BURKHOLDERIA (PSEUDOMONAS) CEPACIA AND CYSTIC-FIBROSIS - THE EPIDEMIOLOGY IN BELGIUM

Burkholderia cepacia has become an increasingly recognized pathogen am ong cystic fibrosis (CF) patients and its potential role in declining pulmonary function or unexpected fatal outcome has caused widespread c oncern. Direct person-to-person transmission has been documented and a segregation policy of CF patients colonized with B.cepacia from non-c olonized CF patients is widely adopted. Since this policy has a dramat ic impact on social behaviour of CF patients it is imperative that cli nical laboratories accurately isolate and identify B.cepacia in the re spiratory secretions. In order to comprehend the epidemiology of B.cep acia in the Belgian CF population a multicentre study was conducted du ring a period of 1 year (March'93-February'94). B.cepacia was isolated in only 12 of 465 CF patients (2.6%). Routine biochemical tests ident ified these strains as authentic B.cepacia. However, the combined data from protein and DNA-DNA hybridization analyses revealed that the Bel gian CF ''B.cepacia'' isolates showed patterns different from referenc e B.cepacia isolates and belong to 3 different, newly identified Burkh olderia genomovars, but not to B.cepacia. Comparative analysis of the selective media used for recovery of these ''B.cepacia'' strains from respiratory secretions indicated that the commercial medium (Mast) con taining polymyxin B and ticarcillin as the selective agents was the be st and most user-friendly. Molecular typing of these Burkholderia isol ates by arbitrarily-primed PCR (AP-PCR) and pulsed-field gel electroph oresis (PFGE) showed that spread of a single strain within a same cent re occurred but the mode of transmission remains unknown; inter-centre spread of strains was not observed. Interestingly, neither colonizati on with a distinct or an epidemic strain (belonging to either of the t hree newly identified Burkholderia genomovars) nor colonization for a prolonged period of time, led to a rapid deterioration of lung functio n in these CF patients. It appears essential to determine the prevalen ce of these ''new'' Burkholderia genomovars in larger populations of C F patients and to evaluate their virulence and other features as this may have important clinical and practical implications.