Glutaraldehyde exposed Pseudomonas fluorescens: a case of biofilm persistence?

Abstract

From the assessment of the recovery capability of pseudomonas fluorescens atcc 13525t after exposure to several glutaraldehyde (gta) concentrations (100, 200 and 400 mg/l) and exposure times (1 and 2 hours), it was found that, for gta concentrations above 100 mg/l, whatever the exposure time, bacterial cells presented different growth patterns in solid media. after this statement, the recovered cells were initially characterized using api ne20 strips and species identification was obtained using the api database. the type culture and the cells obtained after treatment with concentrations below 200 mg/l were identified as p. fluorescens. conversely, the identification of cells exposed to higher concentrations of gta failed. the electrophoretic profiles of both the type culture and the cells exposed to gta were obtained by pcr, using the primer t3b. the results showed identical profiles for the type culture and the cells exposed to low gta concentrations, and a totally different pattern for cells exposed to gta concentrations above 200 mg/l. sequencing of the 16s rdna gene is under way in order to further clarify the differences observed. the p. fluorescens atcc 13525 (used as control) and the cells treated with 200 mg/l of gta during 2 hours were selected for further studies. a comparative study was carried out between the above referred cells in terms of morphological structure, surface properties, respiratory activity, biofilm formation ability and susceptibility to gta. the results showed that the cells treated with 200 mg/l of gta presented an elongated structure, were about 30 times less active in terms of respiratory activity and were more hydrophilic. concerning biofilm formation, both tested cells presented biofilm formation ability, but the gta treated cells produced about 2 times more mass of biofilm. however, this biofilm had a specific respiratory activity 3 times less than the one formed by the control culture. the biofilm behaviour immediately after exposure to 200 mg/l of gta during 2 hours, was similar for both situations studied, since a low biofilm removal and inactivation was achieved. however, 7 hours after gta exposure, only 55% of the biofilm formed by the control culture remained attached to the surface, while for the biofilms formed by the treated cells all the deposit remained attached to the surface. the results obtained in this work indicate that cells submitted to gta treatment may give rise to biofilms harder to remove and consequently more persistent, than non-treated cells. therefore, care must be taken in the selection and application of biocides in industrial biofilms.