Isolation, growth and epidemiology of campylobacter jejuni / coli

A selective blood agar (SBA) and a selective blood enrichment broth (SBEB) containing polymyxin (5,000 iu/l), trimethoprim (10 mg/i), rifampicin (10 mg/l) and cyclohexamide (100 mg/l) have been developed. Results from a comparison with four other media showed that the SBA gave the most isolations and was the most selective. Enrichment culture using SBEB achieved additional isolations. The SBEB was used in a most probable number (MPN) method which detects as few as 10 campylobatters/tOO ml of water. A glass microfibre filtration system was even more sensitive. A blood-free non-selective agar (BFNSA) containing charcoal (0.4%), ferrous sulphate (0.025%) and sodium pyruvate (0.025%) was also developed. These supplements were shown to detoxify rather than enrich the basal medium. A blood-free selective agar (BFSA) was produced by incorporating cephazolin (10 mg/i) and sodium deoxycholate (0.1%). This medium and the SBA gave similar isolation rates from faecal specimens when incubated at 42 0C for 42h but the BFSA was less selective. A blood-free selective enrichment broth (BFSEB) containing sodium metabisulphite (0.05%) gave slightly fewer Campylobacter isolations than the SEES when evaluated with various types of specimens and was also less selective. Maximum isolation rates were achieved by incubating broths at 42 0C and subculturing after 24h and 42h. Growth studies of three Campylobacter strains in four enrichment brothc incubated at 37 0C and 420C produced different growth curves. However, the mean generation time (approx 90 mins) was fairly constant. Studies on the gaseous requirements of campylobacters showed that atmospheres. containing S - 10% 02 and 1 - 10% CO2 facilitate growth. Satisfactory microaerobic conditions were produced by the evacuation-replacement technique and gas generating envelopes but not by candle jars. A biotyping scheme has been developed which differentiates Campylobacter spp. and is useful for epidemiological purposes. Environmental surveys have shown: i) that animal carcasses and equipment in abattoirs were frequently contaminated with campylobacters whilst similar samples from butchers' shops were free from campylobacters; ii) that frozen chickens were the main source of campylobacters in a hospital kitchen and that environmental contamination was uncommon; and iii) river water frequently contains Campylobacter spp., serotypes and biotypes associated with human infection and sewage effluent discharge is an important source of these organisms