Correction: Thermal stability and structural changes in bacterial toxins responsible for food poisoning

Antibacterial Effects of Synthetic Plantaricins Against Staphylococcus aureus

Background/Objectives: Plantaricins without a signal sequence were synthesized based on bacteriocins, plantaricins A, E, F, J, and K, of Lactiplantibacillus plantarum KM2. The antibacterial activities of four combinations of synthetic plantaricins-spPlnA, E&F, E&J, and J&K-were identified against Staphylococcus aureus ATCC 12692. And in this experiment, we aimed to identify the antimicrobial mechanism of the synthesized plantaricin sample against S. aureus. Methods/Results: The minimal inhibitory concentrations for each combination were 1.4 μg/mL, 1.8 μg/mL, 1.6 μg/mL, and 1.6 μg/mL, respectively. Raman spectra changed after treating S. aureus ATCC 12692 with synthetic plantaricins. Furthermore, transmission electron microscopy results revealed that the four synthetic plantaricin combinations could induce the cell lysis of S. aureus ATCC 12692. Finally, the four synthetic plantaricin combinations maintained their antibacterial effect at temperatures below 40 °C, and at pH levels of pH = (4-7). Except for spPlnJ&K, they are stable against the action of α-amylase and lysozyme. Overall, these results indicate that, excepting spPlnJ&K, the three synthetic plantaricin combinations exhibit similar antibacterial activity. Conclusions: Through this study, we confirmed that synthetic plantaricin exhibited antimicrobial activity against S. aureus, demonstrating its potential as a direct antimicrobial agent. However, since the antimicrobial activity decreased due to protease, it was confirmed that its use is limited in environments where protease is present.

Enterotoxigenic Staphylococcus aureus in Brazilian artisanal cheeses: Occurrence, counts, phenotypic and genotypic profiles

The present study aimed to assess the occurrence and counts of Staphylococcus aureus in Brazilian artisanal cheeses (BAC) produced in five regions of Brazil: Coalho and Manteiga (Northeast region); Colonial and Serrano (South); Caipira (Central-West); Marajó (North); and Minas Artisanal cheeses, from Araxá, Campos das Vertentes, Cerrado, Serro and Canastra microregions (Southeast). The resistance to chlorine-based sanitizers, ability to attach to stainless steel surfaces, and antibiogram profile of a large set of S. aureus strains (n = 585) were assessed. Further, a total of 42 isolates were evaluated for the presence of enterotoxigenic genes (sea, seb, sec, sed, see, seg, sei, sej, and ser) and submitted to typing using pulsed-field gel electrophoresis (PFGE). BAC presented high counts of S. aureus (3.4-6.4 log CFU/g), varying from 25 to 62.5%. From the S. aureus strains (n = 585) assessed, 16% could resist 200 ppm of sodium hypochlorite, whereas 87.6% produced strong ability to attach to stainless steel surfaces, corroborating with S. aureus ability to persist and spread in the environment. Furthermore, the relatively high frequency (80.5%) of multidrug-resistant S. aureus and the presence of enterotoxin genes in 92.6% of the strains is of utmost attention. It reveals the lurking threat of SFP that can survive when conditions are favorable. The presence of enterotoxigenic and antimicrobial-resistant strains of S. aureus in cheese constitutes a potential risk to public health. This result calls for better control of cheese contamination sources, and taking hygienic measures is necessary for food safety. More attention should be paid to animal welfare and hygiene practices in some dairy farms during manufacturing to enhance the microbiological quality of traditional cheese products.

Development of antibodies against recombinant staphylococcal enterotoxin B from food poisoning cases

Background and Aim

Staphylococcal enterotoxin B (SEB) is the most common serotype involved in food poisoning. The aim of this study was to develop immunoassay detection methods using a recombinant enterotoxin B antigen protein to produce recombinant polyclonal antibodies in vivo.

Materials and Methods

Staphylococcus aureus isolated from a food poisoning case (strain JH5800) was analyzed by polymerase chain reaction (PCR) and confirmed to contain a seb gene of 477 bp. A SEB segment was amplified, cloned, sequenced, and aligned. The PCR product corresponding to the predicted mature SEB peptide was inserted into Escherichia coli BL21 (DE-3) expression vector and expressed as a hexahistidine-SEB fusion protein. Antiserum against recombinant SEB protein was produced by immunization of Balb/c mice.

Results

In the indirect enzyme-linked immunosorbent assay (ELISA), the polyclonal antibodies produced had a titer of 1:3200. The seb gene of Staphylococcus aureus isolated from a poisoning case (JH5800) had a molecular size of about 477 bp and a band of recombinant SEB toxin was observed at approximately 30 kDa on SDS-PAGE gel. The polyclonal anti-SEB antibody titer, as revealed by indirect ELISA, was 1:3200 at 59 days.

Conclusion

SEB recombinant protein could be used to produce polyclonal antibodies. ELISA and Western blotting were used to analyze the specificity and sensitivity of the recombinant polyclonal antibodies. Polyclonal antibodies produced could be used to detect SEB on a large-scale.