Transcriptomic and metabolic responses of Staphylococcus aureus in mixed culture with Lactobacillus plantarum, Streptococcus thermophilus and Enterococcus durans in milk

Abstract

Staphylococcus aureus is a major food-borne pathogen due to the production of enterotoxin and is particularly prevalent in contaminated milk and dairy products. The lactic acid bacteria (LAB) are widely used as biocontrol agents in fermented foods which can inhibit pathogenic flora. In our work, we investigated the influence of three strains of LAB (Lactobacillus plantarum, Streptococcus thermophilus and Enterococcus durans) on the relative expression of three enterotoxin genes (sea, sec, sell) and eight virulence and/or regulatory genes (sarA, saeS, codY, srrA, rot, hld/RNAIII, agrA/RNAII, sigB) in two S. aureus strains (MW2 and Sa1612) in TSB and reduced-fat milk (1.5 %) at 30 °C over a 24-h period. The tested LAB and S. aureus strains proved to be mutually non-competitive or only slightly competitive during co-cultivation. In addition, under the above-mentioned conditions, differential gene expression between the S. aureus MW2 and Sa1612 strains was well documented. S. aureus growth was changed in mixed culture with LAB; however, its effect on the repression of sea and sec expression correlated with production of these virulence factors. In comparison, the presence of LAB strains generally inhibited the expression of sec, sell, sarA, seaS, agrA/RNAII and hld/RNAIII genes. The effect of LAB strains presence on the expression of sea, codY, srrA, rot and sigB genes was medium, time, LAB and S. aureus strain specific. SEA and SEC production was significantly reduced in milk compared to TSB in pure culture. After the 24-h cultivation, S. aureus MW2 and Sa1612 SEC production was 187 and 331 times lower in milk compared to TSB, respectively (0.07 and 0.39 ng/mL in milk, versus 13.1 and 129.2 ng/mL in TSB, respectively). At the same time S. aureus MW2 and Sa1612 SEA production was 77 and 68 times lower in milk compared to TSB, respectively (0.99 and 0.17 ng/mL in milk, versus 76.4 and 11.5 ng/mL in TSB, respectively). This study has revealed new insights into the interaction between S. aureus and LAB (L. plantarum, S. thermophilus, E. durans) on the level of the expression and/or production of S. aureus enterotoxins, regulatory and virulence genes in different media, including milk. This study provides data which may improve the quality of food production.

In vitro co-culture of Clostridium scindens with primary human colonic epithelium protects the epithelium against Staphylococcus aureus

“…These results indicate that the production of SE by S. aureus was suppressed when C. scindens was present, but this suppression was not reliant on the creation of secondary bile acids. Similar findings have been observed in co-cultures of S. aureus with other bacterial species in vitro (Zdenkova et al, 2016;Nogueira Viçosa et al, 2019;Rodríguez-Sánchez et al, 2022). However, it is noteworthy that this phenomenon was observed for the first time in S. aureus-C. scindens co-culture in the presence of colonic cells.…”

Lactobacillus plantarum Strains Isolated from Polish Regional Cheeses Exhibit Anti-Staphylococcal Activity and Selected Probiotic Properties

“…The pathogenic effects of S. aureus are connected with enterotoxin production in food matrix. It has been proved that 5 × 10 5 cells of enterotoxin-producing S. aureus strains per ml is a threshold value resulting in the production of enterotoxin [39,40]. Therefore, the key prevention should be to eliminate any factors and conditions that enhance the growth of the pathogen and the production of enterotoxin [41].…”

“…In another study, S. aureus count decreased below the detection limit after 72 h of incubation when milk was inoculated with 3 log CFU/ml of both L. plantarum and S. aureus [42]. It was also shown that presence of S. aureus in co-culture with some L. plantarum strains slows down the pH lowering in the matrix, which could be the reason of overdue the effect of exhibited anti-staphylococcal efficiency [40].…”

Contribution of omics to biopreservation: Toward food microbiome engineering

“…The expression of several enterotoxins and global regulator genes (including agr) was downregulated, while the expression of genes involved in metabolism was upregulated. Finally, the interaction of S. aureus with a mixed culture of Enterococcus durans, E. faecalis and L. lactis in milk confirmed that the production of enterotoxins was reduced in mixed culture and the expression of several genes involved in virulence was inhibited (Zdenkova et al, 2016). All these studies on the interaction of S. aureus with different lactic acid bacteria converge on a very important idea that the mechanism of action of biopreservation can result in the inhibition of virulence by inhibiting the production of enterotoxins through the decreased expression of genes involved in their synthesis.…”