INTRODUCTION

The number of patients with pulmonary disease caused bynontuberculous mycobacteria (NTM) is rapidly increasingglobally [1]. Poor resistance against infections, due to previ-ous lung diseases, immune deficiency and immune-modu-lating treatment, increases the likelihood of patients devel-oping pulmonary NTM disease. Additionally, co-morbidi-ties such as chronic liver disease, diabetes mellitus, cardiacdisease, and malignancy predispose to infection as well [2].

Advances in medical imaging and microbiologicaltechniques, particularly molecular techniques, have en-

hanced our understanding of this disease, but manyuncertainties remain, especially in radiological diagno-sis. Consequently, radiographic abnormalities often seemto remain stable and progress very slowly. All of thesefactors contribute to the delay in diagnosis. However,recent position statements have suggested that patientsthat have suspected NTM and are classified as grade Dshould have a chest X-ray and CT scan [3] based on ex-pert opinions and previous case studies.

Patients with chronic respiratory symptoms have M.simiae isolated from sputum and bronchoalveolar lavagespecimens. This increase has been noted in Middle-Easterncountries and in other countries such as Israel and Australia[4-7]. Often M. simiae is considered to be of low virulence.However, radiologically it can be challenging. The aim ofthis study was to identify the radiographic and CT scan find-ings in patients with M. simiae pulmonary infection.

254 Lebanese Medical Journal 2018 • Volume 66 (5)

AARRTTIICCLLEE OORRIIGGIINNAALL//OORRIIGGIINNAALL AARRTTIICCLLEEIMAGING APPEARANCE OF MYCOBACTERIUM SIMIAE PULMONARY INFECTIONhttp://www.lebanesemedicaljournal.org/articles/66-5/original3.pdf

Amro BAASSIRI1, Charbel SAADE1, Lara NASSAR1, Maria EL HOMSI, Souha KANJ2

Andrew BARAKAT1, Ghina BERJAWI1

Baassiri A, Saade C, Nassar L, El Homsi M, Kanj S, Barakat A,Berjawi G. Imaging appearance of Mycobacterium simiae pul-monary infection. J Med Liban 2018 ; 66 (5) : 254-259.

Baassiri A, Saade C, Nassar L, El Homsi M, Kanj S, Barakat A,Berjawi G. Aspect radiologique de l’infection pulmonaire àMycobacterium simiae. J Med Liban 2018 ; 66 (5) : 254-259.

ABSTRACT • Aim : The purpose of this study was to iden-tify the radiographic and CT scan findings in patients withMycobacterium simiae pulmonary infections. Methods : Atotal of 40 patients with positive cultures for M. simiae wereidentified between January 2000 and August 2015. In ourradiographic analysis, we included those with cultures thatgrew M. simiae as the only isolate.The patients’ chest X-raysand Computed Tomography scans were reviewed andReceiver Operating Characteristic (ROC) and inter- andintra-reader variability was recorded. Results : A total of 54images were retrieved, 30 Chest X-rays and 24 CT scans.Out of the 9 patients who had chest X-rays, 3 (33.3%)patients had their x-rays read as normal while the rest 6(66.6%) had abnormal findings. All patients had abnormalfindings on their CT images. The most common radiograph-ic findings were consolidations, bronchiectasis, nodules,ground glass opacities, and enlarged mediastinal lymphnodes. ROC scores demonstrated significant detection ofnontuberculous mycobacteria (NTM) (p < 0.003) (95%; CI[0.589-0.864] and CI [0.566-0.844]) (p < 0.001) with goodinterobserver agreement (k = 0.63). Conclusion : M. simiaeinfection has various radiographic presentations. It is imper-ative that radiologists recognize its common radiographicfeatures. Furthermore, M. simiae must be considered evenin immunocompetent patients.

Keywords: lung, Mycobacterium simiae, chest X-ray, computedtomography

RÉSUMÉ • But:: Identifier les résultats radiographiques et tomo-densitométriques chez les patients atteints d’infections pulmo-naires à Mycobacterium simiae. Méthodes: Un total de 40 pa-tients avec des cultures positives pour M.simiae ont été identifiésentre janvier 2000 et août 2015. Dans notre analyse radiogra-phique, nous avons inclus ceux avec M. simiae isolé comme uni-que germe. Les radiographies thoraciques et les tomodensito-métries ont été examinées et les caractéristiques de fonctionne-ment du récepteur (ROC) ainsi que la variabilité inter- et intra-lecteur ont été enregistrées. Résultats: 54 images ont été collec-tées, 30 radiographies thoraciques et 24 tomodensitogrammes.Parmi les 9 patients qui ont recu des radiographies thoraciques,3 (33,3%) patients ont eu un examen normal et 6 ont présentédes anomalies radiologiques.Tous les patients avaient des résul-tats anormaux sur leur scanner. Les observations radiologiquesles plus fréquentes étaient des consolidations, des bronchec-tasies, des nodules, des opacités du verre dépoli et des gan-glions lymphatiques médiastinaux élargis. Les scores ROC ontdémontré une détection significative de mycobactéries non tuber-culeuses (NT < 0,003) (95%, IC [0,589-0,864] et IC [0,566-0,844]) (p < 0,001) avec un bon accord interobservateur (k = 0,63).Conclusion: L’infection à M.simiae a diverses présentations radio-graphiques. Il est impératif que les radiologues reconnaissent sescaractéristiques radiographiques communes. En outre, M. simiaedoit être considéré même chez les patients immunocompétents.

Mots-clés : poumon, Mycobacterium simiae, radiographiethoracique, tomodensitométrie

1Department of Diagnostic Radiology, American University ofBeirut Medical Center (AUBMC), Beirut, Lebanon.

2Department of Infectious Diseases, AUBMC.*Corresponding author: Ghina Berjawi, MD.e-mail: gb02@aub.edu.lb

MATERIALS AND METHODS

Patient selectionInstitutional review board approval was received for thisstudy. We reviewed all consecutive cases with positiveculture for NTM obtained between January 2000 andAugust 2015. There was a total of 40 patients where M.simiae was either the only species cultured or was de-tected amongst other species from respiratory samples.Speciation of the isolated NTM was carried out at theMayo Clinic by using the Maldi-Tofassay or, if that failed,DNA sequencing was used.

The images retrieved dated from the initial day ofadmission till either the last day of the study if a positiveculture persists or until the first negative culture wasobtained. All patients (n = 40) met the diagnostic criteriaof the American Thoracic Society inclusion criteria forNTM pulmonary disease [8]. However, in order to dis-card the possibility of regarding a case as a mere coloni-zation, we included only those where M. simiae grew asthe only isolate. Some patients had their diagnostic radio-graphs performed at other hospitals and the images werenot available for review.

Of the patient population, 17 patients were included inthe radiographic analysis (male: n = 10; female: n = 7).The mean age of patients at time of diagnosis was 60(range, 21-84 years). Five patients had a chest X-ray, 8patients had CT scan, and 4 patients had both X-ray andCT. A total of 54 cases were retrieved (30 chest X-raysand 24 CT scans). In the study population, only sixpatients had a single image with no follow-up imagingstudies. The rest of the patients were followed up for anaverage of 15 months, with the shortest period being1 month and the longest 55 months.

Imaging techniqueChest X-ray exams consisted of a single posterior-ante-rior view that was obtained using 70-80KVp along witha tube-to-distance of 6 feet. Unenhanced CT scans wereacquired with either a Philips ICT scanner (8 patients) ora Siemens Somatom sensation scanner (4 patients).

All CT data were reconstructed using sharp algorithmdedicated to lung imaging. On the Philips ICT scanner, CTtechnique was as follows: 80 mm collimation, 100KVp,200mA, 1.5-mm intervals. On the Siemens Somatom sen-sation scanner, CT technique was as follows: 20mm colli-mation, 120KVp, 200 mA, 1.5-mm intervals. All imageswere reconstructed at 1.5 mm thickness. The scan datawere displayed on two monitors (with 1536 x 2048 imagematrices, 3 megapixel viewable gray-scale, using BARCOluminescence) of a picture archiving and communicationsystem, or PACS (AGFA version 6.5.3.562). Both medi-astinal (window width, 150 HU; window level, 88HU) and

lung (window width, 1500 HU; window level, - 600 HU)window scans could be viewed and image brightness man-ually adjusted when being reviewed.

Review of radiographs and CT scansTwo radiologists reviewed initial and follow-up radio-graphs and CT scans (mean years of experience: 10years; minimum 5 years, maximum 15 years). The radio-logists were given a mixture of cases including patientswith TB, NTM infection, and normal studies.

They were unaware of any clinical information. Theyassessed the images separately then reached final deci-sions by consensus. A total of six lobes were assessed forany abnormal findings. The lingula was counted as a lobe.

Chest X-rays were assessed for the following: bron-chiectasis, cavitary lesions, nodules, atelectasis, pleuraleffusions, pleural thickening, reticulonodular opacities,and volume loss/decrease.

CT images were assessed for the following: consoli-dations, bronchiectasis, nodules, cavities, ground glassopacity, linear scarring, volume loss, parenchymal calci-fication, emphysema, air-trapping, mediastinal or hilarlymph node (LN) enlargement or calcification, pleuraleffusions, pleural thickening/calcification, esophagealdilatation, esophageal wall thickening, and hiatal hernias.Consolidations were described as lobular, segmental, orperibronchial. Bronchiectasis was also described as cy-lindrical, cystic, or varicose. As for the nodules, theywere described as either tree-in-bud pattern or peribron-chovascular. In the presence of cavities, we accountedfor their number, their diameters measured and reportedin millimeters, and wall thickness was commented onwhether it was thick or thin walled.

ROC analysisA total of 60 cases were randomly allotted, divided equallybetween the three groups. Of the 60 cases, 22 exhibited nopathology, 13 demonstrated tuberculosis, and 25 with NTM.Truth was determined by the cardiothoracic radiologistreports as well as confirmation with CT and culture.

Chart reviewThe medical records were reviewed for the followinginformation, when present: smoking history, pre-existinglung disease, immunodeficiency, purified protein deriv-ative (PPD) result, history of tuberculosis (TB) treat-ment, and human immunodeficiency virus (HIV) status.Concerning their smoking history, 9 (53%) were pastsmokers, 6 (35%) never smoked, and we had data miss-ing for 2 (12%) patients. Six (35%) patients had pre-existing lung disease while 11 (65%) patients did not.There was a single case of asthma, 2 cases of bronchi-ectasis, and 3 cases of chronic obstructive pulmonary

A. BAASIRI et al. – Imaging appearance of M. simiae pulmonary infection Lebanese Medical Journal 2018 • Volume 66 (5) 255

disease (COPD). One patient had another risk factornamely immunodeficiency, for he had acute myeloidleukemia (AML). Two of the 3 cases of patients withCOPD and the patient with AML had a history of recur-rent pneumonias. PPD testing was done for all patients,13 patients were negative while 4 were positive for latentTB. None of those patients with latent TB took treatmentmedications prior to their admission. All patients wereHIV negative except for one patient who was alreadydiagnosed prior to presentation.

Statistical analysisPathology compared between normal, tuberculosis andNTM using a two-tailed independent t-test. The ROCanalysis utilized the Dorfman-Berbaum-Metz (DBM)approach while using random readers and fixed cases[9]. The analysis treated cases as fixed because the lim-ited image sample size should not be taken as represen-tative of all images. Results were considered statistical-ly significant at p ≤ 0.05. In each case series inter- andintra-observer agreements were calculated using Cohen’skappa analysis. A k value 0.60-1, 0.41-0.60, 0.21-0.40and less than 0.20 was considered excellent, moderate,fair and poor agreement respectively.

RESULTS

The chest X-ray findings are summarized in table I. Ninepatients had chest X-rays, 6 (66.6%) of which had abnor-mal findings. Both lungs were concomitantly affected in3 patients. Bronchiectasis and pleural effusions wereidentified in 2 patients each. Reticulonodular opacities,emphysematous changes (Fig. 1a), and infiltrates werevisualized in one patient each. A single patient had aconsolidation visualized in the left lower lobe. None ofthe patients had cavitary lesions, nodules, atelectasis,pleural thickening, or volume loss in the lung visualizedon their chest X-rays.

The CT findings are summarized in tables II and III.All patients had abnormal findings on their CT images.Of the 12 patients who had CT images, 7 patients (58%)

had both lungs concomitantly affected. Unilateral lunginfection was detected in a total of 5 (41.6%) patients;left and right lungs were involved in 3 patients (25%)and 2 patients (17%), respectively.

The most commonly involved lobe was the right upperlobe (66.67%) [patients], followed by the left lower and theright middle lobes (50%), the right lower lobe and the lingu-la (41.67%). The least common lobe affected was the leftupper lobe which was involved only in 3 patients (25%).

Consolidation was visualized in 5 patients. It was lob-ular shaped in 1 patient while the rest were segmental.Bronchiectasis was noted in 5 patients all of which hadcylindrical type (Fig. 2a). However, one patient hadcylindrical type bronchiectasis which on follow-up hadevolved into having a cystic component as well. Noduleswere visualized in 6 cases, most commonly as a tree-in-bud pattern (66.67%) (Figs. 2b & 3b), followed by peri-bronchovascular, and nonspecific (16.67%) each.

Over a follow-up of 18 months, one patient had 2 CTscans in which 5 thin walled cavities were visualized in total.Two cavities (8 mm & 17 mm in diameter) were detectedon the first CT and 3 cavities (9, 10, & 20 mm in diame-ter) on follow-up (Fig. 3a). Other findings include: groundglass opacity and enlarged mediastinal lymph nodes(41.67%), bilateral apex linear scarring (16.67%), emphyse-ma (16.67%) (Fig.1b), and hilar lymphadenopathy (16.67%).

256 Lebanese Medical Journal 2018 • Volume 66 (5) A. BAASSIRI et al. – Imaging appearance of M. simiae pulmonary infection

TABLE I. SUMMARY OF CHEST X-RAY FINDINGS

Finding Number of patients

Normal 3 Abnormal 6Bronchiectasis 2Pleural effusions 2Emphysematous changes 1Reticulonodular opacities 1Consolidation 1Infiltrates 1

TABLE II. SUMMARY OF LOBES AFFECTED AS SEEN ON CT

Lobe affected Number of patientsRight upper lobe 8Left lower lobe 6Right middle lobe 6Right lower lobe 5Lingula 5Left upper lobe 3

TABLE III. SUMMARY OF CT FINDINGS

Finding Number of patientsConsolidation 5Lobular 1Segmental 4Bronchiectasis 5Cavitation 1Ground glass opacity 5Linear scarring 2Emphysema 2Enlarged mediastinal lymph nodes 5Hilar lymph node calcification 2Nodules 6Tree in bud pattern 4Bronchovascular 1Non specific 1

Figure 1. A 70-year-old male with M. simiae pulmonary diseasea. PA chest radiograph showing right upper lobe emphesematous changes (arrows) and left upper lobe fibrosis from previoussurgery and loss of volume. b. Axial thick section (4mm) CT scan showing similar changes to corresponding chest radiograph.

Figure 2. A 61-year-old female with M. simiae pulmonary diseasea. Axial thick-section (4mm) CT scan shows abnormal dilatation of the bronchial tree in keeping with bronchiectasis (arrow) in the rightmiddle lobe b. CT shows multiple small nodules and branching centrilobular nodules, so called tree-in-bud (arrow) in the right lower lobe.

Figure 3. A 55-year-old female with M. simiae pulmonary diseasea. Axial thick-section (4mm) CT scan obtained at the level of the great vessels shows multiple thin-walled cavities in both lung apices. b. CT shows multiple small nodules and branching centrilobular nodules, so called tree-in-bud (arrows) in the upperright and lower right lobes.

None of the patients had lung volume loss, parenchymal cal-cification, air trapping, pleural thickening or calcification ontheir CT scans.

When combining normal and abnormal images in thereading session, it resulted in significant reader sensitivi-ty and specificity with mean ROC values demonstratingincreased reader confidence range by reader 1 (95%;CI [0.722-0.873]) and reader 2 (95%;CI [0.648-0.813])(p < 0.0001) (Fig. 4). We further extrapolated the datathat evaluated the sensitivity and specificity of NTM onits own with significant reader confidence by reader 1(95%; CI [0.589-0.864]) and reader 2 (95%; CI [0.566-0.844]) (p < 0.003) (Fig. 5).

Moreover, detection and agreement in patients withNTM yielded good (p < 0.001) interobserver agreement(k = 0.63) and there was a strong positive relationshipbetween NTM and patients with chest pathology overall(r = 0.61, p < 0.001).

DISCUSSION

The true virulence of NTM is controversial. Even in thepresence of a positive culture, it is difficult to distinguishbetween colonization and invasive pulmonary disease.Nevertheless, studies have shown that NTM are indeedpathogenic. Transbronchial lung biopsies carried out inpatients with Mycobacterium avium complex (MAC) in-fection demonstrated lung tissue invasion. Extensive epi-thelioid granuloma formation, destruction of bronchialcartilage and smooth muscle layers, and ulceration ofbronchial mucosa were visualized [10-12]. Furthermore,Moore studied serial computed tomographies [8] for pa-tients with an atypical Mycobacterium infection. Uponfollow-up, the most common manifestation, namely bron-chiectasis was noted in new lung areas and progressionof existing bronchiectasis was visualized [13].

NTM pulmonary infection has two distinct radiologicmanifestations: the cavitary form (classical infection)and bronchiectatic form (nonclassical infection). Thecavitary form of the disease is prevalent in elderly menwith an underlying chronic disease; usually chronic ob-structive pulmonary disease (COPD). The characteristicradiologic findings include upper lobe cavitary forma-tion and nodules [14-17]. The bronchiectatic form is prev-alent in elderly women without an underlying disease.The characteristic radiologic findings include bronchi-ectasis, bronchiolitis, and small nodules. The middlelobe and lingula are most commonly affected [18-22].Despite the nonspecific imaging features, they are usefulin ruling out or ruling in an NTM infection when put inclinical context. This is echoed by our readers’ signifi-cant high sensitivity and low specificity as well as goodinter- and intra-reader variability in identifying imagesof NTM infected individuals.

Our radiological imaging results showed that we hadnormal chest radiographs in 33.3% of the patients who hada chest X-ray. This is comparable to the findings by Shitritet al. in which 38% of their patients had normal chest X-ray readings [2]. The right upper lobe was the most com-monly involved lobe in our study. According to Moaz et al.the lower/middle lobes (55%) were more affected than theupper lobes (45%) [23]. However, the right upper lobe wasaffected more than its left counterpart; 25% and 20%respectively. In our study, the most common radiographicfindings were consolidations, bronchiectasis, nodules,ground glass opacities, and enlarged mediastinal lymphnodes. It is comparable to other studies which reportednodular lesions (100%) and bronchiectasis (85%) as themost common findings [6,24). However, unlike Baghaei etal. where cavitation (88.5%) was amongst the most com-mon findings, we had only one single patient who had atotal of 5 cavities over a follow-up duration of 18 months.

258 Lebanese Medical Journal 2018 • Volume 66 (5) A. BAASSIRI et al. – Imaging appearance of M. simiae pulmonary infection

Figure 4. ROC analysis for all cases

Figure 5. ROC analysis for NTM cases

R1

R2

Reference Line

R1_NTM

R2_NTM

Reference Line

Sens

itivi

ty

Specificity

Sens

itivi

ty

Specificity

0.0 0.2 0.4 0.6 0.8 1.0

0.0 0.2 0.4 0.6 0.8 1.0

1.0

0.8

0.6

0.4

0.2

0.0

1.0

0.8

0.6

0.4

0.2

0.0

Miller Jr WT claimed that radiographic findings ofNTM pulmonary infections are not influenced by a specif-ic mycobacterial species [18]. This was corroborated byJeong et al. whereby irrespective of which mycobacterialspecies caused the infection, the most common findingswere the same [25]. In contrast to a report by Ellis andHansell in which radiographic features of NTM infectionswere variable according to the isolated species [26]. Somedifferences are subtle while others are blatant. Neverthe-less, the question remains whether these differences aresignificant. Further studies are needed to address this mat-ter. This is particularly important as the clinical manifesta-tions of various NTM mycobacterial infections are vari-able and not all laboratories have the ability to identify thespecies, especially that such infections are prevalent insome developing countries with limited resources. More-over, treatment is species specific since the organisms tendto have different susceptibility profile.

Our study has its limitations including patient selec-tion bias in a tertiary care medical center with patient re-ferral mostly from the city area. Another limitation isthat the number of immunocompromised patients waslimited. These patients might have a different radio-graphic pattern. Finally, our case load was small to runfurther statistical analyses.

M. simiae infection has various presentations on im-aging which makes it difficult to diagnose. Therefore, aradiologist’s role is pivotal in recognizing its common radi-ographic features and to include NTM infection, and specif-ically M. simiae infection in the differential diagnosis in theendemic countries. Finally, it is imperative to recognize thatM. simiae can affect immunocompetent patients.

REFERENCES1. Larsson L-O, Polverino E, Hoefsloot W et al. Pulmonary

disease by non-tuberculous mycobacteria – clinical man-agement, unmet needs and future perspectives. ExpertRev Respir Med 2017; 11: 977-89.

2. Shitrit D, Peled N, Bishara J et al. Clinical and radiolog-ical features of Mycobacterium kansasii infection andMycobacterium simiae infection. Respir Med 2008; 102:1598-603.

3. Haworth CS, Banks J, Capstick T et al. British ThoracicSociety Guideline for the management of non-tubercu-lous mycobacterial pulmonary disease (NTM-PD). OpenRespir Res 2017; 4: e000242.

4. Samra Z, Kaufman L, Pitlik S, Shalit I, Bishara J. Emer-gence of Mycobacterium simiae in respiratory speci-mens. Scand J Infect Dis 2005; 37: 838-41.

5. Hashemi-Shahraki A, Darban-Sarokhalil D, Heidarieh P,et al. Mycobacterium simiae: a possible emerging path-ogen in Iran. Jpn J Infect Dis 2013; 66: 475-9.

6. Baghaei P, Tabarsi P, Farnia P et al. Pulmonary diseasecaused by Mycobacterium simiae in Iran’s national referralcenter for tuberculosis. J Infect Dev Ctries 2011; 6: 23-8.

7. Thomson R. NTM working group at Queensland TBControl Centre and Queensland Mycobacterial Reference

Laboratory. Changing epidemiology of pulmonary non-tuberculous mycobacteria infections. Emerg Infect Dis2010; 16: 1576-83.

8. Mycobacteria. N. American Thoracic Society. Am JRespir Crit Care Med 1997; 156: S1-S25.

9. Hillis SL, Obuchowski NA, Schartz KM, Berbaum KS.A comparison of the Dorfman-Berbaum-Metz andObuchowski-Rockette methods for receiver operatingcharacteristic (ROC) data. Stat Med 2005; 24: 1579-607.

10. Tanaka E, Amitani R, Niimi A, Suzuki K, Murayama T,Kuze F. Yield of computed tomography and broncho-scopy for the diagnosis of Mycobacterium avium com-plex pulmonary disease. Am J Respir Crit Care Med1997; 155: 2041-6.

11. Fujita J, Ohtsuki Y, Suemitsu I et al. Pathological andradiological changes in resected lung specimens inMycobacterium avium intracellulare complex disease.Eur Respir J 1999; 13: 535-40.

12. Fujita J, Ohtsuki Y, Shigeto E et al. Pathological findingsof bronchiectases caused by Mycobacterium avium intra-cellulare complex. Respir Med 2003; 97: 933-8.

13. Moore E. Atypical mycobacterial infection in the lung:CT appearance. Radiology 1993; 187: 777-82.

14. Christensen EE, Dietz GW, Ahn C, Chapman JS, MurryRC, Hurst GA. Radiographic manifestations of pulmo-nary Mycobacterium kansasii infections. Am J Roentgenol1978; 131: 985-93.

15. Christensen EE, Dietz GW, Ahn CH et al. Pulmonarymanifestations of Mycobacterium intracellularis. Am JRoentgenol 1979; 133: 59-66.

16. Christensen EE, Dietz GW, Ahn CH et al. Initial roent-genographic manifestations of pulmonary Mycobacte-rium tuberculosis, M. kansasii, and M. intracellularisinfections. CHEST 1981; 80: 132-6.

17. Woodring J, Vandiviere H, Melvin I, Dillon M. Roent-genographic features of pulmonary disease caused byatypical mycobacteria. South Med J 1987; 80: 1488-97.

18. Miller Jr WT. Spectrum of pulmonary nontuberculousmycobacterial infection. Radiology 1994; 191: 343-50.

19. Albelda S, Kern J, Marinelli D, Miller W. Expandingspectrum of pulmonary disease caused by nontubercu-lous mycobacteria. Radiology 1985; 157: 289-96.

20. Hartman TE, Swensen SJ, Williams DE. Mycobacteriumavium-intracellulare complex: evaluation with CT. Radio-logy 1993; 18 : 23-6.

21. Wittram C, Weisbrod G. Mycobacterium avium complexlung disease in immunocompetent patients: radiography– CT correlation. Br J Radiol 2002; 75: 340-4.

22. Prince DS, Peterson DD, Steiner RM et al. Infection withMycobacterium avium complex in patients without pre-disposing conditions. N Engl J Med 1989; 321: 863-8.

23. Maoz C, Shitrit D, Samra Z et al. Pulmonary Mycobacte-rium simiae infection: comparison with pulmonary tubercu-losis. Eur J Clin Microbiol Infect Dis 2008; 27: 945-50.

24. Baghizadeh A, Mehrian P, Farnia P. Computed tomogra-phy findings of pulmonary Mycobacterium simiae infec-tion. Can Respir J 2017.

25. Jeong YJ, Lee KS, Koh W-J, Han J, Kim TS, Kwon OJ.Nontuberculous mycobacterial pulmonary infection inimmunocompetent patients: comparison of thin-section CTand histopathologic findings. Radiology 2004; 231: 880-6.

26. Ellis S, Hansell D. Imaging of non-tuberculous (atypical)mycobacterial pulmonary infection. Clin Radiol 2002;57: 661-9.

A. BAASSIRI. et al. – Imaging appearance of M. simiae pulmonary infection Lebanese Medical Journal 2018 • Volume 66 (5) 259