ABSTRACT
Aims: Pseudomonas aeruginosa is a drug resistance opportunistic bacterium. Biofilm formation is key factor for survival of P. aeruginosa in various environments. Polysaccharides may be involved in biofilm formation. The purpose of this study was to evaluate antimicrobial and anti-biofilm activities of seven plant extracts with known alpha-glucosidase inhibitory activities on different strains of P. aeruginosa. Methodology and results: Plants were extracted with methanol by the maceration method. Antimicrobial activities were determined by agar dilution and by growth yield as measured by OD560nm of the Luria Bertani broth (LB) culture with or without extracts. In agar dilution method, extracts of Quercus infectoria inhibited the growth of all, while Myrtus communis extract inhibited the growth of 3 out of 8 bacterial strains with minimum inhibitory concentration (MIC) of 1000 μg/mL. All extracts significantly (p≤0.003) reduced growth rate of the bacteria in comparison with the control without extracts in LB broth at sub-MIC concentrations (500 μg/mL). All plant extracts significantly (p≤0.003) reduced biofilm formation compared to the controls. Glycyrrhiza glabra and Q. infectoria had the highest anti-biofilm activities. No correlation between the alpha-glucosidase inhibitory activity with growth or the intensity of biofilm formation was found. Conclusion, significance and impact of study: Extracts of Q. infectoria and M. communis had the most antimicrobial, while Q. infectoria and G. glabra had the highest anti-biofilm activities. All plant extracts had anti-biofilm activities with marginal effect on growth, suggesting that the mechanisms of these activities are unrelated to static or cidal effects. Further work to understand the relation between antimicrobial and biofilm formation is needed for development of new means to fight the infectious caused by this bacterium in future.
ABSTRACT
Non-fermenting Gram-negative bacteria are unable to ferment sugars in order to generate energy. They are ubiquitous in nature, and have a wide geographic distribution. They are also common in hospital settings, and may be isolated from humidifiers, ventilator machines, dialysis machines and other equipment, as well as from the skin of hospital personnel. This study focused on the isolation of multidrug resistant [MDR] non-fermenting Gram negative bacteria from clinical samples. Antimicrobial susceptibility, detection of extended spectrum beta-lactamases [ESBL], and the presence of CTX-M and Metallo beta-lactamase [MBL] in the isolated bacteria were evaluated. Agar dilution method was used to test the susceptibility of the isolates to 10 antibacterial agents. All the isolates that were resistant to >/= 3 antibacterial agents from different classes were regarded as MDR [111 isolates] and were selected for further studies. beta-lactamase and ESBL production were detected by nitrocefin discs, combined discs [CD] and double discs plus CD [DCDT]. blaCTX-M and MBL were detected by PCR and EDTA synergy methods respectively. Among the MDR isolates the isolation frequency of Pseudomonas aeruoginosa, Stenotrophomonas maltophilia and Acinetoacter baumannii were 83.7%, 9.9% and 6.3% respectively. Resistance to imipenem [0.9%] and Ceftazidim [13.6%] was low, but resistance to other beta-lactams was high, and 29.7% were resistant to >/= 6 antibacterial agents from different classes simultaneously. beta-lactamase was produced by 41.4% of the MDR isolates. Detection of ESBLs by a CD [59.4%] or DCDT test [46.8%] was not significantly different, but with a combination of CD and DCDT a higher percentage of ESBLs in the isolates [P