BURKHOLDERIA CEPACIA - MEDICAL, TAXONOMIC AND ECOLOGICAL ISSUES

The increasing challenge posed by multiresistant saprophytes in medica l microbiology is strikingly demonstrated by the emergence of Burkhold eria (formerly Pseudomonas) cepacia as an opportunist pathogen in immu nocompromised patients, particularly individuals with chronic granulom atous disease and cystic fibrosis (CF). Best known previously as a phy topathogen and the cause of soft rot of onions, B. cepacia presents th ree major problems for the CF community: innate multiresistance to ant imicrobial agents; person-to-person transmission of epidemic strains t hrough nosocomial or social contacts; and 'cepacia syndrome', a fulmin ating fatal pneumonia, sometimes associated with septicaemia, that occ urs in approximately 20% of colonised patients, including those with p reviously mild disease. Accumulated evidence to dispel earlier suggest ions that the organism is avirulent and merely a marker of existing lu ng disease includes: case-controlled studies in CF patients; reports o f serious infections in non-CF patients; in-vitro and in-vivo evidence that B. cepacia induces production of pro-inflammatory markers, inclu ding the major cytokine TNF alpha; and histopathological evidence that exposure of transgenic CF mice to B. cepacia results in pneumonia. By the early 1990s, the use of selective culture media and DNA-based bac terial fingerprinting confirmed suspicions of epidemic person-to-perso n spread of B. cepacia. This evidence provided scientific justificatio n for draconian and controversial measures for infection control, in p articular, segregation of B. cepacia-colonised patients during treatme nt at CF centres and their exclusion from social gatherings and nation al conferences. Recently, molecular analyses of type strains and clini cal isolates have revealed that isolates identified previously as B. c epacia belong to at least three distinct species and have increased co ncern regarding the reliability of current laboratory detection and id entification systems. Clarification of the taxonomy of B. cepacia-like organisms and the pathogenic potential of environmental isolates rema ins a high priority, particularly when the organism's antifungal and d egradative properties have created interest in its potential use as a biological control agent to improve crop yields and its use for the bi oremediation of contaminated soils.