Factors Affecting Staphylococcus aureus Colonization of the Nasopharynx in the First 6 Months of Life

Abstract

Background Staphylococcal aureus (SA) colonization in early infancy is common, but the pattern and factors affecting its acquisition and persistence in the first few months of life are not well studied. Objectives To study the rate of SA nasopharyngeal (NP) colonization at monthly intervals in the first six months of life, and its association with environmental and host factors, and other pathogenic NP bacteria. Methods Data from a prospective study were analyzed on bacterial cultures of 1765 NP swabs from 367 infants who were followed from birth to 6 months of age. Demographic, breastfeeding, cigarette smoke exposure and daycare attendance data were collected at each monthly visit. Results The rate of infants colonized with SA was highest at age 1 month (25%) and declined to lowest rate by age 6 months (12%). The proportion of SA strains that was methicillin-resistant (MRSA) was also highest at age 1 month and declined rapidly by age 4 months (18% vs 6%, P = 0.05). Colonization with Streptococcus pneumoniae (SP), nontypeable Haemophilus influenzae (HI) and Moraxella catarrhalis (MC) increased at different rates up to age 6 months. Univariate analysis showed that SA colonization rate was significantly lower with increasing age, black race, day care attendance, and colonization with NTHI, MC and SP (P <0.05). Multivariate analysis showed that this effect was independently associated only with increasing age and MC colonization (P ≤0.05). Furthermore, the time to first acquisition of SA from one month of age onwards was significantly associated with day care attendance, and NTHI and MC colonization. None of the infants colonized with SA developed SA infections through age 6 months. Conclusions SA colonization of NP begins very early in life and declines quickly. MRSA has lower ability to maintain prolonged colonization status than methicillin-susceptible strains in the first 6 months of life. As the NP is colonized with other respiratory bacterial pathogens, the colonization with SA declines; however, this effect is stronger with Gram negative bacteria such as NTHI and MC.

Bacterial Colonization and Antibiotic Resistance in a Prospective Cohort of Newborn Infants During the First Year of Life

“…Five of our 6 infants with S aureus were colonized by 3 months of age, none with MRSA; antibiotic-resistant S aureus was not isolated for 2 consecutive visits from any infant. Previous studies found that staphylococcal colonization was most prevalent early during the first year but tended to report higher prevalence of MRSA, up to 50%, and longer duration of carriage from 24 to 40 months, even with decolonization efforts [23, 24]. Groups believed to be at increased risk of infection with MRSA include neonates and children in general, urban underserved populations, and daycare attendees, all highly represented in our infant population.…”

Nasopharyngeal microbiota in infants and changes during viral upper respiratory tract infection and acute otitis media

“…Our data, although from a small number, suggest that one of the factors preventing AOM development in young infants is colonization with Staphylococcus , which helps counteract with the otopathogens. Our previously published report from this cohort [ 26 ] has shown the highest S . aureus colonization rate (25%) in samples collected at age 1 month, with declining in rate to 12% by age 6 months, along with increasing rates of colonization of S .…”

“…Because S . aureus colonization in young infants is not associated with invasive infections [ 26 – 30 ], Staphylococcus colonization may be beneficial than harmful to these young infants. Not only Staphylococcus protected them from otopathogen colonization but it also helped prevent the transition from URI to AOM.…”

Epidemiological Markers for Interactions AmongStreptococcus pneumoniae,Haemophilus influenzae, andStaphylococcus aureusin Upper Respiratory Tract Carriage

“…We found higher S. aureus carriage among Jewish children, in contrast to higher S. pneumoniae and H. influenzae carriage among Bedouin children. Similarly, in the United States, S. aureus colonization is more prevalent among white, non-Hispanic children and adults in comparison to their black or Hispanic counterparts, among whom S. pneumoniae and H. influenzae carriage is more prevalent [10,29,30]. We also observed reductions in S. aureus carriage at younger ages among Bedouin children, who carried S. pneumoniae and H. influenzae earlier and a Multivariate analyses additionally control for sine and cosine transformations of calendar week, with 4-, 6-, and 12-month periods, stratified by ethnicity (Figure 2).…”