Ewa Dworniczek

In situ photoexcitation of silver-doped titania nanopowders for activity against bacteria and yeasts

Photocatalytic and in situ microbial activity of the amorphous and annealed states of Ag-doped and un-doped titania were examined. Studies on their structure, morphology, composition, and the photo-absorption characteristics of these materials were performed. These results were correlated with the photocatalytic and microbial activity against methicillin resistant Staphylococcus aureus K324 (MRSA), methicillin susceptible S. aureus ATCC 25923 (MSSA), Escherichia coli PA 170, and yeasts Candida albicans ATCC 90028. The annealed powders containing anatase form of titania exhibited relatively higher photocatalytic activity,corresponding to activity against MRSA,when exposed to UV-A radiation. In comparison, amorphous powders exhibited low photoactivity and showed poor antibacterial performance against MRSA under UV-A exposure. Doping of amorphous titania with Ag resulted in an anti-MRSA effect without exposure to UV radiation. In the Ag-doped crystalline anatase samples, the size of Ag primary nanocrystallites increased, which led to the decrease in the surface concentration of Ag and detriment anti-MRSA activity.

Antibacterial activity of gemini quaternary ammonium salts

A series of gemini quaternary ammonium salts (chlorides and bromides), with various hydrocarbon chain and spacer lengths, were tested. These compounds exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria and were not mutagenic. The strongest antibacterial effect was observed for TMPG-10 Cl (against Pseudomonas aeruginosa ATCC 27853) and TMPG-12 Br (against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 11229 and clinical ESBL(+) isolate 434) surfactants. These compounds inhibited the adhesion of Staphylococcus epidermidis ATCC 35984 to a polystyrene surface and eradicated biofilm formed by P. aeruginosa PAO1. The activity of studied compounds was dependent on hydrocarbon chain length.

Virulence of Enterococcus isolates collected in Lower Silesia (Poland)

148 enterococcal strains: E.faecalis (108), E.faecium (35), E.gallinarum (3), E.casseliflavus (1) and E.durans (1) from various clinical specimens were investigated for their ability to adhere to Caco-2 and HEp-2 cell lines, and also for the presence of the esp gene, biofilm formation, production of haemolysins, DNAse and lipase. Several types of enterococcal adhesion to both cell lines were noted. An aggregative adherence was the most frequent among E.faecalis and E.faecium isolates. Other species presented various adhesive types. The occurrence of virulence factors in the whole group of strains was as follows: esp gene in 53.4%, biofilm in 45.3%, haemolysins in 15.5%, DNAse in 12.2% and lipase in 33.1% of enterococcal isolates. It appears that the adherence of the enterococci studied was not significantly associated with the presence of virulence factors.

Biocidal effect and durability of nano-TiO2 coated textiles to combat hospital acquired infections

While antimicrobial textiles have received considerable interest and attention from both the scientific community and general consumers, there have been very few studies investigating the durability of such antimicrobial activities. In this study, we describe the modification of the surface of textiles that were modified with commercially available titanium dioxide (TiO2) powder (P25 Aeroxide®, Degussa™) using a sonochemical technique. The antibacterial activity of TiO2 can improve textile quality and effectively reduce the rate of infections acquired in hospitals. Medical garments produced from such fabrics may improve the patients recovery and revolutionize the textile market. This modification imparts biocidal properties to these textiles, which were then optimized to acquire properties of the textile. Samples were washed for 30 cycles at three different temperatures (40 °C, 60 °C and 90 °C) to test the durability of the bonding of the nanoparticles to textiles and the effectiveness was examined with respect to their antimicrobial activity against hospital pathogens: Escherichia coli, MRSA and Candida albicans. Samples surfaces were examined by a Scanning Electron Microscope equipped with Energy Dispersive X-ray Spectroscopy (SEM/EDS) for surface imaging. Atomic Absorption Spectrometry (AAS) was used as a technique to quantify the Ti present on the fabric. The best durability of TiO2 on textiles was best retained after washing at 40 °C. From an environmental point of view, the release of nanomaterial from textiles was acceptable against currently available benchmarks. We have investigated the adhesion of nanoparticles (NPs) to the textile surface. Medical garments, bed linens and upholstery produced from such fabrics may improve hospital hygiene against antibiotic resistant superbugs and help reduce hospital acquired infections.

Enterococcus in wound infections: Virulence and antimicrobial resistance

Enterococci, a complex group of facultative pathogens have become increasingly isolated in various hospital settings. They are considerable frequently cultured from traumatic and surgical wounds. We investigated 57 strains of the species E. faecalis, E. faecium and E. casseliflavus isolated from infected wounds. Their ability to produce virulence factors and their sensitivity to antibiotics were evaluated using phenotypic and genotyping methods. In the phenotype studies, significant portion of the isolates produced biofilm (66.7%) and gelatinase (36.8%). Nearly 30% of the strains expressed hemolytic properties. Only a few produced DNAse (15.8%) and lipase (7.0%). The genes esp, gelE, cylA, cylB, cylM and agg were detected in most of the isolates (38.6-87.7%). All the isolated enterococci were susceptible to vancomycin and were characterized by their low resistance to antibiotics, except aminoglycosides (HLR).

Genotypic characterization of hospital Enterococcus faecalis strains using multiple-locus variable-number tandem-repeat analysis

Aims:  The level of genetic diversity and relationships between the specific genotypes and the distribution of virulence determinants among Enterococcus faecalis strains isolated from patients hospitalized in different wards of two hospitals were investigated.

Resistance patterns and occurrence of virulence determinants among GRE strains in southwestern Poland

PURPOSE The aim of this study was to determine the antimicrobial resistance and the occurrence of virulence determinants among glycopeptide-resistant enterococci (GRE) isolated in 2007-2009 from patients hospitalized in southwestern Poland. MATERIAL AND METHODS The minimal inhibitory concentrations (MICs) of antibiotics were determined by agar dilution method or by E-test®. The presence of vanA - vanG resistance and virulence genes (agg, esp, gelE and cylA, cylB, cylM) was investigated using PCR. The ability to form biofilm and the activity of gelatinase, hemolysins, lipase and DNase were tested. RESULTS All the GRE strains were susceptible to linezolid, daptomycin, and tigecycline and resistant to norfloxacin. In the Enterococcus faecium group, 17 strains carried the vanA gene and 20 the vanB gene. In the Enterococcu faecalis group, 4 strains carried the vanA gene and 1 the vanB gene. There were differences in tetracycline susceptibility between the VanA (70%) and the VanB (55%) phenotypes. Only linezolid had high activity against both the VanA and the VanB phenotypes. The esp gene was present in most of the GRE strains, but only 3 E. faecalis strains produced biofilm. Lipase was produced by 10/42 examined strains, gelatinase by 4/42 and hemolysin by 3/42 isolates. CONCLUSIONS Linezolid seems to be the optimal option in empirical therapy of infections caused by GRE strains because of the relationship between its activity (MIC value) and susceptibility breakpoint. There was no correlation between the prevalence of different virulence genes and resistance to the antibiotics tested.

Prevalence of non-O157 Escherichia coli Strains among Shiga-like Toxin-Producing (SLTEC) Isolates in the Region of Lower Silesia, Poland

During 5 y (1997–2002) in the region of Lower Silesia, Poland, 55 shiga-like toxin-producing strains were isolated from children with diarrhoea, none of whom developed haemolytic uremic syndrome. Shiga-like toxin production was detected on Vero cells and confirmed by the detection of slt1 and slt2 gene sequences. Most of isolates examined possessed slt2 gene alone (41.8%), or in combination with slt1 gene (38.2%). None of the shiga-like toxin-producing strains was of serotype O157:H7. It appears that non-O157 shiga-like toxin-producing E. coli strains are prevalent as the causal agent of severe diarrhoea in the region.

Enterococcus – virulence and susceptibility to photodynamic therapy of clinical isolates from Lower Silesia, Poland

Abstract Background: A collection of 400 enterococcal isolates from clinical samples of hospitalized patients were studied for their virulence traits according to the isolation site. Formation of biofilm and production of DNase, hemolysin, lipase, and gelatinase were characterized. Biofilms of selected strains were examined for their susceptibility to antimicrobial photodynamic therapy (aPDT). Methods: All strains were tested for biofilm production by microtiter method and the activity of hemolysin, gelatinase, lipase, and DNase by plate method with an adequate substrate. Photodynamic therapy with Photolon and red laser light was performed towards 48 h biofilms of eight representative strains. The viability of biofilms was tested by the BactLight assay and visualized under a fluorescent microscope. Results: Among the 400 isolates, 69.8% strains of Enterococcus faecalis, 30% of Enterococcus faecium, and 0.2% of Enterococcus casseliflavus were identified. In vitro, production of biofilm was found in 65.7% of enterococci. Biofilm-positive strains were isolated from urinary tract infections (81%), wound infections (71%), respiratory tract infections (62%), and gastrointestinal tract (47%) (colonization). Hemolysin activity was observed in 28.5%, gelatinase in 24.5%, lipase in 23%, and DNase in 3.5% of all, mostly biofilm-positive, isolates. Photodynamic therapy with Photolon efficiently reduced the enterococcal biofilms. Conclusions: The study demonstrated the high prevalence of biofilm-producing clinical enterococci, their virulence potential being higher than for biofilm-negative strains, and the susceptibility to aPDT of mature biofilms produced by strains, regardless of their species and site of isolation.

An efficient Nb-modified BiVO4 film for photo-induced bacterial inactivation and photocatalytic removal of organic pollutants

Using a Nb-modified BiVO4 film, the photo-induced properties in Methicillin-resistant Staphylococcus aureus (MRSA) inactivation under simulated solar light reached 43% after 1 hour of irradiation, while 72% of Rhodamine B was degraded after 3 hours. To evaluate the efficiency of Nb–BiVO4, its photo-performance was compared with that of BiVO4/TiO2 composites and pure BiVO4.