Evaluation of the Kudoh method for mycobacterial culture: Gambia experience

AbstractObjective/backgroundTo evaluate the Kudoh swab method for improving laboratory diagnosis of tuberculosis (TB) in Gambia.MethodsA total of 75 sputa (50 smear positive and 25 smear negative) were examined. Sputum samples were collected from leftover routine samples from the Medical Research Council Unit, Gambia TB Diagnostic Laboratory. The samples were processed using the standard N-acetyl-l-cysteine-NaOH (NALC-NaOH) methods currently used and Kudoh swab method. These were cultured on standard Lowenstein Jensen (LJ) and Modified Ogawa media, respectively, and incubated aerobically at 36±1°C for mycobacterial growth. To determine if the decontamination and culture methods compared could equally detect the Mycobacterium tuberculosis complex (MTBC) highly commonly isolated in Gambia, spoligotyping was done.ResultsIn total, 72% (54/75) of MTBC were recovered by both LJ and Modified Ogawa methods. The LJ method recovered 52% (39/75) and Modified Ogawa recovered 56% (42/75) of the MTBC, respectively. Spoligotyping showed Euro-American 35% (19/54), Indo-Oceanic 35% (19/54), Mycobacterium africanum (West African type 2) 26% (14/54), Beijing 2% (1/54), and M. africanum (West African type 1) 2% (1/54).ConclusionThe Kudoh method is simpler and cheaper than the NALC-NaOH method. There was no significant difference in recovery between the methods. The Kudoh method is ideal in overburdened TB laboratories with poor resources in developing countries. The predominant lineages were Euro-American and Indo-Oceanic, followed by M. africanum (West African type 2)

Evaluation of sodium hydroxide–N-acetyl-l-cysteine and 0.7% chlorhexidine decontamination methods for recovering Mycobacterium tuberculosis from sputum samples: A comparative analysis (The Gambia Experience)

Objective/Background: To determine the culture yield and time to detection of mycobacterial growth between samples decontaminated using 0.7% chlorhexidine and sodium hydroxide–N-acetyl-l-cysteine (NaOH–NALC) and cultured on the Löwenstein–Jensen (LJ) medium. We also aimed to determine the contamination rate between the 0.7% chlorhexidine and NaOH–NALC decontamination methods. Methods: The study was carried out on 68 sputa samples (42 smear positives and 26 smear negatives). Of these 68 samples, 46 were collected from men and 26 from women with an approximate average age of 27 years. All the sputum samples were decontaminated using the standard NaOH–NALC and 0.7% chlorhexidine methods. The concentrates were cultured in parallel on LJ media in which reading of the slope for mycobacterial growth was obtained daily for the first 2 weeks and then weekly until week 8. The mycobacterial recovery rate, time to detection, and contamination rate were then compared. Results: The overall recovery rate of mycobacterial growth on samples treated with both decontamination methods inoculated on LJ media is 51.5% (35/68). Specifically, mycobacterial growth rates on samples treated with 0.7% chlorhexidine and standard NaOH–NALC on LJ media were 61.8% (42/68) and 54.4% (37/68), respectively. However, the growth of Mycobacterium tuberculosis complex was faster on samples treated with 0.7% chlorhexidine than those treated with NaOH–NALC (average, 32 ± 5 days vs. 33 ± 5.2 days, respectively). The contamination rate on samples treated with 0.7% chlorhexidine was 1.5% (1/68), whereas on those treated with NaOH–NALC, the rate was 4.4% (3/68). Conclusion: The 0.7% chlorhexidine decontamination method is rapid and has less contamination rate in terms of mycobacterial recovery compared with the standard NaOH–NALC method. Therefore, the 0.7% chlorhexidine decontamination method would be an ideal alternative option for decontamination of sputum samples and recovery/isolation of M. tuberculosis in resource-poor countries