Respiratory carriage of the novel Kingella negevensis species by young children

Kingella negevensis, a novel Kingella species implicated in a pediatric joint infection, has been recently characterized but its epidemiology remains largely unknown. The pharyngeal carriage of K. negevensis was studied by re-examining the results of a previous longitudinal study conducted in a cohort of healthy Israeli children from whom upper respiratory tract specimens were sequentially cultured between the ages of 2 and 36 months. Isolates were identified as K. negevensis by a species-specific nucleic amplification assay and genotyped by pulsed-field gel electrophoresis. β-lactamase production was determined by the nitrocephin test. Kingella negevensis was detected in 26 of 4,472 (0.58%) oropharyngeal cultures obtained from 24 of 716 children (3.35%) and was not isolated from any of 4,472 nasopharyngeal specimens. Following the first 6 months of life during which none of the children was colonized, the prevalence of carriage gradually increased reaching a peak of 1.09% at 24 months of age and decreased thereafter. Kingella negevensis strains showed genomic heterogeneity, and two clones represented 22 of 26 (84.62%) isolates. Twelve of the 26 (46.15%) isolates, belonging to two distinct clones, produced β-lactamase. Kingella negevensis shows remarkable similarities with K. kingae in terms of colonization site, age-related patterns of acquisition and carriage, and clonal distribution of β-lactamase production. Additional research is needed to investigate potential colonization sites of K. negevensis outside the respiratory tract, explore the mechanisms of pharyngeal colonization by the organism, and determine its role as an invasive human pathogen.