formation increased in the same pH, NaCl concentration up to 4% and temperatures ≥20⯰C. This is the first study assessing the biofilm formation through categorical, ordinal responses and it shows that ordinal regression models can be useful to predict biofilm stages of S. enterica as a function of pH, NaCl, and temperature or their interactions.
Assuntos
Biofilmes , Vidro , Polipropilenos , Salmonella enterica/fisiologia , Cloreto de Sódio/farmacologia , Temperatura , Aderência Bacteriana , Contagem de Colônia Microbiana , Concentração de Íons de Hidrogênio , Modelos Logísticos , Análise de Regressão , Salmonella enterica/efeitos dos fármacosRESUMO
This study aimed to assess the capability of 97 epidemic S. enterica strains belonging to 18 serovars to form biofilm. Five strains characterized as strong biofilm-producers, belonging to distinct serovars (S. Enteritidis 132, S. Infantis 176, S. Typhimurium 177, S. Heidelberg 281 and S. Corvallis 297) were assayed for adhesion/biofilm formation on stainless steel surfaces. The experiments were conducted in different combinations of NaCl (0, 2, 4, 5, 6, 8 and 10% w/v), pH (4, 5, 6 and 7) and temperatures (8⯰C, 12⯰C, 20⯰C and 35⯰C). Only adhesion was assumed to occur when S. enterica counts were ≥3 and <5â¯logâ¯CFU/cm2, whereas biofilm formation was defined as when the counts were ≥5â¯logâ¯CFU/cm2. The binary responses were used to develop models to predict the probability of adhesion/biofilm formation on stainless steel surfaces by five strains belonging to different S. enterica serovars. A total of 99% (96/97) of the tested S. enterica strains were characterized as biofilm-producers in the microtiter plate assays. The ability to form biofilm varied (Pâ¯<â¯0.05) within and among the different serovars. Among the biofilm-producers, 21% (20/96), 45% (43/96), and 35% (34/96) were weak, moderate and strong biofilm-producers, respectively. The capability for adhesion/biofilm formation on stainless steel surfaces under the experimental conditions studied varied among the strains studied, and distinct secondary models were obtained to describe the behavior of the five S. enterica tested. All strains showed adhesion at pHâ¯4 up to 4% of NaCl and at 20⯰C and 35⯰C. The probability of adhesion decreased when NaCl concentrations were >8% and at 8⯰C, as well as in pH valuesâ¯≤â¯5 and NaCl concentrationsâ¯>â¯6%, for all tested strains. At pHâ¯7 and 6, biofilm formation for S. Enteritidis, S. Infantis, S. Typhimurium, S. Heidelberg was observed up to 6% of NaCl at 35⯰C and 20⯰C. The predicted boundaries for adhesion were pH valuesâ¯<â¯5 and NaClâ¯≥â¯4% and at temperatures <20⯰C. For biofilm formation, the predicted boundaries were pH valuesâ¯<â¯5 and NaCl concentrationsâ¯≥â¯2% and at temperatures <20⯰C for all strains. The secondary models obtained describe the variability in boundaries of adhesion and biofilm formation on stainless steel by five strains belonging to different S. enterica serovars. The boundary models can be used to predict adhesion and biofilm formation ability on stainless steel by S. enterica as affected by pH, NaCl and temperature.