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Browsing ESS - SA - Posters apresentados em eventos científicos by Subject "Acid tolerance"
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- Assess of acid tolerance of non-typhoidal Salmonella and Enterococcus faecium from different epidemiological and genetic backgroundsPublication . Rebelo, Andreia; Mourão, Joana; Freitas, Ana R.; Campos, Joana; Peixe, Luísa; Antunes, Patrícia; Novais, CarlaAcid stress is one of the most frequently encountered hostile conditions that bacteria have to face (e.g. foodproduction-chain/feed/disinfectants/human and animal hosts). Nevertheless, acid tolerance profile of bacteria from diverse epidemiological and genetic backgrounds, including multidrug- resistant (MDR), is still poorly explored. The aim of this study was to assess the susceptibility to acidic-pH of non-typhoidal Salmonella and Enterococcus faecium (Efm) from diverse origins. We included Salmonella (n=66; 23 serotypes) and Efm (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). The minimum-growth-pH (growth-pHmin) was assessed by broth-microdilution using Mueller-Hinton-II adjusted with HCl (pH=2.0-6.5/16h-20h ±2h/37ºC) and the minimum-survival-pH (survival-pHmin) by plating the microdilution wells without visible growth in Brain-HeartInfusion-agar (BHI) (24h-48h±2h/37ºC). An Acid-Tolerance-Response (ATR) assay was performed in 3 isolates of each genera (different growth/survival-pHmin), exposing bacteria in log-phase to an acid-shockchallenge (pH=3.0/15’-Salmonella/60’-Efm) or to a pre- adaptation to acidic-pH (pH=4.5/60’ - for both bacteria) followed by an acid-shock-challenge (pH=3.0/15’-Salmonella/60’-Efm). After that a growth-pHmin and survival-pHmin assays were performed. Most Salmonella showed a growth-pHmin of 4.0 (98%- n=65/66) and a survival-pHmin between 4.0 (52%- n=34/66) and 3.5 (48%-n=32/66). In Efm, the growth-pHmin ranged between 4.5 (65%-n=48/74) and 5.0 (35%-n=26/74) and the survival-pHmin between 3.0 (15%-n=11/74), 3.5 (43%- n=32/74) and 4.0 (42%n=31/74). Only Efm isolates from food (39%-n=11/28), mostly from a poultry-processing-plant using peracetic acid as disinfectant (73%-n=8/11), presented the lowest survival-pHmin 3.0 (73%- MDR/82%-clade A2). Similar survival-pHmin=3.5-4.0 were observed for different Salmonella serotypes and Efm clades. However, a higher percentage of MDR-Salmonella (61%-n=27/44) were able to survive at pH=3.5 contrasting with nonMDR-Salmonella (23%-n=5/22) (p<0,05; Fisher-exact test). The ATR-assay (pre-adaptation acidic pH+acid shock challenge) enhanced survival-pHmin from 3 to 2.5 in 1-Efm (clade A2/MDR/from a poultry processing plant) and from 4 to 3.5 in 1-S. 4,[5],12:i:- (MDR/with mcr-1 gene/from pork meat). Our data suggest that MDR-Salmonella and Efm with diverse epidemiological and genetic backgrounds can survive to low-pH values, although differences among clades/serotypes were not detected. MDR- Salmonella showed a better ability to survive to more acidic pH than non-MDR isolates. ATR-assays revealed strainspecific ability to survive under more acidic-pH after a pre-adaptation to middle acidic- pH.
- Peracetic acid tolerance of MDR non-typhoidal Salmonella and Enterococcus faecium with diverse epidemiological and genetic backgroundPublication . Rebelo, Andreia; Duarte, Bárbara; Callejón, Ana; Peixe, Luísa; Novais, Carla; Antunes, PatríciaBacteria 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.