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Pseudomonas aeruginosa is an important nosocomial pathogen. Metal nanoparticles (NPs) have shown a promising antibacterial activity against multidrug resistant strains. The purpose of this study was to investigate the synergistic antibacterial effect of silver nanoparticles functionalized by Thiosemicarbazid with ciprofloxacin and their effect on the expression of mexA-B efflux pump genes in ciprofloxacin resistant P. aeruginosa. Ciprofloxacin resistant P. aeruginosa strains were isolated from clinical specimens. Silver nanoparticles (Ag NPs) were functionalized using glutamic acid and conjugated with Thiosemicarbazid (TSC). Antibacterial synergism of Ag-TSC NPs with ciprofloxacin against P. aeruginosa and possible effect of the NPs on the expression of MexA and MexB genes were evaluated using quantitative PCR. The Ag-TSC NPs (concentration ≥ 32 μg/mL) displayed synergistic effects with ciprofloxacin (at sub-MIC concentration), which efficiently inhibited bacterial growth. Expression of mexA and mexB genes was reduced among the strains that simultaneously were exposed to the Ag -TSC NPs and ciprofloxacin by 6.0 and 2.75 folds, respectively, compared to the controls. In this study synergism of Ag-TSC NPs with ciprofloxacin against multi-drug P. aeruginosa by attenuation of ciprofloxacin resistance genes was observed, which could be promising to be used in antibacterial approaches. KeywordsEfflux pumps . Pseudomonas aeruginosa . Silver nanoparticles . Thiosemicarbazide Abbreviations TSC thiosemicarbazide NPs nanoparticles MIC minimum inhibitory concentration CIP ciprofloxacin ROS reactive oxygen species qPCR Quantitative polymerase chain polymerization * Hojjatolah Zamani

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Municipal waste is rich in lignocellulosic compounds which contain cellulose, lignin and hemicellulose. Microorganisms can break down such compounds and convert them into glucose and other carbohydrates. The current study was performed to isolate and identify cellulolytic bacteria in municipal waste. Municipal waste samples were collected and plated on Carboxymethyl cellulose (CMC) agar. Preliminary identification of the isolates was performed using standard biochemical assays. The activity of carboxymethyl cellulose (CMCase) was specified through measuring the release of reducing sugars from CMC. Different nitrogen sources at various concentrations and initial pH values were evaluated for their effect on enzyme production. Further the enzyme production was determined at different fermentation times. Molecular identification was then performed using bacterial 16s rRNA gene amplification and sequencing. A cellulolytic bacterium was isolated from municipal waste samples and identified based on morphological, physiological and biochemical characteristics along with 16S rRNA analysis. The isolated bacterium was identified as Bacillus subtilis (accession number: KU681044). Whose growth characteristics showed that its growth curve entered the logarithmic phase following 10-18 h with the stable growth phase ranging from 23 to 37 h. The optimal carbon source for fermentation was 1% rice hull, with the nitrogen source comprised of 2% peptone and yeast extract. The the minimum CMCase activity was observed at an initial medium pH of 4.0, while the maximum was observed at pH 7. The strain grew vigorously and the cellulase yield was high at 6-24 h fermentation time period. The isolated bacteria showed the degrading potential of cellulose which could be employed in local industrial process.