Category Archives: Microbiology

Research – Impact of Pipe Material and Temperature on Drinking Water Microbiome and Prevalence of Legionella, Mycobacterium, and Pseudomonas Species

Posted on February 4, 2023 by | Leave a comment

MDPI

Abstract

In drinking water distribution systems (DWDSs), pipe material and water temperature are some of the critical factors affecting the microbial flora of water. Six model DWDSs consisting of three pipe materials (galvanized steel, copper, and PEX) were constructed. The temperature in three systems was maintained at 22 °C and the other 3 at 32 °C to study microbial and elemental contaminants in a 6-week survey using 16S rRNA next-generation sequencing (NGS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). Pipe material and temperature were preferentially linked with the composition of trace elements and the microbiome of the DWDSs, respectively. Proteobacteria was the most dominant phylum across all water samples ranging from 60.9% to 91.1%. Species richness (alpha diversity) ranking was PEX < steel ≤ copper system and elevated temperature resulted in decreased alpha diversity. Legionellaceae were omni-prevalent, while Mycobacteriaceae were more prevalent at 32 °C (100% vs. 58.6%) and Pseudomonadaceae at 22 °C (53.3% vs. 62.9%). Heterogeneity between communities was disproportionately driven by the pipe material and water temperature. The elevated temperature resulted in well-defined microbial clusters (high pseudo-F index) in all systems, with the highest impact in PEX (10.928) followed by copper (9.696) and steel (5.448). Legionellaceae and Mycobacteriaceae are preferentially prevalent in warmer waters. The results suggest that the water temperature has a higher magnitude of impact on the microbiome than the pipe material.

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Posted in Contaminated water, Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Legionella, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Mycobacterium, Pseudomonas, Water, water microbiology, Water Safety

Research – Lysine-Derived Maillard Reaction Products Inhibit the Growth of Salmonella enterica Serotype Typhimurium

Posted on February 4, 2023 by | Leave a comment

MDPI

Abstract

An emerging consumer trend to purchase minimally heated and ready-to-eat food products may result in processing methods that do not effectively reduce pathogenic populations. Crude Maillard reaction products (MRPs) are naturally generated compounds that have been shown to display antimicrobial effects against pathogens. Crude MRPs were generated from reducing sugars (fructose (Fru), glucose (Glc), ribose (Rib) or xylose (Xyl)) with lysine and the melanoidin equivalence was measured using an absorbance of 420 nm (Ab420). The relative antimicrobial activity of each MRP was measured by examining both the length of lag phase and maximum growth rate. MRPs were found to significantly shorten the lag phase and decrease the maximum growth rate of S. Typhimurium (p < 0.05). Glucose-lysine MRP (GL MRP) was determined to have the highest relative melanoidin (1.690 ± 0.048 at Ab420) and its efficacy against S. Typhimurium populations was measured at 37 °C and at pH 7.0 and estimated on xylose lysine deoxycholate (XLD) agar. GL MRP significantly reduced S. Typhimurium populations by >1 log CFU/mL at 8 and 24 h after inoculation (p < 0.05). GL MRPs also further decreased S. Typhimurium populations significantly under thermal stress condition (55 °C) compared to optimal (37 °C) by ~1 log CFU/mL (p < 0.05). Overall, GL MRP demonstrated effective antimicrobial activity against S. Typhimurium at 37 °C and 55 °C.

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Posted in Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Risk, Salmonella, Salmonella in Chicken

Research – Hurdle Technology Approach to Control Listeria monocytogenes Using Rhamnolipid Biosurfactant

Posted on February 4, 2023 by | Leave a comment

MDPI

Abstract

This study evaluates the combination of mild heat with a natural surfactant for the inactivation of L. monocytogenes Scott A in low-water-activity (aw) model systems. Glycerol or NaCl was used to reduce the aw to 0.92, and different concentrations of rhamnolipid (RL) biosurfactant were added before heat treatment (60 °C, 5 min). Using glycerol, RL treatment (50–250 µg/mL) reduced bacterial population by less than 0.2 log and heat treatment up to 1.5 log, while the combination of both hurdles reached around 5.0 log reduction. In the NaCl medium, RL treatment displayed higher inactivation than in the glycerol medium at the same aw level and a larger synergistic lethal effect when combined with heat, achieving ≥ 6.0 log reduction at 10–250 µg/mL RL concentrations. The growth inhibition activity of RL was enhanced by the presence of the monovalent salts NaCl and KCl, reducing MIC values from >2500 µg/mL (without salt) to 39 µg/mL (with 7.5% salt). The enhanced antimicrobial activity of RL promoted by the presence of salts was shown to be pH-dependent and more effective under neutral conditions. Overall, results demonstrate that RL can be exploited to design novel strategies based on hurdle approaches aiming to control L. monocytogenes.

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Posted in Decontamination Microbial, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Listeria, Listeria monocytogenes, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk

Research – Listeria monocytogenes, Escherichia coli and Coagulase Positive Staphylococci in Cured Raw Milk Cheese from Alentejo Region, Portugal

Posted on February 4, 2023 by | Leave a comment

MDPI

Listeria monocytogenes, Escherichia coli and Coagulase Positive Staphylococci in Cured Raw Milk Cheese from Alentejo Region, Portugal

Abstract

Traditional cheeses are part of the Portuguese gastronomic identity, and raw milk of autochthonous species is a common primary ingredient. Here, we investigated the presence of Listeria monocytogenes, Coagulase Positive Staphylococci (CPS) and pathogenic Escherichia coli, as well as of indicator microorganisms (E. coli and other Listeria spp.) in 96 cured raw milk cheeses from the Alentejo region. Whole genome sequencing (WGS) of pathogenic E. coli and Listeria spp. as well as antimicrobial resistance (AMR) screening of E. coli isolates was also performed. L. monocytogenes, CPS > 104 cfu/g and Extra intestinal E. coli were detected in 15.6%, 16.9% and 10.1% of the samples, respectively. Moreover, L. monocytogenes > 102 cfu/g and Staphylococcal enterotoxins were detected in 4.2% and 2.2% of the samples, respectively. AMR was observed in 27.3% of the E. coli isolates, six of which were multidrug resistant. WGS analysis unveiled clusters of high closely related isolates for both L. monocytogenes and L. innocua (often correlating with the cheese producer). This study can indicate poor hygiene practices during milk collection/preservation or during cheese-making procedures and handling, and highlights the need of more effective prevention and control measures and of multi-sectoral WGS data integration, in order to prevent and detect foodborne bacterial outbreaks.

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Posted in E.coli, food bourne outbreak, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, foodborne outbreak, foodbourne outbreak, Listeria monocytogenes, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, outbreak, Staphylococcus aureus

Research – The Effect of High-Pressure Processing on the Survival of Non-O157 Shiga Toxin-Producing Escherichia coli in Steak Tartare: The Good- or Best-Case Scenario?

Posted on February 4, 2023 by | Leave a comment

MDPI

Abstract

Samples of steak tartare were artificially contaminated with a cocktail of Shiga toxin-producing Escherichia coli (STEC) O91, O146, O153, and O156 to the level of 3 log and 6 log CFU/g. Immediately after vacuum packing, high-pressure processing (HPP) was performed at 400 or 600 MPa/5 min. Some of the samples not treated with HPP were cooked under conditions of 55 °C for 1, 3, or 6 h. HPP of 400 MPa/5 min resulted in a 1–2 log reduction in the STEC count. In contrast, HPP of 600 MPa/5 min led to the elimination of STEC even when inoculated to 6 log CFU/g. Nevertheless, sub-lethally damaged cells were resuscitated after enrichment, and STEC was observed in all samples regardless of the pressure used. STEC was not detected in the samples cooked in a 55 °C water bath for 6 h, even after enrichment. Unfortunately, the temperature of 55 °C negatively affected the texture of the steak tartare. Further experiments are necessary to find an optimal treatment for steak tartare to assure its food safety while preserving the character and quality of this attractive product.

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Posted in Decontamination Microbial, E.coli O157, E.coli O157:H7, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Testing, HPP, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, O146, O153, O156, STEC, STEC E.coli

Research – 10 surprising facts about the ‘mind-control’ parasite Toxoplasma gondii

Posted on February 3, 2023 by | Leave a comment

Live Science

Toxoplasma gondii is a single-celled protozoan parasite that invades the cells of a variety of host organisms, including humans, and causes a disease known as toxoplasmosis. T. gondii is sometimes nicknamed the “mind-control parasite” because toxoplasmosis can cause a range of neurological and behavioural changes in infected animals, although most human infections have no clear symptoms.

The pathogen is one of the most common infectious parasites in the world and could lay dormant in up to half of the world’s population, as well as almost any warm-blooded animal species. But there is still much we don’t know about this extremely weird parasite.

From its unusual affinity for cats to its ties to schizophrenia, at the link above are 10 surprising facts about T. gondii.

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Posted in Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Toxoplasma gondii, Toxoplasmosis

Research- Repeated cross-sectional study identifies differing risk factors associated with microbial contamination in common food products in the United Kingdom

Posted on February 3, 2023 by | Leave a comment

Science Direct

Highlights

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E. coli was found in 29–99% of the five food types studied.

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Salmonella was higher in imported frozen chicken than domestic chilled chicken.

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E. coli and Klebsiella detection were higher in summer and autumn for leafy greens.

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Klebsiella detection was higher in summer for chicken and pork.

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Vibrio contamination was common in raw prawns at 60.4%.

Abstract

All foods carry microbes, many of which are harmless, but foods can also carry pathogens and/or microbial indicators of contamination. Limited information exists on the co-occurrence of microbes of food safety concern and the factors associated with their presence. Here, a population-based repeated cross-sectional design was used to determine the prevalence and co-occurrence of Escherichia coli, Klebsiella spp., Salmonella spp. and Vibrio spp. in key food commodities – chicken, pork, prawns, salmon and leafy greens. Prevalence in 1,369 food samples for these four target bacterial genera/species varied, while 25.6% of all samples had at least two of the target bacteria and eight different combinations of bacteria were observed as co-occurrence profiles in raw prawns. Imported frozen chicken was 6.4 times more likely to contain Salmonella than domestic chicken, and imported salmon was 5.5 times more likely to be contaminated with E. coli. Seasonality was significantly associated with E. coli and Klebsiella spp. contamination in leafy greens, with higher detection in summer and autumn. Moreover, the odds of Klebsiella spp. contamination were higher in summer in chicken and pork samples. These results provide insight on the bacterial species present on foods at retail, and identify factors associated with the presence of individual bacteria, which are highly relevant for food safety risk assessments and the design of surveillance programmes.

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Posted in E.coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Klebsiella, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Salmonella, Salmonella in Chicken, Vibrio

Research – Inactivation of Escherichia coli in an Orange Juice Beverage by Combined Ultrasonic and Microwave Treatment

Posted on February 3, 2023 by | Leave a comment

MDPI

Abstract

The inactivation of Escherichia coli is one of the major issues in the food industry. The present study focuses on the application of a combined microwave-ultrasound system for the optimization of the inactivation of Escherichia coli ATCC 25922 in an orange juice drink. Using response surface methodology (RSM), trials were planned with a Box–Behnken Design (BBD) to maximize the impact of microwave power (A: 300–900 W), microwave treatment time (B: 15–35 s), and time of ultrasound (C: 10–30 min) on E. coli inactivation. Analysis of variance (ANOVA) was carried out and E. coli inactivation was expressed with a mathematical equation depending on the factors. The results showed that both the microwave treatment time and the time of ultrasound were effective as independent variables in eliminating the E. coli strain. However, the effect of these two variables, ultrasound and microwave exposure time, in combination was significantly greater than when examined separately. RSM modeling determined that optimal treatment conditions include 900 W microwave power, 33 s microwave treatment time, and 20 min time of ultrasound to achieve an 8-log reduction of E. coli, constituting total inactivation. The results of this study showed that ultrasound-microwave treatment is a potential alternative processing method for an orange juice beverage.

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Posted in E.coli, escherichia coli, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk

Finland joins countries with travel-related Shigella cases

Posted on February 3, 2023 by | Leave a comment

Food Safety News

Shigella - kswfoodworld

Image CDC

Finland is the latest country to report Shigella infections in people returning from Cape Verde.

The Finnish Institute of Health and Welfare (THL) recorded eight patients with shigellosis in November and December 2022, with a history of travel to Cape Verde.

Based on typing, the strains in five of these cases match those found in other European countries. Almost all Shigella infections found in Finland originate from abroad.

During 2022, more travel-related shigellosis cases than usual were recorded in several European countries. Patients are linked by trips to Cape Verde.

Related cases have been reported by the United Kingdom, the Netherlands, France, Germany, Denmark, and Portugal.

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Posted in Decontamination Microbial, food bourne outbreak, Food Illness, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Foodborne Illness, foodborne outbreak, foodbourne outbreak, Illness, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, outbreak, Shigatoxin, Shigella, Shigella flexneri, Shigella Sonnei

India – Maha: 137 Warkaris take ill due to suspected food poisoning in Pandharpur

Posted on February 3, 2023 by | Leave a comment

The Print

Pune, Feb 2 (PTI) A total of 137 Warkaris (devotees of Lord Vitthal) fell sick due to suspected food poisoning in the temple town of Pandharpur in Maharashtra, officials said on Thursday. All the devotees are stable, they said.

According to health officials from Solapur district, several worshippers on Wednesday consumed ‘varai rice’, a barnyard millet preparation, at a local monastery on the occasion of Maghi Ekadashi.

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Posted in Food Illness, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Food Poisoning, Foodborne Illness, Illness, microbial contamination, Microbial growth, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, Poisoning