Synergistic antibacterial action of β-sitosterol-D-glucopyranoside isolated from Desmostachya bipinnata leaves with antibiotics against common human pathogens

Desmostachya bipinnata (L.) Stapf, Poaceae, or Kusha in Sanskrit, is a sacred grass used extensively in Indian Vedic practices. It is well known for its medicinal value and is used in traditional Indian medicine to treat microbial infection in combination with other herbs. An effort has been made to isolate and characterize the bioactive compounds from the hydroalcoholic extract of D. bipinnata through bioassay guided fractionation, column chromatography. Their individual or combined antimicrobial properties were determined by the Resazurin Microtitre Assay, the checkerboard assay in combination with antibiotics, and by time kill curve analysis. β-Sitosterol-D-glucopyranoside was the bioactive compound identified to have the best antimicrobial activity (MIC 6-50 µg/ml) and it works synergistically with most antibiotics, especially with ciprofloxacin. Time kill curves showed that BS kills most of the pathogens within 5-10 h. To our knowledge at its best, this is the first time report of antibacterial synergy of β-sitosterol-D-glucopyranoside from D. bipinnata.

In vitro activity of antimicrobial combinations against multidrug-resistant Pseudomonas aeruginosa

Introduction Pseudomonas aeruginosa isolates related to nosocomial infections are often resistant to multiple antibacterial agents. In this study, antimicrobial combinations were evaluated to detect in vitro synergy against clinical isolates of P. aeruginosa. Methods Four clinical P. aeruginosa isolates were selected at random among other isolates from inpatients treated at the public University hospital in Ribeirão Preto, SP, Brazil. Two isolates were susceptible to imipenem (IPM-S) and several other antimicrobials, while the other two isolates were imipenem and multidrug resistant (IPM-R). The checkerboard method was used to assess the interactions between antimicrobials. Results Combinations of imipenem or other anti-Pseudomonas drugs with complementary antibiotics, such as aminoglycosides, fosfomycin and rifampin, reached synergy rates of 20.8%, 50%, 62.5% and 50% for the two IPM-S and two IPM-R Pseudomonas isolates, respectively. Imipenem, piperacillin-tazobactam and ceftazidime yielded a greater synergy rate than cefepime or ciprofloxacin. Synergist combinations were more commonly observed when the complementary drug was tobramycin (65%) or fosfomycin (57%). Conclusions Some antibacterial combinations led to significant reductions of the minimum inhibitory concentrations of both drugs, suggesting that they could be clinically applied to control infections caused by multidrug-resistant P. aeruginosa. .

The Comparative Efficacy of Colistin Monotherapy and Combination Therapy Based on in vitro Antimicrobial Synergy in Ventilator-associated Pneumonia Caused by Multi-drug Resistant Acinetobacter baumannii / 결핵및호흡기질환

BACKGROUND: Ventilator-associated pneumonia caused by multi-drug resistant Acinetobacter baumannii has been increasing and growing as a threat in intensive care units. Limited therapeutic options have forced clinicians to choose colistin with or without combination of other antibiotics. We tried to compare the effectiveness between colistin monotherapy and combination therapy based on in vitro synergistic tests. METHODS: From January 2006 to December 2007 in medical ICU of a tertiary care hospital in Korea, We reviewed the medical records of patients treated with intravenous colistin due to ventilator-associated pneumonia caused by multi-drug resistant Acinetobacter baumannii. RESULTS: A total of 41 patients were analyzed. 22 patients had been treated with colistin monotherapy and 19 patients with colistin and combination antibiotics that were found to have in vitro synergistic effects. Baseline characteristics were similar in both groups but the mean duration of colistin administration was significantly longer in the combination group (19.1+/-11.2 days vs. 12.3+/-6.8 days, p=0.042). There were no significant differences in outcome variables between the two groups. CONCLUSION: Combination treatment based on the in vitro antimicrobial synergy test did not show better outcomes compared with colistin monotherapy in VAP caused by multi-drug resistant A. baumannii.