Scientific Achievements in the Study of the Occurrence and Antimicrobial Susceptibility Profile of Major Foodborne Pathogenic Bacteria in Foods and Food Processing Environments in Romania: Review of the Last Decade

Pathogenic bacteria are recognized as a major cause of foodborne diseases in humans, globally, with negative impact on the economy of each country. The aim of the present review was to obtain a comprehensive understanding about the frequency of isolation, diversity, and antimicrobial susceptibility profile of the six major foodborne pathogenic bacteria in food matrices and food processing environment, in Romania. In this regard, results of relevant epidemiological studies, published during the last decade and retrieved from the Web of Science Core Collection database, were analyzed, with special emphasis on scientific achievements, main knowledge gaps, and future perspectives. The summarized and harmonized results offer useful insight, especially for public health authorities and researchers, having a reference effect in stimulating further opportunities for studies to be carried out to address some of the limitations of the current status.

High-flux simultaneous screening of common foodborne pathogens and their virulent factors

Rapid and sensitive detection techniques for foodborne pathogens are important to the food industry. However, traditional detection methods rely on bacterial culture in combination with biochemical tests, a process that typically takes 4-7 days to complete. In this study, we described a high-flux polymerase chain reaction (PCR) method for simultaneous detection of nine targeted genes (rfbE, stx1, stx2, invA, oprI, tlh, trh, tdh, and hlyA) with multiplex strains. The designed primers were highly specific for their respective target gene fragments. As the selected primers follow the principles of similar melting and annealing temperature, all the targeted genes could be detected for one strain with the same PCR program. Combining with 96-well PCR plate, by adding a single different gene to each well in each row, both the ATCC strains (E. coli, Salmonella spp., V. parahaemolyticus, L. monocytogenes, P. aeruginosa, S. aureus) and the clinical strains (E. coli, P. aeruginosa, S. aureus) were simultaneously detected to carry their specific and virulence genes. Therefore, using 96-well PCR plate for PCR amplification might be applied to high-flux sequencing of specific and virulence genes.

Secretor Status is Associated with Susceptibility to Disease in a Large GII.6 Norovirus Foodborne Outbreak

Norovirus is commonly associated with food and waterborne outbreaks. Genetic susceptibility to norovirus is largely dependent on presence of histo-blood group antigens (HBGA), specifically ABO, secretor, and Lewis phenotypes. The aim of the study was to determine the association between HBGAs to norovirus susceptibility during a large norovirus foodborne outbreak linked to genotype GII.6 in an office-based company in Stockholm, Sweden, 2015. A two-episode outbreak with symptoms of diarrhea and vomiting occurred in 2015. An online questionnaire was sent to all 1109 employees that had worked during the first outbreak episode. Food and water samples were collected from in-house restaurant and tested for bacterial and viral pathogens. In addition, fecal samples were collected from 8 employees that had diarrhea. To investigate genetic susceptibility during the outbreak, 98 saliva samples were analyzed for ABO, secretor, and Lewis phenotypes using ELISA. A total of 542 of 1109 (49%) employees reported gastrointestinal symptoms. All 8 fecal samples tested positive for GII norovirus, which was also detected in coleslaw collected from the in-house restaurant. Eating at the in-house restaurant was significantly associated with risk of symptom development. Nucleotide sequencing was successful for 5/8 fecal samples and all belonged to the GII.6 genotype. HBGA characterization showed a strong secretor association to norovirus-related symptoms (P = 0.014). No association between norovirus disease and ABO phenotypes was observed. The result of this study shows that non-secretors were significantly less likely to report symptoms in a large foodborne outbreak linked to the emerging GII.6 norovirus strain.

Evolution of class 1 integrons: Mobilization and dispersal via food-borne bacteria

Class 1 integrons have played a major role in the global dissemination of antibiotic resistance. Reconstructing the history of class 1 integrons might help us control further spread of antibiotic resistance by understanding how human activities influence microbial evolution. Here we describe a class 1 integron that represents an intermediate stage in the evolutionary history of clinical integrons. It was embedded in a series of nested transposons, carried on an IncP plasmid resident in Enterobacter, isolated from the surface of baby spinach leaves. Based on the structure of this integron, we present a modified hypothesis for integron assembly, where the ancestral clinical class 1 integron was captured from a betaproteobacterial chromosome to form a Tn402-like transposon. This transposon then inserted into a plasmid-borne Tn21-like ancestor while in an environmental setting, possibly a bacterium resident in the phyllosphere. We suggest that the qacE gene cassette, conferring resistance to biocides, together with the mercury resistance operon carried by Tn21, provided a selective advantage when this bacterium made its way into the human commensal flora via food. The integron characterized here was located in Tn6007, which along with Tn6008, forms part of the larger Tn6006 transposon, itself inserted into another transposable element to form the Tn21-like transposon, Tn6005. This element has previously been described from the human microbiota, but with a promoter mutation that upregulates integron cassette expression. This element we describe here is from an environmental bacterium, and supports the hypothesis that the ancestral class 1 integron migrated into anthropogenic settings via foodstuffs. Selection pressures brought about by early antimicrobial agents, including mercury, arsenic and disinfectants, promoted its initial fixation, the acquisition of promoter mutations, and subsequent dissemination into various species and pathogens.

[Development of multiplex oligonucleotide ligation-PCR-universal DNA microarrays for detection of foodborne pathogens]

OBJECTIVE

To develop a multiplex oligonucleotide ligation-polymerase chain reaction( MOL-PCR) based universal microarray assay for multiplexed detection of foodborne pathogens.

METHODS

Eight common foodborne pathogens causing bacterial food poisoning were selected as detection models. An upstream and downstream adjacent detection probes were designed within specific primer pair for each of eight pathogens. Target fragments of the eight pathogens were enriched by multiplex PCR and used as ligation templates. Abundant fluorescently labeled single-stranded amplicons containing anti-tag sequences were gained by multiplex ligase detection reaction and asymmetric PCR labeling with universal primers. The products could be detected by hybridization with corresponding tag sequences immobilized on DNA microarrays.

RESULTS

The results indicated that the assay could specifically identify all eight pathogens in single and multiple infections. The detection limits were( 1. 1- 8. 5) × 10~2 CFU /mL of pure bacterial cultures. The microarray results for 96 food poisoning and clinical diarrheal samples were consistent with that of traditional culture, biochemical identification and real-time PCR.

CONCLUSION

The assay provides a novel platform for rapid, accurate, sensitive and high-throughput detection of pathogenic bacteria of foodborne diseases.

Multiplex Detection of Food-Borne Pathogens

Detection of food-borne pathogens is traditionally carried out by plating out techniques in selective or differential media using Petri agar dishes or other culture-dependent methods, usually designed for each pathogen to be detected. These classical methods are time and personnel consuming and also may last for up to 5 days in the case of final confirmation of some specific pathogens.Here we describe a method for fast multiplex detection of nine food-borne pathogens (all species usually required under most countrylegislations) by means of a single multiplex PCR reaction coupled to a capillary electrophoresis detection, in just 2-2.5 h and with a minimum cost of around 2 € per sample and nine pathogens. This method saves consumables and personnel time and allows a faster detection of any possible contaminated food batches at industrial level, therefore helping to prevent future food-borne outbreaks at clinical level.

Staphylococcus aureus and staphylococcal food-borne disease: an ongoing challenge in public health

Staphylococcal food-borne disease (SFD) is one of the most common food-borne diseases worldwide resulting from the contamination of food by preformed S. aureus enterotoxins. It is one of the most common causes of reported food-borne diseases in the United States. Although several Staphylococcal enterotoxins (SEs) have been identified, SEA, a highly heat-stable SE, is the most common cause of SFD worldwide. Outbreak investigations have found that improper food handling practices in the retail industry account for the majority of SFD outbreaks. However, several studies have documented prevalence of S. aureus in many food products including raw retail meat indicating that consumers are at potential risk of S. aureus colonization and subsequent infection. Presence of pathogens in food products imposes potential hazard for consumers and causes grave economic loss and loss in human productivity via food-borne disease. Symptoms of SFD include nausea, vomiting, and abdominal cramps with or without diarrhea. Preventive measures include safe food handling and processing practice, maintaining cold chain, adequate cleaning and disinfection of equipment, prevention of cross-contamination in home and kitchen, and prevention of contamination from farm to fork. This paper provides a brief overview of SFD, contributing factors, risk that it imposes to the consumers, current research gaps, and preventive measures.

Antibiotics sensitivity of Candida clinical and food-borne isolates

Candida is a yeast species recognized as the most frequent etiological agent of systemic and invasive thrush in humans. Invasions can affect all tissues, organs and systems of human in various stages of development. In the last 10 years Candida infections have increased 15 times. The purpose of our study was to determine the sensitivity of four antibiotics belonging to three different groups of antifungal agents against clinical and food-borne Candida strains. Our studies showed that of all tested strains, 7% was resistant to nystatin, 32% to fluconazole, 23% to voriconazole, and no strains grew in the presence of caspofungin. Despite the differences in biochemical profiles of clinical and food-borne isolates of Candida, a group of strains showing resistance to antibiotics include both types of isolates. At the same time circulating of antibiotic-resistant strains outside the hospital environment and the yeast infection via food is possible.

Escherichia coli O104:H4 outbreak--have we learnt a lesson from it?

Shiga toxin-producing Escherichia coli (STEC) strains belong to the group of pathogens that cause bloody diarrhea and hemorrhagic colitis with often severe complications. The main problem with human pathogenic E. coli strains, including STEC, is a wide spectrum of phenotypes and clinical manifestations. It is related to a variety of exchangeable genetic elements, like plasmids, bacteriophages, transposons and pathogenicity islands, that take part in horizontal gene transfer which influences creation of new dangerous bacterial strains. A good example of this phenomenon is a novel Shiga toxin-producing E. coli O104:H4 serotype that was associated with a widespread and severe foodborne disease outbreak in Germany in 2011. The O104:H4 strain was created by a number of horizontal gene transfer events between two distinct pathogens, resulting in the emergence of the new, atypical strain. That outbreak proved that also rare and unusual serotypes of STEC may be a significant risk factor and that the procedures recommended for STEC detection were not suitable to deal with this kind of pathogens. With respect to new combinations of chromosomal and extrachromosomal elements in susceptible bacterial hosts, epidemics and frequent human infections caused by STEC strains, we suggest that more attention should be paid to the development and improvement of diagnostic methods. It is difficult to determine STEC bacteria by general microbiological, biochemical and immunological assays, because strains can vary dramatically in their phenotypic and serotypic properties. It is postulated that standardized genetic tests, based on detection of features most frequently presented by STEC, particularly those located on easily exchangeable elements (such as Shiga toxin-encoding phages), can be more adequate for STEC detection.

InlA promotes dissemination of Listeria monocytogenes to the mesenteric lymph nodes during food borne infection of mice

Intestinal Listeria monocytogenes infection is not efficient in mice and this has been attributed to a low affinity interaction between the bacterial surface protein InlA and E-cadherin on murine intestinal epithelial cells. Previous studies using either transgenic mice expressing human E-cadherin or mouse-adapted L. monocytogenes expressing a modified InlA protein (InlA(m)) with high affinity for murine E-cadherin showed increased efficiency of intragastric infection. However, the large inocula used in these studies disseminated to the spleen and liver rapidly, resulting in a lethal systemic infection that made it difficult to define the natural course of intestinal infection. We describe here a novel mouse model of oral listeriosis that closely mimics all phases of human disease: (1) ingestion of contaminated food, (2) a distinct period of time during which L. monocytogenes colonize only the intestines, (3) varying degrees of systemic spread in susceptible vs. resistant mice, and (4) late stage spread to the brain. Using this natural feeding model, we showed that the type of food, the time of day when feeding occurred, and mouse gender each affected susceptibility to L. monocytogenes infection. Co-infection studies using L. monocytogenes strains that expressed either a high affinity ligand for E-cadherin (InlA(m)), a low affinity ligand (wild type InlA from Lm EGDe), or no InlA (ΔinlA) showed that InlA was not required to establish intestinal infection in mice. However, expression of InlA(m) significantly increased bacterial persistence in the underlying lamina propria and greatly enhanced dissemination to the mesenteric lymph nodes. Thus, these studies revealed a previously uncharacterized role for InlA in facilitating systemic spread via the lymphatic system after invasion of the gut mucosa.

Molecular characterization of Salmonella spp directly from snack and food commonly sold in Lagos, Nigeria

Food borne Salmonella infection is an important cause of morbidity and mortality. A total of 200 food samples commonly sold in Lagos, Nigeria comprising raw and cooked meat as well as meat products and spoilt meat were analysed for the presence of Salmonella spp using REVEAL serology kit, culture methods employing RPVA (Rappaport Vassiliadis agar), SSA (Salmonella-Shigella agar) and BSA (brilliant sulphite agar) and PCR method for direct detection from samples using primer salm3/4 and ST11/ST15 sets. Using the REVEAL serology kit, 74% of the samples were positive for Salmonella spp, while culture methods showed only 19% to be Salmonella spp. The PCR method revealed that Salmonella spp was present in 62% and 54% of the samples using primer set salm3/4 and ST11/ST15, respectively. However, the primer set ST11/ST15 was more reliable in the identification of Salmonella spp directly from food samples. These tools should prove useful in the continuous monitoring and control strategies especially for ready-to-eat foods, as well as in retail meat outlets, slaughter houses, fast food restaurants for the prevention and reduction of this pathogen that is of significant importance in the food industry.

[Molecular investigation of enteroaggregative, shiga toxin-producing E. coli O104:H4 isolated in Poland during the recent international outbreak--characteristic of epidemic clone]

Since early May 2011 a large food-borne outbreak caused by E. coli O104:H4 affected Germany then spread over 13 European countries, U.S.A. and Canada. The outbreak strain was found to possess an unusual combination of enteroaggregative E. coli pathotype with StxII. In this report we described the molecular investigation of epidemic clone in Poland during the international outbreak. We confirmed three cases of E. coli O104:H4 infections. The molecular characteristics of the Polish E. coli O104:H4 isolates including virulence profile, antimicrobial resistance, PFGE and plasmids profiles were corresponded with Germany outbreak strains.

Multiresistant Salmonella enterica serovar 4,[5],12:i:- in Europe: a new pandemic strain?

A marked increase in the prevalence of S. enterica serovar 4,[5],12:i:- with resistance to ampicillin, streptomycin, sulphonamides and tetracyclines (R-type ASSuT) has been noted in food-borne infections and in pigs/pig meat in several European countries in the last ten years. One hundred and sixteen strains of S. enterica serovar 4,[5],12:i:- from humans, pigs and pig meat isolated in England and Wales, France, Germany, Italy, Poland, Spain and the Netherlands were further subtyped by phage typing, pulsed-field gel electrophoresis and multilocus variable number tandem repeat analysis to investigate the genetic relationship among strains. PCR was performed to identify the fljB flagellar gene and the genes encoding resistance to ampicillin, streptomycin, sulphonamides and tetracyclines. Class 1 and 2 integrase genes were also sought. Results indicate that genetically related serovar 4,[5],12:i:- strains of definitive phage types DT193 and DT120 with ampicillin, streptomycin, sulphonamide and tetracycline resistance encoded by blaTEM, strA-strB, sul2 and tet(B) have emerged in several European countries, with pigs the likely reservoir of infection. Control measures are urgently needed to reduce spread of infection to humans via the food chain and thereby prevent the possible pandemic spread of serovar 4,[5],12:i:- of R-type ASSuT as occurred with S. Typhimurium DT104 during the 1990s.

Risk assessment of substances that are both genotoxic and carcinogenic

The European Food Safety Authority (EFSA) and the World Health Organization (WHO), with the support of the International Life Sciences Institute, European Branch (ILSI Europe), organized an international conference on 16-18 November 2005 to discuss how regulatory and advisory bodies evaluate the potential risks of the presence in food of substances that are both genotoxic and carcinogenic. The objectives of the conference were to discuss the possible approaches for risk assessment of such substances, how the approaches may be interpreted and whether they meet the needs of risk managers. ALARA (as low as reasonably achievable) provides advice based solely on hazard identification and does not take into account either potency or human exposure. The use of quantitative low-dose extrapolation of dose-response data from an animal bioassay raises numerous scientific uncertainties related to the selection of mathematical models and extrapolation down to levels of human exposure. There was consensus that the margin of exposure (MOE) was the preferred approach because it is based on the available animal dose-response data, without extrapolation, and on human exposures. The MOE can be used for prioritisation of risk management actions but the conference recognised that it is difficult to interpret it in terms of health risk.

Controlled multiplex PCR of enterotoxigenic Clostridium perfringens strains in food samples

A controlled multiplex polymerase chain reaction (PCR) for the detection of Clostridium(C.) perfringens enterotoxin gene (cpe) was established and compared with an in vitro antigenic detection method. Thecpe PCR and the classical method of electric immunodiffusion gave identical results. The predicted specific amplicon of the cpe gene was generated from all of the tested enterotoxigenic C. perfringens strains. In contrast, cultures of any other Clostridium species tested by PCR were negative (100% sensitivity, 100% specificity). Addition of an alphatoxin (plc) gene specific PCR as an in process control reaction was performed in order to prevent false negative PCR results. The PCR detection limit was 0.5 ng of genomic C. perfringens DNA per ml of bouillon culture. By contaminating minced meat with C. perfringens reference strains, the multiplex PCR was established as a tool for routine diagnostic laboratories. The detection limit was approximately 3.0x10(5)C. perfringens cells per gram meat. The results demonstrate the multiplex PCR as an easy, specific, sensitive and time saving diagnostic procedure. Application of this improved method should enhance the knowledge concerning epidemiological aspects of food borne diseases caused by enterotoxigenic C. perfringens.

[HLA-system antigens in patients with food poisonings caused by opportunistic bacteria]

A total of 286 convalescents after toxico-infections caused by opportunistic microorganisms were examined. The panel of anti-HLA sera permitted the typing of 34 HLA antigens, class 1. As a result, the development of the disease was found to be directly associated with antigen HLA-B17 and inversely with antigen HLA-A2. The relationship of antigens of the HLA system with alimentary toxico-infections caused by opportunistic microorganisms manifested not by the absolute resistance or predisposition to the disease, but by an increased severity of the pathological process, paralleled by a decreased level of protective antigens and an increased one of provoking antigens of the HLA system.

[Poisoning by adulterated edible oil]

In spring 1981, thousands of people living in Madrid were intoxicated by adulterated edible oil containing oleoanilide and probably other toxic substances. Due to increasing international travel Swiss doctors may also be faced with this particular disease. The case is reported of a 28-year-old woman who presented in May 1981 with a highly febrile influenza-like syndrome after consuming the adulterated oil while in Madrid. In the following weeks she developed myopathy, characterized by muscular weakness and pain, aldolase elevation and typical electromyographic disturbances, as well as edema and general discomfort. The white cell count showed eosinophilia up to 2170/mm3. Five months later, the symptoms are still continuing. Other members of the family have been exposed to the oleoanilide and exhibited various abnormalities which constitute a new clinical syndrome different from previously reported intoxications by industrial oil.

Argemone oil poisoning

A family of three suffering from Argemone oil poisoning was investigated. The effects of the oil and its toxic alkaloid sanguinarine have been discussed. A test for detecting sanguinarine has been described.