A single-center retrospective study of the molecular epidemiological characteristics of different infections in northern China.

BACKGROUND

( ) is an opportunistic pathogen that can cause multiple life-threatening infections. Recently, there has been an upward trend in carbapenem-resistant infections in China. This epidemiological trend needs to be examined to enable better disease control. We sought to analyze the genomic characteristics, including the prevalent sequence type (ST), resistance, virulence, and evolutionary relationship, of strains isolated from patients with different types of infections in northern China to provide theoretical support for the effective prevention and control of the evolution and transmission of .

METHODS

The STs were analyzed using multi-locus sequence typing (MLST). Drug susceptibility tests were used to examine the resistance of these STs to various antibiotics. A phylogenetic tree of these isolates was constructed using the National Center for Biotechnology Information genome as the reference. Antibiotic resistance genes were identified by comparing the genomic sequences against those in the Comprehensive Antibiotic Resistance Database. Virulence genes were identified using the Virulence Factor database, while the pathogenicity of the isolates was predicted using PathogenFinder.

RESULTS

In total, 38 clinical isolates of were identified and sequenced by high-throughput sequencing. Multidrug-resistant ST11 and hypervirulent ST23 were found to be the prevalent strains. The distribution of the ST11 strains was strongly correlated with stays in the neurosurgery department (chi square test, P=0.02), while the ST23 strains were more frequently isolated from patients with liver abscesses and gallbladder infections. The ST23 strains were significantly more pathogenic than the other STs (Wilcox test, P<0.001). The resistance analysis showed that the genes were significantly correlated with amikacin resistance (P<2.2e-16, R=1). The ST11 strains were also found to co-harbor the KPC-2, , and TEM-1 genes. To the best of our knowledge, this is the first study to report on the dissemination of such multidrug-resistant ST11 strains in Tianjin.

CONCLUSIONS

The carbapenem-resistant (CRKP) ST11 may become highly virulent (CR-hvKP) due to the acquisition of virulence plasmids. Attention should be paid to the evolutionary pressure of a caused by the overuse of antibiotics, which may trigger the further development of multidrug-resistant infections.