Selection for Antimicrobial Resistance in Foodborne Pathogens through Exposure to UV Light and Nonthermal Atmospheric Plasma Decontamination Techniques

Abstract

This study was aimed at assessing whether the repeated exposure of 12 strains of Salmonella spp., Escherichia coli, and Listeria monocytogenes to alternative nonthermal decontamination techniques with UV light (UV-C) and nonthermal atmospheric plasma (NTAP) may cause the emergence of variants showing increased resistance to clinically relevant antibiotics (ampicillin, cefotaxime, ciprofloxacin, gentamicin, streptomycin, tetracycline, erythromycin, vancomycin, and colistin). UV-C and NTAP treatments were applied on the surface of inoculated brain heart infusion (BHI) agar plates. Survivors were recovered and after 24 h of growth in BHI broth were again subjected to the decontamination treatment; this was repeated for 10 consecutive cycles. A total of 174 strain/decontamination technique/antibiotic combinations were tested, and 12 variant strains with increased resistance to one of the antibiotics studied were identified, with the increases in the MICs in Mueller-Hinton broth ranging from 2- to 256-fold. The variant strains of Salmonella spp. isolated were further characterized through phenotypic screenings and whole-genome sequencing (WGS) analyses. Most changes in susceptibility were observed for antibiotics that act at the level of protein synthesis (aminoglycosides, tetracyclines, and glycylcyclines) or DNA replication (fluoroquinolones), as well as for polymyxins. No changes in resistance to β-lactams were detected. WGS analyses showed the occurrence of sequence alterations in some antibiotic cellular targets (e.g., gyrA for ciprofloxacin-resistant variants, rpsL for a streptomycin-resistant variant), accompanied by variations in stress response regulators and membrane transporters likely involved in the nonselective efflux of antibiotics, which altogether resulted in a low- to medium-level increase in microbial resistance to several antibiotics. IMPORTANCE The emergence and spread of antibiotic resistance along the food chain can be influenced by the different antimicrobial strategies used from farm to fork. This study evidences that two novel, not yet widely used, nonthermal microbial decontamination techniques, UV light and nonthermal atmospheric plasma, can select variants with increased resistance to various clinically relevant antibiotics, such as ciprofloxacin, streptomycin, tetracycline, and erythromycin. Whole-genome analysis of the resistant variants obtained for Salmonella spp. allowed identification of the genetic changes responsible for the observed phenotypes and suggested that some antimicrobial classes are more susceptible to the cross-resistance phenomena observed. This information is relevant, since these novel decontamination techniques are being proposed as possible alternative green techniques for the decontamination of environments and equipment in food and clinical settings.

A quantitative microbial risk assessment for touchscreen user interfaces using an asymmetric transfer gradient transmission mode

“…UV itself may also poses potential health risks (though an automated system would least reduce exposure risks to staff employed to clean) [ 52 ]. Yet another risk posed by decontamination methods, including UV, is the inadvertent selection for microbial resistance [ 53 ].…”

The Effects of Natural Products and Environmental Conditions on Antimicrobial Resistance

“…Considering the human health risk due to emerging of AMR in foodborne pathogens, some of the novel ecofriendly de-contamination and sanitation strategies that maintain a high level of antimicrobial activity are used in some food-processing facilities to reduce the presence of the foodborne pathogens. However, according to the latest research progress, the exposure of Salmonella spp., E. coli , and L. monocytogenes to the novel but not yet widely used nonthermal microbial decontamination, UV light, and nonthermal atmospheric plasma can select variants with increased resistance to several clinically relevant antibiotics, which can contribute to the spread of AMR along the food chain [ 134 ]. On the other hand, many countries have banned the use of antimicrobials as animal growth promoters and the application of antimicrobials critically important in human clinical treatment in the veterinary field.…”

Role played by the environment in the emergence and spread of antimicrobial resistance (AMR) through the food chain

“…Alternatives for equipment decontamination such as the use of ultrasound (Brasil et al., 2017) cold plasma (Varilla et al., 2020) or thermal ultraviolet systems are new measures for which efficacy for ARB reduction should be supported with data. However, there are in vitro studies that report that some new alternative non thermal decontamination methods such as UV light and non‐thermal atmospheric plasma (NTAP) decontamination techniques may also lead to selection of resistance to clinically relevant antimicrobials (Álvarez‐Molina et al., 2020) although current data is not conclusive.…”