Discordance between Staphylococcus aureus isolates cultured from
nasal and wound sites and discrepancies between nasal colonization status and
incidence of recurrent infections among children suggested that nasal
colonization may not be an accurate marker for predicting which children are at
risk for recurrent community-associated methicillin-resistant Staphylococcus
aureus skin infections.
Researchers obtained cultures from 95 children, 93% of whom were black, with skin and soft tissue
infections participating in a trial conducted to compare cephalexin and
clindamycin as outpatient treatments.
MRSA was isolated from the wounds of 83 patients and from the nares of
40 patients. S. aureus was isolated from both wound and nasal cultures
in 39 patients, but only 23 had isolates with identical methicillin
susceptibility and pulsed field gel electrophoresis type from both sites.
“A striking 33% of our patients either grew MRSA from their wound but
methicillin-susceptible S. aureus from their nose or MSSA from their
wound but MRSA from their nose,” the researchers wrote.
Furthermore, patients with MRSA isolates obtained from nasal culture
after initial skin infection had a 19% recurrence risk compared with the 42%
recurrence risk observed in patients without MRSA-positive nasal cultures.
“Taken together, these findings suggest that for
community-[associated] skin and soft tissue infections, wound infection by MRSA
— rather than nasal colonization with MRSA — may be a better
predictor of children at higher risk of subsequent skin and soft tissue
infection,” the researchers wrote. – by Nicole Blazek
Chen AE. Pediatr Infect Dis J.
2009;doi:10.1097/INF.0b013e31818cb0c4.
This is a small study involving mostly black children from a limited geographic area. A lot more work
still needs to be done in different settings, because there are clearly
differences between geographic areas and even within the same city. With the
percentage of MRSA we’re isolating in three different hospitals here in
New Orleans, there’s a difference of up to 40% between two of the
hospitals.
This study suggests that patients are getting recurrences of MRSA infections from sources other than
the nose, which we knew anyway because risk factors include close body contact
with people that are infected, contaminated fomites or sports equipment. We should use caution in our
interpretation until there are more data.
– George A. Pankey, MD
Ochsner Clinic Foundation, New Orleans