Methicillin Resistant Staphylococcus aureus (MRSA) ST 398 and gut microbiota: interspecies interactions into the mucus layer of ascendant colon

Abstract

[Statement of the Problem]: Intestinal mucus layer may provide a niche for many nosocomial pathogens, including S. aureus which can occasionally cause a Staphylococcal enterocolitis. Recent exciting researches support the notion that a healthy intestinal microbiota composition can promote resistance to invading pathogenic bacterial species.

[Purpose]: The purpose of this study was to evaluate the survival of MRSA in simulated human ascendant colon conditions and its interaction with gut microbiota into the mucus layer.

[Methodology and Theoretical Orientation]: The study was performed at ascendant colon environment: body-like temperature (37ºC), anaerobiosis (N2), pH 5.7, constant slow shaking (40 RPM). Mucin agar carriers stand for the intestinal mucus layer and a basic feed medium represented the intestinal lumen contents. A three-days long in vitro study was performed by using microbiota from pooled faeces of healthy individuals that were stabilized simulating ascendant colon conditions and a MRSA strain of animal origin (ST398-t011-SCCmecV; 107 UFC/mL). Each day we checked the viability of MRSA both into the mucin agar carriers and in the feed medium by using MRSA-SELECTplates (BioRad). The results were confirmed by quantitative PCR.

[Findings]: MRSA population decreased as a function of time during the incubation with luminal colon microbiota where it was not viable after 24 h. Counts of 4 log cfu/g were still obtained in the mucin agar carriers after 72 h of incubation. On the other hand, counts of Bifidobacterium and Akkermansia increased in the mucin agar carriers as a function of time.

[Conclusion and Significance]: The results support the hypothesis that a competitive microbiota may control MRSA intestinal colonization empathize the important role of specific groups which can inhibit the adhesion of/displace MRSA from the intestinal mucus layer.