Phenotypic and Genotypic Adaptations in Pseudomonas aeruginosa Biofilms following Long-Term Exposure to an Alginate Oligomer Therapy.

Chronic Pseudomonas aeruginosa lung infections in cystic fibrosis (CF) evolve to generate environmentally adapted biofilm communities, leading to increased patient morbidity and mortality. OligoG CF-5/20, a low-molecular-weight inhaled alginate oligomer therapy, is currently in phase IIb/III clinical trials in CF patients. Experimental evolution of P. aeruginosa in response to OligoG CF-5/20 was assessed using a bead biofilm model allowing continuous passage (45 days; ∼245 generations). Mutants isolated after OligoG CF-5/20 treatment typically had a reduced biofilm-forming ability and altered motility profile. Genotypically, OligoG CF-5/20 provided no selective pressure on genomic mutations within morphotypes. Chronic exposure to azithromycin, a commonly prescribed antibiotic in CF patients, with or without OligoG CF-5/20 in the biofilm evolution model also had no effect on rates of resistance acquisition. Interestingly, however, cross-resistance to other antibiotics (e.g., aztreonam) was reduced in the presence of OligoG CF-5/20. Collectively, these findings show no apparent adverse effects from long-term exposure to OligoG CF-5/20, instead resulting in both fewer colonies with multidrug resistance (MDR)-associated phenotypes and improved antibiotic susceptibility of P. aeruginosaIMPORTANCE The emergence of multidrug-resistant (MDR) pathogens within biofilms in the cystic fibrosis lung results in increased morbidity. An inhalation therapy derived from alginate, OligoG CF-5/20, is currently in clinical trials for cystic fibrosis patients. OligoG CF-5/20 has been shown to alter sputum viscoelasticity, disrupt mucin polymer networks, and disrupt MDR pseudomonal biofilms. Long-term exposure to inhaled therapeutics may induce selective evolutionary pressures on bacteria within the lung biofilm. Here, a bead biofilm model with repeated exposure of P. aeruginosa to OligoG CF-5/20 (alone and in combination with azithromycin) was conducted to study these long-term effects and characterize the phenotypic and genotypic adaptations which result. These findings, over 6 weeks, show that long-term use of OligoG CF-5/20 does not lead to extensive mutational changes and may potentially decrease the pathogenicity of the bacterial biofilm and improve the susceptibility of P. aeruginosa to other classes of antibiotics.

Effectiveness of pulse-oximetry in addition to routine neonatal examination in detection of congenital heart disease in asymptomatic newborns.

OBJECTIVE: To assess the feasibility and effectiveness of pulse-oximetry as a screening tool in the detection of critical congenital heart disease (CCHD) in newborns. METHODS: Post-natal babies born between 01/01/2007-31/12/2009 were eligible. Post-ductal pulse-oximetry was performed using Nellcor® NPB 40 pulse oximeter with reusable OXI-A/N saturation probe. Saturations ≥95% were deemed normal. If saturations were <95%, an echocardiogram was done. The regional paediatric cardiology database and death records identified babies later diagnosed with CCHD. RESULTS: 6329/9613 eligible babies were studied and pulse-oximetry was performed at a mean age of 28 hours (range 6-72 hours). Fourteen babies had saturations <95%. CCHD was diagnosed in 7/14 babies; 4/7 had no clinical signs. Of the remaining 7 babies, 3 had non-critical but significant CHD and 4 had an undiagnosed respiratory illness or sepsis. All babies with low saturations had identifiable pathologies. One baby with normal saturations was later diagnosed with transposition of the great arteries. The sensitivity and specificity of identifying an unwell baby was 93.3% and 100% respectively; the sensitivity and specificity of identifying CCHD was 87.5% and 99.8% respectively. Clinical examination alone would have missed 4/7 (57%) of these. CONCLUSION: Pulse-oximetry is safe, acceptable, non-invasive and effective. Our study supports the routine use of pulse oximetry as part of the newborn check.