Purpose: To determine the epidemiology characteristics of intestinal colonization of carbapenem-resistant Enterobacteriaceae  (CRE) among inpatients in a pediatric hospital in China.
Methods: A retrospective study was conducted from April to December 2019. Medical records were reviewed to extract the clinical information. Antimicrobial susceptibility was performed by broth microdilution method. Drug resistance determinants and plasmid types were analyzed using polymerase chain reaction (PCR) assays. Multilocus sequence typing (MLST) and Enterobacterial repetitive intergenic consensus sequences PCR (ERIC-PCR) were employed to determine the genetic relationships between strains.
Results: A total of 90 CRE strains were isolated, with a fecal carriage rate of 8.6% (90/1052), and mainly distributed in E. aerogenes  (n=30), K. pneumoniae  (n=25) and E. coli  (n=23). More than 50% of CRE colonizers had a history of invasive procedures and antibiotic exposures. As high as 91.1% (82/90) of CRE isolates carried carbapenemase genes, with bla _NDM-5 (n=56) being the most common, and mainly found in E. aerogenes  (51.8%, 29/56) and E. coli  (32.1%, 18/56) isolates, which primarily belonged to ST4 (100%, 29/29) and ST692 (55.6%, 10/18), respectively. Followed by bla _KPC-2 (n=12), and all found in K. pneumoniae  ST11 isolates. Other carbapenemase genes including bla _NDM-1, bla _IMP-4 and bla _IMP-26. Meanwhile, ESBL genes (bla _CTX-M, bla _TEM-1 and bla _SHV) and AmpC genes (bla _DHA-1 and bla _EBC) were also detected. All CRE isolates showed high resistance to cephalosporins and carbapenemases (97.8%-100.0%) but remained susceptible to tigecycline (98.9%). IncX3 was a major plasmid type in NDM-containing strains (91.3%), and 91.7% of KPC-2-producing K. pneumoniae  harboring IncFII and IncFIB plasmids. The ERIC-PCR revealed that several strains with identical STs were genetically similar.
Conclusion: This study revealed a major intestinal colonization of ST4 NDM-5 E. aerogenes , ST11 KPC-2 K. pneumoniae  and ST692 NDM-5 E. coli  strains among inpatients in a pediatric hospital. Infection control measures should be implemented immediately to prevent the spread of these strains in clinical settings.
Keywords: intestinal colonization, hospitalized children, ST4, E. aerogenes , NICU, ERIC-PCR