Clinical Risk Score for Prediction of Extended-Spectrum β-Lactamase–Producing Enterobacteriaceae in Bloodstream Isolates

Infection Prevention and Control Strategies According to the Type of Multidrug-Resistant Bacteria and Candida auris in Intensive Care Units: A Pragmatic Resume including Pathogens R0 and a Cost-Effectiveness Analysis

Multidrug-resistant organism (MDRO) outbreaks have been steadily increasing in intensive care units (ICUs). Still, healthcare institutions and workers (HCWs) have not reached unanimity on how and when to implement infection prevention and control (IPC) strategies. We aimed to provide a pragmatic physician practice-oriented resume of strategies towards different MDRO outbreaks in ICUs. We performed a narrative review on IPC in ICUs, investigating patient-to-staff ratios; education, isolation, decolonization, screening, and hygiene practices; outbreak reporting; cost-effectiveness; reproduction numbers (R0); and future perspectives. The most effective IPC strategy remains unknown. Most studies focus on a specific pathogen or disease, making the clinician lose sight of the big picture. IPC strategies have proven their cost-effectiveness regardless of typology, country, and pathogen. A standardized, universal, pragmatic protocol for HCW education should be elaborated. Likewise, the elaboration of a rapid outbreak recognition tool (i.e., an easy-to-use mathematical model) would improve early diagnosis and prevent spreading. Further studies are needed to express views in favor or against MDRO decolonization. New promising strategies are emerging and need to be tested in the field. The lack of IPC strategy application has made and still makes ICUs major MDRO reservoirs in the community. In a not-too-distant future, genetic engineering and phage therapies could represent a plot twist in MDRO IPC strategies.

Development and external validation of a model to predict multidrug-resistant bacterial infections in patients with cirrhosis

With the increasing rate of infections caused by multidrug-resistant organisms (MDRO), selecting appropriate empiric antibiotics has become challenging. We aimed to develop and externally validate a model for predicting the risk of MDRO infections in patients with cirrhosis.

METHODS

We included patients with cirrhosis and bacterial infections from two prospective studies: a transcontinental study was used for model development and internal validation (n = 1302), and a study from Argentina and Uruguay was used for external validation (n = 472). All predictors were measured at the time of infection. Both culture-positive and culture-negative infections were included. The model was developed using logistic regression with backward stepwise predictor selection. We externally validated the optimism-adjusted model using calibration and discrimination statistics and evaluated its clinical utility.

RESULTS

The prevalence of MDRO infections was 19% and 22% in the development and external validation datasets, respectively. The model's predictors were sex, prior antibiotic use, type and site of infection, MELD-Na, use of vasopressors, acute-on-chronic liver failure, and interaction terms. Upon external validation, the calibration slope was 77 (95% CI .48-1.05), and the area under the ROC curve was .68 (95% CI .61-.73). The application of the model significantly changed the post-test probability of having an MDRO infection, identifying patients with nosocomial infection at very low risk (8%) and patients with community-acquired infections at significant risk (36%).

CONCLUSION

This model achieved adequate performance and could be used to improve the selection of empiric antibiotics, aligning with other antibiotic stewardship program strategies.

Demographic, clinical and molecular epidemiology of extended-spectrum beta-lactamase-producing Escherichia coli bloodstream infections in Central Australia

We describe the demographics, clinical and molecular epidemiology of extended-spectrum β-lactamase (ESBL) Escherichia coli bloodstream infections (BSI) in Central Australia. All ESBL-producing E. coli bloodstream isolates from January 2018 to December 2020 were retrospectively identified. Demographic and clinical information was extracted by chart review. Whole-genome sequencing was performed for multi-locus sequence typing, antibiotic-resistance genes, and phylogenetic relationships. We identified 41 non-duplicate episodes of ESBL E. coli BSI. Median age was 55 years (IQR 47-63), 78% were female, 93% were Aboriginal, and half came from a remote community. Infections were predominantly urinary (68%, 28/41). In the 12 months prior, 70% (26/37) of identified patients had been hospitalised and 81% (30/37) prescribed antibiotics. Meropenem and piperacillin-tazobactam susceptibility was maintained in 100% and 95% of isolates, respectively. Co-resistance to non-β-lactam antibiotics was 32% to gentamicin, 61% to trimethoprim/sulfamethoxazole, and 68% to ciprofloxacin. For sequenced isolates, 41% (16/35) were sequence type 131 (ST131). Mean acquired antibiotic-resistance genes for each isolate was 12.3 (SD 3.1). Four isolates carried an OXA-1 gene. Only non-ST131 isolates carried AmpC and acquired quinolone-resistance genes. There was some evidence of clustering of closely related strains, but no evidence of community or healthcare admission overlap. ESBL rates are rapidly rising in Central Australia, which is a conducive environment for antibiotic resistance development (e.g., overcrowding, socioeconomic disadvantages, high healthcare exposure and high antibiotic use). Future research is required to explore resistance-transmission dynamics in this unique setting.

Comparative analysis of a rapid diagnostic test and scoring tools for ESBL detection in Enterobacterales bloodstream infections for optimizing antimicrobial therapy

IMPORTANCE

Our study addresses a significant issue in the medical and scientific community-the delayed administration of appropriate antimicrobial treatments due to the time-consuming process of phenotypic susceptibility data collection in gram-negative bloodstream infections. Our research indicates that a multiplex PCR rapid diagnostic test (RDT) significantly outperformed two clinical scoring tools in predicting ceftriaxone susceptibility. Multiplex PCR also led to reduced instances of undertreatment with ceftriaxone and minimized overtreatment with carbapenems. Furthermore, multiplex PCR demonstrated high sensitivity and specificity in predicting ceftriaxone susceptibility. The results of our study underscore the potential RDTs to reduce the time to appropriate antimicrobial therapy, leading to improved patient outcomes and reduced healthcare costs.

Application of Precision Medicine Concepts in Ambulatory Antibiotic Management of Acute Pyelonephritis

Acute pyelonephritis (APN) is a relatively common community-acquired infection, particularly in women. The early appropriate antibiotic treatment of this potentially life-threatening infection is associated with improved outcomes. The international management guidelines for complicated urinary tract infections and APN recommend using oral antibiotics with <10% resistance among urinary pathogens. However, increasing antibiotic resistance rates among Escherichia coli and other Enterobacterales to fluoroquinolones, trimethoprim-sulfamethoxazole (TMP-SMX), and beta-lactams has left patients without reliable oral antibiotic treatment options for APN. This narrative review proposes using precision medicine concepts to improve empirical antibiotic therapy for APN in ambulatory settings. Whereas resistance rates to a particular antibiotic class may exceed 10% at the population-based level, the predicted antibiotic resistance rates based on patient-specific risk factors fall under 10% in many patients with APN on the individual level. The utilization of clinical tools for the prediction of fluoroquinolones, TMP-SMX, and third-generation cephalosporin resistance improves the ambulatory antibiotic management of APN. It may also reduce the need to switch antibiotic therapy later based on the in vitro antibiotic susceptibility testing results of bacterial isolates in urinary cultures. This approach may mitigate the burden of increasing antibiotic resistance in the community by ensuring that the initial antibiotic prescribed has the highest likelihood of treating APN appropriately.

Predicting Extended-Spectrum Beta-Lactamase and Carbapenem Resistance in Enterobacteriaceae Bacteremia: A Diagnostic Model Systematic Review and Meta-Analysis

Enterobacteriaceae bacteremia, particularly when associated with antimicrobial resistance, can result in increased mortality, emphasizing the need for timely effective therapy. Clinical risk prediction models are promising tools, stratifying patients based on their risk of resistance due to ESBL and carbapenemase-producing Enterobacteriaceae in bloodstream infections (BSIs) and, thereby, improving therapeutic decisions. This systematic review and meta-analysis synthesized the literature on the performance of these models. Searches of PubMed and EMBASE led to the identification of 10 relevant studies with 6106 unique patient encounters. Nine studies concerned ESBL prediction, and one focused on the prediction of carbapenemases. For the two ESBL model derivation studies, the discrimination performance showed sensitivities of 53-85% and specificities of 93-95%. Among the four ESBL model derivation and validation studies, the sensitivities were 43-88%, and the specificities were 77-99%. The sensitivity and specificity for the subsequent external validation studies were 7-37% and 88-96%, respectively. For the three external validation studies, only two models were evaluated across multiple studies, with a pooled AUROC of 65-71%, with one study omitting the sensitivity/specificity. Only two studies measured clinical utility through hypothetical therapy assessments. Given the limited evidence on their interventional application, it would be beneficial to further assess these or future models, to better understand their clinical utility and ensure their safe and impactful implementation.

Risk factors for predicting extended-spectrum β-lactamase-producing Enterobacterales (ESBLE) infections in non-urinary isolates

Background

With increases in antimicrobial resistance, it is crucial that patients receive appropriate antimicrobial therapy in a timely manner. Advancements in rapid diagnostics offer the ability to identify resistant organisms quickly. However, this technology is not always accessible and relies on correct specimen collection. While awaiting new microbiology methods, it may be beneficial to identify risk factors associated with common types of resistance. Specifically, extended-spectrum β-lactamase-producing Enterobacterales (ESBLE) are a rising threat globally.

Objective

The primary objective of this retrospective case-control analysis was to identify factors associated with non-urinary ESBLE versus non-ESBLE infections.

Design/Methods

Patient cultures were randomly selected based on type of culture (blood, bacterial, or exudate) and organism (E. coli, K. pneumoniae, or K. oxytoca) to provide a 1:1 ratio of ESBLE to non-ESBLE infections. Baseline demographics and potential risk factors (malignancy, cirrhosis, acute kidney injury (AKI), and diabetes) were collected for each patient encounter.

Results

In the univariate analysis, risk factors that achieved a significant difference included cirrhosis, AKI, presence of urinary catheter, presence of center venous catheter, history of an ESBLE infection, hospital-acquired infection, and recent fluoroquinolone, cephalosporin, or beta-lactam use. The multivariate analysis showed that four factors were independently associated with an ESBLE infection: cirrhosis, urinary catheter, central venous catheter, and history of ESBLE. Having a history of an ESBLE had the highest adjusted odds ratio (aOR 12.49; 95% CI 4.71-33.15, P < .001) of the four factors.

Conclusions

These results demonstrate that there may be benefit in incorporating select risk factors into clinical decision support tools to identify patients at highest risk of ESBLE infection.

Optimization of Empirical Antimicrobial Therapy in Enterobacterales Bloodstream Infection Using the Extended-Spectrum Beta-Lactamase Prediction Score

Clinical tools for the prediction of antimicrobial resistance have been derived and validated without examination of their implementation in clinical practice. This study examined the impact of utilization of the extended-spectrum beta-lactamase (ESBL) prediction score on the time to initiation of appropriate antimicrobial therapy for bloodstream infection (BSI). The quasi-experimental cohort study included hospitalized adults with BSI due to ceftriaxone-resistant (CRO-R) Enterobacterales at three community hospitals in Columbia, South Carolina, USA before (January 2010 to December 2013) and after (January 2014 to December 2019) implementation of an antimicrobial stewardship intervention. In total, 45 and 101 patients with BSI due to CRO-R Enterobacterales were included before and after the intervention, respectively. Overall, the median age was 66 years, 85 (58%) were men, and 86 (59%) had a urinary source of infection. The mean time to appropriate antimicrobial therapy was 78 h before and 46 h after implementation of the antimicrobial stewardship intervention (p = 0.04). Application of the ESBL prediction score as part of an antimicrobial stewardship intervention was associated with a significant reduction in time to appropriate antimicrobial therapy in patients with BSI due to CRO-R Enterobacterales. Utilization of advanced rapid diagnostics may be necessary for a further reduction in time to appropriate antimicrobial therapy in this population.

2023 Update on Sepsis and Septic Shock in Adult Patients: Management in the Emergency Department

BACKGROUND

Sepsis/septic shock is a life-threatening and time-dependent condition that requires timely management to reduce mortality. This review aims to update physicians with regard to the main pillars of treatment for this insidious condition.

METHODS

PubMed, Scopus, and EMBASE were searched from inception with special attention paid to November 2021-January 2023.

RESULTS

The management of sepsis/septic shock is challenging and involves different pathophysiological aspects, encompassing empirical antimicrobial treatment (which is promptly administered after microbial tests), fluid (crystalloids) replacement (to be established according to fluid tolerance and fluid responsiveness), and vasoactive agents (e.g., norepinephrine (NE)), which are employed to maintain mean arterial pressure above 65 mmHg and reduce the risk of fluid overload. In cases of refractory shock, vasopressin (rather than epinephrine) should be combined with NE to reach an acceptable level of pressure control. If mechanical ventilation is indicated, the tidal volume should be reduced from 10 to 6 mL/kg. Heparin is administered to prevent venous thromboembolism, and glycemic control is recommended. The efficacy of other treatments (e.g., proton-pump inhibitors, sodium bicarbonate, etc.) is largely debated, and such treatments might be used on a case-to-case basis.

CONCLUSIONS

The management of sepsis/septic shock has significantly progressed in the last few years. Improving knowledge of the main therapeutic cornerstones of this challenging condition is crucial to achieve better patient outcomes.

Risk Factors for Bloodstream Infections Due to ESBL-Producing Escherichia coli, Klebsiella spp., and Proteus mirabilis

(1) Background: Risk factors for extended-spectrum beta-lactamase (ESBL) infections could vary geographically. The purpose of this study was to identify local risk factors for ESBL production in patients with Gram-negative bacteremia. (2) Methods: This retrospective observational study included adult patients admitted from January 2019 to July 2021 and had positive blood cultures for E. coli, K. pneumoniae, K. oxytoca, and P. mirabilis. Patients with ESBL infection were matched to a non-ESBL-producing infection with the same organism. (3) Results: A total of 150 patients were included: 50 in the ESBL group and 100 in the non-ESBL group. Patients in the ESBL group had a longer length of stay (11 vs. 7 days, p < 0.001), but not increased mortality (14% vs. 15%, p = 0.87) Multivariate analysis identified the receipt of >1 antibiotic in the last 90 days as a risk factor for ESBL infection (OR = 3.448, 95% CI = 1.494-7.957; p = 0.004); (4) Conclusions: Recent antimicrobial use was identified as an independent risk factors for ESBL-producing Enterobacterales infections. Knowledge of this risk may improve empirical therapy and reduce inappropriate use.

Top Myths of Diagnosis and Management of Infectious Diseases in Hospital Medicine

Antimicrobial agents are among the most frequently prescribed medications during hospitalization. However, approximately 30% to 50% or more of inpatient antimicrobial use is unnecessary or suboptimal. Herein, we describe 10 common myths of diagnosis and management that often occur in the hospital setting. Further, we discuss supporting data to dispel each of these myths. This analysis will provide hospitalists and other clinicians with a foundation for rational decision-making about antimicrobial use and support antimicrobial stewardship efforts at both the patient and institutional levels.

Short- and long-term mortality in patients with urosepsis caused by Escherichia coli susceptible and resistant to 3rd generation cephalosporins

Background

The aim of this study was to compare short- and long-term mortality among patients with urosepsis caused by Escherichia coli susceptibile (EC-SC) and resistant (EC-RC) to 3rd generation cephalosporins.

Methods

A retrospective cohort study that included all patients with E. coli urosepsis admitted to a 700-bed hospital from January 2014 until December 2019. Mortality up to 30 days, 6 months and 1 year was assessed using logistic multivariate regression analysis and Cox regression analysis.

Results

A total of 313 adult were included, 195 with EC-SC and 118 patients with EC-RC. 205 were females (74%), mean age was 79 (SD 12) years. Mean Charlson score was 4.93 (SD 2.18) in the EC-SC group and 5.74 (SD 1.92) in the EC-RC group. Appropriate empiric antibiotic therapy was initiated in 245 (78.3%) patients, 100% in the EC-SC group but only 42.5% in the EC-RC group. 30-day mortality occurred in 12 (6.3%) of EC-SC group and 15 (12.7%) in the EC-RC group. Factors independently associated with 30-day mortality were Charlson score, Pitt bacteremia score, fever upon admission and infection with a EC-RC. Appropriate antibiotic therapy was not independently associated with 30-day mortality. Differences in mortality between groups remained significant one year after the infection and were significantly associated with the Charlson co-morbidity score.

Conclusions

Mortality in patients with urosepsis due to E. coli is highly affected by age and comorbidities. Although mortality was higher in the EC-RC group, we could not demonstrate an association with inappropriate empirical antibiotic treatment. Mortality remained higher at 6 months and 1 year long after the infection resolved but was associated mainly with co-morbidity.

Advances in novel antibiotics to treat multidrug-resistant gram-negative bacterial infections

Antimicrobial resistance is a growing threat to public health and an increasingly common problem for acute care physicians to confront. Several novel antibiotics have been approved in the past decade to combat these infections; however, physicians may be unfamiliar with how to appropriately utilize them. The purpose of this review is to evaluate novel antibiotics active against resistant gram-negative bacteria and highlight clinical information regarding their use in the acute care setting. This review focuses on novel antibiotics useful in the treatment of infections caused by resistant gram-negative organisms that may be seen in the acute care setting. These novel antibiotics include ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/cilistatin/relebactam, cefiderocol, plazomicin, eravacycline, and omadacycline. Acute care physicians should be familiar with these novel antibiotics so they can utilize them appropriately.

Improving Decision Making in Empiric Antibiotic Selection (IDEAS) for Gram-negative Bacteremia: A Prospective Clinical Implementation Study

BACKGROUND

Timely selection of adequate empiric antibiotics has become increasingly difficult due to rising resistance rates and the competing desire to apply antimicrobial stewardship (AMS) principles. Individualized clinical prediction models offer the promise of reducing broad-spectrum antibiotic use and preserving/improving adequacy of treatment, but few have been validated in the clinical setting.

METHODS

Multivariable models were used to predict the probability of susceptibility for gram-negative (GN) bacteria in bloodstream infections (bacteremia) to ceftriaxone, ciprofloxacin, ceftazidime, piperacillin-tazobactam, and meropenem. The models were combined with existing resistance-prediction methods to generate optimized and individualized suggestions for empiric therapy that were provided to prescribers by an AMS pharmacist. De-escalation of empiric antibiotics and adequacy of therapy were analyzed using a quasi-experimental design comparing two 9-month periods (pre- and postintervention) at a large academic tertiary care institution.

RESULTS

Episodes of bacteremia (n = 182) were identified in the preintervention and postintervention (n = 201) periods. Patients who received the intervention were more likely to have their therapy de-escalated (29 vs 21%; aOR = 1.77; 95% CI, 1.09-2.87; P = .02). The intervention also increased the proportion of patients who were on the narrowest adequate therapy at the time of culture finalization (44% in the control and 55% in the intervention group; aOR = 2.04; 95% CI, 1.27-3.27; P = .003). Time to adequate therapy was similar in the intervention and control groups (5 vs 4 hours; P = .95).

CONCLUSIONS

An AMS intervention, based on individualized predictive models for resistance, can influence empiric antibiotic selections for GN bacteremia to facilitate early de-escalation of therapy without compromising adequacy of antibiotic coverage.

Using Prior Culture Results to Improve Initial Empiric Antibiotic Prescribing: An Evaluation of a Simple Clinical Heuristic

BACKGROUND

A patient's prior cultures can inform the subsequent risk of infection from resistant organisms, yet prescribers often fail to incorporate these results into their empiric antibiotic selection. Given that timely initiation of adequate antibiotics has been associated with improved outcomes, there is an urgent need to address this gap.

METHODS

In order to better incorporate prior culture results in the selection of empiric antibiotics, we performed a pragmatic, prospective, hospital-wide intervention: (1) empiric antibiotic prescriptions were assessed for clinically significant discordance with the most recent methicillin-resistant Staphylococcus aureus (MRSA) surveillance swab, previous cultures for extended-spectrum beta-lactamases (ESBLs), and the most recent culture for a Gram-negative (GN) organism; and (2) if discordant, an antimicrobial stewardship pharmacist provided recommendations for alternative therapy. The impact was analyzed using a quasi-experimental design comparing two 9-month periods (pre- and postintervention) at a large academic, tertiary care institution.

RESULTS

Clinically significant discordance was identified 99 times in the preintervention period and 86 times in the intervention period. The proportion of patients that received concordant therapy increased from 73% (72/99) in the control group to 88% (76/86) in the intervention group (P = .01). The median time to concordant therapy was shorter in the intervention group than the control group (25 vs 55 hrs, respectively; P < .001; adjusted hazard ratio = 1.95 [95% confidence interval {CI}, 1.37-2.77; P < .001]). The median duration of unnecessary vancomycin therapy was reduced by 1.1 days (95% CI, .5-1.6 days; P < .001).

CONCLUSIONS

This intervention improved prescribing, with a shorter time to concordant therapy and an increased proportion of patients receiving empiric therapy concordant with prior culture results. The use of unnecessary vancomycin was also reduced.

Validation of Available Extended-Spectrum-Beta-Lactamase Clinical Scoring Models in Predicting Drug Resistance in Patients with Enteric Gram-Negative Bacteremia Treated at South Texas Veterans Health Care System

Extended-spectrum-beta-lactamase (ESBL)-producing Enterobacteriaceae are increasingly common; however, predicting which patients are likely to be infected with an ESBL pathogen is challenging, leading to increased use of carbapenems. To date, five prediction models have been developed to distinguish between patients infected with ESBL pathogens. The aim of this study was to validate and compare each of these models to better inform antimicrobial stewardship. This was a retrospective cohort study of patients with Gram-negative bacteremia treated at the South Texas Veterans Health Care System over 3 months from 2018 to 2019. We evaluated isolate, clinical syndrome, and score variables for the five published prediction models/scores: Italian "Tumbarello," Duke, University of South Carolina (USC), Hopkins clinical decision tree, and modified Hopkins. Each model was assessed using the area under the receiver operating characteristic curve (AUROC) and Pearson correlation. One hundred forty-five patients were included for analysis, of which 20 (13.8%) were infected with an ESBL Escherichia coli or Klebsiella spp. The most common sources of infection were genitourinary (55.8%) and gastrointestinal/intraabdominal (24.1%), and the most common pathogen was E. coli (75.2%). The prediction model with the strongest discriminatory ability (AUROC) was Tumbarello (0.7556). The correlation between prediction model score and percent ESBL was strongest with the modified Hopkins model (R ² = 0.74). In this veteran population, the modified Hopkins and Duke prediction models were most accurate in discriminating between Gram-negative bacteremia patients when considering both AUROC and correlation. However, given the moderate discriminatory ability, many patients with ESBL Enterobacteriaceae (at least 25%) may still be missed empirically.

Effect of N-Acetylcysteine Administration on 30-Day Mortality in Critically Ill Patients with Septic Shock Caused by Carbapenem-Resistant Klebsiella pneumoniae and Acinetobacter baumannii: A Retrospective Case-Control Study

Carbapenem-resistant Klebsiella pneumoniae (CR-Kp) and Acinetobacter baumannii (CR-Ab) represent important cause of severe infections in intensive care unit (ICU) patients. N-Acetylcysteine (NAC) is a mucolytic agent with antioxidant and anti-inflammatory properties, showing also in-vitro antibacterial activity. Aim was to evaluate the effect on 30-day mortality of the addition of intravenous NAC to antibiotics in ICU patients with CR-Kp or CR-Ab septic shock. A retrospective, observational case:control study (1:2) in patients with septic shock caused by CR-Kp or CR-Ab hospitalized in two different ICUs was conducted. Cases included patients receiving NAC plus antimicrobials, controls included patients not receiving NAC. Cases and controls were matched for age, SAPS II, causative agent and source of infection. No differences in age, sex, SAPS II score or time to initiate definitive therapy were observed between cases and controls. Pneumonia and bacteremia were the leading infections. Overall, mortality was 48.9% (33.3% vs. 56.7% in cases and controls, p = 0.05). Independent risk factors for mortality were not receiving NAC (p = 0.002) and CR-Ab (p = 0.034) whereas therapy with two in-vitro active antibiotics (p = 0.014) and time to initial definite therapy (p = 0.026) were protective. NAC plus antibiotics might reduce the 30-day mortality rate in ICU patients with CR-Kp and CR-Ab septic shock.

Characterization of predictors of ESBL-producing enterobacteriaceae in urine cultures of emergency department patients

STUDY OBJECTIVE

With increasing prevalence of extended-spectrum beta-lactamase-producing enterobacteriaceae (ESBLE), more reliable identification of predictors for ESBLE urinary tract infection (UTI) in the emergency department (ED) is needed. Our objective was to evaluate risk factors and their predictive ability for ED patients with ESBLE UTI.

METHODS

This was a retrospective case-control study at an urban academic medical center. Microbiology reports identified adult ED patients with positive urine cultures from 2015-2018. Inclusion criteria were diagnosis of UTI with monomicrobial enterobacteriaceae culture growth. Exclusions were cultures with carbapenemase-resistant enterobacteriaceae or urinary colonization. Collected variables included demographics, comorbidities, and recent medical history. Patient disposition, urine culture susceptibilities, presence of ESBLE, empiric antibiotics, and therapy modifications were collected. Patients were stratified based on ESBLE status and analyzed via descriptive statistics. The data were divided into 2 parts: the first used to identify possible predictors of ESBLE UTI and the second used to validate an additive scoring system.

RESULTS

Of 466 patients, 16.3% had ESBLE urine culture growth and 83.7% did not; 39.5% of ESBLE patients required antibiotic therapy modification, as compared to 6.4% of ESBLE negative patients (odds ratio [OR] 9.5; confidence interval [CI] 8.9-10.1). Independent predictors of ESBLE UTI were IV antibiotics within 1 year (OR 5.4; CI 2.1-12.8), surgery within 90 days (OR 6.4; CI 1.5-27.8), and current refractory UTI (OR 8.5; CI 2.0-36.6).

CONCLUSION

Independent predictors of ESBLE UTI in emergency department patients included IV antibiotics within 1 year, surgery within 90 days, and current refractory UTI.

Deep learning model for prediction of extended-spectrum beta-lactamase (ESBL) production in community-onset Enterobacteriaceae bacteraemia from a high ESBL prevalence multi-centre cohort

Adequate empirical antimicrobial coverage is instrumental in clinical management of community-onset Enterobacteriaceae bacteraemia in areas with high ESBL prevalence, while balancing the risk of carbapenem overuse and emergence of carbapenem-resistant organisms. It is unknown whether machine learning offers additional advantages to conventional statistical methods in prediction of ESBL production. To develop a validated model to predict ESBL production in Enterobacteriaceae causing community-onset bacteraemia. 5625 patients with community-onset bacteraemia caused by Escherichia coli, Klebsiella species and Proteus mirabilis during 1 January 2015-31 December 2019 from three regional hospitals in Hong Kong were included in the analysis, after exclusion of blood cultures obtained beyond 48 h of admission. The prevalence of ESBL-producing Enterobacteriaceae was 23.7% (1335/5625). Deep neural network and other machine learning algorithms were compared against conventional statistical model via multivariable logistic regression. Primary outcomes compared consisted of predictive model area under curve of receiver-operator characteristic curve (AUC), and macro-averaged F1 score. Secondary outcomes included sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Deep neural network yielded an AUC of 0.761 (95% CI 0.725-0.797) and F1 score of 0.661 (95% CI 0.633-0.689), which was superior to logistic regression (AUC 0.667 (95% CI 0.627-0.707), F1 score 0.596 (95% CI 0.567-0.625)). Deep neural network had a specificity of 91.5%, sensitivity of 37.5%, NPV of 82.5%, and PPV of 57.9%. Deep neural network is superior to logistic regression in predicting ESBL production in Enterobacteriaceae causing community-onset bacteraemia in high-ESBL prevalence area. Machine learning offers clinical utility in guiding judicious empirical antibiotics use.

Independent, external validation of clinical prediction rules for the identification of extended-spectrum β-lactamase-producing Enterobacterales, University Hospital Basel, Switzerland, January 2010 to December 2016

Background

Algorithms for predicting infection with extended-spectrum β-lactamase-producing Enterobacterales (ESBL-PE) on hospital admission or in patients with bacteraemia have been proposed, aiming to optimise empiric treatment decisions.

Aim

We sought to confirm external validity and transferability of two published prediction models as well as their integral components.

Methods

We performed a retrospective case–control study at University Hospital Basel, Switzerland. Consecutive patients with ESBL-producing Escherichia coli or Klebsiella pneumoniae isolated from blood samples between 1 January 2010 and 31 December 2016 were included. For each case, three non-ESBL-producing controls matching for date of detection and bacterial species were identified. The main outcome measure was the ability to accurately predict infection with ESBL-PE by measures of discrimination and calibration.

Results

Overall, 376 patients (94 patients, 282 controls) were analysed. Performance measures for prediction of ESBL-PE infection of both prediction models indicate adequate measures of calibration, but poor discrimination (area under receiver-operating curve: 0.627 and 0.651). History of ESBL-PE colonisation or infection was the single most predictive independent risk factor for ESBL-PE infection with high specificity (97%), low sensitivity (34%) and balanced positive and negative predictive values (80% and 82%).

Conclusions

Applying published prediction models to institutions these were not derived from, may result in substantial misclassification of patients considered as being at risk, potentially leading to wrong allocation of antibiotic treatment, negatively affecting patient outcomes and overall resistance rates in the long term. Future prediction models need to address differences in local epidemiology by allowing for customisation according to different settings.

Use of Antibiotics in Chronic Obstructive Pulmonary Disease: What is Their Current Role in Older Patients?

Chronic obstructive pulmonary disease (COPD) has considerable morbidity and mortality in the older adult population. The role of antibiotics in the management of acute exacerbations of COPD (AECOPD) is currently evolving. Despite only mild benefits, most patients with AECOPD in ambulatory settings receive antibiotics based on clinical criteria. Utilization of point-of-care C-reactive protein (CRP) has reduced antibiotic prescriptions by 20% without compromising clinical outcomes. A strict protocol allowing antibiotic use only in patients with clinical criteria and CRP ≥ 20 mg/L has the potential to reduce antibiotic prescriptions for AECOPD in ambulatory settings by nearly 50%. Amoxicillin and doxycycline are commonly prescribed for AECOPD based on a favorable benefit-to-risk ratio. Prophylactic antibiotics have also been used in selected patients with severe COPD and frequent exacerbations. The use of continuous or intermittent azithromycin has demonstrated efficacy in reducing the frequency of AECOPD in this population; however, this approach has potential for the development of antibiotic resistance and adverse effects. The use of azithromycin prophylaxis in older patients with frequent AECOPD should be determined on a case-by-case basis after careful review, discussion, and counseling of the potential benefits and risks. The role of continuous doxycycline and pulsed moxifloxacin prophylaxis for frequent AECOPD remains controversial.

Management of Gram-Negative Bloodstream Infections in the Era of Rapid Diagnostic Testing: Impact With and Without Antibiotic Stewardship

Background

Verigene Blood-Culture Gram-Negative is a rapid diagnostic test (RDT) that detects gram-negatives (GNs) and resistance within hours from gram stain. The majority of the data support the use of RDTs with antimicrobial stewardship (AMS) intervention in gram-positive bloodstream infection (BSI). Less is known about GN BSI.

Methods

This was a retrospective quasi-experimental (nonrandomized) study of adult patients with RDT-target GN BSI comparing patients pre-RDT/AMS vs post-RDT/pre-AMS vs post-RDT/AMS. Optimal therapy was defined as appropriate coverage with the narrowest spectrum, accounting for source and co-infecting organisms. Time to optimal therapy was analyzed using Kaplan-Meier and multivariable Cox proportional hazards regression.

Results

Eight-hundred thirty-two patients were included; 237 pre-RDT/AMS vs 308 post-RDT/pre-AMS vs 237 post-RDT/AMS, respectively. The proportion of patients on optimal antibiotic therapy increased with each intervention (66.5% vs 78.9% vs 83.2%; P < .0001). Time to optimal therapy (interquartile range) decreased with introduction of RDT: 47 (7.9–67.7) hours vs 24.9 (12.4–55.2) hours vs 26.5 (10.3–66.5) hours (P = .09). Using multivariable modeling, infectious diseases (ID) consult was an effect modifier. Within the ID consult stratum, controlling for source and ICU stay, compared with the pre-RDT/AMS group, both post-RDT/pre-AMS (adjusted hazard ratio [aHR], 1.34; 95% CI, 1.04–1.72) and post-RDT/AMS (aHR, 1.28; 95% CI, 1.01–1.64), improved time to optimal therapy. This effect was not seen in the stratum without ID consult.

Conclusions

With the introduction of RDT and AMS, both proportion and time to optimal antibiotic therapy improved, especially among those with an existing ID consult. This study highlights the beneficial role of RDTs in GN BSI.

Online availability of fish antibiotics and documented intent for self-medication

Self-medication and antibiotic utilization without healthcare oversight may lead to delayed appropriate treatment, transmission of communicable infections, untoward adverse events, and contribute to antimicrobial resistance. Previous data suggest people obtain over-the-counter (OTC) animal antibiotics for their personal use. This study examined the availability of OTC fish antibiotics online and the documented intent for self-medication. The authors conducted a web-based cross-sectional study using Google search engine to identify vendor websites selling fish antibiotics in the United States. Vendor websites were included if product information, consumer reviews, and comments were publicly available. Nine fish antibiotics were chosen due to their possibility of having consequences to human misuse. The cost and availability of fish antibiotics was recorded. The proportion of reviews and comments related to human consumption was calculated. Consumer review traffic based on “likes” and “dislikes” received was compared between human- and non-human consumption-related reviews. Selected fish antibiotics were purchased and evaluated for physical appearance and compared to FDA-approved available equivalents. We found 24 website vendors with online ordering available for OTC fish antibiotics. Cost varied significantly by antibiotic and quantity ranging from USD $8.99 to $119.99. There were 2,288 reviews documented for the 9 selected antibiotics being sold. Among consumer reviews, 2.4% were potentially associated with human consumption. Human consumption-related reviews constituted 30.2% of all “likes” received and 37.5% of all “dislikes” received. Human consumption-related reviews received an average of 9.2 likes compared to 0.52 likes for non-human consumption-related reviews. The 8 fish antibiotics purchased were consistent with FDA-approved equivalents in physical appearance. Although infrequent, antibiotics intended for fish use are being purchased online without a prescription for self-medication to circumvent professional medical care. Reviews related to human consumption generate significant online traffic compared to reviews unrelated to human consumption.

Role of Early De-escalation of Antimicrobial Therapy on Risk of Clostridioides difficile Infection Following Enterobacteriaceae Bloodstream Infections

BACKGROUND

There is a paucity of data on the effect of early de-escalation of antimicrobial therapy on rates of Clostridioides difficile infection (CDI). This retrospective cohort study evaluated impact of de-escalation from antipseudomonal β-lactam (APBL) therapy within 48 hours of Enterobacteriaceae bloodstream infections (BSIs) on 90-day risk of CDI.

METHODS

Adult patients hospitalized for >48 hours for treatment of Enterobacteriaceae BSI at Palmetto Health hospitals in Columbia, South Carolina, from 1 January 2011 through 30 June 2015 were identified. Multivariable Cox proportional hazards regression was used to examine time to CDI in patients who received >48 hours or ≤48 hours of APBL for empirical therapy of Enterobacteriaceae BSI after adjustment for the propensity to receive >48 hours of APBL.

RESULTS

Among 808 patients with Enterobacteriaceae BSI, 414 and 394 received >48 and ≤48 hours of APBL, respectively. Incidence of CDI was higher in patients who received >48 hours than those who received ≤48 hours of APBL (7.0% vs 1.8%; log-rank P = .002). After adjustment for propensity to receive >48 hours of APBL and other variables in the multivariable model, receipt of >48 hours of APBL (hazard ratio [HR], 3.56 [95% confidence interval {CI}, 1.48-9.92]; P = .004) and end-stage renal disease (HR, 4.27 [95% CI, 1.89-9.11]; P = .001) were independently associated with higher risk of CDI.

CONCLUSIONS

The empirical use of APBL for >48 hours was an independent risk factor for CDI. Early de-escalation of APBL using clinical risk assessment tools or rapid diagnostic testing may reduce the incidence of CDI in hospitalized adults with Enterobacteriaceae BSIs.

Risk stratification for multidrug-resistant Gram-negative infections in ICU patients

PURPOSE OF REVIEW

Antimicrobial resistance among Gram-negative microorganisms has alarmingly increased in the past 10 years worldwide. Infections caused by these microorganisms are difficult to treat, especially in critically ill patients.The present review examines how to accurately predict which patients carry a greater risk of colonization or infection on which to base the timely choice of an effective empirical antibiotic treatment regimen and avoid antibiotic overuse.

RECENT FINDINGS

There are many risk factors for acquiring one of many multidrug-resistant Gram-negative microorganisms (MDR-GN); however, scores anticipating colonization, infection among those colonized, or mortality among those infected have a variable accuracy. Accuracy of scores anticipating colonization is low. Scores predicting infections among colonized patients are, in general, better, and ICU patients infected with MDR-GN have a worse prognosis than those infected by non-resistant microorganisms. Scores are, in general, better at excluding patients.

SUMMARY

Despite these limitations, scores continue to gain popularity including those by Giannella, Tumbarello, Johnson, or the scores INCREMENT carbapenem-producing Enterobacteriaceae score, Cano, Tartof, or CarbaSCORE.

Minimizing Time to Optimal Antimicrobial Therapy for Enterobacteriaceae Bloodstream Infections: A Retrospective, Hypothetical Application of Predictive Scoring Tools vs Rapid Diagnostics Tests

Background

Bloodstream infections (BSIs) due to ceftriaxone (CRO)-resistant Enterobacteriaceae are associated with delays in time to appropriate therapy and worse outcomes compared with infections due to susceptible isolates. However, treating all at-risk patients with empiric carbapenem therapy risks overexposure. Strategies are needed to appropriately balance these competing interests. The purpose of this study was to compare 4 methods for achieving this balance.

Methods

This was a retrospective hypothetical observational study of patients at the Detroit Medical Center with monomicrobial BSIs due to E. coli, K. oxytoca, K. pneumoniae, or P. mirabilis. This study compared the effectiveness of 4 methods to predict CRO resistance at the time of organism isolation. Three methods were based on applying published extended-spectrum beta-lactamase (ESBL) scoring tools. The fourth method was based on the presence or absence of the CTX-M marker from Verigene.

Results

Four hundred fifty-one Enterobacteriaceae BSIs were included, 73 (16%) of which were CRO-resistant. Verigene accurately predicted ceftriaxone susceptibility for 97% of isolates, compared with 70%-81% using the scoring tools (P < .001). Verigene was associated with fewer cases of treatment with CRO when the isolate was CRO-resistant (15% vs 63%-71% with scoring tools) and fewer cases of overtreatment with a carbapenem for CRO-susceptible strains (0.3% vs 10%-12%).

Conclusions

Verigene significantly outperformed published ESBL scoring tools for identifying CRO-resistant Enterobacteriaceae BSI. Institutions should validate scoring tools before implementation. Stewardship programs should consider adoption of rapid diagnostic tests to optimize early therapy.

Quantifying risk of disease due to extended-spectrum β-lactamase producing Enterobacteriaceae in patients who are colonized at ICU admission

BACKGROUND

The prevalence of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) has globally increased and spread to the community. No clinical score is available to select carriers in whom these organisms can be empirically targeted at ICU admission.

METHODS

We prospectively assessed between 2009 and 2017 the prevalence of ESBL-PE infection in carriers at ICU admission. A logistic regression was used to determine independent risk factors associated with ESBL-PE infection, and to build a clinical risk score.

RESULTS

Of the 8,061 admissions over the study 7-year period, 745 (9%) patients were ESBL-PE carriers at admission, of whom 395 had infections at ICU admission including 59 (15%) who had culture-proven ESBL-PE related infection. By multivariable analysis, age >60 years, cirrhosis, being on broad-spectrum antibiotics within the past three months, urinary or intra-abdominal source of infection, and the absence of chronic pulmonary disease, were the five independent factors associated with ESBL-PE infection in carriers. A clinical risk score ranging from 0 to 7 was built based on these variables, with an area under the receiver operating characteristic curve (ROC) of 0.82 (95% CI 0.78-0.86); p <0.001. The prevalence of ESBL-PE infection for clinical risk scores of 0-1, 2-3, 4-5, or 6-7 was 0%, 4%, 26%, and 49%, respectively. The negative predictive value when Mondor ESBL risk score is <4 was 97%.

CONCLUSION

ESBL-PE related infection was not common in carriers at ICU admission. A clinical risk score may spare ESBL-PE carriers with lower risk of ESBL-PE infection at ICU admission unnecessary empiric carbapenem therapy.

Proposal of a clinical score to stratify the risk of multidrug-resistant gram-negative rods bacteremia in cancer patients

Introduction

Multidrug-resistant gram-negative rods (MDR GNR) represent a growing threat for patients with cancer. Our objective was to determine the characteristics of and risk factors for MDR GNR bacteremia in patients with cancer and to develop a clinical score to predict MDR GNR bacteremia.

Material and Methods

Multicenter prospective study analyzing initial episodes of MDR GNR bacteremia. Risk factors were evaluated using a multiple logistic regression (forward-stepwise selection) analysis including variables with a p < 0.10 in univariate analysis.

Results

394 episodes of GNR bacteremia were included, with 168 (42.6 %) being MDR GNR. Five variables were identified as independent risk factors: recent antibiotic use (OR = 2.8, 95 % CI 1.7–4.6, p = 0.001), recent intensive care unit admission (OR = 2.9, 95 % CI 1.1–7.8, p = 0.027), hospitalization ≥ 7 days prior to the episode of bacteremia (OR = 3.5, 95 % CI 2–6.2, p = 0.005), severe mucositis (OR = 5.3, 95 % CI 1.8–15.6, p = 0.002), and recent or previous colonization/infection with MDR GNR (OR = 2.3, 95 % CI 1.2–4.3, p = 0.028). Using a cut-off value of two points, the score had a sensitivity of 66.07 % (95 % CI 58.4–73.2 %), a specificity of 77.8 % (95 % CI 71.4–82.7 %), a positive predictive value of 68 % (95 % CI 61.9–73.4 %), and a negative predictive value of 75.9 % (95 % CI 71.6–79.7 %). The overall performance of the score was satisfactory (AUROC 0.78; 95 % CI 0.73-0.82). In the cases with one or none of the risk factors identified, the negative likelihood ratio was 0.18 and the post-test probability of having MDR GNR was 11.68 %.

Conclusions

With the growing incidence of MDR GNR as etiologic agents of bacteremia in cancer patients, the development of this score could be a potential tool for clinicians.

Empirical fluoroquinolones versus broad-spectrum beta-lactams for Gram-negative bloodstream infections in the absence of antimicrobial resistance risk factors

OBJECTIVES

Increasing antimicrobial resistance rates limit empirical antimicrobial treatment options for Gram-negative bloodstream infections (GN-BSI). However, antimicrobial resistance may be predicted based on patient-specific risk factors using precision medicine concepts. This retrospective, 1:2 matched cohort examined clinical outcomes in hospitalized adults without major risk factors for antimicrobial resistance receiving empirical fluoroquinolones or broad-spectrum beta-lactams (BSBL) for GN-BSI at Prisma Health-Midlands hospitals in Columbia, SC, USA from January 2010 through June 2015.

METHODS

Multivariable logistic regression was used to examine early treatment failure at 72-96 h from GN-BSI. Cox proportional hazards regression was used to examine 28-day mortality and hospital length of stay (HLOS).

RESULTS

Among 74 and 148 patients receiving empirical fluoroquinolones and BSBL for GN-BSI, respectively, median age was 68 years, 159 (72%) were women, and 152 (68%) had a urinary source of infection. Early treatment failure rates were comparable in fluoroquinolone and BSBL groups (27% vs. 30%, respectively, odds ratio 0.82, 95% confidence intervals [CI] 0.43-1.54, P = 0.53), as well as 28-day mortality (8.9% vs. 9.7%, respectively, hazards ratio [HR] 0.74, 95% CI 0.26-1.90, P = 0.54). Median HLOS was 6.1 days in the fluoroquinolone group and 7.1 days in the BSBL group (HR 0.73, 95% CI 0.54-0.99, P = 0.04). Transition from intravenous to oral therapy occurred sooner in the fluoroquinolone group than in the BSBL group (3.0 vs. 4.9 days, P < 0.001).

CONCLUSIONS

In the absence of antimicrobial resistance risk factors, fluoroquinolones provide an additional empirical treatment option to BSBL for GN-BSI. Shorter HLOS in the fluoroquinolone group may be due to earlier transition from intravenous to oral antimicrobial therapy.

An easy-to-use scoring system for predicting bacteraemia with third-generation cephalosporin-resistant Enterobacterales in a low-resistance setting

Background: The incidence of third-generation cephalosporin-resistant Enterobacterales (3GCR-E) is increasing and a growing number of patients risk receiving inappropriate initial antibiotic treatment. Published scoring systems for predicting 3GCR-E bacteraemia are mostly based on studies from countries with a high incidence. In this study, we aimed to create an easy-to-use scoring system for predicting bacteraemia with these bacteria in a low-resistance setting.Materials and methods: Factors associated with 3GCR-E were studied retrospectively in a cohort of patients with Enterobacterales bacteraemia using uni- and multivariate analysis. A scoring system was constructed and was validated in a separate cohort of patients with Enterobacterales bacteraemia.Results: The derivation cohort comprised 625 cases of Enterobacterales bacteraemia. Three variables (previous hospital care abroad, 3GCR-E in a previous blood or urine culture and 3GCR-E in a previous rectal swab culture) were significantly associated with 3GCR-E bacteraemia. A scoring system, where at least one positive parameter equalled a positive score, was studied in the validation cohort, which comprised 675 cases of Enterobacterales bacteraemia. The sensitivity and specificity of the score were 53% and 95%, respectively. Positive and negative predictive values were 38% and 97%, respectively.Conclusions: This study presents an easy-to-use scoring system for predicting bacteraemia with 3GCR-E. The performance of the score is similar to that of several other, more complicated, scoring systems, developed in countries with higher rates of resistance. The minimal extra effort required to use this new score could facilitate its introduction into clinical routine.

Molecular detection and antibiotic resistance pattern of extended-spectrum beta-lactamase producing Escherichia coli in a Tertiary Hospital in Enugu, Nigeria

BACKGROUND

The use of antibiotic agents in the treatment of infectious diseases has greatly contributed to the decrease in morbidity and mortality, but these great advances in treatment are being undermined by the rapidly increasing antimicrobial resistant organisms. Extended-spectrum beta-lactamases are enzymes hydrolyzing the beta lactam antibiotics, including third generation cephalosporins and monobactams but not cephamycins and carbapenems. They pose a serious global health threat and have become a challenge for health care providers. The aim of this research was to assess the prevalence of extended-spectrum beta-lactamase producing Escherichia coli in University of Nigeria Teaching Hospital Ituku-Ozalla Enugu and to detect the risk factors for acquisition of the resistant organism. To proffer advice on antibiotic stewardship in clinical practice and public health interventions, to curb the spread of the resistant organisms in the hospital.

RESULTS

Out of the 200 E. coli isolates, 70 (35.00%) were confirmed positive for extended-spectrum beta-lactamase production. Fifty-three (75.7%) were from hospital acquired infections. All the isolates were resistant to ampicillin, tetracycline and chloramphenicol while 68 (97.14%) of the 70 isolates were susceptible to imipenem. BlaTEM, blaSHV and blaTEM were detected in 66 (94%) of the 70 isolates. The ESBL bla genes detected were blaCTX-M (n = 26; 37.14%), blaTEM (n = 7; 10.00%), blaSHV (n = 2; 2.86%), blaCTX-M/TEM (n = 7; 10.0%), blaCTX-M/SHV (n = 14; 20.0%) and blaCTX-M/TEM/SHV (n = 10; 14.29%). The three bla genes were not detected in 4 (5.71%) of the isolates. Recent surgery, previous antibiotic and intensive care unit admission were the associated risk factors to infections caused by extended-spectrum beta-lactamase producing E. coli.

CONCLUSION

There is a high rate of infections caused by extended-spectrum beta-lactamase producing E. coli. Recent surgery, previous antibiotic and intensive care unit admission were associated risk factors.

Carbapenem Treatment and Outcomes Among Patients With Culture-Positive Complicated Intra-abdominal Infections in US Hospitals: A Retrospective Cohort Study

BACKGROUND

Carbapenems are a frequent firstline therapy in complicated intra-abdominal infections (cIAIs). We examined the microbiology, epidemiology, and outcomes among patients hospitalized in the United States with culture-positive cIAIs in the context of their exposure to empiric carbapenem treatment (ECT).

METHODS

We performed a multicenter retrospective cohort study of Premier database of ~180 hospitals, 2013-2017. Using an International Classification of Diseases (ICD)-9/10-based algorithm, we identified all culture-positive adult patients hospitalized with cIAI and examined their microbiology, epidemiology, and outcomes.

RESULTS

Among 4453 patients with cIAIs, 3771 (84.7%) had a gram-negative (GN) and 1782 (40.0%) a gram-positive organism; 1185 (26.6%) received ECT. Compared with those on non-ECT, patients on ECT were less frequently admitted from home (82.5% vs 86.0%) or emergently (76.0% vs 81.4%; P < .05 for each); E. coli were less frequent, whereas P. aeruginosa and Enterococcus spp. were more prevalent and resistance to third-generation cephalosporins (C3R; 10.1% vs 5.1%; P < .001) and carbapenems (CR; 3.6% vs 1.2%; P < .001) was more common. In adjusted analyses, ECT was associated with no rise in mortality, shorter postinfection length of stay (-0.59 days; 95% confidence interval [CI], -1.15 to -0.03), but higher postinfection costs ($3844; 95% CI, $1921 to $5767) and risk of Clostridioides difficile (odds ratio, 2.15; 95% CI, 1.02 to 4.50).

CONCLUSIONS

Among patients hospitalized with cIAI, the majority were gram-negative. Despite a 10% prevalence of C3R, fully one-quarter of all empiric regimens contained a carbapenem. ECT was a marker for slightly lower postinfection length of stay, but higher costs and risk of hospital complications.

Extended spectrum β-lactamase producing enterobacteriaceae: carbapenem sparing options

Introduction: Carbapenems have an important place in our antibiotic armamentarium and have been trusted to effectively treat infections caused by ESBL-producing Enterobacteriaceae for many years. However, the utility of carbapenems has been compromised by the emergence of resistance especially in Enterobacteriaceae. Therefore, carbapenem-sparing alternative antibiotics are of extreme importance in clinical practice.Areas covered: We reviewed studies addressing currently available antibiotic options used as both empiric and definitive therapy for the treatment of infections due to ESBL-producing Enterobacteriaceae published in the PubMed/MEDLINE, Web of Science and Scopus databases without any date restriction. Current treatment alternatives included beta-lactam/beta-lactamase inhibitor combinations, cefepime, cephamycins, fluoroquinolones, aminoglycosides, fosfomycin, pivmecillinam, temocillin and, various oral alternative agents. We also summarized the clinical and molecular epidemiology, early prediction methods and impact of initial empirical therapy and de-escalation approach for ESBL-producing Enterobacteriaceae infections.Expert opinion: The current literature would endorse the carbapenem utilization for patients with severe and high inoculum-high risk infections. However, for milder infections particularly for urinary tract infections, various carbapenem-sparing antibiotics can be considered in selected cases. For infections including easily drainable intra-abdominal infections and catheter-related infections in which catheter removal is readily available more reliable data are needed to recommend non-carbapenem antibiotics confidently.

Prediction of trimethoprim/sulfamethoxazole resistance in community-onset urinary tract infections

OBJECTIVES

This study aimed to predict trimethoprim/sulfamethoxazole (SXT) resistance in patients with community-onset urinary tract infection (UTI) due to Enterobacteriaceae based on patient-specific risk factors.

METHODS

This was a retrospective case-control study in Prisma Health facilities in central South Carolina, USA, including three community hospitals, affiliated emergency departments and ambulatory clinics, including adult patients with community-onset UTI due to Enterobacteriaceae (1 April 2015 to 29 February 2016). Multivariate logistic regression was used to examine risk factors for SXT resistance.

RESULTS

Among 351 unique patients with community-onset UTI, 71 (20.2%) had SXT-resistant Enterobacteriaceae urinary isolates. Overall, median age was 64 years and 252 (71.8%) were female. A multivariate model identified prior urinary infection/colonisation with SXT-resistant Enterobacteriaceae (OR=8.58, 95% CI 3.92-18.81; P<0.001) and SXT use within past 12 months (OR=2.58, 95% CI 1.13-5.89; P=0.02) as predictors of SXT resistance among urinary isolates. Most patients with UTI (285; 81.2%) had no risk factors for SXT resistance. SXT resistance rates increased from 13% in the absence of risk factors to 31% in patients with prior SXT use, 66% in those with prior urinary infection/colonisation with SXT-resistant Enterobacteriaceae and 73% in the presence of both risk factors.

CONCLUSION

SXT resistance in Enterobacteriaceae urinary isolates may be predicted based on prior urine culture results and SXT use within the previous year. Utilisation of a patient-specific antibiogram may allow empirical SXT use in patients with community-onset UTI in the absence of risk factors for resistance.

Syndrome-specific versus prospective audit and feedback interventions for reducing use of broad-spectrum antimicrobial agents

BACKGROUND

Antimicrobial use (AU) of antipseudomonal β-lactams (APBL) has significantly increased over the past decade in US hospitals. This retrospective cohort study compares 2 common antimicrobial stewardship strategies, syndrome-specific interventions and antimicrobial postprescription prospective audit and feedback (PAF), in reducing AU of APBL at a large community-teaching hospital.

METHODS

Four antimicrobial stewardship interventions targeting APBL were serially introduced, including 2 syndrome-specific interventions (bloodstream and intra-abdominal infections) and 2 PAF interventions (carbapenems and piperacillin/tazobactam). Multivariable linear regression was used to examine overall AU of APBL and audited antimicrobial agents.

RESULTS

Overall AU of APBL declined from 92.4-69.1 days of therapy (DOT) per 1,000 patient-days between February 2013 and July 2017 (P < .001). Both syndrome-specific interventions were associated with significant reduction in AU of APBL (-7.7 [95% confidence interval (CI): -11.5, -4.0] and -6.0 [95% CI: -9.7, -2.3] DOT per 1,000 patient-days) for bloodstream and intra-abdominal infections, respectively). No significant change in overall AU of APBL was observed after implementation of PAF interventions for carbapenems (-1.4 [95% CI: -7.4, 4.6] DOT per 1,000 patient-days) or piperacillin/tazobactam (0.9 [95% CI: -3.7, 5.4] DOT per 1,000 patient-days).

CONCLUSIONS

Implementation of syndrome-specific interventions was followed by significant reduction in AU of APBL in this population. Despite reducing AU of targeted agents, neither PAF intervention contributed to overall observed decline in APBL use, likely due to compensatory increase in using other APBL.

Enteropathogenetic nosocomial infections: predisposing clinical characteristics and risk of recurrent infections

Nosocomial infections caused by Clostridium difficile, CP-Kp, ESBL-E or Candida spp. are usually associated with a high mortality rate. In this retrospective study, we evaluated the association between the patient characteristics and the risk of development of nosocomial BSI due to Candida or CP-Kp or ESBL-E. Moreover, we described the cumulative incidence of recurrent infections according to each group of nosocomial BSI. Enteral or parenteral nutrition and indwelling CVC at time of diagnosis were associated with an increased risk of candidemia or CP-Kp over ESBL-E and CDI. ESBL-E BSI was higher in patients undergoing hemodialysis, hematological stem cell transplant and neutropenic patients. The cumulative incidence for recurrent infections was higher for CP-Kp BSI and lower for candidemia. Our data highlight a different role of single patient comorbidities in the development of infections and the higher incidence of recurrent infections in CP-Kp BSI.

Direct Measurement of Performance: A New Era in Antimicrobial Stewardship

For decades, the performance of antimicrobial stewardship programs (ASPs) has been measured by incidence rates of hospital-onset Clostridioides difficile and other infections due to multidrug-resistant bacteria. However, these represent indirect and nonspecific ASP metrics. They are often confounded by factors beyond an ASP’s control, such as changes in diagnostic testing methods or algorithms and the potential of patient-to-patient transmission. Whereas these metrics remain useful for global assessment of healthcare systems, antimicrobial use represents a direct metric that separates the performance of an ASP from other safety and quality teams within an institution. The evolution of electronic medical records and healthcare informatics has made measurements of antimicrobial use a reality. The US Centers for Disease Control and Prevention’s initiative for reporting antimicrobial use and standardized antimicrobial administration ratio in hospitals is highly welcomed. Ultimately, ASPs should be evaluated based on what they do best and what they can control, that is, antimicrobial use within their own institution. This narrative review critically appraises existing stewardship metrics and advocates for adopting antimicrobial use as the primary performance measure. It proposes novel formulas to adjust antimicrobial use based on quality of care and microbiological burden at each institution to allow for meaningful inter-network and inter-facility comparisons.

Multidrug-resistant Gram-negative Bacterial Bloodstream Infections in Children's Hospitals in Japan, 2010-2017

BACKGROUND

The risk factors of multidrug-resistant (MDR) Gram-negative bacilli (GNB) bloodstream infection (BSI) are not yet known in children. Our aim was to evaluate risk factors and outcomes associated with MDR GNB BSI in children.

METHODS

Patients with GNB BSI were enrolled between April 2010 and March 2017 at 8 children's hospitals in Japan. Clinical and microbiologic data were collected retrospectively. The risk factors and outcomes of MDR and non-MDR GNB BSI were compared.

RESULTS

In total, 629 GNB BSI episodes met the case definition. The median age and proportion of males were 2 years (interquartile range, 0.3-8.7) and 50.7%, respectively. An underlying disease was found in 94% of patients. The proportion of BSI cases that developed >48 hours after admission was 76.2%. MDR comprised 24.5% of BSI cases. The MDR rate did not change over time (P = 0.540). The effective coverage rate of the initial empiric therapy for the MDR and non-MDR BSI cases was 60.4% and 83.4%, respectively (P < 0.001). The all-cause mortality rate at 28 days for all BSI, MDR-BSI and non-MDR BSI cases was 10.7%, 13.6% and 9.7%, respectively (P = 0.167). MDR BSI was independently associated with cancer chemotherapy within 30 days (odds ratio [OR] 43.90), older age (OR 1.05) and admission to the neonatal ward (OR 0.019).

CONCLUSIONS

One-fourth of GNB BSI cases were MDR. Cancer chemotherapy and older age were risk factors for MDR GNB BSI in children's hospitals. MDR did not increase the all-cause mortality rate.

Influence of primary care antibiotic prescribing on incidence rates of multidrug-resistant Gram-negative bacteria in hospitalised patients

PURPOSE

Use of antibiotics can give rise to the selection of resistant bacteria. It remains unclear whether antibiotic use in primary care can influence bacterial resistance incidence in patients when hospitalised. The aim of this study is to explore the impact of prior community antibiotic usage on hospital-detected multidrug-resistant Gram-negative (MRGN) incidence rate.

METHODS

This pharmacoepidemiological study was case-control in design, and was carried out in the Antrim Area Hospital (N. Ireland) in two phases. In phase 1, the controls were matched according to: age, gender, admission ward, date of admission, and age-adjusted Charlson co-morbidity index score. During the second phase, controls were selected randomly from the total population of admissions to the hospital over the 2-year study period.

RESULTS

In phase 1, multivariate analysis revealed that prior exposure to the second- and third-generation cephalosporins (p = 0.004) and fluoroquinolones (p = 0.023) in primary care was associated with an increased likelihood of MRGN detection in inpatients. In phase 2, an independent relationship between an increased risk of identification of MRGN, while hospitalised was associated with: prolonged hospitalisation (p < 0.001), being elderly (p < 0.001), being female (p = 0.007), and having genitourinary disease (p < 0.001).

CONCLUSION

This study provides clear evidence which supports the need to optimise antibiotic use in primary care to help reduce MRGN incidence in hospitalised patients.

Clinical Prediction Score for Community-Onset Bloodstream Infections Caused by Extended-Spectrum Beta-Lactamase-Producing Escherichia coli and Klebsiella Species

BACKGROUND

This study aimed to identify the predictors and build a prediction score for community-onset bloodstream infections (CO-BSIs) caused by extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella species.

METHODS

All CO-BSIs caused by E. coli and Klebsiella species from 2012 to 2015 were grouped into derivation (BSIs from 2012 to 2014) and validation (BSIs in 2015) cohorts. A prediction score was built using the coefficients of the multivariate logistic regression model from the derivation cohort.

RESULTS

The study included 886 CO-BSIs (594 and 292 in the derivation and validation cohorts, respectively). The independent predictors of CO-BSIs caused by ESBL-producing E. coli and Klebsiella species included: 1) identification of ESBL-producing microorganisms from any clinical culture within one year of admission, 2) beta-lactam or fluoroquinolone treatment within 30 days (with 2 or more courses within 90 days; with 1 course within 90 days), 3) hospitalization within one year, 4) the presence of an indwelling urinary catheter at the time of admission. The area under the curve (AUC) of the clinical prediction score was 0.72 (95% confidence interval [CI], 0.68-0.77). In the validation cohort, the AUC was 0.70 (95% CI, 0.63-0.77).

CONCLUSIONS

The results of this study suggest a simple and easy-to-use scoring system to predict CO-BSIs caused by ESBL-producing E. coli and Klebsiella species.

Relating knowledge, attitude and practice of antibiotic use to extended-spectrum beta-lactamase-producing Enterobacteriaceae carriage: results of a cross-sectional community survey

OBJECTIVES

To study the correlation between knowledge, attitude and practices (KAP) of antibiotic consumption with epidemiology and molecular characteristics of extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-PE) carriage, in order to identify modifiable factors and public health interventions to reduce prevalence of multidrug-resistant organism colonisation in the community.

DESIGN

Cross-sectional questionnaire of KAP towards antibiotic use and collection of stool samples or rectal swabs. ESBL-PE isolates obtained underwent whole genome sequencing to identify resistance genes.

SETTING

A densely populated community in Singapore.

PARTICIPANTS

There were 693 healthy community-dwelling questionnaire respondents. Out of which, 305 provided stool samples or rectal swabs.

RESULTS

The overall knowledge of antibiotic use was poor (mean score 4.6/10, IQR 3.0-6.0). 80 participants (80/305, 26.2%) carried at least one ESBL-PE isolate. The most common ESBL-PE was Escherichia coli sequence type 131 carrying CTX-M type beta-lactamases (11/71, 15.5%). Living overseas for >1 year (OR 3.3, 95% CI 1.6 to 6.9) but not short-term travel, recent hospitalisation or antibiotic intake was associated with ESBL-PE carriage. Interestingly, higher knowledge scores (OR 2.0, 95% CI 1.03 to 3.9) and having no leftover antibiotics (OR 2.4, 95% CI 1.2 to 4.9) were independent factors associated with ESBL-PE carriage in the multivariate logistic regression model.

CONCLUSIONS

While the role of trans-border transmission of antimicrobial resistance is well known, we may have to examine the current recommendation that all antibiotics courses have to be completed. Clinical trials to determine the optimum duration of treatment for common infections are critically important.

A methodological comparison of risk scores versus decision trees for predicting drug-resistant infections: A case study using extended-spectrum beta-lactamase (ESBL) bacteremia

BACKGROUND

Timely identification of multidrug-resistant gram-negative infections remains an epidemiological challenge. Statistical models for predicting drug resistance can offer utility where rapid diagnostics are unavailable or resource-impractical. Logistic regression-derived risk scores are common in the healthcare epidemiology literature. Machine learning-derived decision trees are an alternative approach for developing decision support tools. Our group previously reported on a decision tree for predicting ESBL bloodstream infections. Our objective in the current study was to develop a risk score from the same ESBL dataset to compare these 2 methods and to offer general guiding principles for using each approach.

METHODS

Using a dataset of 1,288 patients with Escherichia coli or Klebsiella spp bacteremia, we generated a risk score to predict the likelihood that a bacteremic patient was infected with an ESBL-producer. We evaluated discrimination (original and cross-validated models) using receiver operating characteristic curves and C statistics. We compared risk score and decision tree performance, and we reviewed their practical and methodological attributes.

RESULTS

In total, 194 patients (15%) were infected with ESBL-producing bacteremia. The clinical risk score included 14 variables, compared to the 5 decision-tree variables. The positive and negative predictive values of the risk score and decision tree were similar (&gt;90%), but the C statistic of the risk score (0.87) was 10% higher.

CONCLUSIONS

A decision tree and risk score performed similarly for predicting ESBL infection. The decision tree was more user-friendly, with fewer variables for the end user, whereas the risk score offered higher discrimination and greater flexibility for adjusting sensitivity and specificity.

Prediction of bloodstream infection caused by extended-spectrum β-lactamase-producing Enterobacterales in patients with suspected community-onset sepsis

OBJECTIVES

In severe infections, time to appropriate therapy is decisive for survival. Patients with bloodstream infection caused by extended-spectrum β-lactamase-producing Enterobacterales (EPE-BSI) often receive inadequate empirical treatment. This study aimed to identify risk factors, to evaluate a previously suggested risk score and to suggest a new score for facilitating empirical treatment choice.

METHODS

Predictors for EPE-BSI were assessed through a retrospective case-control design. The diagnostic performance of the two scores was evaluated. Included patients had blood cultures sampled at four EDs in Stockholm (2012-2015), were admitted, and received antibiotics with activity against Gram-negative bacilli.

RESULTS

A total of 277 EPE-BSI cases and 400 controls were included. The strongest predictor of EPE-BSI was prior EPE-positive culture (cases 33% vs. controls 3%; multivariate (MV) OR = 19.1). Recent EPE-positivity within ≤3 months had a univariate OR of 32.8. Other major predictors were recent prostate biopsy (14% vs. 1%; MV OR = 22.2) and healthcare abroad (6% vs. 2%; MV OR = 3.9). Several previously suggested risk factors were not associated with EPE-BSI. The previously developed Utrecht score had a sensitivity of 54% and a specificity of 77%. The Stockholm score suggested herein (prior EPE-positive culture/prostate biopsy/healthcare abroad) showed comparable sensitivity (50%) but better specificity (96%). Prediction in patients lacking major predictors was difficult and caused high false-positive rates, which would cause unnecessary overtreatment.

CONCLUSIONS

Prior EPE-positive culture, especially recently sampled, prostate biopsy and healthcare abroad were the strongest risk factors for community-onset EPE-BSI in Stockholm. Local data are needed when evaluating risk-scoring models before implementation.

Utility of Combination Antimicrobial Therapy in Adults with Bloodstream Infections due to Enterobacteriaceae and Non-Fermenting Gram-Negative Bacilli Based on In Vitro Analysis at Two Community Hospitals

This study examined the utility of combination therapy for bloodstream isolates of Enterobacteriaceae and non-fermenting Gram-negative bacilli (NFGN) from adults at two community hospitals from January 2010 through to June 2015. Changes to in vitro antimicrobial susceptibilities by adding ciprofloxacin or gentamicin to third-generation cephalosporins (3GC) were examined overall and in patients with risk factors for 3GC resistance. Overall ceftriaxone susceptibility among Enterobacteriaceae was 996/1063 (94%) and 247/295 (84%) in patients with 3GC resistance risk factors. Susceptibilities increased marginally by adding ciprofloxacin or gentamicin (mean difference 2.4% (95% CI 1.5, 3.4) and 3.0% (95% CI 2.0, 4.0), respectively, overall and 5.4% (95% CI 2.8, 8.0) and 7.1% (95% CI 4.2, 10.1), respectively, in patients with risk factors). Eighty-three of 105 (79%) NFGN were susceptible to ceftazidime overall and 20/29 (69%) in patients with prior beta-lactam use. Overall mean increase in susceptibilities was 15.2% (95% CI: 8.3, 22.2) and 17.1% (95% CI: 9.8, 24.5) for ciprofloxacin and gentamicin combinations, respectively; and 27.6% (95% CI: 10.3, 44.9) for either one with recent beta-lactam use. In this setting, empirical combination therapy had limited utility for Enterobacteriaceae bloodstream isolates but provided significant additional antimicrobial coverage to ceftazidime for NFGN, particularly in patients with prior beta-lactam use.

Derivation of a quick Pitt bacteremia score to predict mortality in patients with Gram-negative bloodstream infection

PURPOSE

This retrospective cohort study derived a "quick" version of the Pitt bacteremia score (qPitt) using binary variables in patients with Gram-negative bloodstream infections (BSI). The qPitt discrimination was then compared to quick sepsis-related organ failure assessment (qSOFA) and systemic inflammatory response syndrome (SIRS).

METHODS

Hospitalized adults with Gram-negative BSI at Palmetto Health hospitals in Columbia, SC, USA from 2010 to 2013 were identified. Multivariate Cox proportional hazards regression was used to determine variables associated with 14-day mortality.

RESULTS

Among 832 patients with Gram-negative BSI, median age was 65 years and 449 (54%) were women. After adjustments for age and Charleston comorbidity score, all five components of qPitt were independently associated with mortality: temperature < 36 °C [hazard ratio (HR) 3.02, 95% confidence interval (CI) 1.95-4.62], systolic blood pressure < 90 mmHg or vasopressor use (HR 2.40, 95% CI 1.37-4.13), respiratory rate ≥ 25/min or mechanical ventilation (HR 3.01, 95% CI 1.81-5.14), cardiac arrest (HR 5.35, 95% CI 2.81-9.43), and altered mental status (HR 3.99, 95% CI 2.44-6.80). The qPitt had higher discrimination to predict mortality [area under receiver operating characteristic curve (AUROC) 0.85] than both qSOFA (AUROC 0.77, p < 0.001) and SIRS (AUROC 0.63, p < 0.001). There was a significant difference in mortality between appropriate and inappropriate empirical antimicrobial therapy in patients with qPitt ≥ 2 (24% vs. 49%, p < 0.001), but not in those with qPitt < 2 (3% vs. 5%, p = 0.36).

CONCLUSIONS

The qPitt had good discrimination in predicting mortality following Gram-negative BSI and identifying opportunities for improved survival with appropriate empirical antimicrobial therapy.

Using local clinical and microbiological data to develop an institution specific carbapenem-sparing strategy in sepsis: a nested case-control study

Background

From a stewardship perspective it is recommended that antibiotic guidelines are adjusted to the local setting, accounting for the local epidemiology of pathogens. In many settings the prevalence of Gram-negative pathogens with resistance to empiric sepsis therapy is increasing. How and when to escalate standard sepsis therapy to a reserve antimicrobial agent, is a recurrent dilemma. The study objective was to develop decision strategies for empiric sepsis therapy based on local microbiological and clinical data, and estimate the number needed to treat with a carbapenem to avoid mismatch of empiric therapy in one patient (NNTC).

Methods

We performed a nested case control study in patients (> 18 years) with Gram-negative bacteremia in 2013-2016. Cases were defined as patients with Gram-negative bacteremia with in vitro resistance to the combination 2nd generation cephalosporin AND aminoglycoside (C-2GC + AG). Control patients had Gram-negative bacteremia with in vitro susceptibility to cefuroxime AND/OR gentamicin, 1:2 ratio. Univariate and multivariable analysis was performed for demographic and clinical predictors of resistance. The adequacy rates of empiric therapy and the NNTC were estimated for different strategies.

Results

The cohort consisted of 486 episodes of Gram-negative bacteremia in 450 patients. Median age was 66 years (IQR 56-74). In vitro resistance to C-2GC + AG was present in 44 patients (8.8%). Independent predictors for resistance to empiric sepsis therapy were hematologic malignancy (adjusted OR 4.09, 95%CI 1.43-11.62, p < 0.01), previously cultured drug resistant pathogen (adjusted OR 3.72. 95%CI 1.72-8.03, p < 0.01) and antibiotic therapy during the preceding 2 months (adjusted OR 12.5 4.08-38.48, p < 0.01). With risk-based strategies, an adequacy rate of empiric therapy of 95.2-99.3% could be achieved. Compared to treating all patients with a carbapenem, the NNTC could be reduced by 82.8% (95%CI 78.5-87.5%) using the targeted approaches.

Conclusions

A risk-based approach in empiric sepsis therapy has the potential to better target the use of reserve antimicrobial agents aimed at multi-resistant Gram-negative pathogens. A structured evaluation of the expected antimicrobial consumption and antibiotic adequacy rates is essential to be able to weigh the costs and benefits of potential antibiotic strategies and select the most appropriate approach.

A Decision Tree Using Patient Characteristics to Predict Resistance to Commonly Used Broad-Spectrum Antibiotics in Children With Gram-Negative Bloodstream Infections

BACKGROUND

As rates of multidrug-resistant gram-negative infections rise, it is critical to recognize children at high risk of bloodstream infections with organisms resistant to commonly used empiric broad-spectrum antibiotics. The objective of the current study was to develop a user-friendly clinical decision aid to predict the risk of resistance to commonly prescribed broad-spectrum empiric antibiotics for children with gram-negative bloodstream infections.

METHODS

This was a longitudinal retrospective cohort study of children with gram-negative bacteria cared for at a tertiary care pediatric hospital from June 2009 to June 2015. The primary outcome was a bloodstream infection due to bacteria resistant to broad-spectrum antibiotics (ie, cefepime, piperacillin-tazobactam, meropenem, or imipenem-cilastatin). Recursive partitioning was used to develop the decision tree.

RESULTS

Of 689 episodes of gram-negative bloodstream infections included, 31% were resistant to broad-spectrum antibiotics. The decision tree stratified patients into high- or low-risk groups based on prior carbapenem treatment, a previous culture with a broad-spectrum antibiotic resistant gram-negative organism in the preceding 6 months, intestinal transplantation, age ≥3 years, and ≥7 prior episodes of gram-negative bloodstream infections. The sensitivity for classifying high-risk patients was 46%, and the specificity was 91%.

CONCLUSION

A decision tree offers a novel approach to individualize patients' risk of gram-negative bloodstream infections resistant to broad-spectrum antibiotics, distinguishing children who may warrant even broader antibiotic therapy (eg, combination therapy, newer β-lactam agents) from those for whom standard empiric antibiotic therapy is appropriate. The constructed tree needs to be validated more widely before incorporation into clinical practice.