infection control & hospital epidemiology october 2017, vol. 38, no. 10 concise communication


Antibiotic Overuse is a Major Risk Factor for Clostridium difficile Infection in Surgical Patients


James T. Bernatz, MD;1 Nasia Safdar, MD, PhD;2,3 Scott Hetzel, MS;4 Paul A. Anderson, MD, MS1


Clostridium difficile infection (CDI) is associated with increased cost, morbidity, and mortality in postoperative patients. Variable rates of postoperative CDI are reported among 4 surgical specialties during the 30-month study period. Risk factors for CDI include antibiotic use, increased ASA score, and increased admissions in the past year.


Infect Control Hosp Epidemiol 2017;38:1254–1257


Clostridium difficile infection (CDI) following surgical proce- dures is associated with morbidity, mortality, and cost. Length of stay is increased by 1 week if surgery is complicated by a CDI, and mortality has been reported as high as 35% in trauma surgery patients.1,2 Cost of care more than doubles if the postoperative patient contracts CDI.1 Therefore, it is essential to reduce the risk of CDI in surgical patients. Previous studies have reported CDI rates for individual


specialties or after specific procedures with small sample sizes.1,3–7 To our knowledge, there have been no reports of CDI across multiple surgical specialties. Differences across surgical specialties could be due to overall health of the patient population, complexity of surgery, perioperative antibiotic selection, pre- and postoperative exposure to additional anti- biotics, or many other factors. The aims of our study were to determine the incidence of postoperative CDI across four surgical specialties (orthopedic surgery, neurosurgery, trauma surgery, and general surgery) and to examine risk factors for CDI.


methods


This study was conducted at a 592-bed tertiary-care academic center, and we were granted an exemption by the institutional review board. Using the hospital’s quality improvement database, all admissions to 4 hospital units (ie, orthopedic surgery, neurosurgery, trauma surgery, and general surgery) from January 2014 to July 2016 were reviewed. Patients who underwent an inpatient surgical procedure were included. Exclusion criteria included a documented CDI in the 2 months prior to admission or within 72 hours of admission. A case patient was defined as a patient who underwent an inpatient surgical procedure and subsequently developed healthcare-associated CDI (HA-CDI), defined as a positive


PCR for C. difficile toxin gene recorded more than 72 hours after admission and within 12 weeks of discharge. Controls were patients selected from the same group of patients who underwent an inpatient surgical procedure but did not develop HA-CDI. The electronic medical record was used for data extraction. Variables of interest were extracted by a single author.


Statistical Methods


Control patients were matched in triplicate based on age, sex, and admitting department. If more than 3 controls fit the matching criteria for a case, then 3 were chosen at


random. Data analysis included summarizing the cases with means


(±standard deviation [SD]) for normally distributed continuous variables, medians (with interquartile range [IQR]) for nonnormally distributed continuous variables, and frequency (%) for categorical variables. Associations between collected data and subject group were first assessed with univariable mixed-effect logistic regression (MELR) models with matched pair number as a random effect followed by multivariable MELR analyses with a priori defined covariates of body mass index (BMI), American Society of Anesthesio- logists (ASA) classification, and antibiotic use in the previous 6 months. A P value≤.05 was considered significant. R version 3.3 software (R Foundation for Statistical Computing, Vienna, Austria) was used for statistical analyses.


results Incidence


Over the 30-month study period, there were 11,310 admis- sions to the 4 included hospital units during which the patient had an inpatient operation. In 52 cases, the patient had a positive C. difficile polymerase chain reaction (PCR) test recorded more than 72 hours after admission and within 12 weeks of discharge. The incidence rate of hospital-acquired CDI was 0.80 cases per 1,000 patient days. Comparing spe- cialties, trauma surgery had the highest rate of CDI at 9.5 cases per 1,000 admissions (Table 1).


table 1. Incidence of Clostridium difficile infection (CDI) by Hospital Unit


Hospital Unit


Orthopedic surgery 6 Neurosurgery General surgery Trauma surgery


5


30 11


Cases Admissions Ratea OR (95% CI) 4,339


1.4


2,364 3,447 1,160


NOTE. OR, odds ratio; CI, confidence interval. aCases per 1,000 admissions.


Reference


2.1 1.53 (0.37–6.03) 8.7 6.34 (2.59–18.6) 9.5 6.91 (2.34–22.8)


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