Antimicrobial Resistance in the Upper Respiratory Tract of Children Compared with Adults
Authors: Chu Victoria T , Kalantar Katrina , Mick Eran , Tsitsiklis Alexandra , Spottiswoode Natasha , DeRisi Joseph L , Ambroggio Lilliam , Mourani Peter M , Langelier Charles R 
Published: November 2023

Abstract

Background
Antimicrobial resistance (AMR) is a growing global public health threat. In 2019, resistant bacterial infections and respiratory tract infections were a leading cause of death in children worldwide. While the gut is a known reservoir of AMR genes, there is little data on the AMR burden in the respiratory tract. We used metagenomic RNA next-generation sequencing (mNGS) to describe bacterial AMR genes detected in the upper respiratory tract of children and compare with adults.

Methods
We leveraged two established cohort studies of children and adults diagnosed with acute respiratory illnesses in the inpatient and outpatient setting in California and Colorado. Nasopharyngeal (NP) swabs were collected between March to September 2020. Specimens underwent RNA extraction and paired-end Illumina sequencing. AMR genes were detected using the ARG-ANNOT database and the CZID pipeline. Children ≤18 years of age and adults≥ 40 years of age were eligible for inclusion in the analysis. We described and compared AMR genes and AMR gene classes detected in children and adults. P-values were calculated using the Wilcoxon rank-sum test. A multiple logistic regression model was fitted to evaluate the association of age cohort (children vs adults) with presence of AMR genes, while accounting for possible confounding from sex and encounter setting. 95% confidence intervals (CI) were calculated using the Wald CI.

Results
NP swab mNGS data from 236 patients (82 children, 154 adults) were analyzed. Children were a median age of 4 years (range: 0-17 years), and adults were a median age of 62 years (range: 40-89 years). Both cohorts were 50% male. AMR genes were detected in 44 (54%) children and 109 (71%) adults. Genes conferring resistance to beta-lactams (n=112, 47%), macrolides (n=89, 38%), and tetracyclines (n=72, 31%) were the most frequently detected. Among children, children ages 0 to 2 years had a higher number of AMR genes than children of other age groups, particularly when compared with children ages 3 to 10 years (p-value: 0.031) (Figure 1A). When comparing children with adults, children had fewer AMR genes (p-value: 0.014) as well as fewer AMR gene classes (p-value: 0.031) (Figure 1B). In the multiple logistic regression model, children still had lower odds of any AMR genes detected compared with adults (odds ratio: 0.39, 95% CI: 0.21-0.71).
Figure 1. Box plots of (A) the number of antimicrobial resistance (AMR) genes detected in children stratified by age, and (B) the number of AMR genes and AMR gene classes detected in children (n=82) and adults (n=154). The size of the individual data points within the box plots correlates with the number of patients at each data point.

Conclusion
Children had fewer AMR genes and gene classes than adults in their upper respiratory tract microbiome. Despite this, over half of the children had detectable resistance genes, and children 2 years and younger had more AMR genes than other children. Almost half of the children had resistance genes to beta-lactams, the most frequently prescribed antibiotics to children. These findings suggest that presence of AMR organisms in the airway is common even in children, and that continued efforts to reduce AMR burden in this population are essential.