Abstract
BackgroundThe establishment of therapeutic regimens for mycobacteriosis depends on the accurate identification of Mycobacterium species, and misdiagnosis can result in inappropriate treatment and increased mortality of patients. Differential diagnosis among Mycobacterium species has been made by conventional phenotypic and biochemical tests after a long culture period. Specialized molecular diagnostics of mycobacteria allows rapid detection and species identification; however, such tests are not available in public health programs. Our aim was to demonstrate the clinical implications of erroneous diagnosis by performing molecular genotyping of mycobacterial infections in patients that were diagnosed based on symptoms, culture and bacilloscopy.MethodsCulture samples of mycobacterial infections from 55 patients clinically diagnosed as tuberculosis in 2013 and 2014, based on conventional methods, were identified by PCR -RFLP and results are discussed.ResultsWe have confirmed 35 (63.6 %) positive samples as M. tuberculosis, but 18 (32.7 %) were identified as non-tuberculous mycobacteria (M. avium type 1, M. avium type 2, M. kansasii type 1 type 1, M. mucogenicum, M. chelonae, M. terrae type 3, and 1 unknown RFLP pattern) and two were negative. Regarding clinical diagnosis, 61.8 % (34/55) was classified as pulmonary tuberculosis. It is important to emphasize that 36.4 % (20/55) of samples were misdiagnosed by conventional methods, and 11 (61.1 %) of the HIV positive patients (18/55) were NTM-coinfected.ConclusionThe identification of species in mycobacterial infections is essential for correct diagnosis and choice of treatment regimen, and misdiagnosis by conventional tools can lead to chronic disease, increased resistance and death.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-016-1474-6) contains supplementary material, which is available to authorized users.
Highlights
The establishment of therapeutic regimens for mycobacteriosis depends on the accurate identification of Mycobacterium species, and misdiagnosis can result in inappropriate treatment and increased mortality of patients
This study aimed to identify species of mycobacteria present in samples of positive cultures from patients diagnosed with tuberculosis treated at the Clinical Hospital of the Federal University of Uberlândia in the biennium 20132014, and discuss the implications of misdiagnosis by using only conventional bacilloscopy and culture methods
Patients’ data In the period of 2013 to 2014, 55 positive mycobacterial cultures were obtained from patients diagnosed with tuberculosis attended at the Clinics’ Hospital of the Federal University of Uberlândia
Summary
The establishment of therapeutic regimens for mycobacteriosis depends on the accurate identification of Mycobacterium species, and misdiagnosis can result in inappropriate treatment and increased mortality of patients. Specialized molecular diagnostics of mycobacteria allows rapid detection and species identification; such tests are not available in public health programs. The diagnostic methods used are bacilloscopy and microbiological culture [9], but the main method for bacilli detection is the Ziehl-Neelsen specific staining technique; despite its simplicity and low cost, it has a very low sensitivity (30 to 50 % of the M. tuberculosis cases are negative). The microbiological culture is generally used in suspected pulmonary cases and in negative bacilloscopy, and allows detection and isolation of mycobacteria for subsequent identification of the isolated complex [9]. Automated detection systems of mycobacteria, such as the BACTEC 460 TB®, BACTEC 9000®, and the MGIT® are promising, but they can produce false-positive results due to contamination by other bacteria [9]
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