title: Adaptive response of single and binary Pseudomonas aeruginosa and Escherichia coli biofilms to benzalkonium chloride.
abstract: The main goal of this work was to examine whether the continuous exposure of single and binary P. aeruginosa and E. coli biofilms to sub-lethal benzalkonium chloride (BC) doses can induce adaptive response of bacteria. Biofilms were formed during 24 h and then put continuously in contact with BC for more 5 days. The six-day-old adapted biofilms were then submitted to BC challenge, characterized and inspected by SEM. Both single and binary adapted biofilms have clearly more biomass, polysaccharides and proteins and less activity even though the number of cells was identical. After BC treatment, adapted biofilms maintained their mass and activity. SEM examination revealed that those adapted biofilms had a slimier and denser matrix that became thicker after BC treatment. Continuous exposure of bacteria to antimicrobials can lead to development of biofilms encompassing more virulent and tolerant bacteria. This adaptive resistance can be the result of a phenotypic adaptation, a genetic acquired resistance or both. Instead of eradicating biofilms and kill microorganisms, the use of a disinfectant can, favour biofilm formation and tolerance. This must be a genuine concern as it can happen in clinical environments, where the use of antimicrobials is unavoidable.
authors.affiliation: IBB-Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
authors.forename: Idalina
authors.initials: I
authors.lastname: Machado
authors.forename: Susana Patrícia
authors.initials: SP
authors.lastname: Lopes
authors.forename: Ana Margarida
authors.initials: AM
authors.lastname: Sousa
authors.forename: Maria Olívia
authors.initials: MO
authors.lastname: Pereira
mesh_terms: D000220:Adaptation, Biological; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001548:Benzalkonium Compounds / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D024881:Drug Resistance, Bacterial / Q000187:drug effects / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000502:physiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000502:physiology
chemical_list: D000891:Anti-Infective Agents, Local; D001548:Benzalkonium Compounds