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Seddon MM, Bookstaver PB, Justo JA, et al. Role of early de-escalation of antimicrobial therapy on risk of Clostridioides difficile infection following Enterobacteriaceae bloodstream infections [published online October 12, 2018]. Clin Infect Dis. doi: 10.1093/cid/ciy863. Dellinger RP, Levy MM, Rhodes A, et al; Surviving Sepsis Campaign Guidelines Committee including The Pediatric Subgroup. Surviving Sepsis Campaign: international guidelines for management of severe sepsis and septic shock, 2012. Intensive Care Med. 2013;39(2):165-228. doi: 10.1097/CCM.0b013e31827e83af. Kumar A, Roberts D, Wood KE et al. Duration of hypotension prior to initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock. Crit Care Med. 2006;34(6):1589-1596. doi: 10.1097/01.CCM.0000217961.75225.E9. Kadri SS, Adjemian J, Lai YL, Spaulding AB, et al; National Institutes of Health Antimicrobial Resistance Outcomes Research Initiative (NIH–ARORI). Difficult-to-treat resistance in gram-negative bacteremia at 173 US hospitals: retrospective cohort analysis of prevalence, predictors, and outcome of resistance to all first-line agents. Clin Infect Dis. 2018;67(12);1803-1814. doi: 10.1093/cid/ciy378. Klevens RM, Edwards JR, Gaynes RP; National Nosocomial Infections Surveillance System. The impact of antimicrobial-resistant, healthcare-associated infections on mortality in the United States. Clin Infect Dis. 2008;47(7):927- 930. doi: 10.1086/591698. Hammer KL, Justo JA, Bookstaver PB, Kohn J, Albrecht H, Al-Hasan MN. Differential effect of prior β-lactams and fluoroquinolones on the risk of bloodstream infections secondary to Pseudomonas aeruginosa. Diagn Microbiol Infect Dis. 2017;87(1): 87-91. doi: 10.1016/j.diagmicrobio.2016.09.017. McDonald LC, Gerding DN, Johnson S, et al. Clinical practice guidelines for Clostridium difficile infection in adults and children: 2017 update by the Infectious Diseases Society of America (IDSA) and Society of Healthcare Epidemiology of America (SHEA). Clin Infect Dis. 2018;66(7):e1-e48. doi: 10.1093/cid/cix1085. Tartof SY, Rieg GK, Wei R, Tseng HF, Jacobsen SJ, Yu KC. A comprehensive assessment across the healthcare continuum: Risk of hospital-associated Clostridium difficile infection due to outpatient and inpatient antibiotic exposure. Infect Control Hosp Epidemiol. 2015;36(12):1409-1416. doi: 10.1017/ice.2015.220. Kim SC, Seo MY, Lee JY, et al. Advanced chronic kidney disease: a strong risk factor for Clostridium difficile infection. Korean J Intern Med. 2016;31(1):125-33. doi: 10.3904/kjim.2016.31.1.125 . Buehler SS, Madison B, Snyder SR, et al. Effectiveness of practices to increase timeliness of providing targeted therapy for inpatients with bloodstream infections: a laboratory medicine best practices systematic review and meta-analysis. Clin Microbiol Rev. 2016;29(1):59-103. doi: 10.1128/CMR.00053-14.

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A novel study from Seddon and colleagues adds to the body of evidence that supports what antimicrobial stewardship programs are so often challenged to do, early de-escalation.The study’s investigators looked at the independent risk factors of empiric antipseudomonal β-lactam (APBL) therapy for patients with Enterobacteriaceae bloodstream infections who received more than 48 hours of therapy compared with those who received less and found a 3-fold lower incidence of Clostridium difficile infection in patients who received less than 48 hours of APBL therapy.With each hour that passes after receiving noneffective therapy, patients with sepsis are at increased risk of mortality.As a result, empiric treatment for the condition often includes APBL therapy. With the increased threat of antimicrobial resistance, however, clinicians are growing concerned over the development of difficult-to-treat gram-negative bacteremia, and so the initial selection of the appropriate, targeted antibiotic is imperative.Furthermore, excessive antimicrobial coverage brings additional risks, such as C difficile infection.Seddon and colleagues challenged the practice of broad-spectrum antipseudomonal coverage up front for those patients without risk factors, referencing another recent study completed at their center. The results from that study demonstrated only 1% prevalence of Pseudomonas aeruginosa bloodstream infections in community-onset, immunocompetent patients who have not received prior antimicrobial use within 3 months.In addition, the investigators assessed the risk of antimicrobial exposure and early de-escalation of APBL therapy at 48 hours on the rate of C difficile infection.The retrospective cohort study included 951 adult patients with gram-negative bloodstream infections. Data were collected for 54 months. Not all non-Enterobacteriaceae bloodstream cases (n = 78) were included, as the authors stated they lacked the possibility of de-escalation. Those patients who were discharged, transferred, or died were also excluded from the results (n = 56). Additionally, the investigators excluded those patients with recent (within a year) or concurrent C difficile infection (developed within 24 hours of blood culture collection).A total of 808 patients with a first episode monomicrobial Enterobacteriaceae bloodstream infection who received an APBL were included in the study. Nearly half of the patients (n = 414) received more than 48 hours of APBL versus the patients (n = 394) who received less than 48 hours of similar therapy. (An APBL-antimicrobial agent was described as the following: piperacillin/tazobactam, ceftazidime, cefepime, imipenem/cilastatin, meropenem, and aztreonam.)C difficile infection was determined by positive C difficile toxin B polymerase chain reaction. To overcome the highly sensitive test and account for clinical C difficile infection incidence, the 2 institutions in the study were consistent with their hospital policies related to the diagnosis and testing of C difficile infection. Stool samples must have conformed to container in order to be assessed or otherwise were rejected. Patients who received laxatives within 48 hours of stool collection were excluded. Patients were not routinely screened for C difficile infection.The investigators looked at therapy from the index visit to any subsequent admissions within 90 days of bloodstream infection. Baseline characteristics of those who received more than 48 hours of APBL were that they were slightly younger, more likely male, and more likely to have received antimicrobials within of bloodstream infections (time frame not defined); a higher Charlson Comorbidity Index score; a longer hospital length of stay (HLOS) prior to bloodstream infection; a higher Pitt Bacteremia Score; and higher incidence of intra-abdominal source.Of interest, the isolates were reported to be Escherichia coli (56%), Klebsiella species (21%), Proteus mirabilis (7%), Enterobacter species (7%), Serratia species (4%), Citrobacter species (1%), Salmonella species (1%), and other Enterobacteriaceae (2%). Most infections were from the urinary tract (56%).The investigators also found that HLOS following bloodstream infection and total exposure to antimicrobials was longer in those who received more than 48 hours of APBL (11 days vs 7 days; P