Comparison of enrichment methods and atmosphere modification procedures for isolating Campylobacter jejuni from foods

Enhanced enrichment and detection of thermotolerant Campylobacter species from water using the Portable Microbe Enrichment Unit and real-time PCR

An enhanced enrichment using the Portable Microbe Enrichment Unit (PMEU) with the microaerobic bubbling of broths was applied for the detection of thermotolerant Campylobacter species from water. This PMEU enrichment was compared with the conventional static enrichment of the international standard ISO 17995:2005. In addition, Campylobacter detection after enrichment using a real-time PCR detection was compared with colony counts. The tests with stressed Campylobacter jejuni cells in drinking water indicated that the PMEU enrichment yielded a significantly higher number of Campylobacter cells in the Bolton broth compared with the conventional static incubation. Application of the real-time PCR technique shortened the Campylobacter detection time. This combination of method modifications can be used for Campylobacter detection from water and adds methodological repertoire for the rapid survey and management of waterborne outbreaks.

Culture media for the isolation of campylobacters

The history of the development of selective media for isolation of campylobacters, including the rationale for choice of selective agents is described. Developments have included modifications to allow incubation at 37 degrees C instead of 42 or 43 degrees C and changes in the types and concentrations of antibiotics in order not to inhibit organisms such as Campylobacter upsaliensis, C. jejuni subsp. doylei and some strains of C. coli and C. lari. When examining foods, plating media originally developed for isolation from faeces are normally used, sometimes after liquid enrichment. Most of the media include ingredients intended to protect campylobacters from the toxic effect of oxygen derivatives. Most commonly used are lysed or defibrinated blood; charcoal; a combination of ferrous sulphate, sodium metabisulphite and sodium pyruvate (FBP); and haemin or haematin. To date no medium includes an indicator system--for instance a pH indicator to show whether colonies produce acid or alkali from particular substrates. The manner in which liquid enrichment media are used has been modified for food samples to avoid inhibitory effects on sublethally damaged cells by toxic components in the formula. This is done by a preliminary period of incubation at reduced temperature and sometimes by delayed addition of antibiotics. Expensive and time-consuming methods have been proposed to achieve a microaerobic atmosphere while using liquid enrichment media. To date there is no generally accepted 'standard' method of isolating campylobacters from food.

Methods for the detection of thermotolerant campylobacters in foods: results of an inter-laboratory study

An inter-laboratory comparison of three methods for the detection of thermotolerant campylobacters is described. One of two proposed by the International Standards Organisation was significantly better for detecting campylobacters in minced chicken skin naturally contaminated at levels of either 2 or 10 cells per 10 g, but involved extensive manipulations not likely to be well received in a busy laboratory. This method yielded 18% false negative results compared with 48-54% for the other two but also gave 8% false positive results. Pre-enrichment of samples with a gradual addition of antibiotics to suppress competing organisms seemed to improve the recovery of campylobacters, as did a non-selective blood agar isolation medium used in combination with a membrane filtration technique.

An appraisal of the efficacy of pre-enrichment for the isolation of Campylobacter jejuni from water and food

Cells of Campylobacter jejuni exposed to heating or freezing were progressively less able to grow at 43 degrees C, particularly on selective media. This influenced the recovery of damaged cells from naturally and artificially contaminated samples. With broth culture the isolation rate could be increased by pre-enrichment in basal or selective media at 37 degrees C for 4 h. With membrane filtration or surface plating techniques the inclusion of agents that quench toxic derivatives of oxygen was more important.

Pathogenic bacteria in milk--a review

Pathogenic bacteria are transmissible to humans through milk and milk products. Recently, attention is focused on milk, cheese, and ice cream contaminated with pathogenic bacteria, viz., Listeria monocytogenes, Yersinia enterocolitica, Campylobacter jejuni, and enteropathogenic Escherichia coli. This review presents information on characteristics of these pathogens and illnesses caused by them.

Methods for detecting and enumerating Campylobacter jejuni and Campylobacter coli in poultry

Methods, media, and biochemical tests for detecting, enumerating, isolating, and identifying Campylobacter jejuni and C. coli in foods are summarized with special consideration of poultry and poultry products. Information is drawn largely from the American Public Health Association Compendium of Methods for the Microbiological Examination of Foods and the US Food and Drug Administration Bacteriological Analytical Manual for Foods. Reference is also made to recently advanced techniques and procedures.

Techniques for the optimum recovery of cold injured Campylobacter jejuni from milk or water

When broth was inoculated with cells of Campylobacter jejuni that had been injured by chilling there was a fall in the viable population of up to 90%. It was greater at 43 degrees than 37 degrees C and in the presence of certain antibiotics and in some cases resulted in a surviving population that was below the minimum inoculum for subsequent growth. A technique of pre-enrichment in non-selective culture broth at 37 degrees C for 2 h before the addition of antibiotics and incubation at 43 degrees C was found to significantly reduce the fall in numbers and to improve the detection of C. jejuni in samples of raw milk and water.

Comparison of enrichment broths for isolation of Campylobacter jejuni

Growth of Campylobacter jejuni was compared in enrichment broths of Doyle and Roman (Appl. Environ. Microbiol. 43:1343-1353, 1982) and Park et al. (C. E. Park, Z. K. Stankiewicz, J. Lovett, and J. Hunt, Can. J. Microbiol. 27:841-842, 1981), as modified by Lovett et al. (J. Lovett, D. W. Francis, and J. M. Hunt, Appl. Environ. Microbiol. 46:459-462, 1983). Inoculated foods used were cream-pudding types, which may be cross-contaminated by improper handling, improper storage of meats prepared simultaneously, or the use of raw milk as an ingredient. Both broths adequately supported growth.

Comparison of methods for isolating Campylobacter jejuni from raw milk

The method of Doyle and Roman (Appl. Environ. Microbiol. 43:1343-1353, 1982) was compared with that of Lovett et al. (Appl. Environ. Microbiol. 46:459-462, 1983) for the ability to recover Campylobacter jejuni strains inoculated into raw milk at a concentration of less than 1 cell per g. The method of Lovett et al. gave significantly greater recovery proportions.