PCR inhibitors - occurrence, properties and removal

The polymerase chain reaction (PCR) is increasingly used as the standard method for detection and characterization of microorganisms and genetic markers in a variety of sample types. However, the method is prone to inhibiting substances, which may be present in the analysed sample and which may affect the sensitivity of the assay or even lead to false-negative results. The PCR inhibitors represent a diverse group of substances with different properties and mechanisms of action. Some of them are predominantly found in specific types of samples thus necessitating matrix-specific protocols for preparation of nucleic acids before PCR. A variety of protocols have been developed to remove the PCR inhibitors. This review focuses on the general properties of PCR inhibitors and their occurrence in specific matrices. Strategies for their removal from the sample and for quality control by assessing their influence on the individual PCR test are presented and discussed.

Quo vadis? - Monitoring Campylobacter in Germany

Campylobacter is a poorly recognized foodborne pathogen, leading the statistics of bacterially caused human diarrhoea in Europe during the last years. In this review, we present qualitative and quantitative German data obtained in the framework of specific monitoring programs and from routine surveillance. These also comprise recent data on antimicrobial resistances of food isolates. Due to the considerable reduction of in vitro growth capabilities of stressed bacteria, there is a clear discrepancy between the detection limit of Campylobacter by cultivation and its infection potential. Moreover, antimicrobial resistances of Campylobacter isolates established during fattening of livestock are alarming, since they constitute an additional threat to human health. The European Food Safety Authority (EFSA) discusses the establishment of a quantitative limit for Campylobacter contamination of broiler carcasses in order to achieve an appropriate level of protection for consumers. Currently, a considerable amount of German broiler carcasses would not comply with this future criterion. We recommend Campylobacter reduction strategies to be focussed on the prevention of fecal contamination during slaughter. Decontamination is only a sparse option, since the reduction efficiency is low and its success depends on the initial contamination concentration.

Antibiotic resistance in Salmonella isolates from imported chicken carcasses in Bhutan and from pig carcasses in Vietnam

The antibiotic resistance in Salmonella isolates from 400 imported chicken carcasses in Bhutan and from 178 pig carcasses in Vietnam were analyzed on a random basis against 14 antimicrobial agents. Among the poultry samples tested, 13% were positive for Salmonella. Salmonella Enteritidis dominated with a prevalence of 80.7%, and 40 of the 42 isolates harbored two or more resistance determinants. For the 178 pigs investigated, 49.4% of the swabs and 34.8% of the lymph nodes were Salmonella positive. The most prevalent serotypes in lymph nodes were Salmonella Derby (50.0%) and Salmonella Typhimurium (27.4%). From the Salmonella isolates from pigs, only 6% were sensitive to the antimicrobial agents tested. The high resistance level of Salmonella isolates from pigs and chicken carcasses to different classes of antimicrobials should be emphasized and encourage a prudent use of these agents in animal farming, especially in pig production.

[The use of neck skin for microbial process control of fresh poultry meat using the bioluminescence method]

In this study comparative investigations of the total viable counts of bacteria and viable counts of Enterobacteriaceae with the ATP content were carried out on 70 poultry carcasses and neck skins thereof. The results revealed a correlation of total viable counts on the neck skin and on the carcass sample. Therefore the examination on total viable counts of neck skin is able to give results on the respective load of the carcass (coefficient of correlation (r) = 0.85 and coefficient of determination (R2) = 0.71). This only applies, however, to a slaughter technology at which the poultry hangs up site down with the neck skin to the bottom. The results of the ATP investigation expressed in Relative Light Units (RLU) in a bioluminescence method and total viable counts of neck skin samples are correlated (r = 0.85; R2 = 0.72). Lower values for r and R2 were estimated for RLU/Enterobacteriaceae on neck skin (r = 0.64; R2 = 0.41), for RLU/total viable counts on the carcass (r = 0.66; R2 = 0.46) and for RLU/Enterobacteriaceae on the carcass (r = 0.33; R2 = 0.11). To estimate the hygiene status in poultry slaughtery, sampling from the neck skin can replace the sampling on the whole carcass The bioluminescence method is suitable to replace the determination of total viable counts in the context of in-house hygiene supervision. However, this method seemed to be less reliable to predict the Enterobacteriaceae counts.

[The Hazard Analysis Critical Control Point concept for food production]

A future standardized EU food controlling concept demands additional efforts in food controlling systems. The Hazard Analysis Critical Control Point (HACCP) concept has already been introduced to the EU food hygiene directive 93/43/EEC as a tool to ensure food safety during production. Primarily, it is a preventive measure for health risks in food. The start of any HACCP application is the collection of data, a risk assessment, the determination of Critical Control Points (CCPs), the specification of critical limits to separate acceptable and unacceptable values for each CCP and finally keeping of records and the verification of the implemented HACCP concept. As shown in the present paper, the application of the HACCP concept should be carried out according to the specific conditions of the individual factory. It is still not known, how small food producers will be able to implement the HACCP concept and how the official food inspection service will adapt to the required inspection procedures.

[A review of the diagnostic possibilities of illegal drug administration in slaughtered animals and meat inspection]

A review of possible residues of selected antibacterial substances, hormones, beta-agonists, thyreostatics and tranquillizers in meat is given in this paper. Showing their application mode and the few clinical effects and pathological findings, the collection of samples becomes very important. For each group of substances tissues or body-fluids are proposed as samples. With modern analytical detection methods residues in food of animal origin can be demonstrated at levels of micrograms/kg. The detection of the above mentioned substances could be supported by a well-aimed sampling and the illegal use can be diminished.

[Lipopigment in the adipose tissue of slaughtered swine]

After feeding rests of slaughtered poultry together with whey, tapioca and residues of stark production to pigs 70% of the slaughtered pigs were refused by the meat inspection because of yellow fat and yellow hair. The occurrence of bile pigment, carotenoids and synthetic colours could be excluded while acid fast pigments were demonstrated in the fat tissue, liver and skeleton muscle. This could be confirmed by the peroxide number, acid number and the content of malondialdehyde and vitamin E. The results were discussed in the view of meat inspection laws.