Legionella in health care institutions : a case study in Malta.

Abstract

An evaluation was made of the prevalence of Legionella species in the water systems of selected health institutions in Malta. In addition, the possible association of Legionella isolates with physical parameters and bacterial contamination (aerobic colony counts) was also studied. Detection and enumeration of Legionella organisms was performed according to the British national standard W 12, formulated by the Health Protection Agency (U.K.). Before the actual study was carried out, the chosen method was validated and quality control checks carried out on the culture media used. Analysis of 361 samples, sourced from hospitals (103 samples; 28%), polyclinics (13 samples; 4%), homes for the elderly (159 samples; 44%) and other institutions (86 samples; 24%) were processed. Legionella spp. was detected in 40% of the total amount of samples tested. L. pneumophila SG 1 was isolated from 21% of the water samples, L. pneumophila SG 2-14 from 17% of samples and Legionella spp. was found in 6% of water samples tested. The highest colonization was found in hospitals (50%) followed by homes for the elderly (45%), polyclinics (39%) and other institutions (21 %). Concentrations of Legionella in the water sampled from institutions exceeded the threshold level of >/ 10^4 cfu/L in 5% of the samples, which is considered to be at a high risk for an outbreak of Legionnaires' disease. It was concluded that the colonisation of Legionella in the water systems of the health institutions studied was high and therefore required the implementation of a series of

measures to bring it under control. One recommendation was the introduction or review of a Legionella risk management plan in the institutions. Another part of the project included the publishing of a CD-ROM presentation which could serve as an educational tool for personnel working in these institutions.