[An opportunistic pathogen frequently isolated from immunocompromised patients: Burkholderia cepacia complex]

Burkholderia cepacia complex is a group of 17 closely related species. For a long time B.cepacia complex is believed to be only a plant pathogen but later it has emerged as an important opportunistic pathogen causing morbidity and mortality in hospitalized patients. B.cepacia complex particularly causes bacteraemia/sepsis, septic arthritis, osteomyelitis, meningitis, peritonitis, urinary and respiratory tract infections. Patients with cystic fibrosis or chronic granulomatous disease are predisposed to B.cepacia complex infections. B.cepacia complex can survive for a long period of time and can easily multiply in aqueous environments such as disinfectant agents and intravenous fluids used in hospitals. Patients may acquire B.cepacia complex either from the environment or through patient-to-patient transmission. It has always been a tedious task for routine microbiology laboratory to identify B.cepacia complex. In these laboratories, the identification of B.cepacia complex isolates is generally performed using a combination of selective media, conventional biochemical analysis and/or commercial systems. Three media commonly used for isolation of B.cepacia complex are as follows: the Pseudomonas cepacia agar, the oxidation-fermentation based polymyxin bacitracin lactose agar, and more recently the B.cepacia selective agar. Members of the B.cepacia complex can be identified by available commercial tests, such as API 20NE, Phoenix, MicroScan or VITEK. Molecular techniques are useful for confirmation of phenotypic identification and discrimination beyond the species-level. B.cepacia complex is intrinsically resistant to antimicrobial agents such as aminoglycosides, first- and second-generation cephalosporins, antipseudomonal penicillins and polymyxins. B.cepacia complex bacteria often develop resistance to beta-lactams due to presence of inducible chromosomal beta-lactamases and altered penicillin- binding proteins. Antibiotic efflux pumps in B.cepacia complex bacteria mediate resistance to chloramphenicol, trimethoprim and fluoroquinolones. Under antimicrobial pressure, resistance can quickly develop to all susceptible antimicrobials. In this review, the classification and microbiological features of B.cepacia complex, mechanisms of virulence and pathogenesis, epidemiological properties, clinical spectrum, laboratory diagnosis, antimicrobial resistance and treatment, prevention and control measures were summarized.