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Indian Journal of Medical Microbiology, Vol. 24, No. 4, October-December, 2006, pp. 303 Correspondence Detection of biofilm Maiti PK Department of Microbiology, Institute of Postgraduate Medical Education and Research, Kolkata -700 020 Date of Submission: 30-Apr-2006 Code Number: mb06091 Dear Editor, With great interest I went through the article of Mathur and his co-workers regarding detection of biofilm formation.[1] Probably the methods applied in this study are better indicator of bacterial adhesion, not the potentiality for their biofilm formation. Initial adherence of most S. epidermidis strains to plastic surface is mostly mediated by a capsular polysaccharide adhesion called PS/A and subsequent adhesion between cells is mediated by polysaccharide intercellular adhesion or PIA, which is structurally different to that of PS/A and forms the polysaccharide matrix of biofilm.[2] Slime or glycocalyx forms matrix surrounding each of the individual cells as its outermost component. However, exopolysaccarides of biofilms are produced under selective pressures and give biofilms structural complexities which are controlled by diffusible chemical signals as the collective effort (quorum sensing) of the cells within biofilms. Therefore, presence within biofilm at micro level is not homogenous.[3] Extent of initial adhesion may also differ with adherence property of container, duration and number of bacteria coming in contact with test surface as well as with the fluid turbulence of test media. Consequently, the results of the tests to detect slime production by tissue culture plate method and tube method can only be compared when both types of test containers will be made up of same material and when composition of media, initial bacterial concentration and incubation period will be identical. Probably results after 24 hours of incubation will represent only initial adhesion of bacteria to the test surface which may include some strains of non-biofilm producers. Because all biofilm formation starts with surface adhesion, the screening tests only reliably detect non-biofilm producers which also fail to produce slime. References
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