Characteristics and longitudinal kinetic analysis of carbapenem-resistant Escherichia coli detected in a northern Osaka Prefecture medical facility

Abstract

The spread of antibiotic-resistant bacteria has long been a serious global problem. At present, carbapenem antibiotics are used as drugs of last resort against antibiotic-resistant bacterial infections caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae. However, the emergence of carbapenem-resistant Enterobacteriaceae (CRE) renders this treatment ineffective. In Japan, a health-care-associated infection with CRE at a medical facility in Osaka City was recorded in 2014 and has been reported extensively as one of the earliest known incidents of CRE infection. In this study, 25 strains of carbapenem-resistant Escherichia coli detected in a medical facility in northern Osaka Prefecture during a 4-year period, beginning in 2012, were compared to the strains involved in the incident that occurred in Osaka City. Upon analyzing the genetic factors responsible for drug resistance, it was found that all strains contained the CTX-M-2 group of ESBL genes. In addition, 24 strains contained the IMP-6-type metallo-β-lactamase gene. This corresponds to the characteristics of the drug-resistant Enterobacteriaceae reported in the Osaka City incident, suggesting that by 2012, similar strains of Enterobacteriaceae had already been detected in northern Osaka. In addition, when PCR-based ORF typing was performed and the longitudinal dynamics analyzed, it was found that there was an annual increase in the number and diversity of detected strains. Besides, in 2016, a strain of carbapenem-resistant E. coli, which was very rarely reported in Japan, was also found to be resistant to amikacin. Consequently, it is necessary to closely monitor this strain from this point onward.