COMBINATORIAL EFFECT OF D-AMINOACIDS AND TETRACYCLINE AGAINST PSEUDOMONAS AERUGINOSA BIOFILM

Objective: The present study attempted to evaluate the anti-biofilm activity of D-amino acids (D-AAs) on Pseudomonas aeruginosa and determine if the combination of D-AAs with tetracycline enhances the anti-biofilm activity in vitro and ex vivo.Methods: Different D-AAs were tested for antibiofilm activity against wild type P. aeruginosa PAO1 and two multidrug resistant P. aeruginosa clinical strains in the presence of sub inhibitory concentrations of tetracycline using crystal violet microtitre plate assay. Results were further validated using in vitro wound dressing and ex vivo porcine skin models followed by cytotoxicity and hemocompatibility studies.Results: D-tryptophan (5 mmol) showed 61 % reduction in biofilm formation of P. aeruginosa. Interestingly combinatorial effect of 5 mmol D-tryptophan and 0.5 minimum inhibitory concentration (MIC) (7.5µg/ml) tetracycline showed 90% reduction in biofilm formation. 5 mmol D-methionine shows 28 % reduction and combination with tetracycline shows 41% reduction in biofilm formation of P. aeruginosa. D-leucine and D-tyrosine alone or in combination with tetracycline did not show significant anti-biofilm activity. D tryptophan-tetracycline combination could reduce 80 % and 77 % reduction in biofilm formation in two multi drug resistant P. aeruginosa clinical strains. D-tryptophan-tetracycline-combination could also reduce 76% and 66% reduction in biofilm formation in wound dressing model and porcine skin explant respectively. The cytotoxicity and hemocompatibility studies did not show significant toxicity when this combination was used.Conclusion: The results established the potential therapeutic application of D-tryptophan alone or in combination with tetracycline for treating biofilm associated clinical problems caused by P. aeruginosa

Plasma Choline Metabolites and Colorectal Cancer Risk in the Women's Health Initiative Observational Study

Few studies have examined associations between plasma choline metabolites and risk of colorectal cancer (CRC). Therefore, we investigated associations between plasma biomarkers of choline metabolism [choline, betaine, dimethylglycine and trimethylamine N-oxide (TMAO)] and CRC risk among postmenopausal women in a case-control study nested within the Women’s Health Initiative Observational Study. We selected 835 matched case-control pairs, and cases were further stratified by tumor site (proximal, distal, or rectal) and stage (local/regional or metastatic). CRC was assessed by self-report and confirmed by medical records over the mean 5.2y of follow-up. Baseline plasma choline metabolites were measured by liquid chromatography-tandem mass spectrometry. In multivariable-adjusted conditional logistic regression models, plasma choline tended to be positively associated with rectal cancer risk [OR (95% CI)(highest vs. lowest quartile)=2.44 (0.93–6.40);P-trend=0.08], while plasma betaine was inversely associated with CRC overall [0.68 (0.47–0.99);P-trend=0.01] and with local/regional tumors [0.64 (0.42–0.99);P-trend=0.009]. Notably, the plasma betaine:choline ratio was inversely associated with CRC overall [0.56 (0.39–0.82);P-trend=0.004] as well as with proximal [0.66 (0.41–1.06);P-trend=0.049], rectal [0.27 (0.10–0.78);P-trend=0.02] and local/regional [0.50 (0.33–0.76);P-trend=0.001] tumors. Finally, plasma TMAO, an oxidative derivative of choline produced by intestinal bacteria, was positively associated with rectal cancer [3.38 (1.25–9.16);P-trend=0.02] and with overall CRC risk among women with lower (vs. higher) plasma vitamin B12 levels (P-interaction=0.003). Collectively, these data suggest that alterations in choline metabolism, which may arise early in disease development, may be associated with higher risk of CRC. The positive association between plasma TMAO and CRC risk is consistent with an involvement of the gut microbiome in CRC pathogenesis