Abstract
Practical application
EP could be used for successful preservation of meat and meat products.
KSWFoodWorld
Category Archives: Research
Research – Determination of the effect of ethyl pyruvate on the surface contamination of sausage to Listeria monocytogenes by using Q‐PCR assay
Research – Evaluation of Bactericidal Effects of Phenyllactic Acid on Escherichia coli O157:H7 and Salmonella Typhimurium on Beef Meat
| ABSTRACT |
|---|
Bactericidal effects of various concentrations of phenyllactic acid on Shiga toxin–producing Escherichia coli (STEC), including E. coli O157:H7, O26:H11, O103:H2, and O121:H19, and on Salmonella Typhimurium DT104 in pure culture and microplates assays were studied. Beef cuts were surface sprayed with phenyllactic acid or lactic acid for inactivation of E. coli O157:H7 and Salmonella Typhimurium. The 1.5% phenyllactic acid inactivated all inoculated E. coli O157:H7, O26:H11, O103:H2, and O121:H19 and Salmonella Typhimurium DT104 (>6-log reduction) within 1 min of contact at 21°C, whereas 1.5% lactic acid did not result in microbial reduction. Microplate assays (for STEC and Salmonella Typhimurium DT104 at 10 to 100 CFU per well) indicated that concentrations of 0.25% phenyllactic acid or 0.25% lactic acid inhibited the growth of STEC and Salmonella Typhimurium DT104 incubated at 37°C for 24 h. Treatment of beef with 1.5% lactic acid or 1.5% phenyllactic acid reduced E. coli O157:H7 by 0.22 and 0.38 log CFU/cm2, respectively, within 5 min and reduced Salmonella Typhimurium DT104 by 0.12 and 0.86 log CFU/cm2, respectively. When meat treated with 1.5% phenyllactic acid was frozen at −20°C, inactivation of E. coli O157 and Salmonella Typhimurium DT104 was enhanced by 1.06 and 1.46 log CFU/cm2, respectively. Thus, treatment of beef with 1.5% phenyllactic acid significantly reduced the population of E. coli O157:H7 and Salmonella.
| HIGHLIGHTS |
|---|
-
Phenyllactic acid at 1.5% killed STEC and Salmonella (>6-log reduction) within 1 min.
-
The MIC of lactic and phenyllactic acids was 0.25%.
-
The bactericidal effect of phenyllactic acid on beef was enhanced by freezing.
Research – Salmonella Survival in Soil and Transfer onto Produce via Splash Events
| ABSTRACT |
|---|
Nearly one-half of foodborne illnesses in the United States can be attributed to fresh produce consumption. The preharvest stage of production presents a critical opportunity to prevent produce contamination in the field from contaminating postharvest operations and exposing consumers to foodborne pathogens. One produce-contamination route that is not often explored is the transfer of pathogens in the soil to edible portions of crops via splash water. We report here on the results from multiple field and microcosm experiments examining the potential for Salmonella contamination of produce crops via splash water, and the effect of soil moisture content on Salmonella survival in soil and concentration in splash water. In field and microcosm experiments, we detected Salmonella for up to 8 to 10 days after inoculation in soil and on produce. Salmonella and suspended solids were detected in splash water at heights of up to 80 cm from the soil surface. Soil-moisture conditions before the splash event influenced the detection of Salmonella on crops after the splash events—Salmonella concentrations on produce after rainfall were significantly higher in wet plots than in dry plots (geometric mean difference = 0.43 CFU/g; P = 0.03). Similarly, concentrations of Salmonella in splash water in wet plots trended higher than concentrations from dry plots (geometric mean difference = 0.67 CFU/100 mL; P = 0.04). These results indicate that splash transfer of Salmonella from soil onto crops can occur and that antecedent soil-moisture content may mediate the efficiency of microbial transfer. Splash transfer of Salmonella may, therefore, pose a hazard to produce safety. The potential for the risk of splash should be further explored in agricultural regions in which Salmonella and other pathogens are present in soil. These results will help inform the assessment of produce safety risk and the development of management practices for the mitigation of produce contamination.
| HIGHLIGHTS |
|---|
-
Salmonella was detected for 8 to 10 days after inoculation in soil and on produce.
-
Salmonella in soil can be detected in splash water from rainfall/irrigation events.
-
Salmonella was detected in splash water at heights of up to 80 cm.
-
Soil moisture conditions may affect the transfer potential of Salmonella.
Research – Overview of Listeriosis in the Southern African Hemisphere—Review
Listeriosis is rarely reported in the Southern African Hemispheres in spite of the increasing rate of Listeria in several foodborne outbreaks reported in advanced countries. This paper reviews the emerging trends in the spread, distribution, and epidemiology of Listeria species in foods, water, human, animals, and different environments in Southern Africa based on the appraisal of scholarly articles. In this regard, information obtained from literatures from various online databases revealed that Listeria species are commonly recovered from food, water, and human samples. Fewer articles provided information on Listeria recovered from animals (ruminants) and soil samples. Generally, reports of studies were more focused on Listeria monocytogenes among other Listeria species. To this end, reports obtained from literature on the method of identification of Listeria were mostly based on serological, classical biochemical methods and the principle of aesculin hydrolysis, usually characterized by black coloration on selective media for Listeria. These methods may not be reliable, as they could sometimes give a false positive report. Therefore, molecular methods are more reliable, accurate, could show the genetic relationship between isolates, and at the same time capable of enabling tracking the source of this pathogen should be embraced as a better substitute for the identification of Listeria in Southern African sub‐region.
Research – Bacterial contamination and prevalence of antimicrobial resistance phenotypes in raw fruits and vegetables sold in Delhi, India
Fresh fruits and vegetables contaminated with microbial pathogens can cause outbreaks of food poisoning and other enteric diseases if consumed raw. The objective of the present study was to determine the bacterial contamination and antibiotic resistance in fresh produce sold in Delhi, India. One hundred fifty samples of fruits and vegetables generally consumed raw were collected from retail and wholesale vendors of Delhi‐NCR, India. Microbial contamination was studied by culturing 25 g of each sample. Antimicrobial resistance testing was performed for isolated pathogens and resistance phenotypes determined. Overall, 97.3% of fruit and vegetables sampled were contaminated with pathogens. In over 75% of samples, coliforms were detected with Escherichia coli in 17.4%. Majority of vegetables were contaminated with coliforms particularly ginger (100%), cabbage (80%), cucumber (75%), and tomato (75%). Extended spectrum beta‐lactamases (ESBL) was detected in eight (5.7%) isolates, carbapenem resistance in four with three metallo‐β‐lactamases producers. E. coli was isolated at a significantly higher rate from retail shops viz‐a‐viz wholesale markets (p value = .04). As high level of contamination with potential human pathogens is present in fruits and vegetables sold in wholesale markets and retail shops in Delhi‐NCR, the study underlines the need for stricter regulations and implementation of standards.
Research -Shiga toxin-producing Escherichia coli survives storage in wheat flour for two years
Abstract
Wheat flour has recently been recognised as an exposure vehicle for the foodborne pathogen Shiga toxin-producing Escherichia coli (STEC). Wheat flour milled on two sequential production days in October 2016, and implicated in a Canada wide outbreak of STEC O121:H19, was analysed for the presence of STEC in November 2018. Stored in sealed containers at ambient temperature, the water activity of individual flour samples was below 0.5 at 6 months post-milling and remained static or decreased slightly in individual samples during 18 months of additional storage. STEC O121 was isolated, with the same genotype (stx2a, eae, hlyA) and core genome multilocus sequence type as previous flour and clinical isolates associated with the outbreak. The result of this analysis demonstrates the potential for STEC to persist in wheat flour at levels associated with outbreak infections for periods of up to two years. This has implications for the potential for STEC to survive in other foods with low water activity.
Research -Gut microbes alter characteristics of norovirus infection
The highly contagious norovirus causes diarrhea and vomiting and is notorious for spreading rapidly through densely populated spaces, such as cruise ships, nursing homes, schools and day care centers. There are no treatments for this intestinal virus. A new study has shown that gut microbes can tamp down or boost the severity of norovirus infection based on where along the intestine the virus takes hold.
Research -The nature of salmonella is changing — and it’s meaner
Salmonella is acting up in Michigan, and it could be a model for what’s happening in other states, according to a new Michigan State University study.
The study, appearing in Frontiers in Medicine, documents a substantial uptick in antibiotic resistant strains, and consequently, longer hospital stays as doctors work to treat the increasing virulent pathogens.
“If you get a salmonella infection that is resistant to antibiotics today, you are more likely to be hospitalized longer, and it will take you longer to recover,” said Shannon Manning, MSU Foundation professor in the Department of Microbiology and Molecular Genetics and senior author of the study. “We need better detection methods at the clinical level to identify resistant pathogens earlier so we can treat them with the right drugs the first time.”
Losing a day or more to misdiagnosis or improper treatment allows symptoms to get worse. Doctors might kill off a subpopulation of bacteria that are susceptible, but the ones that are resistant grow stronger, she added.
Salmonella is a diverse group of bacterial pathogens that causes foodborne infections. Infected patients often develop diarrhea, nausea, vomiting and abdominal pain, though some infections are more severe and can be life threatening.
When it comes to treatments, each strain reacts differently to the range of antibiotics available for prescription by doctors. So getting it right the first time is crucial.
Specifically in Michigan, doctors are seeing more strains that are resistant to ampicillin, a common antibiotic prescribed to treat salmonella. Multidrug resistance, or resistance to more than three classes of antibiotics, has also increased in Michigan and could further complicate patient treatment plans.
“We’re still uncertain as to why this is happening; it could be that these antibiotics have been overprescribed in human and veterinary medicine and that possessing genes for resistance has allowed these bacteria to grow and thrive in the presence of antibiotics,” Manning said. “Each state has its own antibiotic-resistance issues. It’s important that the medical profession remains vigilant to ever-changing patterns of resistance in salmonella and other foodborne pathogens, rather than look for a blanket national solution.”
Historically, salmonella has affected young children and the elderly, but now there’s been a rise in adult cases, suggesting that the epidemiology of the infections has changed in Michigan.
Diving into individual strains of salmonella, the team of scientists found that patients with Typhimurium were more likely to have resistant infections as were patients infected during the fall, winter or spring months.
Another distinction was revealed between the strains affecting people living in rural and urban areas. Enteritis infections tend to be higher in rural areas. This may be attributed to rural residents’ exposure to farm animals or untreated sources of water.
Each state’s salmonella population has its own personality; so every state’s approach to identifying disease drivers and effective treatments should be modified to reflect these traits.
“Our results show the importance of surveillance, monitoring resistance frequencies and identifying risk factors specific to each state and region,” Manning said. “The trends that are revealed can lead to new prevention strategies.”
Research -Influence of surface properties of produce and food contact surfaces on the efficacy of chlorine dioxide gas for the inactivation of foodborne pathogens
The objective of this study was to evaluate the influence of surface properties of produce and food contact surfaces on the antimicrobial effect of chlorine dioxide (ClO2) gas against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes. The hydrophobicity of the selected surfaces was evaluated by water contact angle measurements. White light scanning interferometry (WLSI) was used to acquire surface roughness values of each surface. Produce and food contact surfaces inoculated with foodborne pathogens were treated with 20 ppmv ClO2 gas for 5, 10, and 15 min. As treatment time increased, different levels of inactivation of the three pathogens were observed among the samples. Contact angles of produce and food contact surfaces were highly and negatively correlated with the log reduction of all three pathogens. There were generally weaker correlations between the roughness values of sample surfaces and microbial reduction compared to those between hydrophobicity and microbial reduction. The results of this study showed that surface hydrophobicity is a more important factor relative to bacterial inactivation by ClO2 gas from the surface than is surface roughness. Also, the existence of crevices with features of similar size to the pathogen cell was more important than the Ra and Rq values in the inactivation of pathogens.
Research – Population dynamics of Salmonella spp. and Shigella spp. in ready‐to‐eat Mediterranean vegetable salads
Abstract
This study evaluated the behavior of Salmonella and Shigella (5–6 log CFU/g) in tomato–cucumber (TC) salad without additives (control), TC with 1.0% lemon juice and 0.5% salt, TC with 10% wt/wt tahini, coleslaw, and toum sauce at 4, 10, or 24°C for 5 days. At 4°C, both pathogens survived well in all salads, with a 0.2–1.6 log CFU/g reduction after 5 days (except for toum sauce with >3.5 log CFU/g reduction after 4 days). At 10°C, Salmonella in the different TC salads remained constant, whereas Shigella numbers significantly increased by 1.0–1.7 log CFU/g after 5 days. Yet, both pathogens significantly decreased by 1.2–1.4 log CFU/g in coleslaw after 5 days and by >3.5 log CFU/g in toum sauce after 3 days. At 24°C, Salmonella significantly increased in TC salad without additives by 1.4 log CFU/g after 5 days and were below the detection level in the other types of salad after 5 days. However, Shigella numbers significantly increased by 1.0 log CFU/g in TC with tahini, but they significantly declined by 1.9–2.9 log CFU/g in TC salads after 5 days, and the pathogen was not detected in coleslaw and toum sauce after 4 days.
FoodWorld 