Fluoroquinolones are not a blanket cover for gram-negative bacilli

Abstract

We read with interest the Spanish report on selective intestinal decontamination with fluoroquinolones for the prevention of early bacterial infections after liver transplantation. Although the study was not randomized, the investigators made a significant contribution through their finding of ‘‘a higher relative incidence of infections by NFGNBs [nonfermenting gram-negative bacilli] in patients undergoing FQ-SID [fluoroquinolone selective intestinal decontamination], which probably overrode the protective effect against infections due to enteric bacteria.’’ Their conclusion that other selective intestinal decontamination strategies should be evaluated in this high-risk population is valid. The observations of this Spanish study confirm findings from earlier randomized controlled trials of critically ill patients requiring treatment in the intensive care unit and receiving fluoroquinolones. Belgian and Austrian randomized controlled trials have demonstrated that the classical selective intestinal decontamination regimen of polymyxin and tobramycin does cover nonfermenting gram-negative bacilli (apart from Enterobacteriaceae). The partial efficacy of selective intestinal decontamination with fluoroquinolones can be explained by the observation that fluoroquinolones eradicate gut overgrowth of Enterobacteriaceae after intestinal excretion via the gut mucosa but not the overgrowth of nonfermenting gram-negative bacilli, which is subsequently followed by polyclonality and resistance. In contrast, polymyxin and tobramycin have consistently been shown to achieve the successful eradication of overgrowth of gram-negative bacilli (both fermenting and nonfermenting); that is, surveillance cultures are persistently negative for these potential pathogens. We would like to contribute to the discussion by suggesting the assessment of the selective intestinal decontamination strategy of polymyxin and tobramycin rather than probiotics. Luciano Silvestri, M.D. Miguel A. de la Cal, M.D. Durk F. Zandstra, M.D. Nia Taylor, M.Phil. Hendrick K. F. van Saene, M.D., Ph.D. Anesthesia and Intensive Care Unit Emergency Department Presidio Ospedaliero Gorizia, Italy Intensive Care Unit University Hospital of Getafe Getafe, Spain Intensive Care Unit Onze Lieve Vrouwe Gasthuis Amsterdam, the Netherlands Institute of Ageing and Chronic Disease University of Liverpool Liverpool, United Kingdom