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Category Archives: Pathogen
Research – Effect of UVC light-emitting diodes on pathogenic bacteria and quality attributes of chicken breast
This study aimed to investigate the inactivation of foodborne pathogens and the quality characteristics of fresh chicken breasts after Ultraviolet-C light-emitting diode (UVC-LED) treatment. Fresh chicken breasts were separately inoculated with Salmonella Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes at an initia population of 6.01, 5.80, and 6.22 log 10 CFU/cm 2 , respectively, then were treated by UVC-LED at 1000 to 4000 mJ/cm 2 . UVC-LED irradiation could inactivate the tested bacteria in a dose-dependent manner. After UVC-LED treatment at 4000 mJ/cm 2 , the populations of S . Typhimurium, E . coli O157:H7, and L . monocytogenes on chicken breasts were decreased by 1.90, 2.25, and 2.18 log 10 CFU/cm 2 , respectively. No significant ( P > 0.05) changes were found in the color, pH value, texture properties, and thiobarbituric acid reactive substances (TBARS) values of chicken breasts following the UVC-LED radiation at doses up to 4000 mJ/cm 2 . Overall, this study indicates that UVC-LED is a promising technology to reduce the number of microorganisms while maintaining the physico-chemical characteristics of poultry meat.
Research – Bacteriophages for detection and control of foodborne bacterial pathogens—The case of Bacillus cereus and their phages
Bacillus cereus is among the primary food‐poisoning pathogenic bacterium that causes diarrhea and emetic types of diseases throughout the world. Recent advances show that bacteriophages become important tools in detection and control of foodborne bacterial pathogens in foods. They gain the interest of researchers for the food industries mainly because they are host‐specific and harmless to humans. Studies showed that bacteriophages could be employed as natural or engineered, whole or part, and temperate or virulent type in designing a range of tools for the detection and control of foodborne bacterial pathogens. This article discusses the recent methods and advances in the utilization strategies of bacteriophages in detection and control of foodborne pathogens, with particular focus on B. cereus pathogen. Moreover, the article presents the latest and relevant information of B. cereus‐infecting phages with respect to their potential applications in foods to address food safety issues. It also reflects future research directions by indicating gap of studies on the area.
Research – Contamination of ready-to-eat street food in Pakistan with Salmonella spp.: Implications for consumers and food safety
Microbial contamination of street food sold in Quetta.
38% (121/320) of ready-to-eat food samples were contaminated with microbial pathogens.
Food quality was worse in summer months.
Salmonella enteritidis and Salmonella typhimurium were identified by multiplex polymerase chain reaction.
Isolated pathogens showed antibiotic resistance.
Ready-to-eat (RTE) food sold in Quetta, Pakistan was assessed for microbial contamination.
Equal numbers of samples were collected from four categories of RTE food – burgers, shawarma, pizza and sandwiches – from January 2018 to December 2018. Microbial contamination of individual food samples was assessed by quantifying the total aerobic count obtained from plating samples on bacterial growth medium. Salmonella spp. serovars were identified using polymerase chain reaction.
Approximately 38% (121/320) of RTE food samples were not fit for human consumption. The most contaminated type of RTE food was shawarma (49%). Microbial contamination of food samples was higher in summer compared with the other seasons. Approximately 40% (49/121) of food samples that were not fit for human consumption were contamined with Salmonella spp. Salmonella enteritidis (69%) and Salmonella typhimurium (31%) were the only serovars among the samples testing positive for Salmonella spp. Of the 49 samples with high microbial counts, S. enteritidis was present in 34 samples and S. typhimurium was present in 15 samples. The antibiotic sensitivity results demonstrated that both S. enteritidis and S. typhimurium were resistant to amoxicillin. In addition, S. enteritidis was resistant to chloramphenicol and erythromycin, and S. typhimurium presented high resistance to erythromycin. Both S. typhimurium and S. enteritidis were highly sensitive to kanamycin.
RTE food sold by street vendors in Quetta was found to be contaminated with Salmonella spp. and poses a great health risk to consumers. As such, consumption should be avoided, and the health authorities should take stringent action to ensure the quality of street food in order to reduce the healthcare burden.
In the vegetable processing industry, the application of chlorine dioxide (ClO2) as a disinfectant solved in washing water to eliminate undesirable microorganisms harmful to consumers’ health and the shelf life of produce has been discussed for years. The disinfection efficacy depends on various factors, e.g., the location of microorganisms and the organic load of the washing water. The present study analyzed the sanitation efficacy of various concentrations of water-solved ClO2 (cClO2: 20 and 30 mg L−1) on Escherichia coli (1.1 × 104 cfu mL−1), Salmonella enterica (2.0 × 104 cfu mL−1) and Listeria monocytogenes (1.7 × 105 cfu mL−1) loads, located on the leaf surface of iceberg lettuce assigned for fresh-cut salads. In addition, it examined the potential of ClO2 to prevent the cross-contamination of these microbes in lettuce washing water containing a chemical oxygen demand (COD) content of 350 mg L−1 after practice-relevant washing times of 1 and 2 min. On iceberg leaves, washing with 30 mg L−1 ClO2 pronouncedly (1 log) reduced loads of E. coli and S. enterica, while it only insignificantly (<0.5 × log) diminished the loads of L. monocytogenes, irrespective of the ClO2 concentration used. Although the sanitation efficacy of ClO2 washing was only limited, the addition of ClO2 to the washing water avoided cross-contamination even at high organic loads. Thus, the application of ClO2 to the lettuce washing water can improve product quality and consumer safety. View Full-Text
The number of farmers markets registered by the U. S. Department of Agriculture (USDA) has seen a significant increase, jumping from 1,755 in 1994 to 8,771 in 2019. Microbial studies have found evidence that produce sold at farmers can yield higher microbial counts than their retail counterparts; however, no previous literature explored the efficacy of microbial (bacteria and virus) persistence on a variety of different farmers market fomites over a 2-month period. The objectives of the current study were to conduct observations to determine the most commonly used food contact surface fomites at farmers markets and to investigate the persistence of key foodborne pathogens ( Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and MS2 bacteriophage) on these fomites. A repeated-measures analysis of variance was used to compare the persistence rates of foodborne pathogens on cardboard, plastic, tablecloth, molded pulp fiber, and wicker baskets used to store, transport, and display produce at farmers markets. In general, molded pulp fiber, plastic and wicker surface materials supported the persistence of foodborne pathogens the most, with S. aureus demonstrating the highest log concentrations over the longest period of time. Additionally, Salmonella and E. coli strains also persisted for a significant period of time (approximately 32-days) on all fomites with the exception of tablecloth. The results suggest that foodborne pathogens on these fomites pose a high-risk of cross-contamination particularly if the fomites cannot be washed, rinsed, and sanitized effectively (e.g. cardboard). The results highlight the need avoid using porous, single-use storage containers such as cardboard, molded pulp fiber and wicker containers for extended periods of time and suggest the use of easily cleanable materials such as plastic containers.
On March 21, 2017, field investigating team was sent to Cayapa Village, Abra, Philippines due to an increasing cases of foodborne illness. An epidemiologic investigation was conducted to verify the diagnosis, establish existence of outbreak, identify risk factors, and recommend control and prevention measures.
The epidemic curve indicates a point source outbreak of gastrointestinal Anthrax. We found valid statistical and temporal association of eating by-product of dead water buffalo and gastrointestinal Anthrax. Though, bacterial isolation were both negative for human specimen and environmental sample, all clinical manifestations were consistent with Bacillus anthracis rather than other foodborne bacterial pathogens. Hence, we conducted massive information education campaign sick or dead animal by-product should not be sold or eaten and properly handled and disposed.
Chickens are the most common birds on Earth and colibacillosis is among the most common diseases affecting them. This major threat to animal welfare and safe sustainable food production is difficult to combat because the etiological agent, avian pathogenic Escherichia coli (APEC), emerges from ubiquitous commensal gut bacteria, with no single virulence gene present in all disease-causing isolates. Here, we address the underlying evolutionary mechanisms of extraintestinal spread and systemic infection in poultry. Combining population scale comparative genomics and pangenome-wide association studies, we compare E. coli from commensal carriage and systemic infections. We identify phylogroup-specific and species-wide genetic elements that are enriched in APEC, including pathogenicity-associated variation in 143 genes that have diverse functions, including genes involved in metabolism, lipopolysaccharide synthesis, heat shock response, antimicrobial resistance and toxicity. We find that horizontal gene transfer spreads pathogenicity elements, allowing divergent clones to cause infection. Finally, a Random Forest model prediction of disease status (carriage vs. disease) identifies pathogenic strains in the emergent ST-117 poultry-associated lineage with 73% accuracy, demonstrating the potential for early identification of emergent APEC in healthy flocks.
Wine and alcoholic apple cider are commonly back-sweetened with unpasteurized juice to produce fresh, natural, and palatable sweetened alcoholic beverages. Foodborne pathogens may be introduced from unpasteurized juice into alcoholic beverages through this back-sweetening process. Although pathogens generally do not survive under low pH conditions or high alcohol environment, the die-off of these pathogens has not been established to ensure the safety of the products. To determine the safety of these back-sweetened beverages, we evaluated the survival of three common foodborne pathogens, E. coli O157:H7, Salmonella enterica , and Listeria monocytogenes in modified white grape juice and apple juice models. White grape juice and apple juice were modified with hydrochloric acid/sodium hydroxide and ethanol to achieve conditions that are similar to the back-sweetened white wine and alcoholic apple cider. Pathogen cocktails were inoculated separately into modified juice models and their survival in the juice models were recorded over a 96-hour period. Our results show that a combination of low pH and high ethanol content resulted in a faster pathogen die-off compared to higher pH and lower ethanol conditions. The holding times required for different combinations of pH and ethanol concentration for each juice model to achieve 5-log reduction were reported. This research provides data to validate pathogen die-off to comply with Juice HACCP 5-log pathogen inactivation requirements for back-sweetened wine and alcoholic apple cider.
Research – Application of a Novel Lytic Podoviridae Phage Pu20 for Biological Control of Drug-Resistant Salmonella in Liquid Eggs
Salmonella is a globally distributed zoonotic pathogen. Among them, S. Pullorum is a host-specific pathogen that seriously affects the development of the poultry breeding industry in China. It mainly infects chickens and can cause white scabs, and the mortality rate after infection is almost 100%. As antibiotics are widely used in animal feed and other production processes, Salmonella resistance has gradually increased. Therefore, there is an increasing need to develop new technologies to control multi-drug resistant (MDR) pathogens and confirm their actual effectiveness in the target food matrix. Bacteriophage can efficiently and specifically lyse bacteria, and will be a potential bactericide to replace antibiotics. In this study, 34 strains of Salmonella bacteriophages were isolated from environmental resources. Therein, phage Pu20 with the widest host spectrum had the strongest ability to lyse tested Salmonella strains. Further studies showed that Pu20 had high pH tolerance and heat resistance, short incubation period. Pu20 can effectively inhibit the growth of two strains of MDR Salmonella in liquid egg white and yolk at 4 ℃ and 25 ℃, respectively. According to morphological and phylogenetic analysis, Pu20 belongs to the Podoviridae family. Genomic analysis of Pu20 indicates a linear 59435 bp dsDNA sequence with no homology to virulence or antibiotic resistance-related genes. Together, these results sheds light on the potential biocontrol application value of Pu20 in food products.