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Biomicrofluidics. 2015 Aug 20;9(4):044120. doi: 10.1063/1.4928879. eCollection 2015 Jul.

Quantitative detection of cells expressing BlaC using droplet-based microfluidics for use in the diagnosis of tuberculosis.

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Department of Mechanical Engineering, Stanford University , Stanford, California 94305, USA.
Molecular Imaging Program at Stanford, Departments of Radiology and Chemistry, Stanford University , Stanford, California 94305, USA.


This paper describes a method for the quantitative detection of cells expressing BlaC, a β-lactamase naturally expressed by Mycobacterium tuberculosis, intended for the diagnosis of tuberculosis. The method is based on the compartmentalization of bacteria in picoliter droplets at limiting dilutions such that each drop contains one or no cells. The co-encapsulation of a fluorogenic substrate probe for BlaC allows the quantification of bacteria by enumerating the number of fluorescent drops. Quantification of 10 colony forming units per milliliter is demonstrated. Furthermore, the encapsulation of single cell in drops maintains the specificity of the detection scheme even when the concentration of bacteria that do not express BlaC exceeds that expressing BlaC by one million-fold.

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