Theoklis E Zaoutis

The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, United States

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Publications (163)700.6 Total impact

  • JAMA. 10/2014;
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    ABSTRACT: Objective. Inappropriate antibiotic prescribing commonly occurs in pediatric outpatients with acute respiratory tract infections. Antimicrobial stewardship programs are recommended for use in the hospital, but less is known about whether and how they will work in the ambulatory setting. Following a successful cluster-randomized trial to improve prescribing for common acute respiratory tract infections using education plus audit and feedback in a large, pediatric primary care network, we sought to explore the perceptions of the intervention and antibiotic overuse among participating clinicians. Methods. We conducted a qualitative study using semistructured interviews with 24 pediatricians from 6 primary care practices who participated in an outpatient antimicrobial stewardship intervention. All interviews were transcribed and analyzed using a modified grounded theory approach. Results. Deep skepticism of the audit and feedback reports emerged. Respondents ignored reports or expressed distrust about them. One respondent admitted to gaming behavior. When asked about antibiotic overuse, respondents recognized it as a problem, but they believed it was driven by the behaviors of nonpediatric physicians. Parent pressure for antibiotics was identified by all respondents as a major barrier to the more judicious use of antibiotics. Respondents reported that they sometimes "caved" to parent pressure for social reasons. Conclusions. To improve the effectiveness and sustainability of outpatient antimicrobial stewardship, it is critical to boost the credibility of audit data, engage primary care pediatricians in recognizing that their behavior contributes to antibiotic overuse, and address parent pressure to prescribe antibiotics.
    10/2014; 35(S3):S69-S78.
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    ABSTRACT: Objective. To compare practice patterns regarding the diagnosis and management of streptococcal pharyngitis across pediatric primary care practices. Design. Retrospective cohort study. Setting. All encounters to 25 pediatric primary care practices sharing an electronic health record. Methods. Streptococcal pharyngitis was defined by an International Classification of Diseases, Ninth Revision code for acute pharyngitis, positive laboratory test, antibiotic prescription, and absence of an alternative bacterial infection. Logistic regression models standardizing for patient-level characteristics were used to compare diagnosis, testing, and broad-spectrum antibiotic treatment for children with pharyngitis across practices. Fixed-effects models and likelihood ratio tests were conducted to analyze within-practice variation. Results. Of 399,793 acute encounters in 1 calendar year, there were 52,658 diagnoses of acute pharyngitis, including 12,445 diagnoses of streptococcal pharyngitis. After excluding encounters by patients with chronic conditions and standardizing for age, sex, insurance type, and race, there was significant variability across and within practices in the diagnosis and testing for streptococcal pharyngitis. Excluding patients with antibiotic allergies or prior antibiotic use, off-guideline antibiotic prescribing for confirmed group A streptococcal pharyngitis ranged from 1% to 33% across practices (P < .001). At the clinician level, 13 of 25 sites demonstrated significant within-practice variability in off-guideline antibiotic prescribing (P ≤ .05). Only 18 of the 222 clinicians in the network accounted for half of all off-guideline antibiotic prescribing. Conclusions. Significant variability in the diagnosis and treatment of pharyngitis exists across and within pediatric practices, which cannot be explained by relevant clinical or demographic factors. Our data support clinician-targeted interventions to improve adherence to prescribing guidelines for this common condition.
    10/2014; 35(S3):S79-S85.
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    ABSTRACT: Community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) has emerged as the most common cause of skin and soft-tissue infections (SSTI) in the United States. A nearly three-fold increase in SSTI visit rates had been documented in the nation's emergency departments (ED). The objective of this study was to determine characteristics associated with ED performance of incision and drainage (I+D) and use of adjuvant antibiotics in the management of skin and soft tissue infections (SSTI).
    The western journal of emergency medicine 07/2014; 15(4):491-8.
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    ABSTRACT: To evaluate clinician adherence to guidelines for documentation of sexual history and screening for sexually transmitted infection (STI)/HIV infection during routine adolescent well visits. Secondary objectives were to determine patient and clinician factors associated with sexual history documentation and STI/HIV testing.
    The Journal of pediatrics. 05/2014;
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    ABSTRACT: We examined the impact of PIDS/IDSA guidelines that recommend ampicillin or amoxicillin for children hospitalized with community-acquired pneumonia. Prescribing of ampicillin/amoxicillin increased following guideline publication, but remains low. Cephalosporin and macrolide prescribing decreased but remains common. Further studies exploring outcomes of and reasons for compliance with guidelines are warranted.
    Clinical Infectious Diseases 01/2014; · 9.37 Impact Factor
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    ABSTRACT: Children with acute myeloid leukemia are at risk for sepsis and organ failure. Outcomes associated with intensive care support have not been studied in a large pediatric acute myeloid leukemia population. Our objective was to determine hospital mortality of pediatric acute myeloid leukemia patients requiring intensive care. Retrospective cohort study of children hospitalized between 1999 and 2010. Use of intensive care was defined by utilization of specific procedures and resources. The primary endpoint was hospital mortality. Forty-three children's hospitals contributing data to the Pediatric Health Information System database. Patients who are newly diagnosed with acute myeloid leukemia and who are 28 days through 18 years old (n = 1,673) hospitalized any time from initial diagnosis through 9 months following diagnosis or until stem cell transplant. A reference cohort of all nononcology pediatric admissions using the same intensive care resources in the same time period (n = 242,192 admissions) was also studied. None. One-third of pediatric patients with acute myeloid leukemia (553 of 1,673) required intensive care during a hospitalization within 9 months of diagnosis. Among intensive care admissions, mortality was higher in the acute myeloid leukemia cohort compared with the nononcology cohort (18.6% vs 6.5%; odds ratio, 3.23; 95% CI, 2.64-3.94). However, when sepsis was present, mortality was not significantly different between cohorts (21.9% vs 19.5%; odds ratio, 1.17; 95% CI, 0.89-1.53). Mortality was consistently higher for each type of organ failure in the acute myeloid leukemia cohort versus the nononcology cohort; however, mortality did not exceed 40% unless there were four or more organ failures in the admission. Mortality for admissions requiring intensive care decreased over time for both cohorts (23.7% in 1999-2003 vs 16.4% in 2004-2010 in the acute myeloid leukemia cohort, p = 0.0367; and 7.5% in 1999-2003 vs 6.5% in 2004-2010 in the nononcology cohort, p < 0.0001). Pediatric patients with acute myeloid leukemia frequently required intensive care resources, with mortality rates substantially lower than previously reported. Mortality also decreased over the time studied. Pediatric acute myeloid leukemia patients with sepsis who required intensive care had a mortality comparable to children without oncologic diagnoses; however, overall mortality and mortality for each category of organ failure studied was higher for the acute myeloid leukemia cohort compared with the nononcology cohort.
    Pediatric Critical Care Medicine 12/2013; · 2.35 Impact Factor
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    ABSTRACT: Objective. Antimicrobial stewardship programs (ASPs) are recommended to optimize antimicrobial use for hospitalized patients. Although mechanisms for the implementation of ASPs have been described, data-driven approaches to prioritize specific conditions and antimicrobials for intervention have not been established. We aimed to develop a strategy for identifying high-impact targets for antimicrobial stewardship efforts. Design. Retrospective cross-sectional study. Setting and patients. Children admitted to 32 freestanding children's hospitals in the United States in 2010. Methods. We identified the conditions with the largest proportional contribution to the total days of antibiotic therapy prescribed to all hospitalized children. For the 4 highest-using conditions, we examined variability between hospitals in antibiotic selection patterns for use of either first- or second-line therapies depending on the condition. Antibiotic use was determined using standardized probability of exposure to selected agents and standardized days of therapy per 1,000 patient-days, adjusting for patient demographics and severity of illness. Results. In 2010, 524,364 children received 2,082,929 days of antibiotic therapy. Surgical patients received 43% of all antibiotics. The 4 highest-using conditions-pneumonia, appendicitis, cystic fibrosis, and skin and soft-tissue infection-represent 1% of all conditions yet accounted for more than 10% of all antibiotic use. Wide variability in antibiotic use occurred for 3 of these 4 conditions. Conclusions. Antibiotic use in children's hospitals varied broadly across institutions when examining diagnoses individually and adjusting for severity of illness. Identifying conditions with both frequent and variable antimicrobial use informs the prioritization of high-impact targets for future antimicrobial stewardship interventions.
    Infection Control and Hospital Epidemiology 12/2013; 34(12):1252-8. · 4.02 Impact Factor
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    ABSTRACT: Objective. Antimicrobial susceptibility patterns across US pediatric healthcare institutions are unknown. A national pooled pediatric antibiogram (1) identifies nationwide trends in antimicrobial resistance, (2) allows across-hospital benchmarking, and (3) provides guidance for empirical antimicrobial regimens for institutions unable to generate pediatric antibiograms. Methods. In January 2012, a request for submission of pediatric antibiograms between 2005 and 2011 was sent to 233 US hospitals. A summary antibiogram was compiled from participating institutions to generate proportions of antimicrobial susceptibility. Temporal and regional comparisons were evaluated using χ(2) tests and logistic regression, respectively. Results. Of 200 institutions (85%) responding to our survey, 78 (39%) reported generating pediatric antibiograms, and 55 (71%) submitted antibiograms. Carbapenems had the highest activity against the majority of gram-negative organisms tested, but no antibiotic had more than 90% activity against Pseudomonas aeruginosa. Approximately 50% of all Staphylococcus aureus isolates were methicillin resistant. Western hospitals had significantly lower proportions of S. aureus that were methicillin resistant compared with all other regions tested. Overall, 21% of S. aureus isolates had resistance to clindamycin. Among Enterococcus faecium isolates, the prevalence of susceptibility to ampicillin (25%) and vancomycin (45%) was low but improved over time ([Formula: see text]), and 8% of E. faecium isolates were resistant to linezolid. Southern hospitals reported significantly higher prevalence of E. faecium with susceptibilities to ampicillin, vancomycin, and linezolid compared with the other 3 regions ([Formula: see text]). Conclusions. A pooled, pediatric antibiogram can identify nationwide antimicrobial resistance patterns for common pathogens and might serve as a useful tool for benchmarking resistance and informing national prescribing guidelines for children.
    Infection Control and Hospital Epidemiology 12/2013; 34(12):1244-51. · 4.02 Impact Factor
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    ABSTRACT: Background. Invasive fungal infections (IFI) cause significant morbidity and mortality for children with acute myeloid leukemia (AML). Data on the comparative effectiveness of antifungal prophylaxis in this population are limited. Methods. A pediatric AML cohort was assembled from the Pediatric Health Information System database using ICD-9 codes and pharmacy data. Antifungal prophylaxis status was determined by pharmaceutical data review within 21 days of starting induction chemotherapy. Patients were followed until end of induction, death, or loss to follow-up. Cox regression analyses compared induction mortality and resources utilized between patients receiving and not receiving antifungal prophylaxis. A propensity score accounted for variation in demographic factors, location of care and severity of illness at presentation. Results. 871 AML patients were identified; the induction case fatality rate was 3.7%. In the adjusted Cox regression model, patients receiving antifungal prophylaxis (57%) had a decreased hazard for induction mortality (HR: 0.42, 95% CI: 0.19- 0.90). Children receiving prophylaxis were less frequently exposed to broad-spectrum Gram-positive (IRR: 0.87, 95% CI: 0.79-0.97) and anti-pseudomonal beta-lactam agents (HR: 0.91, 95% CI: 0.85-0.96), had fewer blood cultures (IRR: 0.78, 95% CI: 0.71-0.86) and fewer chest CT scans (IRR: 0.73, 95% CI: 0.60-0.88). Conclusions. Antifungal prophylaxis in pediatric AML patients is associated with reduced induction mortality rates and supportive care resources. Further investigation is necessary to determine whether antifungal prophylaxis should include anti-mold activity.
    Clinical Infectious Diseases 11/2013; · 9.37 Impact Factor
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    ABSTRACT: Objective. Optimal strategies for limiting the transmission of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella spp (ESBL-EK) in the hospital setting remain unclear. The objective of this study was to evaluate the impact of a urine culture screening strategy on the incidence of ESBL-EK. Design. Prospective quasi-experimental study. Setting. Two intervention hospitals and one control hospital within a university health system from 2005 to 2009. Patients and Intervention. All clinical urine cultures with E. coli or Klebsiella spp were screened for ESBL-EK. Patients determined to be colonized or infected with ESBL-EK were placed in a private room with contact precautions. The primary outcome of interest was nosocomial ESBL-EK incidence in nonurinary clinical cultures (cases occurring more than 48 hours after admission). Changes in monthly ESBL-EK incidence rates were evaluated with mixed-effects Poisson regression models, with adjustment for institution-level characteristics (eg, total admissions). Results. The overall incidence of ESBL-EK increased from 1.42/10,000 patient-days to 2.16/10,000 patient-days during the study period. The incidence of community-acquired ESBL-EK increased nearly 3-fold, from 0.33/10,000 patient-days to 0.92/10,000 patient-days ([Formula: see text]). On multivariable analysis, the intervention was not significantly associated with a reduction in nosocomial ESBL-EK incidence (incidence rate ratio, 1.38 [95% confidence interval, 0.83-2.31]; [Formula: see text]). Conclusions. Universal screening of clinical urine cultures for ESBL-EK did not result in a reduction in nosocomial ESBL-EK incidence rates, most likely because of increases in importation of ESBL-EK cases from the community. Further studies are needed on elucidating optimal infection control interventions to limit spread of ESBL-producing organisms in the hospital setting.
    Infection Control and Hospital Epidemiology 11/2013; 34(11):1160-1166. · 4.02 Impact Factor
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    ABSTRACT: Rates of invasive candidiasis (IC) in children between 2003 and 2011 were evaluated in a retrospective cross-sectional analysis. The rate of IC decreased 72% (p<0.0001) and in neonates specifically rate of IC decreased 91% (P<0.0001). Improving infection control efforts is hypothesized as a contributing factor for this decrease.
    Clinical Infectious Diseases 10/2013; · 9.37 Impact Factor
  • Philip Toltzis, Theoklis Zaoutis
    Clinical Infectious Diseases 09/2013; · 9.37 Impact Factor
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    ABSTRACT: This 13-year retrospective study investigated risk factors for candidemia secondary to Candida species with increased likelihood of fluconazole resistance. Of 344 candidemia cases, 23 were caused by C glabrata or C krusei (CGCK). Age >2 years, recent fluconazole exposure, and recent surgery were independent risk factors for CGCK.
    Journal of the Pediatric Infectious Diseases Society. 09/2013; 2(3):263-266.
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    ABSTRACT: The objective was to estimate the frequency of pregnancy testing among adolescent emergency department (ED) patients and to determine factors associated with testing. This was a retrospective cross-sectional study using the National Hospital Ambulatory Medical Care Survey (NHAMCS) from 2005 through 2009 of ED visits by females ages 14 to 21 years. The frequency of pregnancy testing among all visits was estimated for potential reproductive health complaints and for those associated with exposure to potentially teratogenic radiation. Multivariable logistic regression modeling was performed to calculate adjusted probabilities and odds ratios (ORs) with 95% confidence intervals (CIs) to evaluate factors associated with pregnancy testing by patient characteristics. The authors identified 11,531 visits, representing an estimated 41.0 million female adolescent ED visits. Of these, 20.9% (95% CI = 19.3% to 22.5%) included pregnancy testing. Among visits for potential reproductive health complaints and those associated with exposure to potentially teratogenic radiation, 44.5% (95% CI = 41.3% to 47.8%) and 36.7% (95% CI = 32.5% to 40.9%), respectively, included pregnancy testing. Among the entire study population, we found statistically significant differences in pregnancy testing by age, race or ethnicity, hospital admission, and geographic region (p < 0.001 for all). A minority of female adolescent ED visits included pregnancy testing, even if patients presented with potential reproductive health complaints or received exposure to ionizing radiation. Small but statistically significant differences in pregnancy testing rates were noted based on age, race or ethnicity, ED disposition, and geographic region. Future studies should focus on designing quality improvement interventions to increase pregnancy testing in adolescent ED patients, especially among those in whom pregnancy complications or the risk of potentially teratogenic radiation exposure is higher.
    Academic Emergency Medicine 08/2013; 20(8):816-21. · 1.76 Impact Factor
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    ABSTRACT: Invasive candidiasis is a life-threatening infection in patients with haematological malignancies. The objective of our study was to determine the incidence, microbiological characteristics and clinical outcome of candidaemia among hospitalized adult patients with haematological malignancies. This is a population-based, prospective, multicentre study of patients ≥18 years admitted to haematology and/or haematopoietic stem cell transplantation units of nine tertiary care Greek hospitals from January 2009 through to February 2012. Within this cohort, we conducted a nested case-control study to determine the risk factors for candidaemia. Stepwise logistic regression was used to identify independent predictors of 28-day mortality. Candidaemia was detected in 40 of 27 864 patients with haematological malignancies vs. 967 of 1 158 018 non-haematology patients for an incidence of 1.4 cases/1000 admissions vs. 0.83/1000 respectively (p <0.001). Candidaemia was caused predominantly (35/40, 87.5%) by non-Candida albicans species, particularly Candida parapsilosis (20/40, 50%). In vitro resistance to at least one antifungal agent was observed in 27% of Candida isolates. Twenty-one patients (53%) developed breakthrough candidaemia while receiving antifungal agents. Central venous catheters, hypogammaglobulinaemia and a high APACHE II score were independent risk factors for the development of candidaemia. Crude mortality at day 28 was greater in those with candidaemia than in control cases (18/40 (45%) vs. 9/80 (11%); p <0.0001). In conclusion, despite antifungal prophylaxis, candidaemia is a relatively frequent infection associated with high mortality caused by non-C. albicans spp., especially C. parapsilosis. Central venous catheters and hypogammaglobulinaemia are independent risk factors for candidaemia that provide potential targets for improving the outcome.
    Clinical Microbiology and Infection 06/2013; · 4.58 Impact Factor
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    ABSTRACT: Antimicrobial stewardship programs have been effective for inpatients, often through prescribing audit and feedback. However, most antimicrobial use occurs in outpatients with acute respiratory tract infections (ARTIs). To evaluate the effect of an antimicrobial stewardship intervention on antibiotic prescribing for pediatric outpatients. Cluster randomized trial of outpatient antimicrobial stewardship comparing prescribing between intervention and control practices using a common electronic health record. After excluding children with chronic medical conditions, antibiotic allergies, and prior antibiotic use, we estimated prescribing rates for targeted ARTIs standardized for age, sex, race, and insurance from 20 months before the intervention to 12 months afterward (October 2008-June 2011). A network of 25 pediatric primary care practices in Pennsylvania and New Jersey; 18 practices (162 clinicians) participated. One 1-hour on-site clinician education session (June 2010) followed by 1 year of personalized, quarterly audit and feedback of prescribing for bacterial and viral ARTIs or usual practice. MAIN OUTCOMES AND MEASURES: Rates of broad-spectrum (off-guideline) antibiotic prescribing for bacterial ARTIs and antibiotics for viral ARTIs for 1 year after the intervention. Broad-spectrum antibiotic prescribing decreased from 26.8% to 14.3% (absolute difference, 12.5%) among intervention practices vs from 28.4% to 22.6% (absolute difference, 5.8%) in controls (difference of differences [DOD], 6.7%; P = .01 for differences in trajectories). Off-guideline prescribing for children with pneumonia decreased from 15.7% to 4.2% among intervention practices compared with 17.1% to 16.3% in controls (DOD, 10.7%; P < .001) and for acute sinusitis from 38.9% to 18.8% in intervention practices and from 40.0% to 33.9% in controls (DOD, 14.0%; P = .12). Off-guideline prescribing was uncommon at baseline and changed little for streptococcal pharyngitis (intervention, from 4.4% to 3.4%; control, from 5.6% to 3.5%; DOD, -1.1%; P = .82) and for viral infections (intervention, from 7.9% to 7.7%; control, from 6.4% to 4.5%; DOD, -1.7%; P = .93). In this large pediatric primary care network, clinician education coupled with audit and feedback, compared with usual practice, improved adherence to prescribing guidelines for common bacterial ARTIs, and the intervention did not affect antibiotic prescribing for viral infections. Future studies should examine the drivers of these effects, as well as the generalizability, sustainability, and clinical outcomes of outpatient antimicrobial stewardship. clinicaltrials.gov Identifier: NCT01806103.
    JAMA The Journal of the American Medical Association 06/2013; 309(22):2345-52. · 29.98 Impact Factor
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    ABSTRACT: PURPOSE: In 2002, the Centers for Disease Control and Prevention (CDC) broadened the pelvic inflammatory disease (PID) diagnostic criteria to increase detection and prevent serious sequelae of untreated PID. The impact of this change on PID detection is unknown. Our objectives were to estimate trends in PID diagnosis among adolescent emergency department (ED) patients before and after the revised CDC definition and to identify factors associated with PID diagnoses. METHODS: We performed a retrospective repeated cross-sectional study using the National Hospital Ambulatory Medical Care Survey from 2000 to 2009 of ED visits by 14- to 21-year-old females. We calculated national estimates of PID rates and performed multivariable logistic regression analyses and tests of trends. RESULTS: During 2000-2009, of the 77 million female adolescent ED visits, there were an estimated 704,882 (95% confidence interval [CI], 571,807-837,957) cases of PID. After the revised criteria, PID diagnosis declined from 5.4 cases per 1,000 United States adolescent females to 3.9 cases per 1,000 (p = .03). In a multivariable model, age ≥17 years (odds ratio, 2.14; 95% CI, 1.25-3.64) and black race (odds ratio, 2.04; 95% CI, 1.36-3.07) were associated with PID diagnosis. CONCLUSIONS: Despite broadened CDC diagnostic criteria, PID diagnoses did not increase over time. This raises concern about awareness and incorporation of the new guidelines into clinical practice.
    Journal of Adolescent Health 05/2013; · 2.97 Impact Factor
  • JAMA pediatrics. 05/2013;
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    ABSTRACT: Background. C. difficile infection (CDI) is associated with significant morbidity and mortality among adults. Although CDI has increased among children, outcomes are poorly defined. Methods. A retrospective cohort study was performed among hospitalized children aged 1-18 years at 41 free-standing children's hospitals between 1/2006 and 8/2011. Patients with CDI (exposed) were matched 1:2 to patients without CDI (unexposed) based on the probability of developing CDI (propensity score derived from patient characteristics). Studied outcomes included death, length of stay (LOS), and total standardized cost. Sub-analyses were performed after stratifying exposed subjects by C. difficile test date, suggestive of community-onset (CO) versus hospital-onset (HO)-CDI. Results. We identified 5,107 exposed and 693,409 unexposed subjects. Age in years was 6 (2, 13) for exposed and 8 (3, 14) for unexposed [median (IQR)]. Of these, 4,474 exposed were successfully matched to 8,821 unexposed by propensity score. In-hospital mortality differed significantly [CDI (1.43%), matched unexposed (0.66%); (p<0.001)]. On sub-analysis, mortality rates were similar between CO-CDI and matched unexposed subjects. However, mortality rates were significantly greater among HO-CDI compared with matched unexposed [6.73 (3.77, 12.02); OR (95% CI)]. Mean differences in LOS and cost were significant [mean difference (95% CI)]: 5.55 days (4.54, 6.56) and $18, 900 (15,100, 22,700) for CO-CDI, and 21.60 days (19.29, 23.90) and $93, 600 (80,000, 107,200) for HO-CDI. Conclusions. Pediatric CDI is associated with increased mortality, longer LOS, and higher costs among hospitalized children. These findings underscore the importance of antibiotic stewardship and infection control programs to prevent this disease in children.
    Clinical Infectious Diseases 03/2013; · 9.37 Impact Factor

Publication Stats

4k Citations
700.60 Total Impact Points

Institutions

  • 2003–2014
    • The Children's Hospital of Philadelphia
      • • Division of Infectious Diseases
      • • Department of Pediatrics
      • • Division of General Pediatrics
      Philadelphia, Pennsylvania, United States
    • University of Pennsylvania
      • • Division of Infectious Disease
      • • Center for Therapeutic Effectiveness Research
      • • Center for Clinical Epidemiology and Biostatistics
      Philadelphia, Pennsylvania, United States
    • University of Nebraska at Omaha
      • Department of Pediatrics
      Omaha, NE, United States
  • 2013
    • George Washington University
      • Children's National Medical Center
      Washington, D. C., DC, United States
  • 2010–2013
    • Case Western Reserve University
      • • Division of Hematology and Oncology
      • • Rainbow Babies and Children's Hospital
      Cleveland, OH, United States
  • 2005–2013
    • Hospital of the University of Pennsylvania
      • • Division of Infectious Diseases
      • • Department of Pediatrics
      Philadelphia, Pennsylvania, United States
  • 2012
    • Hospital Infantil de Tamaulipas
      Victoria, Guanajuato, Mexico
    • Seattle Children's Hospital
      Seattle, Washington, United States
  • 2011
    • University of California, San Francisco
      • Department of Pediatrics
      San Francisco, CA, United States
  • 2009–2011
    • Columbia University
      • Department of Pediatrics
      New York City, NY, United States
    • Statens Serum Institut
      København, Capital Region, Denmark
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany
    • Aristotle University of Thessaloniki
      • Department of Pediatrics II
      Thessaloníki, Kentriki Makedonia, Greece
    • Christiana Care Health System
      Wilmington, Delaware, United States
  • 2008
    • National Institutes of Health
      • Department of Laboratory Medicine
      Bethesda, MD, United States
    • Duke University Medical Center
      Durham, North Carolina, United States
  • 2005–2008
    • National Cancer Institute (USA)
      • Pediatric Oncology Branch
      Maryland, United States
  • 2006
    • University of Arkansas at Little Rock
      Little Rock, Arkansas, United States
  • 1999
    • Thomas Jefferson University
      Philadelphia, Pennsylvania, United States