Acta Microbiologica Bulgarica

134-148

Authors: Galabov, A. S., Nikolaeva-Glomb, L., Stoyanova, A., Nikolova, I., Petrov, N., Vilhelmova-Ilieva, N., Mukova, L., Vassileva-Pencheva, R., Salama, Z.

Forty-three organosilicon class of compounds were tested for antiviral activity using a wide scope screening program in vitro (in cell cultures) including eight model strains of viruses belonging to seven taxonomic groups including causative agents of infections in which applications of chemotherapy is indicated. The results obtained demonstrated a marked activity of di(hexadecanoyloxy)diphenylsilan (compound 27) only against human cytomegalovirus (SI = 30.9). A marked activity toward this virus at a low m.o.i. was recorded also by 1-o-dimethyl(octadecyl)silyl-(2,3,4,6-o-tetraacetyl--D-glucopyranosid) (compound 20). Small to borderline effect against this virus was found by silanes 2, 7, 15, 19 and 34, at silanes 2, 3 and 25 toward influenza virus A(H3N2) and at silane 9 versus vaccinia virus. As concerns the cytotoxicity it was established a strong variation towards different cell cultures used, the higher susceptibility of the HEp-2 cells been recorded.

153-159

Authors: Tsvetanova, Z. G., Najdenski, H. M.

The present study aimed to assess the potential of three enteropathogenic bacteria to form single-species drinking water-associated biofilms and their capacity to attach to and survive in the multispecies bacterial biofilms, pre-existing on polypropylene and polyethylene pipe surfaces, in 63-day batch experiments with real drinking water. Dynamics of the biofilm formation process of the tested enteropathogens was studied, and the influence of the inter-species interactions and the type of polymer pipe materials as surface for attachment were clarified. It was found out, that the biofilm formation potential was a specific characteristic of each tested enteropathogen and was influenced by the pipe material type. The single-species- and multispecies biofilms of each enteropathogen differed in the culturable cells density and dynamics. The pathogen attachment to the bacterially pre-colonized surfaces was more significant compared to the non-colonized ones. The culturable S. dublin 1953 and Y. enterocolitica O:8 8081 cells persisted in the biofilms in a lower number than the E. coli O157 cells. The number of culturable pathogen cells in the single-species biofilms decreased faster than in the mixed bacterial biofilms.

165-173

Authors: Satchanska, G., Stefanova, P., Dicheva, V., Vatcheva-Dobrevska, R., Tsenova, M.

Cheese plays a significant role in human nutrition, being one of the most popularready-to-eat foods produced worldwide. Cheese is rich in microbiota and more than 400 species of LAB, Gram (+) and Gram (-) bacteria, yeasts and molds have been identified in it so far. The rich nutritional content of cheese also favors the development of foodborne pathogenic bacteria. The aim of our study was to investigate the microbiota in commercially branded full-cream yellow cheese with a high market share as well as to search for pathogenic bacteria in it. An amount of different bacterial groups in 1 g of cheese was assessed using SPS agar (Clostridium), MCA agar (Staphylococcus), KEAA (fecal enterococci), YGS (yeasts), Candida agar (Candida spp.) and Nutrient broth (total number). Randomly picked isolates were subcultured on Columbia agar with 5% sheep blood; McConkey agar (BD, USA); Sabouraud and BBL CHROMagar Candida (BD, USA). Identification of isolates was carried out using Crystal (BD, USA) system; VITEK 2, bioMerieux, France, API 20 C AUX Candida (bioMerieux, France). Our results revealed that the total number of bacteria in the investigated sample was 6.9x105. Cheese was negative for clostridia and coliforms. It was positive for yeasts but within the standard limit – 2x102 CFU/g, including Candida spp. - 2x102 CFU/g. Alarmingly, a high amount of fecal enterococci - 1.5x105 CFU/g and staphylococci – 2x104 CFU/g was detected. Bacteria isolated from the cheese sample were further identified as Staphylococcus simulans, Enterococcus avium, Candida krusei and Cryptococcus neoformans, and Staphylococcus simulans, associated with endocarditis of chickens in humans. A putative reason for the staphylococcal contamination of cheese could be mastitis in the cows whose milk was processed. Another isolate, Enterococcus avium, was reported to be responsible for bacteremia and brain abscesses in humans and is known to be resistant to antibiotics. Yeasts, including Candida spp., complied with the standard but even at a small amount they could be harmful to immunocompromised consumers, children or pregnant women. Pathogens as Candida krusei and Cryptococcus neoformans were detected in the investigated sample.

180-186

Authors: Stoyanova, M. I., Ganeva D. G., Petrov, N. M., Bogatzevska, N. S.

Since 2014, an unusual appearance of tomato seeds (Solanum lycopersicum) has been observed. The seeds were produced from local tomato genotypes from Bulgaria without visible symptoms of disease. The seeds exhibited small or large brown-grey spots on the surface that affected also the deeper layers. The most affected seeds lacked germinating ability or were unable to produce normal seedlings. Bacteria were derived from exudates, seed coat, endosperm, and embryo. Several tests were carried out to investigate pathogenicity - inoculation of seedlings, seeds, and plants. All isolates were identified as Stenotrophomonas maltophilia by BiologTM and after sequencing of the 16S rRNA gene region. S. maltophilia was found to be the sole causal agent of the disease in seeds. This is the first report of S. maltophilia causing disease of tomato seeds.