Effect of Temperature on Carbapenemase-Encoding Plasmid Transfer in Klebsiella pneumoniae.

Bacteria causing human infections can develop antibiotic resistance due to various factors. Temperature affects bacterial growth and gene transfer; however, studies exploring the association between the changes in local temperature and antibiotic resistance are limited. Here, we investigated the effects of local temperatures on the distribution of antibiotic resistance and transmission of carbapenemase-producing Enterobacterales using the data on Klebsiella pneumoniae from sentinel hospitals in eight regions included in the Korea Global Antimicrobial Resistance Surveillance System between 2017 and 2021. The resistance rates to most antibiotics, including carbapenems, varied significantly according to local temperature (p < 0.047), except for aminoglycosides. Conjugation experiments at various temperatures for strains encoding the carbapenemase gene on a plasmid revealed significant variation in the optimal conjugation temperatures for plasmids carrying blaKPC and blaNDM genes. The optimal conjugation temperatures demonstrating the highest stability for blaKPC- and blaNDM-carrying plasmids were 25 °C (p = 0.030) and 30 °C (p = 0.007), respectively. The stability of blaKPC-IncF was higher at 25 °C than that at 30 °C (p = 0.032) or 37 °C (p = 0.047), while blaKPC-IncX3 exhibited the lowest stability at 37 °C (p = 0.047). blaNDM-IncX3 was more stable at 30 °C than at 37 °C (p = 0.049). These findings suggest that the optimal temperature for carbapenemase gene transmission varied between 25 °C and 30 °C, indicating that warmer seasons promote the transfer of more antibiotic resistance-related genes and highlighting the importance of local temperature in the spread and transmission of plasmids carrying carbapenemases.

Antimicrobial resistance of major clinical pathogens in South Korea, May 2016 to April 2017: first one-year report from Kor-GLASS.

The Korean government established an antimicrobial resistance (AMR) surveillance system, compatible with the Global AMR Surveillance System (GLASS): Kor-GLASS. We describe results from the first year of operation of the Kor-GLASS from May 2016 to April 2017, comprising all non-duplicated clinical isolates of major pathogens from blood, urine, faeces and urethral and cervical swabs from six sentinel hospitals. Antimicrobial susceptibility tests were carried out by disk diffusion, Etest, broth microdilution and agar dilution methods. Among 67,803 blood cultures, 3,523 target pathogens were recovered. The predominant bacterial species were Escherichia coli (n = 1,536), Klebsiella pneumoniae (n = 597) and Staphylococcus aureus (n = 584). From 57,477 urine cultures, 6,394 E. coli and 1,097 K. pneumoniae were recovered. Bloodstream infections in inpatients per 10,000 patient-days (10TPD) were highest for cefotaxime-resistant E. coli with 2.1, followed by 1.6 for meticillin-resistant Sta. aureus, 1.1 for imipenem-resistant Acinetobacter baumannii, 0.8 for cefotaxime-resistant K. pneumoniae and 0.4 for vancomycin-resistant Enterococcus faecium. Urinary tract infections in inpatients were 7.7 and 2.1 per 10TPD for cefotaxime-resistant E. coli and K. pneumoniae, respectively. Kor-GLASS generated well-curated surveillance data devoid of collection bias or isolate duplication. A bacterial bank and a database for the collections are under development.

Detection of mcr-1 Plasmids in Enterobacteriaceae Isolates From Human Specimens: Comparison With Those in Escherichia coli Isolates From Livestock in Korea.

BACKGROUND: The emerging mobile colistin resistance gene, mcr-1, is an ongoing worldwide concern and an evaluation of clinical isolates harboring this gene is required in Korea. We investigated mcr-1-possessing Enterobacteriaceae among Enterobacteriaceae strains isolated in Korea, and compared the genetic details of the plasmids with those in Escherichia coli isolates from livestock. METHODS: Among 9,396 Enterobacteriaceae clinical isolates collected between 2010 and 2015, 1,347 (14.3%) strains were resistant to colistin and those were screened for mcr-1 by PCR. Colistin minimum inhibitory concentrations (MICs) were determined by microdilution, and conjugal transfer of the mcr-1-harboring plasmids was assessed by direct mating. Whole genomes of three mcr-1-positive Enterobacteriaceae clinical isolates and 11 livestock-origin mcr-1-positive E. coli isolates were sequenced. RESULTS: Two E. coli and one Enterobacter aerogenes clinical isolates carried carried IncI2 plasmids harboring mcr-1, which conferred colistin resistance (E. coli MIC, 4 mg/L; E. aerogenes MIC, 32 mg/L). The strains possessed the complete conjugal machinery except for E. aerogenes harboring a truncated prepilin peptidase. The E. coli plasmid transferred more efficiently to E. coli than to Klebsiella pneumoniae or Enterobacter cloacae recipients. Among the three bacterial hosts, the colistin MIC was the highest for E. coli owing to the higher mcr-1-plasmid copy number and mcr-1 expression levels. Ten mcr-1-positive chicken-origin E. coli strains also possessed mcr-1-harboring IncI2 plasmids closely related to that in the clinical E. aerogenes isolate, and the remaining one porcine-origin E. coli possessed an mcr-1-harboring IncX4 plasmid. CONCLUSIONS: mcr-1-harboring IncI2 plasmids were identified in clinical Enterobacteriaceae isolates. These plasmids were closely associated with those in chicken-origin E. coli strains in Korea, supporting the concept of mcr-1 dissemination between humans and livestock.

New Delhi Metallo-Beta-Lactamase-Producing Enterobacteriaceae in South Korea Between 2010 and 2015.

This study was carried out to investigate the epidemiological time-course of New Delhi metallo-beta-lactamase- (NDM-) mediated carbapenem resistance in Enterobacteriaceae in South Korea. A total of 146 non-duplicate NDM-producing Enterobacteriaceae recovered between 2010 and 2015 were voluntarily collected from 33 general hospitals and confirmed by PCR. The species were identified by sequences of the 16S rDNA. Antimicrobial susceptibility was determined either by the disk diffusion method or by broth microdilution, and the carbapenem MICs were determined by agar dilution. Then, multilocus sequence typing and PCR-based replicon typing was carried out. Co-carried genes for drug resistance were identified by PCR and sequencing. The entire genomes of eight random selected NDM producers were sequenced. A total of 69 Klebsiella pneumoniae of 12 sequence types (STs), 34 Escherichia coli of 15 STs, 28 Enterobacter spp. (including one Enterobacter aerogenes), nine Citrobacter freundii, four Raoultella spp., and two Klebsiella oxytoca isolates produced either NDM-1 (n = 126), NDM-5 (n = 18), or NDM-7 (n = 2). The isolates co-produced CTX-M-type ESBL (52.1%), AmpCs (27.4%), additional carbapenemases (7.1%), and/or 16S rRNA methyltransferases (4.8%), resulting in multidrug-resistance (47.9%) or extensively drug-resistance (52.1%). Among plasmids harboring blaNDM, IncX3 was predominant (77.4%), followed by the IncFII type (5.8%). Genome analysis revealed inter-species and inter-strain horizontal gene transfer of the plasmid. Both clonal dissemination and plasmid transfer contributed to the wide dissemination of NDM producers in South Korea.

Klebsiella pneumoniae Carbapenemase Producers in South Korea between 2013 and 2015.

Between 2014 and 2015, the Klebsiella pneumoniae carbapenemase (KPC) was becoming endemic in South Korea. To assess this period of transition, we analyzed KPC producers in terms of molecular epidemiology. A total of 362 KPC-producing Enterobacteriaceae strains, including one from 2013, 13 from 2014, and 348 from 2015, were actively collected from 60 hospitals throughout the peninsula. Subtypes of KPC were determined by PCR and direct sequencing, and isotypes of Tn4401 (the transposon flanking the blaKPC gene) were specified by PCR using isotype-specific primers and direct sequencing. Sporadic occurrence of KPC-producing Enterobacteriaceae was initially observed around Seoul, which is the most crowded district of the country, and these strains rapidly disseminated in 2014, to the other parts of the country in 2015. The bacterial clones responsible for the extreme epidemiological transition were K. pneumoniae ST307 (46.2%) and ST11 (21.3%). Less frequently, E. coli (4.7%), Enterobacter spp. (1.4%), and other Enterobacteriaceae members (1.7%) producing the enzyme were identified. The blaKPC-2 gene bracketed by Tn4401a (72.1%) was the most prevalent mobile genetic element responsible for the dissemination, and the same gene carried either by Tn4401b (2.2%) or Tn4401c (6.6%) was identified at a lesser frequency. The genes blaKPC-3 (1.6%) and blaKPC-4 (6.4%), both flanked by Tn4401b, were occasionally identified. This study showed endemic dissemination of KPC producers in 2015 due to a clonal spread of two K. pneumoniae strains. Further systemic surveillance is needed to monitor dissemination of KPC-producers.

Carbapenemase-producing Enterobacteriaceae in South Korea: a report from the National Laboratory Surveillance System.

AIM: To assess the epidemiology of carbapenemase-producing Enterobacteriaceae (CPE) in South Korea. MATERIALS & METHODS: From 2011 to 2015, 2487 carbapenem-nonsusceptible Enterobacteriaceae were collected through the Korean National Laboratory Surveillance System. Disk-diffusion for antimicrobial susceptibility, PCR/sequencing to detect carbapenemase genes and multilocus sequence typing for molecular epidemiology were carried out. RESULTS: The number of carbapenem-nonsusceptible Enterobacteriaceae was increasing approximately 1.5-fold per year and the proportion of CPEs was exponentially confirmed from 2014. KPC was the most dominant, mostly associated with Klebsiella pneumoniae ST11 and ST307, NDM was the second and OXA-48-like was the third dominant carbapenemases. The IMP, VIM and GES-5 CPEs were identified sporadically. CONCLUSION: The nation-wide spreads of KPC, NDM and OXA-48-like CPEs were in an alarming epidemiological stage.

The blaOXA-23-associated transposons in the genome of Acinetobacter spp. represent an epidemiological situation of the species encountering carbapenems.

Objectives: High rates of carbapenem resistance in the human pathogen Acinetobacter baumannii threaten public health and need to be scrutinized. Methods: A total of 356 A. baumannii and 50 non-baumannii Acinetobacter spp. (NBA) strains collected in 2013 throughout South Korea were studied. The type of blaOXA-23 transposon was determined by PCR mapping and molecular epidemiology was assessed by MLST. Twelve representative strains and two comparative A. baumannii were entirely sequenced by single-molecule real-time sequencing. Results: The carbapenem resistance rate was 88% in A. baumannii, mainly due to blaOXA-23, with five exceptional cases associated with ISAba1-blaOXA-51-like. The blaOXA-23 gene in A. baumannii was carried either by Tn2006 (44%) or Tn2009 (54%), with a few exceptions carried by Tn2008 (1.6%). Of the NBA strains, 14% were resistant to carbapenems, two with blaOXA-58 and five with blaOXA-23 associated with Tn2006. The Tn2006-possessing strains belonged to various STs, whereas Tn2008- and Tn2009-possessing strains were limited to ST208 and ST191, respectively. The three transposons were often multiplied in the chromosome, and the gene copy number and the carbapenem MICs presented linear relationships either very strongly for Tn2008 or moderately for Tn2006 and Tn2009. Conclusions: The dissemination of Tn2006 was facilitated by its capability for intercellular transfer and that of Tn2009 was attributable to successful dissemination of the ST191 bacterial host carrying the transposon. Tn2008 was infrequent because of its insufficient ability to undergo intercellular transfer and the scarce bacterial host A. baumannii ST208. Gene amplification is an adaptive mechanism for bacteria that encounter antimicrobial drugs.

Complete Genome Sequence of Klebsiella pneumoniae subsp. pneumoniae KP617, Coproducing OXA-232 and NDM-1 Carbapenemases, Isolated in South Korea.

The prevalence of Klebsiella pneumoniae coproducing carbapenemase metallo-ß-lactamase 1 (NDM-1) and OXA-48 has been increasing globally since 2013. The complete genome of KP617 was sequenced and assembled into a circular chromosome and two plasmids. This sequence provides the genetic background for understanding the evolution of carbapenemase genes in K. pneumoniae KP617.

Detection of clonal KPC-2-producing Klebsiella pneumoniae ST258 in Korea during nationwide surveillance in 2011.

This study analysed the characteristics and genetic similarity of recent Klebsiella pneumoniae carbapenemase (KPC-2)-producing Klebsiella pneumoniae isolates from Korea. Recent laboratory surveillance detected an increase in carbapenemase-producing Enterobacteriaceae in Korea. A total of 6 KPC-2-producing K. pneumoniae were identified from 277 Enterobacteriaceae clinical isolates. All were sequence type (ST) 258 and they had the same pulsotype. They had high MICs for carbapenems and multi-drug resistance. TEM-1, SHV-11 and OXA type ß-lactamases were detected in all isolates, whereas CTX-M type ß-lactamases and plasmid-mediated AmpC ß-lactamase (PABL) were not present. A conjugation experiment failed, but blaKPC-2-harbouring plasmids from the six isolates were used to transform Escherichia coli DH5-α by electroporation. Each of the transformants harboured a blaKPC-2-positive approximately 95 kb plasmid, which was typed in the IncFII incompatibility group and co-harboured TEM-1 and OXA-9 ß-lactamases. They shared the same restriction profile. This study confirms the emergence of clonal ST258 KPC-2-producing K. pneumoniae in some regions of Korea.

Dissemination of genetically related IMP-6-producing multidrug-resistant Pseudomonas aeruginosa ST235 in South Korea.

The present study aimed to describe the prevalence and molecular epidemiology of metallo-ß-lactamase (MBL)-producing Pseudomonas aeruginosa isolates obtained from non-tertiary care hospitals and geriatric hospitals in South Korea. Of the 644 isolates, 224 were carbapenem-resistant, amongst which 41 (18.3%) were MBL-producers and the major MBL type was IMP-6 (35 isolates). IMP-6-producing isolates were multidrug-resistant and showed higher minimum inhibitory concentrations for meropenem than imipenem. All of the IMP-6-producing isolates had class 1 integrons with amplification sizes of 4.5 kb/5.5 kb (34 isolates) or 3.0 kb (1 isolate); 4.5 kb/5.5 kb integrons had bla(IMP-6)-qac-aacA4-bla(OXA-1)-aadA1 (5.5 kb) and aadB-cmlA-bla(OXA-10)-aadA1 (4.5 kb). Pulsed-field gel electrophoresis (PFGE) analysis indicated that all IMP-6-producing P. aeruginosa from various geographic areas had nearly identical patterns with >85% similarity. All IMP-6-producing isolates showed high genetic similarity to those obtained from tertiary care hospitals and had the same integron type, indicating the spread of these strains to the three types of hospitals nationwide. These data show the wide spreading of clonally related IMP-6-producing P. aeruginosa (sequence type 235) through tertiary, non-tertiary and geriatric hospitals in South Korea. Continuous monitoring and thorough infection control should be performed in all types of hospitals to prevent further spreading of MBL-producing P. aeruginosa.