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

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.

Survival of SSG, an Endophytic Burkholderia Biocontrol Agent, on the Boxwood Leaf Surface

Survival of Burkholderia cepacia complex (Bcc)-based biocontrol agents (BCA) has been associated with their field performance for foliage disease control. SSG, a strain of boxwood endophytic Bcc, suppresses a broad spectrum of plant foliage diseases, including boxwood blight, but the control efficacy declines over time. Factors affecting SSG survival on leaf surfaces were investigated to promote the application of the BCA for boxwood blight management. ‘Justin Brouwers' boxwood plants were treated with SSG cells at 107 to 108 colony-forming unit (CFU)·ml−1, maintained in a moist chamber at 10, 20, or 30 C (50, 68, 86 F), and sampled after the inoculum was blow-dried at 0, 3, 6, 12, and 24 h after treatment. The retained cells per leaf at 0 hours was 105 to 106 CFU, but only less than 10% of the cells survived 24 h after application, irrespective of the wet period and temperature. A wet condition of 12 and 24 h at 20 and 30 C facilitated SSG survival on the second day. Further survival of SSG was affected by temperature but not wetness. Damp conditions and pleasant temperatures can improve bacteria survival and stability and are keys to promoting BCA field applications. Index words: Biocontrol agent, endophyte, survival on plant surfaces, temperature, wetness. Species used in this study: Bacterium strain, SSG (Burkholderia sp);Plant species: Buxus sempervirens L. ‘Justin Brouwers'.

A Polyclonal Antibody Raised against the Burkholderia cenocepacia OmpA-like Protein BCAL2645 Impairs the Bacterium Adhesion and Invasion of Human Epithelial Cells In Vitro

Respiratory infections by bacteria of the Burkholderia cepacia complex (Bcc) remain a life threat to cystic fibrosis (CF) patients, due to the faster lung function decline and the absence of effective eradication strategies. Immunotherapies are regarded as an attractive alternative to control and reduce the damages caused by these infections. In this work, we report the cloning and functional characterization of the OmpA-like BCAL2645 protein, previously identified and found to be immunoreactive against sera from CF patients with a record of Bcc infections. The BCAL2645 protein is shown to play a role in biofilm formation, adherence to mucins and invasion of human lung epithelial cells. The expression of the BCAL2645 protein was found to be increased in culture medium, mimicking the lungs of CF patients and microaerophilic conditions characteristic of the CF lung. Moreover, a polyclonal antibody raised against BCAL2645 was found to inhibit, by about 75 and 85%, the ability of B. cenocepacia K56-2 to bind and invade in vitro CFBE41o- human bronchial epithelial cells. These results highlight the potential of anti-BCAL2645 antibodies for the development of passive immunization therapies to protect CF patients against Bcc infections.

New Auranofin Analogs with Antibacterial Properties against Burkholderia Clinical Isolates

Bacteria of the genus Burkholderia include pathogenic Burkholderia mallei, Burkholderia pseudomallei and the Burkholderia cepacia complex (Bcc). These Gram-negative pathogens have intrinsic drug resistance, which makes treatment of infections difficult. Bcc affects individuals with cystic fibrosis (CF) and the species B. cenocepacia is associated with one of the worst clinical outcomes. Following the repurposing of auranofin as an antibacterial against Gram-positive bacteria, we previously synthetized auranofin analogs with activity against Gram-negatives. In this work, we show that two auranofin analogs, MS-40S and MS-40, have antibiotic activity against Burkholderia clinical isolates. The compounds are bactericidal against B. cenocepacia and kill stationary-phase cells and persisters without selecting for multistep resistance. Caenorhabditis elegans and Galleria mellonella tolerated high concentrations of MS-40S and MS-40, demonstrating that these compounds have low toxicity in these model organisms. In summary, we show that MS-40 and MS-40S have antimicrobial properties that warrant further investigations to determine their therapeutic potential against Burkholderia infections.