Making It Last: Storage Time and Temperature Have Differential Impacts on Metabolite Profiles of Airway Samples from Cystic Fibrosis Patients.

Metabolites of human or microbial origin have the potential to be important biomarkers of the disease state in cystic fibrosis (CF). Clinical sample collection and storage conditions may impact metabolite abundances with clinical relevance. We measured the change in metabolite composition based on untargeted gas chromatography-mass spectrometry (GC-MS) when CF sputum samples were stored at 4°C, -20°C, or -80°C with one or two freeze-thaw cycles. Daily measurements were taken for 1 week and then weekly for 4 weeks (4°C) and 8 weeks (-20°C). The metabolites in samples stored at -20°C maintained abundances similar to those found at-80°C over the course of 8 weeks (average change in Bray-Curtis distance, 0.06 ± 0.04) and were also stable after one or two freeze-thaw cycles. However, the metabolite profiles of samples stored at 4°C shifted after 1 day and continued to change over the course of 4 weeks (average change in Bray-Curtis distance, 0.31 ± 0.12). The abundances of several amino acids and other metabolites increased with time of storage at 4°C but remained constant at -20°C. Storage temperature was a significant factor driving the metabolite composition (permutational multivariate analysis of variance: r2 = 0.32 to 0.49, P < 0.001). CF sputum samples stored at -20°C at the time of sampling maintain a relatively stable untargeted GC-MS profile. Samples should be frozen on the day of collection, as more than 1 day at 4°C impacts the global composition of the metabolites in the sample. IMPORTANCE Metabolomics has great potential for uncovering biomarkers of the disease state in CF and many other contexts. However, sample storage timing and temperature may alter the abundance of clinically relevant metabolites. To assess whether existing samples are stable and to direct future study design, we conducted untargeted GC-MS metabolomic analysis of CF sputum samples after one or two freeze-thaw cycles and storage at 4°C and -20°C for 4 to 8 weeks. Overall, storage at -20°C and freeze-thaw cycles had little impact on metabolite profiles; however, storage at 4°C shifted metabolite abundances significantly. GC-MS profiling will aid in our understanding of the CF lung, but care should be taken in studies using sputum samples to ensure that samples are properly stored

Infection by Ralstonia Species in Cystic Fibrosis Patients: Identification of R. pickettii and R. mannitolilytica by Polymerase Chain Reaction

The frequency of respiratory tract infections caused by Ralstonia species in persons with cystic fibrosis (CF) and the role of these species in CF pulmonary disease are not well documented. In part, this lack of documentation may be attributed to the difficulty in accurately identifying Ralstonia species; R. mannitolilytica and R. pickettii in particular may be misidentified as other closely related species, particularly those of the Burkholderia cepacia complex. We used polyphasic analyses to identify 42 Ralstonia isolates from sputum cultures from 38 CF patients. Several isolates that could not be identified to the species level may belong to novel Ralstonia species. We demonstrated chronic colonization by using genotyping of serial isolates recovered from the same patient. To facilitate identification of R. mannitolilytica and R. pickettii, we developed 16S ribosomal DNA-based polymerase chain reaction assays that allow sensitive and specific identification of these species

Cystic fibrosis lung microbiome: Opportunities to reconsider management of airway infection

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/113756/1/ppul23243.pd

Evidence of transmission of Burkholderia cepacia , Burkholderia multivorans and Burkholderia dolosa among persons with cystic fibrosis

Previous studies have identified specific Burkholderia cepacia complex strains that are common to multiple persons with cystic fibrosis (CF). Such so-called epidemic strains have an apparent enhanced capacity for inter-patient spread and reside primarily in Burkholderia cenocepacia (formerly B. cepacia complex genomovar III). We sought to identify strains from B. cepacia complex species other than B. cenocepacia that are similarly shared by multiple CF patients. We performed genotype analysis of 360 recent sputum culture isolates from 360 persons residing in 29 cities by using repetitive extragenic palendromic polymerase chain reaction (rep-PCR) and pulsed field gel electrophoresis. The results indicate that sharing of a common Burkholderia multivorans strain occurs relatively infrequently; however, several small clusters of patients infected with the same strain were identified. A cluster of seven patients infected with the same B. cepacia (genomovar I) strain was found. We also identified a large group of 28 patients receiving care in the same treatment center and infected with the same Burkholderia dolosa strain. These observations suggest that B. cepacia complex strains in species other than B. cenocepacia may be spread among CF patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72506/1/S0378-1097_03_00724-9.pd

Impact of Burkholderia Infection on Lung Transplantation in Cystic Fibrosis

Rationale: Lung transplantation offers the only survival option for patients with cystic fibrosis (CF) with end-stage pulmonary disease. Infection with Burkholderia species is typically considered a contraindication to transplantation in CF. However, the risks posed by different Burkholderia species on transplantation outcomes are poorly defined. Objectives: To quantify the risks of infection with Burkholderia species on survival before and after lung transplantation in patients with CF. Methods: Multivariate Cox survival models assessed hazard ratios of infection with Burkholderia species in 1,026 lung transplant candidates and 528 lung transplant recipients. Lung allocation scores, incorporating Burkholderia infection status, were calculated for transplant candidates. Measurements and Main Results: Transplant candidates infected with different Burkholderia species did not have statistically different mortality rates. Among transplant recipients infected with B. cenocepacia, only those infected with nonepidemic strains had significantly greater post-transplant mortality compared with uninfected patients (hazard ratio [HR], 2.52; 95% confidence interval [CI], 1.04–6.12; P 5 0.04). Hazards were similar between uninfected transplant recipients and those infected with B. multivorans (HR, 0.66; 95% CI, 0.27–1.56; P 5 0.34). Transplant recipients infected with B. gladioli had significantly greater post-transplant mortality than uninfected patients (HR, 2.23; 95% CI, 1.05–4.74; P 5 0.04). Oncehazards for species/strainwereincluded,lung allocation scores of B. multivorans–infected transplant candidates were comparable to uninfected candidate scores, whereas those of candidates infected with nonepidemic B. cenocepacia or B. gladioli were lower. Conclusions: Post-transplant mortality among patients with CF infected with Burkholderia varies by infecting species. This variability should be taken into account in evaluating lung transplantation candidates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91898/1/Murray LiPuma AJRCCM 2008.pd

Spontaneous and evolutionary changes in the antibiotic resistance of Burkholderia cenocepacia observed by global gene expression analysis

Abstract Background Burkholderia cenocepacia is a member of the Burkholderia cepacia complex group of bacteria that cause infections in individuals with cystic fibrosis. B. cenocepacia isolate J2315 has been genome sequenced and is representative of a virulent, epidemic CF strain (ET12). Its genome encodes multiple antimicrobial resistance pathways and it is not known which of these is important for intrinsic or spontaneous resistance. To map these pathways, transcriptomic analysis was performed on: (i) strain J2315 exposed to sub-inhibitory concentrations of antibiotics and the antibiotic potentiator chlorpromazine, and (ii) on spontaneous mutants derived from J2315 and with increased resistance to the antibiotics amikacin, meropenem and trimethoprim-sulfamethoxazole. Two pan-resistant ET12 outbreak isolates recovered two decades after J2315 were also compared to identify naturally evolved gene expression changes. Results Spontaneous resistance in B. cenocepacia involved more gene expression changes and different subsets of genes than those provoked by exposure to sub inhibitory concentrations of each antibiotic. The phenotype and altered gene expression in the resistant mutants was also stable irrespective of the presence of the priming antibiotic. Both known and novel genes involved in efflux, antibiotic degradation/modification, membrane function, regulation and unknown functions were mapped. A novel role for the phenylacetic acid (PA) degradation pathway genes was identified in relation to spontaneous resistance to meropenem and glucose was found to repress their expression. Subsequently, 20 mM glucose was found to produce greater that 2-fold reductions in the MIC of multiple antibiotics against B. cenocepacia J2315. Mutation of an RND multidrug efflux pump locus (BCAM0925-27) and squalene-hopene cyclase gene (BCAS0167), both upregulated after chlorpromazine exposure, confirmed their role in resistance. The recently isolated outbreak isolates had altered the expression of multiple genes which mirrored changes seen in the antibiotic resistant mutants, corroborating the strategy used to model resistance. Mutation of an ABC transporter gene (BCAS0081) upregulated in both outbreak strains, confirmed its role in B. cenocepacia resistance. Conclusions Global mapping of the genetic pathways which mediate antibiotic resistance in B. cenocepacia has revealed that they are multifactorial, identified potential therapeutic targets and also demonstrated that putative catabolite repression of genes by glucose can improve antibiotic efficacy.http://deepblue.lib.umich.edu/bitstream/2027.42/134738/1/12864_2010_Article_3517.pd

Spontaneous and evolutionary changes in the antibiotic resistance of Burkholderia cenocepacia observed by global gene expression analysis

Abstract Background Burkholderia cenocepacia is a member of the Burkholderia cepacia complex group of bacteria that cause infections in individuals with cystic fibrosis. B. cenocepacia isolate J2315 has been genome sequenced and is representative of a virulent, epidemic CF strain (ET12). Its genome encodes multiple antimicrobial resistance pathways and it is not known which of these is important for intrinsic or spontaneous resistance. To map these pathways, transcriptomic analysis was performed on: (i) strain J2315 exposed to sub-inhibitory concentrations of antibiotics and the antibiotic potentiator chlorpromazine, and (ii) on spontaneous mutants derived from J2315 and with increased resistance to the antibiotics amikacin, meropenem and trimethoprim-sulfamethoxazole. Two pan-resistant ET12 outbreak isolates recovered two decades after J2315 were also compared to identify naturally evolved gene expression changes. Results Spontaneous resistance in B. cenocepacia involved more gene expression changes and different subsets of genes than those provoked by exposure to sub inhibitory concentrations of each antibiotic. The phenotype and altered gene expression in the resistant mutants was also stable irrespective of the presence of the priming antibiotic. Both known and novel genes involved in efflux, antibiotic degradation/modification, membrane function, regulation and unknown functions were mapped. A novel role for the phenylacetic acid (PA) degradation pathway genes was identified in relation to spontaneous resistance to meropenem and glucose was found to repress their expression. Subsequently, 20 mM glucose was found to produce greater that 2-fold reductions in the MIC of multiple antibiotics against B. cenocepacia J2315. Mutation of an RND multidrug efflux pump locus (BCAM0925-27) and squalene-hopene cyclase gene (BCAS0167), both upregulated after chlorpromazine exposure, confirmed their role in resistance. The recently isolated outbreak isolates had altered the expression of multiple genes which mirrored changes seen in the antibiotic resistant mutants, corroborating the strategy used to model resistance. Mutation of an ABC transporter gene (BCAS0081) upregulated in both outbreak strains, confirmed its role in B. cenocepacia resistance. Conclusions Global mapping of the genetic pathways which mediate antibiotic resistance in B. cenocepacia has revealed that they are multifactorial, identified potential therapeutic targets and also demonstrated that putative catabolite repression of genes by glucose can improve antibiotic efficacy.http://deepblue.lib.umich.edu/bitstream/2027.42/116207/1/12864_2010_Article_3517.pd

Susceptibility of Caenorhabditis elegans to Burkholderia Infection Depends on Prior Diet and Secreted Bacterial Attractants

The nematode Caenorhabditis elegans may be killed by certain pathogenic bacteria and thus is a model organism for studying interactions between bacteria and animal hosts. However, growing nematodes on prey bacteria may influence their susceptibility to potential pathogens. A method of axenic nematode culture was developed to isolate and quantify interactions between C. elegans and potentially pathogenic strains of the Burkholderia cepacia complex. Studying these dynamics in liquid solution rather than on agar surfaces minimized nematode avoidance behavior and resolved more differences among isolates. Most isolates of B. cenocepacia, B. ambifaria and B. cepacia caused 60–80% mortality of nematodes after 7 days, whereas isolates of B. multivorans caused less mortality (<25%) and supported nematode reproduction. However, some B. cenocepacia isolates recovered from chronic infections were much less virulent (5–28% mortality). As predicted, prior diet altered the outcome of interactions between nematodes and bacteria. When given the choice between Burkholderia and E. coli as prey on agar, axenically raised nematodes initially preferred most lethal Burkholderia isolates to E. coli as a food source, but this was not the case for nematodes fed E. coli, which avoided toxic Burkholderia. This food preference was associated with the cell-free supernatant and thus secreted compounds likely mediated bacterial-nematode interactions. This model, which isolates interactions between bacteria and nematodes from the effects of prior feeding, demonstrates that bacteria can influence nematode behavior and their susceptibility to pathogens

Reactivity of Haemophilus influenzae type b anti-pili antibodies

The reactivity of anti-pilus antibodies to native and denatured Haemophilus influenzae b (Hib) pili was studied using rabbit serum prepared against piliated H. influenzae b strain M43 (p+) and adsorbed with its non-piliated variant, strain M42 (p-). The specificity of the adsorbed serum for Hib pili was documented by immunogold electron microscopy and by immunoprecipitation, which revealed the 24 kDa pilin band from strain M43 (p+) that was not seen on strain M42 (p-1). In immunodot assays, the anti-pilus antibodies reacted with the native pili present on the outer membrane of strain M43 (p+), but on Western blot assay using denatured outer membranes, the anti-pilus antibodies did not react with the 24 kDa pilin subunit. These data demonstrate that the anti-pilus antibodies in the adsorbed serum recognize conformational epitopes that depend on the tertiary or quaternary structure of Hib pili.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27738/1/0000130.pd

Burkholderia anthina sp. nov. and Burkholderia pyrrocinia , two additional Burkholderia cepacia complex bacteria, may confound results of new molecular diagnostic tools

Nineteen Burkholderia cepacia -like isolates of human and environmental origin could not be assigned to one of the seven currently established genomovars using recently developed molecular diagnostic tools for B. cepacia complex bacteria. Various genotypic and phenotypic characteristics were examined. The results of this polyphasic study allowed classification of the 19 isolates as an eighth B. cepacia complex genomovar ( Burkholderia anthina sp. nov.) and to design tools for its identification in the diagnostic laboratory. In addition, new and published data for Burkholderia pyrrocinia indicated that this soil bacterium is also a member of the B. cepacia complex. This highlights another potential source for diagnostic problems with B. cepacia -like bacteria.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71564/1/j.1574-695X.2002.tb00584.x.pd