Spread of an emerging Mycobacterium tuberculosis drug-resistant strain in the western Cape of South Africa.

BACKGROUND: South Africa has a high burden of drug-resistant tuberculosis (TB). METHODS: Routine drug susceptibility testing was performed prospectively over a 2-year period on Mycobacterium tuberculosis isolates in two health districts of the Western Province, South Africa. A cluster of drug-resistant strains that shared a rare mutation in katG315 was found in 64 of the 450 cases identified as having been infected with drug-resistant TB. Isolates belonging to this cluster were phenotypically and genotypically characterised. Epidemiological and clinical characteristics were used to identify mechanisms leading to the acquisition and spread of this drug-resistant strain. RESULTS: An outbreak of an emerging non-Beijing drug-resistant strain infecting 64 pulmonary tuberculosis (PTB) cases was identified. This previously undetected genotype (now designated DRF150) is characterised by five IS6110 insertions, specific spoligotypes and high levels of resistance to the first-line TB medications isoniazid, streptomycin and rifampicin. In 45% of the cases it is also resistant to ethambutol and pyrazinamide. Key factors leading to the development and spread of this drug-resistant genotype were inappropriate chemotherapy, poor adherence to treatment and prolonged periods of infectiousness due to delays in susceptibility testing. CONCLUSIONS: Molecular markers allowed early identification of an emerging non-Beijing drug-resistant strain.

Ethambutol resistance testing by mutation detection.

OBJECTIVE: To identify chromosomal mutations that confer resistance to ethambutol (EMB) in Mycobacterium tuberculosis. DESIGN: Drug-resistant (n = 235) and drug-susceptible (n = 117) M. tuberculosis isolates collected from the Western Cape in South Africa were subjected to embB gene analysis and the results were compared to phenotypic EMB testing. RESULTS: Genotypic analysis identified mutations at codon 306 of the embB gene in 20% (47/235) of the resistant isolates in comparison to only 1.7% (4/235) of those that were phenotypically resistant to EMB by the agar diffusion method. No gene mutations were detected in susceptible isolates. Phenotypic retesting in BACTEC demonstrated that the 47 genotypically resistant isolates were phenotypically resistant to EMB. This implies that 91.4% (43/47) of EMB resistance had been phenotypically missed by routine laboratory procedures. EMB resistance was closely linked to multidrug resistance (MDR); 87.2% (41/47) of the EMB-resistant isolates were resistant to both isoniazid and rifampicin. A newly developed one-step amplification refractory mutation system polymerase chain reaction (ARMS-PCR) method correctly detected the EMB-resistant genotype. CONCLUSION: Implementation of more accurate diagnosis of EMB resistance may enhance patient management in South Africa, as standardised treatment of MDR-TB with second-line drugs is currently dependent on the outcome of the EMB resistance test.

Genotypic and phenotypic characterization of drug-resistant Mycobacterium tuberculosis isolates from rural districts of the Western Cape Province of South Africa.

Genotypic and phenotypic analysis of drug-resistant Mycobacterium tuberculosis isolates from the Western Cape Province of South Africa showed that drug resistance is widespread and recently transmitted. Multidrug-resistant (MDR) isolates comprise 40% of this collection, and a large pool of isoniazid monoresistance may be a future source of MDR tuberculosis.

Depolarization- and ionophore-induced release of octacosa somatostatin from stalk median eminence synaptosomes.

Species of somatostatin of higher molecular weight were present in the nerve terminals (synaptosomes) of ovine stalk median eminences and were released by depolarizing stimuli. One of these species was identified as the biologically active molecule octacosa somatostatin. Octacosa somatostatin appears therefore to be secreted into the hypothalamic-hypophyseal system, supporting the concept of a role for this peptide in regulating pituitary hormone secretion.

A radio-immunoassay of 17-alpha-hydroxyprogesterone.

A method is described for the determination of 17 alpha-hydroxyprogesterone (17-OHP) in plasma. Antisera were raised in rabbits against 11-deoxycortisol-21-hemisuccinate-bovine serum albumin (11-DOC-21-HS-BSA) and 17 alpha-hydroxyprogesterone-3-carboxymethyloxime-bovine serum albumin (17-OHP-3-CMO-BSA). An antiserum to 11-DOC-21-HS-BSA exhibited cross-reaction with progesterone (29%), 11-deoxycortisol (100%), cortisol (17%) and testosterone (10%) and was therefore not appropriate for quantitation of 17-OHP in plasma. An antiserum to 17-OHP-3-CMO-BSA cross-reacted with progesterone (9,7%), 11-deoxycortisol (50%) and less than 1% with all other major naturally occurring steroid hormones. A radio-immunoassay (RIA) was developed using the antiserum to 17-OHP-4-CMO-BSA. The intra-assay and interassay coefficients of variation were 7,2% and 10,5% respectively. The normal ranges (nmol/l plasma) of samples extracted with hexane:benzene (1:1) and purified by Sephadex LH-20 chromatography were 0,28-4,7 for men, 0,84-3,0 for women (follicular phase), 3,0-11,0 for women (luteal phase), 4,6-22,1 for pregnant women, 18,5-123,9 for cord blood, 0,12-5,0 for children and 56,3-1 032 for persons with congenital adrenal hyperplasia (CAH) due to a 21-hydroxylation enzyme defect. Sephadex LH-20 purification of plasma extracts could be omitted when using the RIA as a screening procedure for CAH due to a 21-hydroxylation enzyme defect.