Genomic Epidemiology of Methicillin-resistant Staphylococcus aureus in a Neonatal Intensive Care Unit
Methods: Since 2004, we have performed admission and weekly MRSA screening of all infants admitted to the level III NICU in Jacksonville, FL (AJIC 2011;39:35-41). Isolates from infants (n=411) were spa-typed to characterize prevalent strains within the NICU. Strains identified as spa-type t008 (n=55), representing the prevalent CA-MRSA lineage, and spa-type t045 (n=41), representing the prevalent HA-MRSA lineage, underwent WGS and phylogenetic analysis to understand the putative replacement of HA- strains and to assess the endemnicity of CA strains within the unit. Infant demographic and clinical data were extracted electronically.
Results: A total of 5,212 infants were admitted to the NICU during the study period (2004-2011) representing 128,422 patient days (pd). The colonization prevalence among infants was 3.62 per 1000 pd. Preliminary epidemiological and phylogenetic analysis of spa-type t008 and t045 strains demonstrated a complex dynamic marked by both multiple introductions of t008 strains and putative nosocomial transmission as suggested by different individuals having nearly identical MRSA WGS.
Conclusion: Our findings show evidence of multiple introductions of MRSA into the NICU, possibly due to increasing community-wide prevalence resulting in greater colonization pressure from patients, staff, and visitors. Given that spa-typing alone cannot distinguish introductions from the community vs. nosocomial transmission (i.e. sporadic vs. epidemic cases), WGS should be used as the gold standard to investigate the emergence and transmission of MRSA and to inform evidence-based, targeted control measures.
M. Rathore, None
C. Bailey, None
D. Halstead, None
R. Cook, None
J. Johnson, None
J. G. Morris, None
M. Salemi, None