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Indian Journal of Medical Microbiology, Vol. 24, No. 4, October-December, 2006, pp. 303-304 Correspondence Author's reply Mathur Tarun Department of Infectious Diseases, Ranbaxy Research Laboratories, Gurgaon - 122001, Haryana Date of Submission: 22-May-2006 Code Number: mb06092 Related Article: mb06091 Dear Editor, It was nice the views of Prof. P.K. Maiti about our paper.[1] The objective of our study was to differentiate between biofilm producer and non-producer clinical strains of staphylococci by tissue culture plate (TCP) tube and Congo red agar methods described previously for detection of biofilm formation among staphylococci. Staphylococcus epidermidis and Staphylococcus aureus are the most important pathogen in foreign body-related infections. The pathogenic mechanism by which they adhere to prosthetic devices and elaborate is now termed, as biofilm is increasingly understood. Identification of biofilm producing phenotype might help to elucidate the impact of staphylococci in diagnosis of infections related to biomedical devices. These biofilm producing phenotype excrete an adherent cover glycocalyx or "slime", which allows ′planktonic" -unattached individual cells, to adhere to surfaces followed by cell-cell adhesion and accumulation of multilayered cell cluster surrounded by slimy cover termed as biofilms. This later part is mediated by polysaccharide intercellular adhesion (PIA), which is composed of partially N-acetylated linear β -1, 6-linked glucosaminoglycans and product of intracellular adhesion (ica) locus, icaADBC and one regulatory gene (icar). Slime contribures the bulk of the volume of a biofilm and is primarily responsible for its slimy macroscopic properties. Detection of staphylococci with slimes is indicative of infected devices due to colonization by biofilm producing staphylococcal isolates. In numerous in vitro studies related to adherence and biofilm formation by staphylococci was demonstrated on catheter disc, PVC tube, membranes, tissue culture plates, glass slide and glass beads, even when incubated for shorter incubation periods of 12-24 hours. These studies clearly indicated that biofilm formation is a continuous process and can be iniated as soon as the bacteria come in contact with foreign material. By both TCP and tube method only adherent cells of staphylococci covered with slime were deeply stained with crystal violet indicated the concentration of bacterial biofilms on the surface. In our study, there were strain and media preparation variability of slime production in the presence of other carbohydrates. However, all non-slime producing staphylococcal strains were unable to produce slime either on polystyrene or glass material with similar media and incubation conditions. This fact correlates favourably with the methodology used by other investigators for detection of buiofilm producing phenotype among staphylococci. Reference strains S. epidermidis ATCC 35984 (high slime producer) S. epidermidis ATCC 35983 (moderate slime producer) and S. epidermidis ATCC 12228 (non slime producer) included in our study behaved characteristically by all three methods. References
Copyright 2006 - Indian Journal of Medical Microbiology |
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