Microbiological Contamination Research Articles

Investigation of the influence of the processing method before drying on the organoleptic characteristics, the amount of weight loss and microbiological parameters of zucchini chips

Drying is one of the most popular ways to preserve plant materials by reducing humidity and preventing microbiological contamination and it is a promising direction in the food industry. The article presents the results of the research in the development of effective technologies for preparing zucchini for drying, ensuring acceleration of the drying process, as well as maintaining or improving organoleptic characteristics (for example, to prevent excessive darkening). The article describes the results of the influence of pre-treatment of zucchini before drying on quality indicators – organoleptic indicators (appearance, consistency, taste, smell, color, shape, size) and physicochemical indicators (weight of fresh raw materials and dried product, moisture content of the finished product) and microbiological safety (MAFAnM, coliform bacteria, mold, yeast). The types of pre-treatment of zucchini before drying were microwave treatment, C6 H8 O7 solution (citric acid), NaCl solution (saline solution), microwave treatment + C6 H8 O7 solution, microwave treatment + NaCl solution. During the organoleptic assessment, it was found that the best organoleptic indicators are provided by treatment with 5% NaCl solution (4.8 points) and 1% C6 H8 O7 solution (4.7 points). Microwave pre-treatment in various parameters led to the appearance of characteristic bitterness and an unpleasant aftertaste. Treatment with a solution of citric acid in various dosages imparts a sour taste and prevented darkening during drying. It was found that various types of pre-treatment do not affect the duration of drying of zucchini, which was, on average, 7 hours. Microwave treatment reduced humidity to 3.4%, citric acid – to 3.6%, saline solution – to 4.6%, while complex treatment did not affect the reduction in moisture content of the dry product and, in general, the duration of drying. As a result of the microbiological assessment, it was noted that the amount of MaFAnM and mold fungi were within acceptable imits, and the growth of coliform bacteria was absent, which corresponded to the indicators of regulatory documents.

Identification and Characterization of Microorganisms Isolated from Non-compliant and/or Atypical Dairy Products in Canada

Despite good manufacturing practices and rigorous cleaning and sanitizing procedures established in dairy processing plants, microbiological contamination remains the main cause of products being non-compliant and/or atypical and hence not fit for human consumption. The objective of this study was to isolate, identify and characterize bacteria, yeasts and molds associated with substandard dairy products in Canada and to create a collection of reference isolates. In addition to conventional microbiological characterization, each isolate was tested for biofilm-forming ability and susceptibility to heat, antimicrobial agents, and common industrial disinfectants. Among the 105 microbial strains isolated from pasteurized milk, cream, and cheese samples, 24 bacterial isolates, belonging mainly to the genus Pseudomonas, were shown to be moderate or strong biofilm producers in 96-well plates and highly resistant to peracetic acid (100 ppm, 5 min contact time) and sodium hypochlorite (70 ppm, 5 min contact time). In addition, 56 bacterial isolates, including Acinetobacter baumannii, Enterobacter bugandensis, Klebsiella pneumoniae and Pseudomonas spp., were found resistant to ampicillin, fosfomycin and/or ceftriaxone, while 14 others, such as Bacillus spp. and Macrococcus spp., withstood a heat treatment equivalent to low-temperature long-time pasteurization (63°C for 30 min). This descriptive study provides new information on potential problematic microorganisms in dairies and will guide the development of novel control strategies intended to prevent and reduce microbiological contamination and the associated economic losses.

Exploring the Antimicrobial Efficacy of Low-Cost Commercial Disinfectants Utilized in the Agro-Food Industry Wash Tanks: Towards Enhanced Hygiene Practices.

The increase in vegetable consumption has underlined the importance of minimizing the risks associated with microbiological contamination of fresh produce. The critical stage of the vegetable washing process has proven to be a key point for cross-contamination and the persistence of pathogens. In this context, the agri-food industry has widely adopted the use of disinfectants to reduce the bacterial load in the wash water. Therefore, we conducted laboratory-scale experiments in order to demonstrate the antimicrobial activity of disinfectants used in the wash tank of agro-food industries. Different wash water matrices of shredded lettuce, shredded cabbage, diced onion, and baby spinach were treated with sodium hypochlorite (NaClO), chlorine dioxide (ClO2), and per-oxyacetic acid (PAA) at recommended concentrations. To simulate the presence of pathogenic bacteria, a cocktail of E. coli O157:H7 was inoculated into the process water samples (PWW) to determine whether concentrations of disinfectants inhibit the pathogen or bring it to a viable non-culturable state (VBNC). Hereby, we used quantitative qPCR combined with different photo-reactive dyes such as ethidium monoazide (EMA) and propidium monoazide (PMA). The results indicated that concentrations superior to 20 ppm NaClO inhibit the pathogen E. coli O157:H7 artificially inoculated in the process water. Concentrations between 10-20 ppm ClO2 fail to induce the pathogen to the VBNC state. At concentrations of 80 ppm PAA, levels of culturable bacteria and VBNC of E. coli O157:H7 were detected in all PWWs regardless of the matrix. Subsequently, this indicates that the recommended concentrations of ClO2 and PAA for use in the fresh produce industry wash tank do not inhibit the levels of E. coli O157:H7 present in the wash water.

Stabilization of the pharmaceutical finished dosages form by using various techniques

The stabilization of pharmaceuticals means that the drug product is physically, chemically and microbiologically stable at the recommended storage condition throughout the predefined shelf life of the product. Pharmaceutical formulations irrespective of its physical states have been used for their efficacy and safety so for as its therapeutic activity is concern. Stability of dosage forms is the ability of drugs to remains unaffected by environmental condition viz. temperature, humidity and microbiological contamination. This research work is an attempt to stabilize the drug product at controlled room temperature for the drug product which is stable at refrigerated storage condition. Hence the aim of present study was development and stabilization of the drug product at room temperature. Investigation of alternate manufacturing processes for stabilization of the drug product at controlled room temperature was one of the objectives of the work. Keywords: Stability, shelf life, lyophilization, freeze drying

The chemical and microbiological safety of emerging alternative protein sources and derived analogues: A review.

Climate change and changing consumer demand are the main factors driving the protein transition. This shift toward more sustainable protein sources as alternatives to animal proteins is also reflected in the rapid upscaling of meat and dairy food analogues. Such changes could challenge food safety, as new food sources could result in new and unexpected food safety risks for consumers. This review analyzed the current knowledge on chemical and microbiological contamination of emerging alternative protein sources of plant origin, including soil-based (faba bean, mung bean, lentils, black gram, cowpea, quinoa, hemp, and leaf proteins) and aquatic-based (microalgae and duckweeds) proteins. Moreover, findings on commercial analogues from known alternative protein sources were included. Overall, the main focus of the investigations is on the European context. The review aimed to enable foresight approaches to food safety concerning the protein transition. The results indicated the occurrence of multiple chemical and microbiological hazards either in the raw materials that are the protein sources and eventually in the analogues. Moreover, current European legislation on maximum limits does not address most of the "contaminant-food" pairs identified, and no legislative framework has been developed for analogues. Results of this study provide stakeholders with a more comprehensive understanding of the chemical and microbiological safety of alternative protein sources and derived analogues to enable a holistic and safe approach to the protein transition.

Diazoxon exposure increases susceptibility to infection by Salmonella Typhimurium

ABSTRACT Various exogenous factors, such as microbiological and chemical contamination condition food security. Salmonella Typhimurium (S. Typhimurium) is the cause of salmonellosis. This bacterium utilizes phagocytosis to create bacterial reservoirs. On the other hand, exposure to chemical contaminants, such as pesticides, increases susceptibility to numerous infections. Therefore, this research aims to evaluate the effect of co-exposure to diazoxon and S. Typhimurium on the in vitro infection dynamics. For this purpose, human mononuclear cells were pre-exposed in vitro to diazoxon and then challenged with S. Typhimurium at 1, 8, and 24 h. Bacterial internalization, actin polymerization, and reactive oxygen species (ROS) were analyzed. Obtained data show that mononuclear cells previously exposed to diazoxon exhibit greater internalization of S. Typhimurium. Likewise, greater ROS production and an increase in actin polymerization were observed. Therefore, in the proposed scenario, obtained data suggest that co-exposure to diazoxon and S. Typhimurium increases susceptibility to acquiring an illness.

Consumption Rate of Energy Drinks among Kabul University Students: Caffeine Contents and Microbiological Examinations of their Available Varieties at Kabul City

Energy drinks (EDs) have gained popularity as a beverage all around the world, but as their usage has grown, questions have been raised concerning their high caffeine concentration and potential for microbial contamination. The objective of this study was to evaluate EDs. consumption rate among Kabul University students, the determination of caffeine contents, microbiological quality, and pH of EDs available in Kabul City. 184 Kabul University students were selected using simple random selection to assess the types, amounts of consumption, and awareness about the side effects of EDs. The caffeine levels in EDs were quantified using a UV/Vis spectrophotometer. The EDs were cultured in various culture media for microbiological studies. 23 of the 184 students were regular users of EDs. The mean concentration of caffeine was 277.43 ppm with an SD of 137.49 to 143.10. The EDs had no microbiological contamination, and their pH ranged from 2.64 to 3.64. 12.5% of the students regularly used EDs, Caffeine levels in all of the evaluated EDs were below recommended levels, and none of them contained any bacteria contamination.

THE EFFECT OF ULTRASONIC DIFFUSER ON INDOOR AIR QUALITY

The usage of ultrasonic diffusers in indoors has raised concerns regarding their potential health effects, mostly due to the lack of research on the matter. This study’s aim was to analyse the effect of distilled water, tap water, and tap water with essential oils droplets from an ultrasonic diffuser on the number of particle matter and microbiological contamination in indoor air under laboratory conditions during summer and winter seasons. The most common species throughout all experiments were the Gram+ Aerococcus viridans and Micrococcus luteus, accounting for 21.33% (93 CFU/m3) and 13.76% (60 CFU/m 3) of the total bacteria count. Four different fungal species were identified over both seasons, moulds were more common making up 81.25% (65 CFU/m 3). It was noted that the microorganisms identified were not pathogenic, presenting no significant infection risk from the diffuser's use. Experiments involving the use of an ultrasonic diffuser with DW demonstrated that PM1, PM2.5, and PM10 levels can be maintained within acceptable ranges over a 4-hour period. However, these experiments also highlighted an increase in nanoparticle concentrations, for which current guidelines lack specific recommendations. The diffuser was cleaned before every experimental setup stage, avoiding any residual contamination.

Runoff microbiome quality assessment of a city center rainwater harvesting zone shows a differentiation of pathogen loads according to human mobility patterns

The hygienic quality of urban surfaces can be impaired by multiple sources of microbiological contaminants. These surfaces can trigger the development of multiple bacterial taxa and favor their spread during rain events through the circulation of runoff waters. These runoff waters are commonly directed toward sewer networks, stormwater infiltration systems or detention tanks prior a release into natural water ways. With water scarcity becoming a major worldwide issue, these runoffs are representing an alternative supply for some usage like street cleaning and plant watering. Microbiological hazards associated with these urban runoffs, and surveillance guidelines must be defined to favor these uses. Runoff microbiological quality from a recently implemented city center rainwater harvesting zone was evaluated through classical fecal indicator bacteria (FIB) assays, quantitative PCR and DNA meta-barcoding analyses. The incidence of socio-urbanistic patterns on the organization of these urban microbiomes were investigated. FIB and DNA from Human-specific Bacteroidales and pathogens such as Staphylococcus aureus were detected from most runoffs and showed broad distribution patterns. 16S rRNA DNA meta-barcoding profilings further identified core recurrent taxa of health concerns like Acinetobacter, Mycobacterium, Aeromonas and Pseudomonas, and divided these communities according to two main groups of socio-urbanistic patterns. One of these was highly impacted by heavy traffic, and showed recurrent correlation networks involving bacterial hydrocarbon degraders harboring significant virulence properties. The tpm-based meta-barcoding approach identified some of these taxa at the species level for more than 30 genera. Among these, recurrent pathogens were recorded such as P. aeruginosa, P. paraeruginosa, and Aeromonas caviae. P. aeruginosa and A. caviae tpm reads were found evenly distributed over the study site but those of P. paraeruginosa were higher among sub-catchments impacted by heavy traffic. Health risks associated with these runoff P. paraeruginosa emerging pathogens were high and associated with strong cytotoxicity on A549 lung cells. Recurrent detections of pathogens in runoff waters highlight the need of a microbiological surveillance prior allowing their use. Good microbiological quality can be obtained for certain typologies of sub-catchments with good hygienic practices but not all. A reorganization of Human mobility and behaviors would likely trigger changes in these bacterial diversity patterns and reduce the occurrences of the most hazardous groups.

Enhancing Surgical Safety: Microbiological Air Control in Operating Theatres at University Medical Centre Maribor.

the aim of the study was to assess microbiological air quality in operating theatres by determining the level of microbiological contamination of the air and critical surfaces using the passive air sampling method and compliance of the operating theatre staff with infection control measures. The prospective study was conducted in the surgical block of the University Medical Centre Maribor. For two months continuously, ten operating theatres were assessed for microbial contamination of air and surfaces during quiet and active times of the day. A passive air sampling method with Petri dishes on an agar specially adapted for this purpose (plate count agar) was used. In addition, ten surgical procedures were observed to assess staff compliance with recommended practises. Air samples met microbiological standards in all operating theatres. In both sampling sessions of the day (quiet and active periods), microbial contamination of the air was always within the limit of 10 CFU/m3. The average number of bacterial colonies was zero to two during quiet phases and one to four during active phases. Approximately 60% of the isolates from the operating theatres belonged mainly to the genus Staphylococcus: S. epidermidis (36% of the isolates), S. hominis (17.5%) and S. haemolyticus (5.5%). The rest were identified as Streptococcus anginosus (23%) and Bacillus sp. (18%). Pathogenic bacteria and moulds were not present. In regard to staff compliance with good surgical practise, the former varied by behaviour and function, with non-compliance in pre-operative skin preparation and operating theatre congestion being notable. The cleanliness of the environment was satisfactory. Microbiological air control is extremely important for the safety and success of both surgical and postoperative practises. In spite of good results obtained in the study, further improvements in surgical staff compliance with good surgical practise are essential to reduce surgical site infections.

Assessing exposure to airborne fungi and bacteria in the horse-riders environment: A pilot study

Among airborne biological contaminants, several pathogenic and/or allergenic fungi and bacteria can affect the health of horses and humans. Exposure to primary biological aerosol particles (PBAP) in the equine environment remains poorly understood, although environmental factors play a major role in the development of respiratory diseases and impaired performance in horses. This pilot study was conducted during a training course for young racers. Ambient and personal air samples provided original data on the microbial composition of PBAP in the riders’ immediate environment (stable, outdoor, riding arena), using culture-based and metagenomic approaches. The culture-based approach showed average levels of fungi and bacteria of 2.3 × 104 and 8.3 × 105 CFU/m3 respectively during training. Seventy-one and 50 fungal and bacterial species were respectively identified, while the metagenomic approach identified 211 and 285, respectively. It should be noted, however, that two-thirds of the bacterial and fungal genera were found by both approaches. Among these species, various pathogenic and/or allergenic fungi (Alternaria spp., Aspergillus spp., Cladosporium spp. and Lichtheimia ramosa) and bacteria (Aeromonas spp., Bacillus spp., Pseudomonas spp. and Staphylococcus spp.) were highlighted. This study underlines the value of the combined use of culture-based and metagenomic approaches to provide an overview of the distribution of different fungal and bacterial phyla, genera and species in the equine environment. Statistical analysis also suggests interactions between microbiological contaminants (bacteria and mold) and climatic parameters (rain, wind, temperature).

Fluorescence spectroscopy for tracking microbiological contamination in urban waterbodies

Dissolved organic matter (DOM) plays a crucial role in freshwater ecosystem function. Monitoring of DOM in aquatic environments can be achieved by using fluorescence spectroscopy. Particularly, DOM fluorescence can constitute a signature of microbiological contamination with a potential for high frequency monitoring. However, limited data are available regarding urban waterbodies. This study considers fluorescence data from field campaigns conducted in the Paris metropolitan region: two watercourses (La Villette basin and the river Marne), two stormwater network outlets (SO), and a wastewater treatment plant effluent (WWTP-O). The objectives of the study were to characterize the major fluorescence components in the studied sites, to investigate the impact of local rainfall in such components and to identify a potential fluorescence signature of local microbiological contamination. The components of a PARAFAC model (C1-C7), corresponding to a couple of excitation (ex) and emission (em) wavelengths, and the fluorescence indices HIX and BIX were used for DOM characterization. In parallel, fecal indicator bacteria (FIB) were measured in selected samples. The PARAFAC protein-like components, C6 (ex/em of 280/352 nm) and C7 (ex/em of 305/340 nm), were identified as markers of microbial contamination in the studied sites. In the La Villette basin, where samplings covered a period of more than 2 years, which also included similar numbers of wet and dry weather samples, the protein-like components were significantly higher in wet weather in comparison to dry weather. A positive relationship was obtained between C6 and FIB. In urban rivers, the high frequency monitoring of C6 levels would support the fecal contamination detection in rivers. In addition, it could help targeting specific field campaigns to collect comprehensive dataset of microbiological contamination episodes.

A complete review on enhancing air circulation and filtration for improving internal air quality in a healthy school environment

The health of staff and students is impacted by Indoor Air Quality (IAQ) in educational environments. A healthy atmosphere depends on good IAQ, yet millions of students worldwide might develop respiratory illnesses due to poor air quality. Immediate action is required to alleviate the burden of IAQ consequences in the pandemic-dominated period. This detailed evaluation focuses on techniques for improving air circulation and filtration systems to meet the critical demand for improved IAQ in schools. This research demonstrates the negative impacts of inadequate IAQ on students and educators’ cognitive capacities, health and performance based on an extensive examination of current records. A healthy learning environment, on the other hand, can minimize absenteeism, raise test results and increase pupil/teacher education/teaching productivity. This review explores the effectiveness of different ventilation as well as filtration methods, such as air purifiers, mechanical ventilation, natural ventilation and advanced filtration systems, in lowering airborne pollutants like particulate matter, volatile organic compounds (VOCs) and microbiological contaminants. This study reviews current information, emphasizes recent findings along with options and provides guidelines for the future of education. It underlines the limits of previous studies, gives ideas for further research and indicates a path forward for more enhancements to the air quality in schools. Comprehensive analysis with greater sample numbers is required to evaluate student performance, indoor contentment and environmental health exposure. On-site measurements are essential for comprehending the properties of contaminants. Intricate mitigation strategies must take health impacts, IAQ and energy efficiency into effect.

Analysis of an anatomy laboratory for microbiological contamination

Aim: In order to prevent any microbiological contamination in laboratories, it is vital to determine both routine microbiological screening and the appropriate protocol. This study was based on this hypothesis and discussed the microbiological contamination and prevention procedures in an anatomy laboratory. Methods: The study was carried out on 34 different spots in an anatomy laboratory. Swab samples taken from these points were examined for contamination and contamination was detected. The samples were taken from various locations, including the head, upper and lower extremities of both male and female cadavers, the door handle, the floor in front of the door, the faucet, the head, body, and foot parts of the dissection table, the dissection tool, the trailer, the inner and outer coating of the cadaver pool, the sink, the floor in front of the window, the stool, the living room wall, the formaldehyde liquid in the cadaver pool, the window handle, the instrument table, the morgue unit, the exterior surfaces of three different organ storage boxes, the inner surface of an organ storage box, the medical waste container, the handle of the organ storage cabinet, a training model, the lower surface of the dissection table, the medical waste storage box for dissection, and the blackboard. Results: Bacillus subtilis was found in 16 out of 34 different spots and mold fungus was found in 2 of them. No contamination was detected in the remaining 16 spots. 69% of the spots were directly related to the cadaver. Conclusion: As a result of our study, the importance of scanning anatomy laboratories in terms of microbiological contamination was highlighted and an appropriate protocol was determined.

Comparison of real-time PCR and nested PCR based on the HlyA gene for the detection of Listeria monocytogenes. Application on cheese samples.

The aim of the present study was to compare the performance of a nested polymerase chain reaction (nPCR) and a real-time PCR based on the amplification of the HlyA gene from Listeria monocytogenes using a plasmid DNA standard. Nested PCR was developed with an internal amplification control (IAC). Both techniques were validated in soft cheese samples by comparing their results with the results of the microbiological reference method ISO 11290-1:2017. Cheese samples artificially contaminated with 3.5 to 3,500 UFC/25g were processed by ISO 11290-1:2017 and, at several times of culture, DNA samples were extracted. All cheeses contaminated with L. monocytogenes were positive for the microbiological method 96h post contamination and for nPCR and real-time PCR 48h post contamination. At this time, the HlyA gene was amplified in all contaminated samples. Both molecular techniques showed the same sensitivity, 30 copies/reaction or 3.5 UFC/25g, when plasmid DNA standard or artificially contaminated cheese samples were used. Finally, eighty soft cheese samples obtained from local retail stores and tested by three methods were negative, indicating a 100% concordance in results. The development of an nPCR with IAC reinforces the reliability of the negative results without increasing the costs of the reaction. Besides, nPCR showed less sensitivity to the presence of inhibitory substances in the reaction. The use of one of these molecular techniques could be easily coupled to the microbiological method, serving as a screening method in the food industry for hygiene monitoring and early identification of contaminated foods.

Evaluation of the Microbiological Quality of Three Varieties of Kilichi Produced in Niger

Kilichi is a food based on beef, mutton or goat meat that is processed by slicing, dressing, drying in the sun and applying spice porridge and roasting over a hot fire. Traditional processing conditions and practices for this product may pose risks of microbiological contamination and pose serious public health concerns.
 The objective of this study was to assess the microbiological quality of Niger's kilichis. A total of twenty-two samples of kilichi of three variants (single kilichi "KS", archide kilichi "Kilichi Fari" and peanut paste kilichi with Jawa "Kilichi Ja"). Total Mesophilic Aerobic Flora (TMAF), total coliforms, faecal coliforms, Escherichia coli and Salmonella were determined after the preparation of the stock solutions, decimal dilution and seeding on selective media. The results showed that the samples of the kilichi coated with the peanut paste sauce are more loaded with sought-after sprouts. However, single kilichi is more loaded with faecal coliform, 3,52x106 CFU/ml; 2,11x105 CFU/ml and 1,17x106 CFU/ml for kilichi single, kilichi Fari and kilichi Ja respectively. These results show that the microbial load of kilichi samples is higher than the microbial criteria that cooked deli products must meet.

Safety, Processing, and Utilization of Fishery Products

Global marine fish harvests have reached a plateau over the last decade, and efforts to increase aquaculture tend to face limitations in terms of water resources and contamination problems. Of the current fish harvest, at least 50% is discarded as waste. The current situation requires efforts to process, preserve, and utilize the fish capture to minimize waste. Chemical and microbiological contamination limit the utilization of harvested fish. There is a need to improve fish preservation to minimize spoilage and to process them into more appealing products. Instead of resorting to individual food-processing methods, the efficiency of processing could best be increased by a combination of conventional and modern processing methods or by combinations of modern processing methods. Fish waste is a rich source of oils containing essential fatty acids, polypeptides, and amino polysaccharides that could be utilized through the upscaling of current scientifically proven methods to new processing technologies. The separation of collagens, gelatins, bioactive peptides, edible fish oils, and chitosan form the primary stages in the utilization of fish waste. The products need purification to meet food quality and safety standards and to have desirable industrial characteristics. The diversity of information and products generated through new methods require advanced data handling and prediction systems, such as artificial intelligence, to address food safety and to derive the best out of fish processing and utilization.

Alert for microbreweries – a case study on unpasteurized and unfiltered beer

Beer stability, influenced by physical, chemical, and biological factors, poses a considerable challenge for breweries. Biological stability, as a major concern, is effectively managed through practices such as good hygiene, pasteurization, and filtration. Microbiological contamination, often recognizable by increased turbidity or off-flavours, is influenced by temperature, with optimal conditions promoting the growth of specific microorganisms. Lower temperatures slow down flavour changes and chemical reactions in beer, impacting its non-biological stability. This case study explores the impact of storage temperature on autolysis off-flavour development in 10 different unfiltered and unpasteurized beers. The results showed that autolysis off-flavour occurred at both low and higher storage temperatures and that its dependence on the temperature was minimal. This unexpected fact was discovered mainly due to uncovered significant contamination of the commercial beers tested (wild yeasts, lactic acid bacteria, enterococci and coliform bacteria). For this reason, the concentration of cells in the beer appeared as a more influential factor in the development of off-flavours, including autolysis, than the storage temperature. The partial results need to be studied in more detail, nevertheless, we felt it was important to publish the revelation of a strong contamination of beers purchased from regular stores for our experiments. At this point it can already be concluded that the low storage temperature did not help to prevent the development of the contamination and the associated sensory deterioration of the beers.

Raw milk cheeses from Beira Baixa, Portugal—A contributive study for the microbiological hygiene and safety assessment

Due to specific bacterial microbiota, raw milk cheeses have appreciated sensory properties. However, they may pose a threat to consumer safety due to potential pathogens presence. This study evaluated the microbiological contamination of 98 raw milk cheeses from Beira Baixa, Portugal. Presence and enumeration of Coagulase Positive Staphylococci (CPS), Listeria monocytogenes, Salmonella spp., pathogenic Escherichia coli, and indicator microorganisms (non-pathogenic E. coli and Listeria spp.) was attained. E. coli antimicrobial resistance (AMR) was also evaluated. PCR and/or Whole genome sequencing (WGS) was used to characterize E. coli, Salmonella spp. and L. monocytogenes isolates. Sixteen cheeses (16.3%) were classified as Satisfactory, 59 (60.2%) as Borderline and 23 (23.5%) as Unsatisfactory/Potential Injurious to Health. L. monocytogenes, CPS > 104 cfu g−1, Extraintestinal pathogenic E. coli (ExPEC) and Salmonella spp. were detected in 4.1%, 6.1%, 3.1% and 1.0% of the samples, respectively. Listeria innocua (4.1%) and E. coli > 104 cfu g−1 (16.3%) were also detected. AMR E. coli was detected in 23/98 (23.5%) of the cheese samples, of which two were multidrug resistant. WGS identified genotypes already associated to human disease and Listeria spp. cluster analysis indicated that cheese contamination might be related with noncompliance with Good Hygiene Practices during cheese production.

Microbiology of post-fermentation leachate

Using post-fermentation leachate as fertilizer is a good alternative and solution to the problem of waste at wastewater treatment plants and contains the principles of sustainable development. Leachate from anaerobic treatment of sewage sludge contains valuable elements such as phosphorus, nitrogen and potassium, which can improve soil properties. The production of liquid fertilizer minimizes the negative impact of leachate on the main biological stream in the WWTP and improves the energy efficiency of the entire wastewater treatment system. This transfers into the operating costs of the facility. When thinking about the agricultural use of digestion leachate and its introduction into the environment, a very important issue is its microbiological contamination. The purpose of the conducted research was to determine the microbiological quality of digestion leachates from municipal wastewater treatment plants and to determine the parameters of their hygienization. The number of bacteria in raw leachate is indicative of a sanitary risk in the case they are used in agriculture as fertiliser. Heating the leachate at 60°C for 15 minutes produces an effect comparable to that achieved by heating the leachate to 70°C. The sonication process itself did not affect the better temperature effect. Heating the leachate for 20 minutes after prior sonication for 20 minutes does not result in the complete elimination of microflora.