Chapter 56 : Legionella Detection from South African Cooling Water Systems

Abstract:

Large numbers of legionellae in water distribution systems present a potentially serious health risk to workers and the general public. Sporadic infections are diagnosed with increasing frequency, clearly illustrating the importance of appropriate methods for Legionella detection. A Legionella Action Group formed in 1995, took up a study as part of an initiative to provide South African laboratories and industries with guidelines for the most appropriate culturing method for the environment, and with information on the prevalence of Legionella in industrial waters. Two of the internationally accepted culture methods and a locally developed adaptation of the most probable number (MPN) method, used by some laboratories in South Africa, were evaluated. The International Standard (ISO) method is widely accepted as a standard and used by some laboratories in South Africa. The quantitative MPN method has been adapted for enumeration of Legionella in water samples by South African workers. Single colonies with the typical groundglass appearance of legionellae were tested for cysteine dependence by inoculating buffered charcoal-yeast extract (BCYE) agar and nutrient agar and incubating these until growth was observed on the BCYE agar, as indicated in the ISO and Australian Standard (AS) methods.