Improved agar diffusion assay for nisin quantification

Rogers, Ann M.; Montville, Thomas J.

doi:10.1080/08905439109549799

Cited by 75 publications

(40 citation statements)

References 12 publications

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“…Serial twofold dilutions of L. plantarum 35d and E. casseliflavus IM 416K1 cell free supernatant fluid (CFSF) were assayed by the agar well diffusion method (Rogers & Montville, 1991) to evaluate the antibacterial activity titration of the crude bacteriocin preparation against L. monocytogenes NCTC 10888. The antimicrobial titre was defined as the reciprocal of the highest dilution showing a distinct inhibition of the indicator growth and expressed in terms of arbitrary units per millilitre (AU ml À1 ) (Mayr-Harting, Hedges, & Berkeley, 1972).…”

Section: Antibacterial Activity Titrationmentioning

confidence: 99%

Use of lactic acid bacteria (LAB) biofilms for the control of Listeria monocytogenes in a small-scale model

et al. 2009

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Section: Antibacterial Activity Titrationmentioning

confidence: 99%

Use of lactic acid bacteria (LAB) biofilms for the control of Listeria monocytogenes in a small-scale model

et al. 2009

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“…In contrast, little is known about how Tween 20, a surfactant and medium supplement widely used in laboratory studies of bacteriocins, influences homeoviscous adaptation. Tween 20 improves the well diffusion method for nisin quantification (28,44). It also synergistically improves the antimicrobial effects of nisin and other bacteriocins (2,44).…”

mentioning

confidence: 99%

Temperature- and Surfactant-Induced Membrane Modifications That Alter Listeria monocytogenes Nisin Sensitivity by Different Mechanisms

Chikindas

Ludescher

et al. 2002

Appl Environ Microbiol

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Nisin interacts with target membranes in four sequential steps: binding, insertion, aggregation, and pore formation. Alterations in membrane composition might influence any of these steps. We hypothesized that cold temperatures (10°C) and surfactant (0.1% Tween 20) in the growth medium would influence Listeria monocytogenes membrane lipid composition, membrane fluidity, and, as a result, sensitivity to nisin. Compared to the membranes of cells grown at 30°C, those of L. monocytogenes grown at 10°C had increased amounts of shorter, branched-chain fatty acids, increased fluidity (as measured by fluorescence anisotropy), and increased nisin sensitivity. When 0.1% Tween 20 was included in the medium and the cells were cultured at 30°C, there were complex changes in lipid composition. They did not influence membrane fluidity but nonetheless increased nisin sensitivity. Further investigation found that these cells had an increased ability to bind radioactively labeled nisin. This suggests that the modification of the surfactant-adapted cell membrane increased nisin sensitivity at the binding step and demonstrates that each of the four steps can contribute to nisin sensitivity.Listeria monocytogenes is a gram-positive, non-spore-forming food-borne pathogen that can grow at refrigeration temperatures (31, 41). L. monocytogenes has a sophisticated strategy to overcome environmental stresses, such as cold (23, 38), heat (35), an acidic environment (27), and osmotic shock (4). L. monocytogenes is of particular interest with respect to food safety due to its psychrotrophic nature (41), which may result in the enrichment of L. monocytogenes in foods at refrigeration temperature (15). This organism can pose a serious health threat to high-risk populations, such as immunocompromised individuals, newborns, and pregnant women. (42).Nisin is used as an antimicrobial agent against L. monocytogenes. The bactericidal activity of nisin is due to pore formation in the bacterial membrane (12), which occurs through a four-step process of binding, insertion, aggregation, and pore formation. The cell's sensitivity to nisin is influenced by the membrane's lipid composition (24), which might act on any of the four steps. Nisin-resistant L. monocytogenes has a lowered cellular phospholipid content and an altered membrane fatty acid composition. (11,24,25).The cytoplasmic membrane is the primary barrier between the cell and its environment. Environmental factors, especially temperature, influence membrane fluidity by modifying the membrane's lipid composition (19,23). The process of maintaining fluidity, called homeoviscous adaptation (34,29,45), is critical for cell growth at nonoptimal temperatures (5, 20). The concept of membrane fluidity covers the thermal mobility of membrane proteins as well as the microviscosity of the membrane lipid bilayer (33). However, the primary way that bacteria maintain constant membrane fluidity at different growth temperatures is by adjusting their fatty acid compositions (1,5,29). For instance, there are hig...

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“…= 600 nm. The second sample was centrifuged and the pH of the supernatant was adjusted to 6.8 with 5 N NaOH, filtered through a 0.20-mm filter and the antibacterial activity was evaluated using the well-diffusion method [12,16]. Twenty-five millilitre of TSB with soft agar 0.7 % (w/v) was mixed with 50 lL (1 9 10 9 cells/mL) of the indicator bacteria and plated.…”

Section: Bacteriocins Productionmentioning

confidence: 99%

Bacteriocinogenic Bacteria Isolated from Raw Goat Milk and Goat Cheese Produced in the Center of México

et al. 2016

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Currently, there are few reports on the isolation of microorganisms from goat milk and goat cheese that have antibacterial activity. In particular, there are no reports on the isolation of microorganisms with antibacterial activity from these products in central Mexico. Our objective was to isolate bacteria, from goat products, that synthesized antimicrobial peptides with activity against a variety of clinically significant bacteria. We isolated and identified Lactobacillus rhamnosus, L. plantarum, L. pentosus, L. helveticus and Enterococcus faecium from goat cheese, and Aquabacterium fontiphilum, Methylibium petroleiphilum, Piscinobacter aquaticus and Staphylococcus xylosus from goat milk. These bacteria isolated from goat cheese were able to inhibit Staphylococcus aureus, Bacillus cereus, Escherichia coli, Listeria monocytogenes, L. inoccua, Pseudomona aeruginosa, Shigella flexneri, Serratia marcescens, Enterobacter cloacae and Klebsiella pneumoniae. In addition, bacteria from goat milk showed inhibitory activity against B. cereus, L. lactis, E. coli, S. flexneri, E. cloacae and K. pneumonia; S. aureus, L. innocua, S. agalactiae and S. marcescens. The bacteriocins produced by these isolates were shown to be acid stable (pH 2-6) and thermotolerant (up to 100 °C), but were susceptible to proteinases. When screened by PCR for the presence of nisin, pediocin and enterocin A genes, none was found in isolates recovered from goat milk, and only the enterocin A gene was found in isolates from goat cheese.

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Improved agar diffusion assay for nisin quantification

Cited by 75 publications

References 12 publications

Use of lactic acid bacteria (LAB) biofilms for the control of Listeria monocytogenes in a small-scale model

Use of lactic acid bacteria (LAB) biofilms for the control of Listeria monocytogenes in a small-scale model

Temperature- and Surfactant-Induced Membrane Modifications That Alter Listeria monocytogenes Nisin Sensitivity by Different Mechanisms

Bacteriocinogenic Bacteria Isolated from Raw Goat Milk and Goat Cheese Produced in the Center of México

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