Papers by Andreja Rajkovic
Toxins
In the last decade, foodborne outbreaks and individual cases caused by bacterial toxins showed an... more In the last decade, foodborne outbreaks and individual cases caused by bacterial toxins showed an increasing trend. The major contributors are enterotoxins and cereulide produced by Bacillus cereus, which can cause a diarrheal and emetic form of the disease, respectively. These diseases usually induce relatively mild symptoms; however, fatal cases have been reported. With the aim to detected potential toxin producers that are able to grow at refrigerator temperatures and subsequently produce cereulide, we screened the prevalence of enterotoxin and cereulide toxin gene carriers and the psychrotrophic capacity of presumptive B. cereus obtained from 250 food products (cereal products, including rice and seeds/pulses, dairy-based products, dried vegetables, mixed food, herbs, and spices). Of tested food products, 226/250 (90.4%) contained presumptive B. cereus, which communities were further tested for the presence of nheA, hblA, cytK-1, and ces genes. Food products were mainly contamin...
Toxins, 2021
The thermotolerant representative of the Bacillus cereus group, Bacillus cytotoxicus, reliably ha... more The thermotolerant representative of the Bacillus cereus group, Bacillus cytotoxicus, reliably harbors the coding gene of cytotoxin K-1 (CytK-1). This protein is a highly cytotoxic variant of CytK toxin, initially recovered from a diarrheal foodborne outbreak that caused the death of three people. In recent years, the cytotoxicity of B. cytotoxicus has become controversial, with some strains displaying a high cytotoxicity while others show no cytotoxicity towards cell lines. In order to better circumscribe the potential pathogenic role of CytK-1, knockout (KO) mutants were constructed in two B. cytotoxicus strains, E8.1 and E28.3. The complementation of the cytK-1 KO mutation was implemented in a mutant strain lacking in the cytK-1 gene. Using the tetrazolium salt (MTT) method, cytotoxicity tests of the cytK-1 KO and complemented mutants, as well as those of their wild-type strains, were carried out on Caco-2 cells. The results showed that cytK-1 KO mutants were significantly less c...
Journal of Microbiological Methods, 2020
There is increasing interest in methodologies for the simultaneous concentration and detection of... more There is increasing interest in methodologies for the simultaneous concentration and detection of multiple targets in individual samples. The aim of this study was to investigate the potential presence of E. coli DNA in beef extract powder used as part of a procedure to concentrate water samples for the simultaneous detection of bacteria, viruses and protozoa. DNA from E. coli was detected in five out of six beef extract lots tested, demonstrating the limitations of its inclusion when being used in assays that will be used for the detection of E. coli in water samples. Further work is required to clarify if this phenomenon also occurs for other microorganisms of interest in water. Water used in the production and preparation of vegetables can be sourced from public supply systems, groundwater, recovered rain water, surface water from lakes, rivers or artificial ponds, or even treated wastewater in some countries (Allende and Monaghan, 2015; Jongman and Korsten, 2018; Uyttendaele et al., 2015). The microbial quality of different water sources, especially surface and treated wastewaters is of crucial importance, given the potential for pathogenic microorganisms present in the water to persist and be transferred to plant material. Several fresh produce related microbial disease outbreaks have been attributed to the use of contaminated water at different steps of the farm-to-fork chain, as exemplified by an outbreak in the United States caused by the consumption of raspberries contaminated with Cyclospora present in the water used for pesticide application (Herwaldt et al., 1997), an outbreak in Finland caused by the consumption of frozen raspberries contaminated with Norovirus during irrigation or water spraying before cooling (Ponka et al., 1999), an outbreak attributed to the consumption of spinach leaves contaminated with Escherichia coli O157, in the United States, caused by the use of water contaminated by cattle (Parker et al., 2012; Sharapov et al., 2016), or an outbreak of Salmonella Saintpaul infections in the United States related with the consumption of jalapeno or serrano peppers contaminated with farm water (Barton Behravesh et al., 2011). Ensuring the microbiological quality of the water used in the production of fresh crops is therefore of vital importance for both consumers and food business operators. Guidelines and regulations for the microbiological quality of water used for the production of crops focus on indicator microorganisms, typically referring to the presence and/or quantification of E. coli and faecal or total coliforms as criteria for microbial quality of the irrigation water (Uyttendaele et al., 2015). In Europe, the quality of water used for crop production is regulated by Regulation (EC) 852/2004 on the hygiene of foodstuffs, stating that food business operators producing or harvesting plant products should use potable water or clean water whenever necessary to prevent contamination (European Commission, 2004). The definition of potable water is outlined in EC Regulation 98/ 83/EC on the quality of water intended for human consumption, that states that water that is in contact with food should be of good microbiological quality (European Commission, 1998), with the criteria being established as the absence of E. coli and enterococci in 100 mL of water. The methods specified for the analysis of these two parameters are presented in ISO 9308-1 and ISO 7899-2, respectively. Both standards outline culture methods based on membrane filtration of the water samples, providing results in up to 48 h after sample processing. Other methodologies, such as the detection of target microorganisms via PCR, have been developed and implemented for several matrices, with the advantages of more rapid results and testing of multiple
This paper gives an overview of the food packaging process in seven food companies in the dairy a... more This paper gives an overview of the food packaging process in seven food companies in the dairy and confectionery sector. A total of 23 production runs have been analyzed regarding the three packers' rules outlined in the Serbian legislation and process capability tests related to statistical process control. None of the companies had any type of statistical process control in place. Results confirmed that more companies show overweight packaging compared to underfilling. Production runs are more accurate than precise, although in some cases the productions are both inaccurate and imprecise. Education / training of the new generation of food industry workers (both on operational and managerial level) with courses in the food area covering elements of quality assurance and statistical process control can help in implementing effective food packaging.
British Food Journal, 2015
Purpose – The purpose of this paper is to analyze the current situation of multidimensional food ... more Purpose – The purpose of this paper is to analyze the current situation of multidimensional food safety assurance in Serbia, as an official candidate for European Union (EU) membership, in relation to its EU food law harmonization efforts. Design/methodology/approach – Serbian assurance scheme was covered in this paper included food safety legislation, control and standards. Findings – The food safety system in Serbia needs improvements in the area of effectiveness and efficiency of food safety control and inspection services, knowledge and expertise of state inspectors, governmental officials, food safety consultants and auditors. Additionally, problems related to the overlapping responsibilities of various legal authorities and inspection services have to be solved, with an improved transparency and communication between legal authorities, customers, consumers and food business operators. Originality/value – An overview of current situation in food safety assurance in Serbia is sh...
Total Quality Management & Business Excellence, 2013
ABSTRACT The purpose of this paper was to analyse the implemented quality management systems (QMS... more ABSTRACT The purpose of this paper was to analyse the implemented quality management systems (QMSs) based on International Organization for Standardization (ISO) 9001 in the production/service sector, operating only with food of animal origin. The research covered the analysis of the rationale for the implementation of QMSs, the quality tools used in interviewed food companies and achieved effects and outputs. The survey comprised 59 Serbian food business operators holding ISO 9001 certificates. The obtained results revealed that the implementation of QMSs resulted in the improvement of food conformity in both of its dimensions ? food quality and food safety. Results indicated improvements towards customer satisfaction and strengthening of their competitiveness, including an increase in the sales and market share. However, none of the surveyed companies recorded any QMS improvement. Companies confirmed efforts made in product improvement but most of them did not improve their processes or confirm higher levels of effectiveness and efficiency of their systems.
Journal of Cleaner Production, 2014
Applied and Environmental Microbiology, 2007
Degradation of the quorum-sensing signal molecule N -acyl- l -homoserine lactone (AHL) in cocultu... more Degradation of the quorum-sensing signal molecule N -acyl- l -homoserine lactone (AHL) in cocultures was verified with Bacillus cereus and Yersinia enterocolitica in culture medium and in pork extract. Results showed evidence of microbial interaction when the AHL-degrading bacterium and AHL-producing bacterium were cocultured in a food-simulating condition.
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Papers by Andreja Rajkovic