Genomic analysis of <i>Klebsiella pneumoniae</i> strains virulence and antibiotic resistance

Abstract

Recently, Klebsiella pneumoniae strains have become widespread both in community-acquired infectious processes and in nosocomial infections. There are two pathotypes of K. pneumoniae: classical (cKp) and hypervirulent (hvKp). Representatives of any pathotype are prone to acquire and further transmit genetic factors of antibiotic resistance and virulence. This combination accounts for severity of the infectious process. Therefore, information about whether the strain belongs to either pathotype can help in prescribing proper therapy. Since there is no consensus upon hypervirulence marker, we attempted to find the most significant combinations of genetic markers of virulence and antibiotic resistance in K. pneumoniae strains. The study was aimed to conduct a genomic analysis of virulence and antibiotic resistance of K. pneumoniae clinical isolates. Materials and methods. There were examined 85 strains of K. pneumoniae isolated from diverse clinical material samples from patients in large St. Petersburg hospitals. In our work, we used classical bacteriological methods, including determination of the hypermucoviscous type using the “string test”, the mass spectrometric method (MALDI-ToF MS) for identifying bacteria, molecular methods for studying markers of virulence and antibiotic resistance (multilocus sequence typing, genome sequencing of K. pneumoniae strains). Results. Among the studied K. pneumoniae strains, the most common carbapenemase genes were OXA-48 (18.7%) and NDM-1 genes — 17.3% of strains; in 6.7% of strains, NDM-1 and OXA-48 genes were found simultaneously. The percentage of strains with β-lactamase genes CTX-M-15 was 54.7%, OXA-1 — 17.3%, TEM-1D — 13.3%, and in 17.3% of cases the OXA-1 and TEM-1D genes were simultaneously present in bacterial strains. Quinolone resistance genes were found in 68.4% of strains. The most common genes were qnrS1 (40% of strains) and qnrB1 (22.7%). Phenotypic antimicrobial susceptibility testing showed that 23.5% and 64.7% strains were resistant to colistin and carbapenems, respectively. 32.9% K. pneumoniae strains, isolated in patients with phlegmon, pneumonia, sepsis, and peritonitis, had a hypermucoid phenotype. The most common sequence types were: ST395 (24.3%), ST23 (17.6%) and ST512 (9.5%). 8% and 25.3% of strains belonged to capsule types K1 and K2, respectively. The polyketide synthesis locus ybt, which characterizes virulent strains, was detected in 69.3% isolates, and the clb locus was present in 10.7% of strains. In 73.3% and 14.7% strains, the plasmid-associated virulence loci iuc and iro were identified, which encode the biosynthesis of the siderophores aerobactin and salmochelin. We described 44 cases (58.7% of strains) of genotypic convergence of virulence and antibiotic resistance, as shown by simultaneously detected the aerobactin (iuc) locus and β-lactamase or carbapenemase genes. Thus, identification of hypervirulence may provide valuable information for the clinical management of patients with hvKp infections. Therefore, it is is obviously necessary to develop comprehensive diagnostic test for simultaneous screening of multidrug-resistant hypervirulent K. pneumoniae strains.