In a prior study of a different cohort of 358 prospectively-enrolled children, we sought associations between physician-attended illness visits and bacterial colonization in the first 5 years of life.2 We showed that early age of first colonization with pneumococcus, Hflu, and Mcat was associated with respiratory infection proneness and asthma among the children.
Dr. Michael E. Pichichero
Multiple demographic and risk factors may contribute to early life and high-density colonization that in turn may increase risk of infections. High densities and early life pneumococcal colonization in low/middle-income countries might impact PCV responses by induction of immunity tolerance. While it is appealing to study new vaccines in low/middle-income populations with high infection incidence, there are reasons that infection incidence is higher compared with high-income countries like the United States, among them may be early life nasopharyngeal colonization and density of colonization.
Prevalent pneumococcal serotype appear to differ with age. The most common serotypes in the first 6 months of life for the children were 23B> 22F> 16F and 21=19F, but in children 7-24 months, serotypes 35B> 21>15B>23A=23B were most commonly observed. This difference might be due to the impact of antibiotics.3 Pneumococci expressing serotypes 22F and 16F were oxacillin susceptible and antibiotic exposure in the first 6 months of life is very uncommon in our study cohorts. In contrast, all pneumococci expressing 35B capsule were oxacillin resistant and in our cohorts antibiotic exposures are common among 7- to 24-month-olds.
In conclusion, we determined that children in the first 6 months of life seen in pediatric primary care settings in Rochester, N.Y., have very low prevalence and low-density colonization of pneumococcus, Hflu, and Mcat compared with 7- to 24-month olds. Our results may explain the significantly lower rates of infections caused by pneumococci, Hflu, and Mcat in infants younger than 6 months old compared with low/middle-income countries.
Dr. Pichichero is a specialist in pediatric infectious diseases, Center for Infectious Diseases and Immunology, and director of the Research Institute at Rochester (N.Y.) General Hospital. He has no conflicts of interest to disclose.
References
1. Kaur R and Pichichero M. Colonization, density, and antibiotic resistance of Streptococcus pneumoniae, Haemophilus Influenzae, and Moraxella catarrhalis among PCV13 vaccinated infants in the first six months of life in Rochester, New York. J Pediatric Infect Dis Soc. 2023 Apr 18;12(3):135-42.
2. Chapman T et al. Nasopharyngeal colonization with pathobionts is associated with susceptibility to respiratory illnesses in young children. PLoS One. 2020 Dec 11;15(12):e0243942. doi: 10.1371/journal.pone.0243942.
3. Chapman TJ et al. Antibiotic use and vaccine antibody levels. Pediatrics 2022 May 1;149(5):e2021052061. doi: 10.1542/peds.2021-052061.