• Biomedical Science Letters
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• v.18 no.1
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• pp.79-82
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• 2012

Acinetobacter infections are of great concern in clinical settings because of multi-drug resistance (MDR) and high mortality of the infected patients. The MDR Acinetobacter baumannii has emerged as a significant infectious agent in hospitals worldwide. The purpose of this study was to determine for molecular characterization of MDR A. baumannii clinical isolates obtained from the Wonju Christian Hospital in Gangwon province of Korea. A total of seventy nonduplicate A. baumannii isolates were collected from the Wonju Christian Hospital in Korea from March to April in 2011. All of the MDR A. baumannii isolates were encoded by $bla_{OXA-23-like}$ gene and all isolates with the $bla_{OXA-23-like}$ gene had the upstream element ISAba1 to promote increased gene expression and subsequent resistance to carbapenem. 16S rRNA methylase gene (armA) was detected in 44 clinical isolates which were resistant to amikacin, and phosphotransferase genes encoding aac(3)-Ia and aac(6')-Ib were the most prevalent. A combination of 16S rRNA methylase and aminoglycoside-modifying enzyme genes (armA, aac(3)-Ia, aac(6')-Ib, and aph(3')-Ia) were found in 31 isolates. The sequencing results for the quinolone resistance-determining region (QRDR) of gyrA and parC revealed the presence of Ser (TCA) 83 Leu (TTA) and Ser (TCG) 80 Leu (TTG) substitutions in the respective enzymes for all MDR. Molecular typing for MDR A. baumannii could be helpful in confirming the identification of a common source or cross-contamination. This is an important step in enabling epidemiological tracing of these strains.

• Journal of Microbiology and Biotechnology
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• v.23 no.9
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• pp.1293-1303
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• 2013

Antibiotic resistance of soilborne Acinetobacter species has been poorly explored. In this study, norfloxacin resistance of a soil bacterium, Acinetobacter oleivorans DR1, was investigated. The frequencies of mutant appearance of all tested non-pathogenic Acinetobacter strains were lower than those of pathogenic strains under minimum inhibitory concentration (MIC). When the quinolone-resistance-determining region of the gyrA gene was examined, only one mutant (His78Asn) out of 10 resistant variants had a mutation. Whole transcriptome analysis using a RNA-Seq demonstrated that genes involved in SOS response and DNA repair were significantly up-regulated by norfloxacin. Determining the MICs of survival cells after norfloxacin treatment confirmed some of those cells were indeed persister cells. Ten colonies, randomly selected from among those that survived in the presence of norfloxacin, did not exhibit increased MIC. Thus, both the low mutation frequency of the target gene and SOS response under norfloxacin suggested that persister formation might contribute to the resistance of DR1 against norfloxacin. The persister frequency increased without a change in MIC when stationary phase cells, low growth rates conditions, and growth-deficient dnaJ mutant were used. Taken together, our comprehensive approach, which included mutational analysis of the target gene, persister formation assays, and RNA sequencing, indicated that DR1 survival when exposed to norfloxacin is related not only to target gene mutation but also to persister formation, possibly through up-regulation of the SOS response and DNA repair genes.

• Korean Journal of Veterinary Research
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• v.60 no.3
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• pp.173-177
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• 2020

Edible offal is easily contaminated by Escherichia coli (E. coli) and fluoroquinolone (FQ)-resistant E. coli is considered a serious public health problem, thus, this study investigated the genetic characteristics of FQ-resistant E. coli from edible offal. A total of 22 FQ-resistant E. coli isolates were tested. A double mutation in each gyrA and parC led the highest MIC. Four (18.2%) isolates carried plasmid-mediated quinolone resistance genes. The fimH, eaeA, escV, astA, and iucC genes were confirmed. Seventeen isolates (77.3%) were positive for plasmid replicons. The isolates showed high genetic heterogeneity based on pulsed-field gel electrophoresis patterns.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.74-81
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• 2016

Ureaplasma species can normally colonize in the bodies of healthy individuals. Their colonization is associated with various diseases including non-gonococcal urethritis, chorioamnionitis, neonatal meningitis, and prematurity. In 2012, the sum of the resistant and intermediate resistant rates of Ureaplasma spp. to ofloxacin and ciprofloxacin was 66.08% and 92.69%, respectively. DNA point mutations in the genes encoding DNA gyrase (topoisomerase II) and topoisomerase IV are commonly responsible for fluoroquinolone resistance. Each enzyme is composed of two subunits encoded by gyrA and gyrB genes for DNA gyrase and parC and parE genes for topoisomerase IV. In the current study, these genes were sequenced in order to determine the role of amino acid substitutions in Ureaplasma spp. clinical isolates. From December 2012 to May 2013, we examined mutation patterns of the quinolone resistance-determining region (QRDR) in Ureaplasma spp. DNA sequences in the QRDR region of Ureaplasma clinical isolates were compared with those of reference strains including U. urealyticum serovar 8 (ATCC 27618) and U. parvum serovar 3 (ATCC 27815). Mutations were detected in all ofloxacin- and ciprofloxacin-resistant isolates, however no mutations were detected in drug-susceptible isolates. Most of the mutations related to fluoroquinolone resistance occurred in the parC gene, causing amino acid substitutions. Newly found amino acid substitutions in this study were Asn481Ser in GyrB; Phe149Leu, Asp150Met, Asp151Ile, and Ser152Val in ParC; and Pro446Ser and Arg448Lys in ParE. Continuous monitoring and accumulation of mutation data in fluoroquinolone-resistant Ureaplasma clinical isolates are essential to determining the tendency and to understanding the mechanisms underlying antimicrobial resistance.

• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1735-1743
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• 2010

The full-length genes gyrB (2,415 bp), parC (2,277 bp), and parE (1,896 bp) in Edwardsiella tarda were cloned by PCR with degenerate primers based on the sequence of the respective quinolone resistance-determining region (QRDR), followed by elongation of 5' and 3' ends using cassette ligation-mediated PCR (CLMP). Analysis of the cloned genes revealed open reading frames (ORFs) encoding proteins of 804 (GyrB), 758 (ParC), and 631 (ParE) amino acids with conserved gyrase/topoisomerase features and motifs important for enzymatic function. The ORFs were preceded by putative promoters, ribosome binding sites, and inverted repeats with the potential to form cruciform structures for binding of DNA-binding proteins. When comparing the deduced amino acid sequences of E. tarda GyrB, ParC, and ParE with those of the corresponding proteins in other bacteria, they were found to be most closely related to Escherichia coli GyrB (87.6% identity), Klebsiella pneumoniae ParC (78.8% identity), and Salmonella Typhimurium ParE (89.5% identity), respectively. The two topoisomerase genes, parC and parE, were found to be contiguous on the E. tarda chromosome. All 18 quinolone-resistant isolates obtained from Korea thus far did not contain subunit alternations apart from a substitution in GyrA (Ser83$\rightarrow$Arg). However, an alteration in the QRDR of ParC (Ser84$\rightarrow$Ile) following an amino acid substitution in GyrA (Asp87$\rightarrow$Gly) was detected in E. tarda mutants selected in vitro at $8{\mu}g/ml$ ciprofloxacin (CIP). A mutant with a GyrB (Ser464$\rightarrow$Leu) and GyrA (Asp87$\rightarrow$Gly) substitution did not show a significant increase in the minimum inhibitory concentration (MIC) of CIP. None of the in vitro mutants exhibited mutations in parE. Thus, gyrA and parC should be considered to be the primary and secondary targets, respectively, of quinolones in E. tarda.

• Journal of dental hygiene science
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• v.12 no.2
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• pp.109-113
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• 2012

One hundred seventy four Streptococcus pneumoniae clinical isolates were categorized depending on the types of specimens, the age and the gender, respectively. All isolates were analyzed the characteristics of the multi-drug resistance including levofloxacin antibiotics. In the results of analysis depending on the type of samples, it had been confirmed that sputum was the main source of pneumonia infection because 156 of 174 strains (89.7%) were isolated in sputum samples. The opportunity for isolating the S. pneumoniae that had tolerance to levofloxacin was increased in over 51 age patients group compared with other age and male group. Eight strains of isolates were evaluated higher resistant to levofloxacin, and those also showed multi-drug resistant including penicillin, tetracycline, erythromycin, clindamycin and trimethoprim-sulfamethoxazole. In the results of sequence analysis of quinolone resistance determining region in SP32 (MIC $64{\mu}g/mL$) and SP96 (MIC $8{\mu}g/mL$) which were levofloxacin resistant strains, an amino acid substitutions were found Ser-81$\rightarrow$Phe in both GyrA of SP32 and SP96, and Ser-11$\rightarrow$Gly in only SP96. A Ser-79$\rightarrow$Phe substitution of ParC was found in both.

• Tuberculosis and Respiratory Diseases
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• v.66 no.5
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• pp.358-364
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• 2009

Background: The appropriate empirical antimicrobial choice in the treatment of community-acquired pneumonia (CAP) should be advocated by community-based information on the etiologic pathogens, their susceptibility to antimicrobials, clinical characteristics and outcomes. Jeju is a geographically isolated and identical region in Korea. However, there is no regional reference on adult CAP available. This study investigated the etiologic agents and clinical outcomes of adult patients diagnosed with CAP in Jeju, Korea, to help guide the empirical antimicrobial choice. Methods: A prospective observational study for one year in a referral hospital in Jeju, Korea. Patients diagnosed with CAP were enrolled with their clinical characteristics. Microbiological evaluations to identify the etiologic agents in the adult patients with CAP were performed with blood culture, expectorated sputum smear and culture, antibody tests for mycoplasma, chlamydophila, and antigen tests for legionella and pneumococcus. The clinical outcomes of the initial empirical treatment were analyzed. Results: Two hundred and three patients with mean age of 64 and 79 females were enrolled. Ten microbials from 90 cases (44.3%) were isolated and multiple isolates were confirmed in 30. Among the microbial isolates, S. pneumoniae (36.3%) was the most common, followed by M. pneumoniae (23.0%), C. pneumoniae (17.0%), S. aureus (9.6%) and P. aeruginosa (5.9%). The initial treatment failure (23.8%) was related to the isolation of polymicrobial pathogens, elevated inflammatory markers, and the presence of pleural effusion. Among the 30 isolates of S. pneumoniae, 16 (53.3%) were not susceptible to penicillin, and 19 isolates (63.3%) to erythromycin and clarithromycin. However, 29 isolates (96.7%) were susceptible to levofloxacin and ceftriaxone. Conclusion: S. pneumoniae, M. pneumoniae, S. aureus, and P. aeruginosa are frequent etiologic agents of adult CAP in Jeju, Korea. The clinical characteristics and antibiotic resistance should be considered when determining the initial empirical antimicrobial choice. Respiratory quinolone or ceftriaxone is recommended as an empirical antimicrobiotic in the treatment of adult CAP in Jeju, Korea.