Higher Antilisterial Activity Research Articles

Antimicrobial activity of enterocins against Listeria sp. and other food spoilage bacteria.

To determine bacteriocin producers and the prevalence of structural enterocin genes and to detect the spectrum of activity against foodborne pathogens, from isolates of Enterococcus faecium and Enterococcus faecalis that were isolated from food and the environment. The entA, entB, entP, ent1071 and entX genes, which encode enterocins were the most frequently observed. Enterocins were thermostable, proteinaceous, and resistant to catalase. None of the isolates produced hemolysin, and inhibition resulting from bacteriophage lysis was excluded. The bactericidal effect of enterocins against L. innocua 12612 was determined by optical density and colony forming units. For the activity spectrum, elimination of mainly Listeria strains, Bacillus sp. and clinical enterococci, was observed. Imaging with scanning electron microscopy after treatment with enterocin Efm22 showed irregular rod-shaped cells and loss of cellular integrity. The isolates evaluated in this study are candidates for the production of enterocins that will be used as food biopreservatives, because they have high anti-listerial activity even after 24h of experimentation, and used in the pharmaceutical area because they inhibit clinical microorganisms.

Preparation of phosphatidylcholine nanovesicles containing bacteriocin CAMT2 and their anti-listerial activity

A novel bacteriocin CAMT2, produced by Bacillus amyloliquefaciens ZJHD3-06, has potential as a natural biopreservative for the control of food-borne spoilage and pathogenic bacteria. To avoid interaction of CAMT2 with components of food that may adversely impact its antibacterial activity, CAMT2 was encapsulated into nanovesicles prepared from soybean phosphatidylcholine. The encapsulation of CAMT2 exhibited a limited impact on functional structure and crystallinity of bacteriocin CAMT2, but a high anti-listerial activity in agar, and increase its stability in food at refrigeration temperature (4 °C). The results also showed that both encapsulated and free CAMT2 had good anti-listerial effect in skim milk at refrigeration temperature. However, encapsulated CAMT2 performed better than free CAMT2 against Listeria in whole milk. These results showed that nano-encapsulation is an effective method of protecting bacteriocin from fat in milk and retaining its antimicrobial efficacy.

Assessment of virulence factors, antibiotic resistance and amino-decarboxylase activity in Enterococcus faecium MXVK29 isolated from Mexican chorizo.

The use of molecular techniques has allowed, in recent years, to detect pathogenicity genes present in the genome of starter cultures used in food processing and preservation. The presence of these genes is undesirable, because horizontal transfer may occur with the natural biota of consumers. For this reason, it is important to analyse the presence of pathogenicity genes in such cultures. In this work, virulence factors and antibiotic resistance of Enterococcus faecium strain MXVK29, producing an antimicrobial compound with high antilisterial activity, were analysed. The results indicate that the strain is safe to be used in food processing as starter culture.

Characterization of bacteriocin produced by Enterococcus faecium CN-25 isolated from traditionally Thai fermented fish roe

Enterococcus faecium CN-25 was isolated from a traditionally Thai fermented fish roe, som-kai-pla, and was found to possess enterocin A and B genes. Among the 30 microorganisms tested, the produced bacteriocin exhibited antagonistic activity against Listeria monocytogenes TISTR 1327. The bacterium maximally produced bacteriocin at a concentration of 1828 AU/ml at the beginning of the stationary phase (at 18 h) in the inexpensive rice bran medium. The antilisterial activity of the compound was not affected by heating at 60–100 °C for up to 30 min. High antilisterial activity remained at pH 2. Partially purified CN-25 bacteriocin derived from E. faecium CN-25 completely inhibited the growth of L. monocytogenes at the minimum concentration of 2.38 μg/ml. The compound had no effect on the efflux of ATP from L. monocytogenes but triggered the intracellular hydrolysis of ATP, as evidenced by a decrease in the luminescence of total ATP. The bacteriocin also depleted the transmembrane electrical potential (ΔΨ) but had no effect on the transmembrane pH gradient (ΔpH). Therefore, the partially purified CN-25 peptide may be useful for improving the product safety of fermented fish products.

Occurrence of antilisterial structural bacteriocins genes in meat borne lactic acid bacteria

Abstract The ability to inhibit the growth of Listeria cells and the presence of bacteriocin encoding genes was examined in 115 LAB strains isolated from Argentinean vacuum-packaged beef and different traditional fermented sausages. Lactobacillus (L) sakei, Lactobacillus (L) curvatus and Enterococcus (E) faecium showed a great inhibition of all Listeria strains evaluated while Pediococcus (P) acidilactici and Lactobacillus (L) plantarum demonstrated a limited or absent antilisterial activity. Both L. curvatus and L. sakei carried the sppA, sppQ and sapA structural genes, encoding for sakacin P, sakacin Q and curvacin A bacteriocins, respectively. Whilst L. curvatus exhibited a higher occurrence of these genes, L. sakei strains were more effective at inhibiting Listeria (L) strains, Listeria monocytogenes UC8159 and Listeria innocua 7 being the most sensitive to these bacteriocins. Among analyzed E. faecium strains, the wide distribution of entA, entB and entP genes accounted for the high antilisterial activity particularly observed against L. monocytogenes FBUNT. The structural gene plantEF was mostly present in Lactobacillus plantarum strains and no pedA gene was found in P. acidilactici evaluated strains. The antilisterial potential of L. sakei and E. faecium offers great possibilities for the meat industry as biopreservative cultures, although more studies are needed in order to conclude about this issue.

Functional Properties of Pediococcus Species Isolated from Traditional Fermented Cereal Gruel and Milk in Nigeria

Pediococcus species were isolated from ogi, fermented cow and sheep milk. Functional properties such as hydrogen peroxide production, tolerance to simulated gastric transit with pepsin and bile salts, bile salt hydrolytic (BSH) activity, in vitro adherence assay and antimicrobial characteristics were carried out. The strains tolerated bile salts and BSH activity was positive. Pediococcus acidilactici OB4 survived gastric transit after 180min comparable to a probiotic strain, L. acidophilus CNRZ1923. The strains exhibited good adhesion to the three extracellular matrices. Two isolates (P. acidilactici OB4 and P. pentosaceus SM3) produced bacteriocin. Bacteriocins were stable at pH 4-9 and on treatment with lipase, catalase, α-amylase and lysozyme, while their activity was lost on treatment with proteinase K, pronase E, pepsin and trypsin. The bacteriocins produced by P. pentosaceus SM3 was heat stable at 100°C for 10 min while P. acidilactici OB4 was stable at 100°C for 30 min. The bacteriocin produced by P. acidilactici OB4 was identified as PedA while P. pentosaceus SM3 was PedB. The bacteriocins had relative heat stability, high anti-listerial activity and a good spectrum of activity against some pathogenic microorganisms. The results demonstrated possible inclusion in a starter culture fermentation process of food and dairy products and safety characteristics.

Inhibition ofListeria monocytogenesby a combination of chitosan and divergicin M35

The antimicrobial activities of the class IIa bacteriocin divergicin M35 and several types of chitosan against Listeria monocytogenes were quantified by agar diffusion, critical micro-dilution, and viable count and observed by electron microscopy. Antimicrobial activity of chitosan depended on its molecular mass (MM) and the pH. Three chitosans with MM values of 2, 20, and 100 kDa and 87.4% degree of deacetylation (DDA) were chosen for further study, based on high anti-listerial activity at pH 4.5. Electron microscopy suggested that the mechanism of anti-listerial activity also varied with the MM. Low-MM chitosan appeared to inhibit L. monocytogenes by affecting cell permeability and growth, whereas medium- and high-MM chitosan may form a barrier on the cell surface that prevents entry of nutrients. The minimum inhibitory concentrations (MICs) of 2, 20, and 100 kDa chitosan and divergicin M35 against a divergicin-resistant strain of L. monocytogenes (LSD 535) were 2.5, 2.5, 0.625, and 0.25 mg/mL, respectively. The combination of any of these 3 chitosans and divergicin M35 appeared to have an additive effect against L. monocytogenes, as determined by fractional inhibitory concentration (FIC) index. This study provides useful data for the development of chitosan films incorporating divergicin M35 for inhibiting L. monocytogenes in foods.

Partial Characterization of Nine Bacteriocins Produced by Lactic Acid Bacteria Isolated from Cold-Smoked Salmon with Activity against Listeria monocytogenes

Nine LAB bacteriocin-producers, isolated from vacuum-packaged cold-smoked salmon (CSS), were phenotypically and genotypically identified as Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillus fermentum, Enterococcus faecium, and Pediococcus acidilactici. Their bacteriocins were partially characterized. The antimicrobial spectrum was determined against Listeria monocytogenes, E. faecalis, E. faecium, and Staphylococcus aureus. The molecular size of bacteriocins ranged from 2.8 to 4.5 kDa. They were inactivated by treatment with proteolytic enzymes but not by lipolytic or glycolytic enzymes. Maximal activity against L. monocytogenes ranged between 800 and 10000 AU/mL at pH 6.5. Most of the bacteriocins maintained full activity in a pH range of 2.0 to 8.0 but were partially or completely inactivated at pH 10.0. After heating at 60°C and 100°C, only two bacteriocins from Lb. curvatus strains partially lost activity. All bacteriocins showed a narrow spectrum of activity and a high anti-listerial activity, which is characteristic of the class IIa bacteriocins. Isolated bacteriocin-producing LAB could be used successfully in the bio-preservation of CSS and development of new potential bio-preservatives for CSS active against L. monocytogenes.

Antilisterial Activity of Plantaricin UG1 during Manufacture of Zabady and Kareesh Cheese: Two Arabian Dairy Products

Here, plantaricin UG1 was shown to inhibit Listeria monocytogenes LMG10470 (L. monocytogenes) cells. The inhibition was not caused by lactic acid produced by the bacteriocin producing strain Lactobacillus plantarum UG1 (Lact. plantarum). Partially purified plantaricin UG1 had a higher antilisterial activity than Lact. plantarum cells in both Zabady and Kareesh cheese samples during their maturation. Compared to the antilisterial activity in Kareesh cheese, plantaricin UG1 showed a faster effect during Zabady manufacture.

Partial characterization of a class IIa pediocin produced by Pediococcus parvulus 133 strain isolated from meat (Mexican “chorizo”)

Pediocin-like bacteriocins are antimicrobial substances produced by some bacteria with high antilisterial activity. Several isolates of Pediococcus acidilactici and two Pediococcus parvulus strains of vegetable origin have been reported to produce this kind of peptide. This work presents the partial characterization of the bacteriocin produced by P. parvulus 133 found in meat and confirms its identity as a heat resistant, antilisterial bacteriocin. This peptide has a relatively narrow inhibitory spectrum but a high antilisterial activity. Pediocin remained active after heating to 121 °C, but its thermoresistance varied with pH. The pH selective adsorption method resulted in a 150-fold concentration of antimicrobial activity. The final extract was obtained by ultrafiltration and resulted in an additional 10-fold concentration of activity. Molecular weight was estimated as 5 kDa and isoelectric point was 8.65. The sequence of the first 17 aminoacids at the N-terminal end of the bacteriocin showed complete coincidence with that previously reported for pediocin A1 (AcH) and with an antilisterial peptide produced by Bacillus coagulans. High sequence similarity was also found with two other antilisterial bacteriocins.

Inhibition of Listeria monocytogenes LMG10470 by plantaricin UG1 in vitro and in beef meat.

The inhibition of Listeria monocytogenes LMG 10470 occurred due to plantaricin UG1, but not to lactic acid produced by Lactobacillus plantarum UG1 or its negatie variant (BAC). Partially purified plantaricin UG1 had a higher antilisterial activity in vitro and in meat than Lactobacillus plantarum UG1 culture. Plantaricin UG1 activity was higher in brain heart infusion (BHI) broth than in minced meat. The inhibitory effect of plantaricin UG1 against L. monocytogenes LMG10470 was dependent on its concentration. The 22,880 AU/mL appeared to be an ideal meat preservative in this experiment.

Megaplasmid encoding novel sugar utilizing phenotypes, pediocin production and immunity in Pediococcus acidilactici C20

A bacteriocinogenic strain of Pediococcus acidilactici C20 isolated from fowl intestine was found to bear a single megaplasmid. Strain C20 exhibited an ability to ferment a wide range of sugars including lactose, maltose and melibiose. Curing experiments employing novobiocin and high temperature indicated that the genetic determinants for pediocin production, immunity function and utilization of several sugars resided on the megaplasmid. Pediocin production with different sugars was tested and culture filtrate activity varied from 2500 AU ml−1to 3500 AU ml−1at 1% of carbon source. Molecular and biochemical techniques were used to characterize the bacteriocin produced by strain C20. It was found to be a pediocin AcH/PA-1 like bacteriocin with high antilisterial activity.

Comparative Salmonella Spp. and Listeria monocytogenes Inactivation Rates in Four Commercial Mayonnaise Products

Salmonella spp. and Listeria monocytogenes strains were inoculated into four commercial mayonnaise products: sandwich spread, real mayonnaise, reduced calorie mayonnaise dressing, and cholesterol-free reduced calorie mayonnaise dressing. Products represented a broad cross-section of aqueous phase acetic acid, salt, sucrose, and other compositional factors. Results showed that Salmonella spp. inactivation rates were unaffected by formula composition. The organism was rapidly inactivated, decreasing ≥8 log10 CFU/g in ≤72 h, in each of the four products. L. monocytogenes inactivation rates were directly correlated with aqueous phase acetic acid concentrations as follows: sandwich spread ≥ real mayonnaise > cholesterol-free reduced calorie mayonnaise dressing > reduced calorie mayonnaise dressing. L. monocytogenes inactivation rate in sandwich spread and real mayonnaise was similar to Salmonella spp. The reduced calorie mayonnaise dressings showed gradual, incremental population declines. L. monocytogenes decreased 3 and 5 log10 CFU/g in 72 h in reduced calorie and cholesterol-free reduced calorie mayonnaise dressings, respectively. The higher anti-listerial activity in the cholesterol free formulation was attributed to egg white lysozyme. This study documented that commercial mayonnaise, including reduced calorie mayonnaise dressing varieties, represent negligible consumer safety risks.