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Utilising clinical parameters to differentiate mycobacteraemia from Mycobacterium tuberculosis v.s. from Mycobacterium avium complex on the day of blood culture signal detection

Abstract number: P1810

Putcharoen O., Udomsantisuk N., Kulwichit W.

Objectives: Disseminated MAC (DMAC) and TB (DMTB) share many clinical features and treatment of these two entities are different. Not all mycobacterial laboratories, especially in developing countries, are equipped to perform rapid, same-day molecular identification of the grown mycobacteria. We sought to identify clinical predictors to aid clinicians in species prediction on the day of positive signals.

Methods: At our hospital, blood cultures for mycobacteria and fungi are incubated in Bactec MYCO/F bottles. Content from positive-signals bottles is stained for acid-fast bacilli (AFB) and subcultured. Specimens with AFB are subjected to commercial, and, when deemed necessary, manual, molecular identification to the species level. We analysed certain clinical parameters that may correlate with disseminated TB (DTB) or MAC (DMAC).

Results: A total of 2,040 blood specimens were sent for mycobacterial and fungal isolation by Bactec MYCO/F medium during Jan 2005-Nov 2007. TB and MAC were isolated in 109 patients. Clinical data were available in 87 of them. The prevalence of mycobacteraemia from MTB is higher. Sensitivity and specificity of AFB smear from Bactec content for mycobacterial identification are 92% and 96% respectively. Smear of content of Bactec MYCO/F medium, which gives positive signals, can accurately predict growth of mycobacterium. Most patients had low CD4 cells (mean 89, median 48). The CD4 in patients with DMAC was significantly lower (p < 0.05). Mycobacteraemia from MAC gave positive signals faster than that from MTB. Patients with DTB tended to have abnormal chest x-ray and higher levels of serum alkaline phosphatase. DMAC had normal chest x-ray or had pulmonary infiltrates clearly attributable to another opportunistic agent.

Demographic, baseline CD4, laboratory findings and time until positive signal of Bactec M/F LYTIC

Conclusion: In our country, with high incidence of TB, prevalence of mycobacteraemia from DMTB in advanced HIV-infected patients is higher than that from DMAC. All patients with CD4 < 60 who had either normal chest x-ray or known lung lesions from other causes, whose blood culture give positive signals faster than 15 days, have DMAC and not DTB. Our data can be used for selection of an appropriate initial treatment regimen in HIV-infected patients with suspected disseminated mycobacterial infection.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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