Mycobacterium Xenopi Research Articles

Recent increase in non-tuberculous mycobacterial infection in patients with connective tissue diseases in Japan

BackgroundNon-tuberculous mycobacterial (NTM) infection is currently a growing health concern due to the increasing incidence and the need for prolonged therapy. In patients with connective tissue diseases, use of immunosuppressants may lead to an increased risk of NTM infection. However, few studies have examined the recent incidence of NTM infection among connective tissue diseases patients. This study investigated recent trends in NTM infection among connective tissue diseases patients. MethodsWe included adult patients from whose cultures NTM were isolated between January 2009 and October 2017 in our hospital. By reviewing their medical records, connective tissue diseases patients were identified. Types of connective tissue disease, NTM species, and treatment of NTM infection were extracted. ResultsNTM was isolated from 657 patients during the period. Among these, 24 patients had connective tissue diseases. The number and rate of NTM isolates from connective tissue diseases patients increased during the period, with 4 patients 2009 to 2012 (1.9%), and 20 patients from 2013 to 2017 (3.3%; P = 0.04). The proportion of Mycobacterium avium complex (MAC) to total NTM tended to be lower among connective tissue diseases patients (58.3%) than among non-connective tissue disease-patients (72.8%), but the difference was not significant (P = 0.20). Mycobacterium xenopi was significantly more frequent in connective tissue disease patients than in non-connective tissue diseases patients (P < 0.01). ConclusionThe recent increase in the incidence of NTM infections in connective tissue diseases patients was larger than that in the total population. NTM species other than MAC were isolated from connective tissue diseases patients.

Clinical outcomes in Mycobacterium xenopi versus Mycobacterium avium complex pulmonary disease: A retrospective matched cohort study.

Mycobacterium xenopi is associated with the highest mortality among pulmonary nontuberculous mycobacterial (NTM) infections, but whether this is due to the infection or other factors is unclear. There is little information regarding outcomes among patients infected with M. xenopi versus other NTM species. We conducted a retrospective matched cohort study comparing M. xenopi pulmonary disease (Mx-PD) to M. avium complex (MAC)-PD. Patients were matched by sex, age, radiologic subtype, and presence of cavitation. Baseline clinical characteristics, treatment, and outcomes were compared using matched analyses. We identified 70Mx-PD cases: 29 fibrocavitary-type, 28 nodular-bronchiectatic-type, and 13 unclassifiable-type CT patterns, mean (SD) age 63 (13) years, and 54.3% (n=38) female. Median follow-up duration was longer in the Mx-PD cohort (1552 days versus 1035 days, p=0.01). Symptoms, radiologic phenotype, and pulmonary function were similar between groups although the Charlson Comorbidity Index was numerically higher in Mx-PD patients (3.6 versus 3.2, p=0.08). Rifamycins were used less frequently in Mx-PD (59.5% versus 85.7%, p=0.02). Although combined clinical and radiologic improvement was similar between the groups, successful treatment was more common with Mx-PD (40.5% versus 16.7%, p=0.02) owing to superior culture conversion (70.8% versus 33.3%, p=0.0001). Mortality 24 months after initiation of treatment was numerically but not statistically greater in the Mx-PD cohort (20.4% versus 10.3%, p=0.32). Among matched Mx-PD and MAC-PD patients, standard anti-mycobacterial treatment was significantly more likely to achieve culture conversion and successful treatment for Mx-PD patients. Mortality among Mx-PD patients was numerically, but not statistically higher, possibly explained by increased comorbidity burden.

Complete Genome Sequence of Mycobacterium xenopi JCM15661T, Obtained Using Nanopore and Illumina Sequencing Technologies.

Mycobacterium xenopi is a slow-growing mycobacterial organism for which pathogenic features are unclear. Here, we report the complete genome sequence of an M. xenopi type strain. This sequence will provide essential information for future taxonomic and comparative genome studies of these mycobacteria.

A Chimeric EccB-MycP Fusion Protein is Functional and a Stable Component of the ESX-5 Type VII Secretion System Membrane Complex

The mycosin protease (MycP) is widely conserved in type VII secretion (T7S) systems throughout Actinobacteria. Within the T7S systems of mycobacteria, also known as the ESX systems, MycP is essential for secretion, which is probably linked to its stabilizing effect on the ESX membrane complex. However, it is unknown how this is mediated, as MycP is not a stable component of this complex. In this study, we set out to create a chimeric fusion protein of EccB5 and MycP5, based on a chimeric gene of eccB and mycP in the T7S locus of Bifidobacterium dentium. We show that this fusion protein is functional and capable of complementing ESX-5 secretion in both an eccB5 and a mycP5 knockout in Mycobacterium marinum. To study the ESX complex containing this fusion protein in more detail, we replaced the original eccB5 and mycP5 of the Mycobacterium xenopi esx-5 locus, reconstituted in Mycobacterium smegmatis, with the chimeric gene. The EccB5-MycP5 fusion construct also restored ESX-5 secretion under these double knockout conditions. Subsequent protein pulldowns on the central complex component EccC5 showed that under these conditions, the EccB5-MycP5 fusion was specifically copurified and a stable component of the ESX-5 complex. Based on our results, we can conclude that MycP5 carries out its essential function in secretion in close proximity to EccB5, indicating that EccB5 is the direct interaction partner of MycP5.

Socio-Economic and Environmental Factors Related to Spatial Differences in Human Non-Tuberculous Mycobacterial Diseases in the Czech Republic

Non-tuberculous mycobacteria (NTM) are ubiquitous environmental bacteria that can induce pulmonary and non-pulmonary diseases in susceptible persons. It is reported that the prevalence of NTM diseases is increasing in developed countries, but this differs by regions and countries. NTM species distribution and the rate of diseases caused by NTM vary widely in the historical territories of Moravia and Silesia (Czech Republic). This epidemiologic study of NTM diseases covers the period 2012–2018, reviews isolates obtained from patients with clinical disease and investigates correlations with related socio-economic and environmental factors. Individual NTM patients were included only once during the studied period and results were presented as incidence rate per year. The most frequently isolated NTM meeting the microbiological and clinical criteria in the study were the Mycobacterium avium-intracellulare complex, followed by Mycobacterium kansasii and Mycobacterium xenopi. A previously described endemic incidence of M. kansasii in the Karviná district and M. xenopi in the Ostrava district was also observed in this study. The incidence of NTM patients in the whole studied territory was 1.10/100,000 inhabitants (1.33/100,000 in men and 0.88/100,000 in women). The annual incidence of lymphadenitis in children (≤5 years of age) was 2.35/100,000 of the population of children during the 7 year period but increased in the year 2018 to 5.95/100,000. The rate of human tuberculosis in the studied area was 1.97/100,000 inhabitants. The incidence of NTM pulmonary diseases correlated with a lower socio-economic status (r = 0.63) and a higher concentration of benzo[a]pyrene pollution in the air (r = 0.64).

PL03.04 Lung Cancer and Tuberculosis: Parallel Lives

It is a Battlefield Searching for parallelisms, using historical analogies is a well established method in many fields of soft sciences, medical humanities included. A challenge of seemingly repetitive failure patterns and paradigm shift structures are to be answered in the following imaginary experiment. The aim is the creation of a mental model where understanding of developments and mistakes in treatment of tuberculosis might support our fight against lung cancer (1). The two diseases are existing parallely – one mainly for the poor and young and the other for the richer and older. History of tuberculosis follows the classic algorhythm: diagnostic (Villemin, Virchow), casuistic (Koch) and therapeutical (Waksman/Streptomycin) stages. The therapeutical phase of lung cancer has been reached without identified cause of the disease. Eradication of the macrosocopic focus by physical interference with the involved tissue mass, in both diseases preceeded medical treatment. Causation is not an absolute sine qua non of an effective treatment, as the tuberculosis-lung cancer analogy also proves. While lung cancer seems to be controlled by an emerging array of new drugs, tuberculosis poses a new challenge. Tuberculosis of the lung is a systemic disease, best treated by drugs with additional surgical removal of the focus of the disease as a last option. The disease has a fairly good chance of around 90% of to be cured (2). The prognostic factors include the functional and immunological reserves of the patient. Stage I to III lung cancer is a local manifestation of a systemic disease without sufficiently identified aetiology. Therapy response is understood at cohort level, but it is unpredictable where the individual patient’s fate is concerned. For reasons unknown, mechanical eradication offers the best chance for cure in early stages of the tumour. Some parallelism between tuberculosis and lung cancer might be of interest. In Search of a Character If progress takes a standstill categorization, fever takes over. Lymphnodes are the central elements of the Ghon and Ranke complexes. (3) of the tuberculous lung. The TNM system, a topology approach gyrates around the N status as well. (4). The desire to find a strong characteristic prognostic/predictive element resulted in the Gaffky index (5). The number of Koch bacillus in the sputum as a prognostic tool failed to validate the theory. The discussions of stations and size of lymphnodes in lung cancer (6) might share the fate of the Gaffky index. A Burnt out Case? There are disturbing similarities in the phenomenon of a late relapse/recurrence in both diseases. The dormant Koch bacillus vs exogenous reinfection debate (7) is paralleled by the dormant cancer cell hypothesis (8). Journey without Maps Circulating Koch bacillus, and their prognostic value hotly debated in the 1920s, are comparable to the circulating tumor cell question. The bloodstream journey polemic settled down by 1950, the “seed and soil” theory of cancer cells is subject of intense research. The Heart of the Matter Till the 1960s all tuberculosis cases seemed to be the same, until atypical tuberculosis was identified and the Mycobacterium xenopi lost its stigmatising power (95). Certain phenotypes of the adenocarcinoma in situ behaves definitely in a more benign way than any other cell type NSCLC. In 2019, we still do not know what is the single causative agent (if it exists at all) of NSCLC (if it exists at all as a single entity). The Copernican revolution in tumour biology is still awaited. The Power and the Glory Tuberculosis taught us, that the disease affects the body and the soul as well, reflecting to the society around the patient as well. Lung cancer treatment also depend on the immune status of the individual as well as on the protective capabilities of the science and the society. Affordability and availability of anticancer treatments/drugs are key words yet not interchangeable (8). Onco-economy is as a powerful factor as gene sequencing. A scalpel for sale Our techniques to treat lung cancer are rooted in surgery for tuberculosis (1). VATS techniques take their origin in Jacobeus’ thoracoscopy and Veress needle. Modern thoracic surgical staplers are derivates of the “Russian machines”, Petz staplers adjusted to tuberculotic bronchi. Thoracic surgery practiced in local anesthesia for many decades, is genuine awake/non-intubated thoracic surgery of today. The recent debate over neoadjuvant vs. adjuvant therapy reflects to the bygone dispute on resection before or after antituberculous medical treatment. The different modalities are no mutually exclusive options, but complementary ones. The End of the Affair: The main message of tuberculosis to present day oncopulmonologists is that no one can forget the interaction between tumour and patient and his/her socioeconomic status around the pathologically identified focus.

Prescribing Patterns for Treatment of Mycobacterium avium Complex and M. xenopi Pulmonary Disease in Ontario, Canada, 2001-2013.

Surveys suggest that clinicians diverge from guidelines when treating Mycobacterium avium complex (MAC) pulmonary disease (PD). To determine prescribing patterns, we conducted a cohort study of adults >66 years of age in Ontario, Canada, with MAC or Mycobacterium xenopi PD during 2001-2013. Using linked laboratory and health administrative databases, we studied the first treatment episode (>60 continuous days of >1 of a macrolide, ethambutol, rifamycin, fluoroquinolone, linezolid, inhaled amikacin, or, for M. xenopi, isoniazid). Treatment was prescribed for 24% MAC and 15% of M. xenopi PD patients. Most commonly prescribed was the recommended combination of macrolide, ethambutol, and rifamycin, for 47% of MAC and 36% of M. xenopi PD patients. Among MAC PD patients, 20% received macrolide monotherapy and 33% received regimens associated with emergent macrolide resistance. Although the most commonly prescribed regimen was guidelines-recommended, many regimens prescribed for MAC PD were associated with emergent macrolide resistance.

Radiologic types of Mycobacterium xenopi pulmonary disease: different patients with similar short-term outcomes.

Mycobacterium xenopi pulmonary disease (Mxe-PD) is common among nontuberculous mycobacterial infections in Europe and Canada. Associations between radiological pattern and clinical features and outcomes are inadequately studied in Mxe-PD. We sought to investigate clinical characteristics and outcomes according to the dominant radiological pattern among patients with Mxe-PD. We retrospectively studied patients with Mxe-PD seen in our clinic, categorizing their predominant CT pattern as nodular bronchiectasis, fibrocavitary, or unclassifiable, and compared clinical characteristics, treatment, and outcomes between radiologic groups. Of 94 patients with Mxe-PD, CT patterns comprised nodular bronchiectasis (40/94, 42.6%), fibrocavitary (37/94, 39.4%), and unclassifiable (17/94, 18.1%). Compared with fibrocavitation, patients with nodular bronchiectasis were female dominant, less often had COPD, less often had AFB smear-positive sputum, and more frequently had co-isolation of Pseudomonas. Patients with nodular bronchiectasis were less often treated (65% versus 91.9%) and when treated, they received fewer anti-mycobacterial drugs (on average 3 versus 4). Outcomes did not differ significantly by radiological pattern. Nodular bronchiectasis was common among Mxe-PD patients in our clinic. Compared with fibrocavitary disease, patients with nodular bronchiectasis had features suggestive of milder disease and were less often treated. Among treated patients, outcomes did not differ by radiologic pattern.

A case report of pulmonary &lt;i&gt;Mycobacterium xenopi&lt;/i&gt; infection suspected as lung cancer

患者は48歳，男性．胸部異常陰影を指摘され受診した．CEAが軽度高値で，胸部CT検査では右肺上葉に最大径50 mmの腫瘤を認め，同部位にFDG-PET検査でFDGの異常集積がみられた．CTガイド下生検では悪性所見を認めなかったが，肺癌を否定出来なかったため，手術を施行した．切除標本の抗酸菌塗抹検査ではGaffky5号で，DNA-DNA hybridization法（DDH法）により原因菌をMycobacterium xenopiと同定した．術後は化学療法1年間を追加し，術後2年3ヵ月の現在まで無再発で経過している．

Mycobacterium xenopi Genotype Associated with Clinical Phenotype in Lung Disease.

Mycobacterium xenopi is responsible for pulmonary disease (PD) in Europe and Canada. Despite its high prevalence and increasing clinical importance, little is known about the genetic diversity of M. xenopi. Through a prospective study for M. xenopi strain type and the relation to clinical phenotype, 39 patients with M. xenopi PD were analyzed. Our study demonstrated that sequence type (ST) 5 was dominant in Ontario among 15 distinct STs and caused PD in people even without underlying lung disease, whereas disease due to non-ST5 was found almost exclusively in patients with underlying lung disease.

Emerging pathology: Pulmonary disease caused by Mycobacterium xenopi - a challenge in clinical practice

Introduction. Human nontuberculous mycobacteria (NTM) or environmental mycobacteria related disease is on increase. Risk factors are unclear and associations are observed in relation to climate differences, population density, or host susceptibility. With availability of molecular techniques for NTM identification, we faced emergence of NTM pulmonary cases. The work is an invitation more to colleagues to enroll the rare NTM cases into large study group. Case report. During an episode of productive cough and fever in a 73-year-old HIV-negative man smoker with minimal sequellae of pulmonary tuberculosis, sputum smears were acid fast bacilli positive on direct microscopy. The L?wenstein- Jensen culture results were positive with 20, 30 and 50 colonies, and molecular identification confirmed Mycobacterium xenopi (M. xenopi). Standard chest radiography showed no signs of active lesions. Examination was completed with bronchoscopy and thorax multi-slice computed tomography (MSCT). Cavitary lesions in the apico-posterior part of the left upper lobe (LUL) were detected. Under treatment (rifampicin, ethambutol, clarithromycin) sputum conversion was achieved, but irregular cavitation in the LUL remained at MSCT after 6 and after 12 months with signs of minimal regression. Patient?s general condition only mildly improved and asthenia remained. Observed risk factors were previous pulmonary disease, tobacco smoking, malnutrition and prolonged emotional stress. Conclusion. M. xenopi related pulmonary disease, difficult to cure and with uncertain prognosis, is a challenge in clinical practice. Since treatment is still controversial, more randomized clinical trials are needed. Current international multicentre approach might be a good option for a larger sample size and development of new guide.

Drug Susceptibility of Non-tuberculous Strains of Mycobacterium Isolated from Birds from Poland.

Mycobacterioses are a constant problem in backyard poultry, as well as pet birds. To date, no evidence of direct transmission of atypical bacilli between humans has been demonstrated, but it cannot be ruled out that sick animals can be a source of infection for people in their environment. The aim of the study was to identify mycobacteria isolated from birds with diagnosed mycobacteriosis and to determine the susceptibility of mycobacterial isolates from these animals to antituberculous drugs most commonly used in the treatment of mycobacterial infections in humans. For drug susceptibility tests, drugs such as isoniazid, rifampicin, streptomycin, ethambutol, ofloxacin, capreomycin, cycloserine and ethionamide were used. A high degree of drug resistance was demonstrated, particularly in Mycobacterium avium. Isolates of Mycobacterium xenopi showed a relatively good susceptibility to the drugs tested. The drug resistance of Mycobacterium genavense has not been determined, but this mycobacterium was identified in ten cases, which is the second most frequent occurrence in the cases studied.

Evaluation of PyroMark Q24 pyrosequencing as a method for the identification of mycobacteria

We evaluated PyroMark Q24 (QIAGEN) pyrosequencing as a method for the identification of mycobacteria, with potential application in clinical practice. Sequence data from the hypervariable region A of the 16S rRNA gene (43 and 35bp sequences) were obtained using PyroMark Q24, and a similarity search was performed automatically with PyroMark IdentiFire software. Of the 148 mycobacterial type strains tested, 138 (93.2%) were accurately identified to single or clade species level, including complex level. From the remaining 10 strains, 3 (Mycobacterium gilvum, Mycobacterium goodi, and Mycobacterium thermoresistible) showed poor sequencing quality of homopolymers. For 6 other strains (Mycobacterium cosmeticum, Mycobacterium flavescens, Mycobacterium pallens, Mycobacterium hodleri, Mycobacterium xenopi, and Mycobacterium crocinum), the sequences were unreadable from the middle, and Sanger sequencing indicated biallelic site. Finally, a 40bp sequence for Mycobacterium gordonae could not be obtained despite repeated attempts. PyroMark Q24 provided accurate identification of multiple mycobacterial strains isolated from common clinical settings, but additional gene sequencing is required to distinguish species identified as a group or complex.

Transmission of Mycobacterium xenopi to a pet albino ferret (Mustela putorius furo) from a domestic aquarium

A three-year-old ferret presented with a three-month history of rapid clinical deterioration necessitating euthanasia shortly after initial veterinary assessment. Postmortem PCR testing confirmed Mycobacterium xenopi which is most commonly identified...

Structure of the mycobacterial ESX-5 type VII secretion system membrane complex by single-particle analysis.

Mycobacteria are characterized by their impermeable outer membrane, which is rich in mycolic acids1. To transport substrates across this complex cell envelope, mycobacteria rely on type VII (also known as ESX) secretion systems2. In Mycobacterium tuberculosis, these ESX systems are essential for growth and full virulence and therefore represent an attractive target for anti-tuberculosis drugs3. However, the molecular details underlying type VII secretion are largely unknown, due to a lack of structural information. Here, we report the molecular architecture of the ESX-5 membrane complex from Mycobacterium xenopi determined at 13 Å resolution by electron microscopy. The four core proteins of the ESX-5 complex (EccB5, EccC5, EccD5 and EccE5) assemble with equimolar stoichiometry into an oligomeric assembly that displays six-fold symmetry. This membrane-associated complex seems to be embedded exclusively in the inner membrane, which indicates that additional components are required to translocate substrates across the mycobacterial outer membrane. Furthermore, the extended cytosolic domains of the EccC ATPase, which interact with secretion effectors, are highly flexible, suggesting an as yet unseen mode of substrate interaction. Comparison of our results with known structures of other bacterial secretion systems demonstrates that the architecture of type VII secretion system is fundamentally different, suggesting an alternative secretion mechanism.

Update on pulmonary disease due to non-tuberculous mycobacteria.

Non-tuberculous mycobacteria (NTM) are emerging worldwide as significant causes of chronic pulmonary infection, posing a number of challenges for both clinicians and researchers. While a number of studies worldwide have described an increasing prevalence of NTM pulmonary disease over time, population-based data are relatively sparse and subject to ascertainment bias. Furthermore, the disease is geographically heterogeneous. While some species are commonly implicated worldwide (Mycobacterium avium complex, Mycobacterium abscessus), others (e.g., Mycobacterium malmoense, Mycobacterium xenopi) are regionally important. Thoracic computed tomography, microbiological testing with identification to the species level, and local epidemiology must all be taken into account to accurately diagnose NTM pulmonary disease. A diagnosis of NTM pulmonary disease does not necessarily imply that treatment is required; a patient-centered approach is essential. When treatment is required, multidrug therapy based on appropriate susceptibility testing for the species in question should be used. New diagnostic and therapeutic modalities are needed to optimize the management of these complicated infections.

Direct identification of mycobacteria from liquid media using a triplex real-time PCR coupled with pyrosequencing method

Culture in enriched broth, as well as on a solid medium, is recommended for primary isolation of mycobacteria. With the introduction of liquid mycobacterial culture methods, a substantial workload regarding the identification of culture-recovered mycobacterial species, particularly Mycobacterium tuberculosis complex (MTC), has been imposed on our laboratory. We thus developed a triplex, real-time PCR coupled with pyrosequencing assay that can directly identify mycobacterial species from liquid media, which can reduce the workload. In this assay, real-time PCR simultaneously detects MTC and Mycobacterium xenopi, and amplifies the region of 16S rRNA gene containing hypervariable region A for pyrosequencing analysis; subsequent, pyrosequencing identifies many other nontuberculous mycobacteria. The assay was evaluated using 333 DNA samples directly prepared from liquid media, including 24 reference strains and 309 clinical isolates. Three hundred and twenty-eight (98.5%) of the 333 samples were correctly identified. The remaining five were determined as indeterminate. In conclusion, this coupled assay would be an alternative method for rapid identification of mycobacteria directly from liquid media in a clinical laboratory with a high workload in regions where tuberculosis is endemic.

Engineering versatile protein expression systems mediated by inteins in Escherichia coli.

We have recently employed an intein, Saccharomyces cerevisiae vascular membrane ATPase (VMA), in conjunction with efficient expression and secretory functions formed between the ompA leader sequence and the human epidermal growth factor (EGF) gene (fused at the 5' end of VMA), and the human basic fibroblast growth factor (bFGF) gene (fused at the 3' end of VMA), to engineer an efficient intein-based Escherichia coli system for high-level co-expression of EGF and bFGF as authentic mature products. Both products were found not only excreted to the culture medium but also located, surprisingly, in the cytoplasm (Kwong and Wong 2013). In this study, we employed two structurally varied inteins, VMA and Mycobacterium xenopi GyraseA (GyrA), and further demonstrated that despite acting alone, both VMA and GyrA were able to mediate successful co-expression of two widely different proteins, EGF and an endoglucanase (Eng) in E. coli. Although EGF and Eng were initially expressed as large precursors/intermediates, they were soluble and auto-cleavable to finally yield the desired products in both the cytoplasm and culture media. The results further substantiate our postulation that the aforementioned intein/E. coli approach might lead to the development of cost-effective and versatile host systems, wherein all culture fractions are involved in producing the target proteins.

Time-kill kinetics of slowly growing mycobacteria common in pulmonary disease.

This study aimed to provide basic pharmacodynamic information for key antibiotics used to treat Mycobacterium avium and Mycobacterium xenopi pulmonary disease. M. avium subspecies hominissuis IWGMT49 and M. xenopi ATCC 19250 type strains were used; the MICs of clarithromycin, amikacin and moxifloxacin were determined by broth microdilution. Time-kill assays were performed, exposing bacteria to 2-fold concentrations from 0.062× to 32× the MIC at 37°C for 240 h for M. avium or 42 days for M. xenopi. The sigmoid maximum effect (Emax) model was fitted to the time-kill curve data. Maximum killing of M. avium by amikacin was obtained between 24 and 120 h (0.0180 h(-1)) and was faster and higher than with clarithromycin (0.0109 h(-1)); however, regrowth and amikacin-resistant mutants were observed. Killing rates for M. xenopi were higher, 0.1533 h(-1) for clarithromycin and 0.1385 h(-1) for moxifloxacin, yet required 42 days. There were no significant differences between the Hill's slopes determined for all of the antibiotics tested against M. avium or M. xenopi (P = 0.9663 and P = 0.0844, respectively). The killing effect of amikacin and clarithromycin on M. avium subspecies hominissuis was low, although amikacin activity was higher than that of clarithromycin, supporting its role in a combined therapy. Clarithromycin and moxifloxacin may have similar activity within treatment regimens for M. xenopi disease. Future studies of in vitro and in vivo pharmacokinetic/pharmacodynamic interactions are needed to improve the current regimens to treat these two important slowly growing mycobacteria in pulmonary disease.

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.