Rapid Detection and Immune Characterization of <i>Mycobacterium abscessus</i> Infection in Cystic Fibrosis Patients

<div><p>Cystic fibrosis patients are highly susceptible to infections with non-tuberculous mycobacteria. Especially <i>Mycobacterium abscessus</i> infections are common but reliable diagnosis is hampered by non-specific clinical symptoms and insensitive mycobacterial culture. In the present study we established novel methods for rapid detection and immune characterization of <i>Mycobacterium abscessus</i> infection in cystic fibrosis patients. We performed <i>Mycobacterium abscessus</i> specific DNA-strip- and quantitative PCR-based analyses of non-cultured sputum samples to detect and characterize <i>Mycobacterium abscessus</i> infections. Concomitantly <i>in vitro</i> T-cell reactivation with purified protein derivatives (PPDs) from different mycobacterial species was used to determine <i>Mycobacterium abscessus</i> specific T-cell cytokine expression of infected cystic fibrosis patients. Four of 35 cystic fibrosis patients (11.4%) were <i>Mycobacterium abscessus</i> culture positive and showed concordant DNA-strip-test results. Quantitative PCR revealed marked differences of mycobacterial burden between cystic fibrosis patients and during disease course. Tandem-repeat analysis classified distinct <i>Mycobacterium abscessus</i> strains of infected cystic fibrosis patients and excluded patient-to-patient transmission. <i>Mycobacterium abscessus</i> specific T-cells were detected in the blood of cystic fibrosis patients with confirmed chronic infection and a subgroup of patients without evidence of <i>Mycobacterium abscessus</i> infection. Comparison of cytokine expression and phenotypic markers revealed increased proportions of CD40L positive T-cells that lack Interleukin-2 expression as a marker for chronic <i>Mycobacterium abscessus</i> infections in cystic fibrosis patients. Direct sputum examination enabled rapid diagnosis and quantification of <i>Mycobacterium abscessus</i> in cystic fibrosis patients. T-cell <i>in vitro</i> reactivation and cytokine expression analyses may contribute to diagnosis of chronic <i>Mycobacterium abscessus</i> infection.</p>