in this commentary we discuss the study of scannapieco and colleagues   published in a recent issue of critical care . ventilator - associated pneumonia ( vap ) frequently occurs in icus , with reported incidences ranging from 9% to 27% . it is a leading cause of morbidity and , possibly , of mortality . as a result , colonization of the upper respiratory tract generally precedes the occurrence of vap , most probably because of a reduced capacity to clear pathogens and/or an increased adherence of micro - organisms to the respiratory tract . prevention of oropharyngeal colonization has been achieved with topically applied non - absorbable antibiotics ( referred to as selective oropharyngeal decontamination with antibiotics ( ab - sod ) ) or with topically applied chlorhexidine gluconate ( chx - sod ) . ab - sod was associated with reduced incidences of vap in various studies [ 4 - 6 ] , and recently also with a better 28-day survival in a large dutch multi - center study . in that study , ab - sod was equally effective in improving patient outcome as selective decontamination of the digestive tract ( sdd ) , which combines ab - sod with intestinal decontamination and 4 days of intravenous cefotaxim . the occurrence of resistance as a result of ab - sod or sdd , however , remains of concern , especially in countries with endemic levels of antimicrobial - resistant bacteria ( amrb ) . therefore , simply replacing antibiotics with antiseptics for oral decontamination might offer an effective and safe measure for icu patients , even in settings with high levels of amrb . indeed , chx - sod appeared effective in reducing vap incidence in several studies [ 8 - 13 ] . however , the regimens used were not always carefully described and concentrations and dosing frequencies varied from 0.12% chx twice daily to 2% chx four times a day . in addition , patient populations varied widely : from mixed icu populations   to surgical icu patients   and patients undergoing cardiac surgery . furthermore , nasal application of chx was used in one study   and chx was combined with colistine in another , and in one study effects were compared to historic controls . moreover , all individual studies published so far have been underpowered to demonstrate effects of chx - sod on patient survival . in a recently published systematic review and meta - analysis , chx - sod was associated with a significant reduction in vap incidence of 44% , although the studies were very heterogeneous , which precludes firm conclusions about its protective effects . no reductions in overall mortality , duration of mechanical ventilation or length of stay could be demonstrated . in their article , scannapieco and colleagues   aimed to determine the optimal frequency of chx - sod to prevent vap in trauma icu patients . the study contains a control group ( 49 patients ) and two intervention groups receiving chx 0.12% either once ( 47 patients ) or twice daily ( 50 patients ) . they conclude that the number of staphylococcus aureus in dental plaque was reduced in both intervention groups , but no significant reductions were observed in the total number of respiratory pathogens or incidence of vap . estimated reductions in colonization were 25% and 30% in the ' twice - daily ' and ' once - daily ' groups , respectively . the odds ratio for developing vap was 0.54 ( 95% confidence interval 0.23 to 1.25 ) for patients receiving chx - sod , which is remarkably similar to the pooled estimate from the most recent meta - analysis . although this may suggest a beneficial effect of chx - sod , it can not be demonstrated by a study of this sample size . in summary , the evidence that both ab - sod and chx - sod reduce vap incidence in icu patients is accumulating . the optimal frequency and concentration for chx - sod remains to be demonstrated . from scannapieco and colleagues ' study we can conclude that twice daily is not necessarily better than once daily , but maybe a four times daily regimen with 2% instead of 0.12% chx does make a difference . what we need now are well - designed and adequately powered studies to evaluate the effects of these measures on length of icu stay and survival . if these effects were demonstrated , chx - sod would offer a very cheap and ( ecologically ) safe infection prevention measure in patient populations increasingly suffering from infections caused by amrb . ab : antibiotics ; amrb : antimicrobial - resistant bacteria ; chx : chlorhexidine ; sdd : selective decontamination of the digestive tract ; sod : selective oropharyngeal decontamination ; vap : ventilator - associated pneumonia .
ventilator - associated pneumonia ( vap ) is a common cause of morbidity , antibiotic use , increased length of stay and , possibly , increased mortality in icu patients . 
 colonization of the oropharyngeal cavity with potentially pathogenic micro - organisms is instrumental in the pathogenesis of vap , and selective oropharyngeal decontamination ( sod ) with antibiotics ( ab - sod ) or antiseptics , such as chlorhexidine gluconate ( chx - sod ) , has been associated with reduced incidences of vap . in a recent issue of critical care scannapieco and 
 colleagues investigated differences in oropharyngeal colonization between mechanically ventilated patients receiving oropharyngeal decontamination with 0.12% chx - sod either once or twice daily compared to placebo . 
 chx - sod was associated with a reduction in staphylococcus aureus colonization , but the study was underpowered to demonstrate a reduction in vap incidence . 
 we urgently need well - designed and adequately powered studies to evaluate the potential benefits of chx - sod on patient outcome in icus .