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Diagnosing Mycobacterium Tuberculosis Infections - News-Medical.net
Tuberculosis (TB) is a significant global health challenge caused by Mycobacterium tuberculosis. Nontuberculous mycobacteria (NTM) can produce symptoms similar to TB, with some species leading to serious pulmonary issues.
Image Credit: Kateryna Kon/Shutterstock.Com
Accurate detection is essential to prevent misdiagnosis and ensure the right treatment, particularly in cases involving drug-resistant TB or NTM infections. The Hi-PCR® MTB/NTM Probe PCR Kit offers a quick and dependable method for detecting and differentiating MTB and NTM in clinical samples. Utilizing real-time PCR technology with specialized hydrolysis probes, this kit delivers results in under 70 minutes, making it an invaluable tool for clinical diagnostics, monitoring, and research.
IntroductionTuberculosis (TB) continues to be a major global health issue, resulting in millions of new cases and fatalities annually. It is primarily caused by the Mycobacterium tuberculosis (MTB) complex and predominantly affects the lungs. Meanwhile, nontuberculous mycobacteria (NTM) can also mimic TB symptoms, with some species being notably significant in pulmonary disease.
Conventional TB diagnostic techniques, such as smear microscopy and culture, are often slow and lack sensitivity and specificity in distinguishing between TB and NTM, leading to delays in both diagnosis and treatment. To overcome these obstacles, probe-based real-time PCR assays have been created to accurately identify and differentiate MTB and NTM infections.
The Hi-PCR® MTB/NTM Probe PCR Kit provides a fast and reliable approach for the simultaneous detection of MTB and NTM in clinical samples, facilitating timely and appropriate treatment decisions.
Overview of the technology that underpins the Hi-PCR® MTB/NTM Probe PCR KitThe Hi-PCR® MTB/NTM Probe PCR Kit employs real-time PCR technology to amplify bacterial DNA from clinical specimens, followed by detection with fluorescent probes. This approach enables quick and precise detection and differentiation of Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM) in a single-tube assay.
The method involves amplifying target DNA using hydrolysis probes, which are short oligonucleotides with a fluorescent dye attached at the 5' end and a quencher dye at the 3' end. During amplification, the probe is cleaved, separating the dye from the quencher, leading to increased fluorescence that is monitored in real-time. This allows for the immediate and accurate identification of MTB and NTM DNA.
The Hi-PCR® MTB/NTM Probe PCR Kit includes a single tube containing oligonucleotides (primers and probes) designed to amplify conserved regions of MTB and NTM genes, along with an internal control amplification system.
Each component is labeled with different fluorophores: the MTB complex target is detected in the FAM channel, the NTM target in the ROX channel, and the internal control target in the JOE channel.
Work flowFigure 1. Image representing workflow of the process and One Stop Solution offered by HiGenoMB®. Image Credit: Himedia Laboratories Private Limited
Molecular featuresThe Hi‐PCR®MTB/NTM Probe PCR Kit has been rigorously validated across multiple platforms, including Bio-Rad CFX Opus 96, Applied Biosystems Quant Studio 5, and Insta Q96® Plus Real-Time PCR Systems.
Analytical sensitivity Limit of Detection (LoD)The Limit of Detection (LoD) is defined as the concentration (copies per μl of the eluate) of a target molecule that can be detected with 95% probability, in accordance with CLSI EP17-A2 guidelines.
The LoD assay for the Hi-PCR® MTB/NTM Probe PCR Kit was conducted using 20 replicates on the Biorad CFX Opus 96, Applied Biosystems Quant Studio 5, and Insta Q96® Plus Real-Time PCR Systems.
The assay utilized ATCC standards of Quantitative Genomic DNA from Mycobacterium tuberculosis strain H37Ra (ATCC 25177DQ) and Mycobacterium avium subsp. Paratuberculosis strain K-10 (ATCC BAA-968D). The detectable limit for the Hi-PCR® MTB/NTM Probe PCR Kit was found to be 1 copy per μL for MTB and ≤ 10 copies per μL for NTM.
Figure 2. Dilution series (1000 copies/μl, 100 copies/μl, 10 copies/μl and 1 copy/ μl) of A) Quantitative Genomic DNA from Mycobacterium tuberculosis strain H37Ra (ATCC 25177DQ) and B) Quantitative Genomic DNA from Mycobacterium avium subsp. Paratuberculosis strain K‐10 (ATCC BAA‐968D) run on the Applied Biosystems Quant Studio 5 Real Time PCR Systems. Image Credit: Himedia Laboratories Private Limited
Analytical specificity Inclusivity – In silicoThe analytical specificity of the Hi-PCR® MTB/NTM Probe PCR kit was ensured by in-silico analysis of the oligonucleotides (primers and probes). The oligonucleotide sequences of all the targets were checked by sequence comparison against the following sequences of MTB complex and NTM strains available in the GenBank database and specificity was found to be 100%.
Source: Himedia Laboratories Private Limited
MTB Mycobacterium tuberculosis H37Ra, H37Rv, H37RvSiena, (Zopf 1883) Lehmann and Neumann 1896, Mycobacterium tuberculosis complex sp. N0072, Mycobacterium tuberculosis strain 1-19, 2.2.1, H-19-0008, H-20-0024, N1015 Mycobacterium bovis AF2122/97, BCG str. Tokyo 172, BCG strain Moreau PL, BCG SL 222 Sofia, BCG strain Russia 368, BCG str. Moreau RDJ, BCG str. Tokyo 172 Mycobacterium africanum strain 25, UT307, GM041182, Mycobacterium microti strain 12, OV254, Reed 1957 Mycobacterium caprae strain Allgaeu Mycobacterium canetti strain ET1291 Mycobacterium orygis strain NIAB_BDWBCSHFL_1, strain MUHC/MB/EPTB/Orygis/51145 NTM Mycobacterium avium complex (MAC), M. Abscessus, M. Kansasii, M. Intracellulare, M. Scrofulaceum, M. Fortuitum complex, M. Malmoense , M. Interjectum, M. Gordonae, M. Flavescens, M. Chelonae, M. Simiae, M. Gastri, M. Smegmatis, M. Avium, M. Celatum, M. Terrae complex, M. Xenopi, M. Marinum, M. Phlei, M. Vaccae, M. Ulcerans, M. Tusciae, M. Triplex, M. Septicum, M. Mucogenicum, M. Asiaticum, M. Intermedium, M. Chimaera, M. Senegalense, M. Parascrofulaceum, M. Toakiense, M. Haemophilum, M. Aurum, M. Thermoresistable, M. Aichiense, M. Thermophilum, M. Neoaurum, M. Kubicae, M. Bohemicum, M. Shimoidei, M. Rhodesia, M. Florentinum, M. Hiberniae, M. Mucogenicum, M. Colombiense, M. Wolinsky , M. Longobardum, M. Nonchromogenicum Analytical reactivityThe analytical reactivity of the Hi-PCR® MTB/NTM Probe PCR Kit was confirmed through wet lab testing of the oligonucleotides (primers and probes) against commercial controls for MTB and NTM.
This testing included Quantitative Genomic DNA from Mycobacterium tuberculosis strain H37Ra (ATCC 25177DQ), Quantitative Genomic DNA from Mycobacterium tuberculosis variant bovis BCG strain TMC 1011 (ATCC 35734D), and Quantitative Genomic DNA from Mycobacterium avium subsp. Paratuberculosis strain K-10 (ATCC BAA-968D).
Additionally, it involved Genomic DNA from Mycobacterium abscessus strain L948 (ATCC 19977D-5), Quantitative Genomic DNA from Mycobacterium microti (ATCC 19422DQ), Genomic DNA from Mycobacterium gordonae strain TMC 1327 (ATCC 35760D-5), Genomic DNA from Mycobacterium marinum strain M (ATCC BAA-535D-5), and Genomic DNA from Mycobacterium smegmatis strain mc(2)155 (ATCC 700084D-5).
Figure 3. Image representing probe based Real-Time amplification plots of ATCC standards (MTB and NTM) confirmed by Hi-PCR® MTB/NTM Probe PCR kit on Applied Biosystems Quant Studio 5 Real Time PCR System. Image Credit: Himedia Laboratories Private Limited
Cross-reactivity and interference with other microorganismsWet testing was conducted against commercial genomic or synthetic DNA/RNA of the pathogens listed in the following table, using the Applied Biosystems Quant Studio 5, to assess any potential cross-reactivity. None of the tested pathogens displayed reactivity to the primers and probes of the Hi-PCR® MTB/NTM Probe PCR Kit.
Source: Himedia Laboratories Private Limited
Influenza A virus (H3N2) strain A/Wisconsin/15/2009 (VR-1882DQ) Corynebacterium diphtheriae strain NCTC 13129 (700971D-5) Human coronavirus 229E (ATCC VR-740DQ) Haemophilus influenzae (51907DQ) Human metapneumovirus hMPV RNA (ATCC VR-3250SD) Pseudomonas aeruginosa strain PAO1-LAC (47085DQ) Enterovirus 68 strain Fermon (ATCC VR-1826) Staphylococcus aureus subsp. Aureus (43300DQ) Human parainfluenza virus 1 strain C35 (ATCC VR-94DQ) Chlamydophila pneumoniae strain CM-1 (1360DQ) Human parainfluenza virus 3 strain C 243 (ATCC VR-93DQ) Mycoplasma pneumoniae strain M129-B7 (29342DQ) Human respiratory syncytial virus strain 18537 (ATCC VR-1580DQ) Legionella pneumophila subsp. Pneumophila (33152DQ) Influenza B virus (ATCC VR-1804DQ) Bordetella pertussis (9797DQ) Influenza A virus (H1N1) strain A/PR/8/34 (ATCC VR-1469DQ) Candida albicans strain SC5314 (MYA-2876DQ) Human coronavirus NL63 RNA (ATCC VR-3263SD) Aspergillus niger strain A1144 3528.7 (1015DQ) Measles virus strain Edmonston (VR-24D) Aspergillus flavus strain SN 3 (9643DQ) Human adenovirus 1 strain Adenoid 71 (VR-1DQ) Streptococcus pyogenes strain Bruno (19615DQ) Human parainfluenza virus 2 strain Greer (VR-92DQ)Cross-reactivity analysis – In silico
The sequences of the oligonucleotides (primers and probes) utilized in the Hi-PCR® MTB/NTM Probe PCR Kit underwent BLAST (Basic Local Alignment Search Tool) analysis against the organisms shown in the table below. The in-silico analysis revealed no significant cross-reactivity for any of the evaluated sequences.
Source: Himedia Laboratories Private Limited
Epstein Barr virus (taxid:10376) Klebsiella pneumoniae (taxid:573) Human bocavirus (taxid:329641) Streptococcus pyogenes (taxid:1314) Rhinoviruses (taxid:12059) Streptococcus group G (taxid:1320) Cytomegalovirus (taxid:10358) Escherchia coli (taxid:562) VZV (taxid:10335) Moraxella catarrhalis (taxid:480) Herpes simplex virus 1 (taxid:10298) Haemophilus parainfluenzae (taxid:729) Herpes simplex virus 2 (taxid:10310) Corynebacterium diphtheriae (taxid:1717) Severe acute respiratory syndrome coronavirus (taxid:694009) Corynebacterium ulcerans (taxid:65058) MERS-CoV (taxid:1335626) Salmonella (taxid:590) Human Parainfluenza Virus-4 (taxid:2560526) Bordetella pertussis (taxid:520) Measles morbillivirus (taxid:11234) Legionella pneumophila (taxid:446) SARS-CoV-2 (taxid:2697049)
The precision of the Hi-PCR MTB/NTM Probe PCR Kit was evaluated across various conditions, including:
Variability data were assessed in terms of standard deviation (SD) and coefficient of variation (CV) based on threshold cycle (Ct) values. Total variability was determined by combining results from all five types of variability analyses.
Table 3. Data showing variability observed from Precision (repeatability and reproducibility) studies. Source: Himedia Laboratories Private Limited
Repeatability and Reproducibility data Variability Mean (Ct) MTB NTM IC Intra-assay SD 0.133 0.19 0.09 %CV 0.53 0.74 0.34 Mean (Ct) 24.82 24.76 26.23 Inter-assay SD 0.71 0.45 0.19 %CV 2.94 1.87 0.72 Mean (Ct) 24.11 24.0 26.12 Inter-Day SD 0.79 0.46 0.05 %CV 3.26 1.91 0.2 Mean (Ct) 24.16 24.04 26.23 Inter-Operator SD 0.057 0.004 0.04 %CV 0.22 0.0 0.15 Mean (Ct) 24.88 24.76 26.24 Inter-Instrument SD 3.22 0.36 1.45 %CV 14.06 1.45 7.48 Mean (Ct) 22.89 24.76 24.57 Inter-lot SD 0.18 0.06 0.69 %CV 0.74 0.24 0.03 Mean (Ct) 24.41 24.74 26.62 Total variability SD 0.76 0.38 26.0 %CV 3.12 1.54 0.72 Mean (Ct) 24.33 24.51 26Clinical performance evaluation
The performance of the Hi-PCR MTB/NTM Probe PCR Kit was evaluated using clinical specimens to confirm aspects of assay performance. A total of 40 clinical samples were assessed and compared with a Reference CE-IVD PCR Multiplex Kit. Bacterial nucleic acids were extracted using the HiPurA® Pre-filled Plate for MTB DNA Purification (Cat no: MB579MPF16). Results for MTB are illustrated in the table below.
Table 4. Table representing Sensitivity, Specificity, PPV and NPV data of the Hi-PCR® MTB/NTM Probe PCR Kit. Source: Himedia Laboratories Private Limited
Value 95%CI Diagnostic sensitivity 100% 81.5-100% Diagnostic specificity 100% 78.1-100% Positive Predictive Value 100% 81.5-100% Negative Predictive Value 100% 78.1-100%Case study
DNA extracted from an MTB-positive sample was serially diluted at ratios ranging from 1:10 to 1:1000 to simulate samples with low target concentrations. These diluted samples were tested using the Hi-PCR® MTB/NTM Probe PCR Kit. The results showed that even samples with low concentrations of the target gene were successfully detected as positive, with the generated Ct values remaining within the cutoff threshold for detection.
Figure 4. Image showing amplification of Sample 8 and its dilution series (1:10-1:1000) with the corresponding Ct values confirmed by Hi-PCR® MTB/NTM Probe PCR kit on Applied Biosystems Quant Studio 5 Real Time PCR System. Image Credit: Himedia Laboratories Private Limited
ConclusionThe Hi-PCR MTB/NTM Probe PCR Kit is a highly effective tool for the rapid and accurate identification and differentiation of Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM).
Its exceptional sensitivity, specificity, and user-friendliness make it an indispensable resource for healthcare providers, public health officials, and researchers in combating tuberculosis and related infections. By facilitating prompt diagnoses and informed decision-making, this kit plays a crucial role in managing outbreaks, improving patient outcomes, and supporting global efforts to control and prevent tuberculosis.
About Himedia Laboratories Private LimitedWith a presence in more than 150 countries, HiMedia is amongst the top three brands in the Bioscience Industry.
HiMedia Laboratories Private Limited is world renowned for manufacturing high quality culture media for microbiology. Additionally, we provide advanced media and products in the fields of Molecular Biology, Cell Biology, Plant Tissue Culture, Chemicals and Lab Aids/Equipment. As a Top Tier Global player, we are not only dedicated towards products but also striven towards introducing technologies such as Genomics Sequencing Services and Hydroponics.
HiMedia has managed to do this over decades as we have our own in-house bulk raw materials manufacturing plant. This enables us to deliver consistent quality products that conform to ISO 9001:2015 and ISO 13485:2012 and WHO: GMP.
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The 'Molecular Biology and Virology Division' of HiMedia Laboratories Pvt. Ltd. Also called as HiGenoMB® is a One Stop Solution Provider churning out potential Research and Industry oriented Molecular biology products for the past glorious decade. About 2000 different products such as Nucleic Acid Extraction and Amplification (PCR) Kits, Cloning Reagents, Buffers & Chemicals for proteomics studies, Automated Molecular Instrumentation including RT PCR machines and PCR thermal cyclers and DNA/RNA Extraction platforms are being produced. The Proficient researchers in this department are spear heading the challenging field of Molecular Diagnostics to provide a complete solution for clinical diagnosis, agriculture, veterinary sciences, food industry, drug discovery and forensic medicine with the use of Real Time PCR or quantitative PCR kits and thermal cyclers. Our Molecular Biology Division-has established an in-house Advanced Sequencing and Bioinformatics facility which marks HiMedia's entry into the Services space.
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Daily Shower With A Face Full Of PathogensColorado Arts & Sciences ...
While daily bathroom showers provide invigorating relief and a good cleansing for millions of Americans, they also can deliver a face full of potentially pathogenic bacteria, according to a surprising new University of Colorado at Boulder study.
The researchers used high-tech instruments and lab methods to analyze roughly 50 showerheads from nine cities in seven states that included New York City, Chicago and Denver. They concluded about 30 percent of the devices harbored significant levels of Mycobacterium avium, a pathogen linked to pulmonary disease that most often infects people with compromised immune systems but which can occasionally infect healthy people, said CU-Boulder Distinguished Professor Norman Pace, lead study author.
It's not surprising to find pathogens in municipal waters, said Pace. But the CU-Boulder researchers found that some M. Avium and related pathogens were clumped together in slimy "biofilms" that clung to the inside of showerheads at more than 100 times the "background" levels of municipal water. "If you are getting a face full of water when you first turn your shower on, that means you are probably getting a particularly high load of Mycobacterium avium, which may not be too healthy," he said.
The study appeared in the Sept. 14 online edition of the Proceedings of the National Academy of Sciences. Co-authors of the study included CU-Boulder researchers Leah Feazel, Laura Baumgartner, Kristen Peterson and Daniel Frank and University Colorado Denver pediatrics department Associate Professor Kirk Harris. The study is part of a larger effort by Pace and his colleagues to assess the microbiology of indoor environments and was supported by the Alfred P. Sloan Foundation.
Research at National Jewish Hospital in Denver indicates that increases in pulmonary infections in the United States in recent decades from so-called "non-tuberculosis" mycobacteria species like M. Avium may be linked to people taking more showers and fewer baths, said Pace. Water spurting from showerheads can distribute pathogen-filled droplets that suspend themselves in the air and can easily be inhaled into the deepest parts of the lungs, he said.
Symptoms of pulmonary disease caused by M. Avium can include tiredness, a persistent, dry cough, shortness of breath, weakness and "generally feeling bad," said Pace. Immune-compromised people like pregnant women, the elderly and those who are fighting off other diseases are more prone to experience such symptoms, said Pace, a professor in the molecular, cellular and developmental biology department.
The CU-Boulder researchers sampled showerheads in homes, apartment buildings and public places in New York, Illinois, Colorado, Tennessee and North Dakota.
Although scientists have tried cell culturing to test for showerhead pathogens, the technique is unable to detect 99.9 percent of bacteria species present in any given environment, said Pace. A molecular genetics technique developed by Pace in the 1990s allowed researchers to swab samples directly from the showerheads, isolate DNA, amplify it using the polymerase chain reaction, or PCR, and determine the sequences of genes present in order to pinpoint particular pathogen types.
"There have been some precedents for concern regarding pathogens and showerheads," said Pace. "But until this study we did not know just how much concern."
During the early stages of the study, the CU team tested showerheads from smaller towns and cities, many of which were using well water rather than municipal water. "We were starting to conclude that pathogen levels we detected in the showerheads were pretty boring," said Feazel, first author on the study. "Then we worked up the New York data and saw a lot of M. Avium. It completely reinvigorated the study."
In addition to the showerhead swabbing technique, Feazel took several individual showerheads, broke them into tiny pieces, coated them with gold, used a fluorescent dye to stain the surfaces and used a scanning electron microscope to look at the surfaces in detail. "Once we started analyzing the big metropolitan data, it suddenly became a huge story to us," said Feazel, who began working in Pace's lab as an undergraduate.
In Denver, one showerhead in the study with high loads of the pathogen Mycobacterium gordonae was cleaned with a bleach solution in an attempt to eradicate it, said Pace. Tests on the showerhead several months later showed the bleach treatment ironically caused a three-fold increase in M. Gordonae, indicating a general resistance of mycobacteria species to chlorine.
Previous studies by Pace and his group found massive enrichments of M. Avium in "soap scum" commonly found on vinyl shower curtains and floating above the water surface of warm therapy pools. A 2006 therapy pool study led by Pace and CU-Boulder Professor Mark Hernandez showed high levels of M. Avium in the indoor pool environment were linked to a pneumonia-like pulmonary condition in pool attendants known as "lifeguard lung," leading the CU team into the showerhead study, said Pace.
Additional studies under way by Pace's team include analyses of air in New York subways, hospital waiting rooms, office buildings and homeless shelters. Indoor air typically has about 1 million bacteria per cubic meter and municipal tap water has rough 10 million bacteria per cubic meter, said Pace.
So is it dangerous to take showers? "Probably not, if your immune system is not compromised in some way," said Pace. "But it's like anything else -- there is a risk associated with it." Pace said since plastic showerheads appear to "load up" with more pathogen-enriched biofilms, metal showerheads may be a good alternative.
"There are lessons to be learned here in terms of how we handle and monitor water," said Pace. "Water monitoring in this country is frankly archaic. The tools now exist to monitor it far more accurately and far less expensively that what is routinely being done today."
In 2001 the National Academy of Sciences awarded Pace the Selman Waxman Award -- considered the nation's highest award in microbiology -- for pioneering the molecular genetic techniques he now uses to rapidly detect, identify and classify microbe species using nucleic acid technology without the need for lab cultivation. That same year he was awarded a MacArthur Foundation "genius grant" for his work.
A video news release on the showerhead and pathogen study is available at www.Colorado.Edu/news.
By Jim ScottOffice of News ServicesThis originally appeared on the news services site
Sept. 14, 2009
NTM Lung Infections - News-Medical.net
An interview with Dr Michael Loebinger conducted by April Cashin-Garbutt, MA (Cantab)
What are nontuberculous mycobacteria (NTM) and where are they found?Nontuberculous mycobacteria are part of a group of bacteria called mycobacteria. The non-tuberculous mycobacteria are, as the name suggests, mycobacteria that are not tuberculosis. They're also not leprosy, but they are the other members of the bacteria group termed mycobacteria.
NTM are ubiquitous in that they are found throughout the world in the environment; particularly in water and soil.
© Life science of anatomy / Shutterstock.Com
Are there different types of NTM? Which are most common?There are many different types of NTM. The actual number of individual species, or types of NTM, increases continually as the sophistication of our diagnostic and identification techniques increase. At the moment, there are over 170 species that have been identified, although only a relative minority of those cause disease in humans.
The most common types which can affect humans and cause disease are:
There are others which are commonly found but cause disease less often, or not at all, these include Mycobacterium fortuitum and Mycobacterium gordonae.
Often, mycobacteria are classified into fast-growers (i.E. When you culture them in a laboratory they grow up quickly) or slow-growers (i.E. The opposite happens when you grow them in a laboratory and they can take quite a long time to culture them up).
How do NTM affect the body?NTM normally don't affect the body. NTM are everywhere in the environment and they're not a particularly virulent organism. Most people are exposed to them all the time and don't get affected by them.
Some of the species in some people can cause disease. It can cause disease in a variety of different places, but by far the most common manifestation is pulmonary disease.
How many people are thought to be affected by NTM lung infections?That's quite a difficult question because we don't know if people are affected by NTM lung infections for certain unless we actually test them for it and that isn't always done. But the published literature suggests that somewhere between 1.4 and 40 per hundred thousand people are infected by NTM pulmonary disease.
This varies with the type of person and is much higher in certain groups. It also varies in different locations as some areas of the world have a much larger problem with NTM pulmonary disease compared to others.
One recent study in the US looked at older patients, patients over 65, and looked at period prevalence (i.E. The amount of patients that had pulmonary NTM over this 11-year period), and in this study they found over 100 per 100,000.
What are the main risk factors and who is most at risk?As I mentioned, NTM are ubiquitous, they're everywhere and most people aren't affected by them. There needs to be an interaction between the host and the microbe itself in order to cause disease.
Either you have a particularly susceptible host or you have a particularly virulent microbe, or the environment is such that there is quite a high burden of the organism.
In certain areas of the country and of the world, there is an increased risk and these are thought to be places with high humidity, near the sea. In the United States where lots of this work is being done, states such as Hawaii, Florida, California, have particularly high prevalence of nontuberculous mycobacteria.
There was also a study in Europe which suggested that where you lived didn't just make you more likely to get NTM, but also related to the type or the species of NTM you were more likely to get.
Finally, with regards to the environment, there are some case-control studies which look at environmental exposures comparing people with NTM to people without NTM. In some studies, it was shown that people with NTM have had increased exposures to soil or to water sources.
Another main type of risk factor is the host. Certain aspects of the host make it much more likely to get NTM pulmonary disease. The main risk factor is chronic lung disease, so people that already have a long-standing lung condition and within that group, bronchiectasis and cystic fibrosis are the most common underlying comorbodities. Other underlying causes such as COPD (chronic obstructive pulmonary disease) also make NTM pulmonary disease much more likely.
Also interestingly, there is a group of patients that seem to be at risk and more susceptible to NTM without any obvious long-standing lung conditions and these patients tend to be over represented by post-menopausal women who are taller and thinner on average, commonly with chest wall deformities. The actual reason for this is unknown, but may berelated to mucous clearance
Finally, there has been a lot more research looking into other possible risk factors within the host, including some types of immunodeficiency.
Is it true that NTM lung infections are increasing worldwide in both men and women? What are the likely reasons why?I think it is true. There has been studies from many different parts of the world and all of them seem to suggest that it is increasing worldwide. Studies that have put numbers on this suggested an annual increase somewhere between 3 to 8 percent per year.
We've also found at the Royal Brompton Hospital, a tertiary respiratory hospital in the UK, where I work, a significant increase in the number of patients which have had nontuberculous mycobacteria over the last decade or so.
For example, we recently published that there was an increase in the number of NTM isolates from 137 in the year 2000 to 759 in the year 2013.
Why is it increasing? Well some of that is increased recognition. Exposure at conferences and also the publication of articles have increased the knowledge of NTM and hence, people are testing for it more often. I said back to the beginning, if you don't test for it, then you don't find it and because there is more appreciation of it, people are testing more for it.
However, that's not the whole picture. There was a nice study done a few years ago now, which looked at an American population. They did ahealth survey of civilians both in the early 1970s and also in the turn of the millennium.
As part of this study, they used a small amount of antigen, which is the proteins of one of these NTM compounds, and injected it just under the skin. This is similar to TB testing that many people have had.
The study showed that there was an increase in the number of patients that responded to NTM from the 1970s to 2000s. This shows that there is an increased exposure to these NTMs over this period of time. That is more than just increased recognition. That means that people are being exposed to the NTM more over this period of time.
Why is there more disease? Well, as I keep going to back to, it's an interaction between the host and the bug. The population (host) is getting older. There are an increased number of people with chronic lung disease and underlying diseases. We are getting better at treating other diseases, but we are using drugs which suppress the immune system, which can give bugs more of a chance.
We have also got better at killing other bugs and so NTM have less competition and there is increased chlorination of water supplies and increased hygiene. Also, interestingly, the interaction between the host and the pathogen has changed over the last 20 years. There is an increased amount of showering. We know that these bugs go around in water sources and that they can be around in shower heads.
The increased popularity of showers of the last few decades have also presented mycobacteria to the host in a different manner. Whether that is important again, at the moment it is probably just conjecture. There is also more immigration and environmental contact, so the chance of patients going to areas where NTM are much more prevalent. There are lots of possible reasons.
How is NTM lung infection diagnosed? What are the main challenges with NTM lung infection diagnosis?The main diagnosis for lung infection is detecting or culturing the mycobacteria or the NTM in the respiratory secretions, so predominantly by sputum tests.
The issue is that they are everywhere and hence finding these microbes in the sputum is not that uncommon. The challenge is deciding on whether it is important or not. Finding it in the sputum may just be an isolated finding, it may be a contaminant from the environment, and not actually represent any problem for the individual.
Additionally, to make things even more difficult, these bugs don't always cause problems. Even if they actually do represent an infection in an individual, sometimes they can live happily in the pulmonary system without actually causing any problems.
Finally, the final group could be that they are actually causing a significant amount of disease and causing problems. The problems with diagnosis are that, an isolate culture of mycobacteria could represent a contaminant, casual isolate, an infection which doesn't cause the individual problem, or actually pulmonary disease.
How these are all sorted out is, is helped by the publication of the American Thoracic Society Diagnostic Criteria which came out in 2007. They stressed that you need two positive cultures of the same species from the same organism.
Additionally, you need symptoms and changes on an x-ray or CT scan which relate to disease, which would separate our infection from the disease. There are various criteria that people follow to actually decide if somebody has NTM lung infection or disease.
How do you decide who to treat?Firstly, the criteria are obviously important for decisions to treat. Treatment shouldn't be given for casual isolate or contaminant. Most people wouldn't treat an infection that is not causing any damage and that doesn't have any symptoms or radiographic change.
But, still it is not as simple as saying everyone with evidence of NTM disease needs treatments. This is partly because of the fact that it can be quite an indolent infection and actually if you follow patients for some time then often they can remain relatively stable with relatively few symptoms, so the treatment may not be necessary.
Additionally, the situation is further complicated by the fact that, as I mentioned, a lot of these patients have underlying diseases and underlying chronic lung conditions. Since symptoms of the under lung conditions present often very similar to the symptoms of NTM lung disease can cause for example: cough, sputum and exacerbations.
Actually untangling the contribution from the NTM to the underlying chronic lung disease can be quite difficult. It is important to try and do that before determining whether treatment for the NTM is necessary.
This is important because treatment of NTM is difficult. Whereas for a normal lung infection it would just be a short course of antibiotics which would normally get rid of the infection, for NTM lung disease, antibiotics are needed for long periods of time, over a year and additionally multiple different antibiotics at the same time which can cause significant problems with tolerance.
On top of that, cure is not guaranteed and certainly with certain species and certain elements of lung disease a cure may not be possible.
Why is cure not always the aim?Firstly, you may not want to treat it and that relates back to the previous question. If you decide that treatment is important and you go on and treat, cure may not always be possible.
This is a difficult condition. In some studies, a cure can be anywhere between 13% to 90% depending on the amount of lung disease, the type of species and patient factors as well. Additionally, mortality can be relatively high with these conditions.
Depending on the species and the patient and the amount of lung disease, some studies have shown that all cause of mortality over a 5-year period can be as high as 40%.
When you start treatment in an individual, often you will be trying to cure and get rid of the microbe. In some patients, either due to a lack of tolerance to drugs or a lack of efficacy of drugs, or the fact that the disease is too severe, the aim may be actually to try and control and keep the patient stable with the knowledge that you may not actually get rid of the bug, but you may prevent further lung damage.
What research is currently being conducted on NTM and what more needs to be done to improve understanding of the condition?There is research that is being done throughout the world looking at all the different facets of NTM disease and trying to improve our understanding in the areas where there are gaps. There is research that is looking at why people are susceptible to NTM.
We ourselves have looked at gene expression analysis to have a look if there are any clues there and also other studies have looked at underlying genetics to see if there are any groups of individuals which are more likely to get nontuberculous mycobacteria.
In addition to that, there is research which is assessing different treatment regimens and modes of treatments and different treatment options. There is presently a Phase III study going on looking into a new inhaled drug for possible future treatment of difficult NTM disease.
What do you think the future holds for patients with NTM?I think NTM treatments is difficult. I think it is something that is increasing at the moment and we don't have all the tools available to adequately treat these patients. There are issues knowing who to treat, knowing when to treat and knowing what to treat with.
I am encouraged by the fact that there is a significant increase in interest both from academia, but also from the pharmaceutical industry. It is really the combination of the two which is important to really drive through developments in NTM.
I am quite hopeful that over the next ten years or so we will understand a little bit more about it and hopefully have more tools and more drugs available for treatment.
Where can readers find more information?There are American Thoracic Society guidelines which are published: https://www.Thoracic.Org/statements/tuberculosis-pneumonia.Php
Also about to be published are new British Thoracic Society guidelines of the treatment and management of nontuberculous mycobacteria pulmonary disease, which basically is a critical appraisal of all the available literature, excellentfor interested health care professionals.
They would probably the two main areas of comparative knowledge. There are also lots of different review articles that are available on the internet.
About Dr Michael LoebingerDr. Michael Loebinger is a Consultant Respiratory Physician at the Royal Brompton Hospital with a specialist interest in respiratory infections. He chairs the infection special advisory group for the BTS, co-chairs the BTS bronchiectasis guideline committee and is on the steering committee for the BTS non-tuberculous mycobacteria and ERS bronchiectasis guidelines. He is a founding member of the UK and European clinical and research bronchiectasis networks and sits on the ERS Respiratory Infection Education task force. He also holds an honorary senior lecturer position at Imperial College and supervises PhD, MSc and medical students.
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