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Bovine spongiform encephalopathy (BSE), popularly known as "mad cow disease", was discovered in 1986 and has accounted for the deaths of over 165,000 cattle in the UK (by the end of January, 1997) with about 34,000 (mainly dairy) herds involved. The syndrome in the cow includes changes in posture and temperament, apprehension, and loss of coordination. There are many parallels with scraple in sheep, with similar neuropathological changes in the hindbrain that give it a spongiform appearance under the microscope. The facts have been broadly reviewed in The Lancet in 1990 and 1993, and in much more detail elsewhere. In a two-part article, the first of which appears here, we now summarise recent developments.

One hundred and sixty‐five reference strains and laboratory isolates of Gram negative, non‐sporing, anaerobic bacilli were subjected to a series of simple laboratory tests that were initially selected for their discriminatory value. Conventional biochemical tests, tests of resistance to antibiotics, and tolerance to dyes and bile salts were included. These tests allowed a clear separation of strains into three main groups: Bacteroides fragilis, B. melaninogenicus and Fusobacterium spp. Certain tests were found useful for identifying recognized subspecies of B. fragilis and B. melaninogenicus. A scheme for the identification of unknown laboratory isolates of Gram negative anaerobic bacilli is presented.

Summary: Comparable results were obtained with a commercially available disposable system for the production of H2 and CO2 in an anaerobic jar (the Gaspak system) and with a standard anaerobic jar procedure. Both systems were used with the Baird & Tatlock anaerobic jar and a room temperature catalyst. The test organisms included strict anaerobes such as Clostridium oedematiens type D and Cl. tetani. Comparative tests were also made with Bacteroides species from laboratory stock cultures and with freshly isolated strains of Bacteroides. On occasion, higher recoveries were obtained with the standard system when relatively demanding models were set up but it has limitations, having been developed initially for research purposes. The Gaspak system probably gives more reliable and more reproducible results in a laboratory in which experience with strict anaerobes is limited or sporadic.

SUMMARY. Twenty eight strains of Clostridium dificile, isolated from an outbreak of antibiotic-associated colitis and diarrhoea in an orthopaedic ward and from sporadic cases throughout Sweden, were sent to Edinburgh for immunochemical fingerprinting without information about their origin. EDTA extracts of the organisms were examined by crossed immunoelectrophoresis (CIE), polyacrylamide gel electrophoresis (PAGE) and electroblot transfer. Two patterns were revealed by CIE: group A (18 strains) and group B (10 strains). PAGE and electroblot transfer revealed one major group of 10 strains (group l), six small groups of two or three strains and six strains which were unlike any other strain. The CIE group B and PAGE-electroblot group 1 were identical. Nine of the 10 strains in this group were from patients in the outbreak. These findings indicate that a single strain spread in the orthopaedic ward as a nosocomial infection and that this strain differed from most other strains investigated. The PAGE-electroblot technique should, therefore, greatly aid investigations into the epidemiology of C. dificile infections.

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