Detection of Mycobacterium from sputum by using MB BacT/Alert Automated system

Detection of Mycobacterium from sputum by using MB BacT/Alert Automated system การตรวจหาเชื้อวัณโรคด้วยวิธีเพาะเลี้ยงในเครื่องอัตโนมัติ MB BacT/Alert Automated system

Manthana Phengmak, D. of Pathology, F. of Medicine, PSU.
Cherdsak Mahawong, D. of Pathology, F. of Medicine, PSU.
Urairat Kongmuang, D. of Pathology, F. of Medicine, PSU.
Corresponding e-mail : kurairat@ratree.psu.ac.th

Presented : The 16th Annual Academic Meeting, Faculty of Medicine, PSU., Hat Yai, Songkhla, 10-18 August 2000
Key words : Mycobacterium, MB BacT/Alert automated system, Tuberculosis, sputum culture

The MB BacT/Alert automated system for detection of Mycobacterium has been set in Microbiology Laboratory at Songklanagarind Hospital recently. Prior to service the samples by automate, the method was compared with the routine swab method. A number of 100 sputum samples obtained from suspicious mycobacterial infected patients were cultured by both methods. The routine swab method was performed by swabing the sputum, dipping in oxalic acid and sodium citrate, then culturing on Lowenstein Jensen media and incubating at 37^oC for 2 months. Automated method: The sputum were decontaminated with NaOH and neutralized with PBS, then cultured by MB BacT/Alert automated system for 45 days.

There were 11 positive cultures detected by the routine swab method and 33 positive cultures by automated method. The mean time for the detection of the growth was 30 days by routine swab method and 15 days by automated method. One hundred and forty sputum samples were continue cultured with automated method. The positive culture for mycobacteria was 50 samples (36%), included 29 M. tuberculosis and 21 nontuberculous mycobacteria (NTM). Mostly, the positive culture could be detected at a period of 8-14 days.

MB BacT/Alert is faster and three times more sensitive than the routine swab method in the detection of Mycobacterium. The problem for the detection of Mycobacterium by automate is the contamination of other microorganisms from saliva. Therefore, samples from patients should be true sputum.

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