Antibiotic Resistance Carriage Causes a Lower Survivability Due to Stress Associated with High-Pressure Treatment among Strains from Starter Cultures

Simple Summary

High-pressure processing is one of the most promising novel food preservation methods that is increasingly used in the food industry. It is applied in various food products such as dairy, meat, juices, and jams to improve safety and shelf-life by the inactivation of microorganisms and preserving of quality attributes. It is reported that the level of antibiotic resistance may influence the ability of strains to survive stress conditions. In this study, it was investigated if carrying antibiotic resistance genes affects the survival of lactic acid bacteria (Lactococcus and the former Lactobacillus) strains during high-pressure treatment. It was demonstrated that carrying antibiotic resistance genes strains showed a lower survival in response to pressure than strains carrying up to one resistance gene. The same observations were made for both genera. Appropriately selected parameters of high-pressure treatment may help in the elimination of antibiotic-resistant strains.

Abstract

High-pressure processing is one of the most promising novel food preservation methods that is increasingly used in the food industry. Its biggest advantage is that it is a nonthermal method that ensures the microbiological safety of the product while maintaining other features, including nutritional value. If products made with starter cultures are subjected to high-pressure treatment, the process parameters should be selected so as not to eliminate all microorganisms in the product. The aim of the study was to investigate if carrying antibiotic resistance genes affects the survival of lactic acid bacteria (Lactococcus and the former Lactobacillus) strains during high-pressure treatment. Survival was assessed using the plate count method. It was shown that the strains carrying antibiotic resistance genes showed a lower survival to high pressure. This might be explained by the phenomenon of fitness cost, consisting in a reduced adaptation of antibiotic-resistant strains related to metabolic expenditure. The obtained results indicate the need for further research in this field and the need to select food processing parameters depending on the strains intentionally included in the food.

Antioxidant effects of kimchi supplemented with black raspberry during fermentation protect against liver cirrhosis-induced oxidative stress in rats

BACKGROUND/OBJECTIVES

Oxidative stress is a major effector of various diseases; accordingly, antioxidants are frequently ingested in order to prevent or alleviate disease symptoms. Kimchi contains various natural antioxidants, and it is known that the functional activity varies depending on the ingredients and fermentation state. Black raspberries (BR) contain various bioactive compounds with antioxidant effects. This study investigated the antioxidant and liver-protection effects of kimchi supplemented with black raspberry juice powder (BJP).

MATERIALS/METHODS

BJP-added kimchi (BAK; at 0.5%, 1%, and 2% concentrations of BJP) and control (without BJP) were prepared and fermented at 4℃ for 4 weeks. Changes in the antioxidant effects of BAK during fermentation were investigated. In addition, the protective activity of BAK against oxidative stress was investigated in a liver cirrhosis-induced animal model in vivo.

RESULTS

BAK groups showed the acidity and pH of optimally ripened (OR) kimchi at 2 weeks of fermentation along with the highest lactic acid bacterial counts. Additionally, BAK groups displayed a higher content of phenolic compounds and elevated antioxidant activities relative to the control, with the highest antioxidant effect observed at 2 weeks of fermentation of OR 1% BAK. After feeding the OR 1% BAK to thioacetamide-induced liver cirrhosis rats, we observed decreased glutamate oxaloacetate transaminase and glutamate pyruvate transaminase activities and elevated superoxide dismutase activity.

CONCLUSIONS

These findings showed that the antioxidant effects of OR BAK and feeding of OR 1% BAK resulted in liver-protective effects against oxidative stress.

High-throughput method for a kinetics analysis of the high-pressure inactivation of microorganisms using microplates

Using microplates as pressure and cultivation vessels, a high-throughput method was developed for analyzing the high-pressure inactivation kinetics of microorganisms. The loss of viability from a high-pressure treatment, measured based on the growth delay during microplate cultivation, showed reproducibility with the conventional agar plate method and was applicable for the kinetics analysis.