[Prevalence of nano structure S-layer and beta-lactamase in Bacillus cereus strains]

S-layer is the outer protein layer in the most archaea and bacteria. S-layer protects bacteria against phagocytosis and prohibits entry of some biomolecules and some antibiotics and adhesion to matrix proteins. S-layer is a virulence agent in bacteria, beta-lactamase can inactive [beta-lactame antibiotics. According to role of beta-lactame antibiotics in the treatment of infectious diseases with Bacillus spp., increasing frequency of S-layer and beta-lactamase producer Bacillus cereus strains in hospitals lead to increase antibiotic resistant nosocomial infections. In this basic study, 274 samples were evaluated with laboratory methods in Alzahra hospital and Isfahan University between 2004 and 2006. Bacterial identification was performed with microbiological methods, such as staining, chemical test, use of differential and selective Bacillus cereus selective agar media. Bacteria cultured in TSA for 16h, and then separated surface proteins, and finally electrophoresis was performed. S-layer in Bacillus cereus has 97KD molecular weight. Production of beta-lactamase was evaluated by acidometric method. Of 247 isolated bacteria, frequency of Bacillus cereus strains, S-layer and beta-lactamase in S-layer producer Bacillus cereus strains were 9.49%, 46.20% and 100%, respectively. Results showed high prevalence of nano structure S-layer and beta-lactamase producer Bacillus cereus strains in hospital. We recommend controlling bacterial population in crowded places and health and therapeutic centers to decrease producing antibiotic resistance bacteria

relationship between cell surface hydrophobicity and antibiotic resistance of streptococcal strains isolated from dental plaque and caries

Bacterial adhesion is governed by specific and nonspecific interactions such as hydrophobicity. Hydrophobic interactions play a role in the adherence of microorganisms to a wide variety of surfaces and facilitate biofilm formation due to bacterial adhesion. In this article the relation between cell surface hydrophobicity and antibiotic resistance was studied. We studied antibiotic susceptibility of isolated Streptococci from dental plaque and caries [by disk diffusion method] and cell suface hydrophobicity [by microbial adhesion to hydrocarbon]. The results indicated that the mean surface hydrophobicity of all mutans and other than mutans Streptococci, without considering their location [caries or plaque] showed significant differences [mean 78%, 59%, respectively], No significant differences among caries and plaque isolated Streptococci were found regarding the antibiotic susceptibility. Chi square test with contingency table showed significant qualitative correlation between classes of hydrophobicity [high, moderate and low] and antibiotic resistance [p= 0.001], but according to the regression models we could not find any linear correlation between cell surface hydrophobicity and the diameter of inhibition zone for each antibiotic separately. The high overall proportion of hydrophobic bacteria found in this study suggests that cell- surface hydrophobicity may play a role in adherence of certain oral species to the tooth surface. If bacteria attach to surfaces and form biofilm they can be more resistant, but these two factors [antibiotic resistance and cell surface hydrophobicity] did not show a linear correlation in this study