Our objective was to characterize methicillin-resistant Staphylococcus aureus (MRSA) strains recovered from the nares during active surveillance in the neonatal intensive care unit (NICU), with a focus on the frequency of community-associated (CA) MRSA strain types.
Nasal MRSA isolates (n=250) from 96 patients were recovered from 2009-2014 by active surveillance (at admission and then weekly) in the St. Louis Children's Hospital NICU. Staphylococcal cassette chromosome mec (SCCmec) characterization was performed by multiplex PCR. PCR was also used to detect mupA (marker of high-level mupirocin resistance) and qacA/B (marker associated with chlorhexidine resistance). Medical chart review was performed to assess risk factors associated with CA- or hospital-associated (HA) MRSA strain types.
Fourteen (15%) neonates were colonized at their first sampling. The median [range] time to colonization of those not colonized at baseline was 18 days [4-133]. Neonates born outside the hospital system were more likely to be colonized at baseline (33% vs. 0%, p<0.001) than those inborn. Over half (n=51) of neonates tested positive for MRSA multiple times during their stay (median 2 [range 1-23]). Of 96 subjects, 60 (63%) were colonized with CA-MRSA strain types (59 SCCmec type IV, 1 SCCmec type V) and 35 (37%) were colonized with HA-MRSA strain types (SCCmec type II) (Figure).
Neonates colonized with HA-MRSA were more likely to be born outside the hospital system (60% vs. 37%, p=0.03), colonized at admission to the NICU (29% vs. 7%, p=0.004), intubated during their stay (84% vs. 56%, p=0.02), and of Caucasian race (74% vs. 50%, p=0.02) than those with CA-MRSA. Neonates colonized with CA-MRSA were more likely to have mothers prescribed peripartum antibiotics than those colonized with HA-MRSA (70% vs. 42%, p=0.04).
Eleven (4%) and 8 (3%) isolates were resistant to mupirocin and chlorhexidine, respectively. HA-MRSA isolates were more likely to be mupirocin resistant than CA-MRSA isolates (8% vs. 2%, p=0.02). CA-MRSA isolates were more likely to be chlorhexidine resistant than HA-MRSA isolates (5% vs. 1%, p=0.047). No isolates were resistant to mupirocin and chlorhexidine.
CA-MRSA strains are prominent in the NICU setting.
P. G. Hogan, None
A. Johnson, None
M. Wallace, None
B. Warner, None
C. A. D. Burnham, None
S. Fritz, None