A Polyclonal Spread Emerged: Characteristics of Carbapenem-Resistant Isolates from the Intensive Care Unit in a Chinese Tertiary Hospital.

Carbapenem-resistant (CRKP) isolates often cause nosocomial infections with limited therapeutic options and spread rapidly worldwide. In this study, we revealed a polyclonal emergence of CRKP isolates from the intensive care unit in a Chinese tertiary hospital. We applied a series of methods including automated screening, antimicrobial susceptibility testing, the modified carbapenem inacti vation method (mCIM), PCR amplification, DNA sequencing, and multilocus sequence typing (MLST) to characterize 30 non-duplicated CRKP isolates along with the collection of the related medical records. The results showed the polyclonal spread of CRKP isolates belonged to ST722, ST1446, ST111, ST896, ST290, and ST11. Among them, ST722 and ST1446 were two novel types of , and ST896 isolate harboring was also found for the first time. Since the polyclonal spread of CRKP in the same ward is rare, the silent clonal evolution with the switching genotypes prompts us to stay alert for outbreaks caused by novel subclones.