Outbreak of carbapenem-resistant Enterobacterales at a long-term care facility in Seoul, Korea: surveillance and intervention mitigation strategies

OBJECTIVES

Because effective decolonization options are not available, and treatment options are limited, carbapenem-resistant Enterobacterales (CRE) constitute increasingly threatening nosocomial pathogens. To prevent CRE-associated transmission and ensure patient safety, healthcare personnel and everyone in contact with CRE-infected patients must implement stringent infection control practices. This report describes a CRE outbreak, possibly related to a caregiver at a long-term care facility (LTCF), and presents a new surveillance model to improve the infection control of CRE in Seoul, Korea.

METHODS

The Seoul Metropolitan Government surveillance system identified an outbreak of CRE in an LTCF in 2022. We obtained data on the demographic characteristics and contact histories of the inpatients, medical staff, and caregivers. To isolate the inpatients and employees exposed to CRE, we used rectal swab samples and environmental sampling during the study period (May-December 2022).

RESULTS

We identified 18 cluster cases (1 caregiver and 17 inpatients) and 12 sporadic cases with CRE, and conducted a complete 197-day follow-up of all cases in the LTCF's isolation wards.

CONCLUSIONS

This investigation demonstrated that our surveillance model and targeted intervention, based on the cooperation of the municipal government, public health center, and infection control advisory committee, effectively contained the epidemic at the LTCF. Measures to improve the compliance of all employees in LTCFs with infection control guidelines should also be adopted.

Dissemination of an international high-risk clone of Escherichia coli ST410 co-producing NDM-5 and OXA-181 carbapenemases in Seoul, Republic of Korea

The rapid increase in carbapenemase-producing Enterobacterales is a global health concern. During 2017-2020, a total of 44 Escherichia coli isolates co-harbouring bla_NDM-5 and bla_OXA-181 were collected from patients at 17 hospitals in Seoul and characterized based on antimicrobial susceptibility, resistance genes and plasmid replicons detected using polymerase chain reaction (PCR). Clonal relatedness was estimated using pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). All isolates had an identical multidrug resistance profile, including resistance to carbapenems, cephalosporins, ciprofloxacin, tetracycline, and trimethoprim/sulfamethoxazole, and susceptibility to amikacin, colistin, and tigecycline. Resistance genes (bla_CTX-M-15, bla_CMY-2, bla_TEM-1B, bla_OXA-1, aac(6')-Ib-cr, and qnrS) and plasmid replicons (IncFIA, IncFIB, and IncX3) was observed in almost all isolates. All isolates belonged to ST410 and were genetically similar (>88% similarity), with some PFGE types shared among isolates from different hospitals. Analysis of the whole genome revealed that the isolates clustered together with other strains of the international high-risk clone ST410 B4/H24RxC from other countries. These findings underline the ongoing spread of the high-risk clone of NDM-5- and OXA-181-producing E. coli ST410 B4/H24RxC among hospitals in Seoul. Continuous monitoring and implementation of infection control measures are crucial to track and prevent further spread of these resistant strains.

Distribution of mcr genes among carbapenem-resistant Enterobacterales clinical isolates: High prevalence of mcr-positive Enterobacter cloacae complex in Seoul, Republic of Korea

Colistin is usually used as a drug of last resort against infections caused by multidrug-resistant gram-negative bacteria, including carbapenem-resistant Enterobacterales (CRE). Recently, the acquisition of mobile colistin resistance (mcr) genes by CRE is a cause for worry. Here, we investigated the prevalence of mcr genes in CRE isolates in Seoul, Korea. A total of 3,675 CRE strains were collected from patients between 2018 and 2019 and initially screened for mcr genes using multiplex-PCR assays. Upon the identification of mcr-harboring strains, colistin susceptibility tests, identification of carbapenemase and β-lactamase genes, and plasmid replicon typing were performed. Clonal analysis was conducted using pulsed-field gel electrophoresis. mcr genes were detected in 2.2% (80/3,675) CRE strains. There were three mcr-1, one mcr-4.3, one mcr-4.3/mcr-9, 58 mcr-9, one mcr-9/mcr-10, and 16 mcr-10 carriers from various Enterobacterales species, of which 60 were in Enterobacter cloacae complex (ECC) strains. The mcr prevalence in ECC was 20.5%. Molecular detection confirmed that 21.3% and 13.8% of the mcr-harboring strains shared bla_NDM-1 or bla_KPC-2, respectively. In addition, an IncHI2 replicon was identified in 71.7% of the mcr-9 strains. Comparative analysis revealed not only a notable diversity of mcr carriers, but also clonal spreading or nosocomial outbreak of some ECC strains. Our findings revealed a silent distribution of mcr in CRE strains with high genetic heterogeneity in Seoul, underscoring the urgent need for timely intervention to control and prevent mcr dissemination.

Hepatitis A virus strains identified in jogaejeot associated with outbreaks in Seoul, South Korea

Jogaejeot, seasoned Venerupis philippinarum, is a traditional Korean fermented food, and hepatitis A virus (HAV) can be transmitted through contaminated food, especially bivalve shellfish, causing acute gastroenteritis worldwide. Here, we carried out a phylogenetic analysis to identify and characterize HAV strains in jogaejeot samples associated with hepatitis A (HA) outbreaks in Seoul, South Korea, in 2019. The HAV strains were identified using blast and molecular analysis of the amplified HAV VP1-P2B genome region. The HAV strains identified in the five jogaejeot samples shared at least 99% sequence identity, were all classified as genotype IA and were most closely related to strains that are widespread in East Asia. These results support a link between the consumption of jogaejeot and the HA outbreaks observed in 2019 in Seoul. In addition, they indicate a need for more stringent enforcement of food safety regulations for the shellfish industry, especially against HAV, and the value of widespread vaccination.