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An 8-year-old boy developed cervical lymphadenitis four months after an injection of dental anaesthetic. Histology of the lymphatic tissue showed a tuberculoid granulomatous reaction with scanty acid-fast bacilli.Mycobacterium cheloneiwas isolated in pure culture (NCTC 10882). The patient showed specific skin hypersensitivity to an extract ofM. chelonei, but not to that ofM. ranae.This is thought to be the first recorded case of lymphadenitis in man caused byM. chelonei; it adds another possibility to be considered in the differential diagnosis of `a lump in the neck'.

It is accepted practice to disinfect microbiological safety cabinets with formaldehyde vapour particularly before such operations as filter changing. For some years at Shrewsbury the method described in PHLS Monograph No 61 in which 200 ml of an equal volume of commercial formalin and water were boiled away in a sealed cabinet and left undisturbed overnight has been used. The directions imply that the extra water is added to raise the humidity and so enhance the lethal effect of the formaldehyde. Unfortunately one of the effects of the extra water is to cause the inside of the cabinet to become wet from condensation. Because condensation on the load and in the chamber of low temperature steam/formaldehyde sterilisers is known to be a common cause of sterilisation failure,2 we tested our cabinet disinfection procedures.Among the many and varied recommendations for disinfecting safety cabinets (Table 1)' 3-6 only one quotes recent supportive experimental details.6 Because of the varied advice and the relative lack of published results we describe the tests we undertook and the results obtained.

SUMMARY A homogeniser (Stomacher 400) which does not damage bacteria has been used to produce an homogenate of spore papers, from which it was possible to make quantitative assessments of viable spores recoverable from such papers before and after exposure to sterilising procedures.After being discouraged for many years, the use of spore papers has now regained favour in the absence of satisfactory physical tests for ethylene oxide and formaldehyde sterilising processes. Such tests depend on the inclusion of suitable standard spore preparations in appropriate test pieces (Line and Pickerill, 1973;Mitchell and Alder, 1975) and their examination for spores remaining viable after exposure to the sterilising process. Customary practice is to transfer the spore paper aseptically to tryptone-soya broth and to incubate at 560C for 14 days. As a method this has the disadvantage that growth, if it occurs, may result from one surviving spore or from many; there will even be occasions when growth will result from contaminants introduced at the time of sampling or culture. However, all such 'positive' results will carry equal weight in the assessment of the sterilising process. What would be preferable, though hitherto considered impossible, would be the quantitative recovery of spores from papers so that not only could the initial loading of the papers be checked but also the survival rates could be determined. Kelsey (1961) stated that in spite of the employment of a variety of the then available disintegrative procedures no quantitative recovery technique could be devised because the spores remained caught up in the filter paper fibres. We here describe a simple method for the quantitative recovery of spores from spore paper in which homogenization (accomplished using a recently introduced machine developed specially for microbiological analyses) is followed by a modification of the surface dropwise counting technique of Miles and Misra (1938).

SYNOPSIS Cooling times for various autoclave loads were recorded using thermocouples. Loads which may be encountered during normal laboratory working require between 17 and 174 minutes to cool to 100°C and up to 260 minutes to cool to 95°C. Such long cooling times had an adverse effect on the nutritive properties of bacteriological culture medium. Observations are made on some factors which influenced the cooling times, and the need for artificially assisted cooling is stressed. Recommendations are given for the safe operation of laboratory autoclaves.