Occurrence revisited: Mycobacterium avium and Mycobacterium intracellulare in potable water in the USA.

Nontuberculous mycobacterium (NTM) infections are increasing in the USA and have a high cost burden associated with treatment. Thus, it is necessary to understand what changes could be contributing to this increase in NTM disease rate. Water samples from 40 sites were collected from around the USA. They represented three water types: groundwater disinfected with chlorine and surface water disinfected with chlorine or monochloramine. Two methods, culture and qPCR, were used to measure M. avium and M. intracellulare. Heterotrophic bacteria and NTM counts were also measured. M. avium and M. intracellulare were molecularly detected in 25% (73/292) and 35% (102/292) of samples. The mean concentrations of M. avium and M. intracellulare were 2.8 × 103 and 4.0 × 103 genomic units (GU) L-1. The Northeast sites had the highest sample positively rate for both M. avium and M. intracellulare. The highest NTM counts and M. avium concentrations were observed in the surface water treated with chloramine. Geographic location and source water/disinfectant type were observed to significantly influence M. avium and M. intracellulare occurrence rates. These studies can help improve public health risk management by balancing disinfectant treatments and diverse microbial loads in drinking water. KEY POINTS: • M. avium (MA) culture rate increased significantly: 1% (1999) to 13%. • Culture versus qPCR method: 13% vs 31% for MA and 6% vs 35% for MI. • The results of each method type tell two different stories of MA and MI occurrence.

Epidemiological risk factors and the geographical distribution of eight Mycobacterium species.

BACKGROUND: Nontuberculous mycobacteria (NTM) are environmental bacterium that may cause and/or compound respiratory diseases in humans. There are over a hundred NTM species with varying pathogenicity's Therefore, it is necessary to characterize the populations at risk for each species. METHODS: Demographic (age, sex, and state of residence) and microbiological data from 2014 were extracted from Mississippi, Missouri, and Ohio disease surveillance systems. NTM species with > 50 reports were included in the analysis. Patient sex, age, and incidence rates were generated for each of the following NTM species: M. abscessus, M. avium complex (MAC), M. chelonae, M. fortuitum, M. gordonae, M. kansasii, M. mucogenicum, and M. peregrinum. RESULTS: Analysis by sex showed that M. chelonae,M. fortuitum, M. gordonae,and M. kansasii had significantly higher rates in males than females. Age was not associated with patient rates for several specific NTM species e.g., M. chelonae. Mississippi had the highest patient' rates for M. avium, M. gordonae, M. kansasii, and M. chelonae. Ohio had the highest patient' rates for M. abscessus, M. mucogenicum, and M. peregrinum. The highest patient's rate for M. fortuitum was observed in Missouri. CONCLUSION: This study showed that NTM infection occurred more frequently in males. The highest rates were observed in Mississippi for most of the NTMs studied. Age was not a strong risk factor for some of the NTM species.

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

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.

Increasing nontuberculous mycobacteria reporting rates and species diversity identified in clinical laboratory reports.

BACKGROUND: Nontuberculous Mycobacteria (NTM) are environmental microorganisms that can affect human health. A 2009-2010 occurrence survey of NTM in potable tap water samples indicated an increased recovery rate for many clinically significant species such as M. avium (30%) and M. abscessus (12%). To determine if these trends by species were mirrored in human infections, isolation rates of NTM species identified in clinical laboratory reports from four states were evaluated. METHOD: Clinical laboratory reports from the Mississippi, Missouri, Ohio, and Wisconsin Health Departments were used to investigate the species of NTM isolated from human specimens in 2014. The NTM positive specimen reports were tabulated for each species and complex/group. The number of reports by month were used to investigate seasonal trends. The 2014 isolation rates were compared to historic values to examine longitudinal trends. RESULTS: The positive rate of NTM specimens increased from 8.2 per 100,000 persons in 1994 to 16 per 100,000 persons in 2014 (or 13.3 per 100,000 after excluding Mycobacterium gordonae). Changes in NTM diversity were observed in complex/groups known to be clinically significant. Between 1994 and 2014 the rate implicating M. abscesses-chelonae group and M. avium complex increased by 322 and 149%, respectively. CONCLUSIONS: Based on public health data supplied by the four State's Health Departments and the 2014 U.S. population, 50,976 positive NTM specimen reports per year were projected for the nation; serving as an indicator for the national potential disease burden that year.

Increased Frequency of Nontuberculous Mycobacteria Detection at Potable Water Taps within the United States.

Nontuberculous mycobacteria (NTMs) are environmental microorganisms that can cause infections in humans, primarily in the lung and soft tissue. The prevalence of NTM-associated diseases is increasing in the United States. Exposure to NTMs occurs primarily through human interactions with water (especially aerosolized). Potable water from sites across the U.S. was collected to investigate the presence of NTM. Water from 68 taps was sampled 4 times over the course of 2 years. In total, 272 water samples were examined for NTM using a membrane filtration, culture method. Identification of NTM isolates was accomplished by polymerase chain reaction (PCR) amplification of the 16S rRNA and hsp65 genes. NTMs were detected in 78% of the water samples. The NTM species detected most frequently were: Mycobacterium mucogenicum (52%), Mycobacterium avium (30%), and Mycobacterium gordonae (25%). Of the taps that were repeatedly positive for NTMs, the species M. avium, M. mucogenicum, and Mycobacterium abscessus were found to persist most frequently. This study also observed statistically significant higher levels of NTM in chloraminated water than in chlorinated water.

Widespread molecular detection of Legionella pneumophila Serogroup 1 in cold water taps across the United States.

In the United States, 6,868 cases of legionellosis were reported to the Center for Disease Control and Prevention in 2009-2010. Of these reports, it is estimated that 84% are caused by the microorganism Legionella pneumophila Serogroup (Sg) 1. Legionella spp. have been isolated and recovered from a variety of natural freshwater environments. Human exposure to L. pneumophila Sg1 may occur from aerosolization and subsequent inhalation of household and facility water. In this study, two primer/probe sets (one able to detect L. pneumophila and the other L. pneumophila Sg1) were determined to be highly sensitive and selective for their respective targets. Over 272 water samples, collected in 2009 and 2010 from 68 public and private water taps across the United States, were analyzed using the two qPCR assays to evaluate the incidence of L. pneumophila Sg1. Nearly half of the taps showed the presence of L. pneumophila Sg1 in one sampling event, and 16% of taps were positive in more than one sampling event. This study is the first United States survey to document the occurrence and colonization of L. pneumophila Sg1 in cold water delivered from point of use taps.

Building size and disinfectant type influence the detection and concentration of Mycobacterium spp. in hot water plumbing.

The number of nontuberculous mycobacteria (NTM) lung disease cases is increasing in the United States (US). This respiratory disease is primarily caused by three NTM species: Mycobacterium avium, M. intracellulare, and M. abscessus. Since disease transmission could occur through water aerosolization, this study investigated these three species' occurrence (sporadic and persistent) in hot water samples collected from residences (n = 70) and office buildings (n = 30) across the US. A longitudinal survey design was used. Three quantitative Polymerase Chain Reaction (qPCR) assays were used to measure the mycobacterial species in the water samples. Additionally, the water's disinfectant residual was measured. A structure's age and square footage were evaluated to predict mycobacterial contamination. Also, the seasonal occurrence of each species was assessed by structure type. Residences had a 43 % (30/70), and office buildings had a 77 % (23/30) detection frequency of one or more Mycobacterium spp. in their hot water. The age of the structure influenced M. intracellulare detection frequency but not M. avium and M. abscessus. The structure's square footage affected M. avium and M. intracellulare detection frequency but not M. abscessus. In chlorinated water, M. intracellulare was detected 1.4× more often in office buildings' hot water than in chloraminated water. In chloraminated water, the Mycobacterium spp. were detected 2-2.5× more often in residences, while M. avium and M. abscessus were detected 1.5-2.3× more often in office buildings, compared to chlorinated water. Each Mycobacterium spp. had a different trend associated with the type of structure and disinfectant. Further research is needed to better understand NTM occurrence in the built environment to improve public health.

Hartmannella vermiformis inhibition of Legionella pneumophila cultivability.

Hartmannella vermiformis and Acanthamoeba polyphaga are frequently isolated from drinking water and permissive to Legionella pneumophila parasitization. In this study, extracellular factor(s) produced by H. vermiformis and A. polyphaga were assessed for their effects on cultivability of L. pneumophila. Page's amoeba saline (PAS) was used as an encystment medium for H. vermiformis and A. polyphaga monolayers, and the culture supernatants (HvS and ApS, respectively) were assessed against L. pneumophila growth. Compared to PAS and ApS, HvS significantly inhibited L. pneumophila strain Philadelphia-1 (Ph-1) cultivability by 3 log(10) colony forming unit (CFU) mL(-1) after 3 days of exposure compared to <0.5 log(10) CFU mL(-1) reduction of strain Lp02 (P < 0.001). Flow cytometric analysis revealed changes in the percentage and cultivability of three bacterial subpopulations: intact/slightly damaged membrane (ISM), undefined membrane status (UD), and mixed type (MT). After 3 days of HvS exposure, the MT subpopulation decreased significantly (31.6 vs 67.2 %, respectively, P < 0.001), while the ISM and UD subpopulations increased (+26.7 and +6.9 %, respectively) with the ISM subpopulation appearing as viable but nonculturable (VBNC) cells. HvS was separated into two fractions based on molecular weight, with more than 99 % of the L. pneumophila inhibition arising from the <5 kDa fraction (P < 0.001). Liquid chromatography indicated the inhibitory molecule(s) are likely polar and elute from a Novapak C18 column between 6 and 15 min. These results demonstrate that H. vermiformis is capable of extracellular modulation of L. pneumophila cultivability and probably promote the VBNC state for this bacterium.

Water quality influences Legionella pneumophila determination.

Legionellosis is a respiratory disease of public health concern. The bacterium Legionella pneumophila is the etiologic agent responsible for >90% of legionellosis cases in the United States. Legionellosis transmission primarily occurs through the inhalation or aspiration of contaminated water aerosols or droplets. Therefore, a thorough understanding of L. pneumophila detection methods and their performance in various water quality conditions is needed to develop preventive measures. Two hundred and nine potable water samples were collected from taps in buildings across the United States. L. pneumophila was determined using three culture methods: Buffered Charcoal Yeast Extract (BCYE) culture with Matrix-assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) identification, Legiolert® 10- and 100-mL tests, and one molecular method: quantitative Polymerase Chain Reaction (qPCR) assay. Culture and molecular positive results were confirmed by secondary testing including MALDI-MS. Eight water quality variables were studied, including source water type, secondary disinfectant, total chlorine residual, heterotrophic bacteria, total organic carbon (TOC), pH, water hardness, cold- and hot-water lines. The eight water quality variables were segmented into 28 categories, based on scale and ranges, and method performance was evaluated in each of these categories. Additionally, a Legionella genus qPCR assay was used to determine the water quality variables that promote or hinder Legionella spp. occurrence. L. pneumophila detection frequency ranged from 2 to 22% across the methods tested. Method performance parameters of sensitivity, specificity, positive and negative predictive values, and accuracy were >94% for the qPCR method but ranged from 9 to 100% for the culture methods. Water quality influenced L. pneumophila determination by culture and qPCR methods. L. pneumophila qPCR detection frequencies positively correlated with TOC and heterotrophic bacterial counts. The source water-disinfectant combination influenced the proportion of Legionella spp. that is L. pneumophila. Water quality influences L. pneumophila determination. To accurately detect L. pneumophila, method selection should consider the water quality in addition to the purpose of testing (general environmental monitoring versus disease-associated investigations).

Environmental risk of nontuberculous mycobacterial infection: Strategies for advancing methodology.

The National Institute of Allergy and Infectious Diseases organized a symposium in June 2022, to facilitate discussion of the environmental risks for nontuberculous mycobacteria exposure and disease. The expert researchers presented recent studies and identified numerous research gaps. This report summarizes the discussion and identifies six major areas of future research related to culture-based and culture independent laboratory methods, alternate culture media and culturing conditions, frameworks for standardized laboratory methods, improved environmental sampling strategies, validation of exposure measures, and availability of high-quality spatiotemporal data.

Hot water plumbing in residences and office buildings have distinctive risk of Legionella pneumophila contamination.

AIM: To observe how Legionella pneumophila, the causative agent for legionellosis, can transmit through the hot water plumbing of residences and office buildings. METHOD AND RESULTS: Using qPCR, L. pneumophila and L. pneumophila Serogroup (Sg)1 were measured in hot water samples collected from 100 structures, consisting of 70 residences and 30 office buildings. The hot water samples collected from office buildings had a higher L. pneumophila detection frequency of 53% (16/30) than residences, with a 103 GU/L (median) concentration. An office building's age was not a statistically significant predictor of contamination, but its area (>100,000 sq. ft.) was, P = <0.001. Hot water samples collected at residences had a lower L. pneumophila detection frequency of 36% (25/70) than office buildings, with a 100 GU/L (median) concentration. A residence's age was a significant predictor of contamination, P = 0.009, but not its area. The water's secondary disinfectant type did not affect L. pneumophila detection frequency nor its concentration in residences, but the secondary disinfectant type did affect results in office buildings. Legionella pneumophila's highest detection frequencies were in samples collected in March-August for office buildings and in June-November for residences. CONCLUSION: This study revealed that the built environment influences L. pneumophila transport and fate. Residential plumbing could be a potential "conduit" for L. pneumophila exposure from a source upstream of the hot water environment. Both old and newly built office buildings had an equal probability of L. pneumophila contamination. Legionella-related remediation efforts in office buildings (that contain commercial functions only) might not significantly improve a community's public health.

Quantification of Legionella pneumophila by qPCR and culture in tap water with different concentrations of residual disinfectants and heterotrophic bacteria.

Legionellosis prevalence is increasing in the United States. This disease is caused primarily by the bacterium Legionella pneumophila found in water and transmitted by aerosol inhalation. This pathogen has a slow growth rate and can "hide" in amoeba, making it difficult to monitor by the traditional culture method on selective media. Tap water samples (n = 358) collected across the United States were tested for L. pneumophila by both culture and quantitative Polymerase Chain Reaction (qPCR). The presence of other bacteria was quantified by heterotrophic plate counts (HPC). Residual disinfectant concentrations (free chlorine or monochloramine) were measured in all samples. Legionella pneumophila had the highest prevalence and concentration in the chlorinated water samples that had a free­chlorine value of less than 0.2 mg Cl2/L. In total, 24% (87/358) of the samples were positive for L. pneumophila either by qPCR or 3% (11/358) were positive by culture. In chloramine-treated samples, L. pneumophila was detected by qPCR in 21% (31/148) and 1% (2/148) by culture, despite a high monochloramine residual >1 mg Cl2/L. Despite the presence of a high disinfectant residual (>1 mg Cl2/L), HPC counts were substantial. This study indicates that both culture and qPCR methods have limitations when predicting a potential risk for disease associated with L. pneumophila in tap water. Measuring disinfectant residuals and quantifying HPC in water samples may be useful adjunct parameters for reducing Legionellosis' risk from public water supplies at high-risk locations.

Chloramine Concentrations within Distribution Systems and Their Effect on Heterotrophic Bacteria, Mycobacterial Species, and Disinfection Byproducts.

Chloramine is a secondary disinfectant used to maintain microbial control throughout public water distribution systems. This study investigated the relationship between chloramine concentration, heterotrophic bacteria, and specific Mycobacterium species. Sixty-four water samples were collected at four locations within the utility's distribution network on four occasions. Water samples were analyzed for total chlorine and monochloramine. Traditional culture methods were applied for heterotrophic bacteria and nontuberculous mycobacteria (NTM), and specific quantitative polymerase chain reaction (qPCR) assays were used to detect and quantify Mycobacterium avium, M. intracellulare, and M. abscessus. Total chlorine and monochloramine concentrations decreased between the distribution entry point (4.7 mg/L and 3.4 mg/L as Cl2, respectively) to the maximum residence time location (1.7 mg/L and 1.1 mg/L as Cl2, respectively). Results showed that heterotrophic bacteria and NTM counts increased by two logs as the water reached the average residence time (ART) location. Microbiological detection frequencies among all samples were: 86% NTMs, 66% heterotrophic bacteria, 64% M. abscessus, 48% M. intracellulare, and 2% M. avium. This study shows that heterotrophic bacteria and NTM are weakly correlated with disinfectant residual concentration, R2=0.18 and R2=0.04, respectively. Considering that specific NTMs have significant human health effects, these data fill a critical knowledge gap regarding chloramine's impact on heterotrophic bacteria and Mycobacterial species survival within public drinking water distribution systems.

Detection of Mycobacterium avium subsp. paratuberculosis in drinking water and biofilms by quantitative PCR.

It has been suggested that Mycobacterium avium subspecies paratuberculosis has a role in Crohn's disease. The organism may be acquired but is difficult to culture from the environment. We describe a quantitative PCR (qPCR) method to detect M. avium subsp. paratuberculosis in drinking water and the results of its application to drinking water and faucet biofilm samples collected in the United States.

Human serum IgE reacts with a Metarhizium anisopliae fungal catalase.

BACKGROUND: Previous studies have demonstrated that Metarhizium anisopliae extract can induce responses characteristic of human allergic asthma in a mouse model. The study objectives were (1) to identify and characterize the M. anisopliae mycelia extract (MYC) proteins that are recognized by mouse serum IgE, (2) to determine if human serum IgE reacts with these proteins, and (3) to determine if these IgE-reactive proteins are found in other fungi. METHODS: Asthmatic human serum IgE, M. anisopliae crude antigen (MACA) immunized mouse serum IgE, and anti-catalase antibodies were used to probe one- and two-dimensional gel electrophoresis blots of MYC. RESULTS: Mass spectrometry analysis identified catalase as a mouse IgE-reactive protein. This identification was confirmed by assaying catalase activity in the extract and extract immunoblots probed with anti-catalase antibody. Six adult asthmatic sera contained IgE, but not IgG, that was reactive with mycelia extract proteins. A similar protein profile was seen when blots were probed with either mouse anti-MACA IgE or anti-bovine liver catalase antibodies. Furthermore, these mouse anti-MACA and anti-catalase antibodies were cross-reactive with other mold extracts (skin prick testing mix) and Aspergillus niger catalase. CONCLUSIONS: Some human asthmatics have developed IgE that reacts with an M. anisopliae catalase, most likely due to cross-reactivity (minimal IgG development). The cross-reactivity among fungal catalases suggests that IgE-reactive catalase might be useful for exposure assessment. Additionally, the similarity of protein profiles visualized with both human and mouse serum IgE suggests that allergy hazard identification can be facilitated using a mouse model.

Absorption of strontium by foods prepared in drinking water.

Strontium (Sr) is a natural element, ubiquitous in the environment and known to occur in water, food, air, and soils. Strontium is present in media as a salt or an ionized divalent cation. The Sr ion (dissociated) is toxicokinetically important because it is easily absorbed into systemic circulation when inhaled with particulates or ingested with water or foods. Dietary exposure can be influenced by using tap water containing dissolved Sr in food preparation. Research was conducted to determine the amount of Sr transferred from water to individual foods during preparation. Strontium transferred to broccoli, lentils, and spaghetti at all levels tested (1.5, 10, and 50 mg/L) as evidenced by the residual Sr in the pour-off water following food preparation (33-64%). The data from the cooking study support the hypothesis that cooking of foods with water containing Sr adds to total dietary exposure. This information can inform the determination of the relative source contribution (RSC) that is typically used in developing drinking water advisory guidelines. These cooking study results indicate that food prepared in water containing Sr should be considered as part of the food in a dietary exposure assessment.

Nationwide reconnaissance of contaminants of emerging concern in source and treated drinking waters of the United States.

When chemical or microbial contaminants are assessed for potential effect or possible regulation in ambient and drinking waters, a critical first step is determining if the contaminants occur and if they are at concentrations that may cause human or ecological health concerns. To this end, source and treated drinking water samples from 29 drinking water treatment plants (DWTPs) were analyzed as part of a two-phase study to determine whether chemical and microbial constituents, many of which are considered contaminants of emerging concern, were detectable in the waters. Of the 84 chemicals monitored in the 9 Phase I DWTPs, 27 were detected at least once in the source water, and 21 were detected at least once in treated drinking water. In Phase II, which was a broader and more comprehensive assessment, 247 chemical and microbial analytes were measured in 25 DWTPs, with 148 detected at least once in the source water, and 121 detected at least once in the treated drinking water. The frequency of detection was often related to the analyte's contaminant class, as pharmaceuticals and anthropogenic waste indicators tended to be infrequently detected and more easily removed during treatment, while per and polyfluoroalkyl substances and inorganic constituents were both more frequently detected and, overall, more resistant to treatment. The data collected as part of this project will be used to help inform evaluation of unregulated contaminants in surface water, groundwater, and drinking water.

The development of a matrix-assisted laser desorption/ionization mass spectrometry-based method for the protein fingerprinting and identification of Aeromonas species using whole cells.

This report describes the development of a method to detect the waterborne pathogen Aeromonas using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The genus Aeromonas is one of several medically significant genera that have gained prominence due to their evolving taxonomy and controversial role in human diseases. In this study, MALDI-MS was applied to the characterization of seventeen species of Aeromonas. These seventeen species were represented by thirty-two strains, which included type, reference and clinical isolates. Intact cells from each strain were used to generate a reproducible library of protein mass spectral fingerprints or m/z signatures. Under the test conditions used, peak lists of the mass ions observed in each species revealed that three mass ions were conserved among all the seventeen species tested. These common mass ions having an average m/z of 6301, 12,160 or 12,254, and 13,450, can be potentially used as genus-specific biomarkers to identify Aeromonas in unknown samples. A dendrogram generated using the m/z signatures of all the strains tested indicated that the mass spectral data contained sufficient information to distinguish between genera, species, and strains. There are several advantages of using MALDI-MS based protein mass spectral fingerprinting of whole cells for the identification of microorganisms as well as for their differentiation at the sub-species level: (1) the capability to detect proteins, (2) high throughput, and (3) relatively simple sample preparation techniques. The accuracy and speed with which data can be obtained makes MALDI-MS a powerful tool especially suited for environmental monitoring and detection of biological hazards.

Characterization of nigerlysin, hemolysin produced by Aspergillus niger, and effect on mouse neuronal cells in vitro.

Aspergillus niger produced a proteinaceous hemolysin, nigerlysin when incubated on sheep's blood agar (SBA) at both 23 and 37 degrees C. Nigerlysin was purified from tryptic soy broth (TSB) culture filtrate and found to have a molecular weight of approximately 72 kDa, with an isoelectric point of 3.45. Nigerlysin is heat stable up to 65 degrees C but unstable at 75 degrees C when incubated for 10 min. Circular dichroic analysis revealed that nigerlysin has an alpha helical structure. Exposure of mouse primary cortical neuronal cells to 0.1 microg ml(-1) of nigerlysin resulted in the rapid loss of their viability, approximately 50% in 24 h. The IC50 is estimated to be 0.037 microg ml(-1), or between 0.034 and 0.041 microg ml(-1) at the 95% confidence level.

Increasing Prevalence Rate of Nontuberculous Mycobacteria Infections in Five States, 2008-2013.

RATIONALE: Many nontuberculous mycobacteria (NTM) are clinically significant pathogens that cause disease in a variety of different human organs and tissues. OBJECTIVES: A population-based study was undertaken to investigate the prevalence of patients with a positive specimen for NTM within five states of the United States. METHODS: We determined the case and age distribution of patients with at least one specimen positive for NTM, using data submitted to the disease surveillance systems of five states (Maryland, Mississippi, Missouri, Ohio, and Wisconsin) between 2008 and 2013. Crude, age-specific, and age-adjusted prevalence rates per 100,000 persons were calculated for each state. MEASUREMENTS AND MAIN RESULTS: From 2008 to 2013, a total of 24,226 NTM cases were reported to the disease surveillance systems of the five states. The overall average annual age-adjusted prevalence rate rose from 8.7 to 13.9 per 100,000 persons between the beginning and end of the surveillance period. The number of cases and case rate in the 50-80+-year age group was higher than in the 0-49-year age group. Prevalence by age category differed among the five states. The highest number of NTM cases was observed in Mississippi for the 80+-year age group, whereas Wisconsin observed the highest number of NTM cases in the 60- to 69-year age group. CONCLUSIONS: From 2008 to 2013, the number of patients with positive specimens for NTM rose. This trend is likely to continue in the coming decade as the U.S. population ages. To reduce the prevalence of NTM infections, medical guidance for susceptible populations is needed regarding actions that can be taken to avoid sources and routes of exposure to NTMs if the disease burden is to be reduced.