Inhibitory activity of natural antimicrobial compounds against histamine-forming bacterial isolates from cheese

Abstract

This study was conducted to investigate the presence of histamine-forming bacteria in cheeses, and to assess the impact of naturally-occurring antimicrobials on isolates' viability and histamine-forming potential. Cheese isolates' ability to produce histamine was evaluated by incubation in the presence of the histamine precursor; qualitative detection with a pH indicator and a quantitative analysis by high-performance liquid chromatography. Eight of the 114 isolates were able to produce histamine, but only one was capable of generating histamine at high concentrations. Histamine-producing isolates were identified by matrix-assisted laser desorption ionisation-time of flight mass spectrometry. Isolated strain C_MRSV_25A_4 was the microorganism with the highest capacity to produce histamine, and was identified as Lacticaseibacillus rhamnosus. The antimicrobial potential of natural antimicrobials was tested against this isolate. The results showed that carvacrol, cinnamaldehyde, eugenol, thymol and nisin exhibited remarkable bactericidal activity. These compounds’ inhibitory potential was evaluated against the histamine-generating ability of strain C_MRSV_25A_4 at three concentrations of interest: minimum bactericidal concentration (MBC), MBC/2 and MBC/4. The results on histamine-forming capability at sub-bactericidal concentrations were promising. Given these results, we propose novel antimicrobial formulations based on natural antimicrobials as efficient strategies to reduce potential microbial contamination and histamine accumulation throughout cheese production.