A fluorescent method for assessing the antimicrobial efficacy of disinfectant against Escherichia coli ATCC 35218 biofilm

Platinum nanoparticles inhibit bacteria proliferation and rescue zebrafish from bacterial infection

Platinum nanoparticles rescue zebrafish from bacterial infection.

Fluorescence assay for evaluating microbicidal activity of hand antiseptics

We developed a fluorescent β-d-glucuronidase activity (BGA)-based assay for detecting and quantifying Escherichia coli in samples to assess the biocide efficacy of hand antiseptics. The fluorescence level is proportional to the number of viable E. coli organisms present. We compared our assay results to those of the E. coli plate count method specified by the European standard for testing hygienic hand rub disinfectant products (EN1500). The plate count method requires excessive handling and materials and is not valid if the number of organisms per plate is too low or high for counting in many of the samples. We optimized the fluorescent assay based on the cleavage of 4-methylumbelliferyl-β-d-glucuronide by adding 4-nitrophenyl-β-d-glucuronide, a nonfluorogenic BGA substrate, to induce glucuronidase activity and reduce assay time. Furthermore, our method can be automated and eliminates the need for multiple dilutions. Fluorescence was temporally monitored, and the time required to reach a specific value of fluorescence was correlated with the initial number of viable E. coli organisms on the samples. There was a positive correlation (P < 0.05) with a high correlation coefficient (R(2) = 0.82) between the E. coli counts by plate count and fluorescence methods. Reported effects in fluorescent BGA were compared to the EN1500 plate count method with five hand disinfectants. We found our method more advantageous, because it was as sensitive as the EN1500 method, requires less time to complete, and is less expensive and less laborious than conventional plating techniques.

Damage of Candida albicans blastoconidia exposed to biocides

The damage of Candida albicans blastoconidia exposed to the lowest concentration of chemical disinfectant and antiseptic passing the EN 1275:2005 at 5 min contact time was examined under transmission electron microscopy and scanning electron microscopy. The blastoconidia of C. albicans 82 exposed to the chemical products showed the following damage: Incidin Liquid Spray (disinfectant) and Spitaderm (antiseptic) - cytoplasm congealing; Incidin Plus and Lysoformine 3000 (disinfectants) - cell wall and cell membrane damage, and leakage of the cytoplasm; Medicarine (disinfectant) - cytoplasm denaturation and rough cytoplasm. The damage of blastoconidia of the strains C. albicans 24 and C. albicans 28, exhibiting different susceptibility to Lysoformine 3000 was compared under scanning electron microscopy. The blastoconidia of the strain C. albicans 28 did not exhibit essential damage at a concentration 16 times lower (0.02%) than the lowest concentration of Lysoformine 3000 (Lc-LYS) for this strain (0.32%). At this concentration (0.02%, corresponding to Lc-LYS for C. albicans 24) the more sensitive isolate 24 showed substantial damage. The conducted study exhibited the effects of the tested products against the viability and structural integrity of the cells. Blastoconidial buds at the early stage of development seem to be very susceptible to the action of the tested products. The budding areas are located mainly at the blastoconidial poles.

New device for high-throughput viability screening of flow biofilms

Control of biofilms requires rapid methods to identify compounds effective against them and to isolate resistance-compromised mutants for identifying genes involved in enhanced biofilm resistance. While rapid screening methods for microtiter plate well ("static") biofilms are available, there are no methods for such screening of continuous flow biofilms ("flow biofilms"). Since the latter biofilms more closely approximate natural biofilms, development of a high-throughput (HTP) method for screening them is desirable. We describe here a new method using a device comprised of microfluidic channels and a distributed pneumatic pump (BioFlux) that provides fluid flow to 96 individual biofilms. This device allows fine control of continuous or intermittent fluid flow over a broad range of flow rates, and the use of a standard well plate format provides compatibility with plate readers. We show that use of green fluorescent protein (GFP)-expressing bacteria, staining with propidium iodide, and measurement of fluorescence with a plate reader permit rapid and accurate determination of biofilm viability. The biofilm viability measured with the plate reader agreed with that determined using plate counts, as well as with the results of fluorescence microscope image analysis. Using BioFlux and the plate reader, we were able to rapidly screen the effects of several antimicrobials on the viability of Pseudomonas aeruginosa PAO1 flow biofilms.