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Epidemiology of pharyngeal colonization of infants with aerobic gram-negative rod bacteria
R S Baltimore1, R L Duncan, E D Shapiro
1Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut 06510.
Insights
Pharyngeal colonization with gram-negative rods (GNR) increases significantly in infants by 4.5 months. Breastfed infants show lower GNR prevalence compared to formula-fed infants.
Area of Science:
- Microbiology
- Pediatrics
- Neonatology
Background:
- Pharyngeal colonization by gram-negative rod (GNR) bacteria is a concern in infant health.
- Understanding GNR prevalence in healthy infants is crucial for interpreting colonization in clinical settings.
Purpose of the Study:
- To determine the prevalence and patterns of pharyngeal GNR colonization in healthy infants from birth to six months.
- To compare GNR colonization rates between breastfed and formula-fed infants.
- To establish baseline GNR colonization data for healthy infants to aid in evaluating ill or hospitalized infants.
Main Methods:
- A cohort of 49 normal infants was monitored from birth to 6 months.
- Pharyngeal swabs were collected and cultured on a selective medium for GNR quantitation.
- Statistical analysis was performed to compare colonization rates based on feeding method and infant health status.
Main Results:
- GNR prevalence increased from 8% in the first 72 hours to a peak of 67% at 4.5 months.
- Common GNR species included Klebsiella, Escherichia coli, Enterobacter, and Acinetobacter anitratus.
- Breastfed infants had significantly lower GNR colonization rates (26%) compared to formula-fed infants (45%).
Conclusions:
- Pharyngeal GNR colonization is common and increases with age in healthy infants.
- Breastfeeding appears to be a protective factor against GNR colonization.
- Established data on healthy infant GNR carriage are essential for clinical interpretation in non-healthy infants.
Abstract:
By using a selective medium, pharyngeal colonization with gram-negative rod (GNR) bacteria was determined in a cohort of 49 normal infants monitored from birth to 6 months of age. Culture swabs were diluted in 1 ml of saline for quantitation. The prevalence of GNR in the first 72 h of life was 8% and rose to 29% during the first month, 52% at 2.5 months, 67% at 4.5 months, and 62% at 6 to 7 months. Colonization was with substantial numbers of organisms, generally greater than 100 colonies per ml and frequently greater than 1,000 colonies per ml. The most common species were Klebsiella species, Escherichia coli, Enterobacter species, and Acinetobacter anitratus. Fewer infants who were breast fed rather than formula fed at the time of culture harbored GNR (26 versus 45%, P less than 0.05). The point prevalence of pharyngeal GNR colonization in our special care nursery was 12 of 47 (26%), which was found to be similar to that of age-matched normal infants. GNR carriage in normal infants does not appear to be a residual of organisms acquired at birth, and interpretations of GNR carriage in ill or hospitalized infants should be evaluated by comparison with these data in healthy infants.