Antibiotic susceptibility trend before and after long-term use of selective digestive decontamination: a 16 year ecological study

OBJECTIVES: The aim of this study was to compare antimicrobial susceptibility rates in a Spanish ICU before and after the introduction of selective digestive decontamination (SDD) and also to compare these with susceptibility data from other Spanish ICUs without SDD. METHODS: We performed a retrospective study in the ICU of the University Hospital of Alava, where SDD was implemented in 2002. The SDD protocol consisted of a 2% mixture of gentamicin, colistin and amphotericin B applied on the buccal mucosa and a suspension of the same drugs in the gastrointestinal tract; additionally, for the first 3 days, systemic ceftriaxone was administered. From 1998 to 2013 we analysed the susceptibility rates for 48 antimicrobial/organism combinations. Interrupted time series using a linear dynamic model with SDD as an intervention was used. Data from other ICUs were obtained from the ENVIN-HELICS national registry. RESULTS: Only amoxicillin/clavulanic acid against Escherichia coli and Proteus mirabilis, and a high concentration of gentamicin against Enterococcus faecalis, resulted in a significant decrease in the susceptibility rate after the implementation of SDD, with a drop of 20%, 27% and 32%, respectively. Compared with other Spanish ICUs without SDD, the susceptibility rate was higher in the ICU of our hospital in most cases. When it was lower, differences were <10%, except for a high concentration of streptomycin against Enterococcus faecium, for which the difference was 19%. CONCLUSIONS: No relevant changes in the overall susceptibility rate after the implementation of SDD were detected. Susceptibility rates were not lower than those in the Spanish ICUs without SDD.