Non-pathogenic bacterial flora may inhibit colonization by methicillin-resistant Staphylococcus aureus in extremely low birth weight infants.

OBJECTIVES

To evaluate our hypothesis that non-pathogenic bacterial flora inhibit later colonization with methicillin-resistant Staphylococcus aureus (MRSA) in extremely low birth weight (ELBW) infants, we performed a retrospective investigation of the association between non-pathogenic bacterial flora and later inhibition of colonization by MRSA in ELBW infants.

METHODS

A total of 110 preterm infants with birth weight <1,000 g admitted to the Neonatal Intensive Care Unit of Nagano Children's Hospital from January 1997 to December 2003 were analyzed retrospectively with regard to colonization by MRSA during hospitalization. We investigated the incidence of MRSA colonization in 56 infants with non-pathogenic bacterial flora in the oral cavity during the first week after birth and compared them with 54 infants lacking non-pathogenic bacteria.

RESULTS

Incidence rate of colonization by MRSA at postnatal week 6 was significantly lower in infants with non-pathogenic bacterial flora in the oral cavity (32.1%) than in infants without such bacteria during the first week of life (77.8%; p < 0.001).

CONCLUSIONS

The present results suggest an important role for non-pathogenic bacterial flora in the oral cavity during early life in prevention of later MRSA colonization in ELBW infants.