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Lopez E.,ISCIII Institute Salud Carlos III | Lopez E.,CIBER ISCIII | Domenech A.,CIBER ISCIII | Domenech A.,University of Barcelona | And 12 more authors.
PLoS ONE | Year: 2014

Antibiotic resistance in Streptococcus pneumoniae has increased worldwide by the spread of a few clones. Fluoroquinolone resistance occurs mainly by alteration of their intracellular targets, the type II DNA topoisomerases, which is acquired either by point mutation or by recombination. Increase in fluoroquinolone-resistance may depend on the balance between antibiotic consumption and the cost that resistance imposes to bacterial fitness. In addition, pneumococcal prophages could play an important role. Prophage induction by fluoroquinolones was confirmed in 4 clinical isolates by using Southern blot hybridization. Clinical isolates (105 fluoroquinolone-resistant and 160 fluoroquinolone-susceptible) were tested for lysogeny by using a PCR assay and functional prophage carriage was studied by mitomycin C induction. Fluoroquinolone-resistant strains harbored fewer inducible prophages (17/43) than fluoroquinolone-susceptible strains (49/70) (P = 0.0018). In addition, isolates of clones associated with fluoroquinolone resistance [CC156 (3/25); CC63 (2/20), and CC81 (1/19)], had lower frequency of functional prophages than isolates of clones with low incidence of fluoroquinolone resistance [CC30 (4/21), CC230 (5/20), CC62 (9/21), and CC180 (21/30)]. Likewise, persistent strains from patients with chronic respiratory diseases subjected to fluoroquinolone treatment had a low frequency of inducible prophages (1/11). Development of ciprofloxacin resistance was tested with two isogenic strains, one lysogenic and the other non-lysogenic: emergence of resistance was only observed in the non-lysogenic strain. These results are compatible with the lysis of lysogenic isolates receiving fluoroquinolones before the development of resistance and explain the inverse relation between presence of inducible prophages and fluoroquinolone-resistance. © 2014 López et al.


Aguirre-Lamban J.,Fundacion Jimenez Diaz | Aguirre-Lamban J.,ISCIII Institute Salud Carlos III | Riveiro-Alvarez R.,Fundacion Jimenez Diaz | Riveiro-Alvarez R.,ISCIII Institute Salud Carlos III | And 14 more authors.
Investigative Ophthalmology and Visual Science | Year: 2010

Purpose. Mutations in the ABCA4 gene have been associated with autosomal recessive Stargardt disease (STGD), a few cases of autosomal recessive cone-rod dystrophy (arCRD), and autosomal recessive retinitis pigmentosa (arRP). The purpose of this study was to compare high-resolution melting (HRM) analysis with denaturing high-performance liquid chromatography (dHPLC), to evaluate the efficiency of the different screening methodologies. Methods. Thirty-eight STGD, 15 arCRD, and 5 arRP unrelated Spanish patients who had been analyzed with the ABCR microarray were evaluated. The results were confirmed by direct sequencing. In patients with either no or only one mutant allele, ABCA4 was further analyzed by HRM and dHPLC. Haplotype analysis was also performed. Results. In a previous microarray analysis, 37 ABCA4 variants (37/116; 31.9%) were found. dHPLC and HRM scanning identified 18 different genotypes in 20 samples. Of the samples studied, 19/20 were identified correctly by HRM and 16/20 by dHPLC. One homozygous mutation was not detected by dHPLC; however, the p.Cys2137Tyr homozygote was distinguished from the wild-type by HRM technique. In the same way, one novel change in exon 5 (p.Arg187His) was found only by means of the HRM technique. In addition, dHPLC identified the mutation p.Trp1724Cys in one sample; however, HRM detected the mutation in two samples. Conclusions. ABCA4 should be analyzed by an optimal screening technique, to perform further characterization of pathologic alleles. The results seemed to show that HRM had better sensitivity and specificity than did dHPLC, with the advantage that some homozygous sequence alterations were identifiable. © Association for Research in Vision and Ophthalmology.

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