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Year : 2020  |  Volume : 9  |  Issue : 2  |  Page : 229-230

Kudoh swab method for Mycobacterium tuberculosis culture: Looking back to the 70s to fight tuberculosis

One Health Research Group, Universidad de Las Américas, Quito, Ecuador

Date of Web Publication29-May-2020

Correspondence Address:
Miguel Angel Garcia-Bereguiain
One Health Research Group, Universidad de Las Americas, Quito
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmy.ijmy_66_20

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How to cite this article:
Garcia-Bereguiain MA. Kudoh swab method for Mycobacterium tuberculosis culture: Looking back to the 70s to fight tuberculosis. Int J Mycobacteriol 2020;9:229-30

How to cite this URL:
Garcia-Bereguiain MA. Kudoh swab method for Mycobacterium tuberculosis culture: Looking back to the 70s to fight tuberculosis. Int J Mycobacteriol [serial online] 2020 [cited 2020 Jul 9];9:229-30. Available from: http://www.ijmyco.org/text.asp?2020/9/2/229/285237

Dear Editor,

The culture of Mycobacterium tuberculosis (MTB) is still the gold standard for tuberculosis (TB) diagnosis. To improve TB control and prevention strategies, the WHO recommends to increase MTB culture, particularly at high-burden settings. The culture of MTB from clinical samples requires the elimination of the associated flora in a decontamination step. Petroff method is used as the gold standard decontamination protocol worldwide, although includes a time-consuming centrifugation step and requires technically skilled personnel. There is also a need for a biological safety lab due to the aerosols potentially generated. For these reasons, MTB culture is not widespread enough in developing countries, especially in rural areas with lack of facilities, where TB prevalence is actually higher.

More than 40 years ago in Japan, Kudoh and Kudoh[1] described an easy swab method for the decontamination step that takes only 3–4 min per sample and does not need neither technical skills nor lab equipment: a cotton swab is immersed on the sample and decontaminated for 2 min in a solution of 4% sodium hydroxide, and then directly smeared in the culture medium. There are only few small-scale studies in the literature that have evaluated the Kudoh swab method performance compared to Petroff method, all of them concluding than Kudoh swab method is a cheap, fast, simple, and reliable option for MTB culture. However, the WHO only recommends Petroff method in its laboratory guides. The Pan-American Health Organization mentions the Kudoh swab method in its manual for TB culture, but only for laboratories that lack the adequate equipment and warning for high contamination.

The aim of this letter is to spread the findings recently reported on a publication from my laboratory on Ecuador[2] among the scientific community within the Asian African Society of Mycobacteriology.[3] We carried out the most extensive study to date for validation of Kudoh swab method for culturing MTB. Almost 3000 samples were included in the study, both pulmonary and for the first time extrapulmonary, and processed for both Petroff and Kudoh decontamination methods prior to culture. Kudoh swab method outperforms gold standard Petroff method showing a better MTB diagnostic yield. Contamination rate was the same for both methods. But also and more importantly, we found and striking difference for MTB colonies grow timing with more then 40% of total positive cultures obtained after two weeks with Kudoh swab method, while culture grow was observed with Petroff method after 4 weeks. Hence, compared to Petroff method, the Kudoh swab method is cheaper and faster in terms of sample processing and diagnosis (culture grows at one to 2 weeks earlier) and totally reliable (some contamination rate and slightly higher MTB detection rate).

We hope that upon our study publication other TB laboratories along the world may perform similar validation studies to support a switch toward Kudoh swab method in the WHO recommendations for MTB culture. That will help increase MTB culture on high-burden rural areas on developing countries or even speed diagnosis on high-workload TB laboratories at urban high-burden settings.

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Conflicts of interest

There are no conflict of interest.

  References Top

Kudoh S, Kudoh T. A Simple Technique for Culturing Tubercle Bacilli. Vol. 51. Switzerland: Bulletin World Health Organization; 1974. p. 71-82.  Back to cited text no. 1
Franco-Sotomayor G, Rivera-Olivero IA, Leon-Benitez M, Uruchima-Campoverde SE, Cardenas-Franco G, Perdomo-Castro ME, et al. Fast, simple, and cheap: The Kudoh-Ogawa swab method as an alternative to the Petroff-Lowenstein-Jensen method for culturing of Mycobacterium tuberculosis. J Clin Microbiol 2020;58. pii: e01424-19.  Back to cited text no. 2
Manual Para el Diagnóstico Bacteriológico de la Tuberculosis. Parte II Cultivo. Organizacion Panamaericana de Salud; 2008. Available from: http://iris.paho.org/xmlui/handle/123456789/18616. [Last accessed on 2020 Mar 30].  Back to cited text no. 3


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