Antistaphylococcal penicillins versus cephalosporins for definitive treatment of meticillin-susceptible Staphylococcus aureus bacteraemia: a systematic review and meta-analysis

Comparable Effectiveness of Cefuroxime and Piperacillin-Tazobactam as Empirical Therapy for Methicillin-Susceptible Staphylococcus aureus Bacteremia

Our objective was to examine whether empirical antimicrobial therapy (EAT) against methicillin-susceptible Staphylococcus aureus bacteremia (MS-SAB) with piperacillin-tazobactam (TZP), cefuroxime or combination therapy with one of these was differentially associated with 7-, 30-, and 90- day all-cause mortality or MS-SAB relapse. A multicenter retrospective cohort study of adults with MS-SAB from 2009 through 2018 was used, and 7-, 30-, 90-day mortality and relapse within 90 days were assessed and expressed as hazard ratio (HR) with a 95% confidence interval (95% CI) using Cox proportional hazard regression analysis. Matching of the two monotherapy groups was performed using propensity score matching. In total, 1158 MS-SAB cases were included and received one of three EAT regimens: TZP (n = 429), cefuroxime (n = 337), or TZP or cefuroxime with one or more additional effective antimicrobial (n = 392). The overall 30-day mortality was 28.0% (25.5 to 30.3%). After adjustment and matching, there was no significant difference in 7-, 30-, or 90-day mortality between the therapy groups. The matched HR of death was 0.81 (95% CI, 0.38 to 1.76) at 7 days, 0.82 (95% CI, 0.47 to 1.46) at 30 days, and 0.81 (95% CI, 0.50 to 1.32) at 90 days for TZP compared with cefuroxime. Adjusted HR of 90-day relapse was insignificant between the three therapy groups: TZP: 1.55 (95% CI, 0.54 to 4.43); combination therapy: 1.73 (95% CI, 0.62 to 4.80) compared to cefuroxime. There was no significant difference in 7-, 30-, or 90-day mortality or relapse between MS-SAB patients treated with empirical TZP or cefuroxime after adjustment and matching of covariables.

IMPORTANCE This multicenter retrospective matched cohort study evaluated the effect of empirical antimicrobial therapy on the clinical outcome of methicillin-susceptible Staphylococcus aureus bacteremia (MS-SAB) in >1100 adult patients. To the best of our knowledge, this is the largest study to date evaluating the effect of empirical treatment on the MS-SAB outcome. Importantly, the study found no significant difference in either short- or long-term mortality nor relapse between patients with MS-SAB receiving empirical treatment with cefuroxime or piperacillin-tazobactam. As such, this study provides crucial contemporary data supporting the widespread clinical practice of initiating empirical antimicrobial therapy of sepsis with β-lactam-β-lactamase-inhibitor.

The Cost-effectiveness of Cefazolin Compared With Antistaphylococcal Penicillins for the Treatment of Methicillin-Sensitive Staphylococcus aureus Bacteremia

Background

Methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia is associated with significant morbidity, mortality, and hospitalization costs. Cefazolin and antistaphylococcal penicillins (ASPs), such as nafcillin, are the preferred treatments for MSSA bacteremia. The aim of this study was to compare the cost-effectiveness of each approach.

Methods

We constructed a decision-analytic model comparing the use of cefazolin with ASPs for the treatment of MSSA bacteremia. Cost-effectiveness was determined by calculating deaths averted and incremental cost-effectiveness ratios (ICERs). Uncertainty was addressed by plotting cost-effectiveness planes and acceptability curves for various willingness-to-pay thresholds.

Results

In the base-case analysis, the cost associated with the cefazolin strategy was $38 863.1, and the associated probability of survival was 0.91. For the ASP strategy, the cost was $48 578.8, and the probability of survival was 0.81. The incremental difference in cost between the 2 strategies was $9715.7, with hospital length of stay being the main driver of cost, and the incremental difference in effectiveness was 0.10. Overall, cefazolin results in savings of $97 156.8 per death averted (ICER, $–97 156.8/death averted). In the probabilistic analysis, at a willingness-to-pay of $50 000, cefazolin had a 68% chance of being cost-effective compared with ASPs. In cost-effectiveness acceptability curves, the cefazolin strategy was cost-effective in 73.5%–81.8% of simulations compared with ASP for a willingness-to-pay ranging up to $50 000.

Conclusions

The use of cefazolin is a cost-effective strategy for the treatment of MSSA bacteremia and, when clinically appropriate, this strategy results in considerable health care cost-savings.

Ceftriaxone as an Alternative Therapy for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteremia after Initial Clearance of Bloodstream Infection

Introduction

Staphylococcus spp. represent the leading cause of hospital-acquired infections and second-most frequent pathogen in bloodstream infections. Methicillin-susceptible S. aureus (MSSA) comprise approximately half of all S. aureus isolates. Standard-of-care therapies (SOCTs) display high treatment success but require frequent dosing, are problematic in penicillin allergic patients, and are nephrotoxic. Ceftriaxone may represent an alternative treatment option.

Methods

Adult patients hospitalized from January 2015 through June 2016 with positive MSSA blood cultures and treated with SOCT or ceftriaxone for ≥48 hours were included. Exclusion criteria were receipt of vancomycin or concomitant systemic antimicrobials with activity against MSSA, polymicrobial infections, and pregnant patients. Additional data collected included demographics, source/site of infection, and treatment. The primary endpoint was clinical cure (normalization of white blood cell count and temperature within 7 days and clearance of bloodstream within 7 days). Readmission within 60 days, length of stay, and discharge disposition were collected.

Results

A total of 43 patients were included: 23 receiving SOCT and 20 receiving ceftriaxone group. Sixteen patients received SOCT prior to ceftriaxone while 4 patients were initiated on ceftriaxone. Clinical cure was observed in 18/23 (78%) and 10/20 (50%), respectively (P=0.052). Clinical failure was driven by leukocytosis despite clearance of their bloodstream infection in 3/23 (13%) SOCT group compared to 8/20 (40%) in the ceftriaxone group (P=0.043). Six patients (SOCT: 2, ceftriaxone: 4; p=0.669) had infection-related readmissions, and 1 death per group was observed.

Conclusion

Ceftriaxone poses a reasonable alternative to consider for MSSA bacteremia when cost and feasibility are concerns for outpatient parenteral therapy after initial clearance of bloodstream infections.

How automatic notification of infectious disease specialists impacted the management of Staphylococcus aureus bacteremia in a community hospital setting

Objective: The objective of this study was to review the impact of an automatic email notification to infectious disease consultants.

Design: Cases were identified from a community hospital system microbiology database by at least one positive blood culture. Records were reviewed both before (2013 and 2014) and after (2015 and 2016) the implementation of the automated email system (intervention). Prior to this policy, consultation with the infectious disease (ID) specialist was at the discretion of the primary team.

Results: There were no significant differences in 30-day mortality between the two groups (18 vs 20%, p = 0.10). However, a trend of shorter hospital stays (12.2 vs 9.5 days, p = 0.03) and reduced 30 day readmissions (40% vs 19%, p = 0.03) was observed and antibiotics prescribed for complicated cases was more appropriate (57% vs 85%, p = 0.004).

Conclusions: In this study population, the implementation of an automatic email generator to ID specialists was associated with a shorter hospital length of stay, less 30-day readmissions and more appropriate length of antibiotics prescribed in complicated cases of SAB. The authors recommend future studies replicating the methodology employed here with larger sample sizes before consideration of employing a similar automatic email ID consult generation at other health systems.

Adjunctive Clavulanic Acid Abolishes the Cefazolin Inoculum Effect in an Experimental Rat Model of Methicillin-Sensitive Staphylococcus aureus Endocarditis

We tested the ability of clavulanic acid to restore the efficacy of cefazolin against Staphylococcus aureus TX0117, which exhibits the cefazolin inoculum effect (CzIE). In the rat infective endocarditis model, the coadministration of cefazolin plus clavulanic acid resulted in a significant reduction of bacterial counts (7.1 ± 0.5 log₁₀ CFU/g) compared to that with cefazolin alone (2 ± 0.6 log₁₀ CFU/g; P < 0.0001). The addition of a β-lactamase inhibitor may be a viable strategy for overcoming the CzIE.

Synthesis of dibenzothiazepine analogues by one-pot S-arylation and intramolecular cyclization of diaryl sulfides and evaluation of antibacterial properties

Dibenzothiazepine analogues containing lactam, amidine and imine moieties were prepared from 2-aminophenyl disulfides via one-pot S-arylation. The S-arylation involved cleavage of an S-S bond of disulfides and SNAr reaction in aqueous ammonia solution of L-cysteine to afford diaryl sulfides. Dibenzothiazepine analogues having lactam and amidine moieties were obtained by cyclization of the corresponding diaryl sulfides under acidic conditions. One-pot S-arylation of 2-bromo-5-nitrobenzaldehyde gave dibenzothiazepine analogues with an imine moiety in one step through intramolecular cyclization. Compounds with antibacterial activities against Staphylococcus aureus and Escherichia coli were obtained.

The Cefazolin Inoculum Effect Is Associated With Increased Mortality in Methicillin-Susceptible Staphylococcus aureus Bacteremia

Background

Recent studies have favored the use of cefazolin over nafcillin for the treatment of methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia. The clinical influence of the cefazolin inoculum effect (CzIE) in the effectiveness of cephalosporins for severe MSSA infections has not been evaluated.

Methods

We prospectively included patients from 3 Argentinian hospitals with S. aureus bacteremia. Cefazolin minimum inhibitory concentrations (MICs) were determined at standard (10⁵ colony-forming units [CFU]/mL) and high (10⁷ CFU/mL) inoculum. The CzIE was defined as an increase of MIC to ≥16 µg/mL when tested at high inoculum. Whole-genome sequencing was performed in all isolates.

Results

A total of 77 patients, contributing 89 MSSA isolates, were included in the study; 42 patients (54.5%) had isolates with the CzIE. In univariate analysis, patients with MSSA exhibiting the CzIE had increased 30-day mortality (P = .034) and were more likely to have catheter-associated or unknown source of bacteremia (P = .033) compared with patients infected with MSSA isolates without the CzIE. No statistically significant difference between the groups was observed in age, clinical illness severity, place of acquisition (community vs hospital), or presence of endocarditis. The CzIE remained associated with increased 30-day mortality in multivariate analysis (risk ratio, 2.65; 95% confidence interval, 1.10–6.42; P = .03). MSSA genomes displayed a high degree of heterogeneity, and the CzIE was not associated with a specific lineage.

Conclusions

In patients with MSSA bacteremia where cephalosporins are used as firstline therapy, the CzIE was associated with increased 30-day mortality. Clinicians should be cautious when using cefazolin as firstline therapy for these infections.

Systematic Review and Meta-analysis of the Safety of Antistaphylococcal Penicillins Compared to Cefazolin

Recent studies and experience suggest that cefazolin might be equally as effective as antistaphylococcal penicillins for methicillin-susceptible Staphylococcus aureus (MSSA), with a better safety profile and lower cost. The objective of these meta-analyses was to compare the safeties of antistaphylococcal penicillins and cefazolin. The PubMed, Embase, and International Pharmaceutical Abstracts databases and websites for clinical trial registries through 23 June 2017 were searched. In addition, recent abstracts from infectious disease and pharmacy conferences were reviewed. We estimated Peto odds ratios (ORs) with 95% confidence intervals (CIs) using random-effects models. One analysis focused on hospitalized patients, and the other focused on outpatients. Eleven retrospective studies of hospitalized patients and three retrospective studies of outpatients were included. In hospitalized patients, lower rates of nephrotoxicity (Peto OR, 0.225; 95% CI, 0.127 to 0.513), acute interstitial nephritis (Peto OR, 0.189; 95% CI, 0.053 to 0.675), hepatotoxicity (Peto OR, 0.160; 95% CI, 0.066 to 0.387), and drug discontinuation due to adverse reactions (Peto OR, 0.192; 95% CI, 0.089 to 0.414) were found with cefazolin. In outpatients, lower rates of nephrotoxicity (Peto OR, 0.372; 95% CI, 0.192 to 0.722), hepatotoxicity (Peto OR, 0.313; 95% CI, 0.156 to 0.627), and hypersensitivity reactions (Peto OR, 0.372; 95% CI, 0.201 to 0.687) were observed with cefazolin. Compared to antistaphylococcal penicillins, cefazolin was associated with significant reductions in nephrotoxicity and hepatotoxicity in hospitalized patients and outpatients. Additionally, cefazolin was associated with lower likelihoods of discontinuation due to side effects in hospitalized patients and hypersensitivity reactions in outpatients. Cefazolin should be considered a first-line option for patients with MSSA infections for which efficacy is presumed to be similar to that of antistaphylococcal penicillin therapy.

Efficacy of Ceftaroline against Methicillin-Susceptible Staphylococcus aureus Exhibiting the Cefazolin High-Inoculum Effect in a Rat Model of Endocarditis

Certain Staphylococcus aureus strains exhibit an inoculum effect (InE) with cefazolin (CFZ) that has been associated with therapeutic failures in high-inoculum infections. We assessed the in vitro activities of ceftaroline (CPT), CFZ, and nafcillin (NAF) against 17 type A β-lactamase (βla)-producing, methicillin-susceptible S. aureus (MSSA) strains, including the previously reported TX0117, which exhibits the CFZ InE, and its βla-cured derivative, TX0117c. Additionally, we determined the pharmacokinetics of CPT in rats after single intramuscular doses of 20 and 40 mg/kg of body weight and evaluated the activities of CPT (40 mg/kg every 8 h [q8h]), CFZ, and NAF against TX0117 and TX0117c in a rat model of infective endocarditis. No InE was observed for CPT or NAF, whereas a marked InE was detected for CFZ (MIC, 8 to ≥128 μg/ml). CPT and NAF treatment against TX0117 resulted in mean bacterial counts of 2.3 and 2.1 log10 CFU/g in vegetations, respectively, compared to a mean of 5.9 log10 CFU/g in the CFZ-treated group (CPT and NAF versus CFZ, P = 0.001; CPT versus NAF, P = 0.9830). Both CFZ and CPT were efficacious against the βla-cured derivative, TX0117c, compared to time zero (t0) (P = <0.0001 and 0.0015, respectively). Our data reiterate the in vivo consequences of the CFZ InE and show that CPT is not affected by this phenomenon. CPT might be considered for high-inoculum infections caused by MSSA exhibiting the CFZ InE.

Implementation of a cefazolin-based stewardship pathway for methicillin-susceptible Staphylococcus aureus bloodstream infections paired with infectious diseases consultation

Methicillin-susceptible Staphylococcus aureus (MSSA) infections have been successfully treated both with cefazolin and antistaphylococcal penicillins; cefazolin appears effective in MSSA bloodstream infections (BSIs). Thus, our antimicrobial stewardship programme (ASP) implemented a clinical pathway supporting cefazolin use in MSSA-BSIs and restricting oxacillin use to infectious diseases (ID) consultation due to cefazolin's lower cost and more convenient dosing. This before and after quasi-experimental study was conducted to describe the impact on outcomes and process of care measures associated with implementing this pathway among patients with MSSA-BSI. Definitive treatment with cefazolin increased over the study period from 17.3% to 69.8% post-implementation. Clinical failure (5.8% vs. 2.3%; P = 0.62) and in-hospital mortality (3.8% vs. 0%; P = 0.50) were rare pre- and post-implementation. Median hospital length of stay among survivors was similar between pre- and post-implementation periods (P = 0.31). Duration of bacteraemia [median (IQR) 3 (2-4) days vs. 2 (2-3) days; P = 0.002] and rates of re-infection after culture clearance (9.6% vs. 0%; P = 0.06) were reduced post-implementation. Frequency of source control (P = 0.71) and time to source control (P = 0.52) were similar between study periods. Significant increases in ID consultations (33.3% [3/9] vs. 73.3% [22/30]; P = 0.047) and median (IQR) 24-h daily doses [2 (1-3) g vs. 6 (3-6) g; P < 0.01] were seen for patients treated with cefazolin post-implementation. ASPs may find implementation of a similar pathway to be an effective means of improving the care of patients infected with MSSA.

Comparable Effectiveness of First Week Treatment with Anti-Staphylococcal Penicillin versus Cephalosporin in Methicillin-Sensitive Staphylococcus aureus Bacteremia: A Propensity-Score Adjusted Retrospective Study

The objective was to compare the prognostic impact of first week treatment with anti-staphylococcal penicillin (ASP) versus cephalosporin in methicillin-sensitive Staphylococcus aureus bacteremia (MS-SAB). Altogether 580 patients were retrospectively followed and categorized according to first week treatment; 84% (488) received ASP (cloxacillin) and 16% (92) cephalosporin (cefuroxime or ceftriaxone). SAB management was optimized with formal bedside infectious disease specialist consultation in 88%, deep infection foci diagnosed in 77% and adjunctive rifampicin therapy given to 61% of patients. The total case fatality in 580 patients was 12% at 28 days and 18% at 90 days. When comparing effectiveness of first week ASP versus cephalosporin treatment there were no significant differences in 28-days (11% vs. 12%, OR; 1.05, 95% CI, 0.53-2.09) or 90-days (17% vs. 21% OR; 1.25, 95% CI, 0.72-2.19) outcome. In univariate analysis no prognostic impact of either first week ASP or cephalosporin treatment was observed for 28-days (OR; 0.96, 95% CI, 0.48-1.90 and OR; 1.05, 95% CI, 0.53-2.09) or 90-days (OR; 0.80, 95% CI, 0.46-1.39 and OR; 1.25, 95% CI, 0.72-2.19) outcome. Propensity-score adjusted Cox proportional regression analysis for first week treatment with cephalosporin demonstrated no significant prognostic impact at 28-days (HR 1.54, 95% CI 0.72-3.23) or 90-days (HR 1.56, 95% CI 0.88-2.86).

IN CONCLUSION

There is a comparable effectiveness with respect to 28- and 90-days outcome for first week treatment with ASP versus cephalosporin in MS-SAB. The results indicate that the difference in prognostic impact between first week ASP and cephalosporin may be non-significant in patient cohorts with SAB management optimized by infectious disease specialist consultation.

Variation of Circulating Inflammatory Mediators in Staphylococcus aureus and Escherichia coli Bloodstream Infection

Background

The aim of this study was to examine the behavior of circulating inflammatory mediators and to exclude gram-positive from gram-negative bloodstream infections. Results may be helpful in selection of optimal specific antibiotic therapies.

Material/Methods

Mice (25–27 g) were randomized to 3 groups infected with Staphylococcus aureus (S. aureus) ATCC 25923, Escherichia coli (E. coli) ATCC 25922, or phosphate-buffered saline (PBS). The white blood cell count (WBC) and the concentrations of serum C-reactive protein (CRP), procalcitonin (PCT), interleukin (IL)-1α, IL-1β, IL-6, IL-10, monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1α (MIP-1α) were detected in blood samples at different time intervals after intravenous tail injection.

Results

The results showed that compared to the control mice, infected animals exhibited significantly higher levels of all mediators after bacterial infection. Moreover, compared to the mice that received S. aureus, animals with E. coli infection showed significantly greater increases in serum IL-1α, IL-1β, IL-6, MCP-1, and MIP-1α levels.

Conclusions

These results suggest that the use of the analyzed serum markers at an early stage of bloodstream infection may give useful information for the clinician to distinguish gram-negative from gram-positive infections.