Isolation of Campylobacter spp. from pigeon feces by a combined enrichment-filtration technique

Use of cellulose filters to isolate Campylobacter spp. from naturally contaminated retail broiler meat

Membrane filtration has been used to isolate Campylobacter spp. from feces, although approximately 5 log CFU/g must be present in the sample. Few studies have attempted to use filter membranes for the isolation of Campylobacter from foods. We investigated the minimum number of thermotolerant Campylobacter cells that pass through cellulose filters, the effect of different cell conditions on the rate of passage, and the minimum number of cells that could pass the filters from enriched broiler meat naturally contaminated with Campylobacter spp. Cellulose filters with 0.65-microm pore sizes retained fewer cells and were more effective than filters with 0.45-microm pore sizes. Scanning electron microscopy revealed that 15 min of contact of the filters with agar plates allowed for the passage of most bacteria. The minimum number of bacteria required to pass through the filters was contingent on cell conditions; nonmotile cells were retained more than motile cells (P < 0.05). The minimum number of motile bacteria from 24-h cultures and centrifuged cells were 2.2 and 2.1 log CFU, respectively, while the number of coccoid and nonmotile (flaA/B(-) mutant) cells were 4.1 and 3.4 log CFU, respectively. Broiler meat samples enriched in Bolton's broth supplemented with 5% lysed blood showed that approximately 1.7 log CFU of Campylobacter can be filtered to pure colonies on agar plates. These results demonstrate that the motility of the bacteria influences passage through cellulose filters and that 0.65-mum-pore-size filters on agar plates help obtain pure Campylobacter colonies from enriched food samples.

The use of a combined enrichment-filtration technique for the isolation of Campylobacter spp. from clinical samples

A combined non-selective enrichment-filtration technique was investigated for the isolation of Campylobacter spp. from clinical samples. In total, 479 samples were tested by direct culture, enrichment subculture and enrichment-filtration. The enrichment-filtration technique was used with both selective and non-selective media. Direct culture and enrichment subculture yielded 13 and seven isolates, respectively, while enrichment-filtration yielded 18 and 14 isolates on selective and non-selective agar, respectively. Thus, the combination of enrichment-filtration with selective agar produced a 38.5% increase in the number of isolates (p <0.05). All isolates were identified as Campylobacter jejuni.

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.

Prevalence of Campylobacter jejuni in ranch mink at pelting: Cultural, serological, and histological evidence of infection

This survey of 500 mink on three Wisconsin ranches at pelting gives an estimate of the prevalence of Campylobacter jejuni in the feces of clinically normal animals. On ranches 1 and 2, which used wet feed, C. jejuni was isolated by colon content culture from 7% and 32% of mink one year, and 43% and 13% the next year; the 200 bile samples tested were culture-negative. On ranch 3, which fed a pelleted ration, the organism was never isolated. Among culture-positive mink tested, 22 of 55 had bacterial agglutination serum titers to homologous and/or heterologous Campylobacter isolates from the ranch of origin. Four of 23 culture-negative animals tested had titers. No histological evidence of inflammatory changes in the lower ileum and/or colon was found, although Campylobacter-like organisms were rarely seen in silver-stained sections from both culture-negative and culture-positive animals. We conclude that the presence of C. jejuni in the mink gut does not necessarily indicate a role in gastrointestinal disease.