Exposure and risk assessment of Staphylococcus aureus in food chain in Slovakia

Foods can been contaminated by S. aureus usually as a result of unhygienic behaviour of staff or improper conducted technological procedures. Compared to saprophytic bacteria, S. aureus does not possess significant competitive properties; however its epidemiological potential consists in multiplication to density higher than 106 cfu/g and formation of heat-resistant enterotoxins by which it causes food poisoning. Based on the data in 2001, the risk was characterized as follows: S. aureus is almost ubiquitous in ewes’ milk. It is likely that it can increase its numbers by more than 3 log cfu/g and exceed the densities from 105-106 cfu/g for a short period, particularly at farm conditions. It is unlikely that it can succeed in competition with active lactic acid bacteria when they are present in higher numbers in ewes’ milk. While exposure of S. aureus through consumption of lump ewes’ cheese made ​​from raw milk is high, its consequences are mild and severity may be assessed as negligible. The overall risk is considered as low. A kind of confirmation provides the official incidence of staphylococcal poisoning which is 0.2 per 100,000 populations (lower than the EU average of 0.6/100,000)

Effect of different environmental factors on the growth dynamics of Staphylococcus aureus in model medium

As the strains of S. aureus growing during fermentation of raw milk cheeses are exposed to the competitive growth of lactic acid bacteria and their metabolites, in this work, we characterized the growth of the strain S. aureus 2064 isolated from such environment against of water activity values and incubation temperature. Water activity of the tested media was adjusted by NaCl in the range from 0 % to 20.72 % and the experiments were carried out at 37 °C. It was found that the strain under study showed growth until NaCl concentration of 19.95 % in PCA broth. The complete growth cessation of S. aureus 2064 was observed at NaCl concentration higher than 20.72 %. The effect of water activity on the S. aureus 2064 lag-phase duration was described by the modified Davey model with discrepancy of 24.6 %. The growth rate dependence on water activity was described more precisely and reliably by Gibson model that provided the following validation indices: bias factor 0.999 and discrepancy factor 9.6 %. Based on the results we can conclude that secondary models used in this work were suitable to predict growth of S. aureus 2064, originally the ewes´cheese isolate

Growth dynamic of ewes’ lump cheese microflora

The preparation of ewes’ lump cheese has been known in Slovakia for a long time. It is made from raw or pasteurized ewes’ milk, especially due to the activity of lactic acid bacteria. The encouragement of the acidification process by the starters is profitable to use with the respect to the quality of the product. In our study we focused on the growth analysis of Staphylococcus aureus and Escherichia coli in ewes’ cheeses prepared in laboratory conditions with or without addition of starter culture from raw or heat treated milk. According to our experimental data, the addition of the lactic acid bacteria culture and the following pH decrease on the levels lower than 5.0 for 1 to 2 days were able to inhibit the growth of S. aureus and E. coli on concentrations lower than 104 CFU/g required by European Union legislation. The growth data found in this work may provide the information for food technologists and microbiologists to get the studied organisms under the control

Contribution to the debate on the microbiological quality of raw milk from vending machines

Microbiological quality or raw milk from vending maschine was analyzed in this work. Despite the pathogenic bacteria may be present in raw milk, the analyses and evaluations were focused to bacterial indicators only. Refer to total bacterial counts, the criterion ≤ 100,000 cfu/ml met 12 from 15 samples (80%) and all samples complied with the supplementary criterion of 5×104cfu/ml for psychrotrophs. Numbers of coagulase-positive staphylococci ranged closely around the average value 2.9×102cfu/ml. Average numbers of coliforms and E. coli in raw milk were found 4.34 ± 0.42 and 3.25 ± 0.83 log CFU/ml, respectively. These values significantly exceeded even the limits applicable in the past. On the basis of unchanged numbers of these bacteria in milk after 24 h at 6 °C, we assume that the high numbers of coliforms and E. coli present in milk are the result of fecal contamination and not growth. As E. coli is an indicator of faecal contamination of raw milk comprising the possible presence of Salmonella sp. Campylobacter sp. and other pathogens, microbiological survey suggested appropriate preventive measures that should be applied in terms of risk management

Bladder cancer, a review of the environmental risk factors

<p>Abstract</p> <p>Background</p> <p>Many epidemiological studies and reviews have been performed to identify the causes of bladder cancer. The aim of this review is to investigate the links between various environmental risk factors and cancer of the bladder.</p> <p>Methods</p> <p>A systematic literature search was performed using PubMed, Science Direct, Scopus, Scholar Google and Russian Google databases to identify reviews and epidemiological studies on bladder cancer risk factors associated with the environment published between 1998 and 2010. Only literature discussing human studies was considered.</p> <p>Results</p> <p>Smoking, mainly cigarette smoking, is a well known risk factor for various diseases, including bladder cancer. Another factor strongly associated with bladder cancer is exposure to arsenic in drinking water at concentrations higher than 300 µg/l. The most notable risk factor for development of bladder cancer is occupational exposure to aromatic amines (2-naphthylamine, 4-aminobiphenyl and benzidine) and 4,4'-methylenebis(2-chloroaniline), which can be found in the products of the chemical, dye and rubber industries as well as in hair dyes, paints, fungicides, cigarette smoke, plastics, metals and motor vehicle exhaust. There are also data suggesting an effect from of other types of smoking besides cigarettes (cigar, pipe, Egyptian waterpipe, smokeless tobacco and environmental tobacco smoking), and other sources of arsenic exposure such as air, food, occupational hazards, and tobacco. Other studies show that hairdressers and barbers with occupational exposure to hair dyes experience enhanced risk of bladder cancer. For example, a study related to personal use of hair dyes demonstrates an elevated bladder cancer risk for people who used permanent hair dyes at least once a month, for one year or longer.</p> <p>Conclusion</p> <p>Smoking, in particular from cigarettes, exposure to arsenic in drinking water, and occupational exposure to aromatic amines and 4,4'-methylenebis(2-chloroaniline) are well known risk factors for various diseases including bladder cancer. Although the number of chemicals related to occupational exposure is still growing, it is worth noting that it may take several years or decades between exposure and the subsequent cancer.</p

Quantitative Microbiological Analysis of Artisanal Stretched Cheese Manufacture

To evaluate the behavior of the relevant microbial populations during stretched cheese production, quantitative microbiological analysis was performed during the critical steps of the preparation. The obtained data distributions proved statistically significant increases in all indicators, on average by 4.55 ± 0.64 log CFU/g of presumptive lactococci counts, 4.06 ± 0.61 of lactobacilli, 1.53 ± 0.57 log CFU/g of coliforms, 2.42 ± 0.67 log CFU/g of Escherichia coli, 1.53 ± 0.75 log CFU/g of yeasts and molds, and 0.99 ± 0.27 log CFU/g of presumptive Staphylococcus aureus, from the early stage of milk coagulation until curd ripening (0–24 h). The following steaming/stretching process caused reductions in viable counts with the most significant inactivation effect on coliform bacteria, including E. coli (−4.0 ± 1.0 log CFU/g). Total viable counts and yeasts and molds showed 2 and almost 3 log reduction (−2.2 ± 1.1 log CFU/g and −2.6 ± 0.9 log CFU/g), respectively. The lowest decreases in presumptive S. aureus counts were estimated at the level of −1.50 ± 0.64 log CFU/g. The counts of yeasts and molds showed the best indicatory function during the entire storage period of vacuum-packaged cheeses at 6 °C

The Effect of Salt and Temperature on the Growth of Fresco Culture

The effect of environmental factors, including temperature and water activity, has a considerable impact on the growth dynamics of each microbial species, and it is complicated in the case of mixed cultures. Therefore, the aim of this study was to describe and analyze the growth dynamics of Fresco culture (consisting of 3 different bacterial species) using predictive microbiology tools. The growth parameters from primary fitting were modelled against temperature using two different secondary models. The intensity of Fresco culture growth in milk was significantly affected by incubation temperature described by Gibson&#8217;s model, from which the optimal temperature for growth of 38.6 &#176;C in milk was calculated. This cardinal temperature was verified with the Topt = 38.3 &#176;C calculated by the CTMI model (cardinal temperature model with inflection), providing other cardinal temperatures, i.e., minimal Tmin = 4.0 &#176;C and maximal Tmax = 49.6 &#176;C for Fresco culture growth. The specific growth rate of the culture under optimal temperature was 1.56 h&#8722;1. The addition of 1% w/v salt stimulated the culture growth dynamics under temperatures down to 33 &#176;C but not the rate of milk acidification. The prediction data were validated and can be used in dairy practice during manufacture of fermented dairy products

Modelling the Effect of Temperature on the Initial Decline during the Lag Phase of Geotrichum candidum

The study of lag phase provides essential knowledge for food quality control. With respect to significance of Geotrichum candidum in the food context, the aim of this study was to quantitatively characterize the relationship between temperature (6–25 °C) and initial decline period during G. candidum lag phase. The decrease in G. candidum cells in the lag phase was primary modelled by Weibull’s model to define the first-decimal reduction time (δ). Subsequently, the lag death rate (LDR) values were recalculated from δ and further modelled by using Arrhenius equations, as well as a square root model, and the models’ suitability was proven by selected statistical indices. The square root model with the estimated parameters b = 0.016 °C−1 h−0.5 and Tmin = −0.72 °C showed better indices relating to goodness of fit based on a low root mean sum of square error (RMSE = 0.028 log CFU mL−1), a higher coefficient of determination (R2 = 0.978), and the lowest value of AIC (AIC = −38.65). The present study provides a solution to the possible application of secondary predictive models to the death rate dependence on temperature during the microbial lag phase. Despite limited practical importance, under specific conditions, it is possible to consider its use, for example, in exposure assessment