Introduction: Wearing hearing aid earmoulds has been implicated as a predisposing factor in the development of chronic otitis externa. Audiologists come into contact with a large number of hearing aid earmoulds and these could potentially harbour pathogenic micro-organisms, with the risk of subsequent cross infection. Cleaning with dilute alcohol is widely used in an attempt to break the chain of infection.

Objective: To determine the presence and nature of microbial flora on hearing aid earmoulds and the efficacy of cleaning methods used to prevent cross infection.

Setting: Secondary health care within the audiology department of Addenbrooke's Hospital, Cambridge, UK.

Design: A prospective, observational study.

Methods: Hearing aid earmoulds were swabbed before and after cleaning. Samples were cultured to determine qualitatively and quantitatively the microbiological flora present before and after cleaning.

Results: Twenty out of 21 (95 per cent) earmoulds had microbes present and, of these, 19/20 (95 per cent) had a polymicrobial profile. Coagulase negative staphylococci and diphtheroids were the most frequent microbial isolates, but pathogenic bacteria and fungi were also demonstrated on earmoulds both before and after cleaning.

Conclusions: The polymicrobial flora, including recognized pathogens, that colonizes earmoulds may lead to chronic otitis externa. Cleaning with 70 per cent alcohol solution was ineffective, in particular for pathogenic fungi on earmoulds.

Nosocomial infections are an important cause of morbidity and contaminated equipment may contribute to this. There has been little work concerning contamination of non-disposable equipment in Otolaryngology. This study investigates the efficacy of the cleaning regimen for non-disposable instruments in an Otolaryngology out-patients clinic. Instruments were swabbed before each clinic, when they had been autoclaved, then after use on patients, when they had been washed with detergent and chlorhexidine. Swabs of 86 instruments were cultured using standardized microbiological techniques. Fifteen instruments (17 per cent) were contaminated, most with coagulase negative staphylococci. Two specimens of Micrococcus luteus were cultured and one each of Pseudomonas aeruginosa, Acinetobacter lwoffii and Aureobacterium spp. Micrococcus luteus and coagulase negative staphylococci may represent skin contaminants, but Aureobacterium spp. and Acinetobacter lwoffii can be sources of nosocomial infection. Pseudomonas aeruginosa is a potentially serious pathogen and is implicated in the aetiology of otitis externa. These findings question the efficacy of the current cleaning techniques.

The failure of anaesthetic equipment as a result of maintenance is extremely rare. The ingress of water into the flowmeters of an anaesthetic machine from the piped medical air supply is reported and is possibly unique. The piped medical air supply was open to the atmosphere during maintenance. Water condensed in the gas pipeline and this was not noticed during subsequent testing. Water was seen leaking from the orthopaedic air tools used for surgery but was assumed to be from the autoclaving process. Later the same day, when medical air from the piped source was used as part of the gas mixture for a general anaesthetic, water was seen filling the barrel of the flowmeter air control valve. This could have had far-reaching and dangerous consequences for the patient, which were fortunately averted.