Emergence of Antibiotic Resistance in Listeria monocytogenes Isolated from Food Products: A Comprehensive Review

Listeria monocytogenes is an opportunistic pathogen that has been involved in several deadly illness outbreaks. Future outbreaks may be more difficult to manage because of the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products. The present review summarizes the available evidence on the emergence of antibiotic resistance among L. monocytogenes strains isolated from food products and the possible ways this resistance has developed. Furthermore, the resistance of food L. monocytogenes isolates to antibiotics currently used in the treatment of human listeriosis such as penicillin, ampicillin, tetracycline, and gentamicin, has been documented. Acquisition of movable genetic elements is considered the major mechanism of antibiotic resistance development in L. monocytogenes. Efflux pumps have also been linked with resistance of L. monocytogenes to some antibiotics including fluoroquinolones. Some L. monocytogenes strains isolated from food products are intrinsically resistant to several antibiotics. However, factors in food processing chains and environments (from farm to table) including extensive or sub‐inhibitory antibiotics use, horizontal gene transfer, exposure to environmental stresses, biofilm formation, and presence of persister cells play crucial roles in the development of antibiotic resistance by L. monocytogenes.     

Binary mixtures of fatty alcohols and fatty acid esters as novel solid‐liquid phase change materials

The discovery of new eutectic phase change materials (PCMs) will overcome the current PCM challenges such as nonbiodegradability, super‐cooling, and limited thermal stability. This paper reports on the development of new bio‐based PCMs composed of binary mixtures of fatty acid esters and fatty alcohols at their eutectic compositions, which provide potential solid‐liquid PCMs for building applications. Six binary systems, namely 1‐dodecanol (DD) + methyl stearate (MES), DD + methyl palmitate (MEP), DD + methyl laurate (MEL), 1‐tetradecanol (TD) + MES, TD + MEP, and TD + MEL were prepared and their thermal behaviours were deliberated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), long‐term thermal stability test, and mass loss analysis. Amongst the studied systems, phase change transition temperature and latent heat of fusion of the eutectic mixtures of DD‐MES, DD‐MEP, TD‐MES, and TD‐MEP were found to be suitable for the building application with values of 22.46°C/201.91 J/g, 20.34°C/224.45 J/g, 32.05°C/209.38 J/g, and 26.72°C/210.15 J/g, respectively. The average degree of super‐cooling for all PCMs was below 2°C, and no significant changes in thermophysical properties of the developed PCMs were observed after 1000 thermal cycles.     

What Makes a Problem GP-Hard? Analysis of a Tunably Difficult Problem in Genetic Programming

This paper addresses the issue of what makes a problem genetic programming (GP)-hard by considering the binomial-3 problem. In the process, we discuss the efficacy of the metaphor of an adaptive fitness landscape to explain what is GP-hard. We indicate that, at least for this problem, the metaphor is misleading.     

Immobilized Enzymes-Based Biosensing Cues for Strengthening Biocatalysis and Biorecognition

Catalysis Letters - The versatility of immobilized enzyme systems enables rapid recovery of both product and enzyme, numerous re-uses of enzymes, continuous enzymatic processes, quick reaction...     

High hydrostatic pressure treatment for manufacturing of garlic powder with improved microbial safety and antioxidant activity

The traditional method of manufacturing garlic powder (GP) that includes simple grinding of air-dried garlic slices has problems of microbial safety and a pungent flavour for this product. Microbiologically safe GP with a less pungent flavour and better antioxidant activities was manufactured using high hydrostatic pressure (HHP), wet grinding and freeze-drying process. The numbers of total aerobic bacteria and yeasts and molds in untreated (without HHP) GP were 3.64 and 2.47 log CFU/g respectively. Garlic powder treated with 600 MPa HHP for 5 min exhibited a total aerobes count of 1.62 CFU/g and a yeasts and molds count of 1.43 log CFU/g. The diallyl disulfide content, which is responsible for the pungent odour of garlic, was also significantly reduced by HHP due to a decrease in the alliinase activity. Hence, a novel process using HHP can help to produce GP with improved microbial safety, flavour and nutrition.     

Applying Near-Infrared Spectroscopy and Chemometrics to Determine Total Amino Acids in Herbicide-Stressed Oilseed Rape Leaves

Near-infrared (NIR) spectroscopy was investigated to determine the total amino acids (TAA) in oilseed rape (Brassica napus L.) leaves under a new herbicide—propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate (ZJ0273)—stress. In full-spectrum partial least squares (PLS) models, direct orthogonal signal correction (DOSC) was the best preprocessing method. Successive projections algorithm (SPA) was used to select the relevant variables. Multiple linear regression (MLR), PLS, and least squares-support vector machine (LS-SVM) were used for calibration. The DOSC–SPA–LS-SVM model achieved the best prediction performance with correlation coefficients r = 0.9968 and root mean squares error of prediction (RMSEP) = 0.2950 comparing all SPA–MLR, SPA–PLS, and SPA–LS-SVM models. Some parsimonious direct functions were also developed based on the DOSC–SPA wavelength (1,340 nm) such as linear, index, logarithmic, binominal, and exponential functions. The best performance was achieved by direct exponential function with r = 0.9968 and RMSEP = 0.2943. The overall results indicated that NIR was able to determine the TAA in herbicide-stressed oilseed rape leaves, and the DOSC–SPA was quite helpful for the development of detection sensors and the monitoring of the growing status and herbicide effect on field crop oilseed rape.     

Quantifying Rainfall and Flooding Impacts on Groundwater Levels in Irrigation Areas: GIS Approach

Landscapes continuously irrigated without proper drainage for a long period of time frequently experience a rise in water-table levels. Waterlogging and salinization of irrigated areas are immediate impacts of this situation in arid areas, especially when groundwater salinity is high. Flooding and heavy rainfall further recharge groundwater and accelerate these impacts. An understanding of regional groundwater dynamics is required to implement land and water management strategies. The purpose of this study is to quantify the impact of flood and rain events on spatial scales using a geographic information system (GIS). This paper presents a case study of shallow water-table levels and salinity problems in the Wakool irrigation district located in the Murray irrigation area with groundwater average electrical conductivity greater than 25,000?μS/cm. This area has experienced several large flood events during the past several decades. Piezometric data are interpolated to generate a water-table surface for each event by applying the Kriging method of spatial interpolation using the linear variogram model. Spatial and temporal analysis of major flood events over the last four decades is conducted using calculated water-table surfaces to quantify the change in groundwater storage and shallow water-table levels. The drainage impact of a subsurface drainage scheme partially covering the area has also been quantified in this paper. The results show that flooding and local rainfall have a significant impact on shallow groundwater. The study also found that postflood climatic conditions (evaporation and rainfall) play a significant role in the groundwater dynamics of the area. The spatial net average groundwater recharge during the flooding events ranges from 0.19 to 0.52?ML/ha. The GIS-based techniques described in this paper can be used for net recharge estimation in semiarid regions where it is important to quantify net recharge impacts of regional flooding and local rainfall. The spatial visualization of the net recharge in a GIS environment can help prioritize management actions by local communities.