Background & Objective: Staphylococcus aureus, especially methicillin-resistant S. aureus (MRSA), represent serious nosocomial and community infections. Biofilm formation as an important virulence factor may be affected by sub-inhibitory levels of antibiotics. Few studies examined the effects of all therapeutic antimicrobial agents on clinical S.aureus. The current study aimed at observing the inducing and reducing effects of antibiotics, commonly used to treat staphylococcal infections on the production of staphylococcal biofilm. Methods: Four MRSA (1ATCC and 3 clinical) and 1 methicillin-susceptible Staphylococcus aureus (MSSA) strains with biofilm forming ability, evaluated by the Congo red agar (CRA) plate test, were employed. Biofilm formation was measured by crystal violet microtiter plate assay. Cefazolin, rifampicin, vancomycin, oxacillin, clindamycin, cotrimoxazole, minocycline, linezolid, azithromycin, and clarithromycin were added to wells ranging from 0.06to 128 µg/mL (1× to 1/1024 MIC dependent on the MIC value of each strain). Results: The current study showed that azithromycin and vancomycin had a significant inducing effect on biofilm formation. In contrast, linezolid, cefazolin, and clarithromycin, and in the second place, clindamycin and minocycline could inhibit the level of biofilm production in the sub-minimal inhibitory concentrations. Conclusion: The findings demonstrated that the biofilm formation as an important virulence factor may be affected by the subinhibitory levels of antibiotics.

Aim: The aim of this study was to express and purify the recombinant CTB (rCTB) protein from Vibrio cholerae and investigate the biological and immunological characteristics of purified protein in rabbit animal model and in combination with Iranian inactivated V. cholerae whole cells as a domestic recombinant WC-CTB vaccine. Methods and Results: Expressed 6XHis-tagged rCTB was properly purified, and its identity was confirmed by Western blotting using cholera toxin-specific antibody. Concentration of purified protein was assessed to be 700 mg l À1 .GM 1 -ELISA assay showed that purified rCTB pentamer was functionally active and able to bind GM 1 in a dose-dependent manner. Recombinant CTB was inoculated into rabbits through intestinal rout alone and in combination with inactivated whole-cell V. cholerae strains (WC). The anti-CTB IgG titre showed that serum IgG responses were significantly increased in groups immunized with rCTB mixed with inactivated WC in comparison with control group. Furthermore, rCTB without V. cholerae WC also stimulated the IgG responses when inoculated into rabbit intestine. Challenge experiments of immunized rabbits showed an adequate protection against V. cholerae strains. Conclusions: Recombinant CTB alone and in combination with inactivated Iranian strains was protective against live toxigenic V. cholerae strains, made it a potential candidate for an indigenous vaccine. Significance and Impact of the Study: It was proved that rCTB produced in this system can be used as a potent immunogenic protein to stimulate the immunity against V. cholerae strains and can be used for developing a native vaccine composed of our local strains with their own surface structures and antigenic determinants against cholera.

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Background: Enterococcus spp. are part of the normal flora of humans and animals. The nosocomial pathogenicity of Enterococcus spp. has emerged in recent years and has caused great concern due to developing of resistance to many antimicrobial agents. Objectives: The current study aimed to determine the resistance pattern and the type of virulence genes in Enterococcus spp. isolated from Milad hospital of Tehran, Iran. Materials and Methods: The current observational study was conducted from Apr 2014 to Feb 2015 on a total of 149 Enterococcus species isolated from Milad hospital in Tehran, Iran. The antibiotic susceptibility pattern of the bacteria was determined by the disc diffusion method for eight antibiotics. Minimum inhibitory concentration (MIC) of vancomycin was also done using agar-dilution assay by clinical and laboratory standards institute (CLSI) recommendations. The sodA, esp, cyl, ace and gelE genes were detected by polymerase chain reaction (PCR) assay. Results: About 37.5%, 73%, 86.6%, 35.8%, 69%, 60.8%, 45% and 79% of the isolates were resistant to vancomycin, tetracycline, gentam-