Synergistic antimicrobial activity of oregano and thyme thymol essential oils against Leuconostoc citreum in a laboratory medium and tomato juice.

This study was done to identify combinations of essential oils (EOs) that elicit synergistic antimicrobial effects against Leuconostoc citreum, a spoilage bacterium in vegetable and fruit juices. Twenty-four EOs were tested for antimicrobial activity against L. citreum using an agar well diffusion assay. Ten EOs showed relatively strong antimicrobial activity. Among those, cinnamon bark, oregano, and thyme thymol EOs showed the strongest activity (minimal inhibitory concentration = 1.25 µL/mL). It was confirmed that a combination of oregano and thyme thymol EOs had a synergistic antimicrobial activity (fractional inhibitory concentration index = 0.3750) using a checkerboard assay. This combination also had a synergistic antimicrobial activity against L. citreum in tomato juice. An initial population of L. citreum in tomato juice (5.3 log CFU/mL) increased to ≥ 8.6 log CFU/mL within 48 h at 15 °C and 24 h at 25 °C. Populations reached 6.8-7.2 log CFU/mL in tomato juice containing either 0.156 mL/mL oregano or thyme thymol. However, in the presence of both EOs (0.156 µL/mL in total), populations of L. citreum were significantly lower (5.7-6.5 log CFU/mL) (P ≤ 0.05). Findings will be useful when developing non-thermal food preservation technologies to increase the shelf-life of juices and other foods not containing synthetic preservatives.

A therapeutic benefit of daptomycin against glycopeptide-resistant gram-positive cocci bloodstream infections under neutropenia.

Antibiotic-resistant infections remain to be a major issue for all over the world. Although appropriate diagnosis and rapid treatment initiation are crucially important particularly in immunocompromised patients, selection of antibiotics without identification of causative bacteria is often challenging. A 44-year-old woman with acute myeloid leukemia (AML) under myelosuppression suffered from teicoplanin-resistant gram-positive cocci bacteremia. Taking severe neutropenia due to chemotherapy and glycopeptide-resistance into account, teicoplanin was empirically substituted with daptomycin, which led to prompt defervescence. This microorganism later turned out to be Leuconostoc lactis (L. Lactis), and daptmycin was continued to use based on antimicrobial susceptibility tests. As a result, empiric use of daptomycin successfully controlled glycopeptide-resistant gram-positive cocci bacteremia under neutropenia. This is the first report of daptomycin treatment for L. lactis bacteremia in a patient with AML under neutropenia. Our findings suggest that daptomycin would be a suitable treatment option for glycopeptide-resistant gram-positive cocci bloodstream infections, especially in myelosuppressive patients.

Effect of Initial Headspace O2 Level on the Growth and Volatile Metabolite Production of Leuconostoc Mesenteriodes and the Microbial and Sensorial Quality of Modified Atmosphere Packaged Par-Fried French Fries.

This study evaluated the effect of residual O2 level (0% to 5%) on microbial growth and volatile metabolite production on par-fried French fries packaged in a modified atmosphere with 60% CO2 (rest N2 ) at 4 °C. The results obtained showed that the initial headspace (IH) O2 level had an effect on growth of Leuconostoc mesenteroides on French fry simulation agar, whereby growth was slightly faster under 5% O2 . In terms of quantity, ethanol, 2-methyl-1-propanol, and dimethyl disulphide were the most significant volatile metabolites produced by L. mesenteroides. The production of ethanol by L. mesenteroides was highest on simulation agar packaged under low IH O2 levels (0% to 1%), indicating that the fermentative metabolism was induced under these conditions. In agreement with the results observed on the simulation medium, growth of native lactic acid bacteria was faster under an IH O2 level of 5%. In addition, ethanol, 2-methyl-1-propanol, and dimethyl disulphide were also quantitatively the most important volatile metabolites. However, in contrast, greater quantities of ethanol and dimethyl disulphide were produced on par-fried French fries packaged under 5% O2 . This was attributed to the limited growth of the native flora on the par-fried French fries under residual O2 levels of 0% and 1%. Although some significant differences (P < 0.05) occurred between the French fries packaged in 0%, 1%, and 5 % residual O2 during storage, all products were considered to be acceptable for consumption. The results of this study can be used to optimize the shelf-life of packaged chill stored potato products.

Inhibition of algal bromophenols and their related phenols against glucose 6-phosphate dehydrogenase.

A novel bromophenol, n-butyl 2,3-dibromo-4,5-dihydroxybenzyl ether, and known bromophenols were isolated from Rhodomelaceae algae as glucose 6-phosphate dehydrogenase (G6PD) inhibitors. Among them, bromophenol dimers showed stronger inhibitory activity against Leuconostoc mesenteroides and Saccharomyces cerevisiae G6PDs than the corresponding monomers. The dibenzyl ether-type dimers had lower IC50 values than the diarylmethane-type dimers against L. mesenteroides G6PD among the bromophenols examined. In contrast, the inhibitory activities of diarylmethane-type dimers against S. cerevisiae G6PD were stronger than those of dibenzyl ether-type dimers. Especially, 3-bromo-2-(2,3-dibromo-4,5-dihydroxybenzyl)-4,5-dihydroxybenzyl methyl ether selectively inhibited S. cerevisiae G6PD compared to L. mesenteroides G6PD.

[Antimicrobial Properties of Eremoxylarin A Produced by Ascomycete of Sordariomycetes in Submerged Culture].

The fungal strain INA 01108 producing antibiotic substances with broad spectrum of antibacterial activity was isolated from the natural environment. By the morphological characteristics and DNA analysis it was shown to belong to Ascomycetes of Sordariomycetes. In submerged culture the strain produced at least four antibiotics. The major component of them was identified as eremophilane-type sesquiterpene eremoxylarin A. Eremoxylarin A is effective in vitro against grampositive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin group glycopeptide antibiotics resistant Leuconostoc mesenteroides VKPM B-4177. The efficacy and toxicity of eremoxylarin A was determined on a murine staphylococcal sepsis model. The dose of 6.25 mg/kg provided 100% recovery and survival of the animals, while the dose of 3.12 mg/kg was close to the ED50. The chemical structure of eremoxylarin A allows to modify the antibiotic and such studies may be relevant to design a less toxic derivative without loss of the valuable antimicrobial properties.

Antimicrobial activity of a neem cake extract in a broth model meat system.

This work reports on the antimicrobial activity of an ethyl acetate extract of neem (Azadirachta indica) cake (NCE) against bacteria affecting the quality of retail fresh meat in a broth model meat system. NCE (100 µg) was also tested by the agar disc diffusion method. It inhibited the growth of all tested microorganisms. The NCE growth inhibition zone (IZ) ranged 11.33-22.67 mm while the ciprofloxacin (10 µg) IZ ranged from 23.41-32.67 mm. There was no significant difference (p ≤ 0.05) between the antimicrobial activity of NCE and ciprofloxacin vs. C. jejuni and Leuconostoc spp. The NCE antibacterial activity was moreover determined at lower concentrations (1:10-1:100,000) in micro-assays. The percent growth reduction ranged from 61 ± 2.08-92 ± 3.21. The higher bacterial growth reduction was obtained at 10 µg concentration of NCE. Species-specific PCR and multiplex PCR with the DNA dye propidium monoazide were used to directly detect viable bacterial cells from experimentally contaminated meat samples. The numbers of bacterial cells never significantly (p ≤ 0.05) exceeded the inocula concentration used to experimentally contaminate the NCE treated meat. This report represents a screening methodology to evaluate the antimicrobial capability of a herbal extract to preserve meat.

Influence of epigallocatechin gallate and phenolic compounds from green tea on the growth of Oenococcus oeni.

AIMS: To investigate the effect of phenolic compounds on the growth of Oenococcus oeni. METHODS AND RESULTS: Oenococci are usually grown in media often supplemented with complex additives such as tomato juice. In order to improve our knowledge about the growth requirements of oenococci, we added several juices and leaf extracts such as green tea to the culture media and screened them for growth-stimulating substances to substitute complex supplements such as juices by more defined components. We found that also green tea could cause a growth stimulation of Oenococcus oeni strain B2. CONCLUSIONS: Further experiments showed that the stimulating effect was as a result of the phenolic compounds of green tea, especially epigallocatechin gallate (EGCG). On the other hand, EGCG could also inhibit the growth of O. oeni strain B2 just depending on its concentration. SIGNIFICANCE AND IMPACT OF THE STUDY: Individual catechins should have a minor influence on the growth of oenococci during wine making as their concentration in grapes is <30 mg kg(-1) grape. Whether there is a synergistic effect of the different catechins in wine has to be investigated.

Leuconostoc species-associated endocarditis.

Leuconostoc species are gram-positive cocci belonging to the Streptococcaceae family. The species were generally regarded as nonpathogenic and of little importance in clinical microbiology until several occurrences of Leuconostoc infections were reported in the literature. Unlike many gram-positive bacteria, Leuconostoc species commonly demonstrate high-level resistance to vancomycin, with preserved sensitivity to most other antibacterial agents. We describe a 55-year-old man who developed endocarditis caused by Leuconostoc species sensitive to vancomycin. The patient received an aortic valve replacement and was treated with penicillin G and gentamicin; he experienced no further complications.

Use of lemon extract to inhibit the growth of malolactic bacteria.

The potential use of lemon extract as a natural preservative to inhibit the growth of Oenococcus oeni and Lactobacillus plantarum, microorganisms involved in the malotactic fermentation of wine, was studied. Growth tests were run at 30 degrees C using laboratory media. Carbon dioxide concentration in the vial headspace was used as metabolic activity index of the investigated microorganisms. The MIC and the noninhibiting concentration (NIC) were calculated for each microorganism. Results suggest that lemon extract was active on each phase of the growth cycle for the tested microorganisms. It was also shown that lemon extract exhibits a nonlinear dose-related inhibitory effect on microbial growth. In particular, the active compound could be added at concentrations slightly higher than the NIC levels in order to appreciably slow down the microbial growth rate as well as to reduce the maximum microbial growth level.

Both arginine and fructose stimulate pH-independent resistance in the wine bacteria Oenococcus oeni.

The wine bacteria Oenococcus oeni has to cope with harsh environmental conditions including an acidic pH, a high alcoholic content, and growth inhibitory compounds such as fatty acids, phenolic acids and tannins. So how can O. oeni bacteria naturally present on the surface of grape berries acquire a natural resistance that will alleviate the effect of wine stresses? One mechanism displayed by O. oeni and many other bacteria against the damaging effects of acid environments is arginine consumption through the arginine deiminase pathway. Various studies have shown that the bacterial protection conferred by arginine depends on the rise in pH associated with ammonia production. However, many experimental results disagree with this point of view. The aim of this study was to clarify the protective effect of arginine on O. oeni stress adaptation. Is it only by increasing the pH through ammonia production that this effect is triggered, or does stimulation of appropriate cellular responses play an additional role? This study shows that: (a) arginine in combination with fructose triggers the expression of a subset of genes which are also stress-responsive; (b) cultivation of O. oeni in a fructose- and arginine-supplemented medium prior to wine exposure protects bacteria against subsequent wine shock, and (c) this acquired stress resistance is independent of pH.

[Influence of vancomycin by venous route on salivary and fecal aerobic floras]. / Influence de la vancomycine par voie veineuse sur les flores aérobies salivaires et fécales.

An IV vancomycin treatment induces a reduction of Gram positive cocci (Staphylococcus, Enterococcus) of the aerobic salivary and fecal flora. Some of these strains persisted during and after treatment, but remained susceptible to vancomycin. Others isolated Gram positive cocci were resistant to vancomycin before and after treatment. They were identified as Pediococcus sp., and Leuconostoc sp. There is a reduction of the number of Gram positive cocci, without increase of Gram negative rods, Lactobacillus, or Candida which are always resistant to vancomycin.

Assay for citrovorum factor (NSC-3590) in the presence of methotrexate (NSC-740).

Treatment of certain malignancies with high-dose methotrexate/citrovorum factor rescue has recently been adopted as an effective regimen. A microbiologic assay capable of detecting citrovorum factor in the presence of massive amounts of methotrexate has been developed using a strain of Pediococcus cerevisiae resistant to methotrexate. The assay described in this paper is an inexpensive and rapid method of studying the distribution kinetics of citrovorum factor.

Growth stimulants in plant extracts for Leuconostoc citrovorum.

The growth of Leuconostoc citrovorum ML 34, an isolate associated with the malo-lactic fermentation of wine, was stimulated in part by grape, orange, cabbage, and tomato juices. The stimulatory activity of tomato serum was associated with the carbohydrate fraction. Further purification of the fraction showed that fructose was the factor responsible for initiating growth. In addition to fructose, the organism required CO(2) for establishing growth. Saturated CO(2) atmosphere and catalytic amounts of fructose served as substitutes for plant extracts in a complex glucose medium.