annually , over 4 million patients within the 27 european union member states acquire a nosocomial infection , of whom approximately 37  000 will die as a result .
surgical site infections ( ssis ) are the third most common form of healthcare - associated infection ( hai ) , behind urinary tract ( 27% ) and lower respiratory tract ( 24% ) infections , comprising 17% of cases .
the economic impact of ssis is considerable , with an estimated burden on european healthcare providers of  7 billion in 2008 .
costs are driven predominantly by increased length of hospital stay , estimated to be an average 98-day increase compared to patients not experiencing a ssi . in france ,
it has been estimated that the crude incidence of ssis in france , between 1996 and 2006 , was 154% in patients undergoing either elective or emergency surgery .
the incidence varied depending on the surgical intervention , from 049% for knee prosthesis to 924% for colon surgery . despite an increase in the number of patients undergoing surgical procedures , in particular patients deemed to be at high risk of ssi , such as elderly patients , analysis of temporal trends
has shown that the incidence of nosocomial infections in france has decreased in recent years [ 57 ] .
the reduction in ssi incidence has been attributed , in part , to the successful introduction of active surveillance programmes such as the infection du site opratoire   
rseau alerte investigation surveillance des infections ( iso - raisin ) and incidence des infections du site opratoire ( inciso ) , and the utilization of infection control strategies that have accompanied surveillance [ 4 , 8 ] .
the majority of ssis are preventable ; with a recent usa - based study finding that up to 55% of cases could be avoided .
iso - raisin data from 2007 showed that the most common infectious causative agents of ssis were escherichia coli ( 25% ) , staphylococcus aureus ( 19% ) and pseudomonas aeruginosa ( 10% ) .
of the identified strains , 10% of e. coli isolates were cefotaxime- or ceftriaxone - resistant , 19% of s. aureus were methicillin - resistant and 25% of p. aeruginosa were ceftazidime - resistant .
the frequency of infection by resistant strains of bacteria significantly adds to the burden of ssis as more expensive second - line treatments become necessary .
published data describing the total economic burden of nosocomial infections and ssis in france are currently lacking .
a recent single - centre study found that the mean additional cost per patient experiencing a ssi , taking into account laboratory tests , radiology , surgery , exploratory examinations and antimicrobial agents , was  1814 .
the aim of the present study was to estimate the healthcare burden associated with ssis , both nationally and by region , in france and to explore the potential impact of infection control strategies on the overall clinical and economic burden .
the frequency of 12 preselected surgical procedure categories ( table 1 ) performed in france between 1 january 2010 and 31 december 2010 was quantified through searching of the programme de mdicalisation des systmes d'information ( pmsi ) using 507 appropriate classification commune des actes medicaux ( ccam ) procedure codes , selected from about 8000 codes used to index hospital procedures in france .
the 12 procedure categories were chosen to provide an overview of ssis in france , but do not encompass all surgical procedures performed in 2010 , and therefore the total incidence is underestimated .
pmsi is a comprehensive database of hospital visits in france since all hospitals , both public and private , are legally obliged to report activity for collation , otherwise remuneration for the procedure performed is withheld by the local health authority [ 12 , 13 ] .
it is recommended as an epidemiological tool by the french guidelines for health economic evaluation .
as well as detailing the procedure performed using ccam codes , the database contains details of length of hospital stay , patients details ( such as age ) and an anonymous patient identifier to allow future hospitalizations to be followed . 

table 1.daily cost of hospital care following healthcare - associated infection by surgical procedure , in public and private hospitalssurgical proceduredaily cost of care in public hospitals (  ) daily cost of care in private hospitals (  ) amputation276171coronary artery bypass268163thoracic or abdominal artery surgery219131thoracic or abdominal vein surgery261kidney or pelvic surgery259162caesarean281160colon and rectal surgery240162bowel surgery304177laparoscopic hysterectomy293189intracranial or cerebrospinal fluid surgery263171prostate surgery166150organ transplant290172   =  2009 euros .
daily cost of hospital care following healthcare - associated infection by surgical procedure , in public and private hospitals having identified patients undergoing surgical procedures in france , the incidence of ssis was examined by inspection of patients history subsequent to surgery for the classification statistique internationale des maladies et des problmes de sant connexes ( icd-10 ) codes relating to infection , namely t814 ( infection following a therapeutic or diagnostic procedure , not classified elsewhere ) , l02 ( cutaneous abscess , furuncle , carbuncle ) , and y95 ( nosocomial infection ) .
since these codes are not specific to infection of the surgical site , data shown is for hai incidence following surgery .
daily costs of care were calculated for both public and private hospitals based on resource use and cost data from the 2009 echelle nationale de cots  mthodologie commune ( encc ) .
the encc provides costs of care , taking into account costs of a range of factors , including medical professionals , drug costs , and running costs of the medical unit ( e.g. cleaning and laundry ) .
it is possible to evaluate daily physician costs for public hospitals , but this is not the case for private hospitals since physicians are reimbursed per ccam procedure performed rather than per day of care administered , and therefore physician costs are captured in public , but not private , hospitals . in this analysis only costs allocated to the days of stay following surgical procedures were included .
the mean daily cost of care , in 2009 euros (  ) , following each category of surgical procedure is summarized in table 1 .
having collected data on the length of stay in patients with and without hai , a health economic model was constructed to evaluate cost differences between the infection control scenarios .
a bespoke model was coded , with sqlite and adobe air used to manage the database and present the results .
a 1-year time horizon was used with outcomes evaluated from a hospital perspective . in this model hai incidence
could be varied to examine the clinical and economic impact of infection control interventions used .
model inputs were length of stay associated with each procedure with and without hai , daily cost of hospital care following each procedure , and hai incidence following each procedure .
the model reported outputs of number of hospital stays , number of hospital days of care , and cost of care . as well as examining the burden at current rates of infection ,
three scenario analyses were performed in which hai incidence was varied . in the first scenario hai incidence
this was based on a recent study of the use of triclosan antibacterial sutures , which found that ssi incidence was reduced by 8% ( 7% vs. 15% ) compared to the control arm in which conventional sutures were used . to examine the impact of less focused approaches that could be used to reduce ssis , scenarios with 20% and 30% reduction in incidence were also analysed .
these were based on the upper and lower limits of an estimate of the number of preventable nosocomial infections , made by the european centre for disease prevention and control .
statistical analysis was conducted to examine differences between clinical outcomes in patients experiencing hai and those not experiencing hai , based on the data collected from pmsi .
hypothesis testing of the difference between normally distributed variables was performed using  tests , while mann 
normality tests , to determine whether the data were well modelled by a normal distribution , were performed using kolmogorov 
the pmsi data showed that of 520  715 selected surgical procedures performed between 1 january 2010 and 31 december 2010 , 30% resulted in infection ( table 2 ) .
frequency of hai was correlated with age , with 439% of cases occurring in patients aged 70 years , while only 151% of cases involved patients aged < 50 years
the frequency of hai also varied with the type of surgery performed ( table 3 ) .
of the selected surgical procedures , the group with the highest incidence of hai was organ transplant , with 131% of surgeries resulting in hai .
caesarean section had the lowest incidence of hai , with only 01% of procedures being followed by infection .
the clinical burden of hai was greatest following colon and bowel surgery , comprising 491% and 220% , respectively , of the total hai cases .
it was found that the highest incidence of infection was in martinique ( 51% ) and the lowest in french guiana ( 07% ) . of the mainland
french regions , the highest incidence was found in languedoc - roussillon ( 42% ) and the lowest incidence in alsace ( 22% ) .
however , when corrected for case mix it was found that incidence rates were similar across regions .
this suggests that differences found between regions were due to the number of high - risk procedures performed , rather than other factors influencing hai incidence .
the incidence rates in public and private hospitals showed minimal variation , with 29% and 31% of procedures resulting in hai , respectively .
incidence rates by procedure were also found to be comparable for public and private hospitals . 

2.incidence of healthcare - associated infection ( hai ) following surgery in the 27 regions of france . 

table 2.summary of episodes of hospital care included in the analysis ( with and without hai)without haiwith haitotalnumber of procedures505  19515  520520  715median length of stay ( days)7227number of deaths10  326129311  619hai , healthcare - associated infection . 

table 3.burden of hai by proceduresurgical procedurenumber of procedures performedprocedures resulting in hai ( % ) contribution to the total burden of hai following surgery ( % ) mean length of stay without hai ( days)mean length of stay with hai ( days)mortality rate without hai ( % ) mortality rate with hai ( % ) amputation24  759548617355798coronary artery bypass18  541354114313695thoracic or abdominal artery surgery30  1454179133563143thoracic or abdominal vein surgery35  978030732902104kidney or pelvic surgery20  619304011241369caesarean170  34901157130004colon and rectal surgery93  4308249114294581bowel surgery31  533108220173785124laparoscopic hysterectomy69  27110436190230intracranial or cerebrospinal fluid surgery646565272250131160prostate surgery32  86533699200323organ transplant1742131154262120127total520  7153010014322083hai , healthcare - associated infection.some procedures were classified as more than one type of surgery .
incidence of healthcare - associated infection ( hai ) following surgery in the 27 regions of france .
summary of episodes of hospital care included in the analysis ( with and without hai ) hai , healthcare - associated infection .
the mortality rate in patients experiencing a hai was 83% , compared to 20% in patients who did not ( p  <  0001 ) , corresponding to a 415-fold relative increase ( table 3 ) . the largest increase in mortality rate was seen in the thoracic or abdominal vein and thoracic or abdominal artery surgery groups , where mortality rates increased over 50-fold , from 02% to 104% , and 23-fold , from 63% to 143% , respectively .
length of hospital stay was found to be non - normally distributed ( kolmogorov  smirnov d  =  0253 , p  <  001 ) .
patients experiencing hai had a threefold longer hospital stay than those who did not , with median length of stay increasing from 7 days to 22 days ( p  <  0001 ) .
when mean length of hospital stay following each procedure was evaluated , it was found that hai was associated with at least a twofold longer stay following all procedures ( table 3 ) .
of particular note was the almost tenfold increase following thoracic or abdominal vein surgery , with mean length of stay increasing from 3 days to 29 days following the procedure if hai occurred .
the health economic modelling analysis suggested that in 2010 , hais led to an additional cost to public and private hospitals of  43  019  936 and  14  872  779 , respectively ( table 4 ) .
this difference was driven not by the rate of infection , since incidence rates were found to be comparable , but by the increased number of procedures performed in public hospitals and the increased daily cost of care .
a total of 86  861 more procedures were performed in public hospitals , resulting in 1856 further hais .
the daily cost of care was found to be significantly higher in public hospitals for all procedures , ranging from  122 per day increase for care following intracranial surgery (  293 vs.  171 ) to  88 per day increase following thoracic and abdominal artery surgery (  219 vs.  131 ) .
this was , at least in part , driven by the exclusion of physicians costs in the private sector . 

table 4.additional length of hospital stay and additional costs associated with healthcare - associated infection following surgery for public and private hospitals in francesurgical procedurepublic hospitalsprivate hospitalsadditional length of hospital stay ( days)additional cost (  ) additional cost per procedure resulting in hai (  ) additional length of hospital stay ( days)additional cost (  ) additional cost per procedure resulting in hai (  ) amputation14  0953  890  220496868141  165  1943078coronary artery bypass13  1663  528  488455684771  381  7512771thoracic or abdominal artery surgery905198  195481829238  2522882thoracic or abdominal vein surgery3297547  3024316kidney or pelvic surgery62  05216  195  5723654415776  735  4742268caesarean40  43910  473  701155416  6322  661  120960colon and rectal surgery48511  363  13142152319375  6782430bowel surgery90102  162  4004800594105  1383540laparoscopic hysterectomy48081  461  63239523096585  1442457intracranial or cerebrospinal fluid surgery34781  019  054849773341  254  1144959prostate
surgery63471  669  26128933133469  9501650organ transplant1762510  9805800587100  9643440total164  21043  019 
93690  85514  872  779hai , healthcare - associated infection.  =  2009 euros .
additional length of hospital stay and additional costs associated with healthcare - associated infection following surgery for public and private hospitals in france hai , healthcare - associated infection .
the largest cost burden was that of hai following kidney or pelvic surgery , costing public hospitals  16  195  572 per year and private hospitals  6  735  474 per year .
an increased number of patients experienced hai in public hospitals , despite similar rates of infection ( 3% in both ) , due to the increased number of procedures performed in public hospitals ( 12  365 in public hospitals vs. 8283 in private hospitals ) .
furthermore , daily costs of care following kidney or pelvic surgery were  99 higher in public hospitals than in private hospitals .
expenditure following kidney or pelvic surgery equated to 38% and 45% , in public and private hospitals , respectively , of additional expenditure as a result of hai .
hais had a particularly large cost burden following caesarean (  13  134  821 ) , amputation (  5  055  414 ) and coronary artery surgery (  4  910  239 ) , comprising 40% of additional expenditure , across public and private hospitals , between these three procedures . an 8% reduction in hai incidence , based on a recent study into the reduction in ssis associated with the use of triclosan antibacterial sutures   was predicted to result in a saving of 20  205 hospital days per year , across both public and private hospitals , resulting in annual cost savings of  3  406  520 in public hospitals and  1  178  999 in private hospitals .
the bulk of the cost savings came from reduced cost of hai following kidney or pelvic surgery , with public hospitals saving  1  294  299 per year and private hospitals saving  537  516 per year , 40% of total savings ( figs 3 , 4 ) . 

3.cost saving by reducing the incidence of healthcare - associated infections ( hais ) following surgery by 8% , 20% and 30% in public hospitals .
4.cost saving by reducing the incidence of healthcare - associated infections ( hais ) following surgery by 8% , 20% and 30% in private hospitals .
cost saving by reducing the incidence of healthcare - associated infections ( hais ) following surgery by 8% , 20% and 30% in public hospitals .
cost saving by reducing the incidence of healthcare - associated infections ( hais ) following surgery by 8% , 20% and 30% in private hospitals .
the analysis in which a 20% reduction in hai incidence was applied , based on the lower limit of an estimate of the number of preventable nosocomial infections by the european centre for disease prevention and control   suggested that 3185 hai cases could be avoided annually , resulting in 50  871 hospital days saved .
this was made up of 32  758 days in public hospitals and 18  113 days in private hospitals .
cost savings of  8  583  202 per year and  2  964  855 per year could be made in public and private hospitals , respectively ( figs 3 , 4 ) .
healthcare spending as a result of hais was reduced from  57  892  715 to  46  344  658 .
when a 30% reduction in hai incidence was applied , based on the upper limit of a european centre for disease prevention and control estimate of the proportion of nosocomial infections that could be prevented , analysis suggested that 76  373 hospital days per year could be saved as a result of 4781 hai cases being avoided .
cost savings of  12  880  036 per year could be made in public hospitals , and  4  454  660 per year in private hospitals ( figs 3 , 4 ) .
this saving of  17  334  696 represents a 30% reduction in healthcare spending as a result of hais .
the present study has quantified part of the considerable clinical and economic burden of ssis on the french healthcare system , where about 3% of the included surgical procedures resulted in infection .
the incidence of hai following surgery increased with patients age and varied depending on the surgical procedure performed .
included hais led to a 415-fold increase in post - surgery mortality , a threefold increase in length of hospital stay and an annual cost burden of  57  892  715 .
the current analysis underestimates the total burden of ssis on the french health economy for two reasons .
first , only a predefined set of surgical procedures were included in the analysis , not all the surgical procedures performed in france in 2010 .
furthermore , the icd-10 codes used captured only infections reported during the initial hospital stay . since not all ssi cases were identified in this analysis , the clinical and economic estimates are conservative and the burden to the french health economy is expected to be greater .
scenario analysis suggests that reduction in hai incidence by 8% , 20% and 30% will result in savings of  4  588  519 ,  11  548  057 and  17  334  696 , respectively .
these are substantial cost savings , made predominantly in public hospitals due to the increased number of surgical procedures performed and the increased daily cost of care .
the frequency of surgical procedures involving patients at high risk of ssi is increasing , and therefore the use of infection control strategies is likely to become increasingly important in the future .
one of the major strengths of the present study is the robust epidemiological data on which the health economic model is based .
pmsi provides a detailed account of hospital stays and allows the number of procedures and treatments performed in a given time - frame to be accurately determined .
furthermore , the age of the patient and the post - operative clinical consequences can be accurately assessed using the anonymous patient identifier . in this analysis ,
507 ccam codes relating to preselected surgical procedures were used to identify treatments of interest , giving a comprehensive list of procedures performed , while the use of icd-10 codes relating to hai allows accurate quantification of hai incidence following surgery during the initial hospital stay . the bespoke health economic model developed for this analysis , based on these data , may be a valuable tool for future economic evaluations of infection control strategies and interventions in the french setting .
an assumption of this analysis is that the daily cost of care following surgical procedures is the same in patients experiencing hai and those not experiencing hai
. it may be the case that patients with hai would require not only a longer period of care , taken into account through the increased length of hospital stay , but also require more intense and expensive care during hospitalization .
this may be through increased volume of diagnostic tests to identify the causative pathogen , intensified antimicrobial treatments ( including more expensive second - line therapy if the causative agent is resistant to first - line treatments ) , and increased nursing staff time . given this conservative assumption , cost savings reducing ssi incidence may be greater than those suggested in this analysis .
an important limitation of the present analysis is that it does not capture the costs of achieving 8% , 20% and 30% reductions in hai incidence following surgery .
however , the analysis does show the threshold at which an intervention to achieve this reduction will be cost saving .
for example , if an infection control strategy resulting in an 8% reduction in hai could be introduced in public hospitals at an annual cost of less than  3  400  000 , healthcare providers would have reduced expenditure . while including the costs of interventions to achieve reductions in hai following surgery was beyond the scope of the present analysis , the potential for significant cost savings as a result of interventions that reduce hai incidence following surgery is worthy of further investigation
. the risk of ssi is dependent on the type and virulence of the infecting bacteria , and the immunological status of the host .
factors increasing the susceptibility of patients to ssi include advanced age , poor nutritional status , diabetes , smoking , obesity , infection remote to the surgical site and lengthy preoperative hospitalization . due to the increased resource use and cost of hospital care for patients experiencing a ssi , infection control strategies to reduce the incidence are important , particularly in patients at the highest risk . while it is acknowledged that not all ssis can be prevented , evidence suggests that the current level of incidence can be reduced [ 13 ] .
the majority of ssis occur at superficial sites around foreign material left in the wound .
one potential avenue for improving infection control is in the choice of sutures , which are known to provide a focal point for bacterial colonization , act as a vehicle to transport bacteria into the wound and afford a repository for bacteria in the suture knot .
use of triclosan - coated sutures reduces ssis by preventing bacterial colonization of the wound around the suture , due to the presence of an antimicrobial .
triclosan is a broad - spectrum antimicrobial agent , possessing mostly antibacterial , but also some antifungal and antiviral properties .
use of triclosan - coated sutures has been shown to reduce ssi incidence by 8% ( 7% vs. 15% ) in a comparison with conventional sutures .
examination of this benefit in the present scenario analysis suggests that this reduction in ssi incidence may have a substantial impact on both the clinical and economic burden , reducing the number of hospital stays , length of stay and cost of care by as much as  4  588  519 per year .
further economic evaluation of the benefit of introduction of infection control interventions such as triclosan antibacterial sutures in the french setting may be warranted based on these observations .
the world health organization and the centre for disease control and prevention have issued guidelines detailing pre- , peri- and post - operative infection control actions that can be used to reduce the incidence of ssis [ 17 , 18 ] .
preoperatively patients should be treated to resolve infections remote from the surgical site and appropriate disinfection of the skin at the surgical site should take place , with shaving only performed if absolutely necessary [ 17 , 18 ] .
if the patient is considered at high risk of ssi , a prophylactic dose of an appropriate antimicrobial should be administered , ideally intravenously , at a time to establish a bactericidal concentration at the operational site [ 17 , 18 ] .
surgical team members should follow good practice guidelines for hand washing and preoperative aseptic procedures [ 17 , 18 ] . during the surgical procedure ,
surgical team members should use surgical masks , caps , gowns , gloves and drapes and replace these items when they become soiled [ 17 , 18 ] .
the operating theatre should be cleaned using a hospital - approved disinfectant and good practice used to maintain sterility of surgical instruments [ 17 , 18 ] .
air within the operating theatre should be changed at least 15 times per hour , with three of these being with fresh air , and filtering should take place using an appropriate filter [ 17 , 18 ] . in the post - operative period ,
sterile dressing should be used and sterile techniques should be adhered to during dressing changes [ 17 , 18 ] .
patients should undergo post - operative surveillance , including post - discharge if required , with any ssi assessed and reported appropriately [ 17 , 18 ] .
ssi rates should then be conveyed to surgical team members [ 17 , 18 ] .
the present study used conservative estimates of an overall reduction in incidence of 2030% in ssis .
the analyses suggest that substantial reductions in healthcare expenditure could occur if ssi incidence is reduced . with greater decreases in ssi incidence larger cost savings
can be expected , as the required number of hospital days of care will be reduced beyond the levels estimated in this study .
the present study has quantified the substantial economic burden that ssis following a limited selection of procedures place on the healthcare system in france to be  57892715 per year
. however , our analysis was conservative and the total burden is expected to be greater , both clinically and economically . new infection control interventions which reduce ssi incidence have the potential to lessen the clinical and economic burden , providing valuable cost savings to healthcare providers and should be the subject of future health economic evaluations .
ludovic lamarsalle is an employee of heva , and barnaby hunt and william valentine are employees of ossian health economics and communications .
 summaryover 4 million patients suffer nosocomial infections annually in the european union . 
 this study aimed to estimate the healthcare burden associated with healthcare - associated infections ( hais ) following surgery in france , and explore the potential impact of infection control strategies and interventions on the clinical and economic burden of disease . 
 data on the frequency of hais were gathered from the 2010 programme de mdicalisation des systmes d'information ( pmsi ) , and cost data were taken from the 2009 echelle nationale de cots  mthodologie commune ( encc ) . it was estimated that 3% of surgical procedures performed in 2010 in france resulted in infection , resulting in an annual cost of  57  892  715 . 
 patients experiencing a hai had a significantly increased mortality risk ( 415-fold ) and an increased length of hospital stay ( threefold ) . 
 scenario analysis in which hai incidence following surgery was reduced by 8% ( based on a study of the effectiveness of triclosan - coated sutures ) , suggested that , annually , 20  205 hospital days and  4  588  519 could be saved . 
 analyses of 20% and 30% reductions in incidence ( based on an estimate of the number of preventable nosocomial infections ) suggested that annual savings of  11  548  057 and  17  334  696 , respectively , could be made . 
 new infection control interventions which reduce hai incidence during hospitalization for surgery have the potential to provide valuable cost savings to healthcare providers . 
INTRODUCTION
METHODS
RESULTS
DISCUSSION
DECLARATION OF INTEREST