Annual variations and effects of temperature on Legionella spp. and other potential opportunistic pathogens in a bathroom

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Abstract

Opportunistic pathogens (OPs) in drinking water, like Legionella spp., mycobacteria, Pseudomonas aeruginosa and free-living amobae (FLA) are a risk to human health, due to their post-treatment growth in water systems. To assess and manage these risks, it is necessary to understand their variations and environmental conditions for the water routinely used. We sampled premise tap (N cold=26, N hot=26) and shower (N shower=26) waters in a bathroom and compared water temperatures to levels of OPs via qPCR, and identified Legionella spp. by 16S rRNA gene sequencing. The overall occurrence and cell-equivalent quantities (CE L −1) of Mycobacterium spp. were highest (100%, 1.4×10 5), followed by Vermamoeba vermiformis (91%, 493), Legionella spp. (59%, 146), P. aeruginosa (14%, 10), and Acanthamoeba spp. (5%, 6). There were significant variations of OP’s occurrence and quantities, and water temperatures were associated with their variations, especially for Mycobacterium spp., Legionella spp. and V. vermiformis. The peaks observed for Legionella, mainly consisted of L. pneumophila sg1 or L. anisa, occurred in the temperature ranged from 19 to 49°C, while Mycobacterium spp. and V. vermiformis not only co-occurred with Legionella spp. but also trended to increase with increasing temperatures. There were higher densities of Mycobacterium in 1 st than 2 nd draw water samples, indicating their release from faucet/shower head biofilm. Legionella spp. were mostly at detectable levels and mainly consisted of L. pneumophila, L. anisa, L. donaldsonii, L. tunisiensis and an unknown drinking water isolate based on sequence analysis. Results from this study suggested potential health risks caused by opportunistic pathogens when exposed to warm shower water with low chlorine residue and the use of Mycobacterium spp. as an indicator of premise pipe biofilm and the control management of those potential pathogens.

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Microorganisms resistant to free-living amoebae.

G Greub, D Raoult (2004)

Free-living amoebae feed on bacteria, fungi, and algae. However, some microorganisms have evolved to become resistant to these protists. These amoeba-resistant microorganisms include established pathogens, such as Cryptococcus neoformans, Legionella spp., Chlamydophila pneumoniae, Mycobacterium avium, Listeria monocytogenes, Pseudomonas aeruginosa, and Francisella tularensis, and emerging pathogens, such as Bosea spp., Simkania negevensis, Parachlamydia acanthamoebae, and Legionella-like amoebal pathogens. Some of these amoeba-resistant bacteria (ARB) are lytic for their amoebal host, while others are considered endosymbionts, since a stable host-parasite ratio is maintained. Free-living amoebae represent an important reservoir of ARB and may, while encysted, protect the internalized bacteria from chlorine and other biocides. Free-living amoebae may act as a Trojan horse, bringing hidden ARB within the human "Troy," and may produce vesicles filled with ARB, increasing their transmission potential. Free-living amoebae may also play a role in the selection of virulence traits and in adaptation to survival in macrophages. Thus, intra-amoebal growth was found to enhance virulence, and similar mechanisms seem to be implicated in the survival of ARB in response to both amoebae and macrophages. Moreover, free-living amoebae represent a useful tool for the culture of some intracellular bacteria and new bacterial species that might be potential emerging pathogens.

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Opportunistic pathogens enriched in showerhead biofilms.

L. M. Feazel, L. Baumgartner, K L Peterson … (2009)

The environments we humans encounter daily are sources of exposure to diverse microbial communities, some of potential concern to human health. In this study, we used culture-independent technology to investigate the microbial composition of biofilms inside showerheads as ecological assemblages in the human indoor environment. Showers are an important interface for human interaction with microbes through inhalation of aerosols, and showerhead waters have been implicated in disease. Although opportunistic pathogens commonly are cultured from shower facilities, there is little knowledge of either their prevalence or the nature of other microorganisms that may be delivered during shower usage. To determine the composition of showerhead biofilms and waters, we analyzed rRNA gene sequences from 45 showerhead sites around the United States. We find that variable and complex, but specific, microbial assemblages occur inside showerheads. Particularly striking was the finding that sequences representative of non-tuberculous mycobacteria (NTM) and other opportunistic human pathogens are enriched to high levels in many showerhead biofilms, >100-fold above background water contents. We conclude that showerheads may present a significant potential exposure to aerosolized microbes, including documented opportunistic pathogens. The health risk associated with showerhead microbiota needs investigation in persons with compromised immune or pulmonary systems.