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Challener, Douglas W.

https://orcid.org/0000-0002-6964-9639

Mayo Clinic

Mayo Clinic

Citations 60

Relationship between Antibiotic Prescription and Survival in Hospice
Crowley, Patrick , Siegel, Leslie R. , Dickinson, Drew T. , Lahr, Brian D. , Whalen, Francis X. , Challener, Douglas W. , Crowley, Patrick D , Siegel, Leslie

Clinical Infectious Diseases | September 10, 2026 | Volume: No volume available | Issue: No issue available | Pages: No page available

10.1093/cid/ciag561 Get It

Abstract Background At hospice enrollment, patients are asked preferences regarding antibiotic use. Limited evidence on how these medications impact survival makes it difficult for clinicians to offer clear guidance. To support decision-making and antimicrobial stewardship, we assessed the association between antibiotic use and survival in outpatient hospice patients. Methods The association between antibiotic use and survival was evaluated using a time-dependent Cox proportional hazards model, adjusted for age, sex, Charlson Comorbidity Index, and hospice-qualifying conditions (HQCs). The cohort included patients enrolled in a large health system’s outpatient hospice program between June 20, 2017, and January 1, 2023. Results Among 6169 patients with an HQC, 1233 received at least one antimicrobial prescription during the study period. The median time from hospice enrollment to first prescription was 16 days (IQR 3-83). Antimicrobial prescribing patterns varied by HQC category. In time-dependent Cox models, antibiotic use was associated with increased hazard of death (aHR 1.47; 95% confidence interval [CI], 1.37–1.57).Stratified analyses showed the strongest association with increased mortality in patients with cancer HQCs (aHR 1.67; 95% CI, 1.50–1.87) and a survival benefit in those with infectious HQCs (aHR 0.60; 95% CI, 0.40–0.89). Discussion Physicians, patients, and families often overestimate the benefits of antibiotics near the end of life. The observed increase in mortality shortly after antibiotic initiation suggests that symptoms prompting antibiotic use may reflect the dying process rather than treatable infection. Knowledge of the limited role of antibiotics in prolonging life in hospice settings may improve decision-making and enhance the quality of end-of-life care.
Show Me the “Mino:” In Vitro Efficacy of Minocycline on Clinical Gram-Negative Bacterial Isolates
Streck, Nicholas , Saleh, O. Abu, Crowley, Patrick D , Mira, Portia , Challener, Douglas W. , Abu Saleh, Omar , Crowley, Patrick D., Ranganath, Nischal , Rivera, Christina G. , AbuSaleh, Omar

Microbial Drug Resistance | March 31, 2026 | Volume: 32 | Issue: 4 | Pages: 128-134

10.1177/10766294261424485 Get It

Background: There are limited oral treatment options available for resistant Gram-negative bacterial (GNB) infections. Minocycline, a second-generation tetracycline antibiotic, offers good bioavailability and broad-spectrum coverage that may be an option for GNB infections. Methods: We conducted a retrospective review of minocycline susceptibility testing performed on GNB isolates at the Mayo Clinic reference lab between 2013 and 2022. Minocycline susceptibility was evaluated with a focus on difficult-to-treat organisms and relevant anatomic source. Organisms included resistant isolates of Escherichia coli and Klebsiella pneumoniae ; high-risk ampC-derepressors, including Citrobacter freundii, Enterobacter cloacae, and K. aerogenes; and clinically challenging non-Enterobacterales, Acinetobacter species, Achromobacter species, and Stenotrophomonas maltophilia . Results: Of 217,206 GNB isolates, 18,148 Enterobacterales (EB) and 8,190 non- Enterobacter isolates were tested for minocycline susceptibility. Of these, 80% of all EB and 92% of non-EB isolates were susceptible. Among E. coli isolates with ceftriaxone, ciprofloxacin, meropenem, or multidrug resistance, minocycline susceptibility was 78%, 76%, 70%, and 70.9%, respectively. Among the K. pneumoniae isolates with ceftriaxone, ciprofloxacin, meropenem, or multidrug resistance, minocycline susceptibility was 46%, 38%, 37%, and 39.3%, respectively. 85% of C. freundii , 81% of E. cloacae, and 85% of K. aerogenes isolates were susceptible to Minocycline. 83.5% of Achromobacter species isolates, 66% of Acinetobacter species isolates, and 99.1% of S. maltophilia isolates were susceptible. Conclusions: Our study reports the largest collection of minocycline susceptibility findings in GNB. Minocycline showed in vitro activity against many difficult-to-treat GNB isolates, including ceftriaxone- and multidrug-resistant E. coli and some K. pneumoniae isolates, common Amp-C-producing species, and non-fermenting GNB, including Stenotrophomonas , Acinetobacter , and Achromobacter .
Clinical Manifestations, Long-Term Trends, and Risk Factors for Treatment Failure in Native Vertebral Osteomyelitis: A 26-Year Mayo Clinic Experience
Matsuo, Takahiro , Borgonovo, Fabio , Lahr, B. A., Petri, Francesco , Igwilo-Alaneme, Rita , Mulett, Sergio L Alvarez, Alavi, Seyed Mohammad Amin, Challener, Doug W, Nassr, Ahmad, Huddleston, Paul M, Berbari, Elie F. , Petri, Francesco , Matsuo, Takahiro , Lahr, Brian D. , Alvarez Mulett, Sergio , Challener, Douglas , Tande, Aaron , Berbari, Elie F , Borgonovo, Fabio , Alavi, Seyed Mohammad Amin , Challener, Douglas W. , Nassr, Ahmad , Huddleston, P.M. , Tande, Aaron J.

Clinical Infectious Diseases | January 31, 2026 | Volume: 82 | Issue: 6 | Pages: e1171-e1180

10.1093/cid/ciag048 Get It

Abstract Background Native vertebral osteomyelitis (NVO) is a life-threatening spinal infection with rising incidence and significant morbidity. Despite its growing burden, long-term data on clinical characteristics, management trends, and outcomes remain limited. Methods We conducted a 26-year multicenter retrospective cohort study of adults (≥18 years) diagnosed with NVO at Mayo Clinic sites between 1999 and 2024. Demographic, microbiologic, treatment, and outcome data were analyzed across five time periods. Predictors of treatment failure were assessed using a multivariable competing risk model. Results Among 1255 patients (median age 67; 66% male), lumbosacral involvement was most common (65%), and 21% had multilevel involvement. Pathogens were identified in 77%, most commonly Staphylococcus aureus (49%; Methicillin-susceptible S. aureus 37%, methicillin-resistant S. aureus 13%). Over time from 1999–2004 to 2020–2024, Gram-negative bacilli increased from 6% to 14% (P = .048). Comorbidities including chronic kidney disease (10% to 21%), active chemotherapy (6% to 11%), and immunosuppression (8% to 17%) increased significantly. Additionally, 1-year treatment failure declined (16% to 10%). In multivariable analysis, diabetes mellitus (subdistribution hazard ratio [sHR] 1.92, 95% CI 1.18–3.13) and multilevel involvement (sHR 1.67, 95% CI 1.17–2.38) were associated with increased incidence of treatment failure, while concurrent infections (sHR 0.57, 95% CI 0.37–0.87) and higher Charlson Comorbidity Index (sHR 0.62, 95% CI 0.43–0.90) were associated with lower failure. Conclusions This large multicenter cohort highlights increasing host complexity, shifting microbiology, and predictors of failure, emphasizing the importance of early risk stratification and tailored strategies, such as multidisciplinary evaluation and close follow-up of high-risk patients to improve outcomes.
P-2148. Infection Following Cytokine Release Syndrome in Patients Receiving Chimeric Antigen Receptor T-Cell Therapy
Nadarevic, Ella, Corraes, Andre De Menezes Silva, Lin, Y., McHugh, Jack , Challener, Douglas W. , Corraes, Andre De Menezes Silva , Vergidis, Paschalis

Open Forum Infectious Diseases | January 12, 2026 | Volume: 13 | Issue: Supplement_1 | Pages: No page available

10.1093/ofid/ofaf695.2311 Get It

Abstract Background Chimeric antigen receptor T-cell therapy (CAR-T) has transformed care for relapsed or refractory B-cell malignancies. Cytokine-release syndrome (CRS) complicates most infusions, yet the ensuing infection risk is ill-defined.Table 1Profile of 230 patients undergoing with CRS following CAR-T therapyTable 2Cytokine Release Syndrome Severity, Management, and Early Outcomes by 90-Day Infection Status Methods CAR-T recipients who developed CRS at our institution from 1 Jan 2018 to 3 June 2024 were retrospectively reviewed. Variables were abstracted into REDCap. CRS was graded with American Society for Transplantation and Cellular Therapy (ASTCT) criteria. All infections occuring after CRS onset to day 90 were adjudicated. Continuous data are reported as medians with interquartile ranges (IQR); categorical data as counts and percentages. Table 2 comparisons used Mann-Whitney U for continuous and χ² or Fisher exact tests for categorical variables (two sided, P < 0.05). Multivariable logistic regression was used to identify independent predictors of infection.Table 3Infectious Syndromes, Pathogens, and Timing of First Infection Following CRS Onset Results Among 230 CRS cases, median age was 64 yr (IQR 57–70) and 59% were male. Non-Hodgkin lymphoma accounted for 62% and multiple myeloma for 38%. Median prior therapy lines were 3. CRS was grade 1–2 in 97%. CAR-HEMATOTOX was low in 156 (68%) (Table 1). Within 90 days, 51 patients (22%) developed infection; median onset was 15 days (IQR 5–26). Infected patients more often received anakinra (22% vs 8%, p = 0.02) and required ICU care (18% vs 7%, p = 0.05); grade ≥3 CRS trended higher (10% vs 3%, p = 0.06). In multivariable analysis adjusting for age, CAR-HEMATOTOX, ICU admission, and anakinra, both ICU admission (aOR 2.06; 95% CI 0.70–5.81; p = 0.18) and anakinra use (aOR 2.18; 95% CI 0.83–5.53; p = 0.10) were associated with higher infection odds, though not statistically significant. 90-day survival was 88% with infection versus 96% without (p = 0.09) (Table 2). 51 infectious episodes were documented: bacteremia 22; gastrointestinal 9; central line–associated bloodstream infection 7; other sites 22. Bacteria caused 59%, viruses 37% (15 CMV, 4 SARS-CoV-2), and fungi 4%. No infection-related deaths occurred (Table 3). Conclusion Infection was common after CRS, but did not alter early survival. Anakinra exposure and ICU admission were associated with a higher likelihood of infection, though not statistically significant. Targeted surveillance should focus on patients requiring intensified CRS management. Disclosures Yi Lin, M.D., BMS: Board Member|Caribou: Advisor/Consultant|Genentech: Board Member|Jassen: Board Member|Jassen: Steering Committee|Kite/Gilead: Steering Committee|Legend: Board Member|NexImmune: Advisor/Consultant|NexT Therapeutics: Board Member|Pfizer: Board Member|Regeneron: Board Member|Sanofi: Board Member|Tessera: Board Member Paschalis Vergidis, MD, MSc, Current Fungal Infection Reports: Honoraria|F2G: Grant/Research Support|Merck Manuals: Honoraria|Mundipharma: Grant/Research Support|Scynexis: Advisor/Consultant|Scynexis: Grant/Research Support
P-2152. Adenovirus Viremia in Adults: Clinical Syndromes, Risk Factors, and Outcomes
Mughrabi, Abdallah , Razonable, Raymund R, Saleh, Omar Abu , Challener, Douglas W. , Fida, Madiha , Razonable, Raymund R.

Open Forum Infectious Diseases | January 12, 2026 | Volume: 13 | Issue: Supplement_1 | Pages: No page available

10.1093/ofid/ofaf695.2315 Get It

Abstract Background Adenovirus is a ubiquitous dsDNA virus with potential for end-organ disease. End-organ or disseminated adenoviral disease (EOD) occurs more frequently in hematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients. We aim to characterize the clinical manifestations and outcome of adenovirus viremia in adults, including HSCT and SOT recipients. We describe severity of illness, organ-involvement, and graft and patient survival. Methods This retrospective, multi-site, study enrolled adults patients with positive adenovirus PCR in blood and other clinical specimens from January, 2010 through April, 2025. We excluded patients with insufficient medical records, follow up less than 30 days, and isolated conjunctivitis without viremia. EOD was defined by the presence of clinical signs or symptoms consistent with organ involvement, confirmed by a positive adenovirus PCR or by histopathology. Descriptive and comparative statistics were performed using R. Results Fifty patients with adenovirus viremia were included in this study. The most common immunocompromising conditions were corticosteroid use (84%, n = 42), HSCT (40%, n = 20) and SOT (34%, n = 17) (Table 1). Only 3 patients (6%) had no known immunocompromising condition. 20 patients (40%) had EOD while 30 patients (60%) had isolated viremia. Lungs were the most affected organ, followed by the gastrointestinal tract and liver (Figure 1). EOD was more prevalent in older patients (60 vs. 41 years, p =0.03) and in those with higher initial plasma viral load (673364 vs. 6593, p=0.005). The most common treatment was reduction in immunosuppression (Table 2). Cidofovir was more often used in patients with EOD. Adenovirus-related outcomes were worse in patients with EOD [higher rates of mortality (45% vs. 13.3%) and ICU admission (60% vs. 20%)] vs. without EOD (Table 3). Conclusion Adenovirus viremia is associated with high mortality in a cohort of mostly immunocompromised adults, particularly those with EOD. Older age and a higher initial plasma viral load are associated with EOD. Patients with EOD had worse clinical outcomes such as ICU admission and adenovirus-related mortality. Disclosures All Authors: No reported disclosures
P-1935. Persistent Candidemia: Predictors and Outcomes in a Multicenter Matched Analysis
Bayless, David, Saleh, Omar M Abu, Bayless, David , McHugh, Jack , Saleh, Omar Abu , Vergidis, Paschalis , Challener, Douglas W.

Open Forum Infectious Diseases | January 12, 2026 | Volume: 13 | Issue: Supplement_1 | Pages: No page available

10.1093/ofid/ofaf695.2103 Get It

Abstract Background Persistent candidemia (PC) occurs in a minority of Candida bloodstream infections (BSIs) but is associated with increased morbidity. Comparative data on patient profile, species distribution and outcomes are limited.Table 1Clinical profile and outcomes of patients with persistent candidemia in the primary study cohort. ANC = absolute neutrophil count. SD = standard deviation.Table 2Comparative analysis of persistent candidemia and non-persistent candidemia cases. Methods All candidemia episodes at three academic medical centers (2018-2025) were reviewed. Persistence was defined as ≥72 hours of positive blood cultures after appropriate antifungal initiation. Each PC case was matched 1:2 to non-PC controls who survived ≥72 hours. Demographics, Charlson Comorbidity Index (CCI), Candida species distribution, and outcomes were used for comparative analysis. Continuous variables were summarized as median (interquartile range [IQR]) and compared with Wilcoxon rank-sum, while categorical data (n%) were analyzed by Fisher’s exact test (species by χ²), yielding odds ratios (ORs) with 95% confidence intervals (CIs). Two-tailed p < 0.05 denoted significance. Results Each PC case (n = 46) was matched 1:2 to non-PC controls (n = 92). Clinical profiles and outcomes of PC cases are presented in Table 1. Most PC patients (54.3%) had an immunocompromising condition, and non-urinary intra-abdominal sources were the most frequently suspected infection source (21/46; 45.7%). All but one of 46 PC cases had antibiotic exposure within the preceding 90 days. Comparative demographics and outcomes for PC cases and non-PC controls are displayed in Table 2. PC patients were younger (median 62 yr, IQR 45–69 vs 68 yr, 57–76; p = 0.01), more often female (59% vs 30%; OR 3.3, 95% CI 1.5–7.1; p = 0.002), and had higher comorbidity (CCI 5, IQR 3–8 vs 3, 1–4; p < 0.001). Species distribution differed (χ² p = 0.04), driven by C. guilliermondii over-representation in PC cases (9% vs 0%) (Figures 1 and 2). Hospital stay was longer in PC cases (median 36 d, 24–54 vs 16 d, 8–28; p < 0.001) and time from admission to first culture greater (12 d, 3–26 vs 3 d, 1–10; p = 0.003). 90-day mortality was 54.3% (25/46) in PC cases versus 31.5% (29/92) in controls (OR 2.57, 95% CI 1.17–5.71; p = 0.016). Conclusion In this 7-year multicenter study, there were significant differences in demographics, microbiology, and clinical outcomes between PC and non-PC cases, including higher short-term mortality rates with PC in univariate analysis. Disclosures Paschalis Vergidis, MD, MSc, Current Fungal Infection Reports: Honoraria|F2G: Grant/Research Support|Merck Manuals: Honoraria|Mundipharma: Grant/Research Support|Scynexis: Advisor/Consultant|Scynexis: Grant/Research Support
Quality assessment of artificial intelligence‐generated versus human‐written hospital summaries evaluating detail, usefulness, and continuity of care
Ryu, Alexander J. , Heaton, Heather A. , Challener, Douglas , Ayanian, Shant , Ryu, Alexander, O'horo, John, Heaton, Heather, Challener, Douglas W. , Ryu, Alexander J. , O’Horo, John C.

Journal of Hospital Medicine | October 1, 2025 | Volume: 21 | Issue: 4 | Pages: 375-379

10.1002/jhm.70163 Get It

Abstract Background Hospital discharge summaries are critical for ensuring continuity of care, but their quality often varies. Large language models (LLMs) have the potential to standardize and enhance the efficiency of this documentation process. Objectives To evaluate the quality of hospital discharge summaries created by an LLM‐based hospital course drafting tool created by Epic Systems compared with human‐written summaries. Methods Retrospective study at a single tertiary‐care institution in 2024. The cohort included 100 adult hospitalizations lasting >72 h across medical and surgical dismissing services. No interventions were performed. Summaries (LLM‐generated vs. human‐written) were independently reviewed using a standardized rubric covering nine domains (e.g., comprehensiveness, clarity, relevance). Scores were normalized and compared. Readability was assessed using Flesch Reading Ease. Results LLM‐generated summaries outperformed human‐written summaries across all criteria ( p < .05), with the greatest difference observed in comprehensiveness (LLM median 0.62 vs. human −0.23). Human‐written summaries from surgical services scored lower than those from medical services, but LLM performance was consistent across both. Human summaries had higher Flesch Reading Ease scores (33.11 vs. 26.2; p < .05), reflecting simpler language. Conclusions LLM‐generated summaries demonstrated superior quality, consistency, and clinical utility compared with human‐written summaries, highlighting their potential to improve documentation efficiency and standardization.
The Influence of the Coronavirus Disease 2019 Pandemic on Influenza Vaccination Refusal and Patient Satisfaction
Man, Olivia , McHugh, Jack , Wilshusen, Laurie , Hart, Lacey, Welch, Tripp, O’Horo, John C. , Man, Olivia M , McHugh, Jack , Wilshusen, Laurie L , O'Horo, John C , Challener, Douglas , Young, Jeremy, Welch, Tripp, Challener, Douglas W.

Open Forum Infectious Diseases | June 27, 2025 | Volume: 12 | Issue: 7 | Pages: No page available

10.1093/ofid/ofaf351 Get It

Abstract Background We examined how the COVID-19 pandemic influenced influenza vaccination, healthcare engagement, and patient satisfaction. Methods We retrospectively analyzed influenza vaccination records and patient experience surveys of adult primary care patients in southeastern Minnesota during two 3-year phases: Prepandemic (1 January 2017–28 February 2020) and Pandemic-Plus (1 March 2020–31 December 2023). Vaccination status was defined as “always vaccinated” (AV), “never vaccinated” (NV), or “intermittently vaccinated” (IV) for seasonal influenza. Results During the Pandemic-Plus phase, 7.0% (n = 3556) of the Prepandemic AV and 48.7% (n = 16 710) of the Prepandemic IV patients never received another influenza vaccine. Compared to AV, IV and NV patients were more likely to reside in areas with greater socioeconomic deprivation (odds ratio [OR], 1.58 [95% confidence interval {CI}, 1.53–1.62] and 1.99 [1.94–2.05], respectively), have a high school education or less (2.86 [2.74–2.98] and 3.38 [3.23–3.53]), and report healthcare disengagement (1.59 [1.55–1.64] and 4.21 [4.09–4.33]). After adjusting for Area Deprivation Index and medical comorbidities, healthcare disengagement increased among the NV versus AV between phases (3.33 [3.24–3.41] and 4.23 [4.10–4.35]). In a subgroup analysis those with severe comorbidities were less likely AV (NV vs AV: 1.21 [1.14–1.27]) and more dissatisfied with care (NV vs AV: 1.25 [1.18–1.33]). Conclusions The COVID-19 pandemic altered vaccination behaviors and healthcare satisfaction, especially among those at high risk of developing influenza-related complications. Medical providers and public health officials should be aware of factors associated with vaccine refusal to better target interventions.
Flesch-Kincaid Grade Level Readability Scores to Evaluate Readability of Clinical Documentation During an Electronic Health Record Transition
Wen, Andrew , O’Horo, John C. , Nyman, M. , Challener, Douglas , Fan, Jungwei W, O'horo, John, Nyman, Mark, O'Horo, John C , Wen, Andrew , Challener, Douglas W. , Fan, Jungwei , Liu, Hongfang

Advances in Health Information Science and Practice | June 18, 2025 | Volume: 1 | Issue: 1 | Pages: No page available

10.63116/vbwy7913 Get It

Background Electronic health records (EHRs) serve as a critical tool for clinical documentation, yet their complexity has raised concerns about readability and usability for healthcare providers and patients. Readability scores, such as the Flesch-Kincaid (FK) Grade Level, offer a quantitative method to assess documentation clarity. In this study, the authors evaluated the impact of an EHR transition on the readability of clinical notes across multiple medical specialties. Methods All clinical notes recorded between 2016 and 2019 at a large healthcare organization were evaluated across specialties. The organization transitioned EHR systems during the study period, in May 2018. FK Grade Level scores were calculated for each clinical consultation note and stratified by specialty and EHR. Results Across 10 medical specialties, 630,246 clinical notes were evaluated. The median FK grade levels from notes composed in the new EHR were similar to those composed in the previous EHR (8.228 vs 8.240; p=0.58). The variation in FK grade level as measured by standard deviation was lower in the new EHR compared with the old EHR (1.405 vs 1.764; p <0.01). Conclusions Calculation of FK grade level of clinical notes is a feasible method to assess clinical note readability. Study results showed that clinical documentation readability may not be strongly associated with underlying EHR. Migrating to a new EHR alone should not be expected to improve readability of clinical notes.
Cumulative Antibiotic Exposure Is Associated With Ceftriaxone Resistance Among Patients With Urinary Source Gram-negative Bloodstream Infection: A Retrospective Cohort Study
Tande, Aaron J. , Stevens, Ryan W. , Ilges, Dan , Lahr, Brian D. , Challener, Douglas , Tande, Aaron , Stevens, Ryan W , Ilges, Dan , Challener, Douglas W.

Clinical Infectious Diseases | June 14, 2025 | Volume: 81 | Issue: 5 | Pages: 871-878

10.1093/cid/ciaf315 Get It

Abstract Background We investigated the relationship between cumulative, historical antibiotic therapy and the presence of ceftriaxone-resistant (CRO-R) Enterobacterales bloodstream infections (BSI) from urinary sources. Methods Adult patients established with primary care at Mayo Clinic with a first episode of monomicrobial Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, or Proteus mirabilis BSI from a urinary source from May 2019 to May 2023 were included. Antibiotic therapy over the year prior to BSI was quantified as days of therapy (DOT), cumulative modified Antibiotic Spectrum Index (mASI), and cumulative Days of Antibiotic Spectrum Coverage (DASC) using prescription data. Patients with CRO-R urinary pathogens prior to antibiotic therapy assessment were excluded. Results In total, 721 adults had monomicrobial gram-negative BSI, including 70 patients (9.7%) with a CRO-R pathogen and 651 patients (90.3%) with a ceftriaxone-susceptible (CRO-S) pathogen. In the 12 months prior to BSI, levels of antibiotic DOT, mASI, and DASC were significantly greater among patients with CRO-R BSI than CRO-S BSI (P &lt; .001). The median time from blood culture collection to appropriate antibiotic therapy was significantly longer in the CRO-R group (24 hours, interquartile range [IQR] 16–48) than the CRO-S group (1 hour, IQR 0–2) (P &lt; .001). Increasing cumulative antibiotic therapy prior to BSI, as quantified by the mASI, was significantly associated with increased risk of 1-year CDI after BSI (P = .027). Conclusions Patients with first episode CRO-R Enterobacterales BSI had significantly greater prior antibiotic exposure than patients with CRO-S BSI and experienced significant delay of appropriate therapy. Routine quantitation and reporting of prior antibiotic therapy may improve empiric prescribing.