The antimicrobial activity of aqueous and ethanolic extracts of 11 Bryophyta species and 9 Marchantiophyta species collected in Latvia was tested against Staphylococcus aureus, Escherichia coli and Bacillus cereus. The extract of Lophocolea heterophylla inhibited the growth of B. cereus, but none of the tested extracts inhibited the growth of E. coli. 70% of bryophyte species demonstrated certain activity in relation to S. aureus. In general, 73% of ethanolic extracts and 39% of aqueous extracts exhibited antibacterial activity against S. aureus. The highest degree of antibacterial activity against S. aureus was shown by the ethanolic extract of Dicranum scoparium and aqueous extracts of Atrichum undulatum and Rhytidiadelphus squarrosus. The bactericidal action was not ascertained. For the first time antimicrobial activity has been proved for three moss species-Eurhynchium angustirete, Rhytidiadelphus squarrosus and Rhodobryum roseum, and for two liverwort species Frullania dilatata and Lophocolea heterophylla. Qualitative and quantitative differences of plant extracts were evaluated by FT-IR spectra.

Variations in the radial growth rate of 24 isolates belonging to ten species of Trichoderma, three isolates of conifer pathogen Heterobasidion annosum s.s. and four isolates of H. parviporum were evaluated by incubation on a solid malt extract medium at a temperature of 4˚C, 15˚C and 21˚C. Trichoderma antagonism against Heterobasidion was investigated in dual culture in vitro. The slowest rate of growth was referable to all seven strains of Heterobasidion spp. All Heterobasidion spp. strains were overgrown by 63% of Trichoderma spp. strains after two weeks at 21˚C and by 33% of strains at 15˚C. 21% of Trichoderma strains did not grow and only four strains belonging to T. koningii, T. viride and T. viridescens demonstrated the ability to completely overgrow Heterobasidion spp. after two weeks incubation at 4˚C. According to the antagonistic efficiency, Trichoderma strains were divided into five groups with an Euclidean distance of 25. The groups contained isolates from different species. It was suggested that selected psychrotrophic fast growing T. viride, T. koningii and T. viridescens strains could be examined in different substrate conditions as suitable antagonist agents for the control of H. annosum and H. parviporum.

Bacterial infections are a prevalent complication after primary viral respiratory infections and are associated with high morbidity and mortality. Antibiotics are widely used against bacterial respiratory pathogens; however, the rise in antibiotic-resistant strains urges us to search for new antimicrobial compounds, including ones that act synergistically with antibiotics. In this study, the minimal inhibitory (MIC) and minimal bactericidal (MBC) concentrations of a polyphenol-rich complex of green propolis, Tabebuia avellanedae bark, and Olea europaea leaf extracts against Staphylococcus aureus, Haemophilus influenzae, and Klebsiella pneumoniae were determined, followed by an analysis of the synergistic effect with clarithromycin, azithromycin, and amoxiclav (875/125 mg amoxicillin/clavulanic acid). A combination of extracts showed activity against all three bacterial strains, with MIC values ranging from 0.78 to 12.5 mg/mL and MBC values from 1.56 to 12.5 mg/mL. The extracts showed synergistic activity with azithromycin and clarithromycin against S. aureus, with clarithromycin against K. pneumoniae, and with all three tested antibiotics against H. influenzae. Synergy with clarithromycin was additionally evaluated in a time-kill assay where the synergistic effects against S. aureus and K. pneumoniae were seen within the first 6 h of incubation. The results show the potential of polyphenol-rich extracts in enhancing the efficacy of antibiotic therapy and indicate their potential to be used in the management of respiratory infections.

The abundance and predominant groups of bacteria, filamentous fungi and yeasts have been studied by culture-dependent microbiological methods in peat probes obtained in two Latvian balneotherapy spa sites, Kemeri and Baldone. Unsterilized peat samples from both the sites contained 5.7-8.1 log bacterial colony-forming units (CFU) and 3.0-5.3 log fungal CFU per gram of dry peat. Isolated species belonged to Alpha-, Beta-, and Gamma-Proteobacteria, Actinobacteria, Clostridia, Bacilli and Flavobacteria as well as to filamentous fungi and yeasts. The composition of microbial population of the peat from both sites shared just four microorganism groups (Bacillus mycoides, Burkholderia cepacia, Streptomyces spp. and Trichoderma spp.) within totally 36 groups identified. No pathogenic bacteria or fungi and no faecal pollution indicators were recovered. Decimal reduction doses for microorganisms in peat samples and radiation sterilization doses of peat for the gamma and electron beam radiation were determined. The highest radiation resistance was observed for B. mycoides and Aureobasidium sp. Gamma-sitosterol was the most abundant hydrophobic organic compound in both peats according to GC-MS data. All the sterilization procedures increased concentration of alkanes, alcohols, and ketones and decreased the amount of fatty acids. Heat sterilization proved to be more preserving for the peat sterols than the radiation sterilization. It is concluded that the heat and radiation sterilization methods induce different changes of the profile of hydrophobic organic compounds of balneological peats, what may lead to different therapeutic effects at their application.

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