Role of Tris-CaEDTA as an adjuvant with nebulised tobramycin in cystic fibrosis patients with Pseudomonas aeruginosa lung infections: A randomised controlled trial.

BACKGROUND: We tested if disrupting iron utilisation by P. aeruginosa by adding the Tris-buffered chelating agent CaEDTA to nebulised tobramycin would enhance bacterial clearance and improve lung function in CF patients. METHODS: In this double-blind, randomised controlled trial, 26 episodes (25 patients) with P. aeruginosa infection admitted to two CF centres for treatment of an acute pulmonary exacerbation were randomly assigned to receive either 75 mg CaEDTA in Tris-buffered saline or placebo (Tris-buffered saline) nebulised in combination with 250 mg tobramycin twice daily for six weeks followed with four week safety follow-up. Primary endpoints were safety, tolerability, and bacterial density of P. aeruginosa. A secondary endpoint was lung function. RESULTS: The study drug was well tolerated with adverse events comparable in both groups. The mean (SD) reduction in sputum P. aeruginosa count (log10 CFU/g) in the CaEDTA vs placebo group was 2·05 (2·57) vs 0·82 (2·71) at two weeks relative to admission (p = 0·39). The mean improvement in ppFEV1 was 16 vs 5 (p = 0·16); 11 vs 2 (p = 0·28); and 6 vs 2 percentage points (p = 0·47) at two, six, and ten weeks in CaEDTA and placebo groups, respectively. CONCLUSIONS: In this pilot study in CF patients, an increase in the reduction of sputum density of P. aeruginosa and an increase in ppFEV1 was observed in the group of patients who received Tris-CaEDTA added to inhaled tobramycin compared to the group who received inhaled tobramycin alone, although these differences were not statistically significant. The treatment was also shown to be safe.

Pseudomonas aeruginosa antibiotic resistance in Australian cystic fibrosis centres.

BACKGROUND AND OBJECTIVE: In cystic fibrosis (CF), chronic Pseudomonas aeruginosa infection is associated with increased morbidity, antibiotic treatments and mortality. By linking Australian CF registry data with a national microbiological data set, we examined the association between where treatment was delivered, its intensity and P. aeruginosa antibiotic resistance. METHODS: Sputa were collected from paediatric and adult CF patients attending 18 Australian CF centres. P. aeruginosa antibiotic susceptibilities determined by local laboratories were correlated with clinical characteristics, treatment intensity and infection with strains commonly shared among Australian CF patients. Between-centre differences in treatment and antibiotic resistance were also compared. RESULTS: Large variations in antibiotic usage, maintenance treatment practices and multi-antibiotic resistant P. aeruginosa (MARPA) prevalence exist between Australian CF centres, although the overall proportions of MARPA isolates were similar in paediatric and adult centres (31% vs 35%, P = 0.29). Among paediatric centres, MARPA correlated with intravenous antibiotic usage and the Australian state where treatment was delivered, while azithromycin, reduced lung function and treating state predicted intravenous antibiotic usage. In adult centres, body mass index (BMI) and treating state were associated with MARPA, while intravenous antibiotic use was predicted by gender, BMI, dornase-alpha, azithromycin, lung function and treating state. In adults, P. aeruginosa strains AUST-01 and AUST-02 independently predicted intravenous antibiotic usage. CONCLUSION: Increased treatment intensity in paediatric centres and the Australian state where treatment was received are both associated with greater risk of MARPA, but not worse clinical outcomes.

Iron-binding compounds impair Pseudomonas aeruginosa biofilm formation, especially under anaerobic conditions.

The success of Pseudomonas aeruginosa in cystic fibrosis (CF) and other chronic infections is largely attributed to its ability to grow in antibiotic-resistant biofilm communities. This study investigated the effects of limiting iron levels as a strategy for preventing/disrupting P. aeruginosa biofilms. A range of synthetic and naturally occurring iron-chelating agents were examined. Biofilm development by P. aeruginosa strain PAO1 and CF sputum isolates from chronically infected individuals was significantly decreased by iron removal under aerobic atmospheres. CF strains formed poor biofilms under anaerobic conditions. Strain PAO1 was also tested under anaerobic conditions. Biofilm formation by this model strain was almost totally prevented by several of the chelators tested. The ability of synthetic chelators to impair biofilm formation could be reversed by iron addition to cultures, providing evidence that these effective chelating compounds functioned by directly reducing availability of iron to P. aeruginosa. In contrast, the biological chelator lactoferrin demonstrated enhanced anti-biofilm effects as iron supplementation increased. Hence biofilm inhibition by lactoferrin appeared to occur through more complex mechanisms to those of the synthetic chelators. Overall, our results demonstrate the importance of iron availability to biofilms and that iron chelators have potential as adjunct therapies for preventing biofilm development, especially under low oxygen conditions such as encountered in the chronically infected CF lung.

Iron deficiency in cystic fibrosis: relationship to lung disease severity and chronic Pseudomonas aeruginosa infection.

BACKGROUND: Iron deficiency (ID) is common in patients with cystic fibrosis (CF) and may be related to GI factors and chronic inflammation. Pseudomonas aeruginosa (PA) infection is predominantly responsible for chronic lung suppuration in patients with CF, but its survival is critically dependent on the availability of extracellular iron, which it obtains via highly efficient mechanisms. OBJECTIVE: To determine whether ID in CF patients is directly related to the severity of suppurative lung disease. DESIGN: We determined the iron status of 30 randomly selected adult CF patients (13 women) and assessed the relationship to lung disease severity and GI factors by determining their daily sputum volume, FEV(1) percent predicted, C-reactive protein (CRP) level, erythrocyte sedimentation rate, and degree of pancreatic supplementation. Additionally, we measured the sputum concentrations of iron and ferritin in a randomly selected subgroup of 13 of the 30 subjects. SETTING: Adult CF Service in a tertiary-care center. RESULTS: Seventy-four percent of subjects experienced ID (ie, serum iron levels < or = 12 micromol/L and/or transferrin saturation levels < or = 16%). There was no relationship found with the degree of pancreatic supplementation. The daily sputum volume was strongly associated with low serum iron levels, transferrin saturation, ferritin/CRP ratio, and FEV(1) percent predicted (p < 0.05). Serum iron levels and transferrin saturation were negatively related to CRP (r = -0.8 and r = -0.7, respectively; p < 0.01) and erythrocyte sedimentation rate (r = -0.5 and r = -0.4, respectively; p < 0.05). FEV(1) percent predicted was positively related to serum iron level (r = 0.5; p < 0.01), transferrin saturation (r = 0.4; p < 0.05), and ferritin/CRP ratio (r = 0.7; p < 0.05). Sputum iron concentration (median, 63 micromol/L; range, 17 to 134 micromol/L) and ferritin concentration (median, 5,038 microg/L; range, 894 to 6,982 microg/L) exceeded plasma levels and negatively correlated with FEV(1) percent predicted (r = -0.6 and r = -0.5, respectively; p < or = 0.05). CONCLUSION: In our CF patients, ID was directly related to the increased severity of suppurative lung disease but not to the degree of pancreatic insufficiency. Iron loss into the airway may contribute to ID and may facilitate PA infection.