Results of the external quality assessment of Mycobacterium tuberculosis drug susceptibility testing in Russia, 2005-2007

SETTING

External quality assessment (EQA) of Mycobacterium tuberculosis drug susceptibility testing (DST) in bacteriological tuberculosis (TB) laboratories in the Russian Federation.

OBJECTIVE

To improve the EQA of DST of first-line anti-tuberculosis drugs using proficiency testing in the Russian Federation.

METHOD

Three rounds of DST proficiency testing using Mycobacterium tuberculosis isolates provided by the Swedish Institute for Infectious Disease Control, a World Health Organization Supranational Reference Laboratory (SRL). In total, 42 TB laboratories in the Russian civilian and prison sectors participated in at least one round of proficiency testing, and 17 laboratories participated in all three rounds.

RESULTS

Ninety-seven per cent (87/89) of reports were received for the three rounds: 67% of laboratories in the first round and 86% of laboratories in the second round demonstrated >or=95% accuracy for isoniazid, and respectively 72% and 80% of laboratories in the first and second rounds reported >or=95% accuracy for rifampicin.

CONCLUSION

Coordination with the SRL network resulted in the introduction of 90 well-characterised strains for EQA in the Russian Federation. Successive rounds of DST proficiency testing have helped to identify highly proficient laboratories that will be used as expert laboratories for proficiency testing in the future.

Low-molecular-weight trypsin inhibitors of microbial origin

Three hundred actinomyces cultures newly isolated from the soil of different regions of the Soviet Union were tested for their ability to produce inhibitors of trypsin-like proteases. Seven previously not known to produce trypsin inhibitors (Streptomyces bikiniensis 17-5, S. sporoclivatus 28-1, S. filamentosus 32-11, S. diastatochromogenes 20-4, S. lavendulae 29-4, S. violacens 52-8, and Streptoverticillium cinnamoneum 36-8) were found to possess high antitrypsin activity. The morphological and cultural properties of the strains and the dynamics of inhibitor production were investigated. S. bikiniensis 17-5 was studied in greatest detail. Its culture filtrate contained several inhibitors for trypsin and one for chymotrypsin. A mixture of oligopeptides with Mr of 300-500 was obtained by the described procedure which included the adsorption of the culture fluid filtrate on charcoal followed by ion-exchange chromatography on CM-cellulose. Four trypsin inhibitors (Sb-IT1, Sb-IT2, Sb-IT3, and Sb-IT4) were isolated from the mixture in a highly purified state by reversed-phase high-performance liquid chromatography. Sb-IT2 has been recognized as formylhistidylvaline with an Mr of 282. No trypsin inhibitor of this structure has been described previously.

Glucose effect in tgl mutant of Escherichia col K12 defective in methyl-alpha-D-glucoside transport

1. The dependence of the rate of accumulation of methyl-alpha-D-glucoside on its extracellular concentration was studied in the tgl mutant of Escherichia coli K12, isolated earlier. It has been shown that the kinetics of methyl-alpha-D-glucoside transport differ sharply from those in wild-type bacteria. 2. The beta-galactosidase synthesis in tgl strain is much less sensitive both to permanent and transient glucose catabolite repression. The level of cyclic AMP in mutant cells under the conditions of glucose catabolite repression is several times higher than in the parent strain. 3. The tgl mutation does not affect the manifestation of catabolite inhibition and inducer exclusion with glucose. 4. The data obtained are discussed in the light of a hypothesis concerning the existence of two sites, binding and pecific enzyme II of the phosphoenolpyruvate-dependent phosphotransferase system. The tgl mutation alters the first site, and the second one is damaged by the pgt mutation. 5. It is suggested that the products of the tgl and gpt genes are necessary for the manifestation of the phenomena of glucose permanent and transient repression. The effects of catabolite inhibition and inducer exclusion are realized irrespective of the existence or absence of the tgl product.