Nisin activity against methicillin-resistant and methicillin-sensitive Staphylococcus aureus and risk of resistance acquisition

The objective of this study was to analyze the antimicrobial effect of nisin against MRSA (Methicillin-Resistant Staphylococcus aureus) and MSSA (Methicillin-Sensitive Staphylococcus aureus), and at the same time examine the possibility of the bacteria to develope nisin resistance. The antimicrobial susceptibility of the strains was tested using the agar diffusion and/or microdilution methods. To select nisin-resistant strains, bacteria were grown consecutively at sublethal concentrations of the bacteriocin. Nisin showed bactericidal activity against most of the tested strains. MRSA required higher doses of bacteriocin compared to MSSA both for inhibition and cell death. However, transfers in the presence of nisin could completely eliminate nisin activity with an increase in minimal inhibitory concentration value of up to 250 times. Nisin-resistance could be maintained in MRSA and MSSA even in the absence of the bacteriocin. Nisin resistance affected antibiotic susceptibility of both MRSA and MSSA to mainly Cefoxitin, Oxacillin, and Erythromycin. These results indicate that nisin-resistance is a complex trait among MSSA and MRSA and must be elucidated before the therapeutic recommendation of nisin to treat infections caused by these bacterial species.

THE EFFECT OF TAPIOCA-BASED EDIBLE COATING ENRICHED WITH NISIN ON QUALITY OF PATIN (PANGASIUS HYPOPHTHALMUS) FILLET DURING COLD STORAGE

The effect of tapioca-based edible coating enriched with nisin in preserving the quality of patin fish fillet during cold stored (410C) for 16 days was evaluated. The examination was conducted including Total Plate Count (TPC), pH, TVB (Total Volatile Base), and TBA (Thiobarbituric Acid) values. The results showed that the tapioca-based edible coating enriched with nisin significantly has affected the TPC, TVB, and TBA values, and insignificantly affected the pH of patin fillets samples. The higher nisin activity on the tapioca-based edible coating solutions, the better effect on maintaining the quality of patin fish fillets. Enrichment of nisin at 2000 IU/ ml on tapioca-based edible coating solution could maintain the patin fish fillets quality during 16th day stored at 410C.

Turbidimetric Assay of Nisin in Tender Coconut Water

Nisin activity in tender coconut water using <em>Lactococcus lactis</em> subspecies <em>cremoris </em>as test microorganism was estimated using turbidimetry by measuring optical density at 600nm after 6 h. of incubation at 37⁰C. The test microorganism was cultivated in nutrient broth with different concentration of nisin along with tender coconut water. A standard curve was drawn between optical density and known concentration of nisin. The nisin concentration of the test samples was measured by curve fitting method using the optical density values. The results thus obtained by this method were reproducible, rapid and more accurate in tender coconut water and hence it may be employed for the determination of nisin activity in tender coconut water on regular basis for quality control purposes.

Activity Retention after Nisin Entrapment in a Polyethylene Oxide Brush Layer

The cationic, amphiphilic peptide nisin is an effective inhibitor of gram-positive bacteria whose mode of action does not encourage pathogenic resistance, and its proper incorporation into food packaging could enhance food stability, safety, and quality in a number of circumstances. Sufficiently small peptides have been shown to integrate into otherwise nonfouling polyethylene oxide (PEO) brush layers in accordance with their amphiphilicity and ordered structure, including nisin, and we have recently shown that nisin entrapment within a PEO layer does not compromise the nonfouling character of that layer. In this work we test the hypothesis that surface-bound, pendant PEO chains will inhibit displacement of entrapped nisin by competing proteins and, in this way, prolong retention of nisin activity at the interface. For this purpose, the antimicrobial activity of nisin-loaded, PEO-coated surfaces was evaluated against the gram-positive indicator strain, Pediococcus pentosaceous. The retained antimicrobial activity of nisin layers was evaluated on uncoated and PEO-coated surfaces after incubation in the presence of bovine serum albumin for contact periods up to 1 week. Nisin-loaded, uncoated and PEO-coated samples were withdrawn at selected times and were incubated on plates inoculated with P. pentosaceous to quantify nisin activity by determination of kill zone radii. Our results indicate that nisin activity is retained at a higher level for a longer period of time after entrapment within PEO than after direct adsorption in the absence of PEO, owing to inhibition of nisin exchange with dissolved protein afforded by the pendant PEO chains.

Mechanism of Synergistic Inhibition of Listeria monocytogenes Growth by Lactic Acid, Monolaurin, and Nisin

ABSTRACT The combined lactic acid, monolaurin, and nisin effects on time-to-detection (optical density at 600 nm) extension were greater (P < 0.05) than any single or paired combination effect, which demonstrates a synergistic interaction among the antimicrobials. Monolaurin exposure caused C12:0 cell membrane incorporation. Lactic acid caused increased monolaurin C12:0 membrane incorporation, while nisin had no influence. We postulate that lactic acid-enhanced monolaurin C12:0 incorporation into the cell membrane increased membrane fluidity resulting in increased nisin activity.