Dragana Bozic

Newly-synthesized chalcones-inhibition of adherence and biofilm formation of methicillin-resistant Staphylococcus aureus

Biofilm formation and adherence of bacteria to host tissue are one of the most important virulence factors of methicillin-resistant strains of Staphylococcus aureus (MRSA). The number of resistant strains is seriously increasing during the past years and bacteria have become resistant, not only to methicillin, but also to other commonly used antistaphylococcal antibiotics. There is a great need for discovering a novel antimicrobial agent for the treatment of staphylococcal infections. One of the most promising groups of compounds appears to be chalcones. In present study we evaluated the in vitro effect of three newly synthesized chalcones: 1,3- Bis-(2-hydroxy-phenyl)-propenone, 3-(3-Hydroxy-phenyl)-1-(2-hydroxy-phenyl)-propenone and 3-(4-Hydroxy-phenyl)-1-(2-hydroxy-phenyl)-propenone on glycocalyx production, biofilm formation and adherence to human fibronectin of clinical isolates and laboratory control strain of MRSA (ATCC 43300). Subinhibitory concentrations of the tested compounds reduced the production of glycocalyx, biofilm formation and adherence to human fibronectin of all MRSA strains. Inhibition of biofilm formation was dose dependent and the most effective was 1,3- Bis-(2-hydroxy-phenyl)-propenone. In our study we demonstrated that three newly-synthesized chalcones exhibited significant effect on adherence and biofilm formation of MRSA strains. Chalcones may be considered as promising new antimicrobial agents that can be used for prevention of staphylococcal infections or as adjunct to antibiotics in conventional therapy.

Licheniocin 50.2 and Bacteriocins from Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 Inhibit Biofilms of Coagulase Negative Staphylococci and Listeria monocytogenes Clinical Isolates.

Background Coagulase negative staphylococci (CoNS) and Listeria monocytogenes have important roles in pathogenesis of various genital tract infections and fatal foetomaternal infections, respectively. The aim of our study was to investigate the inhibitory effects of two novel bacteriocins on biofilms of CoNS and L. monocytogenes genital isolates. Methods The effects of licheniocin 50.2 from Bacillus licheniformis VPS50.2 and crude extract of bacteriocins produced by Lactococcus lactis subsp. lactis biovar. diacetylactis BGBU1-4 (BGBU1-4 crude extract) were evaluated on biofilm formation and formed biofilms of eight CoNS (four S. epidermidis, two S. hominis, one S. lugdunensis and one S. haemolyticus) and 12 L. monocytogenes genital isolates. Results Licheniocin 50.2 and BGBU1-4 crude extract inhibited the growth of both CoNS and L. monocytogenes isolates, with MIC values in the range between 200–400 AU/ml for licheniocin 50.2 and 400–3200 AU/ml for BGBU1-4 crude extract. Subinhibitory concentrations (1/2 × and 1/4 × MIC) of licheniocin 50.2 inhibited biofilm formation by all CoNS isolates (p < 0.05, respectively), while BGBU1-4 crude extract inhibited biofilm formation by all L. monocytogenes isolates (p < 0.01 and p < 0.05, respectively). Both bacteriocins in concentrations of 100 AU/mL and 200 AU/mL reduced the amount of 24 h old CoNS and L. monocytogenes biofilms (p < 0.05, p < 0.01, p < 0.001). Conclusions This study suggests that novel bacteriocins have potential to be used for genital application, to prevent biofilm formation and/or to eradicate formed biofilms, and consequently reduce genital and neonatal infections by CoNS and L. monocytogenes.

The Effect of Field Dodder (Cuscuta campestris Yunck.) on Morphological and Fluorescence Parameters of Giant Ragweed (Ambrosia trifida L.)

SUMMARY The effect of the parasitic flowering plant known as field dodder (Cuscuta campestris Yunck.) on morphological and fluorescence parameters of infested giant ragweed (Ambrosia trifida L.) plants was examined under controlled conditions. The parameters of chlorophyll fluorescence (Fo, Fv/Fm, ΦPSII, Fv, Fm, ETR and IF) were measured on infested (I) and non-infested (N) A. trifida plants over a period of seven days, beginning with the day of infestation. Morphological parameters (plant height, dry and fresh weight) were measured on the last day of fluorescence measurements. C. campestris was found to affect the height, fresh and dry weight of the infested A. trifida plants, causing significant reduction in plant height and dry weight. Field dodder also affected several parameters of chlorophyll fluorescence (Fo, Fv/Fm, ΦPSII and Fv) in infested A. trifida plants.

Effect of nicosulfuron on plant traits of Xanthium strumarium

Field experiments were conducted in 2008 and 2009 at the Experimental Field Institute Padinska Skela PKB Agroe-konomik, near Belgrade, to quantify effects of nicosulfuron on plant traits (vegetative production and fecundity) of Xanthium strumarium. Plants of X. strumarium were grown in monoculture on plots of 5 × 4.2 m. Inter-row spacing was 24 cm and the distance between the rows was 70 cm. Plants were treated with nicosulfuron when they developed two pairs of leaves. The applied rates of nicosulfuron were 20, 40 and 80 g a.i. ha−1 and one control treatment (without herbicide application) was included. Vegetative parameters (height, fresh weight, leaf area and leaf area index (LAI)) were recorded just before herbicide application and four times after the herbicide treatment. Measurements were made at intervals of about two weeks. At maturity, fecundity of weeds (bur weight plant−1 and bur number plant−1) was measured. In both years, the application of nicosulfuron caused less growth (height, fresh weight and LAI) of X. stru-marium in comparison with the control. All rates of nicosul-furon reduced vegetative parameters, which decreased as rates of nicosulfuron increased. On the other hand, effects of nicosulfuron on bur production were not equivalent to its effects on vegetative parameters. Only the highest rate of nicosulfuron reduced bur production significantly.

Antibiofilm effects of topical corticosteroids and intranasal saline in patients with chronic rhinosinusitis with nasal polyps depend on bacterial species and their biofilm-forming capacity

Microbial biofilms have been implicated in the pathogenesis of chronic rhinosinusitis with nasal polyposis (CRSwNP). Intranasal application of corticosteroids and saline is a reliable option for their management. The aim of our study was to evaluate in vitro antibiofilm effects of corticosteroids and isotonic and hypertonic nasal saline in CRSwNP patients. The sinus mucosal specimens were harvested from the ethmoid cavity of 48 patients with CRSwNP and further subjected to hematoxylin–eosin staining and microbiology analysis. The biofilm-forming capacity of isolated bacterial strains was detected by microtiter-plate method and the effects of therapeutic doses of mometasone, fluticasone, isotonic and hypertonic saline on biofilm production were investigated. Bacterial strains were isolated in 42 (87.5%) patients: one organism in 34 (80.9%) and two organisms in 8 (19.1%). Staphylococcus epidermidis (34%) and Staphylococcus aureus (28%) were the most prevalent bacteria in biofilms of CRSwNP patients. Corticosteroids and saline solutions significantly reduced biofilm formation (p < 0.01 and p < 0.05, respectively) with better efficacy of fluticasone and isotonic nasal saline. Treatment with fluticasone, mometasone, isotonic and hypertonic nasal saline completely prevented biofilm production in 66, 50, 84 and 38% of bacterial strains, respectively. The most significant density reduction was observed in biofilm formed by Staphylococcus aureus, Pseudomonas aeruginosa and Streptococcus pneumoniae compared to other bacterial species (p < 0.01, p < 0.05, p < 0.05, respectively). The antibiofilm effects of corticosteroids and saline solutions also greatly depended on bacterial biomass (p < 0.05), with the most significant effect on high compared to small amount of formed biofilm. The topical steroids and nasal saline are shown to be potent antibiofilm agents in patients with CRSwNP. The effects of tested compounds depend on bacterial species and volume of formed biofilm.

Gene Flow from Herbicide-Resistant Sunflower Hybrids to Weedy Sunflower

Weedy forms of cultivated sunflower (Helianthus annuus) are invasive species widely distributed in several regions of the world and are commonly controlled by applying acetohydroxyacid synthase (AHAS)-inhibiting herbicides, such as imidazolinones (IMIs) or sulfonylurea (SUs). The widespread adoption of herbicide-resistant crops has exposed the weedy population to the high risk of crop-to-weedy gene flow. The aim of this study was to check and quantify the gene flow from IMI- and SU-resistant sunflower hybrids to weedy sunflower populations. Field experiments were conducted in 2008 at two sites in Serbia to evaluate the relationship of distance between the crop and the weedy sunflower and its impact on the percentage of gene flow. The weedy sunflower progenies were evaluated through herbicide resistance and SSR marker study. Hybridization with IMI-resistant hybrids was not confirmed. Conversly, SU-resistance trials and SSR marker studies partially confirmed the transfer of resistance within the weedy population.