A Chlorhexidine- Agar Plate Culture Medium Protocol to Complement Standard Broth Culture of Mycobacterium tuberculosis

Abstract

The culture of Mycobacterium tuberculosis using parallel inoculation of a solid culture medium and a liquid broth provides the gold standard for the diagnosis of tuberculosis. Here, we evaluated a chlorhexidine decontamination-MOD9 solid medium protocol versus the standard NALC-NaOH-Bactec 960 MGIT protocol for the diagnosis of pulmonary tuberculosis by culture. Three-hundred clinical specimens comprising 193 sputa, 30 bronchial aspirates, 10 broncho-alveolar lavages, 47 stools, and 20 urines were prospectively submitted for the routine diagnosis of tuberculosis. The contamination rates were 5/300 (1.7%) using the MOD9 protocol and 17/300 (5.7%) with the Bactec protocol, respectively (P < 0.05, Fisher exact test). Of a total of 50 Mycobacterium isolates (48 M. tuberculosis and two Mycobacterium abscessus) were cultured. Out of these 50, 48 (96%) isolates were found using the MOD9 protocol versus 35 (70%) when using the Bactec protocol (P < 0.05, Fisher exact test). The time to positivity was 10.1 ± 3.9 days versus 14.7 ± 7.3 days, respectively, (P < 0.05, Student’s t-test). These data confirmed the usefulness of parallel inoculation of a solid culture medium with broth for the recovery of M. tuberculosis in agreement with current recommendations. More specifically, chlorhexidine decontamination and inoculation of the MOD9 solid medium could be proposed to complement the standard Bactec 960 MGIT broth protocol.

Stool Culture for Diagnosis of Pulmonary Tuberculosis in Children

“…El Khechine et al replaced NaOH decontamination with 0.25% chlorhexidine in their laboratory handling of stool samples ( 19 , 38 ), citing unpublished data of improved recovery versus contamination compared to NaOH ( 19 ). Chlorhexidine is inactive against mycobacteria and may increase the recovery of M. tuberculosis ( 39 , 40 ). The sensitivity of stool culture in the study by El Khechine is the highest reported for the diagnosis of PTB at 54% ( 19 ).…”

Mycolactone-independent pathogenicity ofMycobacterium ulcerans: an experimental study in plants

“…Samples were then crushed using a piston pellet in 2 mL Eppendorf-tubes containing 1mL of sterile PBS and filtered through a 5μm filter to remove the debris. A 1mL-volume of each homogenate was decontaminated with 1% chlorhexidine and then 100 μL were cultured on MOD9 medium (11).…”

Malaria, tuberculosis and HIV: what's new? Contribution of the Institut Hospitalo-Universitaire Méditerranée Infection in updated data

“…In the search of reducing MTB culture time, which takes more than 2 weeks on conventional media, we set up a step-by-step protocol with a new MOD4 media (blood and egg lecithin) in microaerophilic atmosphere or ascorbic acid supplement and autofluorescent detection, allowing a marked reduction of culture time, with, in some occasion, rifampin susceptibility testing available after 72 hours of growth [90] . On the basis of this knowledge, we developed a novel solid medium for culturing MTB isolates from clinical specimens that we named MOD9, a blood-free derivative of MOD4; we showed that the detection time was significantly shorter compared to conventional Lowenstein medium [97] and standard culture broth [98] .…”