Background: The most important pathogen in nosocomial infections are microorganisms in the patient's body. 90 percent of nosocomial infections caused by bacteria. Medlar is an medicinal plant that its therapeutic effects has historically been emphasized. The aim of this study was to evaluate the antibacterial effect of methanolic and ethanolic leaf extract of medlar against bacteria isolated from hospital environment.

Materials and Methods: In this experimental study, the Nosocomial bacteria were obtained from Shahid Mostafa Khomeini hospital, Ilam, Iran. Soxhlet extraction method was used for medlar leaf extract. Disk diffusion method was used to study the effect of antimicrobial and broth microdilution method were used to determine the minimum inhibitory concentration (MIC) and Minimum Bactericidal Concentration (MBC).

Results: Two strains of Pseudomonas aeruginosa, three strain of Staphylococcus aureus and five strains of Escherichia coli were isolated from hospital. The results showed that the methanolic extract of Medlar leaf inhibited the growth of all strains of pseudomonas aeruginosa and four strain of Staphylococcus aureus and also inhibits the growth of all strains of Escherichia coli strains except E4 strain. The maximum antimicrobial activity was against E2 strain that zone diameter around it was 19/67 Millimeters. Quantities of minimum inhibitory concentration for all three strains P1, P2 and P3 and E2, E3, E5, S1, S2 and S3 strains was equals with 125 mg/ml.

Conclusion: Medlar leaf methanolic extract possesses significant antibacterial activity against bacteria causing nosocomial infections and so this extract can be considered in the control of infectious diseases.

Background: Biosurfactants are amphiphilic biological compounds produced extracellularly by a variety of microorganisms. Because their use in various industries are of a particular importance. The aim of this study was to identify a strain of bacteria of the genus Bacillus Cereus biosurfactant producers and investigate the antibacterial effects of biosurfactant produced.

Materials and Methods: In this study, different samples of oil, water and soil contaminated with oil were prepared. Hemolytic activities, emulsification and measurement of surface tension were used and selected strains were identified by biochemical tests. The nature and effect of antibacterial biosurfactant were evaluated for strain selection.

Results: In this study, eighty eight bacterial strains were isolated. Among them, 24 strains were hemolytic activity. Among them, 14 strains have emulsification activity more than 70% and finally from among them four strains were able to convey to the surface tension of less than 40 mN/m. On the basis of biochemical tests, a strain selective in this study as B. cereus 43 strain, were identification and selection. The results of investigating the nature biosurfactant determined that the type of lipopeptide. Also, the produced biosurfactant has antibacterial activity against six bacterial infectious. The most sensitive and the most resistant bacteria than the impact of biosurfactant extract, of S. aureus PTCC1112 and of the Proteus mirabilis ATCC 2601 respectively. Also, the results of MIC, MBC showed that MIC extract were effective in a dilution of 63 mg/ml on S. aureus PTCC1112 and S.epidermidis ATCC 2405 and the MBC extract had the greatest effect in a dilution of 125mg/ml on Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa PTCC 1074 respectively.

Conclusion: Bacillus Cereus 43 had high potential in reducing the surface tension and biosurfactant extracted had high antibacterial effects. Therefore, Frequency of potential has for applications of biotechnology and the environment.