Expressão diferencial da proteína internalina A em Listeria monocytogenes do sorotipo 4b de diferentes origens em caldos de enriquecimento seletivos e não-seletivos

Abstract

Listeria monocytogenes is an infectious microorganism causing listeriosis, a foodborne illness affecting immunocompromised, pregnant, elderly and childrens. Pathogenic to men and animals is found naturally in the environment and has the ability to multiply on adverse conditions such as high salinity and chilling temperatures. However, their detection in food is difficult because it is laborious, time consuming and expensive. Therefore comes to searching for methods to detect simple and fast. Immunological methods are very promising in this regard, but the conditions under which the organism is grown should be ideal for maximizing the expression and subsequent detection of the target antigen. Internalin A protein (InlA) of L. monocytogenes is an excellent target for detection of this pathogen in immunological tests, but the ideal conditions to enhance its expression had not yet been described. Therefore thus study analyzed the expression of InlA in two strains of L. monocytogenes serotype 4b, a clínical and other non-clínical, in non selective enrichment broths Luria-Bertani (LB), Brain Heart Infusion (BHI), Tryptic Soy Broth (TSB) and selective broths Fraser Broth (FRA), Listeria Enrichment Broth (LEB), Listeria Enrichment Broth - University of Vermont Medium (UVM), to incubation at 29 and 37 °C, through the ELISA and real time RT-PCR. All data were statistically analyzed considering a significance level of 5% (p <0.05). In the ELISA it was found that expression of InlA is strain-specific, in other words, was influenced by the origin of the strain, because the strain non-clínical of L. monocytogenes showed higher InlA expression levels than the clínical strain, and the medium used directly interfere with the expression of this antigen, and the most appropriate medium of enrichment for use in detection methods, regardless of the origin of the strain,was FRA, TSB and LEB. It was also observed that there was no significant difference in the expression of InlA when strains were grown at 29 and 37 °C. The real-time RT-PCR data showed inconclusive, since there was no statistically significant difference between the conditions analyzed, requiring thus more study. In conclusion, it was found that InlA gene expression on influenced by origin of the strain and culture media. Regardless of the origin of the strain, the preferred media for use in InlA protein detection methods are FRA, TSB and LEB