Risk Factors for Early Infant Colonization With Methicillin-Resistant Staphylococcus Aureus

The prevalence of Methicillin-resistant Staphylococcus aureus (MRSA) colonization and
infections have been increasing in the general population, including the pediatric
population. It has been reported that MRSA colonization persists for up to four years, and
therefore the youngest pediatric patients, specifically those who are less than 2 years of
age, have a high risk of prolonged colonization during a period of time when they are
susceptible to significant skin and soft tissue infections (SSTIs) attributable to MRSA.
Once prolonged colonization takes place, recurrent SSTIs are commonplace, resulting in
substantial morbidity and in some cases mortality, as well as a significant cost to the
healthcare system. Individuals colonized with MRSA have an increased risk of developing MRSA
infections, which range from mild disease, such as carbuncles, to severe infections, such as
necrotizing pneumonia and toxic shock syndrome. The prevalence of severe MRSA infections is
also greatest in neonates and infants, where increased MRSA colonization has been observed.
In the early infant period, the most common manifestation of MRSA disease is pustular skin
lesions, which affect approximately 5% of the general population, with MRSA-colonization
being a major risk factor for this disease. Moreover, the prevalence of pustular disease is
increasing in the general population, and there are numerous case reports of invasive,
life-threatening MRSA disease in the early infant period.

Corresponding to the increasing prevalence in the community, the carriage of MRSA in
pregnant women has also escalated, and vaginal carriage is significant in pregnant women. As
an analogy, maternal vaginal Group B Streptococcal (GBS) colonization is the major risk for
infant colonization regardless of whether early or late neonatal colonization or disease
occurs. It is quite feasible that vaginal MRSA carriage predisposes newborns to colonization
during the birthing process; however, this mechanism has not yet been well studied. There
are other mechanisms implicated for early infant colonization, including close contact with
MRSA-colonized mothers through daily care and breastfeeding. MRSA colonization in one
household member greatly predisposes colonization in others; therefore, early infant
colonization could result from contact with other MRSA-colonized individuals in a household.
Currently, it is not clear which factors are the most important in influencing early infant
MRSA colonization and subsequent infection.

Not only is the prevalence of MRSA colonization and infection on the rise, but there have
been few if any measures that have been established to prevent colonization and subsequent
infection in adults and children. Eradication measures have shown limited long-term benefit.
If vertical transmission of MRSA can be established as a critical event in the pathogenesis
of disease, potentially effective strategies could be tested, and possibly the spread of
MRSA in the community interrupted.

Hypotheses and Specific Aims:

1. Identify the proportion, rate and time of MRSA colonization in infants born to mothers
with and without MRSA colonization;

2. Compare risk factors for infant MRSA colonization in these two groups;

3. Determine the prevalence and risk factors for developing MRSA infections in the
MRSA-colonized infant.