Impact of Chlorine and Chloramine on the Detection and Quantification of Legionella pneumophila and Mycobacterium Species

Abstract

Potable water can be a source of transmission for legionellosis and nontuberculous mycobacterium (NTM) infections and diseases. Legionellosis is caused largely by Legionella pneumophila, specifically serogroup 1 (Sg1). Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium abscessus are three leading species associated with pulmonary NTM disease. The estimated rates of these diseases are increasing in the United States, and the cost of treatment is high. Therefore, a national assessment of water disinfection efficacy for these pathogens was needed. The disinfectant type and total chlorine residual (TClR) were investigated to understand their influence on the detection and concentrations of the five pathogens in potable water. Samples (n = 358) were collected from point-of-use taps (cold or hot) from locations across the United States served by public water utilities that disinfected with chlorine or chloramine. The bacteria were detected and quantified using specific primer and probe quantitative-PCR (qPCR) methods. The total chlorine residual was measured spectrophotometrically. Chlorine was the more potent disinfectant for controlling the three mycobacterial species. Chloramine was effective at controlling L. pneumophila and Sg1. Plotting the TClR associated with positive microbial detection showed that an upward TClR adjustment could reduce the bacterial count in chlorinated water but was not as effective for chloramine. Each species of bacteria responded differently to the disinfection type, concentration, and temperature. There was no unifying condition among the water characteristics studied that achieved microbial control for all. This information will help guide disinfectant decisions aimed at reducing occurrences of these pathogens at consumer taps and as related to the disinfectant type and TClR. IMPORTANCE The primary purpose of tap water disinfection is to control the presence of microbes. This study evaluated the role of disinfectant choice on the presence at the tap of L. pneumophila, its Sg1 serogroup, and three species of mycobacteria in tap water samples collected at points of human exposure at locations across the United States. The study demonstrates that microbial survival varies based on the microbial species, disinfectant, and TClR.

Evaluation of a new culture medium for isolation of nontuberculous mycobacteria from environmental water samples

“…Opportunistic pathogens, such as NTM species, have adapted to grow and reside in potable premise plumbing systems and can even be selected for by common municipal disinfection methods including monochloramine treatment [ 17 , 18 ]. Although there are many different methods for isolating NTM from both clinical and environmental samples, none of these methods offers ideal selectivity even with the laborious undertaking of decontamination steps.…”

“…mucogenicum , and M . phocaicum [ 18 , 20 , 21 ]. These organisms, and many others, were also recovered in our study.…”

Flushing of stagnant premise water systems after the COVID-19 shutdown can reduce infection risk by Legionella and Mycobacterium spp

“…Legionellae have been observed in drinking water distribution networks and premise plumbing when there is little or no residual free chlorine (HOCl) but largely absent otherwise, especially when residual chloramine is maintained in the water (as monochloramine, NH 2 Cl). 9-16 Conversely, NTM are known for their resistance to disinfectants and other antimicrobial agents, which enables their persistence in distribution networks containing chlorine or chloramine. 16-19…”

“…9-16 Conversely, NTM are known for their resistance to disinfectants and other antimicrobial agents, which enables their persistence in distribution networks containing chlorine or chloramine. 16-19…”

Impact of coagulation–ultrafiltration on long-term pipe biofilm dynamics in a full-scale chloraminated drinking water distribution system

“…57 Mycobacterium is known to be resistant to many disinfection methods, 58 including ultraviolet (UV) disinfection, 59 which the DWTP in this study is using. Legionella has been detected in pipe biofilms 60 and also in bulk water both in chlorinated and chloraminated DWDSs, 56 due in part to their ability to live within protozoa. 61 Dynamics in Mycobacterium and Legionellales showed elevated relative abundances during summer ( Fig.…”