No abstract

Pseudomonas aeruginosa, a ubiquitous environmental organism, is a difficult-to-treat opportunistic pathogen due to its broad-spectrum antibiotic resistance and its ability to form biofilms. In this study, we investigate the link between resistance to a clinically important antibiotic, imipenem, and biofilm formation. First, we observed that the laboratory strain P. aeruginosa PAO1 carrying a mutation in the oprD gene, which confers resistance to imipenem, showed a modest reduction in biofilm formation. We also observed an inverse relationship between imipenem resistance and biofilm formation for imipenem-resistant strains selected in vitro, as well as for clinical isolates. We identified two clinical isolates of P. aeruginosa from the sputum of cystic fibrosis patients that formed robust biofilms, but were sensitive to imipenem (MIC ≤ 2 μg/ml). To test the hypothesis that there is a general link between imipenem resistance and biofilm formation, we performed transposon mutagenesis of these two clinical strains to identify mutants defective in biofilm formation, and then tested these mutants for imipenem resistance. Analysis of the transposon mutants revealed a role for previously described biofilm factors in these clinical isolates of P. aeruginosa, including mutations in the pilY1, pilX, pilW, algC, and pslI genes, but none of the biofilm-deficient mutants became imipenem resistant (MIC ≥ 8 μg/ml), arguing against a general link between biofilm formation and resistance to imipenem. Thus, assessing biofilm formation capabilities of environmental isolates is unlikely to serve as a good predictor of imipenem resistance. We also discuss our findings in light of the limited literature addressing planktonic antibiotic resistance factors that impact biofilm formation.

No abstract

Tannase has great commercial significance in the feed, drink and medical industries, tannase is an enzyme catalyzing the hydrolysis ofthe ester bonds of tannic acid, a water soluble polyphenol secondary metabolites that present in many different parts of plants, to produce gallic acid and glucose and galloyl esters. Although several substrates for the production of tannase have been reported as being economically effective such as utilization of tanninrich substrate rather than pure tannic acid, however, there is still need to develop the substrate to make the entire process much cheaper and more effective. Here we reported tannase production from Erwinia as there is not found any report on tannase production from Erwinia. The present work deals with physiological studies on bacterial tannase. Out of 50 spoilt cucumber and tomato samples from local markets in Baghdad city. Eleven isolates from Erwiniacarotovora were obtained (22%). Tannase activity was found in 7 isolates in primary and secondary screening and the isolate ErwiniacarotovoraEt 3 yielded the highest tannase production. The enzyme activity was increased to 62.6 U/ml when this isolate was cultivated under the optimal conditions which consisted of using basal medium containing(5% w/v) pomegranate peels extract and (2% w/v)ammonium nitrate with pH 5.0 at 30°C for 24 hour. The metal ions K + , Ca ++ , Na + , Mg ++ and Mn ++ did not affect enzyme production. However, metal ions like Zn ++ , Cu ++ , Co ++ , Fe +++ and detergents inhibited the production of tannase. The enzyme revealed maximum activity (79.50U/ml) with pomegranate peels powder(1% w/v), followed by eucalyptus and pine barks powders with relative activities of 127,112 and 103%, respectively, as substrates. Consequently, pomegranate peel has a potential as an effective and much cheaper (economical) substrate for tannase production and tannase activity in comparison with traditionally used substrates like tannic acid and other saccharides.