"Pathogen Eradication" and "Emerging Pathogens": Difficult Definitions in Cystic Fibrosis.

Infection is a common complication of cystic fibrosis (CF) airway disease. Current treatment approaches include early intervention with the intent to eradicate pathogens in the hope of delaying the development of chronic infection and the chronic use of aerosolized antibiotics to suppress infection. The use of molecules that help restore CFTR (cystic fibrosis transmembrane conductance regulator) function, modulate pulmonary inflammation, or improve pulmonary clearance may also influence the microbial communities in the airways. As the pipeline of these new entities continues to expand, it is important to define when key pathogens are eradicated from the lungs of CF patients and, equally important, when new pathogens might emerge as a result of these novel therapies.

Population pharmacokinetics of intravenous acetaminophen and its metabolites in major surgical patients.

Intravenous acetaminophen is a commonly used analgesic following surgery. The aims of this study were to determine the population pharmacokinetic profile of intravenous acetaminophen and its metabolites in adult surgical patients and to identify patient characteristics associated with acetaminophen metabolism in the postoperative period. 53 patients were included in the dataset; 28 were men, median age (range) 60 years (33-87), median weight (range) 74 kg (54-129). Patients received 1, 1.5 or 2 g of intravenous acetaminophen every 4-6 h. Plasma and urine samples were collected at various intervals for up to 6 days after surgery. Simultaneous modelling of parent acetaminophen and its metabolites was conducted in Phoenix(®) NLME™ to estimate pharmacokinetic parameters. The population mean estimate (CV%) for central (plasma) volume of distribution of parent acetaminophen (VC) was 13.9 (4.41) L, peripheral (tissue) volume of distribution (VT) was 50.9 (2.96) L, and intercompartmental clearance (Q) was 77.5 (9.29) L/h. The population mean (CV%) metabolic clearances for glucuronidation (CLPG) was 8.92 (3.25) L/h, sulfation (CLPS) was 0.903 (3.47) L/h, and oxidation (CLPO) was 0.533 (7.90) L/h. The population mean (CV%) urinary clearances of parent acetaminophen (CLRP) was 0.137 (5.46) L/h, acetaminophen glucuronide (CLRG) was 3.81 (6.71) L/h, acetaminophen sulfate (CLRS) was 3.13 (4.32) L/h, and acetaminophen cysteine + mercapturate (CLRO) was 3.51 (9.98) L/h. Age was found to be a significant covariate on the formation of acetaminophen glucuronide, and renal function (estimated as creatinine clearance) on the urinary excretion of acetaminophen glucuronide.

Evaluation of in vitro virulence characteristics of the genus Pandoraea in lung epithelial cells.

Pandoraea species are emerging opportunistic pathogens capable of causing chronic lung infections in cystic fibrosis patients. This study examined the interactions of 17 Pandoraea isolates from the five identified species (Pandoraea apista, Pandoraea norimbergensis, Pandoraea pulmonicula, Pandoraea sputorum and Pandoraea pnomenusa) plus two Pandoraea genomospecies isolates with lung epithelial cells and their ability to form biofilms in vitro. Only three isolates showed an ability to invade A549 lung epithelial cells, and only one isolate was able to form biofilms. In contrast, all isolates triggered a pronounced pro-inflammatory response, with elevation of both interleukin (IL)-6 (two- to 19-fold) and IL-8 (10- to 50-fold) above that observed for a control strain of Escherichia coli. This property is likely to be a major factor in the pathogenesis of the genus.

Differences in invasion and translocation of Burkholderia cepacia complex species in polarised lung epithelial cells in vitro.

In order to investigate the mechanisms by which Burkholderia cepacia complex (Bcc) strains cross the epithelial barrier of the lung and cause septicaemia in a subgroup of Cystic Fibrosis (CF) patients, the invasiveness of four Bcc species have been examined in three lung epithelial cells: A549, 16HBE14o- and Calu-3. The latter two cell lines form polarised monolayers when grown on filters. Invasion of both cell lines by B. multivorans strains was reduced when the cells were grown as tight monolayers compared unpolarised cells, suggesting basolateral receptors are required for the process. In contrast, four B. cenocepacia strains showed comparable invasion of both cell lines irrespective of culture model. All four species of Bcc reduced the TER of Calu-3 monolayers. However, while B. cepacia, B. multivorans and B. stabilis strains readily translocated across the epithelial monolayer, B. cenocepacia translocation was slower. Both B. multivorans and B. cenocepacia altered expression of ZO-1 in Calu-3 cells, but not E-cadherin. Overall, the findings that Bcc strains from four species, which differ greatly in their virulence, have the potential to disrupt tight junctions and to translocate across the epithelium, demonstrates this effect is not exclusive to the most virulent species.

Early detection of Pseudomonas aeruginosa--comparison of conventional versus molecular (PCR) detection directly from adult patients with cystic fibrosis (CF).

BACKGROUND: Pseudomonas aeruginosa (PA) is the most important bacterial pathogen in patients with cystic fibrosis (CF) patients. Currently, routine bacteriological culture on selective/non- selective culture media is the cornerstone of microbiological detection. The aim of this study was to compare isolation rates of PA by conventional culture and molecular (PCR) detection directly from sputum. METHODS: Adult patients (n = 57) attending the regional adult CF centre in Northern Ireland, provided fresh sputum following airways clearance exercise. Following processing of the specimen with sputasol (1:1 vol), the specimen was examined for the presence of PA by plating onto a combination of culture media (Pseudomonas isolation agar, Blood agar & McConkey agar). In addition, from the same specimen, genomic bacterial DNA was extracted (1 ml) and was amplified employing two sequence-specific targets, namely (i) the outer membrane protein (oprL) gene locus and (ii) the exotoxin A (ETA) gene locus. RESULTS: By sputum culture, there were 30 patients positive for PA, whereas by molecular techniques, there were 35 positive patients. In 39 patients (22 PA +ve & 17 PA -ve), there was complete agreement between molecular and conventional detection and with both PCR gene loci. The oprL locus was more sensitive than the ETA locus, as the former was positive in 10 more patients and there were no patients where the ETA was positive and the oprL target negative. Where a PCR +ve/culture -ve result was recorded (10 patients), we followed these patients and recorded that 5 of these patients converted to being culture-positive at times ranging from 4-17 months later, with a mean lag time of 4.5 months. CONCLUSIONS: This study indicates that molecular detection of PA in sputum employing the oprL gene target, is a useful technique in the early detection of PA, gaining on average 4.5 months over conventional culture. It now remains to be established whether aggressive antibiotic intervention at this earlier stage, based on PCR detection, has any significant benefits on clinical outcome.

Loss of microbicidal activity and increased formation of biofilm due to decreased lactoferrin activity in patients with cystic fibrosis.

Intractable formation of biofilm by and infection with the opportunistic pathogen Pseudomonas aeruginosa are hallmarks of cystic fibrosis (CF). Lactoferrin, an innate immunity protein, has recently been shown to inhibit the formation of P. aeruginosa biofilm. Partial cleavage of lactoferrin by the proteases neutrophil elastase and Pseudomonas elastase has previously been described in CF. Here, we show that cathepsins in CF secretions are responsible for complete and rapid cleavage of lactoferrin. We demonstrate that levels of lactoferrin in P. aeruginosa-positive sputum samples are decreased when corrected for inflammatory burden and that P. aeruginosa-positive sputum samples have significantly higher cathepsin activity and significantly reduced ability to inhibit formation of biofilm, compared with P. aeruginosa-negative sputum samples. We also show that cleavage of lactoferrin by cathepsin results in loss of both its microbicidal and antibiofilm activity. Loss of such a vital innate immunity protein clearly has important implications for the pathogenesis of chronic P. aeruginosa lung infection in patients with CF.