Study of resistance to anti-tuberculosis drugs in five districts of Equatorial Guinea: rates, risk factors, genotyping of gene mutations and molecular epidemiology.

SETTING: Five districts in Equatorial Guinea, March 1999 to February 2001. OBJECTIVES: To determine tuberculosis drug resistance among new and previously treated cases, the risk factors associated with resistance, and the mutations associated with isoniazid and rifampicin (katG, inhA and rpoB genes) resistance, and to genotype resistant strains. RESULTS: A positive culture identified as Mycobacterium tuberculosis complex was obtained in 240/499 patients. Susceptibility testing was performed in 236 strains. The overall resistance rate in new cases was 16.9% compared to 41.6% in previously treated cases. Isoniazid resistance was the most frequent (respectively 12.5% and 16.6%) in the two groups, while multidrug resistance was observed in 1.7% and 25% of new and previously treated cases, respectively. Female sex was statistically associated with resistance in new cases. Of 41 isoniazid-resistant strains, 33 (80.5%) had mutations in the inhA gene; none had mutations in the katG gene and eight had no mutations in either gene. All strains had low-level isoniazid resistance. Of eight strains resistant to rifampicin, six had mutations in the rpoB gene. Genotyping defined seven clusters. CONCLUSIONS: Moderate resistance was found in new cases. Low-level isoniazid resistance predominated among mutations in the inhA gene, with a high percentage of clustering in resistant strains.

Molecular epidemiology of tuberculosis in the Bata and Malabo districts of Equatorial Guinea.

SETTING: Bata and Malabo districts, Equatorial Guinea, 1 March 1999 to 28 February 2001. OBJECTIVE: To study the molecular epidemiology of tuberculosis (TB). RESULTS: During the study period, 429 patients were diagnosed with TB in the Bata and Malabo districts. A positive culture was obtained in 206 (48%) TB patients, with RFLP analysis being performed in 185 (89.8%). Ninety-two different patterns were identified. Single patterns were found in 71 strains (38.3%) and the remaining 114 strains (61.6%) were classified into 21 clusters (of 2 to 25 patients). In addition, 37 of the typing strains were resistant to one or more anti-tuberculosis drugs, and 30 were included in clusters (81%), with 21 low level isoniazid (MIC < or = 1 microg/ml) resistance strains in the same cluster. Statistical analysis showed that resistance to anti-tuberculosis drugs (OR 3.1; 95% CI 1.2-7.6; P = 0.014), and positive smear results (4+ grade smear) (OR 4.3; 95% CI 1.5-12; P = 0.005), were significantly more frequent among patients with clustered strains. No epidemiological links were related to clustering. CONCLUSIONS: The level of clustering (61.6%) observed suggests a high degree of recent transmission and a predominance of determined patterns of Mycobacterium tuberculosis strains among the population of Equatorial Guinea.

Physiological concentration of nitric oxide induces positive inotropic effects through cGMP pathway in isolated rat ventricular myocytes.

We used authentic NO or NO from NO donors to show that the physiological levels of NO (<1 microM) induce a positive inotropic effect and demonstrated that the effect is evoked through a cGMP-dependent pathway. In isolated rat ventricular myocytes, authentic NO at 588 nM increased both cell shortening and the intracellular Ca(2+) ([Ca(2+)]i) transient (133 and 117%, respectively; p < 0.05 vs. baseline), and 0.16-1.7 microM NO elicited reproducible dose-dependent increases in cell shortening. NOC18 (0.1 mM: actual NO concentration 673 nM) or SNAP (0.1 mM: actual NO concentration 285 nM) showed similar effects (shortening 215% and [Ca(2+)]i transient 160% increases, and shortening 148% and [Ca(2+)]i transient 117% increases, respectively). The NO-induced increases in cell shortening and the [Ca(2+)]i transient were inhibited by an inhibitor of soluble guanylate cyclase (ODQ, 30 microM) or by an inhibitor of cAMP-dependent protein kinase (KT5720, 0.1 microM). In the presence of an inhibitor of cGMP-inhibited cAMP-phosphodiesterase (milrinone, 10 microM), NO failed to increase both cell shortening and the [Ca(2+)]i transient. These results suggest that physiological levels of NO induce positive inotropy through a cGMP-dependent pathway.