scholarly journals Alterations in GyrA and ParC Associated with Fluoroquinolone Resistance in Enterococcus faecium

1999 ◽  
Vol 43 (4) ◽  
pp. 947-949 ◽  
Author(s):  
Nagwa el Amin ◽  
Shah Jalal ◽  
Bengt Wretlind
Keyword(s):  
Enterococcus Faecalis ◽  
Resistant Strain ◽  
Enterococcus Faecium ◽  
The Other ◽  
Fluoroquinolone Resistance ◽  
Topoisomerase Iv ◽  
Gram Positive Bacteria ◽  
Efflux Mechanism ◽  
Resistant Strains ◽  
High Level

ABSTRACT High-level quinolone resistance in Enterococcus faeciumwas associated with mutations in both gyrA andparC genes in 10 of 11 resistant strains. One low-level resistant strain without such mutations may instead possess an efflux mechanism or alterations in the other subunits of the gyrase or topoisomerase IV genes. These findings are similar to those for other gram-positive bacteria, such as Enterococcus faecalis.

scholarly journals Development of fluoroquinolone resistance in Enterococcus faecalis and role of mutations in the DNA gyrase gyrA gene.

1996 ◽  
Vol 40 (11) ◽  
pp. 2558-2561 ◽  
Author(s):  
J Tankovic ◽  
F Mahjoubi ◽  
P Courvalin ◽  
J Duval ◽  
R Leclerco
Keyword(s):  
Enterococcus Faecalis ◽  
Resistant Isolate ◽  
Fluoroquinolone Resistance ◽  
Gyra Gene ◽  
Single Clone ◽  
Total Dna ◽  
Resistant Strains ◽  
French Hospital ◽  
High Level

We have analyzed the development of fluoroquinolone resistance between 1986 and 1993 among clinical isolates of Enterococcus faecalis from a French hospital. One hundred randomly selected isolates per year were screened for resistance to ciprofloxacin (MIC > 2 micrograms/ml) and for high-level resistance to gentamicin (MIC > 1,000 micrograms/ml). The percentages of ciprofloxacin-resistant strains for these years were as follows: 1986, 0; 1987, 1; 1988 to 1989, 2; 1990, 6; 1991, 16; 1992, 24; and 1993, 14. Eighty-three percent of the ciprofloxacin-resistant isolates were coresistant to high levels of gentamicin. Forty-eight high-level gentamicin-resistant E. faecalis strains, which were resistant (24 strains) or susceptible (24 strains) to ciprofloxacin, were examined by pulsed-field gel electrophoresis (PFGE) of SmaI-digested total DNA. Numerous PFGE types were observed among the ciprofloxacin-susceptible isolates, whereas one type was largely predominant among the ciprofloxacin-resistant strains, which suggests that the increase in fluoroquinolone resistance was due to the spread of a single clone. A 241-bp fragment of gyrA, corresponding to the quinolone resistance-determining region, was amplified and sequenced for seven ciprofloxacin-resistant isolates. Six strains had high levels of resistance (MICs, 32 to 64 micrograms/ml) and had a mutation at position 83 (Escherichia coli coordinates) from Ser to Arg (three strains) or to Ile (two strains) or at position 87 from Glu to Gly (one strain), whereas the low-level-resistant isolate (MIC, 8 micrograms/ml) had no mutations.

scholarly journals Combination of known and unknown mechanisms confers high-level resistance to fluoroquinolones in Enterococcus faecium

2006 ◽  
Vol 55 (6) ◽  
pp. 729-736 ◽  
Author(s):  
Yoshihiro Oyamada ◽  
Hideaki Ito ◽  
Kouichi Fujimoto ◽  
Reiko Asada ◽  
Toshiyuki Niga ◽  
...  
Keyword(s):  
Enterococcus Faecium ◽  
Efflux Pump ◽  
Point Mutations ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Bacterial Cells ◽  
Topoisomerase Iv ◽  
High Level ◽  
Spontaneous Mutants

In order to elucidate the mechanisms of fluoroquinolone resistance in Enterococcus faecium, spontaneous mutants isolated from Ent. faecium ATCC 19434 by stepwise selection with sparfloxacin (SPX) or norfloxacin (NOR) and 13 clinical isolates of Ent. faecium were characterized by analysing quinolone-resistance-determining regions (QRDRs) of the gyrA, gyrB, parC and parE genes and examining changes in MICs of SPX and NOR in the presence of efflux pump inhibitors. The SPX-selected first-step mutant had a point mutation only in gyrA, and the mutants QR7-18 and QR7-39, and clinical isolates that had point mutations in parC, showed NOR resistance. These results indicate that the primary targets of SPX and NOR are DNA gyrase and topoisomerase IV, respectively, and therefore that the primary target of fluoroquinolones in Ent. faecium differs depending on the structure of the compound used. The characterization of the spontaneous mutants and the clinical isolates demonstrates that in addition to the previously reported alterations in GyrA and ParC, an alteration in GyrB, a NorA-like pump, an unknown efflux pump, which excretes both SPX and NOR from bacterial cells, and probably other unknown mechanism(s) all contribute to fluoroquinolone resistance in Ent. faecium.

scholarly journals Emergence of the First Levofloxacin-Resistant Strains of Streptococcus agalactiae Isolated in Italy

2015 ◽  
Vol 59 (4) ◽  
pp. 2466-2469 ◽  
Author(s):  
G. Piccinelli ◽  
F. Gargiulo ◽  
S. Corbellini ◽  
G. Ravizzola ◽  
C. Bonfanti ◽  
...  
Keyword(s):  
Clonal Complex ◽  
Group B Streptococcus ◽  
Sequence Type ◽  
Fluoroquinolone Resistance ◽  
Topoisomerase Iv ◽  
Double Mutation ◽  
Unknown Significance ◽  
Resistant Strains ◽  
Group B ◽  
High Level

ABSTRACTOf 901 group B streptococcus strains analyzed, 13 (1.4%) were resistant to levofloxacin (MICs of >32 μg/ml for seven isolates, 2 μg/ml for four isolates, and 1.5 μg/ml for four isolates). Mutations in the quinolone resistance-determining regions (QRDRs) of gyrase and topoisomerase IV were identified. A double mutation involving the Ser-81 change to Leu forgyrAand the Ser-79 change to Phe or to Tyr forparCwas linked to a high level of fluoroquinolone resistance. In addition, two other mutational positions inparCwere observed, resulting in an Asp-83-to-Tyr substitution and an Asp-83-to-Asn substitution. Different mutations were also observed ingyrB, with unknown significance. Most levofloxacin-resistant GBS strains were of serotype Ib and belonged to sequence type 19 (ST19) and clonal complex 19 (CC-19). Most of them exhibited theepsilongene.

Topoisomerase mutations and efflux are associated with fluoroquinolone resistance in Enterococcus faecalis

2006 ◽  
Vol 55 (10) ◽  
pp. 1395-1401 ◽  
Author(s):  
Yoshihiro Oyamada ◽  
Hideaki Ito ◽  
Matsuhisa Inoue ◽  
Jun-ichi Yamagishi
Keyword(s):  
Enterococcus Faecalis ◽  
Efflux Pump ◽  
Resistance Mechanisms ◽  
Fluoroquinolone Resistance ◽  
Multidrug Efflux ◽  
Multidrug Efflux Pump ◽  
Topoisomerase Iv ◽  
Gram Positive Bacteria ◽  
Efflux Pump Inhibitors ◽  
Resistant Mutants

To understand better the mechanisms of fluoroquinolone resistance in Enterococcus faecalis, fluoroquinolone-resistant mutants isolated from Ent. faecalis ATCC 29212 by stepwise selection with sparfloxacin (SPX) and norfloxacin (NOR) were analysed. The results showed the following. (i) In general, fluoroquinolone-resistance mechanisms in Ent. faecalis are similar to those in other Gram-positive bacteria, such as Staphylococcus aureus and Streptococcus pneumoniae, namely, mutants with amino acid changes in both GyrA and ParC exhibited high fluoroquinolone resistance, and single GyrA mutants and a single ParC mutant were more resistant to SPX and NOR, respectively, than the parent strain, indicating that the primary targets of SPX and NOR in Ent. faecalis are DNA gyrase and topoisomerase IV, respectively. (ii) Alterations in GyrB (ΔKGA, residues 395–397) and ParE (Glu-459 to Lys) were associated with fluoroquinolone resistance in some mutants. Moreover, the facts that the NOR MIC, but not the SPX MIC, decreased in the presence of multidrug efflux pump inhibitors, that NOR accumulation decreased in the cells, and that the EmeA mRNA expression level did not change, strongly suggested that a NorA-like efflux pump, rather than EmeA, was involved in resistance to NOR.

scholarly journals Genetic evidence for a role of parC mutations in development of high-level fluoroquinolone resistance in Escherichia coli.

1996 ◽  
Vol 40 (4) ◽  
pp. 879-885 ◽  
Author(s):  
P Heisig
Keyword(s):  
Escherichia Coli ◽  
Fluoroquinolone Resistance ◽  
Gyra Gene ◽  
Topoisomerase Iv ◽  
E Coli ◽  
Resistant Strains ◽  
Gyra Mutation ◽  
High Level ◽  
Moderately Resistant

Fifteen strains of Escherichia coli with MICs of ciprofloxacin (CIP) between 0.015 and 256 micrograms/ml were examined for the presence of mutations in the quinolone resistance-determining region of the gyrA gene and in an analogous region of the parC gene. No mutation was found in a susceptible isolate (MIC of CIP, 0.015 microgram/ml). Four moderately resistant strains (MIC of CIP 0.06 to 4 micrograms/ml) carried one gyrA mutation affecting serine 83, but in only one strain was an additional parC mutation (Gly-78 to Asp) detected. All ten highly resistant strains examined (MIC of CIP, > 4 micrograms/ml) carried two gyrA mutations affecting residues serine 83 and aspartate 87, and at least one parC mutation. These parC mutations included alterations of serine 80 to arginine or isoleucine and glutamate 84 to glycine or lysine. The parC+ and two mutant alleles (parCI-80 and parCI-80,G-84) were inserted into the mobilizable vector pBP507. Transfer of a plasmid-coded parC+ allele into parC+ strains did not alter the susceptibilities towards ciprofloxacin or nalidixic acid, while a significant increase in susceptibility was detectable for parC mutants. This increase, however, did not restore wild-type susceptibility, whereas transfer of a plasmid-coded gyrA+ allele alone or in combination with parC+ did. These data are in agreement with the view that topoisomerase IV is a secondary, less sensitive target for quinolone action in Escherichia coli and that the development of high-level fluoroquinolone resistance in E. coli requires at least one parC mutation in addition to the gyrA mutation(s).

scholarly journals Alterations in the GyrA Subunit of DNA Gyrase and the ParC Subunit of DNA Topoisomerase IV Associated with Quinolone Resistance in Enterococcus faecalis

1998 ◽  
Vol 42 (2) ◽  
pp. 433-435 ◽  
Author(s):  
Emiko Kanematsu ◽  
Takashi Deguchi ◽  
Mitsuru Yasuda ◽  
Takeshi Kawamura ◽  
Yoshinori Nishino ◽  
...  
Keyword(s):  
Enterococcus Faecalis ◽  
Dna Gyrase ◽  
Quinolone Resistance ◽  
Clinical Isolates ◽  
Fluoroquinolone Resistance ◽  
Primary Target ◽  
Topoisomerase Iv ◽  
Dna Topoisomerase ◽  
High Level

ABSTRACT The gyrA and parC genes of 31 clinical isolates of Enterococcus faecalis, including fluoroquinolone-resistant isolates, were partially sequenced and analyzed for target alterations. Topoisomerase IV may be a primary target in E. faecalis, but high-level fluoroquinolone resistance was associated with simultaneous alterations in both GyrA and ParC.

Topoisomerase Sequences of Coagulase-Negative Staphylococcal Isolates Resistant to Ciprofloxacin or Trovafloxacin

1999 ◽  
Vol 43 (7) ◽  
pp. 1631-1637 ◽  
Author(s):  
Donald T. Dubin ◽  
Joseph E. Fitzgibbon ◽  
Massoumeh D. Nahvi ◽  
Joseph F. John
Keyword(s):  
Dna Gyrase ◽  
Fluoroquinolone Resistance ◽  
Topoisomerase Iv ◽  
Dna Topoisomerase ◽  
Methicillin Resistant ◽  
Intraspecies Variation ◽  
Rrna Sequencing ◽  
Identification Of Species ◽  
Resistant Strains ◽  
Ciprofloxacin Resistance

ABSTRACT Coagulase-negative staphylococcal isolates (n = 188) were screened for susceptibility to oxacillin, ciprofloxacin, and trovafloxacin, a new fluoroquinolone. At an oxacillin concentration of ≥4 μg/ml, 43% were methicillin resistant; of these, 70% were ciprofloxacin resistant (MIC, ≥4 μg/ml). Of the methicillin-resistant, ciprofloxacin-resistant isolates, 46% were susceptible to ≤2 μg of trovafloxacin per ml and 32% were susceptible to ≤1 μg of trovafloxacin per ml. Sixteen isolates, including twelve that expressed fluoroquinolone resistance, were chosen for detailed analysis. Identification of species by rRNA sequencing revealed a preponderance of Staphylococcus haemolyticus andS. hominis among fluoroquinolone-resistant strains. Segments of genes (gyrA and grlA) encoding DNA gyrase and DNA topoisomerase IV were sequenced. Considerable interspecies variation was noted, mainly involving noncoding nucleotide changes. Intraspecies variation consisted of coding changes associated with fluoroquinolone resistance. As for S. aureus, ciprofloxacin resistance (MIC, ≥8 μg/ml) and increased trovafloxacin MICs (0.25 to 2 μg/ml) could be conferred by the combined presence of single mutations in each gyrA and grlA gene. Trovafloxacin MICs of ≥8 μg/ml also occurred, but these required an additional mutation in grlA.

scholarly journals Interpretive criteria to differentiate low- and high-level mupirocin resistance in Staphylococcus aureus

2007 ◽  
Vol 56 (7) ◽  
pp. 937-939 ◽  
Author(s):  
Naira Elane Moreira de Oliveira ◽  
Ana Paula Couto Marques Cardozo ◽  
Elizabeth de Andrade Marques ◽  
Kátia Regina Netto dos Santos ◽  
Marcia Giambiagi deMarval
Keyword(s):  
Staphylococcus Aureus ◽  
High Resistance ◽  
The Other ◽  
Diffusion Method ◽  
Disc Diffusion ◽  
Disc Diffusion Method ◽  
Zone Diameter ◽  
Resistant Strains ◽  
Mupirocin Resistance ◽  
High Level

Meticillin-resistant Staphylococcus aureus isolates were classified into three mupirocin susceptibility groups by the disc diffusion method using 5 and 200 μg mupirocin discs. The zone diameter observed for a 5 μg disc distinguished MupS from the resistant strains (either MupRL or MupRH). On the other hand, a 200 μg disc distinguished the high-resistance MupRH strains from the other two (MupS or MupRL). Thus, the concomitant use of 5 and 200 μg mupirocin discs allowed the clear distinction among the three mupirocin susceptibility groups, MupS, MupRL or MupRH.

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