in this issue of critical care , cuthbertson and colleagues report   the views of 141 intensive care and infection control specialists from four countries on the potential utility , risks and research opportunities of selective digestive decontamination ( sdd ) . using structured interviews , a delphi process , and a theoretical behavioural domains framework , they determined the extent of consensus and perceived importance of specific issues relating to sdd . respondents demonstrated substantial equipoise on risks and benefits of sdd combined with moderate agreement on concerns that sdd might contribute to antimicrobial resistance . there was uncertainty about the generalisability of sdd research to local context or to all patient groups , and moderately strong support for participating in a national randomised controlled trial of sdd despite a common view that sdd was not a high clinical priority , presumably related to the reported use of other strategies to minimise healthcare - associated infections and ventilator - associated pneumonia ( vap ) . sdd is unique amongst intensive care interventions in having the largest and most consistent evidence base for benefit in terms of minimising secondary infections and reducing mortality . since the initial publications by stoutenbeek and van saene in 1983 and 1984   describing sdd in mechanically ventilated trauma patients , there have been at least 65 randomised controlled trials and 12 meta - analyses involving around 15,000 patients . no other intervention approaches this weight of evidence , and yet expert opinion frequently disregards the technique . sdd was omitted from the first consensus statement of the surviving sepsis campaign ; in the second iteration   sdd was considered but no recommendation made , since expert opinion was shown to be bimodal , demonstrated through the development of the grade grid . in the third iteration in 20122013 , sdd has achieved a level 2b recommendation ( suggested use based on ' moderate evidence ) . the main barrier to sdd relates to the perceived risk of antimicrobial resistance ( or emergence of species not covered by the traditional regimen , such as gram - positive bacteria ) if sdd were to be widely adopted , with the spread of these organisms to the wider environment . the historical over - use of antimicrobials ( intravenous and oral in humans , as growth promoters in animals ) has led to calls for better antimicrobial stewardship , and doctors are now conditioned to minimise frequency and duration of prescriptions . the current survey respondents tended to support the statements that sdd increases antimicrobial resistance and that research to date has not adequately addressed this issue . however , recent studies [ 8 - 12 ] do not support either position ; in the two largest trials , rates of resistance were lower in the sdd group . indeed , it is the conventional use of broad - spectrum intravenous antimicrobials that may promote the emergence of resistance by creating sub - lethal concentrations of antimicrobials in the gut , which then becomes a reservoir of pathogenic aerobic organisms in critically ill patients . this suggests the possibility that sdd may not only be unlikely to promote resistance , but also might actually prevent their emergence . the second barrier relates to local perceptions of performance : the sense that sdd is not required because hospital acquired infections are already well - controlled . the majority of respondents agreed with the statement that ' our vap rates are low. this may be the case if icus are regularly auditing their vap rates . however , as we found in the matching michigan project [ 13 - 15 ] , many icus were surprised to find that their performance in minimising blood stream infections from central venous catheters was not as good as they had expected . the third barrier may be the availability of ' competing non - antimicrobial interventions for preventing vap in mechanically ventilated patients , often combined in ' vap bundles. sdd should be compared with these non - antimicrobial approaches to determine whether there is synergy , or whether the newer techniques can substitute for sdd . the final barrier to sdd might be uncertainty about who should receive it , in what form and with which components . originally promoted as a technique for preventing gut overgrowth with potentially pathogenic gram - negative aerobes by preserving the normal colonic anaerobic flora , it gradually came to be seen primarily as a technique for preventing vap from retrograde oropharyngeal spread of enteric organisms . the classical nosocomial gram - negative pathogens of the 1980s were replaced in the 1990s and 2000s by resistant gram - positives for which sdd was not specifically designed ; in recent years multiply - resistant gram - negatives have returned . this means that the sdd regimen must be adapted to local circumstance - for example , including enteral vancomycin or modifying the anti - gram - negative components . evolving concepts of the mechanism(s ) of action of sdd now re - emphasise the gut as the primary reservoir of pathogenic organisms , and establishment of normal enteric flora as the main therapeutic aim . to this extent sdd and interventions directed at increasing splanchnic blood flow share the same conceptual framework of the gut as ' the largest undrained abscess in the body. one question that the survey did not directly ask is ' what evidence and effect size would encourage you to use sdd as a routine intervention in mechanically ventilated patients? the answer to this is likely to include the absence of emergence of resistance over several years ( at both the individual and environmental level ) and improvements in survival to at least 1  year . it is clear that the research will need to compare sdd against non - antimicrobial interventions directed against vap , and will need to take into account local microbial ecology . a multicentre cluster - randomised trial has been proposed ; this might usefully include a factorial design with blinding of the sdd component to explore potential synergies between interventions rather than a straight head - to - head comparison . such a trial might finally allow us to move from practice based on ' gut instinct to evidence - based medicine .