Cell-free supernatants produced by lactic acid bacteria reduce Salmonella population in vitro

Abstract

The genus Salmonella is closely associated with foodborne outbreaks and animal diseases, and reports of antimicrobial resistance in Salmonella species are frequent. Several alternatives have been developed to control this pathogen, such as cell-free supernatants (CFS). Our objective here was to evaluate the use of lactic acid bacteria (LAB) CFS against Salmonella in vitro. Seventeen strains of LAB were used to produce CFS, and their antimicrobial activity was screened towards six strains of Salmonella . In addition, CFS were also pH-neutralized and/or boiled. Those with the best results were lyophilized. MICs of lyophilized CFS were 11.25–22.5 g l–1. Freeze-dried CFS were also used to supplement swine and poultry feed (11.25 g kg–1) and in vitro simulated digestion of both species was performed, with Salmonella contamination of 5×106 and 2×105 c.f.u. g−1 of swine and poultry feed, respectively. In the antimicrobial screening, all acidic CFS were able to inhibit the growth of Salmonella . After pH neutralization, Lactobacillus acidophilus Llorente, Limosilactobacillus fermentum CCT 1629, Lactiplantibacillus plantarum PUCPR44, Limosilactobacillus reuteri BioGaia, Lacticaseibacillus rhamnosus ATCC 7469 and Pediococcus pentosaceus UM116 CFS were the only strains that partially maintained their antimicrobial activity and, therefore, were chosen for lyophilization. In the simulated swine digestion, Salmonella counts were reduced ≥1.78 log c.f.u. g–1 in the digesta containing either of the CFS. In the chicken simulation, a significant reduction was obtained with all CFS used (average reduction of 0.59±0.01 log c.f.u. ml–1). In general, the lyophilized CFS of L. fermentum CCT 1629, L. rhamnosus ATCC 7469 and L. acidophilus Llorente presented better antimicrobial activity. In conclusion, CFS show potential as feed additives to control Salmonella in animal production and may be an alternative to the use of antibiotics, minimizing problems related to antimicrobial resistance.

Probiotic Lactobacilli Do Not Protect Chickens against Salmonella Enteritidis Infection by Competitive Exclusion in the Intestinal Tract but in Feed, Outside the Chicken Host

“…It has been repeatedly confirmed that lactobacilli produce metabolites that suppress the growth of Salmonella [28][29][30]. Lactobacilli also produce metabolites affecting host gene expression [31,32].…”

Bioprotective potential of lactic acid bacteria and their metabolites against enterotoxigenic Escherichia coli

“…plantarum 7.1 – nomenclature updated according to Zheng et al . [16] –, due to the bioprotective potential pointed out in several studies addressing the species [8, 17, 18]. The strains were stored in de Man, Rogosa, and Sharpe broth (MRS; HiMedia Laboratories, Mumbai, India) +20 % glycerol, in an ultrafreezer at −80 °C, and reactivated in 7 ml of MRS broth, incubated for 18 h at 37 °C.…”

“…LAB were previously isolated from cocoa fermentation [15], with the selection of strains Limosilactobacillus (Lactobacillus) fermentum 5.2, Lactiplantibacillus (Lactobacillus) plantarum 6.2, and L. plantarum 7.1 -nomenclature updated according to Zheng et al [16] -, due to the bioprotective potential pointed out in several studies addressing the species [8,17,18]. The strains were stored in de Man, Rogosa, and Sharpe broth (MRS; HiMedia Laboratories, Mumbai, India) +20 % glycerol, in an ultrafreezer at −80 °C, and reactivated in 7 ml of MRS broth, incubated for 18 h at 37 °C.…”

“…Several strategies are used to prevent neonatal diarrhoea, such as the vaccination of pregnant females for transfer of passive immunity via breastfeeding, or even the vaccination of the piglets themselves [6]. The use of antibiotics is also a common and widely used practice, even if their use is highly debated due to antimicrobial resistance issues and public health concerns [7,8].…”

Microbial Musings – November 2021

“…We start this month with two papers from the Antimicrobials and AMR section of the journal. The first is from the group of Fernando Luciano at the Pontificia Universidade Catolica do Parana, Brazil [ 2 ]. This is an interesting paper that tests a potentially cheap approach to treat animal feed to reduce carriage of Salmonella in livestock.…”