There’s no way to avoid the news of a growing concern for drug-resistant infections. In both life-threatening and relatively superficial infections, the ability to successfully treat microbial infections with antimicrobials is decreasing. Our only recourse is to use the drugs we have carefully while researchers hunt for new drugs that must pass the stringent FDA guidelines before they can be used clinically. But here comes a bit of good news among all the doom-and-gloom: meticulous drug management programs can have a positive effect on drug-resistant infections.
Support for the decrease in drug-resistant infections comes from a study performed at St. Joseph’s Health Center Hospital in Toronto, Ontario. A team of clinical scientists led by Larissa Matukas studied the effects of antibiotic stewardship surrounding the use of ciprofloxacin, a fluoroquinolone that interferes with DNA topoisomerases, to treat bacterial infections caused by Esherichia coli or Pseudomonas aeruginosa. Their results are now available in the Journal of Clinical Microbiology.
The Infectious Disease Society of America (IDSA) suggests cascade reporting of drug susceptibility, which is the practice of reporting susceptibility for the least expensive drug to which the microbe is susceptible. If three drugs A, B, and C are all tested in order of drug cost, and the isolate is susceptible to A, only that measurement is reported, because it is the cheapest. There are several controversial issues surrounding this practice and the team in this study hoped to find an alternate reporting system targeting fluoroquinolones, with a goal to reduce their use.
To attempt this, the microbiology lab at the hospital changed their susceptibility reporting for infectious isolates. Previously, ciprofloxacin susceptibility was reported regardless of other drug susceptibilities. The policy was changed such that ciprofloxacin susceptibility was reported only if no other susceptibilities were found when testing isolates against a drug panel that included cefazolin, amoxicillin-clavulanate, trimethoprim-sulfamethoxazole, gentamicin, nitrofurantoin, tobramycin, and ciprofloxacin. This selective reporting emphasized susceptibility without immediate concern of drug cost.
After implementing this new reporting strategy, the scientific team saw a drop in ciprofloxacin use, as might be expected if ciprofloxacin susceptibility isn’t reported. The defined daily dose dropped from 87 to 39 per 1000 inpatient days, demonstrating a strong reduction in use of this particular antibiotic. However, the use of amoxicillin-clavulanate increased from 3.1 to 29.8 DDD per 1000 inpatient days, which may represent compensatory usage as clinicians look for an effective drug to treat infections. This would be an important aspect to consider if broadening the scope of reporting to multiple drugs or drug classes.
In addition to measuring drug use, the team tested E. coli and P. aeruginosa isolates for ciprofloxacin susceptibility before and after the reporting change. The drop in ciprofloxacin use correlated with a change in predicted isolate susceptibility. There was no significant change to the level of P. aeruginosa susceptibility throughout the study. Importantly, the rate of drug-resistant E. coli isolates, which had been steadily increasing prior to the new selective reporting strategy, leveled off and showed a trend toward increasing susceptibility (see figure, right).
The change was small and relatively slow, but this small silver lining shows that our behavior concerning antimicrobials can have an effect. In the midst of ‘superbug’ stories and emerging resistance genes, we will need to employ many small gains, such as those observed in this study, to prolong the efficacy of the drugs we have in hand.
-- Julie Wolf