title: Structural changes and differentially expressed genes in Pseudomonas aeruginosa exposed to meropenem-ciprofloxacin combination.
abstract: The effect of a meropenem-ciprofloxacin combination (MCC) on the susceptibility of multidrug-resistant (MDR) Pseudomonas aeruginosa (MRPA) clinical isolates was determined using checkerboard and time-kill curve techniques. Structural changes and differential gene expression that resulted from the synergistic action of the MCC against one of the P. aeruginosa isolates (1071-MRPA]) were evaluated using electron microscopy and representational difference analysis (RDA), respectively. The differentially expressed, SOS response-associated, and resistance-associated genes in 1071-MRPA exposed to meropenem, ciprofloxacin, and the MCC were monitored by quantitative PCR. The MCC was synergistic against 25% and 40.6% of MDR P. aeruginosa isolates as shown by the checkerboard and time-kill curves, respectively. The morphological and structural changes that resulted from the synergistic action of the MCC against 1071-MRPA were a summation of the effects observed with each antimicrobial alone. One exception included outer membrane vesicles, which were seen in a greater amount upon ciprofloxacin exposure but were significantly inhibited upon MCC exposure. Cell wall- and DNA repair-associated genes were differentially expressed in 1071-MRPA exposed to meropenem, ciprofloxacin, and the MCC. However, some of the RDA-detected, resistance-associated, and SOS response-associated genes were expressed at significantly lower levels in 1071-MRPA exposed to the MCC. The MCC may be an alternative for the treatment of MDR P. aeruginosa. The effect of this antimicrobial combination may be not only the result of a summation of the effects of meropenem and ciprofloxacin but also a result of differential action that likely inhibits protective mechanisms in the bacteria.
authors.affiliation: Postgraduate Program in Pharmaceutical Sciences, State University of Maringa, Maringá, Paraná, Brazil Department of Clinical Analysis and Biomedicine, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Vera Lúcia Dias
authors.initials: VL
authors.lastname: Siqueira
authors.affiliation: Department of Clinical Analysis and Biomedicine, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Rosilene Fressatti
authors.initials: RF
authors.lastname: Cardoso
authors.affiliation: Department of Clinical Analysis and Biomedicine, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Katiany Rizzieri
authors.initials: KR
authors.lastname: Caleffi-Ferracioli
authors.affiliation: Department of Clinical Analysis and Biomedicine, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Regiane Bertin de Lima
authors.initials: RB
authors.lastname: Scodro
authors.affiliation: Department of Cellular Biology and Genetics, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Maria Aparecida
authors.initials: MA
authors.lastname: Fernandez
authors.affiliation: Department of Clinical Analysis and Biomedicine, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Adriana
authors.initials: A
authors.lastname: Fiorini
authors.affiliation: Postgraduate Program in Pharmaceutical Sciences, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Tania
authors.initials: T
authors.lastname: Ueda-Nakamura
authors.affiliation: Postgraduate Program in Pharmaceutical Sciences, State University of Maringa, Maringá, Paraná, Brazil.
authors.forename: Benedito Prado
authors.initials: BP
authors.lastname: Dias-Filho
authors.affiliation: Postgraduate Program in Pharmaceutical Sciences, State University of Maringa, Maringá, Paraná, Brazil cvnakamura@uem.br.
authors.forename: Celso Vataru
authors.initials: CV
authors.lastname: Nakamura
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001938:Brazil; D002939:Ciprofloxacin / Q000494:pharmacology*; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D004338:Drug Combinations; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial / Q000187:drug effects*; D006801:Humans; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D016133:Polymerase Chain Reaction; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000235:genetics* / Q000648:ultrastructure; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D013845:Thienamycins / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D004338:Drug Combinations; D012329:RNA, Bacterial; D013845:Thienamycins; D002939:Ciprofloxacin; D000077731:Meropenem