The hidden microbiome of hospital infection surveillance testing: biomarkers of health outcomes in MRSA and VRE colonization

Background: Hospital-acquired infections present a major concern for healthcare systems in the U.S. and worldwide. Drug-resistant infections result in increased costs and prolonged hospital stays. Methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) are responsible for many drug-resistant infections in the U.S. We undertook two parallel studies aimed to investigate the differences in the microbial communities of individuals colonized with MRSA (or VRE) as compared to their respective non-colonized counterparts matched for age, sex, race, ethnicity, unit of admission, and diagnostic-related group, when available.

Results: The VRE study showed considerably more Enterococcus genus communities in the VRE colonized samples. Our findings for both MRSA and VRE studies suggest a strong association between 16S rRNA gene alpha diversity, beta diversity, and colonization status. When we assessed the colonized microbial communities in isolation, the differences disappeared, suggesting that the colonized microbial communities drove the change. Isolating Staphylococcus, we saw significant differences expressed across colonization in specific sequence variants.

Conclusions: The differences seen in the microbial communities from MRSA (or VRE) colonized samples as compared to non-colonized match-pairs are driven by the isolated communities of the Staphylococcus (or Enterococcus) genus, the removal of which results in the disappearance of any differences in the diversity observed across the match-pairs.