<p>Investigation of six plasmid-mediated quinolone resistance genes among clinical isolates of pseudomonas: a genotypic study in Saudi Arabia</p>

Inappropriate use of antibiotics in clinical settings is thought to have led to the global emergence and spread of multidrug-resistant pathogens. The goal of this study was to investigate the prevalence of genes encoding aminoglycoside resistance and plasmid-mediated quinolone resistance among clinical isolates of Klebsiella pneumoniae. All K. pneumoniae isolates were phenotypically identified using API 20E and then confirmed genotypically through amplification of the specific K. pneumoniae phoE gene. All isolates were genotyped by the enterobacterial repetitive intergenic consensus polymerase chain reaction technique (ERIC-PCR). Antibiotic susceptibility testing was done by a modified Kirby-Bauer method and broth microdilution. All resistant or intermediate-resistant isolates to either gentamicin or amikacin were screened for 7 different genes encoding aminoglycoside-modifying enzymes (AMEs). In addition, all resistant or intermediate-resistant isolates to either ciprofloxacin or levofloxacin were screened for 5 genes encoding the quinolone resistance protein (Qnr), 1 gene encoding quinolone-modifying enzyme, and 3 genes encoding quinolone efflux pumps. Biotyping using API 20E revealed 13 different biotypes. Genotyping demonstrated that all isolates were related to 2 main phylogenetic groups. Susceptibility testing revealed that carbapenems and tigecycline were the most effective agents. Investigation of genes encoding AMEs revealed that acc(6′)-Ib was the most prevalent, followed by acc(3′)-II, aph(3′)-IV, and ant(3′′)-I. Examination of genes encoding Qnr proteins demonstrated that qnrB was the most prevalent, followed by qnrS, qnrD, and qnrC. It was found that 61%, 26%, and 12% of quinolone-resistant K. pneumoniae isolates harbored acc(6′)-Ib-cr, oqxAB, and qebA, respectively. The current study demonstrated a high prevalence of aminoglycoside and quinolone resistance genes among clinical isolates of K. pneumoniae.

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Citrobacter spp. as a Source ofqnrBAlleles

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.05187-11 ◽

2011 ◽

Vol 55 (11) ◽

pp. 4979-4984 ◽

Cited By ~ 61

Author(s):

George A. Jacoby ◽

Caitlin M. Griffin ◽

David C. Hooper

Keyword(s):

16S Rrna ◽

Resistance Genes ◽

Quinolone Resistance ◽

Clinical Isolates ◽

Citrobacter Freundii ◽

Rrna Sequence ◽

16S Rrna Sequence ◽

Allelic Variants ◽

Content Type

ABSTRACTqnrBis the most common of the fiveqnrfamilies and has the greatest number of allelic variants. Almost two-thirds of theqnrBalleles have been reported inCitrobacterspp., and several were shown to be located on the chromosome. In this study, PCR was used to investigate the prevalence of plasmid-mediated quinolone resistance genes in 71 clinical isolates belonging to theCitrobacter freundiicomplex. Thirty-seven percent containedqnrBalleles, including 7 (qnrB32 to qnrB38) that were novel and 1 pseudogene, while none containedqnrA,qnrC,qnrD,qnrS, oraac(6′)-Ib-cr. When the strains were arrayed by related 16S rRNA sequence and further separated into subspecies by biochemical criteria, clustering ofqnrB-positive strains was evident. In only two strains withqnrB2andqnrB4was quinolone resistance transferable by conjugation, and only these strains contained the ISCR1sequence that is often associated withqnrBon plasmids. Five of 26qnrB-positive strains contained integrase genes, but these included the strains withqnrB2andqnrB4as well as two strains with other transmissible plasmids. In a fully sequenced genome ofCitrobacter youngae, a member of theC. freundiicomplex, another novelqnrBallele,qnrB39, occurs in a sequence of genes that is 90% identical to sequence surrounding integron-associatedqnrB4incorporated into plasmids. The chromosome ofCitrobacteris the likely source of plasmid-mediatedqnrB.

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