Antimicrobial therapy is indispensable in neonatal intensive care. Early bacterial infection may present with nonspecific manifestations, and delayed treatment of genuine neonatal sepsis can have devastating consequences. For this reason, clinicians frequently initiate empirical antibiotics when infection cannot initially be excluded. However, the same diagnostic uncertainty contributes to antibiotic overuse. The problem is especially important among premature infants, in whom antibiotics are often initiated immediately after birth because of maternal risk factors or nonspecific neonatal instability, even when cultures ultimately remain negative. Prolonged antibiotic exposure is clinically important. In premature infants with negative cultures, prolonged empirical therapy has been associated in observational literature with adverse outcomes including necrotizing enterocolitis, invasive fungal infection, bronchopulmonary dysplasia, mortality, microbiome disruption, and antimicrobial-resistance selection. Antimicrobial stewardship has therefore become an essential component of neonatal quality and safety. Yet stewardship encompasses multiple distinct strategies including guidelines, education, antibiotic restriction, justification forms, automatic stop orders, audit rounds, early-onset sepsis decision support, DOT measurement, and antibiogram-based prescribing. The clinically relevant question is therefore which stewardship strategies actually change prescribing behavior and reduce unnecessary neonatal antibiotic exposure. This review addresses that question using a strategy-based rather than disease-based framework. Aim and Objectives Aim: To systematically evaluate antimicrobial stewardship strategies designed to reduce antibiotic overuse in neonatal intensive care units. 1. Evaluate interventions that reduce unnecessary antibiotic initiation. 2. Assess automatic stop orders and duration-limiting strategies. 3. Evaluate restriction and preauthorization approaches. 4. Assess prospective audit and feedback. 5. Examine the effect of unit-specific guidelines and prescribing protocols. 6. Evaluate diagnostic and biomarker-supported stewardship. 7. Compare direct prescribing interventions with education-only approaches. 8. Identify measurable indicators for implementing an effective NICU stewardship program.

Review Design This systematic review was structured according to PRISMA 2020 principles. The principal strategy-analysis dataset focused on implemented antimicrobial stewardship interventions in NICUs, with particular emphasis on premature infants and measurable antibiotic-utilization outcomes. Review Question Which antimicrobial stewardship strategies are most effective in reducing unnecessary antibiotic exposure in NICUs without compromising appropriate treatment of neonatal infection? PICO Framework Component Definition Population Neonates cared for in NICUs, with particular emphasis on premature infants Intervention Structured antimicrobial stewardship strategy Comparator Pre-intervention practice, usual care, or conventional prescribing Primary outcomes DOT, antibiotic exposure, prolonged therapy, initiation rate Secondary outcomes Broad-spectrum use, de-escalation, resistance, treatment restart, mortality Information Sources The principal systematic search included PubMed/MEDLINE, McMaster PLUS, the Cochrane Database of Systematic Reviews, Cochrane CENTRAL, UpToDate, and National Institute for Health and Care Excellence resources. Reference lists were additionally examined for potentially relevant intervention studies. Eligibility Criteria • Evaluated an implemented antimicrobial stewardship intervention. • Included neonates cared for in NICUs. • Included premature infants of <=34 weeks gestation or equivalent very-low-birth-weight populations in the principal evidence subset. • Compared antibiotic use before and after stewardship or against a control group. • Provided measurable antimicrobial-utilization outcomes. Studies were excluded if they merely described antibiotic consumption, contained recommendations without an implemented intervention, focused exclusively on an individual organism without general stewardship relevance, evaluated highly specific prophylaxis without broader applicability, or were commentaries/guidelines without intervention outcomes. PRISMA 2020 Study Selection The systematic search identified 1,212 records. No duplicate records were reported in the principal strategy-analysis dataset. After title and abstract screening, 1,183 records were excluded. Twenty-nine full-text articles were assessed for eligibility, of which 17 were excluded. Twelve studies were included in the final systematic review: 11 observational intervention studies and one randomized controlled trial. Heterogeneity in interventions and outcome definitions precluded a pooled meta-analysis. Selection stage n Records identified 1212 Duplicates reported 0 Records screened 1212 Records excluded after title/abstract 1183 Full texts assessed 29 Full texts excluded 17 Studies included 12 Observational studies 11 Randomized controlled trials 1 Data Extraction Extracted variables included author, publication year, NICU population, gestational-age criteria, stewardship strategy, baseline antibiotic use, post-intervention antibiotic use, DOT, prolonged treatment, broad-spectrum antimicrobial consumption, de-escalation, and safety outcomes. Risk-of-Bias Assessment Observational studies were evaluated using the Newcastle-Ottawa Scale, while the randomized study was assessed using a trial-quality framework. The 11 observational studies were generally judged to have good methodological quality, whereas the single randomized trial had greater risk-of-bias concerns in the source evidence review. Study type Number Overall appraisal Observational intervention studies 11 Generally high quality Randomized trial 1 Higher risk of bias Total 12 -

Classification of Stewardship Strategies The included interventions were classified into three major groups: strategies reducing antibiotic initiation, strategies reducing treatment duration, and organizational or multicomponent stewardship. Five studies included interventions spanning more than one category. Strategy Primary mechanism Expected impact Risk-based initiation criteria Prevent unnecessary start Lower exposure rate Automatic 36-48 h stop Prevent unintended continuation Lower DOT Culture-negative duration limit Prevent prolonged empirical courses Lower LOT Prospective audit and feedback Correct active prescribing Lower inappropriate therapy Restricted-agent justification Reduce broad-spectrum use Improved spectrum Antibiotic guideline Standardize treatment Reduce variation Antibiotic time-out Mandatory reassessment Earlier stopping Diagnostic stewardship Improve certainty Reduce unnecessary therapy De-escalation requirement Narrow therapy after cultures Reduced spectrum pressure Measurement + feedback Modify prescriber behavior Sustained improvement 1. Strategies to Reduce Antibiotic Initiation Three of the 12 studies specifically targeted antibiotic initiation. These approaches relied on combinations of maternal infection risk, clinical condition, laboratory findings, microbiological evidence, and structured neonatal sepsis algorithms. Patient-specific initiation criteria were more actionable than broad educational recommendations. 2. Automatic Stop Orders Eight of the 12 studies included strategies intended to reduce antibiotic duration. Automatic stopping after 36-48 hours was among the most consistently successful approaches because it changed the default from continuation unless stopped to stopping unless continuation was actively justified. 3. Effect of Automatic 48-Hour Stopping Astorga et al. implemented an automatic 48-hour stop order for empirical antibiotics. The intervention was associated with approximately a 35% reduction in total antibiotic doses per patient and a 25% reduction in doses per patient-day. 4. Reduction in Days of Therapy Eight studies reported antibiotic utilization using DOT or comparable patient-day measures. Most demonstrated meaningful decreases in total antibiotic consumption after implementation of stewardship strategies. 5. Prolonged Antibiotic Therapy Treatment duration beyond 48 hours was highly modifiable. Kitano et al. reported prolonged therapy decreasing from 65.0% to 32.5%, Tolia et al. reported exposure beyond 48 hours decreasing from 63.4% to 41.3%, and Lu et al. reported discontinuation within 48 hours increasing from 32% to 95%. 6. Culture-Negative Treatment Limits Some stewardship programs specifically limited treatment duration for culture-negative sepsis, pneumonia, or nonspecific deterioration. The central principle is that culture-negative infection should not automatically become a prolonged antibiotic diagnosis; each additional treatment day should require clinical justification. 7. Restricted Antibiotic Policies Restriction targets high-impact agents such as carbapenems, third-generation cephalosporins, vancomycin, and broad-spectrum beta-lactam/beta-lactamase inhibitor combinations. A South Indian intervention reduced restricted antimicrobial use from 49.35% to 40.54%, increased de-escalation from 29.47% to 60.0%, and reduced mean restricted-treatment duration from 13.78 to 9.9 days. 8. De-escalation as a Stewardship Strategy A sophisticated stewardship metric is whether broad empirical therapy is narrowed once microbiological information becomes available. Programs should distinguish appropriate empirical breadth from unnecessary continued breadth. 9. Prospective Audit and Feedback Prospective audit and feedback uses active review of antimicrobial prescriptions by a stewardship team. Recommendations may include discontinuation, narrowing, changing agents, shortening duration, obtaining missing microbiology, or reconsidering diagnosis. The approach is individualized but resource-intensive. 10. Guidelines Alone Are Not Enough Interventions containing only general organizational messages were often less successful than strategies linked to patient-level prescribing decisions. Knowledge-based stewardship is not the same as behavior-changing stewardship. 11. Diagnostic Stewardship Important components include adequate blood-culture volume, cultures before antibiotics, rapid laboratory processing, appropriate interpretation of contaminants, and timely susceptibility reporting. Diagnostic stewardship enables confident discontinuation and de-escalation. 12. Biomarker-Guided Stewardship C-reactive protein and procalcitonin may support earlier discontinuation when interpreted together with clinical improvement, negative cultures, and absence of focal infection. Their most useful role is supporting a stop decision rather than prolonging therapy indefinitely. 13. Measurement and Feedback The preferred neonatal antimicrobial metric is generally DOT per 1,000 patient-days because neonatal doses vary substantially by birth weight, gestational age, postnatal age, and renal function. Measurement and feedback are essential for sustaining improvement. Selected Changes in Antibiotic Consumption Study Before After Main strategy Cantey et al. 343.2 DOT 252.2 DOT Stop rule + culture-negative duration limit Bhat et al. 154.8 DOT 138.4 DOT Initiation criteria + stop strategy Kitano et al. 175.1 DOT 41.6 DOT Multivariable initiation/stop criteria Lu et al. 543 DOT 380 DOT Restriction + stop + education McCarthy et al. 572 DOT 417 DOT Prescription review + 36-h stopping Tolia et al. 99.5 DOT 71.7 DOT Automatic stop + stewardship measures DOT values are shown according to the original study metrics and denominators. Strategy Effectiveness Matrix Strategy Initiation Duration Spectrum Resource requirement Risk-based start criteria +++ + + Moderate EOS decision support +++ + + Low-moderate Automatic 36-48 h stop + +++ + Low Mandatory antibiotic time-out + +++ ++ Low Culture-negative duration limit - +++ + Low Restricted-agent approval + + +++ Moderate Prospective audit-feedback ++ ++ +++ High Guideline alone + + ++ Low Education alone + + + Low Guideline + stop + feedback +++ +++ +++ Moderate-high +++ = strong expected impact; ++ = moderate; + = limited/supportive effect.

This systematic review identifies an important distinction between interventions that encourage better prescribing and interventions that force a prescribing decision. The most consistent reductions in antibiotic exposure were achieved when stewardship was incorporated into individual clinical workflows. Automatic stop orders are a strong example. They do not require clinicians to remember stewardship principles; instead, the prescription expires unless continuation is actively justified. This changes the default behavior and can substantially reduce prolonged empirical treatment. Risk-based initiation criteria act earlier in the pathway by preventing unnecessary courses before exposure begins. Avoiding a course entirely produces a greater reduction in antibiotic pressure than merely shortening the same course after it has started. Multicomponent interventions appear superior to isolated policies. Guideline plus automatic stopping plus audit-feedback addresses initiation, continuation, spectrum, and accountability simultaneously. Broad-spectrum use must be monitored separately from total antibiotic consumption. A program may meaningfully improve first-line prescribing, reduce cephalosporin or carbapenem pressure, and increase de-escalation even when total DOT changes modestly. The overall synthesis suggests a predictable antibiotic-overuse cascade: risk factor -> empirical initiation -> no mandatory reassessment -> negative culture with persistent uncertainty -> continued therapy -> unchanged broad spectrum -> prolonged exposure. Effective stewardship interrupts this cascade at multiple points. Intervention points include risk assessment before initiation, indication documentation at prescription, antibiotic review at 24-36 hours, automatic stop at 36-48 hours, culture-driven de-escalation, and prescribing feedback after completion. Strengths • Categorizes interventions by behavioral mechanism. • Uses a defined PRISMA study-selection dataset for the strategy-focused evidence set. • Compares initiation- versus duration-focused interventions. • Distinguishes broad-spectrum stewardship from total antibiotic reduction. • Considers automatic stop orders separately. • Evaluates organizational strategies against patient-level interventions. • Proposes an implementation hierarchy and monitoring dashboard. Limitations • Only one study in the principal 12-study strategy set was randomized. • Intervention designs were heterogeneous. • Many studies included mixed NICU populations even when premature infants were the primary population of interest. • Baseline antibiotic use varied substantially between NICUs. • DOT definitions and denominators were not uniform. • Long-term antimicrobial-resistance outcomes were infrequently reported. • The principal evidence set was weighted toward premature-infant stewardship and this should be acknowledged if retaining a general NICU title. Future Research 1. Automatic stop order versus clinician reminder. 2. 36-hour versus 48-hour discontinuation. 3. Electronic indication requirements. 4. Biomarker-supported stop rules. 5. Stewardship effects in extremely preterm infants. 6. Antibiotic restart after automatic stopping. 7. Broad-spectrum antibiotic pressure. 8. Long-term resistance ecology. 9. Microbiome recovery. 10. Cost-effectiveness. 11. Clinician acceptance. 12. Automated electronic stewardship alerts. 13. Machine-learning decision support. 14. Benchmarking between NICUs. 15. Sustainability beyond the initial quality-improvement period.

Antibiotic overuse in NICUs can be reduced, but the effectiveness of antimicrobial stewardship depends strongly on how the intervention changes prescribing behavior. The most successful strategies are structured criteria limiting unnecessary initiation, automatic 36- to 48-hour stop orders, predefined limits for culture-negative treatment, mandatory antibiotic reassessment, broad-spectrum antibiotic restriction, active de-escalation, prospective audit and feedback, and multicomponent NICU-specific stewardship programs. Interventions directly linked to individual prescriptions are more consistently effective than general educational or organizational messages alone. The central stewardship principle is: do not rely on clinicians merely to remember to use fewer antibiotics. Design the NICU prescribing system so that every initiation, continuation, and broad-spectrum choice requires a deliberate and reviewable clinical decision.

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