Del Rio Ramos, Christian

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    Temporal analysis and molecular characterization of dominant enterococcus strains present in feces from healthy human subjects
    (2017) Del Rio Ramos, Christian; Ríos Hernández, Luis A.; College of Arts and Sciences - Sciences; Rodríguez Minguela, Carlos; Ortíz Acevedo, Alejandro; Department of Biology; Mazak, Catherine
    The human intestinal microflora is an intricate environment where bacteria, viruses, fungi and the immune system interact. While the Enterococci are described as intestinal commensals, traits like the presence of chromosomal or mobile virulence factors and antibiotic resistance determinants have also lead to their classification as opportunistic pathogens. This group comprises around 1% of the total human intestinal flora and little is known about the population dynamics in terms of species or strain dominance. Although studies have focused on intestinal carriage and survival of specific strains (Sørensen, 2001; Lund, 2002; Sohn, 2013), there is little data on the natural population in healthy humans. Herein the dominant enterococci populations in healthy humans (not medicated for chronic illness nor antibiotic intake one month prior or during the sampling period) are described. These were recovered from stool samples of 3 healthy male subjects aged 18-25 years. A total of 140 isolates per subject were obtained during a sampling period of 7 consecutive days. Isolates were subjected to antibiotic resistance screening, molecular species ID, presence of virulence factors, plasmid families and strain characterization. Analysis showed that all three subjects carried different dominant enterococci but these were specifically limited to E. faecalis and E. faecium. Subject #1 was dominated by two distinct species, a commensal E. faecium or a Vancomycin Resistant E. faecalis. Only E. faecalis was present in Subject #2 and appears mostly commensal with esp as its sole virulence factor. However, for subject #3's isolates, we saw an increase in the pathogenic potential, a Tetracycline Resistant E. faecalis with the potential to carry Vancomycin resistance and 2 virulence factors. Data suggests that the intestinal diversity of enterococci is subject dependent, as there are different dominant strains in each subject; from commensal strains to strains with a higher frequency of antibiotic resistance and virulence factors that are similar to clinical strains. The presence of pathogenic strains in healthy humans reinforces the importance of studying humans as antibiotic resistance reservoirs as well as the prudent use of antibiotics. Intestinal carriage of pathogenic strains and the high turnover rate of strains can be of importance as species of concern may not be detected during culture cased screenings carried out before surgical procedures.