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1.  The role of 2,4-dihydroxyquinoline (DHQ) in Pseudomonas aeruginosa pathogenicity 
PeerJ  2016;4:e1495.
Bacteria synchronize group behaviors using quorum sensing, which is advantageous during an infection to thwart immune cell attack and resist deleterious changes in the environment. In Pseudomonas aeruginosa, the Pseudomonas quinolone signal (Pqs) quorum-sensing system is an important component of an interconnected intercellular communication network. Two alkylquinolones, 2-heptyl-4-quinolone (HHQ) and 2-heptyl-3-hydroxy-4-quinolone (PQS), activate transcriptional regulator PqsR to promote the production of quinolone signals and virulence factors. Our work focused on the most abundant quinolone produced from the Pqs system, 2,4-dihydroxyquinoline (DHQ), which was shown previously to sustain pyocyanin production and antifungal activity of P. aeruginosa. However, little is known about how DHQ affects P. aeruginosa pathogenicity. Using C. elegans as a model for P. aeruginosa infection, we found pqs mutants only able to produce DHQ maintained virulence towards the nematodes similar to wild-type. In addition, DHQ-only producing mutants displayed increased colonization of C. elegans and virulence factor production compared to a quinolone-null strain. DHQ also bound to PqsR and activated the transcription of pqs operon. More importantly, high extracellular concentration of DHQ was maintained in both aerobic and anaerobic growth. High levels of DHQ were also detected in the sputum samples of cystic fibrosis patients. Taken together, our findings suggest DHQ may play an important role in sustaining P. aeruginosa pathogenicity under oxygen-limiting conditions.
PMCID: PMC4715436  PMID: 26788419
Pseudomonas aeruginosa; Quorum sensing; Pathogenicity; Cystic fibrosis; Pseudomonas quinolone signal; Transcriptional regulation
2.  Optimising inhaled mannitol for cystic fibrosis in an adult population 
Breathe  2015;11(1):39-48.
There has been remarkable progress in the treatment of cystic fibrosis (CF) patients over the past 20 years. However, limitations of standard therapies have highlighted the need for a convenient alternative treatment to effectively target the pathophysiologic basis of CF-related disease by improving mucociliary clearance of airway secretions and consequently improve lung function and reduce respiratory exacerbations. Mannitol is an osmotic agent available as a dry powder, dispensed in a convenient disposable inhaler device for the treatment of adult patients with CF. Inhalation of mannitol as a dry powder is thought to change the viscoelastic properties of airway secretions, increase the hydration of the airway surface liquid and contribute to increased mucociliary and cough clearance of retained secretions. In two large phase 3 studies [1, 2], long-term use of inhaled mannitol resulted in a significant and clinically meaningful improvement in lung function relative to control in adult CF subjects and had an acceptable safety profile. Clinical experience with inhaled mannitol confirms that it is safe and effective. A minority of patients are unable to tolerate the medication. However, through training in proper inhaler technique and setting clear expectations regarding therapeutic effects, both the tolerance and adherence necessary for long term efficacy can be positively influenced.
Educational aims
To discuss the importance of airway clearance treatments in the management of cystic fibrosis.
To describe the clinical data that supports the use of mannitol in adult patients with cystic fibrosis.
To highlight the role of mannitol tolerance testing in screening for hyperresponsiveness.
To provide practical considerations for patient education in use of mannitol inhaler.
Key points
Inhaled mannitol is a safe and effective option in adult patients with cystic fibrosis.
Mannitol tolerance testing effectively screens for hyperresponsiveness prior to initiation of therapy.
Physiotherapists and respiratory therapists play an integral role in the introduction and maintenance of dry powder inhalation therapy.
Patient training and follow-up is important for optimising longer term adherence.
PMCID: PMC4487380  PMID: 26306102
A light-porous-particle, dry-powder formulation of tobramycin was developed, using PulmoSphere® technology, to improve airway delivery efficiency, substantially reduce delivery time, and improve patient convenience and satisfaction. We evaluated the safety, efficacy and convenience of tobramycin inhalation powder (TIP™) versus tobramycin inhalation solution (TIS, TOBI®) for treating Pseudomonas aeruginosa infection in cystic fibrosis (CF) patients aged ≥6 years.
In this open-label study, 553 patients were randomized 3:2 to TIP (total 112 mg tobramycin) via the Novartis T-326 Inhaler or TIS 300 mg/5 mL via PARI LC® PLUS nebulizer twice daily for three treatment cycles (28 days on-drug, 28 days off-drug). Safety, efficacy, and treatment satisfaction outcomes were evaluated.
TIP was generally well-tolerated; adverse events were similar in both groups. The rate of cough suspected to be study-drug related was higher in TIP-treated patients (TIP: 25.3%; TIS: 4.3%), as was the overall discontinuation rate (TIP: 26.9%; TIS: 18.2%). Increases in FEV1 % predicted from baseline to Day 28 of Cycle 3 were similar between groups; mean reduction in sputum Pseudomonas aeruginosa density (log10 CFU/g) on Day 28 of Cycle 3 was also comparable between groups. Administration time was significantly less for TIP (mean: 5.6 versus 19.7 minutes, p<0.0001). Treatment satisfaction was significantly higher for TIP for effectiveness, convenience, and global satisfaction.
TIP has a safety and efficacy profile comparable with TIS, and offers a far more convenient treatment option for pseudomonas lung infection in CF.
PMCID: PMC4086197  PMID: 21075062
cystic fibrosis; tobramycin inhalation powder (TIP™); pseudomonas aeruginosa; lung infection
4.  State of progress in treating cystic fibrosis respiratory disease 
BMC Medicine  2012;10:88.
Since the discovery of the gene associated with cystic fibrosis (CF), there has been tremendous progress in the care of patients with this disease. New therapies have entered the market and are part of the standard treatment of patients with CF, and have been associated with marked improvement in survival. Now there are even more promising therapies directed at different components of the pathophysiology of this disease. In this review, our current knowledge of the pathophysiology of lung disease in patients with CF is described, along with the current treatment of CF lung disease, and the therapies in development that offer great promise to our patients.
PMCID: PMC3425089  PMID: 22883684
cystic fibrosis; pathophysiology; treatment
5.  Pharmacokinetics and Safety of MP-376 (Levofloxacin Inhalation Solution) in Cystic Fibrosis Subjects▿ 
The pharmacokinetics and tolerability of nebulized MP-376 (levofloxacin inhalation solution [Aeroquin]) were determined in cystic fibrosis (CF) subjects. Ten CF subjects received single 180-mg doses of two formulations of MP-376, followed by a multiple-dose phase of 240 mg once daily for 7 days. Serum and expectorated-sputum samples were assayed for levofloxacin content. Safety was evaluated following the single- and multiple-dose study phases. Nebulized MP-376 produced high concentrations of levofloxacin in sputum. The mean maximum plasma concentration (Cmax) ranged between 2,563 and 2,932 mg/liter for 180-mg doses of the 50- and 100-mg/ml formulations, respectively. After 7 days of dosing, the mean Cmax for the 240-mg dose was 4,691 mg/liter. The mean serum levofloxacin Cmax ranged between 0.95 and 1.28 for the 180-mg doses and was 1.71 for the 240-mg dose. MP-376 was well tolerated. Nebulized MP-376 produces high sputum and low serum levofloxacin concentrations. The pharmacokinetics, safety, and tolerability were similar for the two formulations. MP-376 240 mg (100 mg/ml) is being advanced into late-stage clinical development.
PMCID: PMC3101414  PMID: 21444699
6.  Linezolid Pharmacokinetics in Adult Patients with Cystic Fibrosis 
The pharmacokinetics of many drugs are altered in patients with cystic fibrosis (CF), often necessitating different dosage requirements than those used in non-CF patients. The objective of this study was to determine the pharmacokinetics of linezolid, an antibiotic with good activity against gram-positive organisms such as methicillin-resistant Staphylococcus aureus, in patients with CF so that dosage requirements could be established. Twelve adult patients (6 male) ranging in age from 22 to 39 years were studied. A single 600-mg dose was administered intravenously over 0.5 h, and plasma samples were collected at 0 (predose), 0.5, 0.75, 1, 2, 4, 8, and 24 h. Linezolid concentrations were determined with a validated high-performance liquid chromatography assay. Pharmacokinetic parameters were estimated using standard noncompartmental methods. Blood chemistry and hematologic indices were determined before and after the study for safety purposes. All patients completed the study without encountering any adverse reactions. The pharmacokinetic parameters, while variable, with half-lives varying from 1.76 to 8.36 h, were similar to those previously described in other populations. Mean (± standard deviation) values for pharmacokinetic parameters of interest were as follows: elimination rate constant, 0.21 (0.11) h−1; half-life, 4.41 (2.43); volume of distribution at steady state, 0.87 (0.19) liters/kg of body weight; and total body clearance, 0.12 (0.06) liters/h/kg. No patient would have achieved the pharmacodynamic target of an area under the concentration-time curve/MIC ratio of 83 h for pathogens for which the MIC was 4 μg/ml. Patients with inadequate clinical responses to linezolid may require more frequent dosing.
PMCID: PMC310170  PMID: 14693551

Results 1-6 (6)