Rotation of antimicrobial therapy in the intensive care unit: impact on incidence of ventilator-associated pneumonia caused by antibiotic-resistant Gram-negative bacteria.

The development of antibiotic resistance is associated with high morbidity and mortality, particularly in the intensive care unit (ICU) setting. We evaluated the effect of an antibiotic rotation programme on the incidence of ventilator-associated pneumonia (VAP) caused by antibiotic-resistant Gram-negative bacteria. We conducted a 2-year before-and-after study at two medical-surgical ICUs at two different tertiary referral hospitals. We included all mechanically ventilated patients admitted for > or =48 h who developed VAP. From 1 January through 31 December 2007, a quarterly rotation of antibiotics (piperacillin/tazobactam, fluoroquinolones, carbapenems and cefepime/ceftazidime) for the empirical treatment of VAP was implemented. We analysed the incidence of VAP and the antibiotic resistance patterns of the responsible pathogens in 2006, before (P1) and, in 2007, after (P2) the introduction of the scheduled rotation programme. Overall, there were 79 VAP episodes in P1 and 44 in P2; the mean incidence of VAP was 20.96 cases per 1,000 days of mechanical ventilation (MV) during P1 and 14.97 in P2, with no significant difference between periods on segmented regression analysis. We observed a non-significant reduction of the number of both the poly-microbial (14 [17.7%] in P1 and 5 [10.6%] in P2 [p = 0.32]) and of the antibiotic-resistant Gram-negative bacteria-related VAP (42 [45.2%] in P1 and 16 [34%] in P2 [p = 0.21]). Conversely, the number of VAP caused by Pseudomonas aeruginosa passed from 8.35 per 1,000 days of MV in P1 to 2.33 per 1,000 days of MV in P2 (p = 0.02). No difference in ICU mortality and crude in-hospital mortality between P1 and P2 was noted. Moreover, no significant change of microbial flora isolated through clinical cultures was observed. We were able to conclude that, despite global microbial flora not being affected by such a programme, antibiotic therapy rotation may reduce the incidence of VAP caused by antibiotic-resistant Gram-negative bacteria in the ICU, such as Pseudomonas aeruginosa. The application of this programme may also improve antibiotic susceptibility. However, further studies are needed to confirm our results.