Effects of cephalexin residues on the starter culture's microbial activity during the fresh cheese making process

The aim of our study was to investigate the carry-over of cephalexin from cow’s milk to cheese and whey, as well as, to study the potential impact of its presence on the microbial activity of the starter culture. Before cheese-making, the raw milk was artificially contaminated to different antibiotic levels. Cephalexin concentrations and the pH values were measured all along the process. It was found that cephalexin was transferred less into the cheese curd (1.8-4.3 % of the original amount) than into the whey (29.3-42.8 %). According to the results the concentration of cephalexin did not influence substantially the pH changes during curding nor the activity of the starter culture. However, pH of the fresh cheese showed significant (p < 0.05) differences compared to the control suggesting that antibiotic residues even below MRL level may influence the quality of product

Rapid detection of Listeria monocytogenes in raw milk and soft cheese by a redox potential measurement based method combined with real-time PCR

The incidence of outbreaks of foodborne listeriosis has indicated the need for a reliable and rapid detection of the microbe in different foodstuffs. A method combining redox potential measurement and real-time polymerase chain reaction (PCR) was developed to detect Listeria monocytogenes in artificially contaminated raw milk and soft cheese. Food samples of 25 g or 25 ml were homogenised in 225 ml of Listeria Enrichment Broth (LEB) with Oxford supplement, and the redox potential measurement technique was applied. For Listeria species the measuring time was maximum 34 h. The absence of L. monocytogenes could reliably be proven by the redox potential measurement method, but Listeria innocua and Bacillus subtilis could not be differentiated from L. monocytogenes on the basis of the redox curves. The presence of L. monocytogenes had to be confirmed by real-time PCR. The combination of these two methods proved to detect < 10 cfu/g of L. monocytogenes in a cost- and time-effective manner. This method can potentially be used as an alternative to the standard nutrient method for the rapid detection of L. monocytogenes in food

Rapid in-house detection method of Campylobacter spp. from food by redox potential monitoring combined with real-time PCR

The rapid detection of Campylobacter spp. is of utmost importance for the reduction of infections in humans by contaminated food products. The standard culturing method (ISO 10272-1:2006) involves a high time and labour demand. In this paper, we present a method that reduces the detection time of Campylobacter spp. to or below one third as compared to the ISO method, at a reduced cost per test. We used redox potential change of enrichment cultures (Bolton broth with Bolton selective supplement) for reliably selecting Campylobacter-contaminated raw milk and broiler meat samples. Identification of Campylobacter spp. in the contaminated samples was done by real-time PCR method. Culturing time to conclusive redox monitoring varied between 6 and 24 h for positive samples, depending on the contamination rate, in contrast to 136 h with the standard culturing process. However, now the Campylobacter-negative majority of food samples will not need to be tested by real-time PCR because redox potential monitoring can identify them in the selective enrichment phase. This method could be potentially used as a faster alternative to the current standard ISO 10272-1:2006, for nonregulatory monitoring purposes

Detection of Salmonella Enteritidis and Typhimurium in fresh poultry meat by rapid microbiological methods

SUMMARY Salmonellosis is one of the major foodborne diseases causing hundreds of thousands of cases each year in the EU. The EU has implemented an integrated approach to reduce its occurrence. Salmonella (S.) Typhimurium and S. Enteritidis are two causative agents responsible for some of the major foodborne diseases occurring worldwide. The necessity of fast and reliable detection methods of low cost has become of utmost importance in order to rapidly identify incidences of Salmonella contaminations of foodstuffs. Salmonella Enteritidis and Typhimurium must be absent in 25 g fresh poultry meat sample placed on the market during its shelf-life, according to the 2073/2005 EC regulation. In this study the combination of redox potential measurement based method and real-time PCR method was used for the detection of Salmonella Enteritidis and Typhimurium. During the enrichment phase the Salmonella positive samples could be screened by the redox potential measurement technique. Instead of biochemical and serological confirmation, real-time PCR technique was carried out for the further identification. The combination of redox potential and real-time PCR can accomplish results in maximum 27 hours compared to conventional methods that can take up to 7-12 days; which indicates that the combined method may be favourable for the effective and rapid identification of Salmonella Enteritidis and Typhimurium in poultry meat samples

In vitro study on the effect of doxycycline on the microbial activity of soil determined by redox-potential measuring system

The potential effect of doxycycline on the microbial activity was investigated in three types of soil. Soil samples were spiked with doxycycline, incubated at 25°C and tested at 0, 2, 4 and 6 days after treatment. The microbiological activity of the soil was characterized by the viable count determined by plate pouring and by the time necessary to reach a defined rate of the redox-potential decrease termed as time to detection (TTD).The viable count of the samples was not changed during the storage. The TTD values, however exhibited a significant increase in the 0.2–1.6 mg/kg doxycycline concentration range compared to the untreated samples indicating concentration-dependent inhibitory effect on microbial activity. The potency of the effect was different in the 3 soil types. To describe the combined effect of the doxycycline concentration and time on the biological activity of one type of soil a mathematical model was constructed and applied.The change of microbial metabolic rate could be measured also without (detectable) change of microbial count when the traditional microbiological methods are not applicable. The applied new redox potential measurement-based method is a simple and useful procedure for the examination of microbial activity of soil and its potential inhibition by antibiotics