Prolonged anoxic exposure impacts antibiotic sensitivity profiles of Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Infectious Diseases
• Pharmacology

Background:

• Chronic respiratory infections often involve Pseudomonas aeruginosa in oxygen-limited niches.
• Mucus plugs in conditions like cystic fibrosis create these environments, potentially altering bacterial antibiotic sensitivity.
• The effects of prolonged anoxia on Pseudomonas aeruginosa antibiotic sensitivity are not well understood.

Purpose of the Study:

• To investigate how prolonged anoxic exposure affects Pseudomonas aeruginosa antibiotic sensitivity.
• To compare the antibiotic sensitivity of anoxic-conditioned strains with parental strains under varying oxygen conditions.

Main Methods:

• Developed anoxic-conditioned Pseudomonas aeruginosa strains through 22 days of passaging in an anoxic environment.
• Conducted time-kill assays using ceftazidime, ciprofloxacin, colistin, and tobramycin.
• Tested both parental and anoxic-conditioned strains in both anoxic and aerobic conditions.

Main Results:

• Anoxic-conditioned strains showed increased susceptibility to tobramycin.
• Reduced sensitivity to colistin and ceftazidime was observed in anoxic-conditioned strains.
• Ciprofloxacin showed a steeper killing rate against conditioned strains, but 24-h outcomes were similar.

Conclusions:

• Prolonged anoxia significantly alters Pseudomonas aeruginosa antibiotic sensitivity, differing from acute anoxia effects.
• Observed changes in susceptibility are linked to altered killing rates or reduced regrowth.
• Findings have implications for managing chronic Pseudomonas aeruginosa infections in oxygen-limited environments.