title: The95ΔG mutation in the 5'untranslated region of the norA gene increases efflux activity in Staphylococcus epidermidis isolates.
abstract: In the Staphylococcus aureus ATCC25923 strain, the flqB mutation in the 5'untranslated region (5'UTR) of the norA gene causes increased norA mRNA expression and high efflux activity (HEA). The involvement of the norA gene 5'UTR in HEA has not been explored in S. epidermidis; therefore, we examined the function of this region in S. epidermidis clinical isolates. The selection of isolates with HEA was performed based on ethidium bromide (EtBr) MIC values and efflux efficiency (EF) using the semi-automated fluorometric method. The function of the 5'UTR was studied by quantifying the levels of norA expression (RT-qPCR) and by identifying 5'UTR mutations by sequence analysis. Only 10 isolates from a total of 165 (6.1%) had HEA (EtBr MIC = 300 μg/ml and EF ranged from 48.4 to 97.2%). Eight of 10 isolates with HEA had the 5'UTR95ΔG mutation. Isolates carrying the95ΔG mutation had higher levels of norA expression compared with those that did not. To corroborate that the95ΔG mutation is involved in HEA, a strain adapted to EtBr was obtained in vitro. This strain also presented the95ΔG mutation and had a high level of norA expression and EF, indicating that the95ΔG mutation is important for the HEA phenotype. The95ΔG mutation produces a different structure in the Shine-Dalgarno region, which may promote better translation of norA mRNA. To our knowledge, this is the first report to demonstrate the participation of the 5'UTR95ΔG mutation of the norA gene in the HEA phenotype of S. epidermidis isolates. Here, we propose that the efflux of EtBr is caused by an increment in the transcription and/or translation of the norA gene.
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: García-Gómez
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico.
authors.forename: Marcos E
authors.initials: ME
authors.lastname: Jaso-Vera
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Juárez-Verdayes
authors.affiliation: Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, Mexico.
authors.forename: María D
authors.initials: MD
authors.lastname: Alcántar-Curiel
authors.affiliation: Instituto de Oftalmología Fundación Conde de Valenciana, Ciudad de México, Mexico.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Zenteno
authors.affiliation: Área Académica de Nutrición, Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Betanzos-Cabrera
authors.affiliation: Programa de Genómica Funcional de Procariotes, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.
authors.forename: Humberto
authors.initials: H
authors.lastname: Peralta
authors.affiliation: Departamento de Inmunología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico.
authors.forename: Sandra
authors.initials: S
authors.lastname: Rodríguez-Martínez
authors.affiliation: Departamento de Inmunología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico.
authors.forename: Mario E
authors.initials: ME
authors.lastname: Cancino-Díaz
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico.
authors.forename: Janet
authors.initials: J
authors.lastname: Jan-Roblero
authors.affiliation: Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas-Instituto Politécnico Nacional, Ciudad de México, Mexico. Electronic address: jccancinodiaz@hotmail.com.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Cancino-Diaz
mesh_terms: D020121:5' Untranslated Regions; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D018441:Biofilms; D019008:Drug Resistance, Neoplasm; D015870:Gene Expression; D005838:Genotype; D006801:Humans; D008826:Microbial Sensitivity Tests; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics* / Q000378:metabolism*; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D013203:Staphylococcal Infections / Q000382:microbiology; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity
chemical_list: D020121:5' Untranslated Regions; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; C075040:NorA protein, Staphylococcus
keywords: 5′UTR; Efflux; Mutation; NorA; Shine-Dalgarno; Staphylococcus epidermidis