Abstract

The most common surface structures bacteria are monomolecular crystalline arrays of proteinaceous subunits termed surface layers or S-layers. Since S-layer-carrying organisms are ubiquitous in the biosphere and because S-layers represent one of the most abundant cellular proteins, it is now obvious that these metabolically expensive products must provide the organisms with an advantage of selection in very different habitats. S-layers have been associated with a number of possible functions that relate to pathogenicity. S-layers can function as adhesins, enabling the bacterium to adhere to host cell membranes and tissue surfaces in order to colonize and protect bacteria from harmful enzymes and antimicrobial agents or changes in pH. Bacillus cereus is one of nosocomial infections bacteria. B. cereus produces several potential virulence factors such as S-layer. A total of 274 strains were isolated from staff hand and hospital surfaces of Azzahra-hospital during 2005 to 2007 years. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of S-layer proteins extracted from B. cereus strains by using Tris-HCl (pH 8) showed that the S-layer proteins of different strains isolate of staff hands and hospital surfaces had subunit molecular weight of 97-kDa. Antibiotic susceptibility was performed according to antibiotic susceptibility standard disc diffusion agar. All the statistical analyses carried out using SPSS version 14. Chi-square and fisher test used for determination of significance of association. The p≤ 0.05 was considered significant. From 247 bacteria, frequency of B. cereus strains was 9.49%. From 13 isolated B. cereusof, staff hand 11 strain (84/6%) and from 13 isolated B. cereus from hospital surfaces, 1 strain (7/7%) production S-layer. According to the antibiogram result, S-layer non producer strains, in comparison with S-layer producer strains, were more sensitive to antibiotics. The result showed high prevalence of S-layer producer of B. cereus strains in hospital; and this point is due to the increased antibiotic resistance of nosocomial infections.

Key words: S-layer, Bacillus cereus, antibiotic resistant, nosocomial infections.