• Journal of Microbiology
• /
• v.45 no.2
• /
• pp.168-170
• /
• 2007

In this research 26 Shigella isolates were examined by PCR and direct nucleotide sequencing for genetic alterations in the quinolone-resistance determining regions (QRDRs). We tested for the presence of qnr genes by PCR in 91 strains, but no qnr genes were found. The results did show, however, some novel mutations at codon 83 of gyrA ($Ser{\rightarrow}Ile$) and codon 64 of parC ($Ala64{\rightarrow}Cys,\;Ala64{\rightarrow}Asp$), which were related to fluroquinolone resistance.

• Biomedical Science Letters
• /
• v.10 no.4
• /
• pp.507-514
• /
• 2004

The Pseudomonas aeruginosa isolated from the clinical specimens has a mutation on the QRDR (quinolone resistance determining region). There were obvious mutations in both gyrA and parC gene which are major targets of quinolone. Simultaneous mutations were found two sites or more on these genes in all of ten strains. GyrB or parE gene had only silent mutation without converted amino acids. We confirmed that P. aeruginosa from clinical specimens exhibited decreased sensitivity to fluroquiolone due to changed Thr-83→lle and Asp-87→Asn types on gyrA and altered Ser-87→Leu type on parC. This is the first finding that a new Met-93→Thr type on parC as well as mutations on gyrB or parE genes differed from existing patterns. This study showed more mutations of gyrA rather than parC, suggesting that change of Type Ⅳ topoisomerase is more serious than that of type Ⅱ (DNA gyrase).

• Biomedical Science Letters
• /
• v.13 no.2
• /
• pp.141-148
• /
• 2007

We determined the sequences of the quinolone resistance-determining region (QRDR) of gyrA and gyrB for 21 clinical strains of Enterobacteriaceae resistant to ciprofloxacin, norfloxacin and levofloxacin. The clinical strains were isolated from the specimens of three general hospitals in Busan. In the present study, we found mutations in type II topoisomerase (DNA gyrase) genes for all strains. We confirmed that some genera of Enterobacteriaceae of clinical specimen exhibited decreased sensitivity to fluroquinolone due to changes in Ser-83$\rightarrow$Leu and Asp-87$\rightarrow$Asn types on gyrA and alterations in Glu-465$\rightarrow$Arg and Ser-492$\rightarrow$Asn type on gyrB. All the twenty-one strains had a missense mutation in gyrA (codon 83 and 87). Three of them had an additional mutation in gyrB (codon 465 or 492), but one of them had an additional mutation in gyrB (codon 426, 427, 491, 495 and 496). The strains which had two mutations in type II topoisomerase genes (gyrA and gyrB) were significantly more resistant to fluoroquinolones than those with a single mutation in gyrA (mean MICs of ciprofloxacin: $\geq8\mu$g/ml, mean MICs of levofloxacin: $\geq16\mu$g/ml). Interestingly, the examination of silent nucleotide changes n the gyrA and gyrB genes revealed six different patterns of DNA polymorphism, respectively. Fifteen strains of the twenty-one strains bearing the gyrase A mutation shared the same polymorphism and eleven strains of the twenty-one strains bearing the gyrase B mutation shared the same polymorphism.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1997.04a
• /
• pp.40-47
• /
• 1997

New quinolones generally have a broad antibacterial spectrum against gram-positive, gram-negative, glucose-nonfermenting and anaerobic bacteria. Some of newly developed quinolones have potent activities against S. aureus including MRSA, S.pneumoniae including PRSP, B. fragilis, chlamydiae, mycoplasmas and mycobacteria as well, and show good activities against various strains resistant to antibacterial agents of other classes. Quinolones display postantibiotic effects in vitro and are bactericidal at concentrations similar to or twice that of the minimum inhibitory concentrations (MICs) for susceptible pathogens. In experimental murine infection models including systemic infections with various pathogens such as S. aureus, S. pyogenes, S. pneumoniae, E. coli and P. aeruginosa, quinolones have shown good oral efficacy as well as parenteral efficacy. Good oral absorption and good tissue penetration of quinolones account for good therapeutic effects in clinical settings. The target of quinolones are two structurally related type II topoisomerases, DNA gyrase and DNA topoisomerase IV. Quinolones are shown to stabilize the ternary quinolone-gyrase-DNA complex and inhibit the religation of the cleaved double-stranded DNA. Bacteria can acquire resistance to quinolones by mutations of these target enzymes. Mutation sites and amino acid changes in DNA gyrase and DNA topoisomerase IV are similar in the organisms examined, suggesting that the mechanism of quinolone resistance in the target enzymes is essentially the same among various organisms. Quinolones act on both the target enzymes to different degrees depending on the organisms or agents tested, and bacteria become highly resistant to quinolones in a step-wise fashion. Incomplete cross-resistance among quinolones in some strains of E. coli and S. aureus suggests the possibility of finding quinolones active against quinolone-resistant strains which are prevailing now. To find such quinolones, the potency toward two target enzymes and the membrane permeability including influx and/or efflux systems should be taken into account.

• Korean Journal of Microbiology
• /
• v.35 no.3
• /
• pp.218-225
• /
• 1999

We isolated the ANRI fragment from Aspergillus nidulons that could autononlously replicate and enhance transformation efficiency about $10^4$ fold compared lo the integrative vector in Saccha,omgcer cerevisioe. In A. nidulans recombinant plasmid pLJ16-4.5 which carries the 4.5 kb EcoRI fragment of ANRI showed a 170-[old increase of transformation efficiency compared to the integrative vector pLJ16 and could be recovered from iransfonnants as an intact form. Estimated copy number of transforming plasmid pLJ16-4.5 was scored as 2 to 3 copies in transformed A. nidulans. Recoinbinant plasinid pILJ16-4.5 is inilotically unstable; being lost Irom 65% of aswual progeny of transformants on selective medium and 90% on complete medium. Southern analysis of transformant DNA showed that the pILJ16-4.5 is maintained in free form. The sequencing data showed that ANRl fragment was originated from mitochondiral DNA of A. nid~ilans and contained high AT content as much as 74.7%. One ARS consensus sequence (A/T)TTr4T(A/G)TTT(AiT). I I ARS-like sequence (agreement 10 of 11) and ABFl binding core consensus sequence (TCN7ACG). Also six gyrase binding core consensus sequence (YRTGNYNNY: y=C or T, R=A or G, N=A, G, C or T) of $\Phi$X174 and SV40 DNA and one b site (CACTTTACC) combining with gyrase in ColEl are shown. ANRl can be developed as a repl&ng plasinid for lransfoimation system in A. nirlulmis.

• The Plant Pathology Journal
• /
• v.32 no.2
• /
• pp.102-111
• /
• 2016

Olive culture is very important in the Mediterranean Basin. A severe outbreak of Olive Quick Decline Syndrome (OQDS) caused by Xylella fastidiosa infection was first noticed in 2013 on olive trees in the southern part of Apulia region (Lecce province, southern Italy). Studies were carried out for detection and diversity evaluation of the Apulian strain of Xylella fastidiosa. The presence of the pathogen in olive samples was detected by PCR amplifying the 16S rDNA, gyrase B subunit (gyrB) and HL hypothetical protein genes and single nucleotide polymorphisms (SNPs) assessment was performed to genotype X. fastidiosa. Twelve SNPs were recorded over gyrB and six SNPs were found for HL gene. Less variations were detected on 16S rDNA gene. Only gyrB and HL provided sufficient information for dividing the Apulian X. fastidiosa olive strains into subspecies. Using HL nucleotide sequences was possible to separate X. fastidiosa into subspecies pauca and fastidiosa. Whereas, nucleotide variation present on gyrB gene allowed separation of X. fastidiosa subsp. pauca from the other subspecies multiplex and fastidiosa. The X. fastidiosa strain from Apulia region was included into the subspecies pauca based on three genes phylogenetic analyses.

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

• YAKHAK HOEJI
• /
• v.39 no.1
• /
• pp.78-84
• /
• 1995

Based on Computer graphics molecular modeling method, quinolone derivatives as DNA-gyrase inhibitors formed stable DNA-intercalation complex with deoxycytidilyl-3',5'-deoxy guanosine[d($C_{p}G)_{2}$] dinucleotide. When d($C_{p}G)_{2}$ and d($A_{p}T)_{2}$, were compared in order to find out which DNA could form more stable DNA-Drug complex based on interaction energy($\Delta$E) and DNA-Drug complex energy, d($C_{p}G)_{2}$ resulted in lower energy than d($A_{p}T)_{2}$.

• Bulletin of the Korean Chemical Society
• /
• v.11 no.5
• /
• pp.376-379
• /
• 1990

To find out a correlation between antibacterial activity and physical properties of 7-substituted 1-ethyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylic acid, dipole moments, charge distributions, and hydrophobicities were calculated. The atomic charges and the dipole moments to not give any correlations with inhibition of DNA gyrase, but the calculated hydration free energies show some correlations.

• Microbiology and Biotechnology Letters
• /
• v.44 no.3
• /
• pp.324-332
• /
• 2016

A bacterial strain capable of hydrolyzing xylan was isolated from fermented soybean paste obtained from a domestic Buddhist temple, using enrichment culture with rice straw as a carbon source. The isolate, named YB-1301, was identified as Bacillus safensis on the basis of its DNA gyrase subunit B gene (gyrB) sequence. The xylanase productivity of strain YB-1301 was drastically increased when it was grown in the presence of wheat bran or various xylans. In particular, the maximum xylanase productivity reached above 340 U/ml in the culture filtrate from LB broth supplemented with only birchwood xylan at shake-flask level. The xylanase production was significantly induced by xylans at the stationary growth phase in LB medium containing xylan, whereas only a small amount of xylanase was constitutively produced from cells grown in LB medium with no addition of xylan. Furthermore, xylanase biosynthesis was induced more rapidly by the enzymatically hydrolyzed products of xylan than by the non-hydrolyzed xylan. In addition, the xylanase in the culture filtrate of B. safensis YB-1301 was found to have optimal activity at 55℃ and pH 6.5–7.0.