Category Archives: Microbiological Risk Assessment

Research – Antibacterial and Anti-Biofilm Properties of Diopside Powder Loaded with Lysostaphin

Posted on February 5, 2023 by | Leave a comment

MDPI

Abstract

Background: Diopside-based ceramic is a perspective biocompatible material with numerous potential applications in the field of bone prosthetics. Implantable devices and materials are often prone to colonization and biofilm formation by pathogens such as Staphylococcus aureus, which in the case of bone grafting leads to osteomyelitis, an infectious bone and bone marrow injury. To lower the risk of bacterial colonization, implanted materials can be impregnated with antimicrobials. In this work, we loaded the antibacterial enzyme lysostaphin on diopside powder and studied the antibacterial and antibiofilm properties of such material to probe the utility of this approach for diopside-based prosthetic materials. Methods: Diopside powder was synthesized by the solid-state method, lysostaphin was loaded on diopside by adsorption, the release of lysostaphin from diopside was monitored by ELISA, and antibacterial and anti-biofilm activity was assessed by standard microbiological procedures. Results and conclusions: Lysostaphin released from diopside powder showed high antibacterial activity against planktonic bacteria and effectively destroyed 24-h staphylococcal biofilms. Diopside-based materials possess a potential for the development of antibacterial bone grafting materials.

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Posted in Antibacterial, Biofilm, 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 Investigations, Microbiology Risk

Research – Microbiological, Physicochemical and Nutritional Properties of Fresh Cow Milk Treated with Industrial High-Pressure Processing (HPP) during Storage

Posted on February 5, 2023 by | Leave a comment

MDPI

Abstract

The safety, shelf life, and quality of fresh cow milk treated using industrial High-Pressure Processing (HPP) treatment at 600 MPa for 10 min was studied to identify the novelty of this non-thermal technology in milk processing. Changes in microbiological and physicochemical properties, including nutritional values of vitamins and amino acid profiles, were measured for a 60-day storage period at 6 °C +/− 1 °C. The HPP treatment produced milk that met all microbial safety requirements and exhibited a shelf life beyond 60 days in a hot and humid region. High physicochemical stability was achieved, with consistent pH and undetectable titratable acidity. The HPP treatment successfully retained all vitamins and minerals, including calcium (99.3%), phosphorus (99.4%), and magnesium (99.1%). However, the 60-day storage caused some degradation of Vitamin A (25%), B3 (91%), B5 (35%), B6 (80%), and C (85%), and minerals, including potassium (5%) and zinc (18%) when compared with fresh milk. This research has shown that the adoption of advanced treatment with HPP is very beneficial to the dairy industry in preserving milk quality in terms of its physicochemical and nutritional properties and extending its storage shelf life beyond 60 days.

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

Research – Far-UVC Radiation for Disinfecting Hands or Gloves?

Posted on February 5, 2023 by | Leave a comment

MDPI

Abstract

(1) Background: Far-UVC radiation in the spectral range 200–230 nm has, according to previous findings, a strong antimicrobial effect on pathogens, but exhibits hardly any harmful effect on human skin. Therefore, the present study will discuss whether such radiation could also be suitable for hand disinfection in the healthcare sector. (2) Methods: Hands and gloves were microbially contaminated and exposed to radiation from a 222 nm krypton-chloride-excimer lamp. The applied doses were 23 mJ/cm2 and 100 mJ/cm2, respectively. Irradiated and non-irradiated hands and gloves were pressed onto agar plates and colonies were counted and compared after 24 h of incubation. For comparison, we also treated hands and gloves with a commercial liquid alcohol-based disinfectant. (3) Results: On the hand, the 23 mJ/cm2 resulted in the reduction of the observed colonies on the agar plates by one log level. For the gloves irradiated with 100 mJ/cm2, a colony reduction of 1.3 log levels was recorded. In the comparative experiments with the commercial disinfectant, a colony reduction of 1.9 and approximately one log level was observed on hand and gloves, respectively. (4) Conclusion: In both cases, far-UVC radiation provided a considerable reduction in microorganisms. However, compared to published far-UVC irradiation results in suspensions, the disinfection success on hands and gloves was rather low. With regard to the irradiation limits currently existing in the European Union, multiple daily hand disinfection with far-UVC radiation is actually legally not possible at present, but the thresholds are currently under discussion and could change in the future. Far-UVC disinfection of hands in gloves seems theoretically possible if attention is paid to potential perforations in the gloves.

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Posted in Decontamination Microbial, food handler, Food Micro Blog, Food Microbiology, Food Microbiology Blog, Food Microbiology Research, Food Microbiology Testing, Hand Washing, microbial contamination, Microbiological Risk Assessment, Microbiology, Microbiology Investigations, Microbiology Risk, UV Microbiology, UV-C

Research – The Occurrence of Cryptosporidium spp. in Wild-Living Carnivores in Poland—A Question Concerning Its Host Specificity

Posted on February 5, 2023 by | Leave a comment

MDPI

Abstract

Cryptosporidium is an apicomplexan protozoan parasite that primarily infects the gastrointestinal epithelium in humans and domestic and wild animals. The majority of studies have been focused on human, livestock, and pet infections. Hence, Cryptosporidium spp. in wildlife, including wild carnivores, remained neglected. There are several studies reporting the occurrence of Cryptosporidium spp. in wild foxes, but these are only a few molecular surveys; no data is available concerning the occurrence of this parasite in raccoon dogs and martens in Europe, and to the best of our knowledge to date, only one study has reported Cryptosporidium from badgers in Spain. Therefore, we used molecular analyses to identify and genotype Cryptosporidium spp. in wild-living mesocarnivores in Poland. A total of 322 individual fecal samples from six carnivore species, i.e., raccoon, raccoon dog, red fox, European badger, pine, and beech martens were collected and then analyzed for the presence of Cryptosporidium spp. using the nested PCR method. The appearance of PCR products in the reaction with Cryptosporidium-specific primers against the 18S rRNA and actin genes demonstrated that Cryptosporidium spp. occurred in 23.0% of all examined species of animals. Performed sequence analyses showed the presence of the Cryptosporidium skunk genotype, Cryptosporidium vole genotype II, Cryptosporidium canis dog and fox genotypes, as well as Cryptosporidium erinacei, Cryptosporidium ditrichi, Cryptosporidium suis, and Cryptosporidium alticolis, in these hosts. Molecular data presented here indicate that examined mesocarnivores may be a significant reservoir of specific and non-specific Cryptosporidium species, including those with zoonotic potential. Most studies of carnivores have described the presence of non-specific Cryptosporidium spp. in carnivore hosts, and this is probably the result of the transfer of these parasites from prey species through the digestive tract or the transfer of the parasite from a contaminated environment.

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Posted in Contaminated water, Cryptosporidiosis, Cryptosporidium, 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, water microbiology, Water Safety

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