Population Biology of Intestinal Enterococcus Isolates from Hospitalized and Nonhospitalized Individuals in Different Age Groups

Abstract

ABSTRACTThe diversity of enterococcal populations from fecal samples from hospitalized (n= 133) and nonhospitalized individuals (n= 173) of different age groups (group I, ages 0 to 19 years; group II, ages 20 to 59 years; group III, ages ≥60 years) was analyzed. Enterococci were recovered at similar rates from hospitalized and nonhospitalized persons (77.44% to 79.77%) of all age groups (75.0% to 82.61%).Enterococcus faecalisandEnterococcus faeciumwere predominant, although seven otherEnterococcusspecies were identified.E. faecalisandE. faecium(including ampicillin-resistantE. faecium) colonization rates in nonhospitalized persons were age independent. For inpatients,E. faecaliscolonization rates were age independent, butE. faeciumcolonization rates (particularly the rates of ampicillin-resistantE. faeciumcolonization) significantly increased with age. The population structure ofE. faeciumandE. faecaliswas determined by superimposing goeBURST and Bayesian analysis of the population structure (BAPS). MostE. faeciumsequence types (STs; 150 isolates belonging to 75 STs) were linked to BAPS groups 1 (22.0%), 2 (31.3%), and 3 (36.7%). A positive association between hospital isolates and BAPS subgroups 2.1a and 3.3a (which included major ampicillin-resistantE. faeciumhuman lineages) and between community-based ampicillin-resistantE. faeciumisolates and BAPS subgroups 1.2 and 3.3b was found. MostE. faecalisisolates (130 isolates belonging to 58 STs) were grouped into 3 BAPS groups, BAPS groups 1 (36.9%), 2 (40.0%), and 3 (23.1%), with each one comprising widespread lineages. No positive associations with age or hospitalization were established. The diversity and dynamics of enterococcal populations in the fecal microbiota of healthy humans are largely unexplored, with the available knowledge being fragmented and contradictory. The study offers a novel and comprehensive analysis of enterococcal population landscapes and suggests thatE. faeciumpopulations from hospitalized patients and from community-based individuals differ, with a predominance of certain clonal lineages, often in association with elderly individuals, occurring in the hospital setting.