Evaluation of a Molecular Test for Detection of Mycobacterium tuberculosis Isolates Resistant to Rifampicin and Isoniazid.

BACKGROUND: Multidrug-resistant tuberculosis (MDR-TB) is increasing worldwide and is a major cause of death in many countries. It has become a major challenge for national tuberculosis control programs. Therefore, rapid identification of MDR strains of Mycobacterium tuberculosis and monitoring of their transmission could contribute significantly to the fight against tuberculosis. The GenoType MTBDRplus assay has been recommended by the World Health Organization to identify rifampicin (RIF)- and isoniazid (INH)-resistant M. Tuberculosis isolates. The objectives of this study were to evaluate the performance of the GenoType MTBDRplus test in the detection of rifampicin and isoniazid resistance of M. tuberculosis isolates in a Moroccan hospital and then to determine the frequency of mutations associated with resistance to these two major anti-tuberculosis drugs. METHODS: This is a retrospective study conducted at the bacteriology department of the Mohammed V military hospital over a period of one year from 01/01/2018 to 12/31/2019. A total of 92 isolates of M. tuberculosis from pulmonary and extra-pulmonary specimens were evaluated for drug susceptibility by MGIT™ 960 AST system and compared to the GenoType MTBDRplus assay. The MGIT™ 960 AST system was used as the gold standard for the evaluation of the GenoType MTBDRplus assay. RESULTS: Sensitivity and specificity of the GenoType MTBDRplus assay for the detection of RIF-resistant M. tuberculosis isolates were 83.33% and 100%, respectively. Its sensitivity and specificity for the detection of INH-resistant M. tuberculosis were 88.23% and 100% respectively. The concordances of the GenoType MTBDRplus assay and the MGIT™ 960 AST system for the detection of sensitivity to RIF and INH were 99% (1/92) and 98% (2/92), respectively. Among the five RIF-resistant isolates, the MUT3 mutation in the rpoB gene (codon S531L mutation) was present in 80% of isolates, whereas mutations in the rpoB MUT1 gene were present in only one (20%) RIF-resistant isolate. INH resistance was detected in 15 isolates, of which nine isolates (60%) had specific mutations of the katG gene (codon S315T1) and conferred a high level of resistance to INH. CONCLUSIONS: The results of this study have shown that the GenoType MTBDRplus test has a high sensitivity and specificity for the detection of resistance to RIF and INH.

Breast tuberculosis: A forgotten diagnosis.

Breast tuberculosis is a rare entity even in endemic countries. It is often considered as a diagnostic conundrum given the non-specific clinical and imaging characteristics. Therefore, the definitive diagnosis is based on the identification of bacilli by microbiological or histopathological examination. We report the case of a 52-year-old woman, with a 2-month history of a painful lump of the left breast. The imaging features were consistent with a breast abscess. The purulent collection was aspirated and a tuberculous mammary abscess was diagnosed by molecular biology (GeneXpert). Through this observation, we discuss the clinical, radiological and biological signs by highlighting the contribution of molecular biology in the rapid management of this rare pathology.

The occurrence of a multidrug-resistant tuberculous retropharyngeal abscess in an immunocompetent patient: A case report.

Retropharyngeal abscess is an uncommon location of tuberculosis (TB). In this report, we describe a multidrug-resistant tuberculous retropharyngeal abscess in a 21-year-old female patient who was treated for lymph node TB for one year. CT scan revealed a large retropharyngeal abscess that was aspirated intraorally under local anesthesia. The diagnosis of TB was retained by molecular and histological study. GeneXpert MTB/ RIF (Cepheid, Sunnyvale, CA, USA),performed on the pus, showed rifampicin resistance and a first- and second-line drug resistance test using Genotype MTBDRplus VER.2 and MTBDRsl VER.1 (Hain Lifescience GmbH, Nehren, Germany) showed TB highly resistant to rifampicin, isoniazid, and aminoglycosides. Treatment is primarily medical as it combines specific antituberculous antibiotics, and aspiration for drainage of the abscess. Our patient was put on long-term 2nd line anti-TB treatment.

A Case of Colonic Tuberculosis Revealed by Polymerase Chain Reaction.

BACKGROUND: The authors report a case of tumor-like colonic tuberculosis revealed by PCR in a 32-year-old patient with a low-level peritoneal effusion on CT scan with negative histological study on colonic biopsy. METHODS: The colonic biopsy received at the laboratory after grinding in a porcelain mortar, was the object of a molecular study by GeneXpert MT/RIF (Cepheid, Sunnyvale, CA, USA) using the automated real-time PCR technique and a conventional study based on Ziehl-Nielsen staining and culture on Lowenstein-Jensen® solid medium (LJ) and Mycobacteria Growth Indicator Tube (MGIT®) liquid medium. RESULTS: The patient was a 32-year-old male without any personal or family history of tuberculosis and without signs of tuberculosis impregnation. He had a story of ingestion of non-pasteurized dairy products including milk and cheese. For 45 days he had constipation with abdominal pain and feeling of heaviness. Physical examination of the patient revealed abdominal tenderness without adenopathy. The laboratory workup showed a normal blood count, CRP, liver and kidney function tests. The HIV test was negative. Medical imaging revealed a low-level peritoneal effusion that could not be punctured. Colonoscopy showed a thickening of the colon. The colonic biopsy, after crushing and sonication, was searched for the Mycobacterium tuberculosis complex by both molecular biology and conventional methods. Molecular research by GeneXpert MTB/RIF (Cepheid, Sunnyvale, CA, USA) using the automated real-time PCR technique, revealed the presence of the Mycobacterium tuberculosis complex without detection of rifampicin resistance. On the other hand, the direct examination after special Ziehl-Nielsen staining was positive (Figure 2) and the cultures on Lowenstein-Jensen® solid medium (LJ) and Mycobacteria Growth Indicator Tube (MGIT®) liquid medium were also positive after two and three weeks, confirming the molecular diagnosis. The histology study showed moderate non-specific chronic colitis with no histological arguments for tuberculosis or malignancy. The patient was placed on curative tuberculosis treatment according to the national protocol, with a favorable clinical-radiological course. CONCLUSIONS: Colonic tuberculosis is a disease that may mimic many other diseases; therefore, a correct approach is necessary for the correct diagnosis and treatment.

Whole-Genome Sequencing of Two Moroccan Mycobacterium tuberculosis Strains.

Mycobacterium tuberculosis is known to cause pulmonary and extrapulmonary tuberculosis. In Morocco, the spread of multidrug-resistant (MDR) tuberculosis (TB) has become a major challenge. Here, we announce the draft genome sequences of two Mycobacterium tuberculosis strains, MTB1 and MTB2, isolated from patients with pulmonary tuberculosis in Morocco, to describe variants associated with drug resistance.

Annotated Whole-Genome Shotgun Sequence of Multidrug-Resistant Mycobacterium tuberculosis MTB13_M Isolated from Morocco.

Here, we describe the annotated genome sequence of Mycobacterium tuberculosis MTB13_M. The organism was isolated from a sputum sample in Morocco.