Production, Recovery and Characterization of an Enterocin with Anti-Listerial Activity Produced by Enterococcus hirae OS1

 Background and objective: Lactic acid bacteria, used in food processing for a long time, can produce various metabolites during their growth, including bacteriocins. These antimicrobials, used as natural bio-preservatives, enhance the food safety. The objective of this study was to assess lactic acid bacteria bacteriocins with anti-listerial activity and optimize their production and recovery process.Material and methods: Isolate was identified using conventional assays (morphological and biochemical characteristics) and 16S rRNA gene sequencing. Lactic acid bacteria bacteriocins were characterized based on their physicochemical properties (nature, pH stability and thermo-resistance). The production process was based on optimization of media components (growth media and addition of glucose, nitrogen source and tween 20) and culture conditions (temperature, pH, agitation and inoculum size). Furthermore, optimization of the recovery process was studied using ion exchange chromatography on amberlite IRC-50 (effects of resin size and NaCl eluent concentration).Results and conclusion: Enterococcus hirae OS1 was isolated from Moroccan raw cow milk as bacteriocinogenic strain. After optimization of the bacteriocin production process, results showed that the key parameters for increasing of production included temperature of 30°C, pH of 6.5 and inoculum size of 5%. Production with whey-based and economic food-grade substrate allowed high production of enterocin OS1 (1,600 AU ml-1) (P<0.001). Simultaneous addition of glucose (1%) and Tween 20 (1%) increased enterocin titer significantly (5,866 AU ml-1) (P<0.01). Recovery efficiency increased with use of 70% amberlite IRC-50 resin and elution with 2M NaCl. Indeed, recovery of 75.4% of bacteriocin was achieved in comparison to 15.7% of bacteriocin without optimization. This promises achieving high quantities of enterocin at low costs.Conflict of interest: The authors declare no conflict of interest

Evaluation of the Performances of the Rapid Test RESIST-5 O.O.K.N.V Used for the Detection of Carbapenemases-Producing Enterobacterales

Background: The emergence of carbapenemase-producing Enterobacterales (CPE) is a public health problem, requiring rapid and reliable diagnostic methods. The aim is to compare the new rapid immunochromatographic (IC) test: RESIST-5 O.O.K.N.V with PCR and the predictive model of EUCAST algorithm for the detection of CPE. Methods: A longitudinal cross-sectional study was carried out in the bacteriology-virology laboratory of the Ibn Rochd-Casablanca University Hospital, from 1 February 2019 to 28 February 2020, concerning strains with reduced sensitivity to Ertapenem. The identification of bacterial species was carried out according to the standard criteria of microbiology and antibiogram according to CASFM-EUCAST 2019 recommendations. The sensitivity and specificity of the rapid IC test were calculated. Results: The results of the new IC test showed a sensitivity and specificity of 100% for the detection of OXA-48 and NDM. These carbapenemases were detected simultaneously with a sensitivity and specificity of 100%. OXA-48 was the most common carbapenemas found (36%), followed by NDM (24%) and (13.4%) cases of OXA-48 and NDM coexistence. Conclusion: The rapid IC test could be a rapid and effective diagnostic tool for detecting the most common carbapenemases in our context, and to accelerate the implementation of adequate antibiotic therapy and infection control measures in patients with CPE infection

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