Determination Of Viable Counts Research Articles

Antibiofilm Effect of Sequential Application of Ozonated Water, Acetic Acid and Lactic Acid on Salmonella Typhimurium and Staphylococcus aureus Biofilms In Vitro

Biofilms are highly resistant to disinfectants and antimicrobials and are known as the primary source of food contamination. Salmonella Typhimurium (S. Typhimurium) and Staphylococcus aureus (S. aureus) have an excellent ability to form biofilm. This study aimed to evaluate the antibiofilm activity of ozonated water (O), acetic acid (AA), and lactic acid (LA), individually and sequentially, against biofilms of S. Typhimurium and S. aureus formed on the polystyrene surfaces. The antibiofilm effects of the treatments were evaluated using crystal violet staining and the viable count determination methods. In the staining method, the highest percentage of biofilm mass reduction was induced by successive use of ozonated water and acetic acid (O-AA), which reduced S. aureus biofilm mass by 44.36%. The sequential use of ozonated water and lactic acid (O-LA) could decrease S. Typhimurium biofilm mass by 57.26%. According to the viable count method, the most effective treatment was the sequential use of ozonated water and lactic acid (O-LA), which reduced S. aureus and S. Typhimurium biofilms by 1.76 and 4.06 log, respectively. It was concluded that the sequential use of ozonated water and organic acids can be considered a practical and environmentally friendly approach to control biofilms.

Comparison of the agar contact method and the wet-dry double swabbing method for determining the total viable bacterial count on pig carcass surfaces

A practical and representative sampling method for microbiological examination of the slaughter process is useful for identifying abattoir-specific risk factors within the pig slaughter line. The aim of this study was to examine the suitability of an agar contact method (ACM), where the agar was homogenized before the microbiological processing, in comparison with the wet-dry double swabbing method (WDSM) for quantitative determination of total viable counts (TVC) on pig skin surfaces. In our experimental trial, pig skin pieces were artificially contaminated at 2 levels (3 log and 7 log cfu/ml) with a suspension of bacteria species commonly found on pig skin and cultivated in vitro. Within our field trial, pig carcasses were investigated at pre-chilling in an abattoir under standard processing conditions. For both sampling methods, TVC was determined, and statistical equivalence tests were calculated. Linear regression models showed the similarity of the sampling methods, with coefficient of determination (R2) > 90% and slope parameters of nearly 1 for both trials separately. Statistically significant equivalence between the 2 sampling methods was proven in both trials (with p < 0.0001 within an equivalence range of ± 0.5 log cfu/ml, respectively). The field trial revealed TVC on carcass surfaces sometimes at or below the lower detection limit for the ACM, while TVC from all carcasses were able to be determined by WDSM. Overall, low contamination levels were less reliably detectable by ACM than by WDSM. The ACM can be seen as an additional and suitable sampling procedure for pig skin and can contribute to the identification of abattoir specific risk factors for investigations of the hygienic status at process stages along the pig slaughter line.

Oxygen Sensor-Based Respirometry and the Landscape of Microbial Testing Methods as Applicable to Food and Beverage Matrices.

The current status of microbiological testing methods for the determination of viable bacteria in complex sample matrices, such as food samples, is the focus of this review. Established methods for the enumeration of microorganisms, particularly, the 'gold standard' agar plating method for the determination of total aerobic viable counts (TVC), bioluminescent detection of total ATP, selective molecular methods (immunoassays, DNA/RNA amplification, sequencing) and instrumental methods (flow cytometry, Raman spectroscopy, mass spectrometry, calorimetry), are analyzed and compared with emerging oxygen sensor-based respirometry techniques. The basic principles of optical O2 sensing and respirometry and the primary materials, detection modes and assay formats employed are described. The existing platforms for bacterial cell respirometry are then described, and examples of particular assays are provided, including the use of rapid TVC tests of food samples and swabs, the toxicological screening and profiling of cells and antimicrobial sterility testing. Overall, O2 sensor-based respirometry and TVC assays have high application potential in the food industry and related areas. They detect viable bacteria via their growth and respiration; the assay is fast (time to result is 2-8 h and dependent on TVC load), operates with complex samples (crude homogenates of food samples) in a simple mix-and-measure format, has low set-up and instrumentation costs and is inexpensive and portable.

Development of a Quality Index Method Scheme for Sensory Assessment of Chilled Yellowfin Tuna

Background: Quality monitoring and/or assessment are parts of a freshness/quality control system, which is of utmost importance for fresh seafood, especially Scombridae fish. The quality index method (QIM) is a simple, convenient, unique, and reliable tool to determine the sensory status and estimate the remaining shelf life of aqua products. Objective: This study aimed to develop a QIM scheme for chilled stored yellowfin tuna and apply the protocol in the fish quality evaluation and storage time estimation. Method: Eight gutted yellowfin tuna of 20, 30, and 40 kg up were used in the study. Five panelists participated in the QIM development, training and application. Control and/or validation analyses were sensory assessment by a control sheet, total volatile basic nitrogen (TVB-N) quantification, and total viable count (TVC) determination. Chilled storage of tuna was performed in liquid ice and traditional crushed block ice. Partial least square regression (PLS-R) was conducted on quality index (QI) dataset over storage time to find the regression line and prediction accuracy. Results: The established QIM protocol for gutted yellowfin tuna comprised 6 attributes (namely, color of whole fish, odor of whole fish and flesh, eyes, appearance of whole fish, flesh color and flesh texture) and a maximal QI of 15. The PLS-R showed that QI could be used to estimate the remaining time with a precision of ± 2.0 and 1.4 days for fish stored in slurry ice and crushed ice, respectively. The TVB-N content in the fish flesh maintained below the acceptable level of 25 mg N/100 g throughout the storage period, which made the parameter impractical to detect the fish shelf life. The TVC overreached the allowable level of 107 CFU/g around the time of fish rejection by the sensory method. Conclusion: The developed QIM scheme for yellowfin tuna showed to be more advantageous in detecting fish quality changes compared to the control sensory method and could be used to estimate the fish's remaining shelf life.

Microbial quality and safety of ready-to-eat street-vended foods sold in selected locations in Kenya

Objectives: Street-vended foods (SVFs) are a major contributor to foodborne diseases, especially in developing countries, where their sale is largely uncontrolled. Foodborne diseases have often been linked to high morbidity and mortality in some developing countries such as Kenya, demonstrating their public health and societal significance. The objective of this study was to determine the microbial quality and safety of ready-to-eat (RTE) foods sold in selected locations within Thika town in Kiambu County, Kenya. Material and Methods: A total of 199 food samples consisting of cereals, sliced fruits, salads, groundnuts, tubers, fruit juices, boiled deshelled eggs, smokies, and sausages were randomly collected for microbial analysis. Determination of total viable count (TVC), total coliform count (TCC), yeast and molds count (YMC), Escherichia coli counts, Staphylococcus aureus counts as well as the presence of Salmonella spp ., and Listeria monocytogenes were determined following standard microbiological methods. Results: Results revealed that plant-based foods had significantly (P &lt; 0.01) higher TVC, TCC, YMC, and S. aureus counts compared to animal-based foods. The levels of TVC, TCC, YMC, E. coli, and S. aureus ranged from 6.590 ± 1.020 to 3.377 ± 1.764, 5.567 ± 2.233 to 1.594 ± 2.299, 5.052 ± 1.201 to 1.595 ± 2.146, 2.033 ± 1.229 to 0.000 ± 0.000, and 5.972 ± 1.170 to 1.888 ± 1.660 Log10 CFU/g, respectively. At least nine food samples were contaminated with E. coli although the chance for contamination was significantly (P = 0.0002) higher (15 times) in plant-based foods compared to animal-based foods. At least one sample in each food type was contaminated with S. aureus with contamination levels above 1.888 ± 1.660 Log10 CFU/g. Salmonella spp. was only detected in boiled arrowroots (25%), boiled deshelled eggs (5.6%), French fries (5.6%), juices (5.0%), and cereals (11.1%), while L. monocytogenes were not detected in any food sample. Conclusion: These findings demonstrate that RTE SVFs sold in this region constitute a potential health hazard to consumers because of the presence of Salmonella spp., and high counts of E. coli and S. aureus. These foods are, therefore, microbiologically unsafe and unsuitable for human consumption as they may cause foodborne disease outbreaks.

Microbial quality and safety of ready-to-eat street-vended foods sold in selected locations in Kenya

OBJECTIVES:Street-vended foods (SVFs) are a major contributor to foodborne diseases, especially in developing countries, where their sale is largely uncontrolled. Foodborne diseases have often been linked to high morbidity and mortality in some developing countries such as Kenya, demonstrating their public health and societal significance. The objective of this study was to determine the microbial quality and safety of ready-to-eat (RTE) foods sold in selected locations within Thika town in Kiambu County, Kenya.MATERIAL AND METHODS:A total of 199 food samples consisting of cereals, sliced fruits, salads, groundnuts, tubers, fruit juices, boiled deshelled eggs, smokies, and sausages were randomly collected for microbial analysis. Determination of total viable count (TVC), total coliform count (TCC), yeast and molds count (YMC), Escherichia coli counts, Staphylococcus aureus counts as well as the presence of Salmonella spp ., and Listeria monocytogenes were determined following standard microbiological methods.RESULTS:Results revealed that plant-based foods had significantly (P &lt; 0.01) higher TVC, TCC, YMC, and S. aureus counts compared to animal-based foods. The levels of TVC, TCC, YMC, E. coli, and S. aureus ranged from 6.590 ± 1.020 to 3.377 ± 1.764, 5.567 ± 2.233 to 1.594 ± 2.299, 5.052 ± 1.201 to 1.595 ± 2.146, 2.033 ± 1.229 to 0.000 ± 0.000, and 5.972 ± 1.170 to 1.888 ± 1.660 Log10 CFU/g, respectively. At least nine food samples were contaminated with E. coli although the chance for contamination was significantly (P = 0.0002) higher (15 times) in plant-based foods compared to animal-based foods. At least one sample in each food type was contaminated with S. aureus with contamination levels above 1.888 ± 1.660 Log10 CFU/g. Salmonella spp. was only detected in boiled arrowroots (25%), boiled deshelled eggs (5.6%), French fries (5.6%), juices (5.0%), and cereals (11.1%), while L. monocytogenes were not detected in any food sample.CONCLUSION:These findings demonstrate that RTE SVFs sold in this region constitute a potential health hazard to consumers because of the presence of Salmonella spp., and high counts of E. coli and S. aureus. These foods are, therefore, microbiologically unsafe and unsuitable for human consumption as they may cause foodborne disease outbreaks.

Improving and Comparing Probiotic Plate Count Methods by Analytical Procedure Lifecycle Management.

Probiotics are live microorganisms that confer a health benefit to the host when administered in adequate amounts. This definition links probiotic efficacy to microbial viability. The current gold standard assay for probiotic potency is enumeration using classical microbiology plating-based procedures, yielding results in colony-forming units (CFU). One drawback to plating-based procedures is high variability due to intrinsic and extrinsic uncertainties. These uncertainties make comparison between analytical procedures challenging. In this article, we provide tools to reduce measurement uncertainty and strengthen the reliability of probiotic enumerations by using analytical procedure lifecycle management (APLM). APLM is a tool that uses a step-by-step process to define procedure performance based on the concept that the reportable value (final CFU result) must be fit for its intended use. Once the procedure performance is defined, the information gathered through APLM can be used to evaluate and compare procedures. Here, we discuss the theory behind applying APLM and give practical information about its application to CFU enumeration procedures for probiotics using a simulated example and data set. Data collected in a manufacturer’s development laboratory is included to support application of the concept. Implementation of APLM can lead to reduced variability by identifying specific factors (e.g., the dilution step) with significant impact on the variability and providing insights to procedural modifications that lead to process improvement. Understanding and control of the analytical procedure is improved by using these tools. The probiotics industry can confidently apply the information and analytical results generated to make decisions about processes and formulation, including overage requirements. One benefit of this approach is that companies can reduce overage costs. More reliable procedures for viable cell count determinations will improve the quality evaluation of probiotic products, and hence manufacturing procedures, while ensuring that products deliver clinically demonstrated beneficial doses.

Improving Phage-Biofilm In Vitro Experimentation.

Bacteriophages or phages, the viruses of bacteria, are abundant components of most ecosystems, including those where bacteria predominantly occupy biofilm niches. Understanding the phage impact on bacterial biofilms therefore can be crucial toward understanding both phage and bacterial ecology. Here, we take a critical look at the study of bacteriophage interactions with bacterial biofilms as carried out in vitro, since these studies serve as bases of our ecological and therapeutic understanding of phage impacts on biofilms. We suggest that phage-biofilm in vitro experiments often may be improved in terms of both design and interpretation. Specific issues discussed include (a) not distinguishing control of new biofilm growth from removal of existing biofilm, (b) inadequate descriptions of phage titers, (c) artificially small overlying fluid volumes, (d) limited explorations of treatment dosing and duration, (e) only end-point rather than kinetic analyses, (f) importance of distinguishing phage enzymatic from phage bacteriolytic anti-biofilm activities, (g) limitations of biofilm biomass determinations, (h) free-phage interference with viable-count determinations, and (i) importance of experimental conditions. Toward bettering understanding of the ecology of bacteriophage-biofilm interactions, and of phage-mediated biofilm disruption, we discuss here these various issues as well as provide tips toward improving experiments and their reporting.

Quality Index Method for Freshness Assessment of Chilled Japanese Flying Squid (Todarodes pacificus)

Aims: To develop and apply a quality index method (QIM) scheme for evaluating the freshness and estimating the shelf life of raw whole Japanese flying squid (Todarodes pacificus) stored at low temperatures.&#x0D; Study design: A QIM scheme was developed through pre-observation and formation of a preliminary scheme, finalization of the protocol and training of judges. The scheme was then applied to evaluate the freshness of squid in comparison with control methods, which were quantitative descriptive analysis (QDA), Torry scoring, and total viable count (TVC) determination.&#x0D; Place and duration of study: Nha Trang University, Vietnam, between February and June 2012; and from November 2019 to January 2020.&#x0D; Methodology: A total of 399 Japanese flying squids (Todarodes pacificus) of 50-70 g stored at 0-2°C were used in the study. Seven judges engaged in the QIM establishment and application. Control methods were QDA, Torry and TVC check. Principle component analysis (PCA) was used for studying the dataset main variance. Partial least square regression (PLS-R) was carried out to evaluate the possibility to predict storage time of the developed QIM scheme.&#x0D; Results: The formulated QIM scheme for Japanese flying squid stored at low temperatures composed of 8 parameters, which are odour, eyes, skin pigment, skin elasticity, body shape, body texture, ink sac integrity, and head-body connection, forming a quality index (QI) range of 0-15. The PLS-R showed that the developed QIM protocol could give a shelf life estimation accuracy of ± 1.0 day if 7 squids from each batch were evaluated. The PCA showed that QDA parameters clustered into good and bad attribute groups, which characterised flesh and old/spoilt squid, respectively. QDA, Torry and TVC results revealed a maximal squid shelf life of 12 days at 0-2 °C.&#x0D; Conclusion: The QIM scheme for chilled Japanese flying squid (Todarodes pacificus) could be used to estimate the remaining shelf life of the product with the precision of ± 1.0 day, using at least 7 squids of the same storage time for assessment. Squid exhibited a shelf life of 12 days at 0-2 °C.

Rapid detection and enumeration of aerobic mesophiles in raw foods using dielectrophoresis

The concept of dielectrophoresis (DEP), which involves the movement of neutral particles by induced polarization in nonuniform electric fields, has been exploited in various biological applications. However, only a few studies have investigated the use of DEP for detecting and enumerating microorganisms in foodstuffs. Therefore, we aimed to evaluate the accuracy and efficiency of a DEP-based method for enumerating viable bacteria in three raw foods: freshly cut lettuce, chicken breast, and minced pork. The DEP separation of bacterial cells was conducted at 20 V of output voltage and 6000 to 9000 kHZ of frequency with sample conductivity of 30–70 μS/cm. The accuracy and validity of the DEP method for enumerating viable bacteria were compared with those of the conventional culture method; no significant variation was observed. We found a high correlation between the data obtained using DEP and the conventional aerobic plate count culture method, with a high coefficient of determination (R2 > 0.90) regardless of the food product; the difference in cell count data between both methods was within 1.0 log CFU/mL. Moreover, we evaluated the efficiency of the DEP method for enumerating bacterial cells in chicken breasts subjected to either freezing or heat treatment. After thermal treatment at 55 °C and 60 °C, the viable cell counts determined via the DEP method were found to be lower than those obtained using the conventional culture method, which implies that the DEP method may not be suitable for the direct detection of injured cells. In addition to its high accuracy and efficiency, the DEP method enables the determination of viable cell counts within 30 min, compared to 48 h required for the conventional culture method. In conclusion, the DEP method may be a potential alternative tool for rapid determination of viable bacteria in a variety of foodstuffs.

Do Your Kids Get What You Paid for? Evaluation of Commercially Available Probiotic Products Intended for Children in the Republic of the Philippines and the Republic of Korea.

A wide range of probiotic products is available on the market and can be easily purchased over the counter and unlike pharmaceutical drugs, their commercial distribution is not strictly regulated. In this study, ten probiotic preparations commercially available for children’s consumption in the Republic of the Philippines (PH) and the Republic of Korea (SK) have been investigated. The analyses included determination of viable counts and taxonomic identification of the bacterial species present in each formulation. The status of each product was assessed by comparing the results with information and claims provided on the label. In addition to their molecular identification, safety assessment of the isolated strains was conducted by testing for hemolysis, biogenic amine production and antibiotic resistance. One out of the ten products contained lower viable numbers of recovered microorganisms than claimed on the label. Enterococcus strains, although not mentioned on the label, were isolated from four products. Some of these isolates produced biogenic amines and were resistant to one or several antibiotics. Metagenomic analyses of two products revealed that one product did not contain most of the microorganisms declared in its specification. The study demonstrated that some commercial probiotic products for children did not match their label claims. Infants and young children belong to the most vulnerable members of society, and food supplements including probiotics destined for this consumer group require careful checking and strict regulation before commercial distribution.

Rapid Microbiological Assessment in Raw Milk: Validation of a Rapid Alternative Method for the Assessment of Microbiological Quality in Raw Milk.

The consumption of dairy products and the dairy industry are one of the main global agri-food sectors for its size, economic importance, and level of technology. Microbiological quality of pasteurized milk or other milk products is dependent on microbiological quality of raw milk. A variety of microbiological count methods is available for monitoring the hygienic quality of raw milk. Among them, the pour plate method is the official essay for counting the number of colony-forming units in milk samples according to International Organization for Standardization (ISO) No. 4833-1:2013. The aim of the present study is the validation of the Micro Biological Survey (MBS) method, against the reference plate-count method, for the assessment of the microbiological quality of raw milk. This comparative study, performed in collaboration with the Istituto Zooprofilattico Sperimentale del Lazio e della Toscana M. Aleandri (IZSLT), demonstrates the accuracy of this alternative method for the determination of total viable bacterial count in cow’s raw milk. The results obtained with the MBS method highlight its potential as a valid tool for reliable microbiological analysis in dairy industries.

Determination of Colour and Total Viable Counts in Fresh and Charcoal Flue Gases Treated Beef Using Digital Colour Meter

Flesh from animals is one of the nutritious foods rich in vitamin B complex, iron, zinc, selenium, phosphorous, fats and magnesium. Due to this high food value, it attracts bacteria, yeasts, molds and other lower life forms that infest on it and hence undergoes natural decay process fast. Poor handling practices by small scale enterprise in the beef industry contribute to fifty percent loss, excluding post slaughter losses by livestock farmers. Therefore, there is need to develop accessible preservation methods that are supported by available infrastructure in order to curb beef losses. This study used charcoal flue gases sourced from combustion of charcoal briquettes in prolonging beef shelf life. Fresh beef samples were purchased from local abattoirs and exposed to flue gases. The optimum treatment time was between 10 to 15 hours depending on beef load mass. The reaction of the carbon monoxide and carbon dioxide with beef functional groups was studied using color determination. The colour lightness (L*) and redness (a*) values were L* 44 and a* 9 values for fresh beef, after treatment L* 30 and a* 4.5 indicating a strong bond of carboxy-myoglobin and on day 35 the L* 23 and a* 1.5 indicated onset of beef spoilage. The mean total aerobic counts of fresh beef, after treatment and onset spoilage were significantly different (p&lt;0.05) 4.16±4.20, 2.16±2.19 and 5.16±5.20 log CFU/cm2 respectively. The results from this study, was not more than 6.00 log CFU/cm2 approved safe microbial standards of beef for consumption by FAO.

Fish from a polluted lake (Lake Chivero, Zimbabwe): a food safety issue of concern

Abstract Objectives A study to determine food safety hazard status of fish products from Lake Chivero was conducted in selected high density suburbs of Harare. Lake water and fish were tested for E. coli O157:H7, total bacterial, fungal counts, mercury (Hg) and aflatoxin B1 (AFB1) to determine contamination levels and assessing human health hazard exposure. Materials and Methods Membrane filtration method was used to determine E. coli O157:H7 viable counts using CHROM agar. Plate count and Potato dextrose agar were used for determination of total viable bacterial and fungal counts. Concentrations of Hg and AFB1 in fish and water were determined by Atomic Absorption Spectrophotometer and High Performance Liquid Chromatography-Mass Spectrometry. A questionnaire survey was conducted on 136 adult fish consumers to determine the fish consumption patterns to assess hazard exposure against international standards. Results Significant levels of microbial contamination above international standards in both fish and water were recorded. Mean E. coli O157:H7 counts were 106 ± 10 (cfu/cm2) in fish and 52 ± 14 (cfu/100ml) in water. Mean Log10 TBC were 8.98 ± 0.26 (cfu/cm2) in fish and 9.05 ± 0.05 (cfu/ml) in water. Mean Log10 TFC were 4.83 ± 0.02 (cfu/cm2) in fish and 4.56 ± 0.03 (cfu/ml) in water. Hg and AFB1 were 0.018 (µg/kg) and 0.025 (µg/kg) in fish and 0.008 (µg/kg) and 0.005 (µg/kg) in water, both with a hazard quotient (HQ) &lt;1 using CODEX STAN 193-1995 of 2015. Conclusion Fish and water are contaminated with E. coli O157:H7, contain bacterial and fungal loads above international food safety guidance levels. Fish were caught already contaminated with pathogens together with toxigenic Hg and carcinogenic AFB1 although their concentration levels are within international food safety toxicological levels. Levels of Hg and AFB1 in water were almost double that of fish, implying bio-accumulation occurred in fish. Thus, fish consumers are exposed to food safety hazards and are at risk of contracting foodborne illnesses from consuming contaminated fish.

Effect of different types of active biodegradable films containing lactoperoxidase system or sage essential oil on the shelf life of fish burger during refrigerated storage

The present study aimed to control the spoilage of fish burger of common carp meat kept at refrigerated temperature (4 ± 2 °C) during 20 days storage using active biodegradable films containing lactoperoxidase system (LPS) or sage essential oil (SEO). Fish burgers were prepared from minced common carp meat and were wrapped in chitosan (CH), alginate (AL) and gelatin (ZH) films containing SEO or LPS. Different groups were kept in the refrigerated temperature and samples taken at day 0, 5, 10, 15 and 20 of storage time for determination of Total Viable Count (TVC), psychrotrophic bacterial count (PTC), Pseudomonas spp. (PSC) and Shewanella spp (ShC). Also, TBARS, pH and sensory properties of the groups were checked during refrigeration. Chitosan films containing LPS were the most effective package to significantly suppress the increase of TVC, PTC, Pseudomonas spp. and Shewanella spp and TBARS during 20-day storage at refrigerated condition compared with other treatments (P<0.05). Moreover, the alginate and chitosan films containing LPS and SEO had the higher ultimate pH (P<0.05). The results of this study indicated that the chitosan film containing LPS extend the shelf life of fish burgers in comparison by other treatments and control for 5 days.

The potential of biogas production from fruit wastes (Watermelon, Mango and Pawpaw)

The study determined the potential of biogas production from fruit wastes: mango, pawpaw and watermelon and their combinations. Fixed batch type anaerobic digesters were locally fabricated and used for the study. Retention time was for 45 days. The different substrates were prepared into slurry treatments by grinding and mixing with water in the ratio of 1:3, and 1:2 for only watermelon treatment because of its high moisture content. Determination of process pH, temperature and viable anaerobic counts were carried out to monitor how their variations in the anaerobic digesters affected the biogas production process, using pH meter, mercury in glass thermometer and a locally designed anaerobic glove box. Quantification of biogas yield was by liquid displacement. The pH, temperature and anaerobic counts varied over the 45 days retention time. The total volume of biogas produced from each digester at the end of the digestion was 2971 cm3, 1577 cm3, 83 cm3, 5103 cm3, 1630 cm3, 916 cm3, and 4348 cm3, from watermelon (W), mango (M), pawpaw (P), watermelon + melon (WM), pawpaw + water melon (PW), mango and pawpaw (MP) and mango, watermelon, and pawpaw (MWP), respectively. The excellent biodegradability potential displayed by watermelon waste and to a lesser extent mango waste is of great importance in waste management and the energy transition vision of Nigeria.

Biofilm-associated accumulation-associated protein (Aap): A contributing factor to the predominant growth of Staphylococcus epidermidis in platelet concentrates.

Staphylococcus epidermidis is a predominant contaminant of platelet concentrates (PCs), outcompeting other skin flora bacteria such as Staphylococcus capitis. The accumulation-associated protein (Aap), encoded by the aap gene, is involved in formation of bacterial aggregates (biofilms) in S.epidermidis and is absent in S.capitis. In this study, the role of S.epidermidis aap in enhancing biofilm formation and conferring an advantageous growth in PCs was investigated. Biofilm formation assays of S.epidermidis 1457, S.epidermidis 1457∆aap, S.capitis 517 and S.capitis 517 carrying S.epidermidis aap (S.capitis 517/pRBaap) were performed in glucose-supplemented trypticase soy broth (TSBg) and PCs. Additionally, competition assays with paired cultures (1:1 ratio) of S.epidermidis and S.capitis strains were seeded in PCs, followed by determination of viable counts of each organism at the end of PC storage. Staphylococcus epidermidis aap had no effect on biofilm formation in TSBg. By contrast in PCs, S.epidermidis 1457 showed higher biofilm formation than S.epidermidis 1457∆aap (P<0·05). Biofilm formation was also enhanced in S.capitis 517/pRBaap compared to S.capitis 517 (P=0·054). Competition assays showed that S.epidermidis 1457 outcompeted S.capitis 517, and importantly, S.capitis 517/pRBaap outcompeted S.capitis 517 and S.epidermidis 1457∆aap. This study demonstrated that S.epidermidis aap plays a role in biofilm formation in PCs conferring an advantageous proliferation to skin flora bacteria in this milieu. The molecular mechanisms of action of Aap merit further investigation.

Flow Cytometry: Evolution of Microbiological Methods for Probiotics Enumeration.

The purpose of this trial was to verify that the analytical method ISO 19344:2015 (E)-IDF 232:2015 (E) is valid and reliable for quantifying the concentration of the probiotic Lactobacillus rhamnosus GG (ATCC 53103) in a finished product formulation. Flow cytometry assay is emerging as an alternative rapid method for microbial detection, enumeration, and population profiling. The use of flow cytometry not only permits the determination of viable cell counts but also allows for enumeration of damaged and dead cell subpopulations. Results are expressed as TFU (Total Fluorescent Units) and AFU (Active Fluorescent Units). In December 2015, the International Standard ISO 19344-IDF 232 "Milk and milk products-Starter cultures, probiotics and fermented products-Quantification of lactic acid bacteria by flow cytometry" was published. This particular ISO can be applied universally and regardless of the species of interest. Analytical method validation was conducted on 3 different industrial batches of L. rhamnosus GG according to USP39<1225>/ICH Q2R1 in term of: accuracy, precision (repeatability), intermediate precision (ruggedness), specificity, limit of quantification, linearity, range, robustness. The data obtained on the 3 batches of finished product have significantly demonstrated the validity and robustness of the cytofluorimetric analysis. On the basis of the results obtained, the ISO 19344:2015 (E)-IDF 232:2015 (E) "Quantification of lactic acid bacteria by flow cytometry" can be used for the enumeration of L. rhamnosus GG in a finished product formulation.

Determination of Total Viable Count in Rainbow-Trout Fish Fillets Based on Hyperspectral Imaging System and Different Variable Selection and Extraction of Reference Data Methods

The aims of this study were to investigate the effect of different reference data extraction (colony-counting) and selection variable methods (Regression Coefficient: RC; Forward and Stepwise Multiple Regression: FMR and SMR) on the performance of PLSR and MLR model to predict TVC value in rainbow-trout fish fillets. TVC values were measured based on manual and digital image (OpenCFU, IMJ, and Photoshop) counting methods. The most and lowest prediction powers were obtained for Photoshop-PLSR and OpenCFU-PLSR, respectively (R2p = 0.873 and 0.815; RMSEP = 0.761 and 0.884 Log10CFU/g). In simplified-model FMR-MLR has superior performance (R2p = 0.89 and RMSEP = 0.65 Log10CFU/g). In simplified PLSR model group, RC-PLSR showed better performance (R2p = 0.866 and RSMEP = 0.782). This distribution map of TVC load was generated by transferring the FMR-Photoshop-MLR model to each pixel of the images. HSI technique revealed a great potential to determine TVC of rainbow-trout fillets and the type of colony counting method influenced on prediction power of the model.

Effect of the Seasons and Salt Concentrations on Microbial Load of Wet-Salted Fermented Product (Fassiekh)

The study aims at investigating the microbial load of wet-salted fermented product (a traditional fermented product in Sudan named locally; fassiekh) and determination of total viable bacterial count, according to salt concentrations (20%, 25% and 30% of the fish weight) and seasons (summer, autumn and winter) variations. Fessiekh processed from popular fessiekh fish species (Hydrocynus spp, local name: Kass).The isolation and identification of bacteria and mould were examined for the microbial quality of fassiekh. The total viable count of bacteria in fresh fish used as raw materials in fessiekh preparation (Hydrocynus froskalii), ranged from 2x103-5.5x103cfu/g. The concentrations of salt had direct effect on the microbial quality of salted Hydrocynus froskalii. It was observed that the total bacterial count was increased during the first five days in summer and autumn while at winter season it showed increases till the tenth day, followed by remarkable decreasing. The counts began to decrease as salting proceeded. Five Staphylococcus spp (Staph.aureus, Staph.rostri, Staph.lentus, Staph.epidermidis and Staph.pyogen) were isolated from all samples of salted fish and appraises about 46.77% of total isolates. Also three species of Micrococcus were isolated (Micro.leuteus, Micro.roseus and Micro.lactis), and Aerococcus viridans, and they represented 36.17% &amp; 12.9% of all isolated samples respectively. The viable bacteria counts of commercial fessiekh were significantly higher (p&lt;0.05) when compared to the experimentally salted fish at the same salt concentrations. No yeasts or fungi were detected in tested samples.