Media for Aeromonas spp., Plesiomonas shigelloides and Pseudomonas spp. from food and environment

Chapter 8 Media for Aeromonas spp., Plesiomonas shigelloides and Pseudomonas spp. from food and environment

In September 2014, a small gastroenteritis outbreak occurred in a Greek restaurant. Primary investigations by official food surveillance revealed significant hygienic problems in the premises. Food samples and environmental samples were analyzed for the presence of bacterial and viral food pathogens. Norovirus genogroup I (GI) was detected in 2 environmental samples and in mixed salad. At the same time, stool samples from patients were analyzed and norovirus GI was detected. Further investigations revealed the presence of norovirus GI on some of the restaurant employees. Comparison of nucleic acid sequences revealed full sequence homology between norovirus RNA genotype 1.2 in food, environmental and stool samples, suggesting a common source of contamination and infection. Sequence analysis of food and environmental samples was facilitated by application of a system for total RNA amplification. Despite the fact that original source of contamination could be determined doubtlessly, observed weaknesses in the food production that caused this outbreak were discussed. The mixed salad could have been contaminated either by the lettuce contaminated at primary production or by one of the food-handlers. The investigation of the path of infection is necessary for the kind of legal consequences to be directed by authorities and may contribute to measures to eliminate possible sources of food contamination.

Analytical improvements shown over four interlaboratory studies of perfluoroalkyl substances in environmental and food samples

Chapter 20 Media for Pseudomonas spp. and related genera from food and environmental samples

Foodborne illness associated with food service establishments is an important food safety issue in Korea. In this study, foodborne pathogens (Bacillus cereus, Clostridium perfringens, Escherichia coli, pathogenic Escherichia coli, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and Vibrio parahaemolyticus) and hygiene indicator organisms [total viable cell counts (TVC), coliforms] were analyzed for food and environmental samples from foodservice establishments at schools in Gyeonggi province. Virulence factors and antimicrobial resistance of detected foodborne pathogens were also characterized. A total of 179 samples, including food (n=66), utensil (n=68), and environmental samples (n=45), were collected from eight food service establishments at schools in Gyeonggi province. Average contamination levels of TVC for foods (including raw materials) and environmental samples were 4.7 and 4.0 log CFU/g, respectively. Average contamination levels of coliforms were 2.7 and 4.0 log CFU/g for foods and environmental swab samples, respectively. B. cereus contamination was detected in food samples with an average of 2.1 log CFU/g. E. coli was detected only in raw materials, and S. aureus was positive in raw materials as well as environmental swab samples. Other foodborne pathogens were not detected in all samples. The entire B. cereus isolates possessed at least one of the diarrheal toxin genes (hblACD, nheABC, entFM, and cytK enterotoxin gene). However, ces gene encoding emetic toxin was not detected in B. cereus isolates. S. aureus isolates (n=16) contained at least one or more of the tested enterotoxin genes, except for tst gene. For E. coli and S. aureus, 92.7% and 37.5% of the isolates were susceptible against 16 and 19 antimicrobials, respectively. The analyzed microbial hazards could provide useful information for quantitative microbial risk assessment and food safety management system to control foodborne illness outbreaks in food service establishments.

Facile ultrasonication-assisted synthesis of Purpald-functionalized silver nanoparticles for the rapid spectrophotometric detection of acetamiprid pesticide in food and environmental samples

Human noroviruses (HuNoVs) are the major cause of non-bacterial acute gastroenteritis worldwide. RT-qPCR is a widely used method to detect HuNoVs. However, the method is unable to extract a virus from environmental samples and to discriminate between infectious and non-infectious viruses. In this study, we explored a new in situ capture RT-qPCR (ISC-RT-qPCR) methodology to estimate the infectivity of HuNoV in environmental and food samples. This assay was based on capturing encapsidated HuNoV by viral receptors, followed by in situ amplification of the captured viral genomes by RT-qPCR. We demonstrated that ISC-RT-qPCR did not capture and enable signal amplification of the heat-denatured Tulane virus (TV) and HuNoVs. Therefore, ISC-RT-qPCR provides better estimates for infectivity of HuNoV than RT-qPCT. We then utilized the ISC-RT-qPCR to detect HuNoV in environmental water samples and food samples, as compared to a conventional RT-qPCR procedure. The presence of HuNoV was examined in 36 oyster samples from retail markets using by both assays for detection. The detection rates of HuNoV in gill, digestive glands, and other tissues were 33.3%, 25%, and 19.4%, respectively, by ISC-RT-qPCR; and were 5.6%, 11.1%, and 11.1%, respectively, by RT-qPCR. ISC-RTqPCR is more sensitive than RT-qPCR for the detection of HuNoV in oysters. By contrast, the HuNoV detection rate by ISC-RTqPCR is lower for environmental samples. Of the 72 water samples that tested positive for HuNoV by RT-qPCR, only 20 (27.8%) of these tested positive by ISC-RT-qPCR, suggesting that 72.2% of RT-qPCR-positive samples were unlikely to be infectious. A better detection rate by ISC-RT-qPCR in oyster samples indicates the likelihood of infectious HuNoV that accumulated in oysters, and a lower detection rate of HuNoV in environmental water by ISC-RT-qPCR, indicating that the majority of RT-qPCR-positive samples were from non-infectious viral RNA.

8 - Micro total analysis systems with nanomaterials

Improvement of an ultrasound assisted method for the analysis of total carbohydrate in environmental and food samples

ABSTRACTStaphylococcal enterotoxin B (SEB), toxic shock syndrome, the superantigens are responsible for diseases such as staphylococcal food poisoning and toxic shock syndrome. An easy and quick system is desirable to detect toxin‐producing strains. In this report, we described standardization of a novel multiplex‐polymerase chain reaction (PCR) assay for simultaneous detection of four important genes associated with the Staphylococcus aureus viz., SEB, Tsst, genus‐specific nuclease (nuc) and Fem genes along with an internal amplification control (IAC), which has now become mandatory in diagnostic PCRs, particularly when tested on environmental or food samples. This mPCR method is sensitive enough to detect cells as low as 103 cfu/mL or /g of the food samples. When evaluated on 136 food and environmental samples, the system detected 4 SEB‐positive S. aureus strains. The S. aureus strains that have been identified to contain the SEB gene in the mPCR were unequivocally detected for the toxin expression by the TECRA kit. mPCR produced a 100% correlation with conventional identification method. As SEB and Tsst are qualified as biowarfare molecules, this system is of immense help in detecting them during emergencies of biological war and suspected outbreaks of S. aureus food poisoning directly from the food and environmental samples.PRACTICAL APPLICATIONSThe virulence‐associated genes targeted in this study are super antigenic in nature and are responsible for diseases such as staphylococcal food poisoning and toxic shock syndrome, and these molecules are also qualified as biowarfare agents. The high throughput and cost‐effective multiplex PCR method reported here could identify all these genes successfully from both artificially spiked and natural food samples and may also find its application in detection of these toxin‐producing Staphylococcus aureus from clinical and environmental samples.

Neutron activation analysis has been applied for determination of selenium in environmental and food samples. Food and environmental samples from city, industrial and agricultural zones were collected with utmost care. Samples were activated in the flux 1·1013 n·cm−2·s−1 in the CIRUS reactor of BARC, Bombay, 75-Se was separated from 6.5N HCl solution using ethyl-α-isonitrosoacetoacetate (HEINA) reagent. The decontamination studies showed the method is very selective. Selenium contents of wheat, rice, vegetables, cereals pulses etc. and of soil, water, and deposits on plants and surface were determined by the procedure developed.

Currently, sample preparation is the most laborious part of the analytical process, requiring the most time and being susceptible to the most errors. In this context, numerous investigations have focused on the miniaturization of these techniques to reduce work time, costs, and errors. In this regard, microextraction by packed sorbent (MEPS) is a simple, fast, and robust sample preparation technique suitable for easy automation in several analytical systems and is applied to a wide variety of samples. Antibiotics are among the most commonly used drugs; however, their extensive and inappropriate use has garnered significant attention in the environment, human health, and food safety. This brief review is intended to provide an overview of recently reported antibiotic extraction methods based on MEPS, with a special interest in those applied to the analysis of biological, environmental, and food samples. In addition, the sample pretreatment step before extraction by the MEPS device was highlighted, as was the description of the sample-related steps within the MEPS procedure, such as extraction, washing, and elution.

Pretreatment techniques and analytical methods for phenolic endocrine disrupting chemicals in food and environmental samples

We report the findings of the study of 4185 food samples and 958 environmental samples collected in Italy in the period 1990-1999 and tested for the presence of Listeria monocytogenes. The strains isolated were biochemically and serologically characterised. We found a fairly high percentage of L. monocytogenes contamination in food (12.8%), whereas the level of contamination was lower in the environment (environment and work surfaces in food processing plants) (6.1%). Serotyping showed a prevalence of a few serotypes (i.e., 1/2a, 1/2b, 1/2c and 4b), which were the same as those found in clinical samples collected during outbreaks and from sporadic cases of listeriosis reported in Italy in the period considered. The geographical distribution of the strains of L. monocytogenes isolated from food samples is very similar to that of the clinical strains.

In this paper, we illustrate the potential of ultra-high performance liquid chromatography (UHPLC) coupled with hybrid quadrupole time-of-flight mass spectrometry (QTOF MS) for large scale screening of organic contaminants in different types of samples. Thanks to the full-spectrum acquisition at satisfactory sensitivity, it is feasible to apply both (post)-target and non-target approaches for the rapid qualitative screening of organic pollutants in food, biological and environmental samples. Different strategies have been applied and compared in this work. The first approach consists of target screening based on automatically extracting the exact analyte masses with a narrow mass window (±10 mDa). The selection of analytes can be made after MS acquisition as non-specific analyte information is required when injecting the samples. The second, non-targeted approach, consists of a first component detection step followed by the search of the detected components in home-made spectral libraries. In this work, two types of libraries have been evaluated: a theoretical database, including the molecular formula of a large number of pollutants (∼1000), and an empirical mass spectra library which includes a lower number of compounds for which reference standards were available. In all cases the confidence of the identification process was excellent, thanks to the value of information given in QTOF MSE acquisition mode (i.e. simultaneous acquisition of low and high energy TOF MS spectra in a unique run). Both, target and non-target approaches, are complementary and both have advantages and drawbacks. Their application to different types of samples has allowed the detection of diverse organic compounds, for example the mycotoxin fumonisin B1 in food samples, cocaine and several metabolites in human urine, as well as several pesticides, antibiotics and drugs of abuse in urban wastewater.