Andrew McDowell

Burkholderia cepacia complex genomovars and pulmonary transplantation outcomes in patients with cystic fibrosis

Burkholderia cepacia is a group of organisms that comprises seven genotypically distinct species (B cepacia genomovars I-VII), which are collectively known as the B cepacia complex. Preoperative infection with B cepacia is associated with a poor prognosis in lung transplant recipients with cystic fibrosis. Many centres do not, therefore, offer transplants to these individuals. Our aim was to ascertain whether or not post-transplant mortality is affected by pretransplant genomovar status. We studied archived isolates with PCR-based methods, and recorded excessive mortality in patients infected with B cepacia genomovar III, but not in those infected with other genomovars.

PCR-Based Detection and Identification of Burkholderia cepacia Complex Pathogens in Sputum from Cystic Fibrosis Patients

ABSTRACT PCR amplification of the recA gene followed by restriction fragment length polymorphism (RFLP) analysis was investigated for the rapid detection and identification ofBurkholderiacepacia complex genomovars directly from sputum. Successful amplification of the B.cepacia complex recA gene from cystic fibrosis (CF) patient sputum samples containing B.cepacia genomovar I, Burkholderiamultivorans, B. cepaciagenomovar III, Burkholderiastabilis, andBurkholderiavietnamiensis was demonstrated. In addition, the genomovar identifications determined directly from sputum were the same as those obtained after selective culturing. Sensitivity experiments revealed thatrecA-based PCR could reliably detect B.cepacia complex organisms to concentrations of 106 CFU g of sputum−1. To fully assess the diagnostic value of the method, sputum samples from 100 CF patients were screened for B. cepacia complex infection by selective culturing and recA-based PCR. Selective culturing identified 19 samples with presumptiveB. cepacia complex infection, which was corroborated by phenotypic analyses. Of the culture-positive sputum samples, 17 were also detected directly by recA-based PCR, while 2 samples were negative. The isolates cultured from bothrecA-negative sputum samples were subsequently identified as Burkholderiagladioli. RFLP analysis of the recA amplicons revealed 2 patients (12%) infected with B. multivorans, 11 patients (65%) infected with B. cepaciagenomovar III-A, and 4 patients (23%) infected with B.cepacia genomovar III-B. These results demonstrate the potential of recA-based PCR-RFLP analysis for the rapid detection and identification of B.cepacia complex genomovars directly from sputum. Where the sensitivity of the assay proves a limitation, sputum samples can be analyzed by selective culturing followed by recA-based analysis of the isolate.

Inflammatory markers in cystic fibrosis patients with transmissible Pseudomonas aeruginosa

Chronic Pseudomonas aeruginosa infection in cystic fibrosis (CF) leads to a damaging host inflammatory response. There are an increasing number of reports of P. aeruginosa cross-infection at CF centres. The clinical significance of acquisition of a transmissible strain for patients who already harbour P. aeruginosa is unclear. In this study, levels of inflammatory markers in clinically stable adult CF patients who harbour transmissible and sporadic strains of P. aeruginosa have been compared. Patients with CF and chronic P. aeruginosa infection were grouped into those who harbour a transmissible P. aeruginosa and those who harbour their own sporadic strains. Total white cell and differential counts, sputum neutrophil elastase (NE), interleukin (IL)‐8, tumour necrosis factor (TNF)‐α, plasma IL‐6 and NE/α1‐antitrypsin complexes, serum C‐reactive protein, and urine TNF receptor 1 were all measured in clinically stable patients 4–6 weeks following completion of intravenous antibiotic therapy. The two groups (both n=20) were well matched for per cent predicted forced expiratory volume in one second, per cent predicted forced vital capacity and body mass index. There were no significant differences in levels of white cell counts or inflammatory markers between the two groups. At times of clinical stability, cystic fibrosis patients infected with transmissible Pseudomonas aeruginosa do not have a heightened inflammatory response above that of those harbouring sporadic strains.

Inhibition of escherichia coli glucosamine synthetase by novel electrophilic analogues of glutamine—comparison with 6-diazo-5-oxo-norleucine

A series of electrophilic glutamine analogues based on 6-diazo-5-oxo-norleucine has been prepared, using novel synthetic routes, and evaluated as inhibitors of Escherichia coli glucosamine synthetase. The gamma-dimethylsulphonium salt analogue of glutamine was found to be one of the most potent inactivators of this enzyme yet reported, with an apparent second order rate constant (k2/Ki) of 3.5 x 10(5) M(-1) min(-1).

Organisms isolated from adults with cystic fibrosis

BackgroundPatients with cystic fibrosis [CF] have frequent pulmonary exacerbations associated with the isolation of bacterial organisms from sputum samples. It is not clear however, if there are differences in the types of additional organisms isolated from patients who are infected with Burkholderia cepacia complex [BCC] or Pseudomonas aerugionsa [PA] in comparison to those who are not infected with either of these organisms [NI].MethodsAdult patients attending the regional CF unit were followed over a two year period and patients were assigned to three groups depending on whether they were known to be chronically infected with BCC, PA or NI. We compared the numbers and types of organisms which were isolated in each of these groups.ResultsInformation was available on a total of 79 patients; BCC 23, PA 30 and NI 26. Total numbers of organisms isolated, expressed as median and IQR for each group, [P = 0.045] and numbers of co-infecting organisms [P = 0.003] were significantly higher in the BCC group compared to PA, and in the PA group [P < 0.001, p = 0.007 respectively] compared to NI patients. The pattern of co-infecting organisms was similar in all three groups.ConclusionsTotal numbers of organisms isolated and numbers of co-infecting organisms were significantly higher in the BCC group compared to PA, and in the PA group compared to NI patients. Types of co-infecting organisms are similar in all groups of patients.