Iveta Brožková

Hyaluronic acid (HA) is a natural biopolymer widely used in wound dressings for its supportive role in the healing process. In this study, we investigated the occurrence of microorganisms in chronic wounds and evaluated the antimicrobial activity of newly synthesized HA–Starch-based materials enriched with acidifying agents. Microbial isolates obtained from chronic wounds were tested for susceptibility using the agar diffusion method. The prepared materials exhibited significant antimicrobial activity against both reference strains and multidrug-resistant clinical isolates. Further characterization by scanning electron microscopy and elemental analysis confirmed uniform microfiber morphology and the expected elemental composition of the fibers. Cytotoxicity assessments performed using the xCELLigence system demonstrated the potential safety of developed materials. Overall, the results indicate that HA–Starch-based materials containing acidifying compounds exhibit strong in vitro antimicrobial activity against chronic-wound isolates, supporting their potential for further evaluation in wound care applications.

A blend with pumpkin and sunflower seed flours was prepared and dried at 41.5 °C for 5 h to create a minimally heat-treated blend for a raw food diet. The blend was inoculated with Lactobacillus acidophilus and Fusarium langsethiae to assess the effect of L. acidophilus on Fusarium growth and mycotoxin production. Drying did not affect the content of naturally occurring microorganisms but significantly reduced water activity (p < 0.05) and increased total phenolic content in samples with external microorganisms. Lactobacilli content remained unchanged after drying (4.8 log CFU/g), while F. langsethiae increased by 1.5 log CFU/g. Principal component analysis showed PC1 explained 95.1% of total variance, driven by Fusarium mycotoxin production. A significant difference in total mycotoxin was found between samples with F. langsethiae alone and those with both F. langsethiae and L. acidophilus (p < 0.05). Lactic acid bacteria could reduce fusarium mycotoxin risk in raw food diet mixtures.

This review deals with microbial adhesion to metal-based surfaces and the subsequent biofilm formation, showing that both processes are a serious problem in the food industry, where pathogenic microorganisms released from the biofilm structure may pollute food and related material during their production. Biofilm exhibits an increased resistance toward sanitizers and disinfectants, which complicates the removal or inactivation of microorganisms in these products. In the existing traditional techniques and modern approaches for clean-in-place, electrochemical biofilm control offers promising technology, where surface properties or the reactions taking place on the surface are controlled to delay or prevent cell attachment or to remove microbial cells from the surface. In this overview, biofilm characterization, the classification of bacteria-forming biofilms, the influence of environmental conditions for bacterial attachment to material surfaces, and the evaluation of the role of biofilm morphology are described in detail. Health aspects, biofilm control methods in the food industry, and conventional approaches to biofilm removal are included as well, in order to consider the possibilities and limitations of various electrochemical approaches to biofilm control with respect to potential applications in the food industry.

Resistant bacteria may leave the hospital environment through wastewater. The opportunistic pathogen Pseudomonas aeruginosa, due to its intrinsic resistance to many antibiotics and its ability to easily acquire antibiotic resistance determinants, poses a significant threat to public health. The aim of this study was to evaluate the antibiotic resistance profiles of cultivated P. aeruginosa in untreated hospital effluents in the Czech Republic. Fifty-nine P. aeruginosa strains isolated from six hospital wastewaters were tested for antimicrobial susceptibility through the disc diffusion method against seven antimicrobial agents. Resistance was found in all antibiotics tested. The highest resistance values were observed for ciprofloxacin (30.5%), gentamicin (28.8%), and meropenem (27.2%). The P. aeruginosa isolates also exhibited resistance to ceftazidime (11.5%), amikacin (11.5%), piperacillin-tazobactam (11.5%), and aztreonam (8.5%). Seventeen strains of P. aeruginosa (28.8%) were classified as multidrug-resistant (MDR). The results of this study revealed that antibiotic-resistant strains are commonly present in hospital wastewater and are resistant to clinically relevant antipseudomonal drugs. In the absence of an appropriate treatment process for hospital wastewater, resistant bacteria are released directly into public sewer networks, where they can serve as potential vectors for the spread of antibiotic resistance.

The antimicrobial effect of OKCEL® H-D, a topical, absorbable hemostatic textile prepared from oxidized cellulose, was tested. Testing by dilution and diffusion methods was conducted on a spectrum of 27 select microorganisms, including also antibiotic-resistant strains. OKCEL® H-D showed inhibitory effects on nearly all tested bacteria. In testing using the dilution suspension method, the majority of bacteria showed decrease in cell density by 7–8 orders of magnitude after just 6 h of exposure. For clinical isolates of antibiotic-resistant strains, a reduction occurred after 24 h of exposure. In testing the antimicrobial effects of OKCEL® H-D by the dilution method was least effective on spore-forming Bacillus subtilis, for which no antimicrobial effect was detected after 48 h, and on Mycobacterium smegmatis, for which the number of cells decreased by four orders of magnitude only after 24 h. By the diffusion method, inhibition zones were recorded for nearly all test microorganisms except for Staphylococcus aureus, M. smegmatis, and Listeria monocytogenes. No growth beneath the tested OKCEL® H-D material was recorded, however, even for the latter-named bacteria strains, which attests to its good inhibitory effect.

The aim of the work was to examine the effect of different disinfectants on production trichothecenes (especially of T-2 toxin and deoxynivalenol). Lipophilicity, chemical structure, the presence of bioactive groups and functional groups in their structure modifies biological activity and toxic potency of trichothecenes. For this reason, limits have been established designating maximum levels of mycotoxins in cereals while maintaining proper growing practices. Appropriate nutritive media were prepared with different concentration of tested disinfectants (Desanal A plus, ProCura spray and Guaa-Pool) and were inoculated using Fusarium strains. The density of Fusarium was 105 spores per mililitre. Nutrient media was cultivated at 15 °C and 25 °C for seven days. The strains of Fusarium graminearum CCM F-683 and Fusarium species (isolated from barley) produced quantities of deoxynivalenol. Fusarium poae CCM F-584 and Fusarium species (isolated from malthouse air) produced quantities of T-2 toxin. Desanal A plus prevented Fusarium growth and production of T-2 toxin and deoxynivalenol at the concentration 10%. It is an alkaline disinfectant on the basis of active chlorine and the surfactant that contains ˂5% of NaClO. ProCura spray at the concentration 0.6% proved to be very effective. This disinfectant contains 35% of propan-1-ol and 25% of propan-2-ol. Guaa-Pool at the concentration 0.004% proved to be very effective. It is a polymeric disinfectant with anion surface-acting agent and it contains ˂0.9% of polyhexamethylene guanidine hydrochloride and ˂0.2% of alkyl (C12-C16) dimethylbenzyl ammonium chloride. Lower contentration of disinfectants that not prevented growth of Fusarium caused higher production of T-2 toxin and deoxynivalenol. The contents of T-2 toxin and deoxynivalenol were analyzed by enzyme-linked immunosorbent assay (ELISA) using commercially produced kits (Agra Quant® Deoxynivalenol Test kit and Agra Quant® T-2 toxin Test kit). The experiment showed that the variability in the production of T-2 toxin and deoxynivalenol depended on the Fusarium strain used, concentration of disinfectants and temperature of cultivation.

Aflatoxins are produced as secondary metabolites by A. flavus, A. parasiticus, A. nomius and A. tamarii. The aflatoxin biosynthetic pathway involves several enzymatic steps and genes (apa-2, ver-1) that appear to be regulated by the aflR gene in these fungi. The aim of this work was the detection of aflatoxins by the HPLC method and the ascertainment of factors influencing their production. A. parasiticus CCM F-108, A. parasiticus CCF 141, A. parasiticus CCF 3137 and two isolates A. flavus were used. These toxigenic isolates were recovered from spice (strain 1) and wraps (strain 2). The gene for the production of aflatoxin B1 for each species of fungi was detected using an optimized PCR method. Rhodotorula spp.*, Lactococcus lactis subsp. lactis CCM 1881, Flavobacterium spp. and fungal strain Pythium oligandrum* were tested for inhibition of aflatoxins production and fungal growth. Having used the HPLC detection, various preservatives (propionic acid, citric acid, potassium sorbate) were tested from the viewpoint of their influence on the growth of aflatoxigenic fungi followed by the production of aflatoxins. The growth of A. flavus and A. parasiticus and aflatoxin production in Potato Dextrose Agar supplemented with propionic acid (1000-2000-3000 mg/kg), citric acid (2000-3000-4000 mg/kg) and potassium sorbate (500-800-1000 mg/kg) was tested by Agar Dilution Method. After 72 h of incubation was evaluated growth of fungi, all samples were frozen for later extraction and aflatoxins quantification by HPLC. Effect of peptone and sucrose additions were studied in yeast extract (2%) supplemented with peptone (5-10-15%) or sucrose (15%). Growth inhibition of Aspergillus by Pythium oligandrum was tested on wood surface. As shown, the highest inhibition effect on the aflatoxins production was obtained when propionic acid was applied in concentrations since 1000 mg/kg. A total inhibition of the fungi growth and aflatoxins production was observed in all samples containing peptone in the concentration range tested. Significant limitation of the growth and production of aflatoxins was also observed in the presence of other microorganisms such like Pythium oligandrum and Rhodotorula spp.

The persistence of A. butzleri CCUG 30484 on various surfaces under 32% and 64% relative humidity suspended in physiological saline or nutrient broth to simulate relatively clean or soiled conditions was studied using various isolation techniques. Our study revealed that A. butzleri CCUG 30484 cells were able to survive for a considerable period of time, even after the droplet of suspending medium has been visibly dried. An extended survival on polypropylene coupons at both humidity levels was observed, particularly at soiled conditions.