Healthcare Epidemiology: Does Antibiotic Selection Impact Patient Outcome?

Targeted Metagenomic Sequencing-Based Approach Applied to 2,146 Tissue and Body Fluid Samples in Routine Clinical Practice

BACKGROUND

The yield of next generation sequencing (NGS) added to a Sanger sequencing-based 16S ribosomal RNA (rRNA) gene PCR assay was evaluated in clinical practice for diagnosis of bacterial infection.

METHODS

PCR targeting the V1 to V3 regions of the 16S rRNA gene was performed, with amplified DNA submitted to Sanger sequencing and/or NGS (Illumina MiSeq), or reported as negative, depending on cycle threshold (Ct) value. 2,146 normally sterile tissues or body fluids were tested between August 2020 and March 2021. Clinical sensitivity was assessed in 579 subjects from whom clinical data was available.

RESULTS

Compared to Sanger sequencing alone (400 positive tests), positivity increased by 87% by adding NGS (347 added positive tests). Clinical sensitivity of the assay incorporating NGS was 53%, higher than culture (42%, p<0.001), with an impact on clinical decision-making in 14% of infected cases. Clinical sensitivity in the subgroup receiving antibiotics at sampling was 41% for culture and 63% for the sequencing assay (p<0.001).

CONCLUSION

Adding NGS to Sanger sequencing of the PCR-amplified 16S rRNA gene substantially improved test positivity. In the patient population studied, the assay was more sensitive than culture, and especially so in patients who had received antibiotic therapy.

Diagnostic Value of 16S Ribosomal RNA Gene Polymerase Chain Reaction/Sanger Sequencing in Clinical Practice

BACKGROUND

Accurate microbiologic diagnosis is important for appropriate management of infectious diseases. Sequencing-based molecular diagnostics are increasingly used for precision diagnosis of infections. However, their clinical utility is unclear.

METHODS

We conducted a retrospective analysis of specimens that underwent 16S ribosomal RNA (rRNA) gene polymerase chain reaction (PCR) followed by Sanger sequencing at our institution from April 2017 through March 2019.

RESULTS

A total of 566 specimens obtained from 460 patients were studied. Patients were considered clinically infected or noninfected based on final diagnosis and management. In 17% of patients, 16S rRNA PCR/sequencing was positive and in 5% of patients, this test led to an impact on clinical care. In comparison, bacterial cultures were positive in 21% of patients. Specimens with a positive Gram stain had 12 times greater odds of having a positive molecular result than those with a negative Gram stain (95% confidence interval for odds ratio, 5.2-31.4). Overall, PCR positivity was higher in cardiovascular specimens (37%) obtained from clinically infected patients, with bacterial cultures being more likely to be positive for musculoskeletal specimens (P < .001). 16S rRNA PCR/sequencing identified a probable pathogen in 10% culture-negative specimens.

CONCLUSION

16S rRNA PCR/sequencing can play a role in the diagnostic evaluation of patients with culture-negative infections, especially those with cardiovascular infections.

Patterns, price and predictors of successful empiric antibiotic therapy in a real-world setting

WHAT IS KNOWN AND OBJECTIVE

Prompt and appropriate empiric antibiotic therapy (EAT) remains the cornerstone of successful outcomes, while the majority of blood cultures do not identify pathogen. We aimed to report patterns of EAT and its impact on outcomes and associated medical costs, while exploring predictors of its success in a real-world setting.

METHODS

We retrospectively utilized the prospective registry of the medical unit of a tertiary university hospital, including patients admitted with diagnosis of infection between 1st May 2016 and 1st May 2018. Costs of hospitalization and unit of antibiotic regimen were retrieved from a database regarding Greek hospitals containing hospitalization-cost data for each ICD-10 code and the national formulary, respectively.

RESULTS

A total of 489 patients were included in this study. Mean age was 61.3 years, 53% were males, while intra-abdominal infections predominated (55%). The most commonly administered EAT included quinolones (48%), followed by piperacillin/tazobactam (18%), or other regimens alone or in combination. EAT was successful in 67% and failed in 33% of cases. Fourteen patients died of the infection before EAT was switched, while among 55 patients that EAT had to be modified, mortality was 22%. Presence of urinary tract infection and use of quinolones, least predicted for failure of EAT [OR:0.15 (0.07-0.35), p < 0.0001, OR:0.53 (0.32-0.90), p = 0.019, respectively], in contrast to presence of sepsis [OR:3.11 (1.79-5.40), p < 0.0001]. Patients with failure had longer length of stay [7(5-11) versus 4 (3-6) days], higher antibiotic [201.9 (97.8-471.8) vs 104.6 (60.2-187.7) euros] and hospitalization costs [1409.3 (945.4-2311.6) vs 759.4 (516.5-1036.5) euros] (p < 0.0001).

DISCUSSION

We observed significantly increased antibiotic-related, healthcare-related costs and length of stay in patients with failure of EAT. Moreover, in our cohort, absence of sepsis, presence of urinary tract infection and use of quinolones better predicted for success of EAT.

WHAT IS NEW AND CONCLUSIONS

Appropriate selection of EAT is crucial to ensure better outcomes and minimize costs.

Stewardship program on carbapenem prescriptions in a tertiary hospital for adults and children in France: a cohort study

Antimicrobial stewardship programs aim at reducing the overuse of broad-spectrum antibiotics such as carbapenems, but their impact remains unclear. We compared the use of carbapenems between paediatric and adult subjects admitted to a French tertiary hospital and described the intervention of an antibiotic stewardship team (AST). As part of AST routine activity, all adult and paediatric patients receiving carbapenems are identified in real time using a computer-generated alert system and reviewed by the AST. Data associated with carbapenem prescriptions were extracted for 2 years (2014-2015) and were compared between paediatric and adult wards. Prescription appropriateness (i.e. no clinically suitable narrower spectrum alternative to carbapenem for de-escalation) and AST intervention were analysed. In total, 775 carbapenem prescriptions for 291 children and 262 adults were included. Most patients (95%) had a comordity and 52% had known recent carriage of extended-spectrum beta-lactamase producing Enterobacteriaceae (ESBLE). Most carbapenem prescriptions came from intensive care units (n = 269, 35%) and were initiated for urinary tract (n = 200, 27%), sepsis (n = 181, 25%), and lung (n = 153, 21%) infections. Carbapenems were initiated empirically in 537 (70%) cases, and an organism was isolated in 523 (67%) cases. Among the isolated organisms, 47% (n = 246) were ESBLE and 90% (n = 468) were susceptible to carbapenems, but an alternative existed in 61% (n = 320) of cases according to antibiotic susceptibility testing. Among prescriptions reviewed by the AST, 39% (n = 255) were considered non-appropriate and led to either antibiotic discontinuation (n = 47, 7%) or de-escalation (n = 208, 32%). Non-appropriate prescriptions were more frequent in paediatric wards (p = 0.01) and in microbiologically documented infections (p = 0.013), and less observed in immunocompromised patients (p = 0.009) or with a known ESBLE carriage (p < 0.001). Tailored stewardship programs are essential to better control carbapenem use and subsequent antimicrobial resistance.

Evaluation of a mass spectrometry and Vitek 2 combined protocol for rapid identification and susceptibility testing of Enterobacterales directly from positive blood cultures

OBJECTIVE

The aim was to evaluate a rapid method which would combine identification and susceptibility testing directly from positive blood cultures for Gram-negative bacilli of the Enterobacterales.

MATERIAL AND METHODS

Gram-negative rods from blood cultures were directly identified by MALDI-TOF. Samples with Enterobacterales were selected for direct antimicrobial susceptibility testing by Vitek 2. The results were compared to those obtained with our laboratory's standard method.

RESULTS

MALDI-TOF directly from blood cultures identified correctly 83% of the samples. Enterobacterales (n=68) were identified at gender and species level in 85% of blood cultures with a score >1.7. In general, MICs were obtained after 7h. MICs of amoxicillin-clavulanate, amikacin and ciprofloxacin showed in almost 50% of the cases after 5h.

CONCLUSIONS

A simple procedure with low cost and reduced working time makes it possible to integrate both identification and susceptibility testing directly from blood cultures. Thus, this protocol could offer advantages when it comes to selection and cost of treatment and patients' clinical outcomes.

Influence of severity of infection on the effect of appropriate antimicrobial therapy for Acinetobacter baumannii bacteremic pneumonia

Background

The impact of appropriate antimicrobial therapy for A. baumannii bacteremic pneumonia has not been well established due to the inclusion of the three phenotypically indistinguishable Acinetobacter species and confounding factors including underlying diseases and severity of infection. This retrospective study aimed to evaluate the impact of appropriate antimicrobial therapy on 14-day mortality in A. baumannii bacteremic pneumonia patients after adjusting for risk factors.

Methods

This study was conducted at five medical centers in Taiwan between July 2012 and June 2016. A. baumannii species identification was performed using reference molecular methods. Risk factors for 14-day mortality were analyzed via logistic regression. The interaction between the Acute Physiology and Chronic Health Evaluation (APACHE) II score and appropriate antimicrobial therapy was assessed using the logistic model.

Results

A total of 336 patients with monomicrobial A. baumannii bacteremic pneumonia were included in this study. The overall 14-day mortality rate was 47.3%. The crude mortality of appropriate antimicrobial therapy was 35.9% (57 of 151 patients). Appropriate antimicrobial therapy was associated with a lower mortality after multivariate adjustment (odds ratio [OR], 0.57; 95% confidence interval [CI], 0.34–0.97; p = 0.04), and the effect was influenced by APACHE II score (OR for interaction term, 0.0098; 95% CI, 0.0005–0.1885; p = 0.002). Further analysis demonstrated that appropriate antimicrobial therapy significantly reduced 14-day mortality among the patients with an APACHE II score > 35 (OR 0.0098; 95% CI 0.0005–0.1885).

Conclusion

Appropriate antimicrobial therapy decreases 14-day mortality of the most severely ill patients with A. baumannii bacteremic pneumonia.

Mortality after Delay of Adequate Empiric Antimicrobial Treatment of Bloodstream Infection

BACKGROUND

Timely empiric antimicrobial therapy is one of the cornerstones of the management of suspected bloodstream infection (BSI). However, studies about the effects of empiric therapy on mortality have reported inconsistent results. The objective of this study was to estimate the effect of delay of appropriate empiric therapy on early mortality in patients with BSI. Methods: Data for the propensity score matching (PSM) study were obtained from a cohort of patients with BSI. Inadequate empiric treatment was defined as in vitro resistance to the antimicrobial regimen administered <6 h after blood cultures were taken. The primary outcome measure was 14-day mortality. Thirty-day mortality and median length of stay (LOS) were secondary outcomes. PSM was applied to control for confounding. Results: Of a total of 893 included patients with BSI, 35.7% received inadequate initial empiric treatment. In the PSM cohort (n = 334), 14-day mortality was 9.6% for inadequate antibiotic treatment, compared to. 10.2% in adequate empiric treatment (p = 0.85). No prolonged median LOS was observed in patients who initially received inadequate therapy (10.5 vs. 10.7 days, p = 0.89). Conclusions: In this study, we found no clear effect of inadequate empirical treatment on mortality in a low-risk BSI population. The importance of early empiric therapy compared to other determinants, may be limited. This may not apply for specific subpopulations, e.g., patients with sepsis.

The impact of carbapenem-resistant Pseudomonas aeruginosa on clinical and economic outcomes in a Chinese tertiary care hospital: A propensity score-matched analysis

BACKGROUND

This study aimed to estimate the impact of carbapenem-resistant Pseudomonas aeruginosa (CRPA) on clinical and economic outcomes in a Chinese tertiary care hospital.

METHODS

Patients were assigned to a carbapenem-susceptible P aeruginosa group or to a CRPA group and matched using propensity score matching. In-hospital mortality, length of stay (LOS), LOS after culture, total hospital costs, daily hospital cost, and 30-day readmission were comparatively analyzed. Subgroup analysis was performed to determine the associations between the subgrouping factors and in-hospital mortality in patients with CRPA isolates.

RESULTS

Within the propensity-matched cohort, in-hospital mortality (12.6% vs 7.8%; P   =   .044), LOS (median 29.0 vs 25.5 days; P   =   .026), LOS after culture (median 18.5 vs 14.0 days; P   =   .029), total hospital costs (median $6,082.0 vs $4,954.2; P  =  .015), and daily hospital cost (median $236.1 vs $223.6; P  =  .045) were significantly higher in CRPA patients than in carbapenem-susceptible P aeruginosa patients. Subgroup analysis revealed a significant interaction between CRPA and age (P  =  .009).

CONCLUSION

Prevention and control of CRPA among hospitalized patients, especially among those over the age of 65 years, is a good measurement for the reduction of mortality and medical costs derived from CRPA infection or colonization.

Microbial Identification Using DNA Target Amplification and Sequencing: Clinical Utility and Impact on Patient Management

Broad-range polymerase chain reaction (PCR) is increasingly used in patients with culture-negative infections; however, few studies have assessed the diagnostic utility of this test in this context. We performed a retrospective cohort study of patients who had clinical specimens sent for broad-range PCR, aiming to evaluate performance and determine impact on patient management. Organisms were identified in 21/71 samples. High numbers of polymorphonuclear leukocytes on Gram stain (odds ratio [OR], 4.17; P = .04) and acute inflammation on histopathology (OR, 5.69; P = .02) were significantly associated with a positive result. Management was altered in 18 patients, 11 with positive and 7 with negative results. Overall, broad-range PCR assay had the highest impact in patients with microscopic evidence of inflammation. Physicians ordering this complex, difficult to interpret, and expensive test should carefully consider all available clinical information on an individualized basis to optimize its performance.

Developing a decision support system for patients with severe infection conditions in pre-hospital care

OBJECTIVE

To develop and validate a pre-hospital decision support system (DSS) for the emergency medical services (EMS), enabling the identification and steering of patients with critical infectious conditions (i.e., severe respiratory tract infections, severe central nervous system (CNS) infections, and sepsis) to a specialized emergency department (ED) for infectious diseases.

METHODS

The development process involved four consecutive steps. The first step was gathering data from the electronic patient care record system (ePCR) on patients transported by the EMS, in order to identify retrospectively appropriate patient categories for steering. The second step was to let a group of medical experts give advice and suggestions for further development of the DSS. The third and fourth steps were the evaluation and validation, respectively, of the whole pre-hospital DSS in a pilot study.

RESULTS

A pre-hospital decision support tool (DST) was developed for three medical conditions: severe respiratory infection, severe CNS infection, and sepsis. The pilot study included 72 patients, of whom 60% were triaged to a highly specialized emergency department (ED-Spec) with an attending infectious disease physician (ID physician). The results demonstrated that the pre-hospital emergency nurses (PENs) adhered to the DST in 66 of 72 patient cases (91.6%). For those patients steered to the ED-Spec, the assessment made by PENs and the ID physician at the ED was concordant in 94% of cases.

CONCLUSIONS

The development of a specific DSS aiming to identify patients with three different severe infectious diseases appears to give accurate decision support to PENs when steering patients to the optimal level of care.

Salvage Strategy for Long-Term Central Venous Catheter-Associated Staphylococcus aureus Infections in Children

Introduction: Current international guidelines strongly recommend catheter removal in case of S. aureus central line-associated bloodstream infection (CLASBI), but a catheter salvage strategy may be considered in children given age-related specificities. No data is available regarding the outcome of this strategy in children. This study aims to evaluate catheter salvage strategy in children with S. aureus CLABSI, and to determine treatment failure rates and associated risk factors. Methods: We retrospectively analyzed data for all children <18 years having S. aureus CLABSI on a long-term central venous catheter in a tertiary hospital from 2010 to 2014. We defined catheter salvage strategy as a central venous catheter left in place ≥3 days after initiation of empiric treatment for suspected bacteremia, and catheter salvage strategy failure as the persistence or relapse of bacteremia with a S. aureus strain harboring the same antibiotic susceptibility pattern, or the occurrence or the worsening of local or systemic infectious complication between 72 h and 28 days after the first positive blood culture. Results: During the study period, 49 cases of S. aureus CLABSI on long-term central venous catheters were observed in 41 children (including 59% with long-term parenteral nutrition) and 6 (15%) isolates were resistant to methicillin. A catheter salvage strategy was chosen in 37/49 (76%) cases and failed in 12/37 (32%) cases. Initial presence of bloodstream co-infection, serum concentration of vancomycin under the targeted value and inadequate empiric treatment were significantly associated with catheter salvage therapy failure. Conclusions: The catheter salvage strategy of S. aureus CLABSI on a long-term central venous catheter was frequent in the studied hospital and failed only in one third of cases.

Multidrug-resistant Pseudomonas aeruginosa lower respiratory tract infections in the intensive care unit: Prevalence and risk factors

Intensive care unit (ICU) admission is a risk for multidrug-resistant (MDR) Pseudomonas aeruginosa, but factors specific to critically ill pneumonia patients are not fully characterized. Objective was to determine risk factors associated with MDR P. aeruginosa pneumonia among ICU patients. This was a retrospective case-control study of P. aeruginosa pneumonia in the ICU; cystic fibrosis and colonizers were excluded. Risk factors included comorbid conditions and prior healthcare exposure (anti-pseudomonal antibiotics, hospitalizations, nursing home, P. aeruginosa colonization/infection, mechanical ventilation). Of 200 patients, 47 (23.5%) had MDR P. aeruginosa pneumonia. Independent predictors for MDR were ≥24h antibiotics in the preceding 90days (carbapenems, fluoroquinolones, and piperacillin-tazobactam) (odds ratio, 3.6 [95% CI, 1.6-8.1]) and nursing home residence (2.3 [1.1-4.9]). MDR P. aeruginosa remains prevalent among ICU patients with pneumonia. Given poor outcomes with delayed therapy, patients should be thoroughly assessed for prior anti-pseudomonal antibiotic exposure and nursing home residency.

Early Identification and Treatment of Pathogens in Sepsis: Molecular Diagnostics and Antibiotic Choice

Sepsis and septic shock are serious conditions associated with high morbidity and mortality. Rapid molecular methods for detection of microorganisms and antimicrobial resistance genes from positive blood cultures or whole blood have evolved over the past 10 years. Such diagnostic methods coupled with therapeutic interventional programs are desirable to improve the overall clinical outcome and mortality. This article discusses the usefulness of current molecular test methods for the diagnosis of sepsis and their potential to enhance the success of antimicrobial stewardship programs. Clinicians and laboratories alike must appreciate key factors influencing the appropriate use and potential impact of these methods.

Risk Factors and Clinical Outcomes for Patients With Acinetobacter baumannii Bacteremia

Acinetobacter (A.) baumannii, an opportunistic nosocomial pathogen that can cause significant morbidity and mortality, has emerged as a worldwide problem. This study aimed to analyze the clinical features and outcomes of patients with A. baumannii bacteremia and determine the factors influencing survival by using 14-day mortality as the primary endpoint. A 6-year retrospective study of 122 cases with monomicrobial A. baumannii bacteremia was conducted in Chinese People's Liberation Army (PLA) General Hospital from January 2008 to April 2014. Predictors of 14-day mortality were identified by logistic regression analysis. The overall 14-day mortality rate was 40.2% (49 of 122 patients). Multivariable analysis revealed that independent predictors of 14-day mortality included severity of illness defined by Pitt Bacteremia Score (PBS) (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.340-0.619; P < 0.001), neutropenia (OR, 18.02; 95% CI, 1.667-194.67; P = 0.017), and malignancy (OR, 4.63; 95% CI, 1.292-16.588; P = 0.019). The effect of malignancy was influenced by neutropenia (OR for interaction term, 1.60; 95% CI, 1.15-2.22; P = 0.005). A subgroup analysis revealed that 14-day mortality rate for patients with underlying hematological malignancies and solid tumors was 75% (12/16) and 40% (12/30), respectively. Survival analysis revealed that mortality in patients with hematological malignancies was higher than that in patients with solid tumors (P = 0.032). The outcomes of patients with A. baumannii bacteremia were related to PBS, neutropenia, and malignancy. Compared with solid tumors, patients with hematological malignancies had a higher mortality in the setting of A. baumannii bacteremia.

Treatment of Gram-negative pneumonia in the critical care setting: is the beta-lactam antibiotic backbone broken beyond repair?

Beta-lactam antibiotics form the backbone of treatment for Gram-negative pneumonia in mechanically ventilated patients in the intensive care unit. However, this beta-lactam antibiotic backbone is increasingly under pressure from emerging resistance across all geographical regions, and health-care professionals in many countries are rapidly running out of effective treatment options. Even in regions that currently have only low levels of resistance, the effects of globalization are likely to increase local pressures on the beta-lactam antibiotic backbone in the near future. Therefore, clinicians are increasingly faced with a difficult balancing act: the need to prescribe adequate and appropriate antibiotic therapy while reducing the emergence of resistance and the overuse of antibiotics. In this review, we explore the burden of Gram-negative pneumonia in the critical care setting and the pressure that antibiotic resistance places on current empiric therapy regimens (and the beta-lactam antibiotic backbone) in this patient population. New treatment approaches, such as systemic and inhaled antibiotic alternatives, are on the horizon and are likely to help tackle the rising levels of beta-lactam antibiotic resistance. In the meantime, it is imperative that the beta-lactam antibiotic backbone of currently available antibiotics be supported through stringent antibiotic stewardship programs.

Influence of carbapenem resistance on mortality of patients with Pseudomonas aeruginosa infection: a meta-analysis

Treatment of infectious diseases caused by the carbapenem-resistant Pseudomonas aeruginosa (CRPA) is becoming more challenging with each passing year. We conducted a meta-analysis to assess the impact of carbapenem resistance on mortality of patients with P. aeruginosa infection. We searched PUBMED, Web of science, EMBASE, Google Scholar and the Cochrane Library up to December 25, 2014, to identify published cohort or case-control studies. 17 studies, including 6660 patients carrying P. aeruginosa, were identified. The pooling analysis indicated that patients infected with CRPA had significantly higher mortality than those infected with carbapenem-susceptible P. aeruginosa (CSPA) (crude OR = 1.64; 95%CI = 1.40, 1.93; adjusted OR = 2.38; 95%CI = 1.53, 3.69). The elevated risk of mortality in patients with CRPA infection was not lessened when stratified by study design, sites of infection, or type of carbapenem, except that the estimate effect vanished in CRPA high-incidence region, South America (crude OR = 1.12; 95%CI = 0.64, 1.99). Begg's (z = 0.95, p = 0.34) and Egger's test (t = 1.23, p = 0.24) showed no evidence of publication bias. Our results suggest that carbapenem resistance may increase the mortality of patients with P. aeruginosa infection, whether under univariate or multivariate analysis.

Rapid identification of pathogens in positive blood culture of patients with sepsis: review and meta-analysis of the performance of the sepsityper kit

Sepsis is one of the leading causes of deaths, and rapid identification (ID) of blood stream infection is mandatory to perform adequate antibiotic therapy. The advent of MALDI-TOF Mass Spectrometry for the rapid ID of pathogens was a major breakthrough in microbiology. Recently, this method was combined with extraction methods for pathogens directly from positive blood cultures. This review summarizes the results obtained so far with the commercial Sepsityper sample preparation kit, which is now approved for in vitro diagnostic use. Summarizing data from 21 reports, the Sepsityper kit allowed a reliable ID on the species level of 80% of 3320 positive blood culture bottles. Gram negative bacteria resulted consistently in higher ID rates (90%) compared to Gram positive bacteria (76%) or yeast (66%). No relevant misidentifications on the genus level were reported at a log(score)cut-off of 1.6. The Sepsityper kit is a simple and reproducible method which extends the MALDI-TOF technology to positive blood culture specimens and shortens the time to result by several hours or even days. In combination with antibiotic stewardship programs, this rapid ID allows a much faster optimization of antibiotic therapy in patients with sepsis compared to conventional workflows.

[First-line anti-infective treatment in sepsis]

BACKGROUND

The Surviving Sepsis Campaign strongly recommends that intravenous antibiotic therapy should be started as early as possible, ideally within the first hour of recognition of severe sepsis or septic shock. There is ample evidence that failure to initiate early antimicrobial treatment correlates with increased morbidity and mortality.

OBJECTIVES

The purpose of this work was to review the recent literature regarding optimal initial antimicrobial treatment in patients with severe sepsis and sepsis shock.

MATERIALS AND METHODS

A literature review was performed.

RESULTS

The most frequently quoted papers claiming the overriding prognostic importance of early administered antibiotics are retrospective data analyses. However, an equivalent number of studies report that a group of septic patients do not benefit from early administration of antibiotics, but can also be harmed. In these patients, watchful waiting with administration of a targeted antibiotic can be used, thus, avoiding the possible collateral damage from excessive treatment with antibiotics. Treatment with monotherapy is adequate in most cases.

CONCLUSION

The administration of antibiotics based on the local epidemiology should be initiated quickly in critically ill patients with severe sepsis and septic shock. In patients who are not in septic shock, treatment can be withheld, while awaiting further studies or clinical assessment to confirm the suspicion of infection.

European perspective and update on the management of nosocomial pneumonia due to methicillin-resistant Staphylococcus aureus after more than 10 years of experience with linezolid

Methicillin-resistant Staphylococcus aureus (MRSA) is an important cause of antimicrobial-resistant hospital-acquired infections worldwide and remains a public health priority in Europe. Nosocomial pneumonia (NP) involving MRSA often affects patients in intensive care units with substantial morbidity, mortality and associated costs. A guideline-based approach to empirical treatment with an antibacterial agent active against MRSA can improve the outcome of patients with MRSA NP, including those with ventilator-associated pneumonia. New methods may allow more rapid or sensitive diagnosis of NP or microbiological confirmation in patients with MRSA NP, allowing early de-escalation of treatment once the pathogen is known. In Europe, available antibacterial agents for the treatment of MRSA NP include the glycopeptides (vancomycin and teicoplanin) and linezolid (available as an intravenous or oral treatment). Vancomycin has remained a standard of care in many European hospitals; however, there is evidence that it may be a suboptimal therapeutic option in critically ill patients with NP because of concerns about its limited intrapulmonary penetration, increased nephrotoxicity with higher doses, as well as the emergence of resistant strains that may result in increased clinical failure. Linezolid has demonstrated high penetration into the epithelial lining fluid of patients with ventilator-associated pneumonia and shown statistically superior clinical efficacy versus vancomycin in the treatment of MRSA NP in a phase IV, randomized, controlled study. This review focuses on the disease burden and clinical management of MRSA NP, and the use of linezolid after more than 10 years of clinical experience.

Risk factors, outcome and impact of empirical antimicrobial treatment in extended-spectrum β-lactamase-producing Escherichia coli bacteraemia

BACKGROUND

To investigate patient characteristics and empirical antimicrobial treatment of extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) bacteraemia, to determine risk factors, outcome and impact of empirical antimicrobial treatment.

METHODS

We performed a retrospective case-control study of all patients diagnosed with ESBL-EC from January 2011 to September 2012. The control group consisted of patients with non-ESBL E. coli bacteraemia. The groups were compared with respect to empirical treatment, risk factors and outcome, using univariate and multivariate analysis.

RESULTS

The study consisted of 70 consecutive cases of ESBL-producing and 140 controls of non-ESBL-producing E. coli bacteraemia. ESBL-EC prevalence of bloodstream invasive E. coli isolates was 6.1%. The independent risk factor found for ESBL-EC bacteraemia was a prior culture with ESBL production (p < 0.001). A higher frequency of inappropriate empirical antibiotic treatment (p < 0.001) and a trend towards worse outcome was observed in patients infected with ESBL-EC and empirical guidelines were more often not followed (p = 0.013). If the guidelines were followed this was associated with adequate initial antibiotic treatment (p < 0.001).

CONCLUSIONS

Patients with ESBL-EC frequently received inappropriate empirical treatment and guidelines were more often not followed. A prior culture of ESBL-producing bacteria was an independent predictor and risk factor for ESBL-EC bacteraemia. Since the prevalence of ESBL-producing E. coli is increasing the importance of adequate guidelines must be emphasized.

How to assist clinicians in improving antimicrobial prescribing: tools and interventions provided by stewardship programs

In the last decade, there has been an exponential increase in the microorganisms resistant to antimicrobials and a significant increase in the cost of these types of drugs. This phenomenon has increased interest in the development of interventions for counseling on and control of the use of antimicrobials, referred to as stewardship programs. In this article we review, from various points of view, the tools that have been developed with this purpose. First, we highlight the value of locally adapted guidelines and clinical pathways as an essential part of the operational process. Then we emphasize the importance of the relationship between microbiologists and clinicians for the accurate transmission of the information provided by blood cultures to make the most appropriate choice of antimicrobial for the patient's treatment. We also review the computerized tools that have facilitated the correct use of antimicrobials according to the controls established by the departments of pharmacy. Based on the previous tools, some programs based on "bedside recommendations" provided by multidisciplinary teams have been developed for optimizing the rational use of antimicrobials (PROA programs). Finally, we comment on the peculiarities of the programs targeting antifungals that have been developed in recent years.

Risk factors for drug-resistant bloodstream infections in patients with systemic lupus erythematosus

OBJECTIVE

To identify risk factors for developing drug-resistant bacterial infections in patients with systemic lupus erythematosus (SLE).

METHODS

A retrospective, case-control study was performed. Patients fulfilled American College of Rheumatology criteria for SLE and had an episode of bloodstream infection between 2001 and 2012. Cases were defined as those with bloodstream infection caused by drug-resistant bacteria (Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, or extended-spectrum-β-lactalamase-producing Escherichia coli); while controls had susceptible strains of S. aureus or E. coli. Differences between groups were analyzed by Student t test or Mann-Whitney U test. Association between variables was assessed by OR (CI 95%). Multivariate analysis was performed by binary logistic regression model.

RESULTS

Forty-four patients were included in each group. Variables associated with drug-resistant bloodstream infection were history of central nervous system activity; hematological activity, immunosuppressive treatment and prednisone dose at the time of the infection; and low C3 levels, antibiotic use, or hospitalization in the previous 3 months. In multivariate analysis, variables that remained significant were low C3 previous to infection (OR 3.12, CI 95% 1.91-8.22), previous hospitalization (OR 2.22, CI 95% 1.42-4.10), and prednisone dose at the time of infection (OR 1.10, CI 95% 1.04-1.22).

CONCLUSION

Low C3 levels, recent hospitalization, and prednisone dose at time of infection are independent risk factors for acquiring drug-resistant bacteria in patients with SLE. Although the present data do not fully support a change in initial treatment-decision strategies, this information could lead to prospective studies designed to address this issue, which could determine the best approach in clinical practice.

Carbapenem-resistant Pseudomonas aeruginosa in Taiwan: Prevalence, risk factors, and impact on outcome of infections

BACKGROUND

The prevalence and clinical impact on mortality of carbapenem-resistant Pseudomonas aeruginosa (CRPA) is unclear in Taiwan. We aim to clarify these clinical issues by using data from the Taiwan Surveillance of Antimicrobial Resistance (TSAR) program.

METHODS

Patients from five hospitals with their P. aeruginosa isolates collected by TSAR II-VII (2000-2010) program were considered as the potential study population. All patients with CRPA were enrolled as case patients. Patients with carbapenem-susceptible P. aeruginosa were randomly selected in a 1:1 ratio to case patients as control patients. CRPA isolates were tested for the presence of carbapenemase-producing genes. The clinical data were collected to identify risk factors for CRPA carriage and mortality of P. aeruginosa infection.

RESULTS

The overall prevalence of CRPA was 10.2% (349/3408), which increased significantly by the TSAR period (p = 0.007). Among the 164 enrolled patients, the risk factor for carrying CRPA was previous fluoroquinolone exposure (p = 0.004). The risk factors for mortality among 80 patients with infection by P. aeruginosa included: intensive care unit (ICU) setting, receipt of antifungal therapy, and presence of invasive devices (p = 0.001, 0.010, and 0.017; respectively). Carbapenem resistance did not play a role. Among the 82 CRPA isolates enrolled in this study, 15 isolates were found to carry carbapenemase-producing genes.

CONCLUSION

In Taiwan, the prevalence of CRPA and carriage of carbapenemase-producing genes was high. However, carbapenem resistance did not play a role in the mortality of patients with P. aeruginosa infections.

Immune response in severe infection: could life-saving drugs be potentially harmful?

Critically ill patients suffer a high rate of nosocomial infection with secondary sepsis being a common cause of death. Usage of antibiotics and catecholamines is often necessary, but it can compromise complex immune response to infection. This review explores influence of these life-saving drugs on host immune response to severe infection.

Polymicrobial bloodstream infections: Epidemiology and impact on mortality

The aim of this study was to investigate the impact of polymicrobial bloodstream infections (pBSIs) on the outcome of sepsis in an area where antimicrobial resistance is of concern. This was a retrospective analysis of data collected prospectively from patients developing BSI outside of an intensive care unit (non-ICU patients) or after ICU admission. Demographics and clinical characteristics were compared for patients with pBSI versus monomicrobial BSI (mBSI) and following stratification by ICU or non-ICU and severity of sepsis status. Possible risk factors for adverse outcome were explored by multivariate analysis, and outcomes were measured by Cox regression analysis. Among 412 patients with BSI, 47 patients (11.4%) with pBSI were recorded; compared with patients with mBSI, they had significantly higher APACHE II scores and presented more frequently with severe sepsis/septic shock. The all-cause 28-day mortality was significantly higher for pBSI versus mBSI (38.3% vs. 24.7%; P=0.033), whereas appropriateness of treatment was comparable (78.7% vs. 86.6%). Primary bacteraemia by combinations of Enterococcus faecalis, Klebsiella pneumoniae and Acinetobacter baumannii was predominant among pBSIs; in mBSIs, urinary tract infections by Escherichia coli, K. pneumoniae or Pseudomonas aeruginosa predominated. Multivariate analysis demonstrated pBSI as a significant contributor to 28-day mortality (HR=1.86; P=0.039), along with presence of two or more co-morbidities (HR=2.35; P=0.004). In conclusion, pBSIs differed epidemiologically from mBSIs, with the emergence of enterococcal species, and portended an almost two-fold increased risk of 28-day mortality. Prospective studies are warranted to elucidate possibly modifiable factors.

Predictors of mortality in patients with infections due to multi-drug resistant Gram negative bacteria: the study, the patient, the bug or the drug?

OBJECTIVE

To study the predictors of mortality among patients with multi-drug resistant Gram negative (MDRGN) infections and the role of MDRGN bacteria in the outcome of such patients.

METHODS

PubMed and Scopus databases were searched (until June 30, 2012). Data were extracted and analyzed using the technique of meta-analysis.

RESULTS

30 studies (25 retrospective) were included in the analysis; 9 provided data on predictors of mortality for MDRGN infections only, while 21 provided data for MDRGN vs non-MDRGN infections. Acinetobacter spp were the most commonly studied bacteria followed by Pseudomonas aeruginosa and Enterobacteriaceae. Significant diversity was observed among studies regarding the evaluated predictors of mortality. Infection severity and underlying diseases were the most commonly reported independent predictors of mortality followed by multidrug resistance, inappropriate treatment and increasing age. In studies that included only patients with MDRGN infections, cancer (RR 1.65, 95% CI 1.13-2.39) and prior or current ICU stay (1.27, 1.02-1.56) were associated with mortality. In studies that included patients with MDRGN and non-MDRGN infections, septic shock (3.36, 2.47-4.57), ICU stay (2.15, 1.45-3.20), pneumonia (1.65, 1.09-2.52), isolation of MDRGN bacteria (1.49, 1.21-1.83), inappropriate definitive (2.05, 1.12-3.76) and empirical treatment (1.37, 1.25-1.51), and male gender (1.13, 1.05-1.21) were most commonly observed in patients who died than patients who survived.

CONCLUSION

Significant diversity and statistical heterogeneity was observed. Beyond comorbidity and severity scores, MDR and inappropriate treatment were also identified as predictors of mortality.

Impact of inappropriate empiric antimicrobial therapy on mortality of septic patients with bacteremia: a retrospective study

Background. Inappropriate empiric antimicrobials could be a major cause of unfavorable mortality rates in co-morbid patients. This study aimed to assess the prevalence and impact of first-dose and 24-hour inappropriate antimicrobials on mortality rates of bacteremic septic patients. Methods. A retrospective cohort study was employed. Case record forms of patients diagnosed as sepsis, severe sepsis, or septic shock with positive hemoculture during 2009 were retrieved from the medical wards, Siriraj Hospital. Demographic data, antimicrobial use, types of bacteria isolated from blood and susceptibilities, patients' comorbidities, 28-day and overall mortality rates were collected and analyzed. Results. There were 229 cases, mean age (SD) of 63.5 (17.2) years and mean (SD) APACHE II score of 24.7 (6.8). The prevalence of first-dose and 24-hour inappropriate antimicrobials was 29.7% and 25.3%, respectively. The 28-day and overall mortality rates between first-dose inappropriate and appropriate antimicrobial were 67.6% versus 60.2% (P = 0.301) and 75.0% versus 68.3% (P = 0.345), consequently. Patients with septic shock and inappropriate first-dose antimicrobials significantly had higher 28-day mortality rate (61.6% versus 41.9%; P = 0.017). Conclusion. Higher mortality rates in bacteremic septic patients were substantially associated with inappropriate first-dose antimicrobials and 3-hour delayed antimicrobial administration after sepsis diagnosis.

Bench-to-bedside review: Rapid molecular diagnostics for bloodstream infection--a new frontier?

Among critically ill patients, the diagnosis of bloodstream infection poses a major challenge. Current standard bacterial identification based on blood culture platforms is intrinsically time-consuming and slow. The continuous evolvement of molecular techniques has the potential of providing a faster, more sensitive and direct identification of causative pathogens without prior need for cultivation. This may ultimately impact clinical decision-making and antimicrobial treatment. This review summarises the currently available technologies, their strengths and limitations and the obstacles that have to be overcome in order to develop a satisfactory bedside point-of-care diagnostic tool for detection of bloodstream infection.

Impact of appropriate antimicrobial therapy on mortality associated with Acinetobacter baumannii bacteremia: relation to severity of infection

BACKGROUND

The efficacy of antimicrobial therapy for Acinetobacter baumannii bacteremia has been difficult to establish because of confounding by underlying diseases, severity of infection, and differences in the pathogenicity of Acinetobacter species. This retrospective study was conducted to evaluate the effect of appropriate antimicrobial therapy on 14-day mortality after adjustment for multiple risk factors.

METHODS

The population consisted of 252 patients with monomicrobial A. baumannii bacteremia admitted to a large teaching hospital in Taiwan. The isolates were identified to species level using reference molecular methods. Predictors of 14-day mortality were determined by logistic regression analysis. The influence of severity of infection, determined by Acute Physiology and Chronic Health Evaluation (APACHE) II score, on the impact of appropriate use of antimicrobials on 14-day mortality was assessed by including an interaction term.

RESULTS

The overall 14-day mortality rate was 29.8% (75 of 252 patients). The unadjusted mortality rate for appropriate antimicrobial therapy was 13.2% (12 of 91 patients). Appropriate therapy was independently associated with reduced mortality (odds ratio [OR], 0.22; 95% confidence interval [CI], .01-.50; P < .001), and the effect was influenced by APACHE II score (OR for interaction term, 0.90; 95% CI, .82-.98; P= .02). A subgroup analysis revealed that the benefit of appropriate therapy was limited to patients with high APACHE II scores (OR for patients with scores >25 and ≤ 35, 0.16 [95% CI, .07-.37]; OR for those with scores >35, 0.06; 95% CI, .01-.25).

CONCLUSIONS

Appropriate antimicrobial therapy significantly reduced 14-day mortality for A. baumannii bacteremia in severely ill patients.

The impact of anti-infective drug shortages on hospitals in the United States: trends and causes

Anti-infective shortages pose significant logistical and clinical challenges to hospitals and may be considered a public health emergency. Anti-infectives often represent irreplaceable life-saving treatments. Furthermore, few new agents are available to treat increasingly prevalent multidrug-resistant pathogens. Frequent anti-infective shortages have substantially altered patient care and may lead to inferior patient outcomes. Because many of the shortages stem from problems with manufacturing and distribution, federal legislation has been introduced but not yet enacted to provide oversight for the adequate supply of critical medications. At the local level, hospitals should develop strategies to anticipate the impact and extent of shortages, to identify therapeutic alternatives, and to mitigate potential adverse outcomes. Here we describe the scope of recent anti-infective shortages in the United States and explore the reasons for inadequate drug supply.

Prospective multicenter study of the impact of carbapenem resistance on mortality in Pseudomonas aeruginosa bloodstream infections

The impact of antimicrobial resistance on clinical outcomes is the subject of ongoing investigations, although uncertainty remains about its contribution to mortality. We investigated the impact of carbapenem resistance on mortality in Pseudomonas aeruginosa bacteremia in a prospective multicenter (10 teaching hospitals) observational study of patients with monomicrobial bacteremia followed up for 30 days after the onset of bacteremia. The adjusted influence of carbapenem resistance on mortality was studied by using Cox regression analysis. Of 632 episodes, 487 (77%) were caused by carbapenem-susceptible P. aeruginosa (CSPA) isolates, and 145 (23%) were caused by carbapenem-resistant P. aeruginosa (CRPA) isolates. The median incidence density of nosocomial CRPA bacteremia was 2.3 episodes per 100,000 patient-days (95% confidence interval [CI], 1.9 to 2.8). The regression demonstrated a time-dependent effect of carbapenem resistance on mortality as well as a significant interaction with the Charlson index: the deleterious effect of carbapenem resistance on mortality decreased with higher Charlson index scores. The impact of resistance on mortality was statistically significant only from the fifth day after the onset of the bacteremia, reaching its peak values at day 30 (adjusted hazard ratio for a Charlson score of 0 at day 30, 9.9 [95% CI, 3.3 to 29.4]; adjusted hazard ratio for a Charlson score of 5 at day 30, 2.6 [95% CI, 0.8 to 8]). This study clarifies the relationship between carbapenem resistance and mortality in patients with P. aeruginosa bacteremia. Although resistance was associated with a higher risk of mortality, the study suggested that this deleterious effect may not be as great during the first days of the bacteremia or in the presence of comorbidities.

Impact of definitive therapy with beta-lactam monotherapy or combination with an aminoglycoside or a quinolone for Pseudomonas aeruginosa bacteremia

Background

Bacteremia by Pseudomonas aeruginosa represents one severe infection. It is not clear whether beta-lactam monotherapy leads to similar rates of treatment success compared to combinations of beta-lactams with aminoglycosides or quinolones.

Methods

Retrospective cohort study from 3 tertiary hospitals (2 in Greece and 1 in Italy). Pseudomonas aeruginosa isolates were susceptible to a beta-lactam and an aminoglycoside or a quinolone. Patients received appropriate therapy for at least 48 hours. Primary outcome of interest was treatment success in patients with definitive beta-lactam combination therapy compared to monotherapy. Secondary outcomes were treatment success keeping the same empirical and definitive regimen, mortality, and toxicity.

Results

Out of 92 bacteremias there were 54 evaluable episodes for the primary outcome (20 received monotherapy). Treatment success was higher with combination therapy (85%) compared to beta-lactam monotherapy (65%), however not statistically significantly [Odds ratio (OR) 3.1; 95% Confidence Interval (CI) 0.69–14.7, p = 0.1]. Very long (>2 months) hospitalisation before bacteremia was the only factor independently associated with treatment success (OR 0.73; 95% CI 0.01–0.95, p = 0.046), however this result entailed few episodes. All-cause mortality did not differ significantly between combination therapy [6/31 (19%)] and monotherapy [8/19 (42%)], p = 0.11. Only Charlson comorbidity index was associated with excess mortality (p = 0.03).

Conclusion

Our study, in accordance with previous ones, indicates that the choice between monotherapy and combination therapy may not affect treatment success significantly. However, our study does not have statistical power to identify small or moderate differences. A large randomized controlled trial evaluating this issue is justified.

Impact of carbapenem resistance and receipt of active antimicrobial therapy on clinical outcomes of Acinetobacter baumannii bloodstream infections

Nosocomial Acinetobacter baumannii bloodstream infections occur with significant prevalence and mortality. The relationship between carbapenem resistance in A. baumannii and patient outcomes remains unclear. A retrospective cohort study was conducted on patients with A. baumannii bacteremia. Outcomes, controlling for confounders, were compared for carbapenem-nonresistant A. baumannii (CNRAB) and carbapenem-resistant A. baumannii (CRAB). The primary outcome studied was all-cause hospital mortality, and the secondary endpoints evaluated were time to mortality, time to negative cultures, and length of stay postinfection for survivors. A total of 79 patients, 37 infected with CRAB and 42 with CNRAB, were studied. Hospital mortality was greater in the CRAB group as determined based on bivariate analysis (P < 0.01); however, this effect was nullified when controlling for relevant confounders with logistic regression and a Cox proportional-hazards model (P = 0.71 and 0.75, respectively). Values for time to mortality and time to negative cultures did not differ between the groups. The median number of days of stay postinfection for survivors was greater for the CRAB group than the CNRAB group (14 versus 6.5; P < 0.01). Patients who received active antimicrobial therapy were less likely to die (93.5% versus 74.2%; P = 0.02), regardless of carbapenem susceptibility classifications, and this result was robust in the multivariate model (P = 0.02). Trends existed for improved outcomes in patients receiving an active beta-lactam, and patients fared worse if they had received a polymyxin as an active agent. Patients with CRAB bloodstream infections were more chronically ill and had more comorbidities. Inactive therapy was more important than carbapenem susceptibility with respect to outcomes, was a strong predictor of death, and is potentially modifiable.

Epidemiology and clinical outcomes of bloodstream infections among lupus patients

Infection is an important cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). This study was aimed at characterizing bloodstream infections in these patients and analysing factors associated with long term outcome. For this purpose, episodes of significant bacteraemia diagnosed from January 1991 to December 2006 among patients with SLE at a single centre were identified through a central database and clinical and analytical variables were recorded regarding short- and long-term follow-up. Univariate and multivariable analysis were performed to identify factors associated with long-term outcome. Thirty-eight SLE patients had 48 episodes of significant bacteraemia, with a 30-day mortality rate of 6.25%. Escherichia coli and Staphylococcus aureus were the leading Gram-negative and Gram-positive pathogens, respectively. After a median follow-up of 25 months, eight of these 38 patients (21.1%) had a further episode of bacteraemia and 13 of them (34.21%) died. Community-acquired bacteraemia and C reactive protein levels lower than 8 mg/dl during episodes were factors associated with lower long-term mortality. These results reinforce previous findings suggesting that lupus patients with bacteraemia episodes have poor long-term outcomes

Infection in the critically ill--questions we should be asking

Best practice in infection control and management in the critically ill continues to generate considerable debate. The wide variation in current practice is witness to this continuing uncertainty. In large part this is due to the lack of a decent evidence base and to an over-reliance on deep-set dogma. Data that go against the grain are often conveniently overlooked and political imperatives frequently supervene. This article highlights some of these discrepancies and argues for a more balanced, scientific approach. In this time of financial restraint, we need to identify true priorities from both health and economic perspectives, and to see what practices can safely and effectively be modified or abandoned.

Differences in clinical outcomes in patients with vancomycin-resistant enterococci according to linezolid susceptibility

STUDY OBJECTIVE

To evaluate the differences in clinical outcomes in patients with linezolid-intermediate or -resistant vancomycin-resistant enterococci (LIRVRE) isolates, as defined by the presence of the G2576T mutation, compared with patients who had linezolid-susceptible VRE (LSVRE) isolates in order to further discern the clinical relevance of linezolid resistance associated with this mutation.

DESIGN

Retrospective cohort study.

SETTING

Large tertiary care academic medical center.

PATIENTS

Eighteen adults (mean age 55.4 yrs) with LIRVRE (case patients) who were frequency matched to 54 adults (mean age 58.1 yrs) with LSVRE (control patients) in a 1:3 ratio based on site of culture and VRE species.

MEASUREMENTS AND MAIN RESULTS

Linezolid resistance was determined by phenotype and genotype (G2576T mutation by polymerase chain reaction). Patients with LIRVRE received more linezolid before isolation of the organism than did those with LSVRE (mean 8.6 vs 0.2 days, p<0.001). No difference in mortality was found; however, compared with controls, patients with LIRVRE were more likely to be transferred to the intensive care unit (56% vs 28%, p=0.032), had more surgical procedures for VRE (39% vs 15%, p=0.029), and had more echocardiograms performed (44% vs 19%, p=0.028) as a result of their VRE. Multivariate analysis revealed that surviving case patients had an increased duration of culture positivity of approximately 1.5 days (p=0.049) and a near statistically significant increase of postculture length of stay of approximately 2 days (p=0.053).

CONCLUSION

The clinical relevance of the G2576T mutation among enterococci remains unclear; however, the increased morbidity and resource utilization among patients with LIRVRE is a finding of concern. Careful monitoring of genotypically confirmed LIRVRE emergence and ongoing epidemiologic studies will be critical to better characterize the clinical relevance of linezolid resistance.

Systematic review and meta-analysis of the efficacy of appropriate empiric antibiotic therapy for sepsis

Quantifying the benefit of early antibiotic treatment is crucial for decision making and can be assessed only in observational studies. We performed a systematic review of prospective studies reporting the effect of appropriate empirical antibiotic treatment on all-cause mortality among adult inpatients with sepsis. Two reviewers independently extracted data. Risk of bias was assessed using the Newcastle-Ottawa score. We calculated unadjusted odds ratios (ORs) with 95% confidence intervals for each study and extracted adjusted ORs, with variance, methods, and covariates being used for adjustment. ORs were pooled using random-effects meta-analysis. We examined the effects of methodological and clinical confounders on results through subgroup analysis or mixed-effect meta-regression. Seventy studies were included, of which 48 provided an adjusted OR for inappropriate empirical antibiotic treatment. Inappropriate empirical antibiotic treatment was associated with significantly higher mortality in the unadjusted and adjusted comparisons, with considerable heterogeneity occurring in both analyses (I(2) > 70%). Study design, time of mortality assessment, the reporting methods of the multivariable models, and the covariates used for adjustment were significantly associated with effect size. Septic shock was the only clinical variable significantly affecting results (it was associated with higher ORs). Studies adjusting for background conditions and sepsis severity reported a pooled adjusted OR of 1.60 (95% confidence interval = 1.37 to 1.86; 26 studies; number needed to treat to prevent one fatal outcome, 10 patients [95% confidence interval = 8 to 15]; I(2) = 46.3%) given 34% mortality with inappropriate empirical treatment. Appropriate empirical antibiotic treatment is associated with a significant reduction in all-cause mortality. However, the methods used in the observational studies significantly affect the effect size reported. Methods of observational studies assessing the effects of antibiotic treatment should be improved and standardized.