Colonization of hospital water systems by legionellae, mycobacteria and other heterotrophic bacteria potentially hazardous to risk group patients

Abstract

Occurrences of legionellae and nontuberculous mycobacteria were followed in water systems of a tertiary care hospital where nosocomial infections due to the two genera had been verified. The aim was to examine whether their occurrence in the circulating hot water can be controlled by addition of a heat-shock unit in the circulation system, and by intensified cleaning of the tap and shower heads. One hot water system examined had an inbuilt heat-shock system causing a temporary increase of temperature to 80 degrees C, the other was an ordinary system (60 degrees C). The heat-shock unit decreased legionella colony counts in the circulating hot water (mean 35 cfu/l) compared to the ordinary system (mean 3.6 x 10(3) cfu/l). Mycobacteria constantly present in the incoming cold water (mean 260 cfu/l) were never isolated from the circulating hot water. Water sampled at peripheral sites such as taps and showers contained higher concentrations of legionellae, mycobacteria, and mesophilic and Gram-negative heterotrophs than the circulating waters. The shower water samples contained the highest bacterial loads. The results indicate the need to develop more efficient prevention methods than the ones presently used. Prevention of mycobacteria should also be extended to incoming cold water.

Risk Factors for Contamination of Hotel Water Distribution Systems by Legionella Species

“…other than L. pneumophila and of L. pneumophila serogroups 2 to 14 and positively with counts of L. pneumophila serogroup 1. These findings confirm other reports, which indicated a positive association of L. pneumophila with pH (10,11,12). The differences in distribution of species according to water characteristics confirm the hypothesis of (4,5,11).…”

Environmental culturing for Legionella: Can we build a better mouse trap?

“…Specific localized problems that can affect Legionella colonization of fixtures include moderate temperature, presence of mixing valves in electronic/sensor type fixtures, and lack of use. [11][12][13] Our experience indicates that increasing the recirculating hot water temperature to 1408F will restrict Legionella growth in the recirculating line; however, Legionella will be unaffected at the distal outlets, and these outlets will remain extensively colonized. Therefore, relying solely on the testing of the recirculating hot water line for assessing the status of Legionella colonization within a complex water distribution system may be misleading.…”

Fluorescence In Situ Hybridization Using Peptide Nucleic Acid Probes for Rapid Detection of Mycobacterium avium subsp. avium and Mycobacterium avium subsp. paratuberculosis in Potable-Water Biofilms

“…The water was filtered through a membrane filter (Ultipor, NR047100, 0.2-m pore size; Pall Corp.). Retained bacteria were detached from the filter by shaking with 6 ml of the original water filtrate in the presence of glass beads, as described by Kusnetsov et al (21). An aliquot (25 l) of the concentrated bacterial suspension was pipetted onto a Teflon-coated diagnostic microscope slide (Erie Scientific Company, Portsmouth, NH) and hybridized as described above.…”