MRSA colonization and the nasal microbiome in adults at high risk of colonization and infection.
OBJECTIVE
The objective of this study was to define the nasal microbiome of hospital inpatients who are persistently colonized with methicillin-resistant Staphylococcus aureus (MRSA) compared with matched, non-colonized controls.


METHODS
Twenty-six persistently MRSA-colonized subjects and 26 matched non-colonized controls were selected from the screening records of the infection control program at the Department of the Veteran Affairs Eastern Colorado Health Care System (VA-ECHCS). The nasal microbiotas were analyzed with PCR amplification and sequencing of the 16S ribosomal RNA (rRNA) gene. Comparison of all variables across the groups was performed using stratified logistic regression to account for the one-to-one matching. Canonical discriminant analysis was performed to assess differences in bacterial community across the two groups. Competing organisms were cocultured with MRSA in vitro.


RESULTS
There was a negative association between MRSA colonization and colonization with Streptococcus spp. At the species level, multivariate analysis demonstrated a statistically significant negative association between colonization with Streptococcus mitis or Lactobacillus gasseri and MRSA. Coculture experiments revealed in vitro competition between S. mitis and all of the 22 MRSA strains isolated from subjects. Competition was blocked by addition of catalase to the media. Persistently colonized subjects had lesser microbial diversity than the non-colonized controls.


CONCLUSIONS
In a high-risk inpatient setting, bacterial competition in the nasal niche protects some patients from MRSA colonization.
Division of Adult Infectious Diseases, University of Colorado Denver, Aurora, CO, USA; Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA. Electronic address: Mary.Bessesen@ucdenver.edu.
Mary T
MT
Bessesen
Division of Adult Infectious Diseases, University of Colorado Denver, Aurora, CO, USA; Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA.
Cassandra Vogel
CV
Kotter
Department of Biostatistics and Informatics, Colorado School of Public Health, University of Colorado Denver, Aurora, CO, USA; Microbiome Research Consortium (MiRC), University of Colorado Denver, Aurora, CO, USA.
Brandie D
BD
Wagner
Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA.
Jill C
JC
Adams
Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA.
Shannon
S
Kingery
Division of Adult Infectious Diseases, University of Colorado Denver, Aurora, CO, USA; Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA; Microbiome Research Consortium (MiRC), University of Colorado Denver, Aurora, CO, USA.
Jeanne B
JB
Benoit
Division of Adult Infectious Diseases, University of Colorado Denver, Aurora, CO, USA; Microbiome Research Consortium (MiRC), University of Colorado Denver, Aurora, CO, USA.
Charles E
CE
Robertson
Division of Adult Infectious Diseases, University of Colorado Denver, Aurora, CO, USA; Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA; Microbiome Research Consortium (MiRC), University of Colorado Denver, Aurora, CO, USA; Mucosal and Vaccine Research Program Colorado (MAVRC), University of Colorado Denver, Aurora, CO, USA.
Edward N
EN
Janoff
Division of Adult Infectious Diseases, University of Colorado Denver, Aurora, CO, USA; Department of Veterans Affairs Eastern Colorado Healthcare System, Denver, CO, USA; Microbiome Research Consortium (MiRC), University of Colorado Denver, Aurora, CO, USA; Mucosal and Vaccine Research Program Colorado (MAVRC), University of Colorado Denver, Aurora, CO, USA.
Daniel N
DN
Frank
D000328:Adult; D000898:Antibiosis; D002353:Carrier State; D002374:Catalase / Q000378:metabolism; D005260:Female; D006760:Hospitalization; D006801:Humans; D007778:Lactobacillus / Q000187:drug effects / Q000302:isolation & purification / Q000502:physiology; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology*; D064307:Microbiota; D009666:Nose / Q000382:microbiology*; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S; D012307:Risk Factors; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000302:isolation & purification / Q000502:physiology; D034361:Streptococcus mitis / Q000302:isolation & purification / Q000502:physiology
D012336:RNA, Ribosomal, 16S; D002374:Catalase
Bacterial interference; Lactobacillus gasseri; Methicillin-resistant Staphylococcus aureus; Microbiome; Streptococcus mitis