Free-living amoebae, Legionella and Mycobacterium in tap water supplied by a municipal drinking water utility in the USA

Abstract

Legionella and Mycobacterium can proliferate within free-living amoebae (FLA) where they are protected from disinfectants at concentrations that can kill bacteria but not protozoa. Despite effective treatment of drinking water, microbes can enter water utility distribution systems (DS) and hence the plumbing within building premises. Additionally, biofilm formation may account for the persistence of microbes in the DS. In the present study a domestic water tap in north-central United States (USA) was sampled in March and September 2007 and analysed for FLA, Legionella and Mycobacterium. Identification of organisms was determined by growth on specific culture media, light and electron microscopy, and amplification of DNA probes specific for each organism. In both the spring and fall samples, amoebae, Legionella and Mycobacterium were detected. However, Acanthamoeba was prominent in the spring sample whereas Vahlkampfia and Naegleria were the amoebae detected in the autumn. Bacterial proliferation in laboratory cultures was noticeably enhanced in the presence of amoebae and biofilms rapidly formed in mixed amoebae and bacteria cultures. It is hypothesized that temperature affected the dynamics of FLA species population structure within the DS and that pathogenic bacteria that proliferate within FLA, which are themselves opportunistic pathogens, pose dual public health risks.

Risk Assessment for the Spread of Serratia marcescens Within Dental-Unit Waterline Systems Using Vermamoeba vermiformis

“…The same source of water, which may supply domestic and clinical service providing premises, will also have nosocomial pathogens and amoebae prevalent within them [18,21,25,34,53], However, Hartmanella (Vermiformis) species are also reported to have been isolated from the throat of humans from as long ago as 1967 [54] implying that the high prevalence of V. vermiformis in the DUWL could also come from humans. This study, identified a clinical isolate of S. marcescens, from one out of 31 DUWL water samples.…”

“…Once inside the amoebal cell, some bacteria will survive or escape the adverse conditions presented by digestive vacuoles, but can also find sanctuary from unfavourable environmental conditions and can multiply [25]. Furthermore, bacteria such as S. aureus may be ingested, but released undigested and intact [39].…”

“…Free living amoebae, Legionella, Mycobacterium and yeast species including Candida, found to reside within DUWLs are sourced from the tap water shared by domestic users and the healthcare providers alike [10,25]. In the context of healthcare, the greatest challenge to overcome is when pathogenic nosocomial bacteria use free living amoebae to support their growth [7,8,31,37,43].…”

Quality Assessment of Drinking Water in Tanta City, Egypt

“…The general trend of tap water of proposed mixed origin to contain the highest number of the isolated bacteria concludes that treatment against microbes in water plants was not highly effective. In addition, microbes can enter water utility distribution systems and biofilm formation may account for the persistence of microbes in the distribution systems [40]. The walls of the pipes in the distribution system provide ideal surfaces for microbial colonization [41].…”

Biofilms Impact on Drinking Water Quality

“…Their presence represents a double threat to human health, being also related to amoeba-resisting bacteria, such as Legionella spp. and Mycobacterium spp., which proliferate in protozoa thus increasing the probability of causing diseases in humans (Marciano-Cabral et al, 2010). Some protozoa, for example Giardia spp.…”