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 blaNDM-5 and blaOXA-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 (blaCTX-M-15, blaCMY-2, blaTEM-1B, blaOXA-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 often used as a drug of last resort against infections caused by multi-drug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacterales (CRE). Recently, the acquisition of mobile colistin resistance (mcr) genes by CRE has become a cause for concern. This study investigated the prevalence of mcr genes in CRE isolates in Seoul, Republic of Korea. In total, 3675 CRE strains were collected from patients between 2018 and 2019, and initially screened for mcr genes using multiplex polymerase chain reaction assays. Upon the identification of mcr-harbouring strains, colistin susceptibility tests, identification of carbapenemase and ß-lactamase genes, and plasmid replicon typing were performed. Clonal analysis was conducted using pulsed-field gel electrophoresis. mcr genes were detected in 2.2% (80/3675) of CRE strains. There were three mcr-1 carriers, one mcr-4.3 carrier, one mcr-4.3/mcr-9 carrier, 58 mcr-9 carriers, one mcr-9/mcr-10 carrier and 16 mcr-10 carriers among various Enterobacterales species, of which 60 were Enterobacter cloacae complex (ECC) strains. The prevalence of mcr genes in ECC strains was 20.5%. Molecular detection confirmed that 21.3% and 13.8% of mcr-harbouring strains shared blaNDM-1 or blaKPC-2, respectively. In addition, an IncHI2 replicon was identified in 71.7% of mcr-9 strains. Comparative analysis revealed not only a notable diversity of mcr carriers, but also clonal spreading or nosocomial outbreaks of some ECC strains. These findings revealed a silent distribution of mcr genes in CRE strains with high genetic heterogeneity in Seoul, underscoring the urgent need for timely intervention to control and prevent mcr dissemination.

Identification of an extensively drug-resistant Escherichia coli clinical strain harboring mcr-1 and blaNDM-1 in Korea.

The development of colistin resistance in carbapenem-resistant strains poses a serious public health problem. In this study, we collected 249 carbapenem-resistant Escherichia coli isolates from patients in Seoul in 2018, and screened all isolates for colistin resistance and for the presence of mobile colistin resistance (mcr) genes. Colistin-resistant strains were further analyzed using multilocus sequence typing, antimicrobial susceptibility testing, detection of antibiotic resistance determinants, plasmid transconjugation, and whole-genome sequencing. Three of the 249 carbapenem-resistant isolates were resistant to colistin, and mcr-1 was detected in one isolate (SECR18-0888), which belonged to sequence type 156 and was resistant to all antibiotics tested except tigecycline. The mcr-1.1 gene was located on an ~62 kb self-transferable IncI2 plasmid along with the blaCTX-M-55 gene, and the blaNDM-1, blaTEM, qepA1, and rmtB genes were additionally detected in SECR18-0888. As an extensively drug-resistant E. coli strain producing MCR-1 and NDM-1 was identified in Korea for the first time, continued monitoring of colistin resistance in carbapenem-resistant Enterobacteriaceae should be reinforced.

Emergence of a multidrug-resistant clinical isolate of Escherichia coli ST8499 strain producing NDM-13 carbapenemase in the Republic of Korea.

We described a carbapenem-resistant Escherichia coli ST8499 strain producing New Delhi metallo-ß-lactamase-13 (NDM-13) from patient in Korea. The isolate exhibited multidrug resistance, but remained susceptible to colistin and tigecycline. The blaNDM-13 gene was located on a 130-kb self-transmissible plasmid. This is the first report of NDM-13 carbapenemase in Korea.

Multivariate analysis to discriminate the origin of sesame seeds by multi-element analysis inductively coupled plasma-mass spectrometry.

In this study, inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine the concentration of 15 elements (Mg, Al, K, Ca, Cr, Mn, Co, Ni, Cu, Zn, Rb, Sr, Cd, Ba, and Pb) of sesame seeds. Multivariate analysis was then performed to discriminate the origin of sesame seeds. Korean (48), Chinese (44), and Indian (21) samples were used to develop the calibration model. Another 10 samples were used to validate this model. All elements were significantly different (p<0.05) among the samples from three countries, and all elements were subjected to both principal component analysis (PCA) and discriminant analysis. The concentrations of multi-element showed a trend of clustering according to the origin of samples based on PCA. They showed a discrimination rate of 92.0% in the discriminant analysis. The results demonstrated that a combination of ICP-MS multi-element determination and multivariate analysis could be used to discriminate the sesame seed origin.

A nondestructive approach for discrimination of the origin of sesame seeds using ED-XRF and NIR spectrometry with chemometrics.

An energy dispersive X-ray fluorescence (ED-XRF) spectrometer and a near infrared (NIR) spectrometer combined with chemometrics were applied for origin discrimination of 48 Korean, 44 Chinese, and 21 Indian sesame seed samples used for development of a discriminant calibration model. Multi-elemental ED-XRF analysis based on Mg, Al, Si, P, S, Cl, K, Ca, Mn, Fe, and Cu was used for comparisons among origins. All elements, except for Fe, showed differences and 96.5% of seed samples were assigned to the correct origin using discriminant analysis based on chemical analytical results. NIR measurements were performed for spectral scanning. Classification of seeds using NIR discriminant analysis achieved 89.4% of seed samples assigned to the correct origin. Both ED-XRF and NIR are useful as nondestructive tools for discrimination of sesame seed origins.

Monitoring and risk assessment of pesticide residues in commercially dried vegetables.

We tested for residual pesticide levels in dried vegetables in Seoul, Korea. A total of 100 samples of 13 different types of agricultural products were analyzed by a gas chromatography-nitrogen phosphate detector (GC-NPD), an electron capture detector (GC-µECD), a mass spectrometry detector (GC-MSD), and a high performance liquid chromatography-ultraviolet detector (HPLC-UV). We used multi-analysis methods to analyze for 253 different pesticide types. Among the selected agricultural products, residual pesticides were detected in 11 samples, of which 2 samples (2.0%) exceeded the Korea Maximum Residue limits (MRLs). We detected pesticide residue in 6 of 9 analyzed dried pepper leaves and 1 sample exceeded the Korea MRLs. Data obtained were then used for estimating the potential health risks associated with the exposures to these pesticides. The estimated daily intakes (EDIs) range from 0.1% of the acceptable daily intake (ADI) for bifenthrin to 8.4% of the ADI for cadusafos. The most critical commodity is cadusafos in chwinamul, contributing 8.4% to the hazard index (HI). This results show that the detected pesticides could not be considered a serious public health problem. Nevertheless, an investigation into continuous monitoring is recommended.