Myobacterium kansasii as the Primary Etiology of Pulmonary Infections due to Non-Tuberculous Mycobacterium (NTM) in Patients WIthout Human Immunodeficiency Virus (HIV): Experience from a Center in Buenos Aires, Argentina

Introduction: Pulmonary diseases due to non-tuberculous mycobacterium (NTM) lung infection in HIV-negative patients are rarely described in the literature. Currently, NTM consist of more than 150 species, and they are globally ubiquitous in both natural and man-made environments.The objective of this study was to define the most frequent species of NTM causing pulmonary disease in HIVnegative patients in the city of Buenos Aires, Argentina. The prevalence of pulmonary diseases caused by NTM is difficult to determine since the isolation of NTM does not necessarily indicate disease. Methods: A retrospective review of all the respiratory cultures positive for NTM in the Bacteriology Laboratory of Posadas Hospital between January 2010 and December 2015 was performed. 31 patients without Human Immunodeficiency Virus (HIV) from whom NTM was isolated in respiratory samples, which fulfilled diagnostic criteria for NTM disease were included. Results: The mean age was 50 years at the time of the diagnosis (SD ± 17.2); and 19 patients (61.3%) were males. Mycobacterium kansasii was the most commonly isolated NTM (68%) followed by Mycobacterium avium Complex (MAC) (19%). M. kansasii was the most common cause of pulmonary infection by NTM in these HIV-negative patients. Cultures should be performed to identify the species and to treat accordingly. 46% of the patients included in the study, there was no evidence of risk factors. Only 32% of the subjects had respiratory comorbidities, and the most common radiologic finding was cavitation (55%). Discussion: Our study indicates that M. kansasii is the primary etiology of NTM pulmonary disease in HIV-negative patients in our service area in Buenos Aires. This finding supports the consideration that patients with symptoms compatible with pulmonary tuberculosis should also be evaluated for NTM with appropriate acid-fast bacilli cultures, as treatment regimens differ vastly according to the specific pathogen isolated, although clinical and radiographic presentations may have overlapping features. The possibility of M. kansasii pulmonary disease or other NTM should be considered in patients treated empirically for TB without appropriate clinical response. DOI: 10.18297/jri/vol2/iss1/5 Received Date: February 12, 2018 Accepted Date: March 17, 2018 Website: https://ir.library.louisville.edu/jri Affiliations: 1Alejandro Posadas National Hospital, Buenos Aires, Argentina ©2018, The Author(s). 21 ULJRI Vol 2, (1) 2018 ORIGINAL RESEARCH *Correspondence To: Alejandra González Work Address: Alejandro Posadas National Hospital, Buenos Aires, Argentina, Work Email: alestork@yahoo.com.ar common NTM cause of pulmonary disease worldwide [5]. It is difficult to compare the incidence and prevalence of NTM diseases across geographic areas. Because reporting NTM disease to public health authorities is not required in most countries, studies of the incidence and prevalence of NTM disease are performed differently in different countries. To compare reports regarding changes in the incidence and prevalence of NTM disease over time in a limited geographic area, one must compare reports that used the same methods. Many epidemiological reports and reviews have shown that NTM disease have been increasing since the 1950s [1,6]. The clinical significance of NTM isolation is not always clear and it is difficult to assess the incidence or prevalence of NTM disease due to several factors, notably its difficulty in differentiation from colonization. Although the detection of NTM colonies has been increasing since the 1950s [6] it is unclear why NTM disease have been increasing in humans. There are several potential contributing factors, such as, (i) an increase of mycobacterial infection sources in the environment, (ii) an increase in susceptible individuals, such as those Human Immunodeficiency Virus (HIV) positive, (iii) improvements in detection methods and laboratory equipment sensitivities (iv) an increasing life expectancy of those with chronic structural pulmonary disease (v) an increased awareness of NTM diseases [1,7]. In many countries, especially those in high-burden areas for TB, the diagnosis of TB is mainly based on the detection of acid-fast bacilli in a sputum smear, as well as on their symptoms and the results of a chest X-ray [1]. Pulmonary diseases caused by NTM could be presumptively treated as pulmonary tuberculosis (TB) as the microbiologic smear of the sputum does not distinguish NTM from TB, and the clinical manifestations are similar. In Latin America the prevalence of NTM is estimated to be much lower than that of TB. The incidence of tuberculosis in Argentina is of 23,91/ 100,000 inhabitants with wide regional variations. In the province of Buenos Aires, it is 30,27/100,000 inhabitants. There are differences in the relative abundances of mycobacterial species that cause NTM diseases across geographic areas, the NTM distribution is most notably associated with variants in environmental factors such as, soil and water distribution systems [1,7]. Pulmonary diseases due to NTM in HIV-negative patients are rarely described in the literature [8]. The objective of this study was to define the most frequent species of NTM causing pulmonary disease in HIV-negative patients in the city of Buenos Aires, Argentina. Materials and Methods A retrospective review of all the respiratory cultures positive for NTM in the Bacteriology Laboratory of Posadas Hospital between January 2010 and December 2015 was performed. Posadas Hospital is a high complexity hospital with 500 admission beds and a service area covering a population of approximately 4,400,000. IRB approval was obtained for this study. Patients older than 15 years old that fulfilled the ATS/IDSA diagnostic criteria for pulmonary disease due to NTM were included in the study [2]. All patients in the study were screened for HIV and we excluded those who presented with positive HIV serology. The method utilized to perform the cultures was the BACTEC MGIT (fluorescence) in addition to solid culture media (Lowenstein Jensen). Lateral flow immunoassay (LFA) were performed on positive cultures to differentiate NTM from TB. The following variables were analyzed: age, sex, NTM species, and clinical and radiological characteristics. For the categorical variables, we used percentages as frequency measurements. The continuous variables were expressed as mean or median depending on the sample distribution. Statistical analysis was performed using the computing environment R version 3.4.3 software [9].