Antimicrobial effect of hypertonic saline on <em>Pseudomonas aeruginosa</em> isolates from cystic fibrosis lung infections — ASN Events
  1. Schedule
  2. Poster Session C
  3. Antimicrobial effect of hypertonic saline on Pseudomonas aeruginosa isolates from cystic fibrosis lung infections

Antimicrobial effect of hypertonic saline on Pseudomonas aeruginosa isolates from cystic fibrosis lung infections (#414)

Honghua Hu 1 , Maria Mempin 1 , Mark Elkins 2 , Barbara Rose 3 , Jim Manos 3 , Peter Bye 4 , Colin Harbour 3 , Karen Vickery 1
  1. Faculty of Medicine and Health Sciences, Macquarie University, North Ryde, NSW, Australia
  2. Department of Respiratory Medicine, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
  3. Department of Infectious Diseases and Immunology, University of Sydney, Camperdown, NSW, Australia
  4. Department of Medicine, University of Sydney, Camperdown, NSW, Australia

Introduction
Chronic Pseudomonas aeruginosa lung infection is the major cause of morbidity and mortality in people with cystic fibrosis (CF) and it is marked by the emergence of mucoid isolates over-producing alginate. Nebulised hypertonic saline (7% NaCl) (HS) has been shown to improve mucus clearance and reduce pulmonary exacerbations in CF patients1. We measured the antimicrobial effect of hypertonic saline on P. aeruginosa isolates from the lungs of people with CF, as a potential mechanism for the beneficial effect of HS in CF.

Methods
Twenty-four saline naïve P. aeruginosa isolates (12 mucoid and 12 non-mucoid) from 24 patients with chronic CF lung infection were shocked with 7% (w/v) NaCl and the effects on bacterial growth and survival rate assessed. A time-course survival rate following 7% NaCl shock was also carried out. Furthermore, minimal inhibitory concentration (MIC), minimal biofilm inhibitory concentration (MBIC), minimal eradication concentration (MEC) and minimal biofilm eradication concentration (MBEC) were determined using 1% to 16% (w/v) NaCl solutions with 1% increments.

Results
Shock treatment of P. aeruginosa isolates with hypertonic saline (7% NaCl) reduced survival rates when compared with isolates grown in physiological saline (0.9% NaCl) (p < 0.001). The survival rate of mucoid isolates (2.0%±3.7%) was significantly lower than that of non-mucoid isolates (6.6%±11%) (p < 0.05). The survival rates of isolates shocked in 7% NaCl declined with increasing exposure time (p < 0.05). The MIC range for mucoid isolates was 3-6% compared with 6-7% for non-mucoid isolates. The MBIC range for mucoid isolates was 4-7% compared with 7% to >16% for non-mucoid isolates. The MEC range for mucoid and non-mucoid isolates was 10-15% and 15 to >16% respectively. The MBEC range for mucoid and non-mucoid isolates was 11-15% and ≥16% respectively.

Conclusion
Our findings suggest that HS exerts its beneficial effects in CF partly by inhibiting growth and reducing survival rates of P. aeruginosa especially mucoid isolates. However, HS  treatment failed to eradicate both planktonic and biofilm P. aeruginosa.

  1. Elkins et al, 2006. A controlled trial of long-term inhaled hypertonic saline in patients with cystic fibrosis. N. Engl. J. Med. 354(3): 229-240.
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