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Advisor(s)
Abstract(s)
Bacteria face multiple stresses in different contexts and developed diverse mechanisms to overcome them individually or through events of cross-tolerance. Peracetic acid (PAA) is widely used in the food-chain as antiseptic/disinfectant (20-3000 mg/mL) and induces oxidative-stress in bacteria. However, data about bacterial tolerance to PAA (PAAT) and the conditions inducing such tolerance remain scarce. Here we assess PAAT of non-typhoidal Salmonella and Enterococcus faecium from diverse epidemiological and genetic backgrounds and determine if induction with PAA and copper-Cu (also associated with oxidativestress and widely used in food-animal production settings) increase PAAT. We included Salmonella (n=66; 23 serotypes) and E. faecium (n=74; clades A1/A2/B) recovered from human (n=54), food-animal production setting (n=20), food (n=56) and environment (n=10) (1997-2018; 6 countries). Most of the isolates were MDR (E. faecium 76%-n=56/74; Salmonella 67%-n=44/66). The MICPAA was performed by broth-microdilution (ISO20776-1:2006; range: 40-140mg/L) followed by MBCPAA determination (NCCLS:1999) (37ºC/48h; 2 replicas/isolate). Induction assays by PAA and by CuSO4 were performed in 6 Salmonella and 6 E. faecium (human, food-animal production settings and food sources; with/without Cu tolerance genes: 3 Salmonella with pcoD+silA genes and 3 E. faecium with tcrB+cueO genes; diverse MIC/MBCPAA) by exposing bacteria (log-phase: 3-4h) to sub-inhibitory PAA or CuSO4 concentrations (up to 10 and 100 times less the MICPAA/Cu) followed by MICPAA assay. MICPAA= 40-60 mg/L and MBCPAA= 50-80 mg/L (MIC90= 60 mg/L; MBC90= 70 mg/L) were observed in Salmonella, and a MICPAA= 60-100 mg/L and MBCPAA= 80-140 mg/L (MIC90= 90 mg/L; MBC90= 140 mg/L) in E. faecium. No differences in MIC/MBCPAA were observed among serotypes/clades, sources or MDR/non-MDR bacteria. The induction with PAA or CuSO4 did not affected the MIC/MBC of Salmonella and E. faecium. Our data suggest that a high number of MDR Salmonella and E. faecium are able to survive to PAA concentrations used in the food-processing industries. Exposure to sub-inhibitory PAA and CuSO4 concentrations, under the tested conditions, does not affect the ability to survive to PAA, in both bacteria. However, further studies are needed to better understand the environmental conditions that can challenge the efficacy of these and other antimicrobial compounds.
Description
Keywords
Peracetic Acid tolerance MDR non-typhoidal Salmonella Enterococcus faecium
Citation
Rebelo, A., Duarte, B., Calléjon, A., Peixe, Luísa, Novais, C., & Antunes, P. (2019). Peracetic Acid tolerance of MDR non-typhoidal Salmonella and Enterococcus faecium with diverse epidemiological and genetic background. Book of abstracts - Congress of Microbiology and Biotechnology 2019 - MICROBIOTEC 19, 477.
Publisher
Universidade de Coimbra/ Sociedade Portuguesa de Microbiologia/ Sociedade Portuguesa de Biotecnologia