|LETTER TO EDITOR
|Year : 2012 | Volume
| Issue : 1 | Page : 46-47
Detection of biofilm formation in bacteria from cases of urinary tract infections, septicemia, skin and soft tissue infections and post-operative infections by Congo Red Agar method
Anuradha De, Dhanashree Deshpande, Sujata M Baveja, Shripad Taklikar
Department of Microbiology, L. T. M. Medical College, Sion, Mumbai, Maharashtra, India
|Date of Web Publication||3-Dec-2012|
Department of Microbiology, L. T. M. Medical College, Sion, Mumbai - 400 022, Maharashtra
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
De A, Deshpande D, Baveja SM, Taklikar S. Detection of biofilm formation in bacteria from cases of urinary tract infections, septicemia, skin and soft tissue infections and post-operative infections by Congo Red Agar method. J Acad Med Sci 2012;2:46-7
|How to cite this URL:|
De A, Deshpande D, Baveja SM, Taklikar S. Detection of biofilm formation in bacteria from cases of urinary tract infections, septicemia, skin and soft tissue infections and post-operative infections by Congo Red Agar method. J Acad Med Sci [serial online] 2012 [cited 2020 Jan 25];2:46-7. Available from: http://www.e-jams.org/text.asp?2012/2/1/46/104017
Biofilms are a group of microorganisms attached to a surface and covered by an exopolysaccharide matrix of microbial and host origin.  Bacteria growing in a biofilm are usually associated with severe human diseases which are far more difficult to eradicate.  According to National Institute of Health, more than 60% of all microbial infections are caused by biofilms.  Formation of biofilms by Gram-negative bacilli and staphylococci have been reported worldwide. , Various screening methods for detection of biofilm production include Congo red agar (CRA) method, Tube method (TM), and Tissue Culture Plate (TCP) method. 
A study was undertaken to find out the incidence of biofilm formation in bacteria recovered from cases of urinary tract infections (UTIs), septicemia, skin and soft tissue infections (SSTIs), and post-operative infections.
A total of 150 clinical isolates from patients admitted in this tertiary care hospital during August to October 2011 was included, of which 66 were from cases of UTIs, 34 from cases of septicemia, 35 from cases of SSTIs, and 15 from post-op. infections. All the isolates were identified by standard biochemical tests. Detection of in vitro biofilm formation was done by Congo red agar (CRA) method, a simple qualitative method described by Freeman et al., using Brain heart infusion broth supplemented with sucrose and Congo red stain.  It was performed in duplicate and repeated twice for all isolates. A positive result was indicated by black colonies with a dry crystalline consistency [Figure 1].
|Figure 1: Left top and bottom are biofilm producers; right top and bottom are negative for biofilm formation|
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Overall biofilm production was seen in 50.67% (76/150) bacteria. Biofilm was mainly produced by 63.63% (42/66) bacteria from cases of UTIs, followed by 57.14% (20/35) in SSTIs, 38.23% (13/34) in cases of septicemia, and only 6.67% (1/15) in cases of post-op. infections.
The major biofilm producing bacteria in UTIs was Escherichia coli (52.18%), followed by Klebsiella pneumoniae (23.91%), Proteus species (13.04%), and Enterococcus species (10.87%). In SSTIs, biofilm production was maximum in Methicillin Sensitive Staphylococcus aureus (MSSA) (50%), followed by MRSA (15%). From cases of septicemia, biofilm production was more prevalent in MRSA (38.46%), followed by E. coli and K. pneumoniae (15.39% each). In post-op. infections, only one MSSA was biofilm positive. [Table 1] shows number of bacteria tested for biofilm production from all specimens and number positive. Maximum biofilm formation was seen among urinary isolates in this study showing its significance in urinary tract infections. Least was seen in post-operative infections. Hassan et al. have considered TCP a reliable method and the gold standard for biofilm detection and said that though specificity of the CRA method is comparable with TM and TCP methods, sensitivity of the CRA method is very less (11%) as compared to the TM method (73%). 
|Table 1: Bacteria tested for biofilm formation from all specimens and number positive|
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As biofilm formation has an important role in pathogenicity of infections, its detection should be mandatory in a laboratory set up. TCP method is an accurate and reproducible screening method for biofilm production. The CRA method has disadvantage of subjective evaluation but it is one of the simple, cost-effective phenotypic methods for screening biofilm formation and does not require technical expertise. All isolates can be tested by the other two methods also, which will definitely improve the sensitivity of the study.
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