Background: Efflux is the process in which bacteria transport compounds outside the cell which are potentially toxic, such as drug or chemicals or compounds. Materials and methods: For this review article by using key words: multidrug resistance, microorganims, efflux pumps, resistance mechanism we have assessed 12 articles in journals published during 1997-2002 Results: Multidrug efflux systems endow on bacterial cells the ability to limit the access of antimicrobial agents to their targets. By actively pumping out antibiotic molecules, these systems prevent the intra cellular accumulation necessary for antibiotics to exert their lethal actively. Drug efflux appears to be one of the most widespread antibiotic resistance mechanisms among microorganisms, since it has been demonstrated to occur in many Gram positive and Gram-negative bateria including medically important species like staphylococci, streptococci, enterobacteria and opportunistic pathogens like pseudomonas aeruginosa. Bacterial antimicrobial efflux transporters have generally been grouped into five superfamily. These include the major facilitator superfamily (MFS), the ATP- binding cassette family, the resistance- nodulation- division (RND) family, the small multidrug resistance (SMR) and multidrug and toxic compound extrusion (MATE) family. Conclusion: Efflux pumps can be specific for only one substrate or accommodate a more or less wide range of noxious products.  

Background and Aims: The monitoring of the causative agents of nosocomial infections (Nis), particularly in the Intensive Care Unit (ICU) ward to detect any change in pattern of infection and their resistance profile are crucial. The aim of this study was to investigate the antibiotic resistance pattern among Gram-negative rods isolated from inpatients in different wards of ICU in Shiraz, Iran. Materials and Methods: In this cross-sectional study from Jaunary to June 2017, 91 different clinical samples were collected from Nemazi teaching hospital ICU wards. After confirming all the isolates by the conventional microbiologic methods, their antimicrobial susceptibility pattern against 11 antibiotics were investigated using the disk diffusion test. Extended-spectrum β-lactamase (ESBL) production was also examined. Results and Conclusions: The isolated bacteria were Acinetobacter baumannii (n=72, 79. 1%), Pseudomonas aeruginosa (n=14, 15. 4%), and Escherichia coli (n=5, 5. 5%). The highest and the lowest resistance rates were observed against ampicillin (100% and 95. 8%) among P. aeruginosa and A. baumannii and imipenem and amikacin (0%) among P. aeruginosa and E. coli isolates, respectively. The frequency of multidrug-resistant (MDR) and ESBL-producing isolates was found 84. 6% and 19. 8%, respectively. Of the MDR isolates, 23. 4% were ESBL producers. A significant difference was determined between ESBL production and MDR isolates. Regarding the high rate of antimicrobial resistance among clinical isolates in the study area, the antibiotic susceptibility results may be a useful guide for empirical therapy used by physicians.

Background: Acute myeloblastic leukemia (AML) is the most common form of acute leukemia in adults. One of the major problems in this disease is the emergence of leukemic blast cells that are resistant to anticancer drugs. This phenomenon is termed multidrug resistance (MDR). One cause of the MDR is the expression of the MDR1 gene and its product, P-glycoprotein (Pgp). In this study, we tried to inhibit the MDR phenotype with MDR1/mRNA/Pgp in the leukemic cells using short interfering RNA (siRNA) and two nano particles as non-viral vectors.Methods: The Pgp expressing cell line was established from a parental K562 cell line with increasing concentration of doxorubicin and named KDI/20. In order to reverse the MDR phenotype due to pgp expression, siRNA against MDR1/mRNA was synthesized. siRNA was used on the KDI/20 cells in combination with two nano particles as non-viral vectors: (1) Fugene 6 transfection reagent (cationic lipid) and (2) polyethylenimine (cationic polymer). The effect of these complexes was assessed at the cellular level by flowcytometry (for Pgp detection) and molecular level by Real Time-PCR.Findings: The result showed 79% reduction in Pgp by siRNA /Fugene 6 and 86% reduction in the Pgp by siRNA/PEI at the cellular level in flowcytometry. Also 62% reduction in the MDR1/mRNA by siRNA /Fugene 6 and 74% reduction in the MDR1/mRNA by siRNA /PEI at the molecular level by Real Time-PCR.Conclusion: siRNA could be an efficient method in order to post transcriptional gene silencing and there were no significant differences between two nano particles in gene silencing in this study.