Search

• Carbapenem-resistant A. baumannii (CRAB) is associated with high mortality rates. • Sequence types ST455 and ST787 CRAB belonging to CC455 are widespread in Taiwan. • Novel contact-dependent growth inhibition CDI TYTH1 was found in CC455. • CDI TYTH1 appears to be a functional epidemic genetic marker for CRAB. The aim of the study was to evaluate the distribution and function of contact-dependent growth inhibition (CDI) systems associated with carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. Isolates were examined by multilocus sequence typing (MLST) and polymerase chain reaction (PCR) for the presence of CDI genes in CRAB and carbapenem-susceptible A. baumannii (CSAB) from patients with invasive disease in a medical center in Taiwan. Inter-bacterial competition assays were performed to characterize the in vitro function of the CDI system. A total of 89 (61.0%) CSAB and 57 (39.0%) CRAB isolates were collected and examined. ST787 (20/57; 35.1%) was the predominant sequence type among CRAB, followed by ST455 (10/57; 17.5%). More than half the CRAB (56.1%, 32/57) belonged to CC455 and more than one third (38.6%, 22/57) to CC92. A novel CDI system, cdi TYTH1 , was found in 87.7% (50/57) of the CRAB but in only 1.1% (1/89) of the CSAB isolates (P <0.00001). The cdi TYTH1 was also identified in 94.4% (17/18) of previously genome-sequenced CRAB isolates and only one CSAB isolate from Taiwan. Two other previously reported CDI (cdi 19606-1 and cdi 19606-2) were not found in these isolates, except both were found in one CSAB. All six CRAB without cdi TYTH1 showed growth inhibition by a CSAB carrying cdi TYTH1 in vitro. All clinical CRAB isolates belonging to the predominant CC455 carried the newly identified cdi TYTH1. This CDI system was widespread in CRAB clinical isolates and appeared to be an epidemic genetic marker for CRAB in Taiwan. The cdi TYTH1 was functional in vitro in bacterial competition assay. [ABSTRACT FROM AUTHOR]