Monthly Archives: May 2018

Research – Blood type affects severity of diarrhea caused by E. coli

Posted on May 31, 2018 by | Leave a comment

Science Daily 

 

A new study shows that a kind of E. coli most associated with “travelers’ diarrhea” and children in underdeveloped areas of the world causes more severe disease in people with blood type A.

The bacteria release a protein that latches onto intestinal cells in people with blood type A, but not blood type O or B, according to a study led by researchers at Washington University School of Medicine in St. Louis. A vaccine targeting that protein could potentially protect people with type A blood against the deadliest effects of enterotoxigenic E. coli (Escherichia coli) infection.

“We think this protein is responsible for this blood-group difference in disease severity,” said senior author James Fleckenstein, MD, an associate professor of medicine at Washington University. “A vaccine targeting this protein would potentially protect the individuals at highest risk for severe disease.”

The study is published May 17 in The Journal of Clinical Investigation. The work was conducted in collaboration with investigators at Johns Hopkins University, the National Institutes of Health (NIH), and the Naval Medical Research Center.

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Posted in E.coli, Food Illness, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Safety Alert, Food Testing, Uncategorized

Research – Antibiotic resistance increases with local temperature

Posted on May 31, 2018 by | Leave a comment

Nature

Bacteria that cause infections in humans can develop or acquire resistance to antibiotics commonly used against them1,2. Antimicrobial resistance (in bacteria and other microbes) causes significant morbidity worldwide, and some estimates indicate the attributable mortality could reach up to 10 million by 20502,3,4. Antibiotic resistance in bacteria is believed to develop largely under the selective pressure of antibiotic use; however, other factors may contribute to population level increases in antibiotic resistance1,2. We explored the role of climate (temperature) and additional factors on the distribution of antibiotic resistance across the United States, and here we show that increasing local temperature as well as population density are associated with increasing antibiotic resistance (percent resistant) in common pathogens. We found that an increase in temperature of 10 °C across regions was associated with an increases in antibiotic resistance of 4.2%, 2.2%, and 2.7% for the common pathogens Escherichia coli, Klebsiella pneumoniae and Staphylococcus aureus. The associations between temperature and antibiotic resistance in this ecological study are consistent across most classes of antibiotics and pathogens and may be strengthening over time. These findings suggest that current forecasts of the burden of antibiotic resistance could be significant underestimates in the face of a growing population and climate change4.

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Posted in Antibiotic Resistance, Antimicrobials, Food Safety, Food Testing, Research, Uncategorized

Research – Behavior of 11 Foodborne Bacteria on Whole and Cut Mangoes var. Ataulfo and Kent and Antibacterial Activities of Hibiscus sabdariffa Extracts and Chemical Sanitizers Directly onto Mangoes Contaminated with Foodborne Bacteria

Posted on May 30, 2018 by | Leave a comment

Journal of Food Protection

The behavior of foodborne bacteria on whole and cut mangoes and the antibacterial effect of Hibiscus sabdariffa calyx extracts and chemical sanitizers against foodborne bacteria on contaminated mangoes were investigated. Mangoes var. Ataulfo and Kent were used in the study. Mangoes were inoculated with Listeria monocytogenes, Shigella flexneri, Salmonella Typhimurium, Salmonella Typhi, Salmonella Montevideo, Escherichia coli strains (O157:H7, non-O157:H7 Shiga toxin–producing, enteropathogenic, enterotoxigenic, enteroinvasive, and enteroaggregative). The antibacterial effect of five roselle calyx extracts (water, ethanol, methanol, acetone, and ethyl acetate), sodium hypochlorite, colloidal silver, and acetic acid against foodborne bacteria were evaluated on contaminated mangoes. The dry extracts obtained with ethanol, methanol, acetone, and ethyl acetate were analyzed by nuclear magnetic resonance spectroscopy to determine solvent residues. Separately, contaminated whole mangoes were immersed in five hibiscus extracts and in sanitizers for 5 min. All foodborne bacteria attached to mangoes. After 20 days at 25 ± 2°C, all foodborne bacterial strains on whole Ataulfo mangoes had decreased by approximately 2.5 log, and on Kent mangoes by approximately 2 log; at 3 ± 2°C, they had decreased to approximately 1.9 and 1.5 log, respectively, on Ataulfo and Kent. All foodborne bacterial strains grew on cut mangoes at 25 ± 2°C; however, at 3 ± 2°C, bacterial growth was inhibited. Residual solvents were not detected in any of the dry extracts by nuclear magnetic resonance. Acetonic, ethanolic, and methanolic roselle calyx extracts caused a greater reduction in concentration (2 to 2.6 log CFU/g) of all foodborne bacteria on contaminated whole mangoes than the sodium hypochlorite, colloidal silver, and acetic acid. Dry roselle calyx extracts may be a potentially useful addition to disinfection procedures of mangoes.

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Posted in E.coli, E.coli O157, E.coli O157:H7, food bourne outbreak, Food Illness, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Poisoning, Food Safety, Food Testing, Food Toxin, foodborne disease, Foodborne Illness, foodborne outbreak, foodbourne outbreak, Salmonella, Uncategorized

Research – Notes from the Field: Investigation of an Outbreak of Salmonella Paratyphi B Variant L(+) tartrate + (Java) Associated with Ball Python Exposure — United States, 2017

Posted on May 30, 2018 by | Leave a comment

File:Ball python lucy.JPG

Mokele at English Wikipedia

CDC  

 

In July 2017, PulseNet, the national molecular subtyping network for foodborne disease surveillance, identified a cluster of five Salmonella Paratyphi B variant L(+) tartrate + (Java) clinical isolates that were indistinguishable by pulsed-field gel electrophoresis (PFGE). Initial questionnaires administered by state and local health department investigators indicated animal exposure as a possible source of infection, with all five patients reporting snake exposure. An outbreak investigation was initiated to identify the source of infection.

A case was defined as isolation of Salmonella Paratyphi B variant L(+) tartrate + (Java) from June 17, 2017, to July 23, 2017, with a PFGE enzyme pattern indistinguishable from the outbreak strain. A snake-specific questionnaire regarding snake type, snake purchase location, and reptile food, including feeder rodents, was developed and administered to patients by state and local health department investigators. In addition, animal and environmental sampling was conducted at patient residences. Traceback of patients’ snakes was conducted by contacting snake purchase locations to identify common suppliers. Finally, whole genome sequencing (WGS) was performed on clinical, environmental, animal, and pet food isolates to further characterize their genetic relatedness, measured in single nucleotide polymorphism (SNP) differences (1).

Five cases were identified in four states: one each in Arizona, Oklahoma, and Oregon, and two in Indiana from different households with no epidemiologic link. Median patient age was 10 years (range = <1–40 years), and four were female. No patient was hospitalized, and no deaths occurred. Five patients or their proxies completed the snake-specific questionnaire, four of whom reported exposure to a ball python in the residence. Ball python sampling occurred in the Arizona, Oregon, and one of the Indiana patient residences by sampling the python cloaca, environment, water, and bedding. Feeder rodent sampling occurred in the Arizona and Indiana patient residences. No common suppliers of either ball pythons or feeder rodents were identified by traceback.

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Posted in Salmonella, Uncategorized

Research – Microbiological survey of field‐grown and retail lettuce in Beijing

Posted on May 29, 2018 by | Leave a comment

Wiley Online Eurofins Food Testing UK

Abstract

About 108 retail and 101 field‐grown lettuce samples from across Beijing were examined. These samples were analyzed for their aerobic plate counts, coliform counts, fecal flora counts, and presence of pathogenic bacteria. Samples included retail leaf (n = 56), retail head (n = 52), field‐grown leaf (n = 54), and field‐grown head lettuce (n = 47). The number of aerobic colonies of retail leaf lettuce was significantly higher than that of retail head lettuce throughout the year, with the exception of December. The means of retail leaf lettuce aerobic plate counts varied from 4.87 to 7.03 log10 cfu/g. For retail head lettuce, the mean count of aerobic microbiological populations varied from 4.33 to 6.33 log10 cfu/g. The aerobic microbiological populations of field‐grown lettuce were lower than those of retail lettuce in the same month. The mean count of field‐grown head lettuce was 5.53 log10 cfu/g. The mean count of retail head lettuce was 5.92 log10 cfu/g. The mean of the coliform counts ranged from <0.47 to 2.85 log10cfu/g. Leaf and retail lettuce had significantly higher coliform, fecal flora, and Escherichia coli counts than head and field‐grown lettuce. The detection rate of E. coli was directly proportional to that of fecal flora. No E. coli O157:H7 or Salmonella spp. were detected in these lettuce samples.

Practical applications

It is generally agreed that microbial contamination of lettuce will arise if there is improper operation in the process of its storage, transportation, and shelves sale. As lettuce is usually eaten raw, microbes can cause people to suffer from illnesses. Therefore, it is of critical importance to monitor the presence of microbes closely. In this study, the number of aerobic plate count in lettuce from different sources was examined. It was found that freshly picked lettuce had fewer microorganisms than retail lettuce had; lettuce harvested in low‐temperature seasons has fewer microorganisms than that in hot seasons. The suggestion is that cold chain transport is the best way for lettuce transportation, especially in summer and aseptic packaging is helpful to reduce contact pollution.

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Posted in E.coli, Research, Salmonella, Uncategorized

Research- Occurrence of Toxigenic Fungi and Mycotoxins on Root Herbs from Chinese Markets

Posted on May 29, 2018 by | Leave a comment

Journal of Food Protection Aspergillus

Herbs derived from roots, leaves, flowers, or fruits of plants are unavoidably contaminated with fungi and mycotoxins during growth, harvest, and storage, thereby posing a health threat to humans. Especially, root herbs (RHs) are more easily contaminated with fungi and mycotoxins because the roots are in direct contact with the soil. Here, we investigated the occurrence of fungi, aflatoxins (AFs), and ochratoxin A (OTA) in eight RHs that are used as medicines, beverages, dietary supplements, and functional foods in China and other countries. Morphological observation and MultiGeneBlast (β-tubulin and calmodulin) were used to identify the potentially toxigenic fungi. Of the 48 samples tested, all were contaminated by fungi, and 1,844 isolates belonging to 25 genera were detected. The genera Aspergillus and Penicillium, which contain potentially toxigenic fungal species, represented a frequency of 10 and 25%, respectively. Thirty-three isolates of Aspergillus flavus, Aspergillus parasiticus, Aspergillus niger, and Penicillium polonicum were arbitrarily selected for analysis of their toxigenic potential. Five of 13 isolates of A. flavus and 1 isolate of A. parasiticus produced AFs, whereas OTA production was not detected for any of the isolates of A. niger and P. polonicum. The occurrence of AFs and OTA in the 48 samples of eight RHs was tested by ultraperformance liquid chromatography–tandem mass spectrometry; 37.50% of samples from six RHs were contaminated with AFs and 16.67% of samples from four RHs were contaminated with OTA. Seven (14.58%) and four (8.33%) samples of ginseng, polygala, and liquorice exceeded the permissible limits of aflatoxin B1 and AFs, respectively. Because ginseng, polygala, and liquorice are widely used as herbs, dietary supplements, and functional foods, the high frequency of AF contamination of these herbs indicated by our current study warrant attention to raise public awareness.

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Posted in Aflatoxin, Biotoxin, Food Hygiene, Food Inspections, Food Microbiology, Food Microbiology Blog, Food Safety, Food Testing, Food Toxin, mold, Moulds, Mycotoxin, Ochratoxin, Tetrodotoxin, Toxin, Uncategorized

Reasearch – Viable-but-Nonculturable Listeria monocytogenes and Salmonella enterica Serovar Thompson Induced by Chlorine Stress Remain Infectious

Posted on May 28, 2018 by | Leave a comment

mbioasm 

ABSTRACT

The microbiological safety of fresh produce is monitored almost exclusively by culture-based detection methods. However, bacterial food-borne pathogens are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses such as chlorine, which is commonly used for fresh produce decontamination. Here, complete VBNC induction of green fluorescent protein-tagged Listeria monocytogenes and Salmonella enterica serovar Thompson was achieved by exposure to 12 and 3 ppm chlorine, respectively. The pathogens were subjected to chlorine washing following incubation on spinach leaves. Culture data revealed that total viable L. monocytogenes and Salmonella Thompson populations became VBNC by 50 and 100 ppm chlorine, respectively, while enumeration by direct viable counting found that chlorine caused a <1-log reduction in viability. The pathogenicity of chlorine-induced VBNC L. monocytogenes and Salmonella Thompson was assessed by using Caenorhabditis elegans. Ingestion of VBNC pathogens by C. elegans resulted in a significant life span reduction (P = 0.0064 and P < 0.0001), and no significant difference between the life span reductions caused by the VBNC and culturable L. monocytogenes treatments was observed. L. monocytogenes was visualized beyond the nematode intestinal lumen, indicating resuscitation and cell invasion. These data emphasize the risk that VBNC food-borne pathogens could pose to public health should they continue to go undetected.

IMPORTANCE Many bacteria are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses. VBNC cells cannot be detected by standard laboratory culture techniques, presenting a problem for the food industry, which uses these techniques to detect pathogen contaminants. This study found that chlorine, a sanitizer commonly used for fresh produce, induces a VBNC state in the food-borne pathogens Listeria monocytogenes and Salmonella enterica. It was also found that chlorine is ineffective at killing total populations of the pathogens. A life span reduction was observed in Caenorhabditis elegans that ingested these VBNC pathogens, with VBNC L. monocytogenes as infectious as its culturable counterpart. These data show that VBNC food-borne pathogens can both be generated and avoid detection by industrial practices while potentially retaining the ability to cause disease.

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Posted in Listeria, Listeria monocytogenes, Listeria welshimeri, listeriosis, Research, Salmonella, Uncategorized, VBNC Viable but none culturable

Research – Thermal Inactivation of Shiga Toxin–Producing Escherichia coli in Ground Beef with Varying Fat Content

Posted on May 27, 2018 by | Leave a comment

Journal of Food Protection

Decimal reduction time (D-value) was calculated for six non-O157 Shiga toxin–producing Escherichia coli (STEC) in a laboratory medium and ground beef. For the laboratory medium, an overnight culture of each strain of STEC was divided into 10-mL sample bags and heated in a water bath for a specific time on the basis of the temperatures. Survival curves were generated by plotting the surviving bacterial population against time, and a linear-log primary model was used to estimate the D-values from survival curves. The z-values (the temperature raised to reduce the D-value by one-tenth) were calculated by plotting the log D-values against temperature. Similarly, for ground beef, six fat contents, 5, 10, 15, 20, 25, and 30% of ground beef were formulated for this study. Inoculated meat was divided into 5-g pouches and submerged in a water bath set at specific temperatures (55, 60, 65, 68, and 71.1°C). The average D-value for these strains in a laboratory medium was 17.96 min at 55°C, which reduced significantly (P < 0.05) to 1.58 min at 60°C, and then further reduced (P < 0.05) to 0.46 min at 65°C. In ground beef, a negative correlation (P < 0.05) between fat content of ground beef and D-values was observed at 55°C. However, at temperatures greater than 60°C, there was no impact (P > 0.05) of fat content of ground beef on the thermal resistance of non-O157 STECs. Irrespective of the fat content of ground beef, the D-values ranged from 15.93 to 11.69, 1.15 to 1.12, and 0.14 to 0.09 min and 0.05 at 55, 60, 65, and 68°C, respectively. The data generated from this study can be helpful for the meat industry to develop predictive models for thermal inactivation of non-O157 STECs in ground beef with varying fat content.

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Posted in E.coli, Food Microbiology, Food Safety, Food Testing, Research, Uncategorized

Research – Inactivation of Escherichia coli by Ultrasound Combined with Nisin

Posted on May 27, 2018 by | Leave a comment

Journal of Food Protection ecoli

The aim of this study was to investigate the inactivation of nonpathogenic Escherichia coli in nutrient broth and milk through the use of either ultrasound (US) alone or US combined with nisin (US + nisin) treatments. The E. coli cells were treated at 0 to 55°C, 242.04 to 968.16 W/cm2 for 0 to 15 min. The results showed that the inactivation of E. coli by US and US + nisin increased when the temperature, US power density, and treatment time were increased. The inactivation kinetics of E. coli in nutrient broth by US and US + nisin both conformed to linear models. The largest reductions of 2.89 and 2.93 log cycles by US and US + nisin, respectively, were achieved at 968.16 W/cm2 and at 25°C for 15 min. The suspension media of the E. coli cells influenced the inactivation effect of US, while the growth phases of E. coli cells did not affect their resistance to US. Under all experiment conditions of this study, the differences between US and US + nisin in their respective inactivation effects on E. coli were not obvious. The results suggested that nisin had either no effect at all or a weak synergistic effect with US and that the E. coli cells were inactivated mainly by US, thus indicating that the inactivation of E. coli by US is an “all or nothing” event.

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Posted in E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Safety, Food Testing, Uncategorized

Research – Response surface modeling for the inactivation of Bacillus cereus on cooked spinach by natural antimicrobials at various temperatures

Posted on May 27, 2018 by | Leave a comment

Wiley Online Library

Abstract

This study was conducted to investigate the growth of Bacillus cereus on cooked spinach with natural antimicrobial substances (0.00–0.02% thymol, 0.60–1.30% acetic acid, and 0.00–0.05% nisin) at various temperatures (15, 25, and 35°C) in order to find the best combination of inhibition. Response surface modeling with the Gompertz model equation was used to describe the growth of B. cereus vegetative cells on cooked spinach with natural antimicrobial substances as a function of temperature. The specific growth rate of B. cereus at the highest concentration of thymol (0.02%) was lower than with the other treatments. In particular, the lag time of B. cereus was the longest for combinations thymol 0.02%, acetic acid 0.68%, and nisin 0.03% at 25°C. The predicted values were shown to be significantly in good agreement with experimental values because the adjusted determination coefficient ( urn:x-wiley:01496085:media:jfs12484:jfs12484-math-0001) was 0.91 and the level of significance was p < .0001. Besides, bias factor (Bf) values of the SGR and LT for B. cereus were 1.07 and 1.10, respectively, indicating that they were mostly at the acceptable level. In sensory evaluation, appearance and color of cooked spinach with antimicrobial substances was similar to the control.

Practical applications

Natural antimicrobials could be used as the preservation method to improve the food safety of cooked foods such as cooked vegetables.

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Posted in Uncategorized