title: Differential distribution of plasmid-mediated quinolone resistance genes in clinical enterobacteria with unusual phenotypes of quinolone susceptibility from Argentina.
abstract: We studied a collection of 105 clinical enterobacteria with unusual phenotypes of quinolone susceptibility to analyze the occurrence of plasmid-mediated quinolone resistance (PMQR) and oqx genes and their implications for quinolone susceptibility. The oqxA and oqxB genes were found in 31/34 (91%) Klebsiella pneumoniae and 1/3 Klebsiella oxytoca isolates. However, the oqxA- and oqxB-harboring isolates lacking other known quinolone resistance determinants showed wide ranges of susceptibility to nalidixic acid and ciprofloxacin. Sixty of the 105 isolates (57%) harbored at least one PMQR gene [qnrB19, qnrB10, qnrB2, qnrB1, qnrS1, or aac(6')-Ib-cr)], belong to 8 enterobacterial species, and were disseminated throughout the country, and most of them were categorized as susceptible by the current clinical quinolone susceptibility breakpoints. We developed a disk diffusion-based method to improve the phenotypic detection of aac(6')-Ib-cr. The most common PMQR genes in our collection [qnrB19, qnrB10, and aac(6')-Ib-cr] were differentially distributed among enterobacterial species, and two different epidemiological settings were evident. First, the species associated with community-acquired infections (Salmonella spp. and Escherichia coli) mainly harbored qnrB19 (a unique PMQR gene) located in small ColE1-type plasmids that might constitute its natural reservoirs. qnrB19 was not associated with an extended-spectrum β-lactamase phenotype. Second, the species associated with hospital-acquired infections (Enterobacter spp., Klebsiella spp., and Serratia marcescens) mainly harbored qnrB10 in ISCR1-containing class 1 integrons that may also have aac(6')-Ib-cr as a cassette within the variable region. These two PMQR genes were strongly associated with an extended-spectrum β-lactamase phenotype. Therefore, this differential distribution of PMQR genes is strongly influenced by their linkage or lack of linkage to integrons.
authors.affiliation: Servicio Antimicrobianos, Departamento de Bacteriología, Instituto Nacional de Enfermedades Infecciosas-ANLIS Dr. Carlos G. Malbrán, Buenos Aires, Argentina.
authors.forename: Patricia
authors.initials: P
authors.lastname: Andres
authors.forename: Celeste
authors.initials: C
authors.lastname: Lucero
authors.forename: Alfonso
authors.initials: A
authors.lastname: Soler-Bistué
authors.forename: Leonor
authors.initials: L
authors.lastname: Guerriero
authors.forename: Ezequiel
authors.initials: E
authors.lastname: Albornoz
authors.forename: Tung
authors.initials: T
authors.lastname: Tran
authors.forename: Angeles
authors.initials: A
authors.lastname: Zorreguieta
authors.forename: Marcelo
authors.initials: M
authors.lastname: Galas
authors.forename: Alejandra
authors.initials: A
authors.lastname: Corso
authors.forename: Marcelo E
authors.initials: ME
authors.lastname: Tolmasky
authors.forename: Alejandro
authors.initials: A
authors.lastname: Petroni
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001118:Argentina; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004755:Enterobacteriaceae / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D006801:Humans; D032023:Integrons / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010641:Phenotype; D010957:Plasmids / Q000235:genetics*; D015363:Quinolones / Q000494:pharmacology*; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015363:Quinolones