Evaluation of Three Culture Media for Isolation of Burkholderia cepacia Complex from Respiratory Samples of Patients with Cystic Fibrosis.

Emma C L Marrs,John D Perry,Audrey Perry

doi:10.3390/microorganisms9122604

Abstract

Burkholderia cepacia complex (BCC) is a significant pathogen causing respiratory disease in individuals with cystic fibrosis (CF). Diagnosis is typically achieved by isolation of BCC on selective culture media following culture of sputum or other respiratory samples. The aim of this study was to compare the efficacy of three commercially available selective media for the isolation of BCC. The three media comprised Burkholderia cepacia selective agar (BCSA; bioMérieux), BD Cepacia medium (BD: Becton–Dickinson) and MAST Cepacia medium (MAST laboratories). Each medium was challenged with 270 respiratory samples from individuals with CF as well as an international collection of BCC (n = 26) and 14 other isolates of Burkholderia species at a range of inocula. The international collection was also used to artificially “spike” 26 respiratory samples. From a total of 34 respiratory samples containing BCC, 97% were recovered on BD and 94% were detected on MAST and BCSA. All three media were effective for isolation of BCC. BCSA was much more selective than the other two media (p < 0.0001) meaning that fewer isolates required processing to exclude the presence of BCC.

Highlights

Individuals with cystic fibrosis (CF) are susceptible to respiratory infections caused by non-fermentative Gram-negative bacteria
Using a high inoculum of approx. 60,000 colony-forming units (CFU)/spot, all isolates were recovered on the three selective media except for B. ambifaria (LMG 19467) which was inhibited by Burkholderia cepacia selective agar (BCSA)
Described the development of BCSA that utilised polymyxin, gentamicin and vancomycin as selective agents along with lactose, sucrose and phenol red to help differentiate Burkholderia cepacia complex (BCC). These formulations form the basis of the selective media that are currently commercially available for isolation of BCC, with MAST medium and BD medium utilising the selective agents used in PC medium and bioMérieux utilising a formulation based on BCSA [18]

Summary

Introduction

Individuals with cystic fibrosis (CF) are susceptible to respiratory infections caused by non-fermentative Gram-negative bacteria Among such bacteria, Burkholderia cepacia complex (BCC) has the most deleterious impact in terms of morbidity and mortality. Qvist et al examined the impact of a range of pathogens on the lung function of 432 patients with CF in a longitudinal registry study spanning 40 years [1]. They showed that, among Gram-negative pathogens, BCC had the greatest negative impact on lung function and was second only to Mycobacterium abscessus complex in terms of severity. This decline is due to improved infection control measures to reduce patient-to-patient transmission of BCC, including the segregation and cohorting of infected individuals within clinics [9]

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