# | Rank | Similarity | Title + Abs. | Year | PMID |
|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 |
| 2475 | 0 | 0.9507 | Examination of single and multiple mutations involved in resistance to quinolones in Staphylococcus aureus by a combination of PCR and denaturing high-performance liquid chromatography (DHPLC). Detection of DNA sequence variation is fundamental to the identification of the genomic basis of phenotypic variability. Denaturing high-performance liquid chromatography (DHPLC) is a novel technique that has been used to detect mutations in human DNA. We report on the first study to use this technique as a tool to detect mutations in genes encoding antibiotic resistance in bacteria. Three methicillin-sensitive and three methicillin-resistant clinical Staphylococcus aureus isolates, susceptible to ciprofloxacin (MIC | 2002 | 12407120 |
| 5221 | 1 | 0.9507 | Molecular cloning of the DNA gyrase genes from Methylovorus sp. strain SS1 and the mechanism of intrinsic quinolone resistance in methylotrophic bacteria. The genes encoding the DNA gyrase A (GyrA) and B subunits (GyrB) of Methylovorus sp. strain SS1 were cloned and sequenced. gyrA and gyrB coded for proteins of 846 and 799 amino acids with calculated molecular weights of 94,328 and 88,714, respectively, and complemented Escherichia coli gyrA and gyrB temperature sensitive (ts) mutants. To analyze the role of type II topoisomerases in the intrinsic quinolone resistance of methylotrophic bacteria, the sequences of the quinolone resistance-determining regions (QRDRs) in the A subunit of DNA gyrase and the C subunit (ParC) of topoisomerase IV (Topo IV) of Methylovorus sp. strain SS1, Methylobacterium extorquens AM1 NCIB 9133, Methylobacillus sp, strain SK1 DSM 8269, and Methylophilus methylotrophus NCIB 10515 were determined. The deduced amino acid sequences of the QRDRs of the ParCs in the four methylotrophic bacteria were identical to that of E. coli ParC. The sequences of the QRDR in GyrA were also identical to those in E. coli GyrA except for the amino acids at positions 83, 87, or 95. The Ser83 to Thr substitution in Methylovorus sp. strain SS1, and the Ser83 to Leu and Asp87 to Asn substitutions in the three other methylotrophs, agreed well with the minimal inhibitory concentrations of quinolones in the four bacteria, suggesting that these residues play a role in the intrinsic susceptibility of methylotrophic bacteria to quinolones. | 2005 | 16404155 |
| 5377 | 2 | 0.9476 | Synthetic lincosamides iboxamycin and cresomycin are active against ocular multidrug-resistant methicillin-resistant Staphylococcus aureus carrying erm genes. OBJECTIVE: Antimicrobial resistance is a global pandemic that poses a major threat to vision health as ocular bacteria, especially methicillin-resistant Staphylococcus aureus (MRSA), are becoming increasingly resistant to first-line therapies. Here we evaluated the antimicrobial activity of new synthetic lincosamides in comparison to currently used antibiotics against clinical ocular MRSA isolates. METHODS: Antimicrobial susceptibility testing was performed by broth microdilution for two novel synthetic lincosamides (iboxamycin and cresomycin) and eight comparator antibiotics against a collection of 50 genomically characterised ocular MRSA isolates, including isolates harbouring erm genes (n = 25). RESULTS: Both drugs were active against widespread MRSA clonal complexes CC8 and CC5. The MIC(50) and MIC(90) of iboxamycin were 0.06 and 2 mg/L, respectively. Cresomycin (MIC(50) = 0.06 mg/L) also displayed good activity with an in vitro potency four-fold higher (MIC(90) = 0.5 mg/L) than iboxamycin. In isolates harbouring erm genes, MIC(90) were >16, 2, and 0.5 mg/L for clindamycin, iboxamycin, and cresomycin, respectively. The in vitro potencies of iboxamycin and cresomycin were similar or higher than that of comparator agents and were not impacted by multidrug-resistance phenotypes or by the presence of erm genes when compared with clindamycin. CONCLUSIONS: Our results demonstrate that iboxamycin and cresomycin display potent in vitro activity against ocular MRSA isolates, including multidrug-resistant isolates harbouring erm genes. | 2024 | 39293511 |
| 828 | 3 | 0.9469 | Screening for Resistant Bacteria, Antimicrobial Resistance Genes, Sexually Transmitted Infections and Schistosoma spp. in Tissue Samples from Predominantly Vaginally Delivered Placentae in Ivory Coast and Ghana. Medical complications during pregnancy have been frequently reported from Western Africa with a particular importance of infectious complications. Placental tissue can either become the target of infectious agents itself, such as, e.g., in the case of urogenital schistosomiasis, or be subjected to contamination with colonizing or infection-associated microorganisms of the cervix or the vagina during vaginal delivery. In the retrospective cross-sectional assessment presented here, the quantitative dimension of infection or colonization with selected resistant or pathogenic bacteria and parasites was regionally assessed. To do so, 274 collected placental tissues from Ivory Coastal and Ghanaian women were subjected to selective growth of resistant bacteria, as well as to molecular screening for beta-lactamase genes, Schistosoma spp. and selected bacterial causative agents of sexually transmitted infections (STI). Panton-Valentine-negative methicillin-resistant Staphylococcus aureus (MRSA) was grown from 1.8% of the tissue samples, comprising the spa types t008 and t688, as well as the newly detected ones, t12101 (n = 2) and t12102. While the culture-based recovery of resistant Enterobacterales and nonfermentative rod-shaped Gram-negative bacteria failed, molecular assessments confirmed beta-lactamase genes in 31.0% of the samples with multiple detections of up to four resistance genes per sample and bla(CTX-M), bla(IMP), bla(GES), bla(VIM), bla(OXA-58)-like, bla(NDM), bla(OXA-23)-like, bla(OXA-48)-like and bla(KPC) occurring in descending order of frequency. The beta-lactamase genes bla(OXA-40/24)-like, bla(NMC_A/IMI), bla(BIC), bla(SME), bla(GIM) and bla(DIM) were not detected. DNA of the urogenital schistosomiasis-associated Schistosoma haematobium complex was recorded in 18.6% of the samples, but only a single positive signal for S. mansoni with a high cycle-threshold value in real-time PCR was found. Of note, higher rates of schistosomiasis were observed in Ghana (54.9% vs. 10.3% in Ivory Coast) and Cesarean section was much more frequent in schistosomiasis patients (61.9% vs. 14.8% in women without Schistosoma spp. DNA in the placenta). Nucleic acid sequences of nonlymphogranuloma-venereum-associated Chlamydia trachomatis and of Neisseria gonorrhoeae were recorded in 1.1% and 1.9% of the samples, respectively, while molecular attempts to diagnose Treponema pallidum and Mycoplasma genitalium did not lead to positive results. Molecular detection of Schistosoma spp. or STI-associated pathogens was only exceptionally associated with multiple resistance gene detections in the same sample, suggesting epidemiological distinctness. In conclusion, the assessment confirmed considerable prevalence of urogenital schistosomiasis and resistant bacterial colonization, as well as a regionally expected abundance of STI-associated pathogens. Continuous screening offers seem advisable to minimize the risks for the pregnant women and their newborns. | 2023 | 37623959 |
| 6012 | 4 | 0.9468 | Metal resistance-related genes are differently expressed in response to copper and zinc ion in six Acidithiobacillus ferrooxidans strains. Metal resistance of acidophilic bacteria is very significant during bioleaching of copper ores since high concentration of metal is harmful to the growth of microorganisms. The resistance levels of six Acidithiobacillus ferrooxidans strains to 0.15 M copper and 0.2 M zinc were investigated, and eight metal resistance-related genes (afe-0022, afe-0326, afe-0329, afe-1143, afe-0602, afe-0603, afe-0604, and afe-1788) were sequenced and analyzed. The transcriptional expression levels of eight possible metal tolerance genes in six A. ferrooxidans strains exposed to 0.15 M Cu(2+) and 0.2 M Zn(2+) were determined by real-time quantitative PCR (RT-qPCR), respectively. The copper resistance levels of six A. ferrooxidans strains declined followed by DY26, DX5, DY15, GD-B, GD-0, and YTW. The zinc tolerance levels of six A. ferrooxidans strains exposed to 0.2 M Zn(2+) from high to low were YTW > GD-B > DY26 > GD-0 > DX5 > DY15. Seven metal tolerance-related genes all presented in the genome of six strains, except afe-0604. The metal resistance-related genes showed different transcriptional expression patterns in six A. ferrooxidans strains. The expression of gene afe-0326 and afe-0022 in six A. ferrooxidans strains in response to 0.15 M Cu(2+) showed the same trend with the resistance levels. The expression levels of genes afe-0602, afe-0603, afe-0604, and afe-1788 in six strains response to 0.2 M Zn(2+) did not show a clear correlation between the zinc tolerance levels of six strains. According to the results of RT-qPCR and bioinformatics analysis, the proteins encoded by afe-0022, afe-0326, afe-0329, and afe-1143 were related to Cu(2+) transport of A. ferrooxidans strains. | 2014 | 25023638 |
| 1254 | 5 | 0.9464 | Genetic diversity and antimicrobial resistance of Staphylococcus aureus from recurrent tonsillitis in children. The aim of this study was to analyze the prevalence of Staphylococcus aureus in the tonsils of children subjected tonsillectomy due to recurrent tonsilitis and to determine the spa types of the pathogens, carriage of virulence genes and antimicrobial resistance profiles. The study included 73 tonsillectomized children. Bacteria, including S. aureus were isolated from tonsillar surface prior to tonsillectomy, recovered from tonsillar core at the time of the surgery, and from posterior pharynx 2-4 weeks after the procedure. Staphylococcus aureus isolates were compared by spa typing, tested for antimicrobial susceptibility and for the presence of superantigenic toxin genes (sea-seu, eta, etb, tst, lukS/lukF-PV) by multiplex polymerase chain reaction. Seventy-three patients (mean 7.1 ± 4.1 years, 61.6% male) were assessed. The most commonly isolated bacteria were S. aureus. The largest proportion of staphylococcal isolates originated from tonsillar core (63%), followed by tonsillar surface (45.1%) and posterior pharynx in tonsillectomized children (18.2%, p = 0.007). Five (6.3%) isolates were identified as MRSA (mecA-positive). Up to 67.5% of the isolates synthesized penicillinases (blaZ-positive isolates), and 8.8% displayed MLS(B) resistance. The superantigenic toxin genes were detected in more than half of examined isolates (56.3%). spa types t091, t084, and t002, and clonal complexes (CCs) CC7, CC45, and CC30 turned out to be most common. Staphylococcus aureus associated with RT in children showed pathogenicity potential and considerable genetic diversity, and no clones were found to be specific for this condition although further studies are needed. | 2020 | 31692060 |
| 2478 | 6 | 0.9463 | Study on the resistance mechanism via outer membrane protein OprD2 and metal β-lactamase expression in the cell wall of Pseudomonas aeruginosa. The aim of the present study was to evaluate the imipenem-resistant mechanism via the outer membrane protein (OMP) OprD2 and metal β-lactamase expression in the cell wall of Pseudomonas aeruginosa. The Pseudomonas aeruginosa was clinically separated and validated by VITEK-2 full-automatic bacteria analyzer. Drug resistance, sensitive antibiotics and minimum inhibitory concentration (MIC) were tested using the drug sensitivity analysis system. The phenotype positive strains of MBL genes were screened using the Kirby-Bauer diffusion method by adding metal ion-chelating agent EDTA on the imipenem susceptibility paper. IMP-1, VIM-1 and SPM metaloenzyme genes were tested by polymerase chain reaction (PCR)-telomeric repeat amplification protocol (TRAP). The OMP OprD2 genes were tested by PCR-TRAP, and the protein expression was tested using western blot analysis. The location of OMP OprD2 was confirmed using the sodium salicylate inhibition test. The results showed that 80 portions (40%) of MBL-positive strains were screened out of 200 specimens. Imipenem-resistant Pseudomonas aeruginosa (IRPA) and MIC values were significantly higher than quality control bacteria and control bacteria (P<0.05). A total of 35 cases with IMP-1 positive, 20 with VIM-1 positive, 16 with SPM positive, 5 with 2 positive genes and 4 with 3 positive genes were screened among MBL positive strains. A total of 150 portions (75%) of OprD2 deficiencies were screened from 200 specimens. The standard strains and sensitive strains showed OprD2 protein bands at 45 kDa while no OprD2 protein bands appeared in OprD2 deficiency strains. It was in accordance with gene detection. In conclusion, OMP OprD2 deficiency and MBL phenotype positivity may be important mechanisms of IRPA. | 2016 | 27882088 |
| 5375 | 7 | 0.9462 | Mechanism of Eravacycline Resistance in Clinical Enterococcus faecalis Isolates From China. Opportunistic infections caused by multidrug-resistant Enterococcus faecalis strains are a significant clinical challenge. Eravacycline (Erava) is a synthetic fluorocycline structurally similar to tigecycline (Tige) that exhibits robust antimicrobial activity against Gram-positive bacteria. This study investigated the in vitro antimicrobial activity and heteroresistance risk of Eravacycline (Erava) in clinical E. faecalis isolates from China along with the mechanism of Erava resistance. A total of 276 non-duplicate E. faecalis isolates were retrospectively collected from a tertiary care hospital in China. Heteroresistance to Erava and the influence of tetracycline (Tet) resistance genes on Erava susceptibility were examined. To clarify the molecular basis for Erava resistance, E. faecalis variants exhibiting Erava-induced resistance were selected under Erava pressure. The relative transcript levels of six candidate genes linked to Erava susceptibility were determined by quantitative reverse-transcription PCR, and their role in Erava resistance and heteroresistance was evaluated by in vitro overexpression experiments. We found that Erava minimum inhibitory concentrations (MICs) against clinical E. faecalis isolates ranged from ≤0.015 to 0.25 mg/l even in strains harboring Tet resistance genes. The detection frequency of Erava heteroresistance in isolates with MICs ≤ 0.06, 0.125, and 0.25 mg/l were 0.43% (1/231), 7.5% (3/40), and 0 (0/5), respectively. No mutations were detected in the 30S ribosomal subunit gene in Erava heteroresistance-derived clones, although mutations in this subunit conferred cross resistance to Tige in Erava-induced resistant E. faecalis. Overexpressing RS00630 (encoding a bone morphogenetic protein family ATP-binding cassette transporter substrate-binding protein) in E. faecalis increased the frequency of Erava and Tige heteroresistance, whereas RS12140, RS06145, and RS06880 overexpression conferred heteroresistance to Tige only. These results indicate that Erava has potent in vitro antimicrobial activity against clinical E. faecalis isolates from China and that Erava heteroresistance can be induced by RS00630 overexpression. | 2020 | 32523563 |
| 6085 | 8 | 0.9459 | Heavy metal resistance and genotypic analysis of metal resistance genes in gram-positive and gram-negative bacteria present in Ni-rich serpentine soil and in the rhizosphere of Alyssum murale. Forty-six bacterial cultures, including one culture collection strain, thirty from the rhizosphere of Alyssum murale and fifteen from Ni-rich soil, were tested for their ability to tolerate arsenate, cadmium, chromium, zinc, mercury, lead, cobalt, copper, and nickel in their growth medium. The resistance patterns, expressed as minimum inhibitory concentrations, for all cultures to the nine different metal ions were surveyed by using the agar dilution method. A large number of the cultures were resistant to Ni (100%), Pb (100%), Zn (100%), Cu (98%), and Co (93%). However, 82, 71, 58 and 47% were sensitive to As, Hg, Cd and Cr(VI), respectively. All cultures had multiple metal-resistant, with heptametal resistance as the major pattern (28.8%). Five of the cultures (about of 11.2% of the total), specifically Arthrobacter rhombi AY509239, Clavibacter xyli AY509235, Microbacterium arabinogalactanolyticum AY509226, Rhizobium mongolense AY509209 and Variovorax paradoxus AY512828 were tolerant to nine different metals. The polymerase chain reaction in combination with DNA sequence analysis was used to investigate the genetic mechanism responsible for the metal resistance in some of these gram-positive and gram-negative bacteria that were, highly resistant to Hg, Zn, Cr and Ni. The czc, chr, ncc and mer genes that are responsible for resistance to Zn, Cr, Ni and Hg, respectively, were shown to be present in these bacteria by using PCR. In the case of, M. arabinogalactanolyticum AY509226 these genes were shown to have high homology to the czcD, chrB, nccA, and mer genes of Ralstonia metallidurans CH34. Therefore, Hg, Zn, Cr and Ni resistance genes are widely distributed in both gram-positive and gram-negative isolates obtained from A. murale rhizosphere and Ni-rich soils. | 2007 | 17276484 |
| 1247 | 9 | 0.9458 | Antibiotic resistance determinants of multidrug-resistant Acinetobacter baumannii clinical isolates in Algeria. Antibiotic susceptibility testing was performed on 71 Acinetobacter baumannii clinical isolates, and presence of antibiotic resistance genes was screened for by PCR amplification and sequencing. Resistance rates were very high for aminoglycosides (22-80%), fluoroquinolones (>90%), and cephalosporins (>90%) but remained low for rifampin (2.8%) or null for colistin. Antibiotic resistance encoding genes detected were as follows: blaTEM-128 gene (74.6%), aph(3')-VI (50.7 %), aadA (63.4%), ant(2″)-I (14.1%), aac(3)-Ia (91.1%), aac(6')-Ib (4.2%), mutation Ser83Leu in gyrA (94.4%), double mutations Ser83Leu and Ser80Leu (or Ser84Leu) in gyrA and parC (69.0%), and mutation I581N in RRDR of the rpoB gene. | 2013 | 23688522 |
| 1400 | 10 | 0.9457 | Comparative genomic analysis of Escherichia coli strains obtained from continuous imipenem stress evolution. The carbapenem-resistant Escherichia coli has aroused increasing attention worldwide, especially in terms of imipenem (IMP) resistance. The molecular mechanism of IMP resistance remains unclear. This study aimed to explore the resistance mechanisms of IMP in E. coli. Susceptible Sx181-0-1 strain was induced into resistance strains by adaptive laboratory evolution. The drug resistance spectrum was measured using the disk diffusion and microbroth dilution methods. Whole-genome sequencing and resequencing were used to analyze the nonsynonymous single-nucleotide polymorphisms (nsSNPs) between the primary susceptible strain and resistant strains. The expression levels of these genes with nsSNPs were identified by real-time quantitative PCR (RT-qPCR). Resistance phenotype appeared in the induced 15th generation (induction time = 183 h). Sx181-32 and Sx181-256, which had the minimum inhibitory concentrations of IMP of 8 and 64 µg ml-1, were isolated during continuous subculture exposed to increasing concentrations of IMP, respectively. A total of 19 nsSNPs were observed both in Sx181-32 and Sx181-256, distributed in rpsU, sdaC, zwf, ttuC, araJ, dacC, mrdA, secF, dacD, lpxD, mrcB, ftsI, envZ, and two unknown function genes (orf01892 and orf01933). Among these 15 genes, five genes (dacC, mrdA, lpxD, mrcB, and ftsI) were mainly involved in cell wall synthesis. The mrdA (V338A, L378P, and M574I) and mrcB (P784L, A736V, and T708A) had three amino acid substitutions, respectively. The expression levels of rpsU, ttuC, and orf01933 were elevated in both Sx181-32 and Sx181-256 compared to Sx181-0-1. The expression levels of these genes were elevated in Sx181-256, except for araJ. Bacteria developed resistance to antimicrobials by regulating various biological processes, among which the most involved is the cell wall synthesis (dacC, mrdA, lpxD, mrcB, and ftsI). The combination mutations of mrdA, envZ, and ftsI genes may increase the resistance to IMP. Our study could improve the understanding of the molecular mechanism of IMP resistance in E. coli. | 2022 | 35147175 |
| 1255 | 11 | 0.9456 | Emergence of quinupristin/dalfopristin resistance among livestock-associated Staphylococcus aureus ST9 clinical isolates. Quinupristin/dalfopristin (Q/D) is a valuable alternative to vancomycin for the treatment of meticillin-resistant Staphylococcus aureus (MRSA) infections. However, not long after Q/D was approved, bacteria with resistance to this newer antimicrobial agent were reported. To investigate the prevalence of Q/D resistance, a total of 1476 non-duplicate S. aureus isolates, including 775 MRSA, from a Chinese tertiary hospital were selected randomly from 2003 to 2013. Of the 775 MRSA, 3 (0.4%) were resistant to Q/D. All meticillin-susceptible S. aureus were susceptible to Q/D. The prevalence of Q/D resistance among S. aureus was 0.2% (3/1476). The three isolates with Q/D resistance had the same antimicrobial resistance profile, except for cefaclor and chloramphenicol. All three Q/D-resistant MRSA were positive for five streptogramin B resistance genes (ermA, ermB, ermC, msrA and msrB) and two streptogramin A resistance genes (vatC and vgaA) as determined by PCR and DNA sequencing. MRSA WZ1031 belonged to ST9-MRSA-SCCmecV-t899, whilst MRSA WZ414 and WZ480 belonged to ST9-MRSA-SCCmecNT(non-typeable)-t899. ST9 has been reported predominantly in livestock-associated (LA) MRSA in some Asian countries. The three patients with these MRSA isolates were not livestock handlers and did not keep close contact with livestock. The origin of these important LA-MRSA isolates causing human infections is not known. Taken together, Q/D resistance, which was caused by a combination of ermA-ermB-ermC-msrA-msrB-vatC-vgaA, was first found among S. aureus clinical isolates in China. The present study is the first report of the emergence of human infections caused by ST9 LA-MRSA isolates with Q/D resistance. | 2014 | 25218154 |
| 5981 | 12 | 0.9456 | Alterations in the DNA topoisomerase IV grlA gene responsible for quinolone resistance in Staphylococcus aureus. A 4.2-kb DNA fragment conferring quinolone resistance was cloned from a quinolone-resistant clinical isolate of Staphylococcus aureus and was shown to possess a part of the grlB gene and a mutated grlA gene. S-80-->F and E-84-->K mutations in the grlA gene product were responsible for the quinolone resistance. The mutated grlA genes responsible for quinolone resistance were dominant over the wild-type allele, irrespective of gene dosage in a transformation experiment with the grlA gene alone. However, dominance by mutated grlA genes depended on gene dosage when bacteria were transformed with the grlA and grlB genes in combination. Quinolone-resistant gyrA mutants were easily isolated from a strain, S. aureus RN4220, carrying a plasmid with the mutated grlA gene, though this was not the case for other S. aureus strains lacking the plasmid. The elimination of this plasmid from such quinolone-resistant gyrA mutants resulted in marked increases in quinolone susceptibility. These results suggest that both DNA gyrase and DNA topoisomerase IV may be targets of quinolones and that the quinolone susceptibility of organisms may be determined by which of these enzymes is most quinolone sensitive. | 1996 | 8723458 |
| 2287 | 13 | 0.9454 | Expression of norA, norB and norC efflux pump genes mediating fluoroquinolones resistance in MRSA isolates. INTRODUCTION: Although fluoroquinolones are used to treat methicillin-resistant Staphylococcus aureus (MRSA)-induced infections, acquisition of antibiotic resistance by bacteria has impaired their clinical relevance. We aimed to evaluate the frequency of norA, norB, and norC efflux pump genes-mediating fluoroquinolones resistance and measure their expression levels in MRSA isolates. METHODOLOGY: 126 S. aureus isolates were collected from different clinical samples of adult hospitalized patients and identified by conventional microbiological methods. MRSA was diagnosed by cefoxitin disc diffusion method and minimum inhibitory concentration (MIC) of ciprofloxacin by broth microdilution method. The expression levels of efflux pump genes were measured by quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS: 80 (63.5%) MRSA isolates were identified and showed high level of resistance to erythromycin (80%), gentamicin (75%), clindamycin (65%) and ciprofloxacin (60 %). norA, norB and norC were detected in 75%, 35% and 55% of the MRSA isolates respectively. norC was the most commonly overexpressed gene measured by qRT-PCR, occurring in 40% of MRSA isolates, followed by norA (35%) and norB (30%). The expression of these genes was significantly higher in ciprofloxacin-resistant than quantitative real-time PCR ciprofloxacin-sensitive MRSA isolates. CONCLUSIONS: This study showed high prevalence and overexpression of efflux pump genes among MRSA isolates which indicates the significant role of these genes in the development of multidrug resistance against antibiotics including fluoroquinolones. | 2024 | 38635612 |
| 5376 | 14 | 0.9453 | In vitro Activity of Contezolid Against Methicillin-Resistant Staphylococcus aureus, Vancomycin-Resistant Enterococcus, and Strains With Linezolid Resistance Genes From China. Contezolid is a novel oxazolidinone, which exhibits potent activity against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and penicillin-resistant Streptococcus pneumoniae (PRSP). In this study, the in vitro activity of contezolid was compared with linezolid (LZD), tigecycline (TGC), teicoplanin (TEC), vancomycin (VA), daptomycin (DAP), and florfenicol (FFC) against MRSA and VRE strains isolated from China. Contezolid revealed considerable activity against MRSA and VRE isolates with MIC(90) values of 0.5 and 1.0 μg/mL, respectively. For VRE strains with different resistance genotypes, including vanA- and vanM-type strains, contezolid did not exhibit significantly differential antibacterial activity. Furthermore, the antimicrobial activity of contezolid is similar to or slightly better than that of linezolid against MRSA and VRE strains. Subsequently, the activity of contezolid was tested against strains carrying linezolid resistance genes, including Staphylococcus capitis carrying cfr gene and Enterococcus faecalis carrying optrA gene. The results showed that contezolid exhibited similar antimicrobial efficacy to linezolid against strains with linezolid resistance genes. In general, contezolid may have potential benefits to treat the infections caused by MRSA and VRE pathogens. | 2021 | 34489919 |
| 2446 | 15 | 0.9453 | Low selection of topoisomerase mutants from strains of Escherichia coli harbouring plasmid-borne qnr genes. OBJECTIVES: To investigate mutations in the type II topoisomerase genes in quinolone-resistant mutants selected from bacteria harbouring plasmid-borne qnr genes. METHODS: Mutants were selected by nalidixic acid, ciprofloxacin and moxifloxacin from two Escherichia coli reference strains and corresponding transconjugants harbouring qnrA1, qnrA3, qnrB2 or qnrS1 genes. RESULTS: The proportion of resistant mutants selected by the three quinolones was, respectively, in the same range for qnr-positive transconjugants and reference strains. Only 20% (65/329) of the mutants selected from the transconjugants showed a gyrase mutation, whereas 79% (94/119) of those from the reference strains without a qnr gene did (P < 0.0001). At four times the MIC of the selector quinolone, gyrA mutants represented 49% and 95% of the mutants selected with nalidixic acid, 4% and 94% with ciprofloxacin and 0% and 54% with moxifloxacin for qnr-positive transconjugants and reference strains, respectively. Mutations within gyrA were distributed at codon 87 (D87G, H, N or Y) and at codon 83 (S83L) with three novel mutations (gyrA Ser83stop, gyrA Asp82Asn and gyrB insertion of Glu at 465) and three rare mutations (gyrA Gly81Asp, gyrA Asp82Gly and gyrA Ser431Pro), mainly obtained from reference strains after moxifloxacin selection. Strikingly, none of the mutants selected by moxifloxacin from qnr-positive transconjugants harboured a mutation in the topoisomerase genes. CONCLUSIONS: Topoisomerase mutants are rarely selected by ciprofloxacin and moxifloxacin from strains harbouring qnr. This suggests that the quinolone resistance-determining region domains are protected from quinolones by the Qnr protein and consequently other mechanisms are developed to acquire a further step of fluoroquinolone resistance. | 2008 | 18325893 |
| 5223 | 16 | 0.9453 | Cloned ermTR Gene Confers Low Level Erythromycin but High Level Clindamycin Resistance in Streptococcus pyogenes NZ131. Objectives: The most common macrolide resistance mechanisms in streptococci are the presence of methylase encoding genes ermB and ermTR or the presence of efflux encoded by mef genes. In the present study we aimed to show the effects of the ermTR gene under isogenic conditions on the activities of macrolides and lincosamides in streptococci. Materials and Methods: Total DNA was extracted from Streptococcus pyogenes C1, and the ermTR gene was amplified with or without the regulatory region using modified primer with insertion of restriction sites to clone in to pUC18. Transformants were selected after electroporation of Escherichia coli DB10. The recombinant plasmids were purified and merged to pJIM2246 to transform Gram positive bacteria. Recombinant pJIM2246 plasmids with the ermTR gene were then introduced into S. pyogenes NZ131 by electroporation. Results: After transformation with ermTR without regulatory region the minimal inhibitory concentration (MIC) for erythromycin and clindamycin increased from ≤0.06 to ≤0.06 to 8 and >128 mg/L, respectively. Induction with erythromycin affected the MICs for clindamycin of S. pyogenes transformed with ermTR with the regulatory region. Double disk testing showed that induction with erythromycin and azithromycin for the S. pyogenes transformed with ermTR, and regulatory regions decreased the clindamycin inhibition zone but not telithromycin. The ermTR gene in isogenic conditions confers low level resistance to erythromycin and high level resistance to clindamycin. Conclusion: The different induction and resistance profiles of ermTR compared to other erm genes suggest that the methylation of ErmTR may be different than well studied methylases. | 2020 | 31971866 |
| 5416 | 17 | 0.9453 | Limited predictive power of known resistance genes for phenotypic drug resistance in clinical Mycobacterium abscessus complex from Beijing in China. Mycobacterium abscessus complex (MABC) is an emerging pathogen with intrinsic multidrug resistance. Genomic sequencing technology has been widely applied to predict bacterial resistance in other bacteria, but the catalog of known resistance-determining genes to explain phenotypic resistance in the MABC is incomplete for many antibiotics. Eighty-one MABC strains were isolated from sputum samples of patients with pulmonary disease in the Beijing Chest Hospital. All isolates were tested for minimum inhibitory concentrations (MICs) to eight antibiotics and underwent whole-genome sequencing (WGS). Of the total 81 MABC isolates, six strains exhibited clarithromycin (CLM) resistance by day 3 in culture, but only one (16.7%, 1/6) contained a mutation in the rrl gene. All M. abscessus strains contained the erm (41)28T (100.0%, 49/49) polymorphism and exhibited CLM-induced resistance after 14 days in culture. Of the 61 imipenem-resistant strains, 12 (19.7%, 12/61) had mutations in the bla gene. Although there were four (4.9%) amikacin-resistant, nine (11.1%) linezolid-resistant, eight (9.9%) clofazimine-resistant, 23 (28.4%) bedaquiline-resistant, and 27 (33.3%) cefoxitin-resistant strains, no known mutations associated with resistance to these antibiotics were found. These results suggest that the explanatory power of known resistance genes for clinical MABC resistance is limited and that other unidentified genes or novel resistance mechanisms may be involved. | 2025 | 40422286 |
| 6149 | 18 | 0.9453 | Characterization and whole-genome sequencing of an extreme arsenic-tolerant Citrobacter freundii SRS1 strain isolated from Savar area in Bangladesh. Citrobacter freundii SRS1, gram-negative bacteria, were isolated from Savar, Bangladesh. The strain could tolerate up to 80 mmol L(-1) sodium arsenite, 400 mmol L(-1) sodium arsenate, 5 mmol L(-1) manganese sulfate, 3 mmol L(-1) lead nitrate, 2.5 mmol L(-1) cobalt chloride, 2.5 mmol L(-1) cadmium acetate, and 2.5 mmol L(-1) chromium chloride. The whole-genome sequencing revealed that the genome size of C. freundii SRS1 is estimated to be 5.4 Mb long, and the G + C content is 51.7%. The genome of C. freundii SRS1 contains arsA, arsB, arsC, arsD, arsH, arsR, and acr3 genes for arsenic resistance; czcA, czcD, cbiN, and cbiM genes for cobalt resistance; chrA and chrB genes for chromium resistance; mntH, sitA, sitB, sitC, and sitD genes for manganese resistance; and zntA gene for lead and cadmium resistance. This novel acr3 gene has never previously been reported in any C. freundii strain except SRS1. A set of 130 completely sequenced strains of C. freundii was selected for phylogenomic analysis. The phylogenetic tree showed that the SRS1 strain is closely related to the C. freundii 62 strain. Further analyses of the genes involved in metal and metalloid resistance might facilitate identifying the mechanisms and pathways involved in high metal resistance in the C. freundii SRS1 strain. | 2023 | 36332226 |
| 5448 | 19 | 0.9451 | Virulence gene profiles, biofilm formation, and antimicrobial resistance of Vibrio cholerae non-O1/non-O139 bacteria isolated from West Bengal, India. Vibrio cholerae is the causative agent of acute dehydrating diarrhoeal disease cholera. Among 71 V. cholerae non-O1/non-O139 isolates, all yielded negative results for ctxA, ctxB and tcpA genes in PCR assay. Few strains were positive for stn (28.38%), and ompU (31.08%) genes. While all isolates were negative for ace gene, only two were positive for zot gene. All strains expressed toxR and toxT genes. It was also found that all isolates were slime-producer and these were capable of forming moderate to high biofilm. Biofilm formation was controlled positively by the transcriptional regulators VpsR and VpsT and was regulated negatively by HapR, as well as CRP regulatory complex. These isolates were resistant to ampicillin, furazolidone, doxycycline, vancomycin, erythromycin, while these were susceptible to ciprofloxacin, gentamycin, kanamycin, polymixin B, norfloxacin, chloramphenicol, sulphamethoxazole-trimethoprim, tetracycline, nalidixic acid, and streptomycin. Indeed, 69.01% isolates were resistant to multiple antibiotics (MAR: resistance to 3 or more antibiotics). Treatment protocols for cholera patients should be based on local antibiogram data. | 2018 | 30582054 |