1166. Methicillin-Resistant Staphylococcus aureus in Mother-Infant Couplets
Session: Poster Abstract Session: Staphylococcus aureus Infections in Children
Saturday, October 22, 2011
Room: Poster Hall B1
Background: 

At a 185-bed children’s hospital in northern Virginia, admissions of infants less than one year of age for methicillin-resistant Staphylococcus aureus (MRSA) infections increased from 2 in 1997 to 25 in 2006.  Of these infections, 25% occurred by 30 days of life with 63% occurring by four months.  From 2004 to 2006, hospital associated (HA-MRSA) USA100 and community associated (CA-MRSA) USA300 accounted for 31% and 56% of infections, respectively. However, during the first 60 days of life, all MRSA infections were caused by USA300.  A prospective study was performed to evaluate for mother-infant transmission of USA300  at parturition.

Methods: 

Nasopharyngeal (NP) and recto-vaginal (RV) swabs were obtained from consented mothers before delivery (L&D).  NP and combined umbilical/anal (UA) swabs were obtained on infants at delivery, discharge, and 1 month.  Breast milk was collected at 1 month in nursing mothers.  Couplets with MRSA positive mother and/or baby were re-cultured at 2, 4, 6, 9, and 12 months. Bio-Rad MRSA Select™ agar was used to culture organisms.  PFGE was performed when MRSA was found.

Results: 

Of 153 enrolled couplets, 3.3% (5/153) were positive for MRSA by 1 month, with 80% (4/5) positive for USA100 and 20% (1/5) positive for USA700, a clone associated with both HA- and CA-MRSA infections. Initial positive cultures were found in 2 (1.3%) mothers in L&D and 3 (2.0%)  previously negative infants: 1 at discharge and 2 at 1 month.  In 2/5 couplets, both mother and infant were concordant with identical PFGE types:  one mother with USA700 on NP/RV swabs in L&D whose infant became positive at 1 month, and one infant with USA100 on NP/UA swabs at hospital discharge whose mother became positive at 2 months.  In both cases, breast milk was also positive.  There were no invasive infections among colonized couplets. USA100 MRSA among the 4 couplets exhibited slightly different PFGE banding patterns.

Conclusion: 

  1. By one month after delivery, 3.3% of mothers and/or infants are colonized with MRSA.
  2. MRSA transmission can occur from mother to infant and from infant to mother.
  3. Colonization by HA-MRSA PFGE types may occur commonly in the community setting.
  4. In our cohort, the source for USA300 infections in young infants still remains unknown. 

Subject Category: P. Pediatric and perinatal infections

Karen Carpenter, MD1, Mahvash Mujahid, BS2, Neema Hardeman, BS2, Kathi Huddleston, PhD1 and David Ascher, MD1, (1)Department of Pediatrics, Inova Fairfax Hospital for Children, Falls Church, VA, (2)Virginia Commonwealth University School of Medicine, Falls Church, VA

Disclosures:

K. Carpenter, None

M. Mujahid, None

N. Hardeman, None

K. Huddleston, None

D. Ascher, None

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