Short report

Improved cultural detection of Burkholderia cepacia from sputum in patients with cystic fibrosis

R M Wright¹, J E Moore¹, A Shaw¹, K Dunbar¹, M Dodd², K Webb², A O B Redmond³, M Crowe¹, P G Murphy¹, S Peacock⁴ and J S Elborn⁵

¹ Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast BT9 7AD, Northern Ireland
² Bradbury Adult Cystic Fibrosis Centre, Wythenshaw Hospital, Manchester M23 9LT, UK
³ Northern Ireland Regional Paediatric Cystic Fibrosis Centre, Royal Belfast Hospital for Sick Children, Belfast BT12 6BE, Northern Ireland
⁴ Department of Bacteriology, John Radcliffe Hospital, Oxford OX3 9DU, UK
⁵ Northern Ireland Regional Adult Cystic Fibrosis Centre, Belfast City Hospital

Correspondence to:
Dr Moore jemoore{at}niphl.dnet.co.uk

Aims—To evaluate the sensitivity and specificity of two selective media for the isolation of Burkholderia cepacia from sputum specimens in patients with cystic fibrosis (CF).

Methods—In total, 149 expectorated sputum specimens from 113 patients with CF (32 cepacia colonised patients and 81 non-cepacia colonised patients) attending three CF centres were examined for the presence of B cepacia on two selective media: (1) MAST selective agar, a commercially available selective medium widely used in the UK and (2) BCSA (B cepacia selective agar), a new medium recently described, which is used predominantly in North America.

Results—Burkholderia cepacia was isolated from 53 of 149 (35.6%) specimens examined, representing 32 of 113 (28.3%) patients, using both the MAST and BCSA media. Growth was most rapid on BCSA with all (53 of 53) isolates detectable after 48 hours, compared with 50 of the 53 isolates on MAST agar, with the remaining three isolates detectable at five days. Twenty eight contaminants were identified on MAST agar and 13 on BCSA agar; mainly Alcaligenes xylosoxidans and yeast on MAST agar and Flavobacterium indologenes on BCSA medium. BCSA was equivalent to MAST agar in its ability to isolate B cepacia from patients with CF with a history of B cepacia infection.

Conclusions—The increased selectivity and reduced time to detection of BCSA makes it an attractive alternative to MAST. However, its present limited commercial availability in the UK may delay its use in routine diagnostic laboratories because of complications with media preparation and quality control.

Key Words: Burkholderia cepacia • Burkholderia cepacia selective agar • MAST agar • cystic fibrosis

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