Mycobacteria in Municipal Wastewater Treatment and Reuse: Microbial Diversity for Screening the Occurrence of Clinically and Environmentally Relevant Species in Arid Regions

Genomic insights into chlorine resistance of a Mycobacterium sp. strain isolated from treated wastewater effluent

Chlorine is the principal microbial disinfectant used for water treatment. However, chlorine-resistant bacteria such as Mycobacterium spp., can survive chlorine treatment and even grow in the presence of chlorine, posing potential public health risks. In this study, we isolated a Mycobacterium sp. strain from treated effluent and investigated its chlorine resistance and recovery using transcriptomic analyses. Specifically, isolate M1, showing 94.58 % average nucleotide identity (ANI) with Mycobacterium massilipolynesiensis type genome, was exposed to 1 ppm HOCl for 30 min and subjected to RNA sequencing. Genes identified as upregulated compared to control conditions (no HOCl) were involved in detoxification (toxic compound degradation; nemA; log2 fold-change [FC]: 7.41), redox homeostasis (COQ5; quinone synthesis; log2 FC 5.70, rosB; riboflavin synthesis; log2 FC 5.61), protein homeostasis (cysHKO, moeZ cysteine biosynthesis, and arg complex; arginine metabolism), and lipid metabolism (cpnA; 6.95 FC) suggesting a multifaceted adaptation to oxidative stress. Levels of a few membrane transport proteins (czcD, and bcr) were also upregulated, highlighting their role in chlorine exposure. Overall, this study broadens the understanding of chlorine resistance strategies employed by Mycobacterium sp. to combat oxidative stress and the resulting toxic intracellular compounds, and has implications for adjusting water treatment technologies toward eliminating mycobacteria.

River Sediments Downstream of Villages in a Karstic Watershed Exhibited Increased Numbers and Higher Diversity of Nontuberculous Mycobacteria

The impact of residential villages on the nontuberculous mycobacteria (NTM) in streams flowing through them has not been studied in detail. Water and sediments of streams are highly susceptible to anthropogenic inputs such as surface water flows. This study investigated the impact of seven residential villages in a karst watershed on the prevalence and species spectrum of NTM in water and sediments. Higher NTM species diversity (i.e., 19 out of 28 detected) was recorded downstream of the villages and wastewater treatment plants (WWTPs) compared to sampling sites upstream (i.e., 5). Significantly, higher Zn and lower silicon concentrations were detected in sediments inside the village and downstream of the WWTP's effluents. Higher phosphorus concentration in sediment was downstream of WWTPs compared to other sampling sites. The effluent from the WWTPs had a substantial impact on water quality parameters with significant increases in total phosphorus, anions (Cl-and N-NH3-), and cations (Na+ and K+). The results provide insights into NTM numbers and species diversity distribution in a karst watershed and the impact of urban areas. Although in this report the focus is on the NTM, it is likely that other water and sediment microbes will be influenced as well.

A narrative review of nontuberculous mycobacterial pulmonary disease: microbiology, epidemiology, diagnosis, and management challenges

INTRODUCTION

Nontuberculous mycobacteria (NTM) are a diverse group of mycobacterial species that are ubiquitous in the environment. They are opportunistic pathogens that can cause a range of diseases, especially in individuals with underlying structural lung disease or compromised immune systems.

AREAS COVERED

This paper provides an in-depth analysis of NTM infections, including microbiology, environmental sources and transmission pathways, risk factors for disease, epidemiology, clinical manifestations and diagnostic approaches, guideline-based treatment recommendations, drugs under development, and management challenges.

EXPERT OPINION

Future approaches to the management of NTM pulmonary disease will require therapies that are well tolerated, can be taken for a shorter time period and perhaps less frequently, have few drug-drug interactions, and are active against the various strains of pathogens. As the numbers of infections increase, such therapies will be welcomed by clinicians and patients.

Effect of odor treatment systems on bioaerosol microbial concentration and diversity from wastewater treatment plants

Biofiltration, activated carbon and chemical scrubbing are technologies used for odor control in wastewater treatment plants. These systems may also influence the airborne microbial load in treated air. The study objectives were to 1) evaluate the capacity of three odor control system technologies to reduce the airborne concentration of total bacteria, Legionella, L. pneumophila, non-tuberculous mycobacteria (NTM) and Cladosporium in winter and summer seasons and 2) to describe the microbial ecology of the biofiltration system and evaluate its impact on treated air microbial diversity. A reduction of the total bacterial concentration up to 25 times was observed after odor treatment. Quantification by qPCR revealed the presence of Legionella spp. in all air samples ranging between 26 and 1140 GC/m³, while L. pneumophila was not detected except for three samples below the limit of quantification. A significant increase of up to 25-fold of Legionella spp. was noticed at the outlet of two of the three treatment systems. NTM were ubiquitously detected before air treatment (up to 2500 GC/m³) and were significantly reduced by all 3 systems (up to 13-fold). Cladosporium was measured at low concentrations for each system (< 190 GC/m³), with 68 % of the air samples below the limit of detection. Biodiversity results revealed that biofiltration system is an active process that adapts to air pollutants over time. Legionella spp. were detected in significant abundance in the air once treated in winter (up to 27 %). Nevertheless, the abundance of protozoan hosts is low and does not explain the multiplication of Legionella spp. The season remains the most influential factor shaping biodiversity. In summer only, air biofiltration caused a significant enrichment of the biodiversity. Although odor control technologies are not designed for bacterial mitigation, findings from this study suggest their potential to reduce the abundance of some genera harboring pathogenic species.

Wastewater microorganisms impact microbial diversity and important ecological functions of stream periphyton

Effluents of wastewater treatment plants can impact microbial communities in the receiving streams. However, little is known about the role of microorganisms in wastewater as opposed to other wastewater constituents, such as nutrients and micropollutants. We aimed therefore at determining the impact of wastewater microorganisms on the microbial diversity and function of periphyton, key microbial communities in streams. We used a flow-through channel system to grow periphyton upon exposure to a mixture of stream water and unfiltered or ultra-filtered wastewater. Impacts were assessed on periphyton biomass, activities and tolerance to micropollutants, as well as on microbial diversity. Our results showed that wastewater microorganisms colonized periphyton and modified its community composition, resulting for instance in an increased abundance of Chloroflexi and a decreased abundance of diatoms and green algae. This led to shifts towards heterotrophy, as suggested by the changes in nutrient stoichiometry and the increased mineralization potential of carbon substrates. An increased tolerance towards micropollutants was only found for periphyton exposed to unfiltered wastewater but not to ultra-filtered wastewater, suggesting that wastewater microorganisms were responsible for this increased tolerance. Overall, our results highlight the need to consider the role of wastewater microorganisms when studying potential impacts of wastewater on the receiving water body.

Metabolically Active Prokaryotes and Actively Transcribed Antibiotic Resistance Genes in Sewer Systems: Implications for Public Health and Microbially Induced Corrosion

Sewer systems are reservoirs of pathogens and bacteria carrying antibiotic resistance genes (ARGs). However, most recent high-throughput studies rely on DNA-based techniques that cannot provide information on the physiological state of the cells nor expression of ARGs. In this study, wastewater and sewer sediment samples were collected from combined and separate sanitary sewer systems. The metabolically active prokaryote community was evaluated using 16S rRNA amplicon sequencing and actively transcribed ARG abundance was measured using mRNA RT-qPCR. Three (sul1, bla_TEM, tet(G)) of the eight tested ARGs were quantifiable in select samples. Sewer sediment samples had greater abundance of actively transcribed ARGs compared to wastewater. Microbiome analysis showed the presence of metabolically active family taxa that contain clinically relevant pathogens (Pseudomonadaceae, Enterobacteraceae, Streptococcaceae, Arcobacteraceae, and Clostridiaceae) and corrosion-causing prokaryotes (Desulfobulbaceae and Desulfovibrionaceae) in both matrices. Spirochaetaceae and methanogens were more common in the sediment matrix while Mycobacteraceae were more common in wastewater. The microbiome obtained from 16S rRNA sequencing had a significantly different structure from the 16S rRNA gene microbiome. Overall, this study demonstrates active transcription of ARGs in sewer systems and provides insight into the abundance and physiological state of taxa of interest in the different sewer matrices and sewer types relevant for wastewater-based epidemiology, corrosion, and understanding the hazard posed by different matrices during sewer overflows.

The source and fate of Mycobacterium tuberculosis complex in wastewater and possible routes of transmission

BACKGROUND

The Mycobacterium tuberculosis complex (MTBC) consists of causative agents of both human and animal tuberculosis and is responsible for over 10 million annual infections globally. Infections occur mainly through airborne transmission, however, there are possible indirect transmissions through a faecal-oral route which is poorly reported. This faecal-oral transmission could be through the occurrence of the microbe in environments such as wastewater. This manuscript, therefore, reviews the source and fate of MTBC in the wastewater environment, including the current methods in use and the possible risks of infections.

RESULTS

The reviewed literature indicates that about 20% of patients with pulmonary TB may have extra-pulmonary manifestations such as GITB, resulting in shedding in feaces and urine. This could potentially be the reason for the detection of MTBC in wastewater. MTBC concentrations of up to 5.5 × 105 (±3.9 × 105) copies/L of untreated wastewater have been reported. Studies have indicated that wastewater may provide these bacteria with the required nutrients for their growth and could potentially result in environmental transmission. However, 98.6 (± 2.7) %, removal during wastewater treatment, through physical-chemical decantation (primary treatment) and biofiltration (secondary treatment) has been reported. Despite these reports, several studies observed the presence of MTBC in treated wastewater via both culture-dependent and molecular techniques.

CONCLUSION

The detection of viable MTBC cells in either treated or untreated wastewater, highlights the potential risks of infection for wastewater workers and communities close to these wastewater treatment plants. The generation of aerosols during wastewater treatment could be the main route of transmission. Additionally, direct exposure to the wastewater containing MTBC could potentially contribute to indirect transmissions which may lead to pulmonary or extra-pulmonary infections. This calls for the implementation of risk reduction measures aimed at protecting the exposed populations.

Metagenomic community composition and resistome analysis in a full-scale cold climate wastewater treatment plant

BACKGROUND

Wastewater treatment plants are an essential part of maintaining the health and safety of the general public. However, they are also an anthropogenic source of antibiotic resistance genes. In this study, we characterized the resistome, the distribution of classes 1-3 integron-integrase genes (intI1, intI2, and intI3) as mobile genetic element biomarkers, and the bacterial and phage community compositions in the North End Sewage Treatment Plant in Winnipeg, Manitoba. Samples were collected from raw sewage, returned activated sludge, final effluent, and dewatered sludge. A total of 28 bacterial and viral metagenomes were sequenced over two seasons, fall and winter. Integron-integrase genes, the 16S rRNA gene, and the coliform beta-glucuronidase gene were also quantified during this time period.

RESULTS

Bacterial classes observed above 1% relative abundance in all treatments were Actinobacteria (39.24% ± 0.25%), Beta-proteobacteria (23.99% ± 0.16%), Gamma-proteobacteria (11.06% ± 0.09%), and Alpha-proteobacteria (9.18 ± 0.04%). Families within the Caudovirales order: Siphoviridae (48.69% ± 0.10%), Podoviridae (23.99% ± 0.07%), and Myoviridae (19.94% ± 0.09%) were the dominant phage observed throughout the NESTP. The most abundant bacterial genera (in terms of average percent relative abundance) in influent, returned activated sludge, final effluent, and sludge, respectively, includes Mycobacterium (37.4%, 18.3%, 46.1%, and 7.7%), Acidovorax (8.9%, 10.8%, 5.4%, and 1.3%), and Polaromonas (2.5%, 3.3%, 1.4%, and 0.4%). The most abundant class of antibiotic resistance in bacterial samples was tetracycline resistance (17.86% ± 0.03%) followed by peptide antibiotics (14.24% ± 0.03%), and macrolides (10.63% ± 0.02%). Similarly, the phage samples contained a higher prevalence of macrolide (30.12% ± 0.30%), peptide antibiotic (10.78% ± 0.13%), and tetracycline (8.69% ± 0.11%) resistance. In addition, intI1 was the most abundant integron-integrase gene throughout treatment (1.14 × 104 gene copies/mL) followed by intI3 (4.97 × 103 gene copies/mL) while intI2 abundance remained low (6.4 × 101 gene copies/mL).

CONCLUSIONS

Wastewater treatment successfully reduced the abundance of bacteria, DNA phage and antibiotic resistance genes although many antibiotic resistance genes remained in effluent and biosolids. The presence of integron-integrase genes throughout treatment and in effluent suggests that antibiotic resistance genes could be actively disseminating resistance between both environmental and pathogenic bacteria.

The bioaerosols emitted from toilet and wastewater treatment plant: a literature review

The aerosols harboring microorganisms and viruses released from the wastewater system into the air have greatly threatened the health and safety of human beings. The wastewater systems, including toilet and wastewater treatment plant (WWTP), are the major locations of epidemic infections due to the extensive sources of aerosols, as well as multifarious germs and microorganisms. Viruses and microorganisms may transport from both toilet and hospital into municipal pipes and subsequently into WWTP, which accounts for the main source of bioaerosols dispersed in the air of the wastewater system. This review aims to elaborate the generation, transmission, and diffusion processes of bioaerosols at toilet and WWTP. Moreover, the main factors affecting bioaerosol transmission and the corresponding prevention strategies for the airborne and inhaled bioaerosols are also discussed. Collectively, this review highlights the importance of managing bioaerosol occurrence in the wastewater system, which has aroused increasing concern from the public.

Non-Tuberculous Mycobacteria: Molecular and Physiological Bases of Virulence and Adaptation to Ecological Niches

Non-tuberculous mycobacteria (NTM) are paradigmatic colonizers of the total environment, circulating at the interfaces of the atmosphere, lithosphere, hydrosphere, biosphere, and anthroposphere. Their striking adaptive ecology on the interconnection of multiple spheres results from the combination of several biological features related to their exclusive hydrophobic and lipid-rich impermeable cell wall, transcriptional regulation signatures, biofilm phenotype, and symbiosis with protozoa. This unique blend of traits is reviewed in this work, with highlights to the prodigious plasticity and persistence hallmarks of NTM in a wide diversity of environments, from extreme natural milieus to microniches in the human body. Knowledge on the taxonomy, evolution, and functional diversity of NTM is updated, as well as the molecular and physiological bases for environmental adaptation, tolerance to xenobiotics, and infection biology in the human and non-human host. The complex interplay between individual, species-specific and ecological niche traits contributing to NTM resilience across ecosystems are also explored. This work hinges current understandings of NTM, approaching their biology and heterogeneity from several angles and reinforcing the complexity of these microorganisms often associated with a multiplicity of diseases, including pulmonary, soft-tissue, or milliary. In addition to emphasizing the cornerstones of knowledge involving these bacteria, we identify research gaps that need to be addressed, stressing out the need for decision-makers to recognize NTM infection as a public health issue that has to be tackled, especially when considering an increasingly susceptible elderly and immunocompromised population in developed countries, as well as in low- or middle-income countries, where NTM infections are still highly misdiagnosed and neglected.

Impact of sludge bulking on receiving environment using quantitative microbial risk assessment (QMRA)-based management for full-scale wastewater treatment plants

During sludge bulking in wastewater treatment plants (WWTPs), high amounts of potentially pathogenic bacteria would release into the environment, causing various human-health risks. This is the first study attempting to assess the microbial infections associated with the reuse of WWTP effluents under various bulking conditions. Three common waterborne pathogens, viz., E. coli O157:H7, Salmonella, and Mycobacterium, were quantified from full-scale WWTPs using DNA extraction and qPCR at different sludge volume indices (SVIs). The detected pathogens were incorporated into a quantitative microbial risk assessment (QMRA) model to determine the applicability of WWTP discharge for recreational (bathing) activities and agricultural practices. The QMRA exposures were children, women, and men during swimming, and farmers and vegetable consumers during irrigation. Bacterial abundance in the treated wastewater increased in response to SVIs, and the QMRA values at all bulking events exceeded the tolerable risk of one case of infection per 10,000 people per year. Hence, various disinfection scenarios (chlorination, ultraviolet, and ozonation) were hypothetically tested to control the risks associated with pathogenic bacteria, allowing for safe disposal and reuse of the treated effluent. The ultraviolet application provided the highest ability to inactivate the pathogenic bacteria, except for the case of children exposed to Salmonella infection during swimming. The reduction of Mycobacterium infection risks with either chlorination or ozonation showed inefficient results. This study would be helpful for the management of human health risks associated with effluent wastewater containing pathogens, i.e., particularly concerning the case of sludge bulking.

Diversity of Mycobacteriaceae from aquatic environment at the São Paulo Zoological Park Foundation in Brazil

We investigated the species diversity of Mycobacteriaceae in surface water samples from six environments at the zoological park in São Paulo, Brazil. Three hundred and eighty isolates were cultivated and identified by phenotypic characteristics (growth rate and pigmentation) and sequencing of hsp65, rpoB and 16S rRNA genes. The results revealed that almost 48% of the isolates could be identified at the species level; about 50% were classified at the genus level, and only less than 2% of the isolates showed an inconclusive identification. The isolates classified at the genus level and not identified were then evaluated by phylogenetic analyses using the same three concatenated target genes. The results allowed us to identify at the genus level some isolates that previously had inconclusive identification, and they also suggested the presence of putative candidate species within the sample, demonstrating that this zoological park is an important source of diversity.

Mycobacterium kansasii arthritis of the elbow in an immunocompetent patient with a suspected soft-tissue tumor

Mycobacterium kansasii is one of the major non-tuberculous mycobacteria species that typically cause pulmonary diseases. M. kansasii is known to cause septic arthritis as an extrapulmonary disease in immunosuppressed patients or chronic skin disease. Herein, we present a case of M. kansasii arthritis involving the elbow of an immunocompetent patient, which was initially suspected to be a soft-tissue tumor. A 70-year-old man presented with a swollen left elbow that had progressed for 18 months with deteriorating arthralgia and limited range of motion. Magnetic resonance imaging revealed filling of the intra-articular space of the elbow and surrounding of the radial head with a soft tissue mass with mixed signal intensity. Initial incisional biopsy was performed via the lateral approach to the elbow joint, and pathological examination of the mass did not reveal any evidence of malignancy. One year after the first operation, arthroscopic surgery was performed to excise the mass following the recurrence of swelling and limited function of the elbow. Pathological examination of the resected synovium revealed epithelioid granulomas containing a multinucleated giant cell and inflammatory cell infiltration, characteristic of mycobacterial infection. M. kansasii was cultured after 2 weeks of incubation of the synovial sample. He experienced full resolution of the swelling and limited function following a combination of synovectomy and multidrug antimycobacterial treatment (rifampin 600 mg/day, clarithromycin 800 mg/day, and ethambutol 750 mg/day). This case highlights the need to consider this rare infection in the differential diagnosis of intra-articular soft tissue tumor-like lesions even in immunocompetent patients.

Floc-size effects of the pathogenic bacteria in a membrane bioreactor plant

The size nature of sludge flocs could affect the occurrence and distribution of bacterial pathogens in wastewater treatment plants (WWTPs). In this study, the floc-size dependence of bacterial pathogens in the activated sludge of a WWTP was investigated using high-throughput metagenomic sequencing approaches. The results showed that a total of 423 pathogenic species belonging to 123 genera were identified in the three size-fractionated flocs. Also, we found that all the pathogens on the WHO's global priority pathogens list were detected in the size-fractionated flocs, with relative abundance of 0.4%, 0.3% and 0.3% for large-size, medium-size and small-size flocs, respectively, indicating the severe human and environmental health risks of activated sludge. Importantly, our results revealed that the pathogenic species showed a clear floc-size dependent distribution manner, leading to significant differences (P < 0.05) of pathogenic communities among the size-fractionated flocs. Additionally, by partitioning pathogens based on the occurrence and significant difference in abundances, we suggested the following distribution features: 1) large flocs-associated pathogens, such as Borrelia recurrentis, Actinobacillus ureae and Campylobacter gracilis; 2) medium flocs-associated pathogens, such as Mycobacterium szulgai and Ureaplasma urealyticum; and 3) small flocs-associated pathogens, such as Rickettsia akari, Staphylococcus anginosus and Helicobacter cinaedi. Overall, this study provides a comprehensive understanding of pathogens in activated sludge, which is expected to aid in assessment and management of pathogen risks.

Mycobacterial species and their contribution to cholesterol degradation in wastewater treatment plants

Mycobacterium often presents as an abundant bacterial genus in activated sludge in many wastewater treatment plants (WWTPs), but the species-level taxonomy and functions remain poorly understood. In this study, we profiled the mycobacterial communities in eleven WWTPs from five countries by pyrosequencing the rpoB amplicons and searching against a customized database of mycobacterial rpoB sequences. Results indicated that major mycobacterial species were related to M. brumae, M. crocinum, M. sphagni, etc., most of which belong to poorly characterized rapidly-growing group. A few opportunistic pathogenic species were detected, suggesting the potential risk of mycobacteria in WWTPs. Genomic analysis of four isolates from activated sludge indicated these genomes contained genes of degradations of alkane, aromatics, steroids and a variety of cytochrome P450 families. Additionally, a few key genes responsible for cholesterol degradation were detected in a full-scale activated sludge metatranscriptomic dataset reported previously and taxonomically assigned to mycobacteria. Evidence showed that all isolates can degrade cholesterol, a major composition of sewage. Relative abundance of mycobacteria in activated sludge was enriched by 4.7 folds after adding cholesterol into the influent for one week. Our results provided the insights into mycobacterial species and functions in WWTPs.

Biodegradation study of methadone by adapted activated sludge: Elimination kinetics, transformation products and ecotoxicological evaluation

The biotransformation study of difficult-to-degrade opioid analgesic methadone (MTHD) was performed by activated sludge culture adapted to high concentration of methadone (10 mg/L). The study included determination of elimination kinetics of the parent compound, taxonomic characterization of microbial culture, identification of biotransformation products (TPs) and assessment of ecotoxicological effects of biotransformation processes. The chemical analyses were performed by ultra-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry, whereas the ecotoxicological assessment was made based on determinations of toxicity to freshwater algae. Changes of the adapted sludge culture during the experiment were followed using the 16S rRNA gene amplicon sequencing. Depending on the experimental conditions, the elimination efficiency of methadone (10 mg/L) varied from 9% to 93% with the corresponding half-lives from 11.4 days to 1.5 days. A significantly faster elimination (t_1/2 from 1.5 days to 5.8 days) was achieved at cometabolic conditions, using glucose-containing media, as compared to the experiments with MTHD as a single organic carbon source (t_1/2 = 11.4 days). Moreover, increased biotransformation rate following the additional supplementation of ammonia, revealed a possible importance of nitrogen availability for the transformation at cometabolic conditions. The elimination of parent compound was associated with the formation of 3 different TPs, two of which were identical to main human metabolites of MTHD, 2-Ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline (EMDP). EDDP represented over 90% of the total TP concentration at the end of experiment. The biodegradation of MTHD was associated with a pronounced drop in algal toxicity, confirming a rather positive ecotoxicological outcome of the achieved biotransformation processes.

Characterization of the Microbiome at the World's Largest Potable Water Reuse Facility

Conventional water resources are not sufficient in many regions to meet the needs of growing populations. Due to cyclical weather cycles, drought, and climate change, water stress has increased worldwide including in Southern California, which serves as a model for regions that integrate reuse of wastewater for both potable and non-potable use. The Orange County Water District (OCWD) Advanced Water Purification Facility (AWPF) is a highly engineered system designed to treat and produce up to 100 million gallons per day (MGD) of purified water from a municipal wastewater source for potable reuse. Routine facility microbial water quality analysis is limited to standard indicators at this and similar facilities. Given recent advances in high throughput DNA sequencing techniques, complete microbial profiling of communities in water samples is now possible. By using 16S/18S rRNA gene sequencing, metagenomic and metatranscriptomic sequencing coupled to a highly accurate identification method along with 16S rRNA gene qPCR, we describe a detailed view of the total microbial community throughout the facility. The total bacterial load of the water at stages of the treatment train ranged from 3.02 × 10⁶ copies in source, unchlorinated wastewater feed to 5.49 × 10¹ copies of 16S rRNA gene/mL after treatment (consisting of microfiltration, reverse osmosis, and ultraviolet/advanced oxidation). Microbial diversity and load decreased by several orders of magnitude after microfiltration and reverse osmosis treatment, falling to almost non-detectable levels that more closely resembled controls of molecular grade laboratory water than the biomass detected in the source water. The presence of antibiotic resistance genes and viruses was also greatly reduced. Overall, system design performance was achieved, and comprehensive microbial community analysis was found to enable a more complete characterization of the water/wastewater microbial signature.

Therapy for Mycobacterium kansasii Infection: Beyond 2018

The current standard of care therapy for pulmonary Mycobacterium kansasii infection is isoniazid (300 mg/day), rifampin (600 mg/day), and ethambutol (15 mg/kg/day) for 12 months after achieving sputum culture negativity. Rifampin is the key drug in this regimen. The contribution of isoniazid is unclear since its in vitro MICs against M. kansasii are near the peak achievable serum levels and more than 100-fold greater than the MICs for Mycobacterium tuberculosis. Ethambutol likely decreases the emergence of rifampin resistant organisms. There are several new drug classes (e.g., quinolones, macrolides, nitroimidazoles, diarylquinolines, and clofazimine) that exhibit antimycobacterial activities against M. tuberculosis but have not yet been adequately studied against M. kansasii infections. The evaluation of in vitro activities of these agents as well as their study in new regimens in comparison to the standard of care regimen in mouse infection models should be undertaken. This knowledge will inform development of human clinical trials of new regimens in comparison to the current standard of care regimen. It is likely that shorter and more effective therapy is achievable with currently available drugs.

Antibiotic Residue in the Aquatic Environment: Status in Africa

Information on the presence of antibiotics is sparse for all types of water in Africa, including groundwater, surface water, effluent of wastewater treatment plants (WWTPs) and municipal potable water. With the relatively high sales of different antibiotics to treat infectious diseases in the human population of Africa, the residual of the antibiotics is bound to be released through excretion via urine or fecal matter in parallel to the high sales. This article reviews the published analysis on the occurrence of antibiotics in the environment particularly in the aquatic environment in some countries in Africa. In general, sulfamethoxazole was the most commonly detected in Africa surface water (with eight reports from four countries) at a concentration range of 0.00027 – 39 μgL-1. Wastewater analysis is believed to give an early warning for preventing epidemics. Thus, we discuss the associated level of antibiotic resistance to some prevalent diseases in Africa whose aetiological agents can develop antibiotic resistance due to exposure to antibiotic residue in water. This is important because of rising population of immuno-deficient African residents ravaged by HIV/AIDS, poor nutrition and less efficient sanitation systems.

Global Environmental Nontuberculous Mycobacteria and Their Contemporaneous Man-Made and Natural Niches

Seminal microbiological work of environmental nontuberculous mycobacteria (NTM) includes the discovery that NTM inhabit water distribution systems and soil, and that the species of NTM found are geographically diverse. It is likely that patients acquire their infections from repeated exposures to their environments, based on the well-accepted paradigm that water and soil bioaerosols - enriched for NTM - can be inhaled into the lungs. Support comes from reports demonstrating NTM isolated from the lungs of patients are genetically identical to NTM found in their environment. Well documented sources of NTM include peat-rich soils, natural waters, drinking water, hot water heaters, refrigerator taps, catheters, and environmental amoeba. However, NTM have also been recovered in biofilms from ice machines, heated nebulizers, and heater-cooler units, as well as seat dust from theaters, vacuum cleaners, and cobwebs. New studies on the horizon aim to significantly expand the current knowledge of environmental NTM niches in order to improve our current understanding of the specific ecological factors driving the emergence of NTM lung disease. Specifically, the Hawaiian Island environment is currently being studied as a model to identify other point sources of exposure as it is the U.S. state with the highest number of NTM lung disease cases. Because of its geographic isolation and unique ecosystem, the Hawaiian environment is being probed for correlative factors that may promote environmental NTM colonization.

A Geospatial Epidemiologic Analysis of Nontuberculous Mycobacterial Infection: An Ecological Study in Colorado

RATIONALE

Nontuberculous mycobacteria (NTM) are ubiquitous environmental microorganisms. Infection is thought to result primarily from exposure to soil and/or water sources. NTM disease prevalence varies greatly by geographic region, but the geospatial factors influencing this variation remain unclear.

OBJECTIVES

To identify sociodemographic and environmental ecological risk factors associated with NTM infection and disease in Colorado.

METHODS

We conducted an ecological study, combining data from patients with a diagnosis of NTM disease from National Jewish Health's electronic medical record database and ZIP code-level sociodemographic and environmental exposure data obtained from the U.S. Geological Survey, the U.S. Department of Agriculture, and the U.S. Census Bureau. We used spatial scan methods to identify high-risk clusters of NTM disease in Colorado. Ecological risk factors for disease were assessed using Bayesian generalized linear models assuming Poisson-distributed discrete responses (case counts by ZIP code) with the log link function.

RESULTS

We identified two statistically significant high-risk clusters of disease. The primary cluster included ZIP codes in urban regions of Denver and Aurora, as well as regions south of Denver, on the east side of the Continental Divide. The secondary cluster was located on the west side of the Continental Divide in rural and mountainous regions. After adjustment for sociodemographic, drive time, and soil variables, we identified three watershed areas with relative risks of 12.2, 4.6, and 4.2 for slowly growing NTM infections compared with the mean disease risk for all watersheds in Colorado. This study population carries with it inherent limitations that may introduce bias. The lack of complete capture of NTM cases in Colorado may be related to factors such as disease severity, education and income levels, and insurance status.

CONCLUSIONS

Our findings provide evidence that water derived from particular watersheds may be an important source of NTM exposure in Colorado. The watershed with the greatest risk of NTM disease contains the Dillon Reservoir. This reservoir is also the main water supply for major cities located in the two watersheds with the second and third highest disease risk in the state, suggesting an important possible source of infection.