Nosocomial outbreak of multidrug-resistant tuberculosis caused by a strain of Mycobacterium tuberculosis W-Beijing family in St. Petersburg, Russia.

A molecular epidemiologic study of 35 Mycobacterium tuberculosis isolates from 19 patients was conducted to define a nosocomial outbreak of multidrug-resistant tuberculosis in St. Petersburg, Russia. IS 6110-restriction fragment length polymorphism (RFLP) fingerprinting, together with investigations to detect mutations conferring drug resistance, revealed relationships between the isolates and links between the cases. Three patients and a nurse exposed to active tuberculosis were proved to be involved in the outbreak; the source case was identified. The outbreak strain possessed a 17-band RFLP pattern and a spoligoprofile (signals 35-43) characteristic of the W-Beijing family as well as distinctive mutations in katG315, rpoB531, embB306 and rpsL43. This specific RFLP pattern has previously been identified among Mycobacterium tuberculosis W-Beijing strains isolated across the former Soviet Union and in the St. Petersburg area of Russia. The spread of multidrug-resistant strains of W-Beijing genotype in the general population and in hospital settings presents a serious threat for public health in Russia. Specific pathogenic properties of W-Beijing genotype strains, such as enhanced transmissibility and the ability to cause reinfection and to readily acquire drug resistance to major antituberculosis drugs, along with special features of host response, have yet to be investigated.