Molecular epidemiology of methicillin-resistant Staphylococcus aureus (MRSA) among patients admitted to adult intensive care units: the STAR*ICU trial.
BACKGROUND
The multicenter, cluster-randomized Strategies to Reduce Transmission of Antimicrobial Resistant Bacteria in Intensive Care Units (STAR*ICU) trial was performed in 18 U.S. adult intensive care units (ICUs). It evaluated the effectiveness of infection control strategies to reduce the transmission of methicillin-resistant Staphylococcus aureus (MRSA) colonization and/or infection. Our study objective was to examine the molecular epidemiology of MRSA and assess the prevalence and risk factors for community acquired (CA)-MRSA genotype nasal carriage at the time of ICU admission.


METHODS
Selected MRSA isolates were subjected to molecular typing using pulsed-field gel electrophoresis.


RESULTS
Of 5,512 ICU patient admissions in the STAR*ICU trial during the intervention period, 626 (11%) had a nares sample culture result that was positive for MRSA. A total of 210 (34%) of 626 available isolates were selected for molecular typing by weighted random sampling. Of 210 patients, 123 (59%) were male; mean age was 63 years. Molecular typing revealed that 147 isolates (70%) were the USA100 clone, 26 (12%) were USA300, 12 (6%) were USA500, 8 (4%) were USA800, and 17 (8%) were other MRSA genotypes. In a multivariate analysis, patients who were colonized with a CA-MRSA genotype (USA300, USA400, or USA1000) were less likely to have been hospitalized during the previous 12 months (PR [prevalence ratio], 0.39 [95% confidence interval (CI), 0.21-0.73]) and were less likely to be older (PR, 0.97 [95% CI, 0.95-0.98] per year) compared with patients who were colonized with a healthcare-associated (HA)-MRSA genotype.


CONCLUSIONS
CA-MRSA genotypes have emerged as a cause of MRSA nares colonization among patients admitted to adult ICUs in the United States. During the study period (2006), the predominant site of CA-MRSA genotype acquisition appeared to be in the community.
Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia 30303, USA.
Nisha
N
Nair
Ekaterina
E
Kourbatova
Katharine
K
Poole
Charmaine M
CM
Huckabee
Patrick
P
Murray
W Charles
WC
Huskins
Henry M
HM
Blumberg
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002353:Carrier State; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000235:genetics; D003428:Cross Infection / Q000453:epidemiology / Q000235:genetics; D005260:Female; D005838:Genotype; D006801:Humans; D017053:Infection Control; D007362:Intensive Care Units; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics*; D008875:Middle Aged; D015999:Multivariate Analysis; D009666:Nose / Q000382:microbiology; D010343:Patient Admission; D015995:Prevalence; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000635:transmission; D014481:United States / Q000453:epidemiology; D055815:Young Adult