Cost-Effectiveness of Blood Agar for Isolation of Mycobacteria

Abstract

Background Mycobacterium species are grown using specific media that increase laboratory cost, thus hampering their diffusion in resource-limited countries. Preliminary data suggested that versatile blood agar may be also used for mycobacterial culture.MethodologyWe examined the growth of 41 different Mycobacterium species on 5% blood agar. Over a 24-month period we analysed isolation of mycobacteria after parallel inoculation of clinical specimens into both a reference automated system (BACTEC 9000 MB broth) and 5% blood agar slant tubes, after NaOH decontamination, and compared the cost of performing 1,000 analyses using these two techniques.Conclusions Mycobacterium reference species cultured on blood agar, with the exception of Mycobacterium ulcerans. Inoculation of 1,634 specimens yielded 95 Mycobacterium isolates. Blood agar performed significantly more efficiently than BACTEC 9000 MB broth (94 vs 88 isolates, P = 0.03). Decontamination of Candida albicans in 5 specimens by addition of amphotericin B in blood agar yielded one more M. tuberculosis isolate that could not be isolated in BACTEC broth. Uneven distribution of time to culture positivity for M. tuberculosis had a median (range) of 19±5 days using blood agar and 26±6 days using BACTEC 9000 MB broth. Cost for 1,000 analyses in France was estimated to be of 1,913 euros using the blood agar method and 8,990 euros using the BACTEC 9000 MB method. Blood agar should be regarded as a first-line medium for culturing Mycobacterium species. It saves time, is cost-effective, is more sensitive than, and at least as rapid as the automated method. This is of particular importance for resource-limited countries in which the prevalence of tuberculosis is high.

Comparison of the isolation and inhibition abilities ofselective media used for Brucella spp. Isolation

“…Amphotericin-B is regarded as one of the antifungal agents recommended to be added into selective media for the first isolation of Mycobacterium spp., (19), Campylobacter spp. (20), and Brucella spp.…”

Bacterial Lymphadenitis at a Major Referral Hospital in France from 2008 to 2012

“…The isolates were identified using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) as previously described (16). For the isolation of mycobacteria, the samples were cultured in MGIT tubes (Becton, Dickinson, Pont-De-Claix, France) or on a homemade 5% sheep blood agar (bioMérieux, La Balme-les-Grottes, France) for 2 to 45 days at 32°C or 37°C, as previously described (17). Gram staining was used to ensure the absence of any contaminant organisms in the culture, and standard identification of mycobacteria was performed using MALDI-TOF, as previously described (18).…”

Comparative Study for Determination of Mycobacterium tuberculosis Susceptibility to First- and Second-Line Antituberculosis Drugs by the Etest Using 7H11, Blood, and Chocolate Agar

“…It has been reported recently that M. tuberculosis can be easily grown on blood agar and chocolate agar (10,11). Moreover, other studies (6)(7)(8)31) have noted that blood agar may be suitable for susceptibility testing of M. tuberculosis.…”

“…The current recommended Etest procedure for M. tuberculosis is based on Middlebrook 7H11 agar supplemented with oleic acid, albumin, dextrose, and catalase (OADC) (1). In recent years, it has been reported that M. tuberculosis isolates could be grown on blood agar in 1 to 2 weeks (4,10,11,16). In addition, the results of our previous reports have shown that blood agar can be used as an alternative medium for testing M. tuberculosis with isoniazid (IZ), rifampin (RI), streptomycin (SM), and ethambutol (EB) (6-8, 31).…”

“…However, blood agar is routinely used. However, Drancourt et al (11) reported that blood agar saves time, is cost-effective, and is at least as rapid as the automated systems.…”