Effect of Ciprofloxacin on Planktonic Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic human pathogen that causes nosocomial, acute, and chronic infections in patients with conditions such as cystic fibrosis, severe burns, and cancer. P. aeruginosa is known for its persistence in infections due largely to its numerous means of antimicrobic resistance, one of which is its ability to form biofilms. This organism has been placed on the World Health Organization list of Priority Pathogens for Research and Development of New Antibiotics at the critical level for many reasons, that includes its high mortality, healthcare burden, prevalence of resistance, and treatability. P. aeruginosa is resistant to many antibiotics; however, >70% of P. aeruginosa are susceptible to ciprofloxacin. For these reasons, the purpose of the current study was to establish antimicrobic levels of ciprofloxacin effective against P. aeruginosa. To accomplish this purpose, antimicrobic levels of bacteria in biofilms and those not associated with a biofilm (planktonic) need separate methods of testing. For planktonic bacteria, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) are performed, whereas other methods are used for biofilm-associated bacteria. To initiate inhibition studies, a model system was identified of ciprofloxacin effect on standardized strains of P. aeruginosa (ATCC strains 10145, 27853, 1744, CRM-9027, 9721). These strains were used to establish ciprofloxacin effect, in terms of MIC and MBC levels, on planktonic bacteria. Results indicate that MIC and MBC levels of these strains are in the same range as reported values of P. aeruginosa. These results establish ciprofloxacin efficacy of growth inhibition for each ATCC strain of planktonic P. aeruginosa and will serve as baseline results for future studies, such as effect on biofilm-associated bacteria and combination antimicrobic treatments. © FASEB.