|Year : 2014 | Volume
| Issue : 1 | Page : 56-58
Mycobacterium riyadhense lung infection in a patient with HIV/AIDS
Musa Abubakar Garbati, Ahmed Musa Hakawi
Department of Medicine, King Fahad Medical City, Riyadh, Saudi Arabia
|Date of Submission||08-Nov-2013|
|Date of Acceptance||16-Dec-2013|
|Date of Web Publication||24-Mar-2014|
Musa Abubakar Garbati
Department of Medicine, Section of Infectious Diseases, King Fahad Medical City, Riyadh - 11525
Mycobacterium riyadhense was first isolated in 2009. Five additional cases were reported since then. This is, however, the first case of M. riyadhense with human immunodeficiency virus coinfection in the literature. A 54-year-old male diabetic presented with 4 months history of diarrhea, productive cough, odynophagia, and dysphagia with progressive weight loss. He looked cachectic with oropharyngeal thrush, bilateral axillary lymph node enlargement and herpes zoster involving the first two thoracic dermatomes. He had right-sided consolidation on chest examination. He was anemic with a normal platelet count. Sputum examination was positive for acid-fast bacilli (AFB); however, deoxyribonucleic acid probe-detection assay for MTB (complex) was negative. The isolate was confirmed as M. riyadhense at the Bioscientia laboratories (Ingelheim, Germany). Stool was positive for Clostridium difficile toxins by polymerase chain reaction (PCR). Human immunodeficiency virus (HIV) test was also positive. The patient showed improvement in clinical, bacteriologic, and immunologic parameters with antituberculous and antiretroviral medications. The lesson from this case is for clinicians to suspect infection with atypical mycobacteria once mycobacterium tuberculosis (MTB) PCR is negative in a patient with a positive smear for AFB so that appropriate therapy for nontuberculous mycobacterial disease can be initiated early.
Keywords: Atypical mycobacteria, HIV/acquired immune deficiency syndrome, M. riyadhense
|How to cite this article:|
Garbati MA, Hakawi AM. Mycobacterium riyadhense lung infection in a patient with HIV/AIDS. Sub-Saharan Afr J Med 2014;1:56-8
|How to cite this URL:|
Garbati MA, Hakawi AM. Mycobacterium riyadhense lung infection in a patient with HIV/AIDS. Sub-Saharan Afr J Med [serial online] 2014 [cited 2020 May 28];1:56-8. Available from: http://www.ssajm.org/text.asp?2014/1/1/56/129324
| Introduction|| |
Mycobacterium riyadhense a nonchromogenic, slowly growing nontuberculous mycobacterium (NTM), was first isolated in 2009 from maxillary sinus lavage fluid of a 19-year-old male with jaw swelling.  Five additional cases have been reported ,,, since then making this the seventh in the literature. M. riyadhense has established itself as an emerging pathogen with the potential to cause infection at both extrapulmonary and pulmonary sites, with six out of the seven cases manifesting as pulmonary infections.
M. riyadhense, M. szulgai, M. kansasii, and M. malmoense are closely related phylogenetically making them among the most pathogenic NTM. , The pathogenicity of M. riyadhense has further been established with the presence of a region of difference 1 (RD1), a region harboring the early secretory antigen target (ESAT-6) and culture filtrate protein (CFP-10) genes, which are important virulence factors in M. tuberculosis,, and thought to equally play a crucial role in the virulence of NTM, such as M. riyadhense.  Deletion of RD1 lowers the virulence of M. tuberculosis complex bacteria, ,, suggesting that this site is involved in pathogenesis.
We, hereby, report the first case of infection with M. riyadhense in a patient with human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS).
| Case Report|| |
A 54-year-old male diabetic, presented with productive cough, chronic diarrohea, and weight loss. Examination was positive for cachexia, oropharyngeal thrush, peripheral lymphadenopathy and herpes zoster of the left first and second thoracic dermatomes. His HIV screening and confirmatory tests were positive. [Table 1] shows his immunologic and virologic parameters with reference values compared to the local population.  Polymerase chain reaction (PCR) for respiratory viruses from bronchoalveolar lavage (BAL) fluid was negative. Stool examination was negative for parasites but positive for Clostridium difficile toxins by PCR.
Smears from BAL fluid were positive for acid-fast bacilli (AFB) and culture yielded mycobacterial species; however, deoxyribonucleic acid (DNA) probe-detection assay for Mycobacterium tuberculosis (MTB) complex was negative. Further speciation of the mycobacterium at the National Reference Centre for Mycobacteria, Borstel, Germany, using molecular methods identified the isolate as M. riyadhense. The identification was done by amplification of a fragment of the gene coding for 16S rRNA (1200bp) and sequenced. The resulting sequence-matched best with M. riyadhense, with 1 bp difference to the database sequence according to CLSI guidelines. 
Plain radiograph and computerized tomographic (CT) scan of the chest showed right apical cavitary disease. Conventional antituberculosis (ATT) regimen [Rifampin (R), Isoniazid (H), Pyrazinamide (Z) and Ethambutol (E)] was started and followed with a highly active antiretroviral therapy (HAART) combination of truvada (emtricitabine and tenofovir) and efavirenz 4 weeks later with no adverse effects. Following full identification of the mycobacterium the regimen was changed to ethambutol, isoniazid and rifampicin (EHR) and clarithromycin during the intensive phase and ER and clarithromycin continued for a total duration of one year with complete resolution of radiologic features. Trimethoprim-sulphamethoxazole was added as primary prophylaxis until CD4 count level rose above 200 cells per micro liter for consecutive 3 months. Sputum conversion was achieved after 4 weeks of therapy. The patient has remained symptom-free 2 years after discontinuing antimycobacterial therapy. A Table summarizing all previously reported M. riyadhense infections has been included as [Table 2].
|Table 2: Country of isolation, Year of publication, Site of infection, treatment and outcome of cases of Mycobacterium riyadhense infection|
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| Discussion|| |
Although this is the seventh case of infection with M. riyadhense in the literature, it is, however, the first to be coinfected with HIV. For a patient with suspected NTM lung disease, the following have to be met: (1) chest radiograph or, in the absence of cavitations, high resolution CT scan of the chest; (2) three or more sputum specimens for AFB analysis; and (3) exclusion of other disorders, such as TB. Several samples from sputum and BAL fluid were positive for AFB smear and culture, in addition to the consistent clinical and radiologic features, thus fulfilling the American Thoracic Society diagnostic criteria for NTM lung disease.  In the setting of typical symptoms and chest CT findings of fibronodular opacities or cavitary disease, a patient with one positive culture from bronchoalveolar lavage (or two positive cultures from sputum) now meet diagnostic criteria. 
The lack of commercially available kits, like DNA sequencing, to facilitate a timely and rapid diagnosis for new and emerging species of NTM including M. riyadhense often results in delayed diagnosis and initiation of standard ATT which could be insufficient. ,,, Whereas in vitro drug susceptibility tests are basically used for the choice of therapy for the rapid growers, the same cannot be said of the slow growers due to discrepancies arising from laboratory technical difficulties of drug susceptibility testing (DST), standardization of methods, and a lack of clinical validation.  It is, however, important to note that even though breakpoints for the susceptibility of M. riyadhense have not been established extrapolations can be made from results for M. kansasii (rifampicin) and M. avium complex (clarithromycin) as reported by van Ingen et al., in a recent review.
| Conclusion|| |
Improved techniques for the identification of emerging NTM strains have led to the isolation of new members of this rapidly expanding bacterial group. This is the seventh case of M. riyadhense infection in the literature but the first to be coinfected with HIV. A combination of HAART and antituberculosis medications led to clinical, virologic, microbiologic, and radiologic improvement. The lesson from this case is that negative results of MTB (complex) PCR in a patient with positive smear should prompt a suspicion of infection due to NTM so that appropriate antimicrobials can be administered.
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[Table 1], [Table 2]