title: Phenotypic characterization of multidrug-resistant Pseudomonas aeruginosa strains isolated from pediatric patients associated to biofilm formation.
abstract: BACKGROUND
  Pseudomonas aeruginosa is an opportunistic pathogen that has acquired several mechanisms of resistance to multiple groups of antibiotic agents and has been widely employed as a model organism for the study of biofilm formation. Many P. aeruginosa structures embedded in the extracellular matrix, such as exopolysaccharides (EPS), flagella, and type-IV pili (T4P), have been associated with biofilm formation. In this study, we assess biofilm formation by crystal violet quantification in clinical strains of multidrug-resistant (MDR) P. aeruginosa isolated from the Hospital Infantil de México Federico Gómez (HIMFG) associated to total and reducing EPS production (quantification by the anthrone and DNS method, respectively), twitching motility activity by T4P, and flagellar-mediated motility.
  
  
  RESULTS
  The determination of Minimum Inhibitory Concentration (MIC) showed that >50% of P. aeruginosa strains were resistant to 12 different antibiotics (TIC, CAZ, CTX, CRO, FEP, AZT, GM, CIP, LEV, PZT, IMP, and MEM). Total and reducing EPS analysis of the 58 biofilm-forming MDR P. aeruginosa strains showed heterogeneous values ranging from OD600 9.06 to 212.33, displaying a linear correlation with the production of total EPS (59.66μg/ml to 6000.33μg/ml; R(2)=0.89), and a higher correlation with reducing EPS (88.33μg/ml to 1100.66μg/ml; R(2)=0.96). T4P twitching motility showed a moderated linear correlation (2.00mm to 28.33mm; R(2)=0.74). Even though it has been demonstrated that flagella contribute to the initial stages of biofilm formation, crystal violet analysis showed a moderate correlation (R(2)=0.49) with flagellar-mediated motility in MDR P. aeruginosa under the tested conditions. In addition, PFGE profiles revealed two subgroups generating profiles group A, consisting of 89.63% (52/58) of the strains, and group B, consisting of 13.09% (6/58) of the strains.
  
  
  CONCLUSIONS
  Phenotypic analysis showed a correlation among the biofilms developed in the MDR P. aeruginosa strains with EPS (total and reducing) production, T4P-activity by twitching motility and flagellar-mediated motility.
authors.affiliation: Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Hemato-Onocología e Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: Sara A
authors.initials: SA
authors.lastname: Ochoa
authors.affiliation: Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Hemato-Onocología e Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: Ariadnna
authors.initials: A
authors.lastname: Cruz-Córdova
authors.affiliation: Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Hemato-Onocología e Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: Gerardo E
authors.initials: GE
authors.lastname: Rodea
authors.affiliation: Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Hemato-Onocología e Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: Vicenta
authors.initials: V
authors.lastname: Cázares-Domínguez
authors.affiliation: Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Hemato-Onocología e Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Escalona
authors.affiliation: Laboratorio de Infectología, Departamento de Infectología. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: José
authors.initials: J
authors.lastname: Arellano-Galindo
authors.affiliation: Departamento de Ecología de Agentes Patógenos, Hospital General "Dr. Manuel Gea González", Tlalpan, México, D.F. 14080, Mexico.
authors.forename: Rigoberto
authors.initials: R
authors.lastname: Hernández-Castro
authors.affiliation: Dirección de Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Reyes-López
authors.affiliation: Laboratorio de Investigación en Bacteriología Intestinal, Unidad de Hemato-Onocología e Investigación. Hospital Infantil de México Federico Gómez, Dr. Márquez 162, Col. Doctores, Delegación Cuauhtémoc, México, D.F. 06720, Mexico. Electronic address: juanxico@yahoo.com.
authors.forename: Juan
authors.initials: J
authors.lastname: Xicohtencatl-Cortes
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018441:Biofilms / Q000254:growth & development*; D024901:Drug Resistance, Multiple, Bacterial; D006761:Hospitals; D006801:Humans; D008124:Locomotion; D008800:Mexico; D008826:Microbial Sensitivity Tests; D011135:Polysaccharides, Bacterial / Q000378:metabolism; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology*
chemical_list: D000900:Anti-Bacterial Agents; D011135:Polysaccharides, Bacterial
keywords: Biofilm; Multidrug-resistant; Pseudomonas aeruginosa; Type IV pili