Effectiveness of Broad-Spectrum Chemical Produce Sanitizers against Foodborne Pathogens as In Vitro Planktonic Cells and on the Surface of Whole Cantaloupes and Watermelons

YOLO Algorithm for Long-Term Tracking and Detection of Escherichia Coli at Different Depths of Microchannels Based on Microsphere Positioning Assistance

The effect evaluation of the antibiotic susceptibility test based on bacterial solution is of great significance for clinical diagnosis and prevention of antibiotic abuse. Applying a microfluidic chip as the detection platform, the detection method of using microscopic images to observe bacteria under antibiotic can greatly speed up the detection time, which is more suitable for high-throughput detection. However, due to the influence of the depth of the microchannel, there are multiple layers of bacteria under the focal depth of the microscope, which greatly affects the counting and recognition accuracy and increases the difficulty of relocation of the target bacteria, as well as extracting the characteristics of bacterial liquid changes under the action of antibiotics. After the focal depth of the target bacteria is determined, although the z-axis can be controlled with the help of a three-dimensional micro-operator, the equipment is difficult to operate and the long-term changes of the target bacteria cannot be tracked quickly and accurately. In this paper, the YOLOv5 algorithm is adopted to accurately identify bacteria with different focusing states of multi-layer bacteria at the z-axis with any focal depth. In the meantime, a certain amount of microspheres were mixed into bacteria to assist in locating bacteria, which was convenient for tracking the growth state of bacteria over a long period, and the recognition rates of both bacteria and microspheres were high. The recognition accuracy and counting accuracy of bacteria are 0.734 and 0.714, and the two recognition rates of microspheres are 0.910 and 0.927, respectively, which are much higher than the counting accuracy of 0.142 for bacteria and 0.781 for microspheres with the method of enhanced depth of field (EDF method). Moreover, during long-term bacterial tracking and detection, target bacteria at multiple z-axis focal depth positions can be recorded by the aid of microspheres as a positioning aid for 3D reconstruction, and the focal depth positions can be repositioned within 3-10 h. The structural similarity (SSIM) of microscopic image structure differences at the same focal depth fluctuates between 0.960 and 0.975 at different times, and the root-mean-square error (RMSE) fluctuates between 8 and 12, which indicates that the method also has good relocation accuracy. Thus, this method provides the basis for rapid, high-throughput, and long-term analysis of microscopic changes (e.g., morphology, size) of bacteria detection under the addition of antibiotics with different concentrations based on microfluidic channels in the future.

Inactivation of Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes on alfalfa seeds by the combination treatment of vacuumed hydrogen peroxide vapor and vacuumed dry heat

We evaluated combined effects of vacuumed hydrogen peroxide vapor (VHPV) and vacuum-sealed dry heat (vacuum heat, VH) to inactivate foodborne pathogens (Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes) on alfalfa seeds. Alfalfa seeds inoculated with foodborne pathogens were sequentially treated initially with1.0 ml of 0 or 30% VHPV for 1 min and later with dry heat (DH) or VH for 2 h, and the rate of seed germination was evaluated. The combination treatment decreased the populations of three foodborne pathogens below the limit of detection (1.0 log CFU/g) on alfalfa seeds without decreasing germinability. The sequential treatment using VHPV and VH greatly reduced the total treatment time needed to inactivate pathogens on alfalfa seeds by more than 5 log CFU/g. These results demonstrate that a combination of VHPV and VH has potentially employed as a new method for pasteurization of alfalfa seeds without affecting their germinability.

Inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium in black and red pepper by vacuumed hydrogen peroxide vapour

AIMS

In this study, the efficacy of using vacuumed hydrogen peroxide vapour (VHPV) to inactivate foodborne pathogens in whole dried black pepper (Piper nigrum) and powdered dried red pepper (Capsicum annuum) was evaluated.

METHODS AND RESULTS

Black and red pepper inoculated with Escherichia coli O157:H7 and Salmonella Typhimurium were subjected to 3.81, 7.93, 12.33, 17.04 and 21.67 mg l^-1 VHPV for 1 min, and the change in pepper colour was evaluated after treatment. Pathogen quantities decreased with increasing hydrogen peroxide concentration. For black pepper, the 21.67 mg l^-1 VHPV treatment decreased E. coli O157:H7 and S. Typhimurium quantities by >6.12 and 4.52 log CFU per gram, respectively, without causing colour change. In addition, the 21.67 mg l^-1 VHPV treatment caused 4.35 and 2.36 log CFU per gram reductions in these two pathogen quantities in red pepper, respectively. During the VHPV treatment, colour values of peppers did not significantly change.

CONCLUSIONS

VHPV effectively reduced the levels of foodborne pathogens in black and red pepper while inducing minimal colour changes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Hydrogen peroxide vapour (HPV) is typically used as a sterilization method for medical devices, and many studies have confirmed the effectiveness of HPV or the gaseous phase of hydrogen peroxide on the inactivation of micro-organisms. However, using HPV for food pasteurization has rarely been studied. In the present study, we confirmed that VHPV effectively reduced the levels of pathogens in black and red pepper without colour changes.