Pseudomonas aeruginosa and cyanide production

Abstract

Infection and subsequent chronic infection of the cystic fibrosis (CF) lung with organisms such as Pseudomonas aeruginosa probably occurs at an early stage in the life of a child suffering from CF. Clinicians worldwide are eager to isolate the organism as early as possible in an attempt to treat the patient before any permanent damage occurs and hopefully to eliminate the organism completely from the respiratory tract for many years. Young children are usually unable to expectorate sputum for microbiological analysis and cough swabs are relatively insensitive. Induced sputum techniques are generally not well tolerated in children and bronchoscopic manoeuvres are very invasive, requiring a general anaesthetic. There has, therefore, been interest in discovering whether there are any surrogate markers which could be helpful as a specific indication of the presence of P. aeruginosa . It has been postulated that cyanide could be one such compound. P. aeruginosa is one of a limited number of organisms which can synthesise cyanide 1. Synthesis occurs by the oxidative decarboxylation of glycine by a hydrogen cyanide synthase enzyme. This process also produces four electrons and four hydrogen ions per glycine molecule. Cyanide synthesis by P. aeruginosa occurs under microaerobic (O2<5%) conditions but is inactivated under both atmospheric oxygen and strictly anaerobic conditions 1, 2. Cyanide production by P. aeruginosa is maximised at temperatures between 34°C and 37°C 3. Studies which have investigated cyanogenesis in relation to P. aeruginosa using liquid or solid samples have assayed cyanide concentrations …