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Factors Affecting Staphylococcus aureus Colonization of the Nasopharynx in the First 6 Months of Life
Janak A Patel1, Pedro Alvarez-Fernandez, Kristofer Jennings
1From the *Department of Pediatrics, †Department of Preventive Medicine and Community Health, ‡Department of Pathology, University of Texas Medical Branch, Galveston, Texas.
Insights
Staphylococcus aureus (SA) colonization in infants peaks at 1 month and declines by 6 months. Co-colonization with other bacteria, particularly Gram-negative species like Moraxella catarrhalis, is associated with reduced SA persistence.
Area of Science:
- Pediatric Infectious Diseases
- Microbiology
- Epidemiology
Background:
- Staphylococcus aureus (SA) colonization is common in early infancy, but patterns and influencing factors require further study.
- Understanding the dynamics of SA acquisition and persistence is crucial for public health interventions.
Purpose of the Study:
- To investigate the rate of SA nasopharyngeal (NP) colonization monthly during the first 6 months of life.
- To identify environmental, host, and co-pathogen factors associated with SA colonization patterns.
Main Methods:
- Prospective cohort study analyzing NP bacterial cultures from 367 infants up to 6 months of age.
- Monthly data collection on demographics, breastfeeding, smoke exposure, and day care attendance.
- Analysis of co-colonization with Streptococcus pneumoniae, nontypeable Haemophilus influenzae, and Moraxella catarrhalis.
Main Results:
- SA colonization peaked at 25% at 1 month, declining to 12% by 6 months.
- Methicillin-resistant SA (MRSA) proportion decreased from 18% at 1 month to 6% by 4 months.
- Increasing age and Moraxella catarrhalis (MC) colonization were independently associated with lower SA rates; day care attendance and NTHI/MC colonization influenced acquisition time.
Conclusions:
- Infant SA NP colonization is established early and diminishes rapidly.
- Methicillin-susceptible SA demonstrates better persistence than MRSA strains in early infancy.
- Co-colonization with other respiratory pathogens, especially Gram-negative bacteria like NTHI and MC, inhibits SA colonization.
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. The aim is to study the rate of SA nasopharyngeal (NP) colonization at monthly intervals in the first 6 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 day care 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 SA 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 (NTHI) 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. Methicillin-resistant SA 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.
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