Abstract
Antimicrobial photodynamic therapy (aPDT) has been shown as a promising technique to inactivate foodborne bacteria, without inducing the development of bacterial resistance. Knowing that addition of inorganic salts, such as potassium iodide (KI), can modulate the photodynamic action of the photosensitizer (PS), we report in this study the antimicrobial effect of eosin (EOS) and rose bengal (RB) combined with KI against Salmonella enterica serovar Typhimurium and Staphylococcus aureus. Additionally, the possible development of bacterial resistance after this combined aPDT protocol was evaluated. The combination of EOS or RB, at all tested concentrations, with KI at 100 mM, was able to efficiently inactivate S. Typhimurium and S. aureus. This combined approach allows a reduction in the PS concentration up to 1000 times, even against one of the most common foodborne pathogenics, S. Typhimurium, a gram-negative bacterium which is not so prone to inactivation with xanthene dyes when used alone. The photoinactivation of S. Typhimurium and S. aureus by both xanthenes with KI did not induce the development of resistance. The low price of the xanthene dyes, the non-toxic nature of KI, and the possibility of reducing the PS concentration show that this technology has potential to be easily transposed to the food industry.
Highlights
The access to safe food is considered as an important requirement to guarantee the quality of human life in modern society [1,2]
Antibiotics 2019, 8, 211 resistant (MDR) bacteria have turned the control of foodborne diseases into a challenge [7,8]
The aim of this work was to investigate the antimicrobial photodynamic effect of the xanthene dyes rose bengal (RB) and EOS combined with the inorganic salt KI against Salmonella Typhimurium and
Summary
The access to safe food is considered as an important requirement to guarantee the quality of human life in modern society [1,2]. Outbreaks of foodborne diseases are one of the main causes of morbidity and mortality being considered as an international public health problem [3], causing significant social and economic impacts [4]. According to the World Health Organization (WHO), it is estimated that more than 600 million people get sick as the result of unsafe food consumption [5,6]. One of the emerging problems related with foodborne bacteria is the increase of antibiotic resistance. Antibiotics 2019, 8, 211 resistant (MDR) bacteria have turned the control of foodborne diseases into a challenge [7,8]. According to the Centre for Disease Control and Prevention [9], about 400,000 people per year are affected by foodborne infections caused by MDR bacteria in the United States.
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