The impact of an antibiotic cycling program on empirical therapy for gram-negative infections

Antimicrobial-resistant organisms are an emerging problem in the ICU. Therapy cycling empiric antibiotics between various classes may influence bacterial resistance patterns. Understanding the impact of cycling on the appropriate treatment of suspected Gram-negative infections is important.

Data were prospectively collected on patients who were admitted to a 19-bed medical ICU (MICU). A total of 1,172 patients were admitted to the MICU for > 48 h and were evaluated during a 28.5-month period. After 4.5 months of baseline data collection, an antibiotic-cycling protocol was implemented, using four different antibiotic classes with Gram-negative activity that were cycled every 3 to 4 months. Therapy was considered to be inappropriate if the subsequent bacterial isolate was resistant to the empiric drug used.

There were 59 bloodstream infections (BSIs), 17 ventilator-associated pneumonias (VAPs), and 101 urinary tract infections (UTIs) involving Gram-negative bacteria among 139 patients. Fifty-five infections (31%) were due to Gram-negative bacteria resistant to one or more antibiotic agents (BSIs, 18 [30%]; VAPs, 4 [23%]; and UTIs, 33 [33%]). Fifteen patients received inappropriate empiral therapy for 18 resistant Gram-negative infections (BSIs, 7 [39%]; VAPs, 3 [75%]; UTIs, 8 [24%]). Patients receiving inappropriate therapy were more likely to die (10 patients [67%] vs 40 patients [32%], respectively; p < 0.01). There was no difference in the receipt of appropriate empirical antibiotic therapy during the baseline compared to cycling (infectious episodes, 15% vs 10%, respectively; p = 0.4).

Antimicrobial resistance occurred in almost 30% of ICU infections involving Gram-negative bacteria. Antibiotic cycling was not associated with significant changes in the receipt of appropriate empirical antimicrobial therapy for the treatment of ICU infections.