• Journal of Microbiology and Biotechnology
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• v.25 no.7
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• pp.1154-1162
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• 2015

The emergence of carbapenem resistance among Pseudomonas aeruginosa is an increasing problem in many parts of the world. In particular, metallo-$\beta$-lactamases (MBLs) and AmpC $\beta$lactamases are responsible for high-level resistance to carbapenem and cephalosporin. We studied the diversity and frequency of $\beta$-lactamases and characterized chromosomal AmpC $\beta$lactamase from carbapenem-resistant P. aeruginosa isolates. Sixty-one carbapenem-resistant P. aeruginosa isolates were collected from patients in a tertiary hospital in Daejeon, Korea, from January 2011 to June 2014. Minimum inhibitory concentrations (MICs) of four antimicrobial agents were determined using the agar-dilution method. Polymerase chain reaction and sequencing were used to identify the various $\beta$-lactamase genes, class 1 integrons, and chromosomally encoded and plasmid-mediated ampC genes. In addition, the epidemiological relationship was investigated by multilocus sequence typing. Among 61 carbapenem-resistant P. aeruginosa isolates, 25 isolates (41.0%) were MBL producers. Additionally, 30 isolates producing PDC (Pseudomonas-derived cephalosporinase)-2 were highly resistant to ceftazidime (MIC₅₀ = $256{\mu}g/ml$) and cefepime (MIC₅₀ = $256{\mu}g/ml$). Of all the PDC variants, 25 isolates harboring MBL genes showed high levels of cephalosporin and carbapenem resistance, whereas 36 isolates that did not harbor MBL genes revealed relatively low-level resistance (ceftazidime, p < 0.001; cefepime, p < 0.001; imipenem, p = 0.003; meropenem, p < 0.001). The coexistence of MBLs and AmpC $\beta$-lactamases suggests that these may be important contributing factors for cephalosporin and carbapenem resistance. Therefore, efficient detection and intervention to control drug resistance are necessary to prevent the emergence of P. aeruginosa possessing this combination of $\beta$-lactamases.

• Korean Journal of Microbiology
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• v.45 no.2
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• pp.163-169
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• 2009

This study was performed to investigate the type of extended-spectrum $\beta$-lactamases (ESBL) produced by bacteria isolated from the sewage of wastewater treatment plant at Minragdong, Suyong-gu in Busan. The facility is located at sushi restaurants and guides its drain water to the wastewater treatment plant at Yonghodong, Nam-gu in Busan. Samples were collected on January, 2009. A total of 19 strains were selected as potential ESBL positive strains through a double disk synergy test. On the basis of the results from biochemical tests including indole, methyl-red, Voges-Proskauer, Simmon's citrate, decarboxylase-dihydrolase and sugar-fermentation tests, the 19 strains were identified with 16 strains of Escherichia coli and 3 strains of Klebsiella pneumoniae. Out of 19 strains, 4 transconjugants against Escherichia coli J53, which is sodium azide resistant recipient strain, were obtained. The plasmids isolated from transconjugants were used for PCR analysis. The type of each extended-spectrum $\beta$-lactamase (ESBL) produced by the strains was determined on the basis of isoelectric focusing analysis and DNA sequencing. The results indicated that the types of ESBL from Klebsiella pneumoniae were SHV-12 (3 strains), and Escherichia coli was SHV-12/TEM-1 (1 strain), respectively.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.3
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• pp.210-216
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• 2016

Recently, there has been a considerable increase in the prevalence of CTX-M type extended-spectrum ${\beta}$-lactamase (ESBL)-producing E. coli isolates worldwide, including Korea. To investigate the ESBL genes in the E. coli strains isolated from a university hospital in the Chungcheong area, a study was conducted using PCR amplification and nucleotide sequence analysis of the amplified products to detect the plasmid mediated quinolone resistance (PMQR) genes in ESBL producing E. coli isolates. The number of CTX-M-14 producing isolates was 25 (16.0%) isolates, and of them, 9 (5.8%) isolates also produced CTX-M-15. All CTX-M type ESBL producing E. coli isolates showed resistance to cefotaxime. Twelve (48%) CTX-M type ESBL producing E. coli isolates contained the PMQR genes, 8 contained qnrS1, and 8 contained aac(6')-Ib-cr. Four isolates harbored both qnrS1 and aac(6')-Ib-cr genes. In our study, we confirmed that the plasmid mediated antimicrobial resistant determinants-the ESBL and PMQR genes-were distributed in the E. coli isolates. To prevent further spreading of the resistant genes among the E. coli isolates, consistent effort is required to investigate and monitor the resistant genes.

• Microbiology and Biotechnology Letters
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• v.52 no.3
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• pp.325-327
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• 2024

We report the complete genome sequence of an extended-spectrum beta-lactamase-producing Salmonella enterica subsp. enterica Serovar Infantis strain IJCS5-22 that harbors bla_CTX-M-65, which was isolated from whole chicken meat purchased from a retail market in South Korea. The assembled IJCS5-22 genome comprised a 4,727,133 bp circular chromosome and a 318,349 bp plasmid that encoded several antimicrobial resistance genes, including bla_CTX-M-65, with 52.27% and 50.39% GC contents, respectively.

• Journal of Veterinary Science
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• v.23 no.3
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• pp.37.1-37.8
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• 2022

Background: Avian pathogenic Escherichia coli (APEC) causes colibacillosis, resulting in significant economic losses in the poultry industry. Objectives: In this study, the molecular characteristics of two extended-spectrum beta-lactamase (ESBL)-producing APEC isolates were compared with previously reported ESBL-producing E. coli isolates. Methods: The molecular characteristics of E. coli isolates and the genetic environments of the ESBL genes were investigated using whole genome sequencing. Results: The two ESBL-producing APEC were classified into the phylogenetic groups C and B1 and ST410 and ST162, respectively. Moreover, the ESBL genes of the two isolates were harbored in different Inc plasmids. The EC1809182 strain, harboring the bla_CTX-M-55 gene on the plasmid, exhibited extensive homology to IncFIB (98.4%) and IncFIC(FII) (95.8%). The EC1809191 strain, harboring the bla_CTX-M-1 gene, was homologous to IncI1-I (Gamma) (99.3%). All chromosomes carried the multidrug transporter, mdf(A) gene. Mobile genetic elements, adjacent to CTX-M genes, facilitated the dissemination of genes in the two isolates, analogous to other ESBL-producing E. coli isolates. Conclusions: This study clarifies the transmission dynamics of CTX-M genes and supports strengthened surveillance to prevent the transmission of the antimicrobial-resistant genes to humans via the food chain.

• Korean Journal of Microbiology
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• v.32 no.1
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• pp.20-27
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• 1994

An inducible ${\beta}$-lactamase gene (bla) was identified and isolated from the chromosomal DNA of multiple drug resistant strains of Staphylococcus aureus. Determined base sequence of bla and of its flanking region was compared with those of bla genes identified on the staphylococcal plasmids pPC1, pI258, pI1071, and pUB101. Base sequence of 843 base-long structural gene of our bla was same as that of pPCl-, pI258-, and pS1-bla. However, HindIII recognition site Which is found in most of the bla genes at 140 base upstream from the structural gene was moved to the site of 370 base upstream from the structural gene. And one of the two direct repeat sequence found in downstream flanking region of pI1071-bla was deleted in our bla. Amino acid sequence homology analysis of the ORF located around HindIII recognition site reveals that this 80 amino acids-long polypeptide is C-terminus of transposase of Tn4001.

• Journal of Digital Convergence
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• v.13 no.12
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• pp.313-318
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• 2015

We investigated the prevalence of extended spectrum ${\beta}$-lactamase (ESBL) genes and 16S rRNA methyltransferase genes to study antimicrobial resistance mechanisms of Enterobacter cloacae strains isolated from a university hospital in the Chungcheong province of Korea. Eight of the bacteria strains involved in this study contained CTX-M-15 type ESBL. Among 8 strains harboring the ESBL gene, 3 strains also harbored armA gene. The three isolates showed resistance to antimicrobial agents belonged to third cephalosporin, aminoglycoside, and fluoroquinolones. Furthermore, interspecies plasmid transfer of the antimicrobial resistant genes may induced horizontal spreading of the genes and emergence of multidrug resistant bacteria. Therefore, surveillance for existence of antimicrobial resistance determinants is important to prevent distribution of antimicrobial resistant strains.

• Journal of Microbiology and Biotechnology
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• v.34 no.5
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• pp.1101-1108
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• 2024

Earlier studies have validated the isolation of extended-spectrum beta-lactamase-producing Salmonella (ESBL-Sal) strains from food. While poultry is recognized as a reservoir for Salmonella contamination, pertinent data regarding ESBL-Sal remains limited. Consequently, the Ministry of Food and Drug Safety has isolated Salmonella spp. from retail meat and evaluated their antibiotic susceptibility and genetic characteristics via whole-genome sequencing. To further elucidate these aspects, this study investigates the prevalence, antibiotic resistance profiles, genomic characteristics, and homology of ESBL-Sal spp. obtained from livestock-derived products in South Korean retail outlets. A total of 653 Salmonella spp. were isolated from 1,876 meat samples, including 509 beef, 503 pork, 555 chicken, and 309 duck samples. The prevalence rates of Salmonella were 0.0%, 1.4%, 17.5%, and 28.2% in the beef, pork, chicken, and duck samples, respectively. ESBL-Sal was exclusively identified in poultry meat, with a prevalence of 1.4% in the chicken samples (8/555) and 0.3% in the duck samples (1/309). All ESBL-Sal strains carried the bla_CTX-M-1 gene and exhibited resistance to ampicillin, ceftiofur, ceftazidime, nalidixic acid, and tetracycline. Eight ESBL-Sal isolates were identified as S. Enteritidis with sequence type (ST) 11. The major plasmid replicons of the Enteritidis-ST11 strains were IncFIB(S) and IncFII(S), carrying antimicrobial resistance genes (β-lactam, tetracycline, and aminoglycoside) and 166 virulence factor genes. The results of this study provide valuable insights for the surveillance and monitoring of ESBL-Sal in South Korean food chain.

• Journal of Microbiology and Biotechnology
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• v.2 no.1
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• pp.26-34
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• 1992

The effect of induction temperature on fermentation parameters has been investigated extensively using Escherichia coli M5248[pNKM21], a producer of recombinant human interleukin-2 (rhIL-2). In this recombinant microorganism, the gene expression of rhIL-2 is regulated by the cI857 repressor and $P_L$ promoter system. The recombinant fermentation parameters studied in this work include the cell growth, protein synthesis, cell viability, plasmid stability, $\beta$-lactamase activity, and rhIL-2 productivity. Interrelationships of such fermentation parameters have been analyzed through a quantitative assessment of the experimental data set obtained at eight different culture conditions. While the expression of rhIL-2 gene was repressed at culture temperatures below $34^\circ{C}$ with little effect on other fermentation parameters, under the conditions of rhIL-2 production $>(36~44^\circ{C})$ the cell growth, plasmid stability, and $\beta$-lactamase activity were, as induction temperature was increased, more profoundly reduced. Although the rhIL-2 content in the insoluble protein fraction was maximum at $40^\circ{C}$, total rhIL-2 production in the culture volume was found to be highest at the induction temperature of $36^\circ{C}$. This was in contrast to the previously known optimum induction temperature of the P$_{L}$ promoter system $>(40~42^\circ{C})$.Explanations for such a discrepancy have been proposed based on a product formation kinetics, and their implications have been discussed in detail.l.

• The Korean Journal of Zoology
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• v.27 no.2
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• pp.103-116
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• 1984

The structural gene of rabbit hemoglobin was cloned into Pst I site of pBR322 in E. coli. The complementary DNA (cDNA) was synthesized from rabbit globin mRNA with avian myeloblastosis viral reverse transcriptase, and then RNA was destroyed at pH 11. The double stranded cDNA was synthesized with both Klenow fragment of E. coli DNA polymerase I and reverse transcriptase and then the hairpin loop was opened with Sl nuclease. Double stranded cDNA was subsequently tailed with dCTP and annealed to dGMP-tailed vector DNA. After transformation and initial screening of appropriate clones by plasmid size, the cloned colonies were identified by in situ colony hybridization using by plasmid size, the cloned colonies were identified by in situ colony hybridization using $[^32P]$-labeled cDNA probes and characterized the inserts with restriction endonucleases. The expression of cloned globin gene was investigated by standard radioimmunoassay using rat anti-rabbit Hb serum as primary antibody and goat antirat IgG serum as secondary antibody. The result suggested that the chimeric proteins (the part of $\\beta$-lactamase from the vector pBR322 and globin from rabbit) were supposedly produced in E. coli and the product had the antigenic determinant of rabbit hemoglobin.