Accuracy of four commercial systems for identification of Burkholderia cepacia and other gram-negative nonfermenting bacilli recovered from patients with cystic fibrosis

Abstract

Burkholderia cepacia has recently been recognized as an important pathogen in chronic lung disease in patients with cystic fibrosis (CF). Because of the social, psychological, and medical implications of the isolation of B. cepacia from CF patients, accurate identification of this organism is essential. We compared the accuracies of four commercial systems developed for the identification of nonfermenting, gram-negative bacilli with that of conventional biochemical testing for 150 nonfermenters including 58 isolates of B. cepacia recovered from respiratory secretions from CF patients. The accuracies of the four systems for identifying all nonfermenters ranged from 57 to 80%, with the RapID NF Plus system being most accurate. The accuracies of these systems for identifying B. cepacia ranged from 43 to 86%, with the Remel system being most accurate. Depending on the commercial system, from two to seven isolates were misidentified as B. cepacia. The relatively poor performance of the commercial systems requires that identification of certain nonfermenters be confirmed by conventional biochemical testing. These organisms include B. cepacia, Burkholderia sp. other than B. cepacia, and infrequently encountered environmental species (Pseudomonas and Flavobacterium species). In addition, conventional biochemical testing should be done if a commercial system fails to assign an identification to an organism. Confirmatory testing should preferably be performed by a reference laboratory with experience in working with organisms isolated from CF patients.

The Changing Microbial Epidemiology in Cystic Fibrosis

“…Recommendations for and adherence to protocols for processing of CF respiratory specimens (e.g., the use of selective media for Burkholderia and, more recently, for staphylococci) have varied considerably during the past decade (281,361). High rates of misidentification of several CF-relevant species by commer-cially available microbial identification systems have been well described (29,66,158,201,265,280,291,292,334). In some surveys, for example, more than 1 in 10 isolates referred to reference laboratories initially identified as B. cepacia complex or A. xylosoxidans isolates had been misidentified (201,265).…”

Infections in Patients with Cystic Fibrosis

“…These organisms were often phenotypically difficult to separate from B cepacia using commercially available kits, resulting in Infections in Patients with Cystic Fibrosis misidentification of non-B cepacia isolates as B cepacia complex ones. 58,59 Alternatively, some isolates were relatively inert biochemically, making them difficult to identify using commercially available phenotypic methods. 58,59 Misidentification of non-B cepacia organisms as B cepacia has grim consequences for the patient with CF.…”

“…58,59 Alternatively, some isolates were relatively inert biochemically, making them difficult to identify using commercially available phenotypic methods. 58,59 Misidentification of non-B cepacia organisms as B cepacia has grim consequences for the patient with CF. In addition to no longer being candidates for lung transplantation in most centers, the patients are completely segregated from other children and adults with CF.…”

Detection and accurate identification of new or emerging bacteria in cystic fibrosis patients

“…Although conventional phenotypic tests fail to produce accurate results [32,33], molecular methods such as PCR followed by sequencing ( Fig. 1) offer an established, powerful and reliable option for the correct identification of bacteria (Table 1), especially nonfermenting Gram-negative bacilli [13,36,[48][49][50][51][52][53][54][55][56].…”