Evaluation of Different Phenotypic Techniques for the Detection of Slime Produced by Bacteria Isolated from Clinical Specimens

UNLABELLED INTRODUCTION : Microorganisms use various strategies for their survival in both the environment and in humans. Slime production by bacteria is one such mechanism by which microbes colonize on the indwelling prosthetic devices and form biofilms. Infections caused by such microorganisms are difficult to treat as the biofilm acts as a shield and protects microbes against antimicrobial agents. There are several methods for the detection of slime produced by bacteria, and they include both phenotypic and molecular methods. The present study evaluated the Congo red agar/broth method, Christensen's method, dye elution technique, and the latex agglutination method for the demonstration of slime production by different bacterial clinical isolates. MATERIALS & METHODS We collected 151 bacterial clinical isolates (both gram-positive and gram-negative bacteria) from various specimens and tested them for the production of slime both by qualitative and quantitative tests. Congo red agar/broth method, Christensen's method, dye elution technique, and latex agglutination methods were used for detecting the slime or slime-like substance. RESULTS : We found that 103 (68.2%) strains were positive for slime production by Congo red agar/broth method. It was found that 18 (94.7%) strains of Klebsiella pneumoniae, 21 (84.0%) strains of S aureus and 25 (65.7%) strains of coagulase-negative Staphylococci were positive for slime or slime-like substances by Congo red agar/broth method. A total of 41.0% of the strains positive by Christensen's method and 15.2% of the strains by dye elution technique were found to be more adherent organisms and that have the potential to form biofilms. Only the gram-positive organisms showed nonspecific agglutination with latex suspension. CONCLUSION : Among the various phenotypic methods compared in this study the Congo red agar/broth method is a simple, economical, sensitive, and specific method that can be used by clinical microbiology laboratories for screening the strains for the presence of slime or slime-like substances.