Nontuberculous Mycobacteria Isolation Rates Research Articles

Epidemiology of Nontuberculous Mycobacteria in Tuberculosis suspects, Southwest of China, 2017-2022.

This study summarizes the epidemiological characteristics, species distribution, and drug sensitivity of clinical nontuberculous mycobacteria (NTM) isolates at the Public Health Clinical Center of Chengdu, China, from January 2017 to December 2022. We retrospectively analyzed data from patients with clinically isolated NTM strains. Chi-square analysis assessed the rate of Mycobacterium strain isolation over 6 years. The number of samples tested for Mycobacterium tuberculosis (MTB) and/or NTM increased each year, while MTB detection decreased and NTM detection rose significantly each year (P=0.03). The average age of NTM patients was 51 ± 17.53 years, with a 14.1% HIV infection rate. The predominant isolates were Mycobacterium avium-intracellulare (MAC) and M. chelonae/M. abscessus, with 96.4% of cases being of Han ethnicity. Amikacin, moxifloxacin, and clarithromycin were effective against M. avium and M. intracellulare; linezolid, amikacin, and cefoxitin were effective against M. chelonae/M. abscessus. Over 90% of NTM cases originated from the respiratory tract. The NTM isolation rate in Southwest China has risen in recent years, primarily among elderly patients with a high HIV co-infection rate. The main NTM isolates were MAC and M. chelonae/M. abscessus. Amikacin, moxifloxacin, clarithromycin, and linezolid exhibited strong antibacterial activity against SGM, while amikacin and linezolid displayed relatively better antibacterial activity against RGM. The prevalence of NTM infection may be positively associated with regional economic development and health conditions.

A comparative analysis of molecular genotypes of Mycobacterium tuberculosis isolates from HIV-positive and HIV-negative patients.

SettingTuberculosis Research Laboratory, Division of Clinical Microbiology and Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, and the National Institute of Tuberculosis and Respiratory Diseases (NITRD), both situated in New Delhi.ObjectivesWe aimed to identify the distribution of various genotypes of M. tuberculosis among HIV-positive and HIV-negative patients suspected of having Tuberculosis, seen at the National Institute of Tuberculosis and Respiratory Diseases, New Delhi, which is a tertiary care dedicated TB hospital.Patients and methodsGenotyping by Spoligotyping and 24 loci MIRU-VNTR was performed and analyzed using SITVITWEB and MIRU-VNTRplus. Drug susceptibility patterns were also analyzed.ResultsA total of 503 subjects who were PTB/EPTB suspected were recruited and 287 were culture positive. Among them, 276 had growth of Mycobacterium tuberculosis (MTB) and in 11 patients non-tuberculous mycobacteria (NTM) were grown. The isolation rate of NTM was predominantly from HIV positive [10 of 130 (7.6%)] patients. Of the total isolates of MTB, 156 (56.5%) were from HIV negative patients and 120 (43.5%) were from HIV positive patients. All 276 M. tuberculosis isolates were genotyped and tested for drug susceptibility patterns. The CAS genotype was most predominant [153 (55.4%)], followed by Beijing lineage [44 (15.9%)], East African India [25 (9.1%)] and others [54 (19.6%)]. Beijing genotype was significantly more common in HIV positive patients (22.5%) than in HIV negative patients (10.9%). In MIRU-VNTR analysis, clustering was found to be more frequent in CAS strains irrespective of HIV status. In the HIV positive group, spoligotyping could differentiate various genotypes in 90% of isolates and MIRU-VNTR analysis in 84.2% of isolates. The clustering of various MTB strains was more associated with drug resistance.ConclusionThe Beijing lineage was predominant in HIV-TB coinfected cases, even though the Central Asian Strain (CAS) was overall more predominant in the region.

Doubled Nontuberculous Mycobacteria Isolation as a Consequence of Changes in the Diagnosis Algorithm.

BackgroundNontuberculous mycobacteria (NTM) and their associated diseases remain neglected. Through minor modifications in our diagnostic algorithm, we observed an unexpected higher number of cultivable NTM isolates. Therefore, a retrospective study was performed thoroughly to investigate the effect of changed laboratory procedures on NTM isolation in a specialized tuberculosis hospital.MethodsNTM isolation rates and composition of NTM species were compared for the two diagnostic algorithms: (1) by using traditional p-nitrobenzoic acid (PNB) selective medium as a preliminary test to identify NTM isolates among the positive cultures (procedure I) and (2) by using the MPT64 antigen detection method to distinguish between Mycobacterium tuberculosis complex (MTBC) isolates and possible NTM isolates after a positive MGIT960 liquid culture (procedure II).ResultsThe NTM isolation rate in procedure II was significantly higher than the procedure I (18.08% vs 9.71%; P<0.001). A noticeable increase in the ratio of NTM isolates among the identified mycobacteria was observed over the studied years (ie, from 58.18% in 2019 to 72.93% in 2021), which indicated a more precise prescription of species identification test after prompt information was provided in procedure II. In addition, the consistency of the identified species using multiple specimens from the same patient did not present a significant difference between the procedures.ConclusionAccording to our study, NTM infection might be far more underestimated than it is. A diagnostic procedure combining MGIT960 culture and MPT64 antigen detection could timely and easily identify clues of NTM isolates and improve the diagnosis of NTM infections.

Increasing Trend of Nontuberculous Mycobacteria Isolation in a Referral Clinical Laboratory in South Korea.

Background and Objectives: Nontuberculous mycobacteria (NTM) infections are increasing worldwide. We evaluated the annual trends of NTM isolation on acid-fast bacillus (AFB) culture, compared to that of Mycobacterium tuberculosis, and the distribution of NTM species nationwide in South Korea. Materials and Methods: The study was conducted in a diagnostic center that is a major referral laboratory for the diagnosis of tuberculosis and NTM in South Korea. All laboratory results of AFB culture from January 2014 to December 2019 were collected. All NTM identified were definitively identified to the species level. Results: A total of 345,871 tests were performed for the diagnosis of mycobacteria. The isolation rate of NTM and M. tuberculosis was 3.7% (12,969 cases) and 4.4% (15,081 cases), respectively. The annual isolation rate of NTM increased gradually from 2.7% in 2014 to 4.8% in 2019, whereas that of M. tuberculosis decreased from 6.2% to 3.3%. There were 4988 cases of NTM identified to the species level. M. avium complex (MAC) was the most common species isolated from pulmonary sites (59.8%), followed by M. gordonae (9.2%), M. abscessus (7.0%), and M. fortuitum (5.5%). Extrapulmonary NTM were identified in 29 cases (0.6%). MAC was also the most common NTM species isolated from extrapulmonary sites (65.5%), followed by M. kansasii (10.3%), M. abscessus (6.9%), and M. fortuitum (6.9%). Conclusions: The annual isolation rate of NTM has increased gradually, whereas that of M. tuberculosis has decreased. Follow-up studies of the increases in NTM identification and NTM infections in South Korea are needed.

Epidemiology of Non-Tuberculous Mycobacteria isolated from clinical specimens in Madrid, Spain, from 2013 to 2017.

The epidemiology of non-tuberculous mycobacteria (NTM) in Spain is largely unknown because systematic reporting is not compulsory. The aim of our study was to describe the frequency and diversity of NTM species in our region and their distribution according to the source sample, gender, and age of the patients. We performed a multicenter study of all NTM isolated in 24 public hospitals in Madrid from 2013 to 2017. A total of 6.923 mycobacteria were isolated: 4535 (65.5%) NTM, and 2.388 (34.5%) Mycobacterium tuberculosis complex (MTB). Overall, 61 different NTM species were identified. The most frequently isolated species were Mycobacterium avium complex (47.7%), M. lentiflavum (12.2%), M. gordonae (9.2%), M. fortuitum (8.9%), and M. abscessus (3.9%). Whereas MTB cases were stable during the study period, the number of NTM isolates increased considerably from 930 isolates in 2013 to 1012 in 2017; a sharp increase occurred in the last year. The rise in NTM isolates was mostly due to M. lentiflavum, M. kansasii, and M. abscessus mainly isolated from respiratory specimens in patients older than 60. The increase in isolation rate of NTM in our region is consistent with the increasing rates reported worldwide in the last decades. The rise in NTM isolates was mainly attributed to M. lentiflavum but it also should be noted the increasing of species with high pathogenic potential such as M. kansasii and M. abscessus.

Increasing Prevalence of Nontuberculous Mycobacteria in Respiratory Specimens from US-Affiliated Pacific Island Jurisdictions1.

Nontuberculous mycobacteria (NTM) respiratory infections represent a growing public health problem in many countries. However, there are limited published epidemiologic studies for the Western Pacific region. We reviewed respiratory specimens submitted to Diagnostic Laboratory Services in Hawaii, USA, for culture of Mycobacterium tuberculosis during August 2007–December 2011 to determine the NTM isolation rate. We observed a statistically significant increase in the rate of specimens with NTM isolated in respiratory culture (adjusted rate ratio per year 1.65, 95% CI 1.54–1.77; p<0.01). In contrast, the number of patients with respiratory cultures positive for M. tuberculosis showed no increase (adjusted rate ratio per year 0.98, 95% CI 0.94–1.01; p = 0.19). A 6-month subset of NTM isolates was identified by using a nucleic acid probe or 16S rRNA sequencing. M. avium complex and M. fortuitum were the most common NTM identified.

Extrapulmonary infections associated with nontubercular mycobacteria in immunocompetent patients: A study of two cases

Nontuberculous mycobacteria (NTM) or atypical mycobacteria are abundantly found in the environment. Extrapulmonary infections are most commonly caused by Mycobacterium chelonae, Mycobacterium fortuitum, Mycobacterium avium, and Mycobacterium kansasii. Risk factors for infection include both accidental/surgical trauma, all procedures involving implants, retained biomaterial. The isolation rate of NTM from India has been reported ranging from 0.5% to 8.6%. We report two culture-proven cases of infection caused by NTM. The present cases emphasize the importance of considering NTM in the differential diagnosis of nonhealing ulcers whether corneal or skin and soft tissue infections. The following core competencies are addressed in this article: Medical knowledge, Patient care.

Mycobacterial Prevalence and Antibiotic Resistance Frequency Trends in Taiwan of Mycobacterial Clinical Isolates From 2002 to 2014.

Tuberculosis, caused by Mycobacterium tuberculosis complex (MTBC) infections, is one of the most widespread infectious diseases worldwide. Nontuberculous mycobacteria (NTM) also cause chronic pulmonary infections, however, NTM infection is generally overlooked.This study analyzed the frequencies of MTBC and NTM clinical isolates from 181,132 specimens obtained from patients in Taiwan suspected of having a pulmonary mycobacterial infection from 2002 to 2014. The resistant rates to 4 first-line antibiotics (isoniazid, ethambutol, rifampicin, and streptomycin) of 9079 clinical MTBC isolates were also examined by the modified agar proportion method.Overall, the mycobacterial isolation rate was 8.65%, and this consisted of MTBC isolation rate of 5.01% and NTM isolation rate of 3.63%. The prevalence of MTBC isolates among the identified mycobacterial strains could be seen to decrease significantly from 82.5% in 2002 to 41.18% in 2014. Notably, the corresponding NTM prevalence increased 3.36 fold from 17.54% in 2002 to 58.82% in 2014. The frequencies of MTBC and NTM isolates showed a reciprocal trend with the crossing over occurring in the years 2010 and 2011. Although the resistance rates of the MTBC isolates to isoniazid and streptomycin were relatively stable over the study period, resistance rates of the MTBC isolates against rifampicin and ethambutol fluctuated across the study period. Overall, the incidence of multidrug resistance was relatively consistent at about 1.74%.The diagnosis, identification, and susceptibility tests for NTM should be standardized and integrated into appropriate clinical settings to cope with the increase in NTM infections. In addition, the documentation of the antibiotic resistance rates of MTBC clinical isolates to the antibiotic treatments most often clinically prescribed over a decade provides valuable clues and reference points for effective mycobacterial control.

Increase in non-tuberculous mycobacteria isolated from humans in Tuscany, Italy, from 2004 to 2014.

BackgroundIn Italy, the prevalence of non-tuberculous mycobacteria (NTM) in human infections is largely unknown. Herein, we report the epidemiology of NTM infections in a region of central Italy, Tuscany, over the last 11 years, and provide a review of the recent literature on NTM isolation rates in different geographic regions.MethodsThe complete collection of NTM strains isolated from a total of 42,055 clinical specimens at the Laboratory of Clinical Mycobacteriology of Pisa University Hospital, Italy, from 1 January 2004 to 31 December 2014 was included.ResultsIn our setting, in the period 2004–2014 a total of 147 patients had cultures positive for NTM. The number of NTM isolates increased considerably from five isolates in 2004 to 29 in 2014; a sharp increase occurred in the last 3 years. Overall, 16 NTM species were isolated; the most common were M. avium, M. intracellulare and M. gordonae detected in respectively in 41.5, 14.3 and 11.6 % of NTM patients. In general, NTM isolates were largely prevalent in people older than 60 (57.8 %); patients aged 1–10 year-old almost exclusively yielded M. avium and M. intracellulare. Of the 147 NTM clinical isolates, 76.2 % were from respiratory specimens, 10.9 % from lymph nodes, 2.7 % from blood (yielding exclusively M. avium), and the remaining 10.2 % from other clinical specimens.ConclusionsThe observed increase in NTM isolation rate in our setting is in keeping with the general increase in NTM infections reported worldwide in the past two decades, although the distribution of the NTM prevalent species differs by geographic region.

Distribution of nontuberculous mycobacteria isolated from clinical specimens and identified with DNA sequence analysis

The aims of the study were to perform the identification of nontuberculous mycobacteria (NTM) isolated from different clinical specimens in the Mycobacteriology Laboratory of Celal Bayar University, Manisa (located at Aegean region of Turkey), by DNA sequence analysis, and to discuss the epidemiological aspects of the data obtained. Out of 5122 clinical specimens sent to the laboratory with the initial diagnosis of tuberculosis in the period April 2007 to July 2011, M.tuberculosis complex and NTM were identified in 225 (4.39%) and 126 (2.46%) samples, respectively. DNA sequence analysis by targeting hsp65 and 16S rDNA gene regions was performed on 101 of the NTM strains in Mycobacteriology Laboratory of Ege University, Izmir. DNA sequence analysis data was evaluated using RIDOM and GenBLAST data bases. NTM strains were identified as 40 M.porcinum (39.60%), 36 M.lentiflavum (35.65%), six M.abscessus (5.64%), five M.peregrinum (4.95%), four M.gordonae (3.96%), three M.fortuitum (2.97%), two M.chelonae (1.98%), and one for each M.alvei (0.99%), M.scrofulaceum (0.99%), M.kansasii (0.99%) species. Two strains which were both 95-98% compatible with other mycobacteria in the data bases could not be identified with certainty. Seventy-two (94.73%) strains of M.lentiflavum and M.porcinum, which were the most frequent (75.24%) species in the study, were isolated from bronchoalveolar lavage (BAL) specimens. The remaining 99 strains examined could not be proven as the cause of the disease due to absence of patients' clinical data, whereas two M.abscessus strains isolated from the sputum were considered as the cause of the disease according to the ATS/IDSA criteria. The isolation rate of NTM in 2010 was found significantly higher (5.33%) than previous years. Review of the 2010 data showed that all strains of M.porcinum and M.lentiflavum, which were the most frequently identified strains were isolated from BAL specimens. This situation is in line with the start of using of an automatic bronchoscope washing machine in our hospital in the same year. In conclusion, NTM were isolated in 2.46% of the clinical specimens of the patients with the initial diagnosis of tuberculosis and these strains belonged to 10 different NTM species. The two NTM species most frequently isolated in our study were M.lentiflavum and M.porcinum which are known for their potential to cause human infections and antibiotic resistance. As these strains were mostly isolated in BAL specimens, it is concluded that automatic bronchoscope washing machines and water delivery system in the hospitals should be examined in terms of contamination by NTM. The isolated NTM strains could not be distinguished as the cause of the disease or a contaminant, which is the limiting factor in this study. However, knowing that the environmental mycobacteria can cause hospital infections, the data obtained in this study can contribute to epidemiology of NTM infections in Turkey.

Recent advances on nontuberculous mycobacteria diseases in Asia

The isolation rate of nontuberculous mycobacteria (NTM) species and the prevalence of NTM-associated diseases are on the rise worldwide; however, the species distribution of NTM isolates and the types of diseases caused by NTM species vary from region to region. Treatment of a NTM disease is complicated, and there is no comprehensive guideline regarding the in vitro susceptibility of each antimicrobial agent against NTM. Therefore, appropriate anti-NTM treatment can only be recommended based on individual NTM species and local surveillance studies of anti-NTM resistance. Previous studies on the in vitro susceptibility of Mycobacterium avium complex (MAC) to clarithromycin in some Asian countries have revealed a low rate of resistance to that antimicrobial agent. Thus, a clarithromycin-based anti-MAC regimen should be effective for MAC infections. However, clarithromycin resistance due to the mutation of the 23S rRNA gene in MAC strains has been detected in many countries. Therefore, physicians should avoid monotherapy with clarithromycin and consider the possibility of clarithromycin resistance in patients who do not respond to clarithromycin-based regimens. Rifampicin is the critical component of successful management of Mycobacterium kansasii diseases. Although most M. kansasii isolates are susceptible to rifampicin in Western countries and in Japan, this agent may not work well in Taiwan. Rapidly growing mycobacteria (RGM) is a prevalent NTM group worldwide, particularly in Asia; however, each NTM species in this group may have its own distinct antibiotic susceptibility pattern, and close monitoring of the antibiotic-resistance patterns of RGM is necessary. Most important of all, the in vitro susceptibility may not represent the in vivo activity until the confirmation of the clinical study. Therefore, further investigation of the clinical effectiveness of the anti-NTM agents is warranted.

Significance of NTM infections in Croatia

Nontuberculous mycobacteria (NTM) are environmental, opportunistic pathogens found in soil and water. NTM are adapted for residence in drinking water distribution systems as they are disinfectant-resistant, surface adherent, and able to grow on low concentrations of organic matter. Reports of NTM infections have been increasing over the past two decades. Of the >150 NTM species reported in the literature, some 25 species have been strongly associated with a variety of human diseases, of which the pulmonary NTM disease (PNTM) is the most frequent. The distribution of NTM species differs strongly by region and it is generally accepted that NTM species differ in their clinical relevance. Further, NTM differ strongly in their growth rate, temperature tolerance, and drug susceptibility, making the correct species identification a very important step in the process of diagnosis. Because NTM are environmental bacteria, the diagnosis of PNTM is complex and requires good communication between clinicians, radiologists, and microbiologists. Extensive microbial resistance, often misleading in vitro drug susceptibility patterns, and complicated treatment regimens are just some of the factors adding to the frustration of the clinical management of NTM diseases. To prevent unwarranted diagnoses and treatment of NTM disease as well as unnecessary diagnostic delay, it could be helpful to use separate, more stringent criteria for species of low relevance, and less stringent criteria for species considered to be of high clinical relevance in the local setting, namely: isolation of Mycobacterium kansasii (worldwide) and Mycobacterium malmoense (north-western Europe) from pulmonary specimens usually indicates disease, whereas Mycobacterium gordonae and Mycobacterium simiae typically represent contamination. This approach requires complete and up-to-date insight in locally prevalent NTM and their clinical relevance. In Croatia, all strains of NTM isolated in any laboratory are sent to the National Reference Laboratory for identification. NTM strains have been systematically recorded and reported since 1982. In the last decade, two retrospective analyses were done to assess the clinical relevance of different NTM species and the burden of pulmonary NTM disease. Over the past decade, a 30-fold increase in overall NTM isolation rates and a 4-fold increase in PNTM incidence were observed. Mycobacterium xenopi was the most frequently seen causative agent of pulmonary NTM disease, but the degree of clinical relevance (i.e., percentage of patients meeting the diagnosis criteria, per species) was higher for isolates of MAC (66.5%) and M. kansasii (57.2%). Only about 30% of the M. xenopi isolates represented true disease. Further, interesting regional differences were observed. Clinically relevant NTM isolates were significantly more often found in the coastal region of Croatia, and the average annual incidence of the PNTM was twice as high in coastal compared with the continental region. The overall burden of PNTM in Croatia is still low compared with tuberculosis. This can, in part, explain the observed lack of knowledge of NTM infections among respiratory specialists. Since these pathogens are increasingly common worldwide, especially in countries where the incidence of tuberculosis is declining, a constant rising of awareness and knowledge is necessary.

Evaluation and Comparison of Molecular and Conventional Diagnostic Tests for Detecting Tuberculosis in Korea, 2013

ObjectivesA fast and accurate diagnosis is necessary to control and eliminate tuberculosis (TB). In Korea, TB continues to be a serious public health problem. In this study, diagnostic tests on clinical samples from patients suspected to have TB were performed and the sensitivity and specificity of the various techniques were compared. The main objective of the study was to compare various diagnostic tests and evaluate their sensitivity and specificity for detecting tuberculosis. MethodsFrom January 2013 to December 2013, 170,240 clinical samples from patients suspected to have TB were tested with smear microscopy, acid-fast bacilli culture, and real-time polymerase chain reaction (PCR). The test results were compared and data were analyzed. ResultsA total of 8216 cultures tested positive for TB (positive detection rate, 4.8%). The contamination rate in the culture was 0.6% and the isolation rate of nontuberculous mycobacteria was 1.0%. The sensitivity and specificity of smear microscopy were 56.8% and 99.6%, respectively. The concordance rate between the solid and liquid cultures was 92.8%. Mycobacterium isolates were not detected in 0.4% of the cases in the liquid culture, whereas no Mycobacterium isolates were detected in 6.8% of the cases in the solid culture. The sensitivity and specificity of real-time PCR for the solid culture were 97.2% and 72.4%, respectively, whereas the corresponding data for the liquid culture were 93.5% and 97.2%. ConclusionThe study results can be used to improve existing TB diagnosis procedure as well as for comparing the effectiveness of the assay tests used for detecting Mycobacterium tuberculosis isolates.

Non-tuberculous mycobacterial infections at San Francisco General Hospital.

The epidemiology of non-tuberculous mycobacteria (NTM) infection is not well defined. We evaluated the trends in incidence of NTM infections at San Francisco General Hospital (SFGH), a large metropolitan county hospital. We performed a retrospective review of microbiologic and clinical records of all patients with a positive NTM culture reported from 1993 to 2001. NTM infection was defined by the isolation of >1 NTM from any clinical specimen. Patients were stratified by human immunodeficiency virus (HIV) status. Univariate and multivariate logistic regression were used to identify factors that were independently associated with NTM infection. Trends over time were assessed using Poisson test for trend. During the study period, 25 736 samples from 7395 patients were cultured for mycobacteria. Of these samples, 2853 (11.1%) from 1345 patients (18.2%) were culture positive for NTM. Patient characteristics associated with infection included younger age (P < 0.001), male gender (P < 0.001), White ethnicity compared with Asian and Hispanic (P < 0.001 and P = 0.01, respectively), and HIV positivity (P < 0.001). Overall, NTM infection at SFGH decreased significantly from 319 cases in 1993 to 59 in 2001 (P < 0.001). Mycobacterium avium was predominant in both HIV-positive and HIV-negative populations (74.5% and 44.6% of isolates, respectively), and Mycobacterium kansasii was the second most common NTM species isolated. The proportion of other NTM species isolated in these groups differed. In contrast to other published studies, time-series analyses show that NTM isolation rates decreased during the study period at SFGH, where NTM was most strongly associated with HIV infection.

Diseases Caused by Nontuberculous Mycobacteria in Asia

The isolation rate of nontuberculous mycobacteria (NTM) species and the prevalence of NTM-associated diseases are on the rise in Asian, as well as in Western countries; however, the species distribution of NTM isolates and the types of diseases caused by NTM species vary from region to region. In this review, we present an update on the epidemiology of NTM in Asia. We demonstrate that the distribution of NTM species varies within Asia and differs from that in North America and Europe. In addition, the clinical manifestations of NTM diseases include respiratory tract infections, disseminated infections, skin and soft tissue infections, lymphadenitis, empyema, ocular infections, CNS infections and genitourinary infections. Finally, the rate of adaptive resistance of anti-NTM antimicrobial agents remains high and may be associated with a poor outcome for patients with NTM diseases.

Geographical distribution and clinical relevance of non-tuberculous mycobacteria in Croatia

The clinical relevance of non-tuberculous mycobacteria (NTM) in Croatia is unknown. To estimate the isolation rate of NTM, record geographical differences and assess the burden of pulmonary NTM disease in Croatia. Nationwide retrospective cohort study of all Croatian residents with NTM isolated by culture in the period from 2006 to 2010. Microbiological criteria of the American Thoracic Society were used to establish a laboratory-based case definition of possible and probable NTM disease. Of 1187 individuals with pulmonary NTM isolates, 8.6% met the possible and 5.5% met the probable disease criteria. We estimated an annual incidence of probable pulmonary NTM disease of 0.23 per 100,000 population. This estimated annual incidence was 0.35/100,000 in the coastal region and 0.17/100,000 in the continental region. Species distribution differed between coastal and continental Croatia. NTM isolation frequency increased over the study period. Geography plays an important role in NTM species distribution and possible disease. The overall burden of NTM pulmonary disease in Croatia is still low compared to that of tuberculosis, but it is higher in the coastal region compared to the continental region.

Prevalence of Nontuberculous Mycobacteria Infection, China, 2004–2009

To the Editor: Pulmonary nontuberculous mycobacteria (NTM) diseases share clinical signs with tuberculosis (TB), causing a clinical dilemma with regard to therapy for patients with these diseases (1). In the past 30 years (post-AIDS era), NTM have increasingly been associated with pulmonary diseases in humans (2). Recent studies in urban areas of the People’s Republic of China have shown that the prevalence of NTM (isolation rate of NTM among all mycobacteria) is increasing; for example, prevalence in Shanghai increased from 4.26% in 2005 to 6.38% in 2008 (3). To investigate NTM prevalence in rural areas of China, we evaluated the NTM isolation rates, species distribution, and drug-resistance profiles through a population-based TB sentinel surveillance study in Shandong Province, the second largest province in China. The study protocol was approved by the Institutional Review Board of Shandong Provincial Chest Hospital (Jinan, Shandong, China). Clinical samples were collected through the ongoing sentinel TB surveillance project, which first began in 7 counties in Shandong Province in 2004 and expanded to 13 counties in 2008. Of the total surveillance population, rural populations accounted for ≈80%. Each sample collected in this study was identified only by a unique participant number. Each surveillance site sent sputum samples from all patients with suspected TB to the TB Reference Laboratory of Shandong Provincial Chest Hospital for mycobacterial culture, drug-susceptibility testing, and species identification. From January 1, 2004, through December 31, 2009, Mycobacteria spp. were isolated from sputum specimens from 3,949 patients with suspected pulmonary TB. Of these patients, mean age ± SD was 48.7 ± 20.4 years (range 1–92 years), 74.6% were male, and 300 were being re-treated for TB. Identification of Mycobacteria spp. was first conducted by conventional biochemical testing—p-nitrobenzoic acid and 2-thiophene carboxylic acid hydrazide testing—following a standard protocol (4). Mycobacteria spp. were further identified by 16S rRNA gene sequence analysis (MicroSeq ID Microbial Indentification Software, version 2.0; Applied Biosystems, Foster City, CA, USA) to the species level as described (5). Drug-susceptibility testing was performed according to standard procedures recommended by the World Health Organization, and quality control was conducted by inter-laboratory confirmation testing by reference laboratories recognized by the World Health Organization in South Korea and in Hong Kong Special Administrative Region, China (6,7). The drug panel included 4 first-line anti-TB drugs: isoniazid, rifampin, streptomycin, and ethambutol. The conventional biochemical testing of the 3,949 Mycobacteria spp. strains identified 68 NTM strains, among which the 16s rRNA gene sequence analysis confirmed 64 (1.6%) NTM strains and identified 3 M. tuberculosis complex strains and 1 Nocardia glanders strain. Among the 64 NTM strains, 52 (81.2%) were M. intracellulare, 5 (7.8%) were M. kansasii, 3 (4.7%) were M. fortuitum, 2 (3.1%) were M. chelonae, 1 (1.6%) was M. gordonae, and 1 (1.6%) was M. scrofulaceum. The first-line anti-TB drug resistance rates of the 64 NTM strains were 100% for isoniazid, 98.4% for streptomycin, 78.1% for rifampin, and 51.6% for ethambutol (Table). Among the 3,949 Mycobacteria spp. strains, 163 (4.1%) were resistant to at least isoniazid and rifampin, of which 50 (30.7%) strains were identified as NTM. Among 300 TB re-treatment cases, 12 (4.0%) were caused by clinically significant NTM infections. Over the 6 study years, NTM isolation rates among the study population did not show a substantial increasing or decreasing trend. Table Species and drug-resistance profiles of 64 nontuberculous mycobacteria strains, Shandong Province, People’s Republic of China, 2004–2009 Our data suggest that the NTM isolation rate among patients with suspected pulmonary TB in rural China (1.6%) is relatively lower and more stable than that for urban areas (mean rate 5.09% in Shanghai) and that the Mycobacterium spp. differ from those in other areas of China (3,8–10). In China and most other developing countries to which TB is endemic, the decision to initiate pulmonary TB treatment is based only on finding a positive sputum smear by microscopy examination, not on Mycobacteria culture, species identification, and drug-resistance testing results. Among our study population, NTM strains showed high drug resistance to first-line anti-TB drugs and accounted for 30.7% of suspected multidrug-resistant TB (MDR-TB) cases and 4.0% of TB re-treatment cases. These findings suggest that pulmonary NTM infections pose substantial difficulties with regard to clinical management of NTM and MDR-TB diseases in China. Laboratory species identification is imperative before proper treatment can be determined for patients with MDR-TB. Compared with conventional biochemical testing, 16S rRNA gene sequencing analysis can more accurately identify Mycobacteria spp.

Trends of mycobacterial clinical isolates in Taiwan

Non-tuberculous mycobacteria (NTM) can cause chronic pulmonary infection, however, NTM infection is generally overlooked. This retrospective study analyzed the frequencies of Mycobacterium tuberculosis complex (MTBC) and NTM clinical isolates from 99 200 specimens of patients suspected with pulmonary mycobacterial infection in Taiwan from 2002-2007. A total of 8024 mycobacterial isolates, including 5349 MTBC and 2675 NTM, were obtained from the 99 200 specimens in the study period. The overall mycobacterial isolation rate was 8.09% (8024/99 200), and the overall MTBC and NTM isolation rate was 5.39% (5349/99 200) and 2.7% (2675/99 200), respectively. Notably, the prevalence of NTM isolates among the identified mycobacteria strains was increased 2.6 fold from 2002 (17.54%, 147/838) to 2007 (45.80%, 659/1439). The frequencies of MTBC and NTM isolates showed a reciprocal trend: the NTM isolation rates were steadily increasing while the overall mycobacterial isolation rates remained stable over the study period. Our results suggest that the diagnosis, identification and susceptibility tests for NTM should be standardized and integrated in clinical routines, for providing the information of NTM infection and prescribing clinical treatment in a more precise and efficient way to reduce the increasing NTM in the studied area.

Isolation of Nontuberculous Mycobacteria Using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism

The isolation rate of nontuberculous mycobacteria (NTM) in clinical laboratories and the incidence of NTM infections are on the increase recently in Korea, but there have been only a few studies that reveal the general aspect of NTM isolation or species distribution. Therefore, this study was performed to examine the isolation rate of NTM, species identification, and the clinical significance of mycobacterial cultures. From August 2004 to May 2005, we examined mycobacterial isolates by AccuProbe test to differentiate NTM from Mycobacterium tuberculosis complex. NTM was then identified by polymerase chain reaction-restriction fragment length analysis (PCR-RFLP). A total of 6,742 specimens from 2,784 patients were requested for mycobacterial culture. Mycobacteria were isolated from 776 specimens (11.5%). The isolation rates of NTMs among the total culture positive specimens and culture positive sputum specimens were 24.4% (189/776) and 25.3% (169/667), respectively. Fourteen species of NTM identified in 172 of the 175 specimens tested included M. avium (39.0%), M. intracellulare (22.7%), and M. abscessus (19.8%). Using AccuProbe tests and PCR-RFLP method for mycobacterial cultures processed in a clinical laboratory, we were able to identify NTMs to the species level. The isolation rate of NTM in this study was similar to that reported in past studies in Korea. In addition, we found that some of the NTMs isolated in this study could cause pulmonary diseases.