Recent and rapid emergence of W-Beijing strains of Mycobacterium tuberculosis in Cape Town, South Africa.

Background: There is increasing evidence of a strain-related variation in the virulence in Mycobacterium tuberculosis that may afford a selective advantage to certain strains. The W-Beijing strain family is globally distributed, highly virulent in animal models, associated with human immunodeficiency virus infection and drug resistance, and may be an emerging strain family. Our goal was to determine whether W-Beijing strains are expanding in a region of South Africa where rates of tuberculosis are among the highest in the world.

How reliable is a negative blood culture result? Volume of blood submitted for culture in routine practice in a children's hospital.

Objectives: The primary aims of this study were to determine the volume of blood submitted for culture in routine clinical practice and to establish the proportion of blood cultures with a blood volume inadequate for reliable detection of bacteremia.

Methods: The volumes of blood samples submitted for culture from infants and children up to 18 years of age were measured over a 6-month period. Blood cultures were deemed adequate submissions if they contained an appropriate (age-related) volume of blood and were submitted in the correct blood culture bottle type.