C. Voidarou

Antibacterial activity of different honeys against pathogenic bacteria.

To study the antimicrobial activity of honey, 60 samples of various botanical origin were evaluated for their antimicrobial activities against 16 clinical pathogens and their respective reference strains. The microbiological quality of honeys and the antibiotic susceptibility of the various isolates were also examined. The bioassay applied for determining the antimicrobial effect employs the well-agar diffusion method and the estimation of minimum active dilution which produces a 1mm diameter inhibition zone. All honey samples, despite their origin (coniferous, citrus, thyme or polyfloral), showed antibacterial activity against the pathogenic and their respective reference strains at variable levels. Coniferous and thyme honeys showed the highest activity with an average minimum dilution of 17.4 and 19.2% (w/v) followed by citrus and polyfloral honeys with 20.8 and 23.8% respectively. Clinical isolates of Staphylococcus aureus subsp. aureus, Escherichia coli, Salmonella enterica subsp. Enterica, Streptococcus pyogenes, Bacillus cereus and Bacillus subtilis were proven to be up to 60% more resistant than their equal reference strains thus emphasizing the variability in the antibacterial effect of honey and the need for further research.

Physical, chemical and microbiological quality of ice used to cool drinks and foods in Greece and its public health implications.

Ice used for direct human consumption or to preserve foods and cool down drinks can be contaminated with pathogenic microorganisms and may potentially become a vehicle for consumers infection. To evaluate physical, chemical and microbiological quality of commercial ice and ice used for fish and seafood, 100 ice samples collected at 10 different retail points in the region of Epirus were studied. The following microbiological parameters were determined: Total coliforms, fecal coliforms, Salmonella spp., Shigella spp., Yersinia spp., Escherichia coli, Campylobacter sp., Vibrio cholerae, Aeromonas spp., Pseudomonas aeruginosa and Clostridium perfringens. E. coli was detected in 22% and coliforms were detected in 31% of samples. Samples in which coliforms were detected fail to meet the microbiological criteria specified by the drinking water legislation. Aeromonas spp., Shigella spp., Campylobacter sp. and V. cholerae were not detected. Spore forms of C. perfringens were prevalent at 35% and the psychotropic bacteriums P. aeruginosa and Yersinia spp. were found only at three samples each. The presence of large numbers of coliforms as well as of other pathogenic strains suggested that commercial ice and ice used to make cool drinks or in preservation of fish and seafood may represent a potential hazard to the consumer. In view of the results reported herein, it is highly recommended that national regulatory guidelines should be established for the production of ice as long as regular inspections.

Occurrence of Clostridium perfringens from different cultivated soils.

The occurrence of Clostridium perfringens was estimated in 750 samples originated from a variety of soils bearing various bulb crops: Brawnica oderacea (vegetable), Olea europaea, Daucus carota (carote), Solanum tuberosum (potato), Phaseolus vulgaris (green haricot), Beta vulgaris var. rapaceum (beetroot), Cucurbita pepo (squash), Allium cepa (onion), Cucumis sativus (cucumber) and Capsicum annum (pepper). All isolated strains were tested for their antimicrobial activities to amoxicillin, penicillin G, kanamycin, tetracycline, streptomycin, erythromycin, chloramphenicol and metronidazole. When considering the type of the bulb production, it was observed increased number of C. perfringens spore densities in the most undersurface bulb soils. Moreover, C. perfringens spore are likely to occur in particularly large numbers in soil contaminated by fecal matter. Additionally, there is a close relationship between the spore amount and nature of organic content. Presence of C. perfringens was associated with acidic soil. Most of our strains showed resistance to the studied antibiotics applied usually for human and veterinary care. A systematic monitoring of the cultivated soil ecosystems must include bacteriological parameters together with chemical indices of organic pollution in order to obtain information adequate for assessing their overall quality.

Development of human lactic acid (LAB) gastrointestinal microbiota in a Greek rural population

In order to investigate the Lactic Acid Bacteria (LAB) of the gut, fecal samples were collected and analyzed from 120 healthy Greek volunteers ranging from age 1 to age 85, all of whom declared daily consumption of local fermented dairy products. LAB strains were isolated using selective media under aerobic or anaerobic conditions. Identification of the isolates was based on their growth patterns, morphological characteristics, and carbohydrate fermentation profiles. There was no significant difference in the abundance of Lactobacillus brevis, Lactococcus lactis subsp. cremoris, Lactococcus lactis, Lactobacilus paracasei and Bifidobacterium sp., in all samples. Lactobacillus fermentum, Lactobacillus plantarum, Lactococcus casei, Lactococcus pentosus, Lactococcus lactis subsp. lactis, Lactococcus delbrueckii subsp. lactis, Enterococcus casseliflavus, Enterococcus faecalis, Enterococcus faecium, Enterococcus avium and Leuconostoc sp. were also recovered, mainly from the adults and elders rather than the children’s group. Despite the above differences in LAB species observed mostly between the younger and the other two age groups, differences were also observed within all groups, indicating that healthy subjects of all ages are colonized by a diverse lactoflora in terms of total or dominant species.

Microbial ecology of fish species ongrowing in Greek sea farms and their watery environment.

The present study focuses on the bacteriological profile of both watery ecosystem and fishes from different North and Central West Greek fish-farms ongrowing euryhaline fish species. The natural microflora of the fish and the water of their ongrowing units in selected farms were studied for a period of 20 months. The analyzed samples were mainly sea bream (Sparus aurata) 61.3% and sea bass (Dicentrarchus labrax) 24%. In most of the watery ecosystems coming from the different sampling areas, total and fecal coliforms as well as total and fecal streptococci were abundant in all water samples. Enterococcus, Escherichia coli and Pseudomonas were present at a level of 3 logs cfu/100 ml. The anaerobic Clostridium perfringens was found in vegetative (21.3%) and spore forms (13.3%). It is of interest to note that pathogens as Pasteurella piscicida and Vibrio anguillarum were isolated only in a small number of samples. Staphylococcus aureus was detected in 4% of the samples, other Staphylococcus sp. in 29.3%, E. coli in 30.7%, Salmonella sp. in 1.3%, Pseudomonas sp. in 13.3%, Clostridia lec(-) in 49.3%, Bacillus sp. in 38.7%, Vibrio sp. in 18.7%, Lactobacillus and Lactococcus sp. in 36% και 29.3% respectively. Vegetative forms of C. perfringens were detected in 22.7%. Although, our results showed no significant correlations between the sea water and fish microflora, more focus on this bipolar interacting system should be necessary in order to avoid any possible disturbance in the balance of the healthy farming ecosystem with the host organisms.

Chemical and microbiological characterization of artisan inoculants used for the fermentation of traditional dairy products in Epirus area (Greece).

The artisan production of a variety of dairy products is a historical tradition since antiquity, which is still practiced nowadays, in the area of Epirus, (northwestern Greece). The common denominator of these products, regardless of the final form of the end product, is the fermentation of raw milk by the use of dried artisan inoculants made of the dehydrated rumen of small ruminants, mainly lambs. The aim of this research project is to study the microbiological parameters as well as certain technological parameters (chymosin activity and lipolytic activity) of these inoculants. The results revealed a wide biodiversity of microorganisms such as Lactobacilli, Lactococci, Leuconostoc, Pediococci, Streptococci, Bifidobacteria, Enterococci, Clostridia and coliforms. Chymosin activity and lipolytic activity were found to be higher in artisan inoculants than in the commercial ones.

Hygienic quality and antibiotic resistance profile of sliced butchery

In order to investigate the microbiological quality of different meat products on the Greek market, 200 samples were collected from the following preparations: boiled turkey (n=50), boiled pork ham (n=50), smoked turkey (n=50) and smoked pork ham (n=50). In all cold meat preparations Clostridium perfringens vegetative and spore forms, Staphylococcus aureus, Escherichia coli and other Clostridium sp lec(-), as well as Lactobacillus, Bacillus sp. and Salmonella sp. were recovered. For instance Bacillus cereus was present in 6% of the samples. L. monocytogenes, Campylobacter jejuni and Campylobacter coli were rarely present (1-4%) while Yersinia enterocolitica and Campylobacter lari were absent. Differences in the occurrence of S. aureus, Salmonella sp., E. coli and spore forms of C. perfringens in boiled and smoked samples, reflects either the differences in the processing of the foods or could be associated to the extensive handling by the personnel during the purchasing (storage, slicing, wrapping). Antibiotic resistance on specific antibiotics for each pathogen was also studied. A multiresistance antibiotic profile was effective for most bacterial strains, and pronounced resistance profiles were observed for the commonly used antibiotics as ampicillin, penicillin, cephalothin, streptomycin followed by ceftriaxone and gentamycin. Albeit this high observed resistance profile, the tested strains generally conserved their susceptibility to amikacin, aztreonam, chloramphenicol and tylosin conserved an almost absent resistance. Antibiotics commonly used for therapeutic purposes, as well as antibiotics added to feed stuff of animals for increasing animal flesh production should contribute to the extensive spreading of antibiotic resistance in food and the environment. Systematically monitoring of the microbiological quality of cold butchery preparations must be done, in order to preserve food quality, optimizing the processing and elaboration methods of the product and safeguard the public health.

Biochemical and antimicrobial profile of Enterococcus faecium and E. faecalis isolated from traditional dairy products and infant intestinal microbiota

Abstract Background: Unpasteurized fermented milk is used for the production of traditional dairy products in certain rural areas of Greece. Methods: In an attempt to search for candidate beneficial probiotic strains of Enterococcus faecium and Enterococcus faecalis, isolates recovered from traditional dairy products and from faeces of infants fed with such products were evaluated regarding their antimicrobial activity and their standard biochemical profile. Results: Almost all tested strains showed resistance to a pH range from 3.0 to 6.5, tolerance to bile acid within 24 h and resistance to phenol. Field isolates of E. faecalis and E. faecium presented higher antimicrobial activity against classic food pathogenic serovars of Salmonella enteritica (S. typhi, S. typhimurium, S. ancona, S. enteritidis) compared with reference strains. Conclusion: The implementation of beneficial enterococcal strains in the production of fermented dairy products is part of technological process in constant development aimed at obtaining food products of increased quality and safety.

Biodiversity and Microbial Resistance of Lactobacilli Isolated From the Traditional Greek Cheese Kopanisti

Kopanisti is a Greek artisan cheese produced from raw milk in the island of Mykonos, Greece. The milk is left to rest for 12–24 h and then the rennet is added. After its formation the curd is left to drain for 2–3 days and is ready either for consumption (as tyrovolia fresh cheese), or with the addition of extra salt, the curd is left to ripen through further fermentation and surface development of Penicillium fungi, aprocess leading to the production of the traditional Greek cheese Kopanisti. From 120 samples of kopanisti, 574 Lactobacillus strains were isolated, distributed in 17 species (16 of them isolated from tyrovolia as well). Strains from 15 species were found resistant or multiresistant against 15 antimicrobial agents, representing all categories of antibiotics. Analysis revealed that the resistance was moderated during ripening of the curd from tyrovolia to Kopanisti. Resistance against penicillin G, ampicillin/sulbactam, clindamycin, chloramphenicol, streptomycin, trimethoprim, metronidazole, vancomycin, teichoplanin, and quinupristin/dalvopristin was significantly enhanced, while the resistance against ampicillin, erythromycin, oxytetracycline, gentamycin, and fucidic acid was significantly reduced. These changes during ripening suggest that resistance to antimicrobials is a dynamic process subjected to environmental factors. The biodiversity of isolated Lactobacillus strains is impressive and explains the exquisite sensorial characteristics of the cheese. However, the extent of the resistance is alarming.