Antibiotic activity of tigecycline against clinical pathogens by the micro dilution method.

Resistant pathogens are the cause of clinical infections which threatening the patients lives and challenging the health systems through their economic importance. Therefore, new antibacterial agents with a broader spectrum of activity that protect against development of resistance are required. Tigecycline (Tygacil, Wyeth) is a relatively new FDA and EMEA approved glycylcycline antimicrobial with an expanded broad-spectrum activity against pathogens involved in complicated skin and skin structure infections. In this study we evaluated the in vitro activity of tigecycline in comparison to 14 other antibiotics against 182 clinical pathogens by use of the micro dilution method. In overall, tigecycline exhibited the lowest Minimum Inhibitory Concentration (MIC) values in almost all bacteria with a mean of 0.52 ± 1.25mg/L, followed by meropenem and levofloxacin (mean MIC values 1.29 ± 2.52 and 1.45 ± 3.078 mg/L, respectively). MIC50 and MIC90 values of tigecycline were: 0.06 and 0.15 mg/L for E. coli, 0.12 and 1.00 mg/L for Klebsiella sp., 0.12 and 0.85 mg/L for various Enterobacter sp., 1.00 and 8.00 mg/L for Pseudomonas sp., 0.25 and 1.00 mg/L for Acinetobacter sp., 0.06 and 0.12 mg/L for Serratia sp., 0.12 and 0.25mg/L for Staphylococcus aureus, 0.5 and 5.00 mg/L for Streptococcus sp. The MIC values recorded were among the lowest in recent literature for Acinetobacter sp. (included A. baumannii), and comparable to those obtained for Klebsiella, Serratia and Enterobacter indicating that tigecycline has a promising in vitro activity.

Application of novel starter cultures for sourdough bread production.

Sourdough application has been extensively increased in the last years due to the consumers demand for food consumption without the addition of chemical preservatives. Several starter cultures have been applied in sourdough bread making targeting the increase of bread self-life and the improvement of sensorial character. More specific, Lactobacillus acidophilus and Lactobacillus sakei as single and mixed cultures were used for sourdough bread making. Various sourdough breads were produced with the addition of sourdough perviously prepared with 10% w/w L. acidophilus, 10% w/w L. sakei and 5% w/w L. acidophilus and 5% w/w L. sakei at the same time. Various chemical parameters were determined such as lactic acid, total titratable acidity and pH. The results revealed that the produced sourdough bread made with sourdough containing the mixed culture was preserved for more days (12 days) than all the other breads produced in the frame of this study, since it contained lactic acid in higher concentrations. The respective total titratable acidity varied between 10.5 and 11 ml NaOH N/10. The same sourdough bread had a firmer texture, better aroma, flavor and overall quality compared to other sourdough breads examined in this study, as shown by sensory evaluation tests and results obtained through SPME GC-MS analysis, which revealed significant differences among the different bread types.

Antibacterial activities of essential oils from eight Greek aromatic plants against clinical isolates of Staphylococcus aureus.

Aromatic plants have been used widely to extend the shelf life of foods but at the same time research is undergoes for their properties as antibacterial agents in clinical use. Although there are promising results for the antimicrobial properties of various essential oils against environmental or food-isolated strains of Staphylococcus aureus, limited work has been done concerning these properties against clinical isolates of this pathogen. S. aureus is responsible for an increase number of nosocomial infections and at the same time exhibits increased resistance to synthetic agents. In this study, essential oils from eight aromatic plants common in Greece were isolated by hydrodistillation, analyzed by gas chromatography (GC) and GC/mass spectrometry (GC/MS) for their chemical components and tested for their antimicrobial activities against 24 clinical isolates of S. aureus. The methods used were disk diffusion and broth dilution in order to determine the Minimum Inhibitory Concentration (MIC). Our results showed that essential oils from Origanum vulgare and Origanum dictamnus were active against S. aureus when tested by disk diffusion, but exhibited increased MIC values (>256 mg/L) with the dilution method. In contrast, the reference strain NCTC 6571 showed to be extremely sensitive in most of the oils tested (MICs 0.25-32.0 mg/L) and resistant only to the essential oil from Ocimum basilicum. Therefore, there is no evidence of a potential clinical use for those essential oils and further research is needed in order to determine if they could substitute efficiently synthetic antibiotics or, perhaps be used in combination.

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.

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.

Experimental effect of ozone upon the microbial flora of commercially produced dairy fermented products.

Ozone was used to control spoilage microorganisms during the manufacturing of dairy products. Ozone stream was applied onto the surface of freshly filled yoghurt cups just before storage for curd development in order to prevent cross contamination from spoilage airborne microorganisms. Accordingly, brine solution was bubbled with ozone for various periods of time and used for ripening of white (feta type) cheese. Both products were subjected to a continuous monitoring of microbial load and also tested for their sensorial properties. In ozonated yoghurt samples there was a reduction in mould counts of approximately 0.6Logcfu/g (25.1%) by the end of the monitoring period in relation to the control samples. In white cheese ripened with ozonated brine (1.3mg/L O3, NaCl 5%) it seems that ozone treatment during the two months of observation reduced some of the mould load but without offering any advantages over the use of traditional brine (NaCl 7%). However, some sensorial alterations were observed, probably due to the organic load in the brine which deactivates ozone in early stages of application. It is concluded that, if the factors of time and concentration of ozone are configured properly, ozonation could be a promising approach safeguarding the production of some dairy products.

Study of kefir grains application in sourdough bread regarding rope spoilage caused by Bacillus spp.

Sourdough breads prepared with kefir grains resulted in appearance of rope spoilage at the 15th day of bread storage, while the control samples (sourdough breads prepared with wild microflora) were spoiled approximately at the 7th day. Denaturing Gradient Gel Electrophoresis (DGGE) analysis confirmed the above macroscopic observation since Bacillus spp. were detected on sourdough breads prepared with kefir grains at the 15th day of bread storage. The content of organic acids that play synergistic role regarding the enhancement of bread self life was also determined. Lactic acid concentration of sourdough breads prepared with kefir grains were approximately 41-82% higher than the control samples, while acetic acid concentration was about 0.5-1-fold higher respectively. The concentration of some other organic acids studied was also found in higher levels (up to 0.06µg/g) than the control samples. These findings could probably explain the stability of breads prepared with kefir grains against rope spoilage.