title: Differences in biofilm formation and aggregative adherence between beta-lactam susceptible and beta-lactamases producing P. mirabilis clinical isolates.
abstract: Biofilm formation of multidrug resistant (MDR) extended-spectrum beta-lactamase (ESbetaL) producing Proteus mirabilis isolates from a long-term care and rehabilitation facility (LTCRF) in Northern Italy was evaluated. A total of 10 strains, 4/10 producing the acquired AmpC beta-lactamase CMY-16, 3/10 producing the ESbetaL TEM-92 and the remaining negative for the presence of beta-lactamase genes, were studied using standard adherence assays on titer plates. Tests were performed in three different media, including Luria Bertani (LB), LB diluted and urine. Three representative strains were also tested for biofilm production in microtiter in presence of beta-lactam sub-MIC concentrations. The same isolates were screened for aggregative adherence onto monkey kidney cells (LLC-MK2). All strains studied were capable of biofilm formation, though at different levels. The beta-lactamase positive strains were statistically better significant in biofilm formation than negative ones regardless of growth medium. Cellular adherence assays showed a preferential ability of all isolates, regardless of beta-lactamase production, to adhere to inert surfaces rather than to cells. Although the results did not fully support a direct correlation between beta-lactamase production and biofilm formation, both mechanisms can greatly contribute to bacterial persistence in the urinary tract.
authors.affiliation: Department of Morphological, Eidological and Clinical Sciences, Section of Microbiology, University of Pavia, Pavia, Italy. elicleo@libero.it
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Nucleo
authors.forename: Giulia
authors.initials: G
authors.lastname: Fugazza
authors.forename: Roberta
authors.initials: R
authors.lastname: Migliavacca
authors.forename: Melissa
authors.initials: M
authors.lastname: Spalla
authors.forename: Mario
authors.initials: M
authors.lastname: Comelli
authors.forename: Laura
authors.initials: L
authors.lastname: Pagani
authors.forename: Maurizia
authors.initials: M
authors.lastname: Debiaggi
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects; D002460:Cell Line; D024881:Drug Resistance, Bacterial; D000882:Haplorhini; D006801:Humans; D008826:Microbial Sensitivity Tests; D011512:Proteus Infections / Q000382:microbiology*; D011513:Proteus mirabilis / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases