Characterization of TEM-1 β-Lactamase-Producing Kingella kingae Clinical Isolates.

is a human pathogen that causes pediatric osteoarticular infections and infective endocarditis in children and adults. The bacterium is usually susceptible to β-lactam antibiotics, although β-lactam resistance has been reported in rare isolates. This study was conducted to identify β-lactam-resistant strains and to characterize the resistance mechanism. Screening of a set of 90 clinical isolates obtained from different geographic locations revealed high-level resistance to penicillins among 25% of the strains isolated from Minnesota and Iceland. These strains produced TEM-1 β-lactamase and were shown to contain additional ≥50-kb plasmids. Ion Torrent sequencing of extrachromosomal DNA from a β-lactamase-producing strain confirmed the plasmid location of the gene. An identical plasmid pattern was demonstrated by multiplex PCR in all β-lactamase producers. The porin gene's fragments were analyzed to investigate the relatedness of bacterial strains. Phylogenetic analysis revealed 27 single-nucleotide polymorphisms (SNPs) in the gene fragment, resulting in two major clusters with 11 allele types forming bacterial-strain subclusters. β-Lactamase producers were grouped together based on genotyping. Our results suggest that the β-lactamase-producing strains likely originate from a single plasmid-bearing isolate that traveled from Europe to the United States, or vice versa. This study highlights the prevalence of penicillin resistance among strains in some regions and emphasizes the importance of surveillance for antibiotic resistance of the pathogen.