Skip to main content

DST : Drug Susceptibility Testing for Tuberculosis; HOW & WHY?

Introduction: 

DST is used to detect resistance of Drugs used in Tuberculosis. So through this test we try to find out which drug is sensitive to TB Bacteria.

Pre-test Requirement: 

For DST positive cultured sample is required.

Culture Medium:

Mainly two medium is used to perform DST testing:

  1. MGIT(Liquid Culture): Fast Method(15-28 Days) 

Mycobacteria Growth Indicator Tube (MGIT) is intended for the detection and recovery of mycobacteria. The MGIT Mycobacteria Growth Indicator Tube contains 4 mL of modified Middlebrook 7H9 Broth base. The machine used for this purpose is of two main types:
  • MGIT 960: 

MGIT 960
This instrument is produced by Becton Dickinson (BD). The BD BACTEC MGIT 960 system is for high-volume mycobacteria growth, detection and susceptibility testing and is designed to meet the needs of medium- and high-volume laboratories.
 It is specially designed to accommodate Mycobacteria Growth Indicator Tube (MGIT) and incubate them at 37°C. The instrument scans the MGIT every 60 minutes for increased fluorescence. Analysis of the fluorescence is used to determine if the tube is instrument positive means test sample contain viable organism
  • MGIT 320:

 The BD BACTEC MGIT 320 system is designed to help smaller-capacity laboratories quickly and accurately detect TB.
    MGIT 320
 
 
 
 
 
 
 
 
 
 
 
 
 
 

2. LJ Culture(Solid Culture): Slow Method(6-8 Weeks)


Drugs Availabale for DST:

These Drugs are available on  MGIT(Liquid Culture)
  1.  Clofazimine
  2. Moxifloxacin
  3. Linezolide
  4. Rifbutin
  5. Levofloxacin
  6. PAS
  7. Ethionamide
  8. Ofloxacin
  9. Ciprofloxacin
  10. Kanamycin
  11. Campreomycin
  12. Amikacin
  13. Streptomycin
  14. Pyrazynamide
  15. Ethambutol
  16. Rifampicin
  17. Isoniazid
Other than these drugs are available on LJ Culture

Why DST is used?

It helps to diffenciate between primary and acquired drug resistance and confirm choice of the initial course of therapy.
Detection of Drug resistance using liquid culture system can be accomplished in 15-28 days rather than 6-8 weeks by conventional LJ culture.
This method is Extremely useful to test drugs not yet available on genotypic platforms.

Basically DST is used to detect MDR TB or XDR TB:

A) Multidrug-resistant Mycobacterium tuberculosis (MDR-TB):

The WHO estimates that 5% of all TB cases worldwide harbor a multidrug-resistant Mycobacterium tuberculosis (MDR-TB) strain.

Definition: MDR-TB is defined as resistance against, at least, rifampicin (RMP) and isoniazid (INH). In 2007, approximately 511,000 new MDR-TB cases were reported

B) Extensively drug-resistant TB (XDR-TB):

In the latest report on anti-TB drug resistance worldwide, conducted by the WHO and the International Union Against Tuberculosis and Lung Disease (IUATLD), high rates of resistance have been shown, with values reaching more than 20% of MDR cases among new cases in certain regions. Extensively drug-resistant TB (XDR-TB) cases have been detected in at least 55 countries.

Definition: XDR-TB is defined as MDR-TB plus resistance to any fluoroquinolone, and to at least one out of three injectable second-line anti-TB drugs (capreomycin, kanamicin and amikacin)

FAQ:

Q1. What is sample required for this test?
Answer: Positive sample of already cultured specimen. It may be sputum, tissues or tissue fluids like CSF, Peritoneal fluid etc

Q2. Is any other fast method available to know Drug resistance?
Answer: Yes. Genotypic platform is also available. It is also called LPA(Line Probe Assay) or Hains Test. But Genotypic platform is only available for Rifamapicin, Isoniazid, fluroquinolones, aminoglycosides, Cyclic peptides, Ethambutol.

Refrences:
1. “Molecular Line-Probe Assay for the Detection of Resistance to Second Line Anti-TB Drugs”, WHO, www.who.int/tb/areas-of-work/laboratory/policy_statements
2. https://www.tbfacts.org/drug-susceptibility/
3.http://www.bd.com/en-us/offerings/capabilities/microbiology-solutions/mycobacteria-testing/bd-bactec-mgit-automated-mycobacterial-detection-system
4. https://www.youtube.com/watch?v=RwifN15FrOc
5. Siddiqi, Salman H.; Sabine Rüsch-Gerdes (2006). Procedure Manual For BACTEC MGIT 960 TB System.
6. Siddiqi, Salman H.; Sabine Rüsch-Gerdes (2006). Procedure Manual For BACTEC MGIT 960 TB System.
7. "Use of BACTEC MGIT 960 for Recovery of Mycobacteria from Clinical Specimens: Multicenter Study" Enrico Tortoli, Paola Cichero, Claudio Piersimoni, M. Tullia Simonetti, Giampietro Gesu, and Domenico Nista Journal of Clinical Microbiology, November 1999, p. 3578-3582, Vol. 37, No. 11 [1]
8. "Evaluation of Automated BACTEC MGIT 960 System for Testing Susceptibility of Mycobacterium tuberculosis to Four Major Antituberculous Drugs: Comparison with the Radiometric BACTEC 460TB Method and the Agar Plate Method of Proportion" Enrico Tortoli, Marta Benedetti, Alessandra Fontanelli, and M. Tullia Simonetti Journal of Clinical Microbiology, February 2002, p. 607-610, Vol. 40, No. 2 doi:10.1128/JCM.40.2.607-610.2002
8. "Evaluation of the fully automated Bactec MGIT 960 system for the susceptibility testing of Mycobacterium tuberculosis to first-line drugs: a multicenter study" Fanourios Kontosa, Maria Maniatia, Christos Costopoulosb, Zoe Gittic, Stavroula Nicolaoub, Efymia Petinakia, Spyridoula Anagnostoub, Ioannis Tselentisc and Antonios N. Maniatis Journal of Microbiological Methods Volume 56, Issue 2, February 2004, Pages 291–294 doi:10.1016/j.mimet.2003.10.015







Comments

Popular posts from this blog

Chhap Tilak Sab Chhini Re Song | Lyrics in Hindi with Meaning in English

Introduction:  Basically this is poem written by Amir Khusro in 14th Century.  छाप तिलक सब छीनी रे मोसे नैना मिलाइके You've taken away my looks, my identity, by just a glance. बात अगम कर दिनी रे तो से नैना मिलाई के You've said the unknown, by just a glance. प्रेम भटी का मदवा पिलाइके By making me drink the wine from the love of devotion मतवारी कर लीन्ही रे मोसे नैना मिलाइके You've intoxicated me by just a glance; गोरी गोरी बईयाँ, हरी हरी चूड़ियाँ My fair, delicate wrists with green bangles in them बईयाँ पकड़ धर लीन्ही रे मोसे नैना मिलाइके Have been taken off by you with just a glance. बल बल जाऊं मैं तोरे रंग रजवा I give my life to you, Oh my cloth-dyer, अपनी सी रंग दीन्ही रे मोसे नैना मिलाइके You've dyed me like yourself, by just a glance. खुसरो निजाम के बल बल जाए I give my whole life to you Oh, Nizam, मोहे सुहागन कीन्ही रे मोसे नैना मिलाइके You've made me your bride, by just a glance. छाप तिलक सब छीनी रे मोसे नैना मिलाइके You've taken

Dil Hoom Hoom Kare Song | Lyrics in Hindi with Meaning in English

Introduction: Basically this song lyrics written by Gulzar; all music composed by Bhupen Hazarika. Gulzar दिल हूम हूम करे, घबराए Dil hoom hoom kare, ghabraaye (The heart rumbles and mumbles) घन धम धम करे, गरजाए Ghan dham dham kare, darr jaaye (dark clouds of worries roar and thunder) एक बूँद कभी पानी की, मोरे अँखियों से बरसाए Ek boond kabhi paani ki mori ankhiyon se barsaaye (and yet I keep yearning, for even a single drop of tears to burst forth from my eyes) तेरी झोली डारूँ, सब सूखी पात जो आए Teri jhori daaroon sab sukhe paat jo aaye (I know your touch can sprout life in these shrivelled stumps of my existence) तेरा छुआ लगे, मेरी सूखी डाल हरियाए Tera chhua laage, meri sukhi daar hariyaaye (and in this hope I gather and preserve all the wilted leaves of my life) Statue of Bhupen Hazarika दिल हूम हूम करे, घबराए Dil hoom hoom kare, ghabraaye (The heart rumbles and mumbles) जिस तन को छूआ तूने उस तन को छुपाऊँ Jis tan ko chhua tune, us tan ko chhupaa

Na Daro Har So Jab Jaye Lado Song | Lyrics in Hindi with Meaning in English

Introduction: Original name of this song is Deh Shiva Bar Mohe. Originally this is 17th-century hymn( भजन)  written by Guru Govind Singh(10th Sikh Guru) in the Dasam Granth in Brij Bhasha language. न डरौं अरि सौं जब जाय लड़ौं, निश्चय कर अपनी जीत करौं, May I battle all foes ( दुश्मनों)  without fear, and claim victory with courage, न डरौं अरि सौं जब जाय लड़ौं, निश्चय कर अपनी जीत करौं, May I battle all foes without fear, and claim victory with courage, निश्चय कर अपनी जीत करौं, Claim victory with courage, देह शिवा बर मोहे ईहे, शुभ कर्मन ते कभुं न टरूं, Grant me this boon( वरदान) , O God | May I never refrain from righteous acts, देह शिवा बर मोहे ईहे, शुभ कर्मन ते कभुं न टरूं, Grant me this boon( वरदान) , O God | May I never refrain from righteous acts, अरु सिख हों आपने ही मन कौ इह लालच हउ गुन तउ उचरों, May the glory be etched on my mind, And my highest goal be singing the praise, जब आव की अउध निदान बनै अति ही रन मै तब जूझ मरों, When this moral life comes to an e