Nasal colonization with MRSA is directly associated with subsequent MRSA infections, according to research published in Antimicrobial Resistance and Infection Control.
Further, the variability observed in colonization and infection efficiency among MRSA genotypes suggests molecular causes for emergence of strains in the community and hospitals should be better defined, according to researchers.
“Our data confirm the link between nasal colonization and clinical MRSA infection and point to the need to better understand the molecular determinants underlying S. aureus emergence, including factors that enhance colonization and infection,” the researchers wrote.
Tara C. Smith, PhD, of the department of epidemiology, University of Iowa College of Public Health, Iowa City, Iowa, and colleagues set out to compare colonization and infection isolates at the Iowa City Veterans Affairs Health Care System and examine the prevalence of livestock-associated MRSA.
The researchers tested all patients with available MRSA isolates gathered from routine nasal screening (73%; n = 397) and infections (27%; n = 148) from December 2010 to August 2012 for spa type and presence of Panton-Valentine leukocidin (PVL) and mecA genes.
The investigators evaluated antibiotic resistance patterns in the clinical isolates, then compared paired colonization and infection isolates for genetic and phenotypic congruity.
The most common spa types were t002 and other CC5-associated strains (65%) and t008 and other CC8-associated strains (20%); no classic livestock-associated MRSA spa types were seen.
CC8-associated strains were more likely to be linked with infections than CC5-associated strains (49%; 53/109 vs. 22%; 77/353).
MRSA colonization was seen more often in patients with infections (71%) compared with the general screening population (7%). Paired colonization and infection isolates were genetically and phenotypically indistinguishable in a majority of cases (82%; 28/34).
“The link between nasal colonization strains and clinical infection strains suggest the need to continue to explore active surveillance and mupirocin decolonization as a means to reduce the burden from MRSA infections,” the researchers wrote.
“Livestock-associated MRSA does not appear to contribute significantly to the prevalence of MRSA colonization or the burden of MRSA infections … despite the high density of livestock in the region.” – by Allegra Tiver
Disclosure: The researchers report no relevant financial disclosures.