Tigecycline Susceptibility of Klebsiella pneumoniae Complex and Escherichia coli Isolates from Companion Animals: The Prevalence of Tigecycline-Nonsusceptible K. pneumoniae Complex, Including Internationally Expanding Human Pathogenic Lineages.

Transmission of tigecycline-nonsusceptible pathogenic Enterobacteriaceae from companion animals to human should be a concern because tigecycline is a last-line drug for treating multidrug-resistant Enterobacteriaceae in human medicine. However, tigecycline susceptibility of Enterobacteriaceae isolated from companion animals has not been investigated. In this study, we investigated the tigecycline susceptibility of Klebsiella pneumoniae complex and Escherichia coli isolates from dogs and cats, and evaluated their human pathogenicity potential. Tigecycline susceptibility of K. pneumoniae, including Klebsiella quasipneumoniae (n = 86) and E. coli (n = 100) strains isolated from dogs and cats was investigated. The antimicrobial susceptibility, capsular serotype, multilocus sequence type, ompK36 group, presence of virulence genes, and serum resistance of tigecycline-nonsusceptible isolates were evaluated. All E. coli isolates were susceptible to tigecycline. Two K. pneumoniae (minimum inhibitory concentration [MIC], 4 mg/L) and one K. quasipneumoniae (MIC, 8 mg/L) isolates were tigecycline resistant. Sixteen K. pneumoniae and one K. quasipneumoniae isolates were tigecycline intermediate (2 mg/L). All tigecycline-nonsusceptible isolates (n = 20) were also ciprofloxacin nonsusceptible. These isolates harbored five to nine virulence genes; 16 isolates were resistant to the human serum. In addition, STs of 13 K. pneumoniae isolates were reported to be found in strains isolated from human; isolates considered high-risk clones in human (ST11, ST15, and ST147) were also identified. In conclusion, the isolation of tigecycline-nonsusceptible K. pneumoniae from companion animals is an impact from the viewpoint of One Health approach to antimicrobial resistance that companion animals are a reservoir of human pathogenic lineages.