title: Microbial interaction between a CTXM-15 -producing Escherichia coli and a susceptible Pseudomonas aeruginosa isolated from bronchoalveolar lavage: influence of cefotaxime in the dual-species biofilm formation.
abstract: Two isolates, Escherichia coli ella00 and Pseudomonas aeruginosa ella01, obtained from bronchoalveolar lavage, were found to be closely associated in clusters in agar medium. Escherichia coli ella00 was multidrug resistant and CTXM-15 extended-spectrum β-lactamase producer, while P. aeruginosa ella01 was susceptible to all antimicrobials tested. These observations impelled for further studies aimed to understand their microbial interaction. The P. aeruginosa ella01 biofilm-forming capacity was reduced and not affected when it was co-cultured with E. coli ella00 and E. coli ATCC 25922 respectively. Interestingly, the co-culture of ella isolates in the presence of high concentrations, such as 160 μg ml(-1) , of cefotaxime allowed the formation of more biofilm than in the absence of the antibiotic. As revealed by fluorescence in situ hybridization, in co-culture, P. aeruginosa ella01 survived and subsequently flourished when exposed to this third-generation cephalosporin at a concentration 10 × higher than its minimum inhibitory concentration (MIC), and this was mostly due to β-lactamases production by E. coli ella00. In fact, it was demonstrated by high-performance liquid chromatography that cefotaxime was absent for the culture medium 4 h after application. In conclusion, we demonstrate that bacterial species can interact differently depending on the surrounding conditions (favourable or stressing), and that those interactions can switch from unprofitable to beneficial.
authors.affiliation: Departmento de Produção Aquática, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.|Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Universidade do Porto, Porto, Portugal.
authors.forename: Lucinda J
authors.initials: LJ
authors.lastname: Bessa
authors.affiliation: Departmento de Produção Aquática, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.
authors.forename: Ângelo
authors.initials: Â
authors.lastname: Mendes
authors.affiliation: +ani+ Clínica Veterinária, Maia, Portugal.
authors.forename: Rita
authors.initials: R
authors.lastname: Gomes
authors.affiliation: +ani+ Clínica Veterinária, Maia, Portugal.
authors.forename: Sara
authors.initials: S
authors.lastname: Curvelo
authors.affiliation: Centro de Química Medicinal da Universidade do Porto (CEQUIMED-UP), Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
authors.forename: Sara
authors.initials: S
authors.lastname: Cravo
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Universidade do Porto, Porto, Portugal.|Centro de Química Medicinal da Universidade do Porto (CEQUIMED-UP), Laboratório de Química Orgânica e Farmacêutica, Departamento de Ciências Químicas, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal.
authors.forename: Emília
authors.initials: E
authors.lastname: Sousa
authors.affiliation: Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Universidade do Porto, Porto, Portugal.|Departmento de Biologia, Faculdade de Ciências, Universidade do Porto, Porto, Portugal.
authors.forename: Vitor
authors.initials: V
authors.lastname: Vasconcelos
authors.affiliation: Departmento de Produção Aquática, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.|Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), Universidade do Porto, Porto, Portugal.
authors.forename: Paulo
authors.initials: P
authors.lastname: Martins da Costa
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D002439:Cefotaxime / Q000494:pharmacology*; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000302:isolation & purification / Q000502:physiology*; D056265:Microbial Interactions; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases; D002439:Cefotaxime