Comparison of bacteriostatic and bactericidal activity of 13 essential oils against strains with varying sensitivity to antibiotics

Aims:  To compare the bacteriostatic and bactericidal activity of 13 chemotyped essential oils (EO) on 65 bacteria with varying sensitivity to antibiotics.
Methods and Results:  Fifty-five bacterial strains were tested with two methods used for evaluation of antimicrobial activity (CLSI recommendations): the agar dilution method and the time-killing curve method. EO containing aldehydes ( Cinnamomum verum bark and Cymbopogon citratus ), phenols ( Origanum compactum , Trachyspermum ammi , Thymus satureioides , Eugenia caryophyllus and Cinnamomum verum leaf) showed the highest antimicrobial activity with minimum inhibitory concentration (MIC) <2% (v/v) against all strains except Pseudomonas aeruginosa . Alcohol-based EO ( Melaleuca alternifolia , Cymbopogon martinii and Lavandula angustifolia ) exhibited varying degrees of activity depending on Gram status. EO containing 1·8-cineole and hydrocarbons ( Eucalyptus globulus , Melaleuca cajeputii and Citrus sinensis ) had MIC_90% ≥ 10% (v/v). Against P. aeruginosa , only C. verum bark and O. compactum presented MIC ≤2% (v/v). Cinnamomum verum bark, O. compactum , T. satureioides , C. verum leaf and M. alternifolia were bactericidal against Staphylococcus aureus and Escherichia coli at concentrations ranging from to 0·31% to 10% (v/v) after 1 h of contact. Cinnamomum verum bark and O. compactum were bactericidal against P. aeruginosa within 5 min at concentrations <2% (v/v).
Conclusions:  Cinnamomum verum bark had the highest antimicrobial activity, particularly against resistant strains.
Significance and Impact of the Study:  Bacteriostatic and bactericidal activity of EO on nosocomial antibiotic-resistant strains.     

Control of Aspergillus section Flavi growth and aflatoxin accumulation by plant essential oils

Aims:  The antifungal effect of Pimpinella anisum (anise), Pëumus boldus (boldus), Mentha piperita (peppermint), Origanum vulgare (oregano) and Minthosthachys verticillata (peperina) essential oils against Aspergillus section Flavi (two isolates of Aspergillus parasiticus and two isolates of Aspergillus flavus ) was evaluated in maize meal extract agar at 0·982 and 0·955 water activities, at 25°C.
Methods and Results:  The percentage of germination, germ-tube elongation rate, growth rate and aflatoxin B₁ (AFB₁) accumulation at different essential oils concentrations were evaluated. Anise and boldus essential oils were the most inhibitory at 500 mg kg⁻¹ to all growth parameters of the fungus. These essential oils inhibited the percentage of germination, germ-tube elongation rate and fungal growth. AFB₁ accumulation was completely inhibited by anise, boldus and oregano essential oils. Peperina and peppermint essential oils inhibited AFB₁ production by 85–90% in all concentrations assayed.
Conclusions:  Anise and boldus essential oils could be considered as effective fungitoxicans for Aspergillus section flavi .
Significance and Impact of the Study:  Our results suggest that these phytochemical compounds could be used alone or in conjunction with other substances to control the presence of aflatoxigenic fungi in stored maize.     

Antimicrobial activity of essential oils and structurally related synthetic food additives towards Clostridium perfringens

Aims:  To assess the potential of essential oils and structurally related synthetic food additives in inhibiting the growth of Clostridium perfringens for the control of necrotic enteritis in chickens.
Methods and Results:  The antimicrobial activity of essential oils/compounds was measured by determining the inhibition of bacterial growth. Thirty-three of 66 oils/compounds exhibited ≥80% inhibition. Seven with the highest potency were further studied. The oils/compounds had MIC₉₅ values between 167 and 425  μ g ml⁻¹. Most of them were tolerant to low pH (2·0) and exhibited minor or no inhibition of Lactobacillus isolates from the chicken intestine. When mixed with chicken ileal digesta, the oils/compounds retained their efficacy against C . perfringens , but had little effect on the total number of lactobacilli and anaerobic bacteria in the digesta.
Conclusions:  Some essential oils/compounds demonstrated good potential in controlling C . perfringens .
Significance and Impact of the Study:  This study has identified candidates of essential oils/compounds for in vivo studies for the control of necrotic enteritis in chickens.     

Production and partial characterization of lipases from a newly isolated Penicillium sp. using experimental design

Aims:  The objective of this work was to investigate the lipase production by a newly isolated Penicillium sp . , using experimental design technique, in submerged fermentation using a medium based on peptone, yeast extract, NaCl and olive oil, as well as to characterize the crude enzymatic extracts obtained.
Methods and Results:  Lipase activity values of 9·5 U ml⁻¹ in 96 h of fermentation was obtained at the maximized operational conditions of peptone, yeast extract, NaCl and olive oil concentrations (g l⁻¹) of 20·0, 5·0, 5·0 and of 10·0 respectively. The partial characterization of crude enzymatic extract obtained by submerged fermentation showed optimum activity at pH range from 4·9 to 5·5 and temperature from 37°C to 42°C. The crude extract maintained its initial activity at freezing temperatures up to 100 days.
Conclusions:  A newly isolated strain of Penicillium sp . used in this work yielded good lipase activities compared to the literature.
Significance and Impact of the Study:  The growing interest in lipase production is related to the potential biotechnological applications that these enzymes present. New lipase producers are relevant to finding enzymes with different catalytic properties of commercial interest could be obtained, without using genetically modified organisms (GMO).     

Polyaluminum chloride-enhanced concentration efficiency of poliovirus and f2 phage from sewage water

Aims:  To enhance the recovery of f₂ bacteriophage and poliovirus by an established method based on the adsorption to and elution from positively-charged Al(OH)₃-treated silica gel.
Methods and Results:  Polyaluminum Chloride (PAC) was added to water samples to neutralize the negatively charged materials, which can reduce virus recovery by providing a competing adsorption mode on the media surface. Using this improved process (PAC 30 mg l⁻¹, pH 6·5, temperature 20∼30°C), the recoveries of Poliovirus I and f₂ from small-volume sewage (100 ml) were 110·76 ± 36·0% and 92·06 ± 8·65%, respectively ( P  < 0·05 vs. traditional methods). Recovery from a 20-L volume of sewage averaged 85·65 ± 4·43% for f₂ and 88·73 ± 9·76% for poliovirus, significantly higher than the recoveries in the traditional methods ( P  < 0·05).
Conclusions:  PAC could enhance concentration efficiency of poliovirus and f₂ phage from sewage water.
Significance and Impact of the Study:  This method should significantly improve the recovery of viruses from sewage.     

Detection of infectious rotavirus in naturally contaminated source waters for drinking water production

Aims:  To assess chlorine susceptibility of Legionella pneumophila grown from two amoebic hosts, Acanthamoeba castellanii and Hartmannella vermiformis .
Methods and Results:  After being released from amoebae, Leg. pneumophila were chlorinated at 2 and 5 mg l⁻¹ for 5 min–24 h. Bacterial culturability and cytoplasmic membrane deterioration were quantified by culture assay on BCYEα agar and BacLight stains coupled with a fluorescent microscope, respectively. Chlorination reduced the culturability of Leg. pneumophila by 2·93–4·59 log CFU ml⁻¹ and damaged cellular membrane by 53·8–99·2%. Moreover, cells released from H. vermiformis exhibited significantly lower degrees in culturability reduction ( P  = 0·0008) and membrane deterioration ( P  < 0·0001) when compared with those from A. castellanii . The amoebic genus is the most significant parameter affecting cytoplasmic membrane integrity of chlorinated Legionella ( P  < 0·0001), followed by free chlorine concentration ( P  = 0·042).
Conclusions:  Legionella pneumophila replicated from H. vermiformis possess greater chlorine resistance than the cells from A. castellanii .
Significance and Impact of the Study:  This study shows the heterogeneity of amoebae-grown Leg. pneumophila in chlorine susceptibility, which should be considered in the control of legionellae proliferation, particularly in the systems where H. vermiformis is dominant, e.g. hot water plumbing.     

Inhibition of quorum sensing regulated bacterial functions by plant essential oils with special reference to clove oil

Aims:  To evaluate quorum sensing (QS) inhibitory activity of plant essential oils using strains of Chromobacterium violaceum (CV12472 and CVO26) and Pseudomonas aeruginosa (PAO1).
Methods and Results:  Inhibition of QS-controlled violacein production in C. violaceum was assayed using disc diffusion and agar well diffusion method. Of the 21 essential oils, four oils showed varying levels of anti-QS activity. Syzygium aromaticum (Clove) oil showed promising anti-QS activity on both wild and mutant strains with zones of pigment inhibition 19 and 17 mm, respectively, followed by activity in cinnamon, lavender and peppermint oils. The effect of clove oil on the extent of violacein production was estimated photometrically and found to be concentration dependent. At sub-MICs of clove oil, 78·4% reduction in violacein production over control and up to 78% reduction in swarming motility in PAO1 over control were recorded. Gas chromatography–mass spectrometry analysis of clove oil indicated presence of many phytocompounds. Eugenol, the major constituent of clove oil could not exhibit anti-QS activity.
Conclusions:  Presence of anti-QS activity in clove oil and other essential oils has indicated new anti-infective activity. The identification of anti-QS phytoconstituents is needed to assess the mechanism of action against both C. violaceum and Ps. aeruginosa .
Significance and Impact of the study:  Essential oils having new antipathogenic drugs principle because of its anti-QS activity might be important in reducing virulence and pathogenicity of drug-resistant bacteria in vivo .     

Bovicin HC5 reduces thermal resistance of Alicyclobacillus acidoterrestris in acidic mango pulp

Aims:  To test the effect of bovicin HC5 against vegetative cells and endospores of Alicyclobacillus acidoterrestris DSMZ 2498 in synthetic media and in acidic mango pulp.
Methods and Results:  Alicyclobacillus acidoterrestris was grown in synthetic medium at 40°C and pH 4·0. The effect on vegetative cells was assayed by adding bovicin HC5 to synthetic medium (40–160 AU ml⁻¹) or to mango pulp (100 AU ml⁻¹) at various pH values and determining the effect on growth (OD_600nm) and viable cell number, respectively. The effect of bovicin HC5 on spore germination and thermal sensitivity of A. acidoterrestris was tested in mango pulp (pH 4·0) containing 80 AU ml⁻¹ of bovicin HC5. Bovicin HC5 was bactericidal against vegetative cells of A. acidoterrestris at different pH values and showed sporicidal activity against endospores of this bacterium. When spores of A. acidoterrestris were heat treated in the presence of bovicin HC5, D -values decreased 77% to 95% compared to untreated controls at temperatures ranging from 80 to 95°C.
Conclusion:  Bovicin HC5 was bactericidal and sporicidal against A. acidoterrestrsi DSMZ 2498.
Significance and Impact of the Study:  These results indicated that bovicin HC5 has potential to prevent spoilage of acidic fruit juices by thermocidophilic spore-forming bacteria.     

Isolation of alkali-tolerant benzene-degrading bacteria from a contaminated aquifer

Aims:  To isolate benzene-degrading strains from neutral and alkaline groundwaters contaminated by benzene, toluene, ethylbenzene, xylenes (BTEX) from the SIReN aquifer, UK, and to test their effective pH range and ability to degrade TEX.
Methods and Results:  The 14 isolates studied had an optimum pH for growth of 8, and could degrade benzene to below detection level (1  μ g l⁻¹). Five Rhodococcus erythropolis strains were able to metabolize benzene up to pH 9, two distinct R. erythropolis strains to pH 10, and one Arthrobacter strain to pH 8·5. These Actinobacteria also degraded benzene at least down to pH 5·5. Six other isolates, a Hydrogenophaga and five Pseudomonas strains, had a narrower pH tolerance for benzene degradation (pH 6 to 8·5), and could metabolize toluene; in addition, the Hydrogenophaga and two Pseudomonas strains utilized o- , m- or p- xylenes. None of these strains degraded ethylbenzene.
Conclusions:  Phylogenetically distinct isolates, able to degrade BTX compounds, were obtained, and some degraded benzene at high pH.
Significance and Impact of the Study:  High pH has previously been found to inhibit in situ degradation of benzene, a widespread, carcinogenic groundwater contaminant. These benzene-degrading organisms therefore have potential applications in the remediation or natural attenuation of alkaline waters.     

Effect of selected antimicrobial compounds on the radiosensitization of Salmonella Typhi in ground beef

Aims:  In this study, we extended our previous work to determine the efficiency of antimicrobial compounds in increase of relative radiosensitivity of Salmonella Typhi in medium fat ground beef (23% fat) by testing 41 different essential oils (EOs), oleoresins and food sauces.
Methods and Results:  Ground beef samples inoculated with Salmonella Typhi (10⁶ CFU g⁻¹ ) were treated with each antimicrobial compound at a concentration of 0·5% (w/w). Then, the samples (25 g each) were packaged under air and irradiated in a ⁶⁰Co irradiator at doses from 0 to 1·75 kGy. Radiosensitivity was evaluated by calculating relative radiation sensitivity, defined as the ratio of radiation D ₁₀ value in the absence/presence of antimicrobial compound.
Conclusions:  Depending on the compound tested, the addition of antimicrobial compound decreased the D ₁₀ value of Salmonella Typhi, resulting in an increase of the radiation sensitivity up to more than four times. Among these antimicrobial compounds, Chinese cinnamon EO, clove EO and trans -cinnamaldehyde were most effective to increase the radiosensitivity of Salmonella Typhi in ground beef.
Significance and Impact of the Study:  These observations demonstrate that some active compounds can function as radiosensitizers of Salmonella Typhi.     

Methods for the recovery of a model virus from healthcare personal protective equipment

Aims:  To develop methods for recovering a model virus (bacteriophage MS2) from healthcare personal protective equipment (PPE).
Methods and Results:  Nine eluents were evaluated for recovery of infectious MS2 from PPE: 1·5% beef extract (BE) pH 7·5 with and without 0·1% Tween 80, 1·5% BE pH 9·0 with and without 0·1% Tween 80, 3% BE pH 7·5 with and without 0·1% Tween 80, 3% BE pH 9·0 with and without 0·1% Tween 80 and PBS with 0·1% Tween 80. Methods were applied to experimentally contaminated PPE. Elution followed by two-step enrichment assay could recover virus inputs as low as 1·5 log₁₀, and could recover >90% of inoculated virus from used items of experimentally contaminated PPE worn by human volunteers.
Conclusions:  BE was effective for recovering infectious viruses from a range of PPE materials.
Significance and Impact of the Study:  PPE plays a crucial role in interrupting transmission of infectious agents from patients to healthcare workers (HCWs). The fate of micro-organisms when PPE is removed and disposed of has important consequences for infection control. Methods described here can be used to conduct rigorous studies of viral survival and transfer on PPE for risk assessments in infection control and HCW protection.     

Effects of chlorophyllin on replication of poliovirus and bovine herpesvirus in vitro

Aims:  Chlorophyllin (CHLN), a synthetic derivative of chlorophyll, was assayed in the replication of poliovirus (PV-1) and bovine herpesvirus (BoHV-1) in HEp-2 cell cultures.
Methods and Results:  Virucidal activity of CHLN was evaluated and the time-of-addition assay was performed as follows: before the infection (−1 and −2 h), at the time of the infection (0 h) and after the infection (1 and 2 h). Plaque reduction assay (PRA) showed that CHLN inhibited BoHV-1 and PV-1 infection and the 50% inhibitory concentrations (IC₅₀) against BoHV-1 and PV-1 infection were 8·6 and 19·8 μg ml⁻¹, respectively. The time-of-addition study demonstrated that the CHLN was effective inhibiting viral replication in 51% and 66·5% for PV-1 and BoHV-1, respectively, at the highest concentration of 20·0 μg ml⁻¹, when added during the infection. The directed effect of CHLN on viral strains demonstrated an inhibition of 62% and 66·4% for PV-1 and BoHV-1, respectively, by PRA.
Conclusions:  These results demonstrated that CHLN could be used as an antiviral suggesting directed activity on virus particles and on virus-receptor sites to BoHV. For poliovirus, CHLN also demonstrated virucide activity, moreover, showed to inhibit early steps of the replication cycle.
Significance and Impact of the Study:  CHLN demonstrated promising selectivity index for both virus strains; therefore, it can be used for the development of an antiviral agent.     

Serovar distribution and antimicrobial susceptibility of swine Salmonella isolates from clinically ill pigs in diagnostic submissions from Indiana in the United States

Aims:  To determine serovar distribution and levels of antimicrobial susceptibility of Salmonella isolated from clinically ill pigs in diagnostic submissions.
Methods and Results:  A total of 197 Salmonella isolates were obtained by the Indiana Animal Disease Diagnostic Laboratory from 2003 to 2005. Minimal inhibitory concentrations (MICs) were determined using the standard microbroth dilution method. The top four serovars identified were Salm. enterica serovar Typhimurium variant Copenhagen, Salm . Derby, Salm . Choleraesuis var. Kunzendorf and Salm . Typhimurium. All isolates were susceptible to the fluoroquinolones tested except that eight isolates were intermediate to difloxacin. The isolates showed a low prevalence of resistance to trimethoprim/sulphadiazine (Sxt), gentamicin (G), ceftiofur (Cf) and cephalothin (Cp) with low MIC₅₀ value of ≤0·5, 0·5, 1 and 4  μ g ml⁻¹, respectively. They showed a high prevalence of resistance to tetracycline (T; 83·8%), and a moderate prevalence to ampicillin (55·8%), spectinomycin (42·6%), ticarcillin (41·6%) and florfenicol (41·1%). There were more isolates of Salm . Typhimurium, including var. Copenhagen and Salm . Agona, that possessed multiple antimicrobial resistance to amoxicillin/clavulanic acid, ampicillin, ceftiofur and cephalothin (AxApCfCp) than the other serovars.
Conclusions:  The swine Salmonella isolates were susceptible to the fluoroquinolones, Sxt, G, Cf and Cp, but resistant to T.
Significance and Impact of the Study:  These findings provided useful information regarding antimicrobial susceptibility and resistance in dealing with clinical salmonellosis in pig herds.     

Isolation of bovine intestinal Lactobacillus plantarum and Pediococcus acidilactici with inhibitory activity against Escherichia coli O157 and F5

Aims:  The growth rate of bovine lactic acid bacteria (LAB) in five different culture conditions, and their inhibitory activity against Escherichia coli O157 and F5 in two assays was assessed to identify LAB for potential prophylactic use in cattle.
Methods and Results:  106 bovine-derived faecal/intestinal LAB were tested in vitro for tolerance to pH 2·0, pH 4·0, 0·15% and 0·3% bile, aerobic incubation, and for inhibitory activity against E. coli O157 ( n  = 3) and F5 ( n  = 1). While no LAB grew at pH 2·0, LAB survivability varied between 35% and 100% on the other tests. Exactly 7·6% (8/106) of LAB supernatants inhibited the growth of E. coli in two assays, whereas 6·6% (7/106) of isolates enhanced the growth of all E. coli strains. Partial 16s rRNA gene sequencing of six best isolates (95th percentile) revealed that five were Lactobacillus plantarum and one Pediococcus acidilactici.
Conclusion:  Lactobacillus plantarum with acid/bile and aerobic resistance and inhibitory activity against E. coli O157 and F5 inhabit the intestinal tract of healthy cattle. Some LAB may enhance E. coli growth.
Significance and Impact of the Study:  Lactobacillus plantarum and P. acidilactici are natural plant micro-organisms and studied silage inoculants. Their identification from gastrointestinal samples of healthy cattle is prophylactically promising.     

A Comparative Investigation of the Bactericidal and Fungicidal Effects of Three Phenolic Disinfectants

Two methods, a capacity use-dilution test and another employing geometrical dilution, are used when comparing the bactericidal and fungicidal effects of a phenolic disinfectant containing 45% (w/w) o -phenylphenol in an aqueous soap solution of linseed oil (soap content 6·5% w/v) with the corresponding effects of the same phenolic compound in an aqueous soya oil soap solution (soap content 3·5% w/v). The soya oil soap did not change the disinfectant capacity on the different test organisms used. For the most resistant strain ( Staphylococcus aureus ) the usedilution concentration was evaluated to be slightly above 1%, i.e. 2%, which is much lower than the recommended use-dilution concentration. However, using the same method and test organisms the capacity use-dilution testing of a third phenolic disinfectant, containing p -chloro- m -cresol and o -benzyl- p -chlorophenol with a total of 9·2 (w/w) phenols in a detergent system, indicated that the recommended use-dilution concentration should be doubled.     

Evaluation of rapid methods for the determination of okadaic acid in mussels

L.CROCI, A.STACCHINI, L.COZZI, G.CICCAGLIONI, F.MAZZEI, F.BOTRÈ AND L.TOTI. 2001 .
Aims: Two different screening methods, a Buffalo Green Monkey cytotoxicity test and a biosensor test, have been considered to replace the official mouse bioassay in monitoring for okadaic acid (OA) levels in mussels.
Methods and Results: Diarrhoetic shellfish poison-contaminated mussels from the Adriatic Sea were assayed in parallel by means of the mouse bioassay and both alternative methods. Both the cytotoxicity test and the biosensor test showed high sensitivity (OA 0·01 mg g^–1 hepatopancreas and 0·002 mg g^–1 hepatopancreas, respectively) and a high correlation with the mouse bioassay ( r =0·932, P  < 0·001 and r =− 0·850, P  < 0·001, respectively).
Conclusions: Both methods are efficacious, quick, inexpensive and provide data on the amount of toxin present in mussels.
Significance and Impact of the Study: Both methods, besides allowing the simultaneous assay of a great number of samples, comply with the ethical need to reduce the use of animals in the laboratory.     

The antibacterial mechanism of carvacrol and thymol against Escherichia coli

Aims:  To investigate the antibacterial mechanism of carvacrol and thymol against Escherichia coli.
Methods and Results:  The time-kill curve results showed that carvacrol and thymol at 200 mg l⁻¹ could inhibit the growth of E. coli . Flow cytometry and fluorescent dyes were used to explore the effect of two components on membrane permeability and membrane potential. In membrane permeability experiment, the mean fluorescence intensity of cells treated with 200 mg l⁻¹ carvacrol or thymol were lower than nonexposed cells. The ratio of red to green fluorescence intensity of DiOC₂(3) reflected the change of membrane potential. Carvacrol and thymol at 200 mg l⁻¹ caused the ratio of red/green decreasing from 0·42 of control to 0·08 and 0·07, respectively.
Conclusions:  Carvacrol and thymol had desired antimicrobial effect on E. coli . The antibacterial effects were attributed to their ability to permeabilize and depolarize the cytoplasmic membrane.
Significance and Impact of the Study:  This study showed the potential use of flow cytometry as a suitable method to investigate the mode of antibacterial action of essential oil components.     

Influence of amino acids, organic solvents and surfactants for phenylalanine ammonia lyase activity in recombinant Escherichia coli

Aim:  To improve phenylalanine ammonia lyase (E.C.4·3·1·5-PAL) activity in recombinant Escherichia coli . Some methods for enrichment of PAL activity in recombinant E. coli JM109 were described. In an effort to create a rich enzyme source these methods would lead to improvements in the production of l -phenylalanine.
Methods and Results:  The possibilities of enriching PAL activity in recombinant E . coli was investigated by using individual and combinations of amino acids, organic solvents and surfactants. PAL activity was induced by adding combination of l -phenylalanine and l -tyrosine, activities as high as 64·3 U g⁻¹of cells were obtained and enzyme activity was enriched by over 3·5-fold in comparison with the control. Permeabilization with cetyl trimethyl ammonium bromide or the acetone significantly enriched cellular PAL activity, which improved over 8·2- and 9·0-fold compared with the control, as high as 148·5 and 164·5 U g⁻¹of cells respectively.
Conclusion:  These efforts may provide some effective methods for enhancing l -phenylalanine ammonia lyase activity.
Significance and Impact of the Study:  These approaches for manipulating recombinant E . coli in an effort to create a rich enzyme source would serve as a biotechnologically important protocol for production of l -phenylalanine.     

Anti-Helicobacter pylori activity of Lactobacillus delbrueckii subsp. bulgaricus strains: preliminary report

Aims:  To evaluate the activities of six Lactobacillus delbrueckii subsp. bulgaricus (LB) strains against 30 Helicobacter pylori strains by agar-well diffusion method.
Methods and Results:  LB cultures [4 × 10⁸–4 × 10⁹ CFU ml⁻¹) either were prepared in milk at their native pH, 3·8–5·0, or were adjusted to pH 6·4–7·7. At low and neutralized pH, LB strains inhibited the growth by 40–86·7% and 16·7–66·7% of H. pylori strains, respectively. LB activity was strain-dependent. At low and neutralized pH, one and five H. pylori strains, respectively, were not inhibited by any LB strain. LB2 and LB3, taken together, were active against most metronidazole and clarithromycin resistant strains.
Conclusions:  All LB strains inhibited a number of H. pylori strains, including also antibiotic resistant strains. LB activity was strain-dependent and better at low pH. At low pH values, the most active LB strains were LB1, LB2 and LB3, inhibiting 86·7% of H. pylori strains, while at neutralized pH values, the most active LB strains were LB2 and LB3, inhibiting 53·3 and 66·7% of H. pylori strains, respectively.
Significance and Impact of the Study:  LB could be utilized in the treatment or prophylaxis of H. pylori infection and warrants clinical investigations.     

Comparison of methods to detect resistance of Penicillium expansum to thiabendazole

Aims:  Because of the lack of a standard method, the aim of this work is to evaluate the suitability of the broth microdilution method CLSI M38-A in determining the resistance level of some Penicillium expansum isolates to thiabendazole (TBZ). The ability of the isolates to produce patulin (PAT) and citrinin (CIT) has been also assessed.
Methods and Results:  Penicillium expansum isolates (128) were assayed (apples, pears, grapes and five reference strains). It was observed that 69·4% of the strains isolated from apples and pears were resistant to TBZ. Sensitive isolates were inhibited at 0·25–0·5 μg ml⁻¹ whilst resistant isolates still grew at 512 μg ml⁻¹. PAT was produced by all P. expansum isolates. CIT was detected in 98·8% of TBZ-resistant isolates and in 89·1% of the TBZ-sensitive isolates.
Conclusions:  The preliminary screening method combined with the adaptation of the method CLSI M38-A, can be a good strategy to be used in assessing the in vitro activity of TBZ against a large number of isolates.
Significance and Impact of the Study:  The proposed methodology can be a contribution to the standardization of susceptibility tests to fungicides against P. expansum.