Inquilinus limosus: Biofilm Formation in Presence of Sub-minimal Inhibitory Concentration of Antibiotics.

PINO MARYLÚ; BARONI MARÍA ROSA; MENEGHETTI FERNANDO; GUTKIND GABRIEL; DI CONZA JOSÉ

Washington

Conferencia; 54th ICAAC - Annual Interscience Conference on Antimicrobial Agents and Chemotherapy; 2014

American Society of Microbiology

Background: Infections by Inquilinus limosus are increasingly reported in cystic fibrosis patients (CFPs). As the ability to form biofilm (BF) could contribute to a refractory state for antibiotic treatment, our aim was to analyze the in vitro BF formation of both mucoid and non-mucoid clinical isolates of I. limosus exposed to sub-minimal inhibitory concentration (sub-MIC) of different antibiotics. Methods: Both mucoid and non-mucoid Inquilinus limosus were isolated from the same sputum specimen obtained from a CFP in 2013. The patient was chronically colonized by a mucoid I. limosus. MICs were performed according to the CLSI procedures with few modifications. Clonality analysis was performed by SpeI and XbaI-PFGE. BF formation was evaluated by microtiter plate assays in the absence and in the presence of sub-MIC of colistin (COL), tobramycin (TOB) and imipenem (IMP) (512, 512, 0.12 mg/L, respectively), by staining with crystal violet and extraction with ethanol. BF was subsequently assessed by measuring the optical density at 540 nm. Statistical differences were assessed by analysis of variance followed by Tukey´s test. Results: Both isolates displayed the same antibiotic resistance pattern, showing identical MIC values for COL, TOB and IMI (>1024, >1024, 0.25 mg/L, respectively). Pulsotypes were indistinguishable. In absence of antibiotic, amounts of BFs formed by the non-mucoid isolate were much higher (3.5-fold) than in the mucoid counterpart. BF in the latter could also be induced by the presence of sub-MIC of COL and TOB (P