LAB Bacteriocins Controlling the Food Isolated (Drug-Resistant) Staphylococci

Abstract

Staphylococci are a group of microorganisms that can be often found in processed food and they might pose a risk for human health. In this study we have determined the content of staphylococci in 7 different fresh goat-milk cheeses. These bacteria were present in all of them, ranging from 103 to 106 CFU/g based on growth on selective media. Thus, a set of 97 colonies was randomly picked for phenotypic and genotypic identification. They could be clustered by RAPD-PCR in 10 genotypes, which were assigned by 16S rDNA sequencing to four Staphylococcus species: Staphylococcus aureus, Staphylococcus chromogenes, S. simulans, and S. xylosus. Representative strains of these species (n = 25) were tested for antibiotic sensitivity, and 11 of them were resistant to at least one of the antibiotics tested, including erythromycin, amoxicillin-clavulanic acid and oxacillin. We also tested two bacteriocins produced by lactic acid bacteria (LAB), namely the circular bacteriocin AS-48 and the lantibiotic nisin. These peptides have different mechanism of action at the membrane level. Nevertheless, both were able to inhibit staphylococci growth at low concentrations ranging between 0.16–0.73 μM for AS-48 and 0.02–0.23 μM for nisin, including the strains that displayed antibiotic resistance. The combined effect of these bacteriocins were tested and the fractional inhibitory concentration index (FICI) was calculated. Remarkably, upon combination, they were active at the low micromolar range with a significant reduction of the minimal inhibitory concentration. Our data confirms synergistic effect, either total or partial, between AS-48 and nisin for the control of staphylococci and including antibiotic resistant strains. Collectively, these results indicate that the combined use of AS-48 and nisin could help controlling (pathogenic) staphylococci in food processing and preventing antibiotic-resistant strains reaching the consumer in the final products.

Insights into Chagas treatment based on the potential of bacteriocin AS-48

“…One of the most exciting and well-known bacteriocin is the circular enterocin AS-48. It is a 70-residue, head-to-tail joined, amphipathic and cationic bacteriocin produced by different Enterococcus species (Maqueda et al, 2004) with a broad bactericidal activity against both Gram-positive and Gram-negative disease-associated pathogens (Gálvez et al, 1989; Aguilar-Pérez et al, 2018; Cebrián et al, 2018; Perales-Adán et al, 2018). The most distinctive structural feature of AS-48 is its circular structure and its amphipathicity, which contributes to a remarkable stability in a broad range of temperature and pH (Maqueda et al, 2004; Montalbán-López et al, 2011; Sánchez-Hidalgo et al, 2011).…”

Synergy of the Bacteriocin AS-48 and Antibiotics against Uropathogenic Enterococci

“…AS-48 is a circular, well-characterized [ 15 , 35 ] and safe [ 24 ] bacteriocin with a proven, broad potential in the food industry and potential health applications. This cationic and amphipathic peptide has a bactericidal effect inhibiting the growth of several pathogenic Gram-positive bacteria, such as Staphylococcus aureus [ 23 ], Cutibacterium acnes (causing cell death and impaired biofilm formation) [ 19 ], or even Mycobacterium tuberculosis [ 36 ], among others. In this work, the AS-48 MIC values for the uropathogenic enterococcal isolates (average 3.1 ± 1 mg/L) were similar to those required to inhibit other Gram-positive bacteria regardless of the genotypic or phenotypic characteristic of the clinical strains.…”

“…Cross-resistance antibiotics-bacteriocins are a broadly analyzed phenomenon, which to date seems to be ruled out due to chemical structure and the different targets (usually the lipid bilayer for many bacteriocins). Similarly to other bacteriocins [ 37 , 38 , 39 ], available data evidence the synergy of AS-48 when it was combined with other antimicrobial compounds (e.g., ethambutol, nisin, or lysozyme), leading to reductions in the MIC of both compounds [ 19 , 23 , 36 ].…”

“…AS-48 inserts into the membrane of sensitive bacteria, creating pores in a mechanism that is independent of any receptor [ 17 ], thereby reducing the development of stable and transmissible resistance. AS-48 has been well characterized for its activity against food spoilage and pathogenic bacteria and also against diverse human pathogens with a low minimal inhibitory concentration (MIC) in the nano- to micromolar range [ 18 , 19 , 20 , 21 , 22 , 23 ]. In addition, a potent trypanocidal activity has been recently described [ 18 , 20 , 21 ].…”

Antilisterial Activity of Bacteriocins Produced by Lactic Bacteria Isolated from Dairy Products

“…This natural mechanism of recombination can also be employed to create a multi-bacteriocinogenic strain with levels of production higher than those of the native sources [40] or to obtain a strain endowed with an amplified activity spectrum against both food-borne pathogens and spoilage bacteria [41]. A possible hurdle associated with the use of bacteriocins against these microorganisms is the development of resistant bacteria populations and this could be overcome by generating multiple bacteriocin producers [42], for example through heterologous co-production.…”