Detection of Biofilm formation in device associated clinical bacterial isolates in cancer patients

Abstract

Introduction : Biofilm is a community of bacteria that are attached to a substratum or surface. Bacteria in biofilm are embedded in extracellular polymeric matrix produced by the bacteria. Biofilm formation on indwelling medical devices such as catheters poses a critical medical problem. Both Gram-negative and Gram-positive bacteria can form biofilms on indwelling medical devices. Objectives : To determine the potential relationship between colonization of different medical devices by various clinical bacterial isolates and to determine the differences in biofilm formation in different conditions and to determine the minimum time and conditions necessary for the development of a homogenous and mature biofilm layer. Method : The study sample consisted of 50 clinical strains isolated from different medical devices and another 50 strains (control group) isolated from swabs taken from peripheral and central catheter insertion sites. All isolates were characterized to species level using commercial identification cards (GN ID,GP ID; Biomerieux, France) on an automated ID AST system . Biofilm formation and quantification of activity was assessed using a microtitre plate assay Results : Of the 50 clinical isolates, 42 were biofilm producers and 5 of the 50 surface swab isolates were weak biofilm producers. Of the 42 clinical isolates which produced biofilms, 24 were strong producers, 15 were moderate and 3 were weak producers. Catheter blood yielded the highest number (19/50) of biofilm producers. Acinetobacter spp. (15/50), Klebsiella pneumoniae (11/50), Pseudomonas aeruginosa (8/50), Staphylococcus spp. (7/50), and E . coli (6/50) the most common isolates. Twenty hours incubation time was found to be optimum for detection of biofilms produced by bacteria. Concentration of glucose also played an important role in formation of biofilm with more biofilm formation in 0.25% glucose in tryptic soya broth. Conclusion: The current study shows that biofilm producing Gram negative bacilli are present in vascular catheters. Methods that detect and quantify biofilms on the inner (luminal) as well as outer surfaces of catheters will provide the only true picture of biofilm colonization.