Model-Informed Precision Dosing Improves Outcomes in Patients Receiving Vancomycin for Gram-Positive Infections

Background

Consensus guidelines for dosing and monitoring of vancomycin recommend collection of 2 serum concentrations to estimate an area under the curve/minimum inhibitory concentration ratio (AUC/MIC). Use of Bayesian software for AUC estimation and model-informed precision dosing (MIPD) enables pre-steady state therapeutic drug monitoring using a single serum concentration; however, data supporting this approach are limited.

Methods

Adult patients with culture-proven gram-positive infections treated with vancomycin ≥72 hours receiving either trough-guided or AUC-guided therapy were included in this retrospective study. AUC-guided therapy was provided using MIPD and single-concentration monitoring. Treatment success, vancomycin-associated acute kidney injury (VA-AKI), and inpatient mortality were compared using a desirability of outcome ranking analysis. The most desirable outcome was survival with treatment success and no VA-AKI, and the least desirable outcome was death.

Results

The study population (N = 300) was comprised of an equal number of patients receiving AUC-guided or trough-guided therapy. More patients experienced the most desirable outcome in the AUC-guided group compared to the trough-guided group (58.7% vs 46.7%, P = .037). Rates of VA-AKI were lower (21.3% vs 32.0%, P = .037) and median hospital length of stay was shorter (10 days [interquartile range {IQR}, 8-20] vs 12 days [IQR, 8-25]; P = .025) among patients receiving AUC-guided therapy.

Conclusions

AUC-guided vancomycin therapy using MIPD and single-concentration monitoring improved outcomes in patients with culture-proven gram-positive infections. Safety was improved with reduced incidence of VA-AKI, and no concerns for reduced efficacy were observed. Moreover, MIPD allowed for earlier assessment of AUC target attainment and greater flexibility in the collection of serum vancomycin concentrations.

Outcomes of Daptomycin Plus Ceftaroline Versus Alternative Therapy for Persistent Methicillin-resistant Staphylococcus aureus (MRSA) Bacteraemia

OBJECTIVES

This study aimed to evaluate both efficacy and safety of combination therapy with daptomycin plus ceftaroline (DAP/CPT) versus alternative therapy in the treatment of persistent methicillin-resistant Staphylococcus aureus bacteraemia (MRSAB).

METHODS

This retrospective, single-centre study investigated adult patients who underwent a change in antibiotic therapy for persistent MRSAB. Daptomycin plus ceftaroline was compared with alternative therapy after initial treatment with vancomycin or DAP monotherapy was modified. The primary outcome was in-hospital mortality, and several secondary efficacy and safety outcomes were evaluated.

RESULTS

A total of 68 patients with persistent MRSAB had initial therapy switched to DAP/CPT (n = 43) or alternative therapy (n = 25). In-hospital mortality was similar with DAP/CPT versus alternative therapy (16.3% vs. 16%; P = 1.0). On average, the total duration of bacteraemia was numerically 1 day less in patients switched to DAP/CPT (11.4 days vs. 12.5 days; P = 0.5). Daptomycin plus ceftaroline was de-escalated in 81% of patients after receiving combination therapy for an average of 12.5 days. Secondary outcomes, including rates of adverse events and emergence of antimicrobial resistance, were similar between the two groups.

CONCLUSIONS

Switching to DAP/CPT after approximately 1 week of persistent MRSA bacteraemia may result in similar clinical outcomes when compared with alternative therapy. Rates of adverse events and emergence of antimicrobial resistance were low without a statistically significant difference observed between DAP/CPT and alternative therapy. These findings, as well as the impact of earlier switch or prolonged treatment with the combination, require further investigation.

1834. Evaluation of De-Escalation Options after Combination Daptomycin and Ceftaroline Therapy for Persistent MRSA Bacteremia

Background

Methicillin-resistant Staphylococcus aureus (MRSA) bacteremia carries high mortality with limited treatment options. Studies over the last decade support glycolipopeptide and beta-lactam combination therapy with daptomycin (DAP) and ceftaroline (CFT) combination gaining prominence. While data supports de-escalation to monotherapy after bacteremia clearance it does not guide the choice of agent. With barriers including accessibility, cost, and tolerability of these agents, data is needed to optimize treatment. This study aims to evaluate de-escalation options after combination DAP/CFT therapy for persistent MRSA bacteremia.

Methods

A single-center, retrospective review of cases of persistent MRSA bacteremia (defined as greater than 72 hours on appropriate therapy) requiring escalation to DAP/CFT between 2014 and 2021 was performed. Details of bacteremia, source of infection, and comorbidities were assessed, and outcomes including recurrence of infection, infection-associated mortality, and tolerability were compared using exact Chi-square testing and univariant analysis.

Results

Sixty-six cases were identified of which 7 were de-escalated to vancomycin (VAN), 48 to DAP, 4 to CFT, and 7 continued DAP/CFT combination. Demographics and details of bacteremia such as prior anti-MRSA therapy, duration prior to DAP/CFT therapy, and source identification were similar between groups. Differences included higher rates of hemodialysis patients in the VAN group, higher rates of immunocompromised hosts in the DAP group, higher average Pitt bacteremia score in the DAP/CFT group, and lower rates of source control in the VAN group. Recurrence of infection (29% VAN, 13% DAP, 25% CFT) and infection-related mortality (14% VAN, 8% DAP) were higher in the VAN group (p=0.0452). In the DAP group 23% required change in therapy during their course. Univariant analysis assessing for confounding from comorbidities and source control yielded no significant associations.

Conclusion

This study is limited by small, uneven sample sizes but the results identify a trend of increased recurrence rates and mortality with de-escalation to VAN but tolerability concerns with DAP. More study is needed to guide clinical care and this data provides framework for future research.

Disclosures

All Authors: No reported disclosures.

1988. Piperacillin-tazobactam plus Ceftriaxone for Enterococcus faecalis endocarditis: A Single Center Experience

Background

Enterococcus faecalis is a leading cause of Infective Endocarditis (IE). IE guidelines recommend combination of penicillin (PCN) or ampicillin (AMP) with ceftriaxone (CTX) in susceptible strains. OPAT allows for antibiotic continuation at home; however outpatient AMP is limited due to frequent dosing and instability. Piperacillin-tazobactam (PTZ) has similar but not identical activity against penicillin binding proteins (PBP) compared to AMP and PCN, suggesting that PTZ may be a substitute in OPAT. This study compares outcomes in those with E. faecalis IE discharged with either PTZ or PCN with CTX.

Results of primary outcomes including death at 90 days and readmission at 90 days for those discharged on either PTZ or PCN in combination with CTX for E. faecalis endocarditis

Results of non infectious complications and changes in antibiotic therapy in both groups post discharge

Methods

This single center retrospective study took place from 2016 - 2020. Adults > 18 years with AMP susceptible E. faecalis IE diagnosed using Duke’s criteria and blood or tissue cultures were included, with cultures confirming PCN susceptibility. Primary endpoint was failure of therapy at 90 days, defined as death due to any cause or infection relapse. Secondary outcomes were duration of antibiotics, change in regimen and non-infectious complications.

Results

Overall, 34 patients were identified, 17 in each group. Average age was 60–80 years, majority having a high Charleston comorbidity index. One did not have available AMP susceptibility but was PCN susceptible. 19 were managed surgically (65% PTZ group, 47% PCN group). Average total antibiotic course was 8.2 and 7.3 weeks in PTZ and PCN groups, with average OPAT course being 4.5 and 4.4 weeks. Primary endpoint was met in 18% patients in the PTZ group and 24% in the PCN group. Of the PCN group, 1 was admitted 4 months later due to an E. faecalis device infection, outside of primary endpoint. Nearly 80% completed antibiotic therapy with 29% in the PTZ group and 35% in the PCN group readmitted for non-infectious complications, including metabolic imbalances, stroke, volume overload and gastro-intestinal bleed. Hyperkalemia was seen in the PCN group with 3 patients requiring readmission. Seizures were not reported with combined PCN and ceftriaxone.

Conclusion

Similar outcomes were seen using either PTZ or PCN with CTX for treatment of enterococcal IE. Discharging patients on PCN is not always a feasible option. In these instances, PTZ could be considered as an alternative OPAT agent despite dissimilar mechanism of action compared to AMP and PCN.

Disclosures

All Authors: No reported disclosures.

186. Klebsiella aerogenes: Are there implications to taxonomic accuracy?

Background

With advances in genomics, microbiologists can accurately rename existing bacteria which may cause confusion among clinicians familiar with prior names. Limited investigation is available on the clinical impact of these name changes. University of Alabama at Birmingham Hospital microbiology updated Klebsiella aerogenes in the electronic medical record (EMR) to "Klebsiella (Enterobacter) aerogenes" to reflect change in nomenclature. Therapy selection differs between Klebsiella pneumoniae and Enterobacter spp. due to differences in Ambler Class C (AmpC) beta-lactamase production. Our Antimicrobial Stewardship Program previously implemented selective and cascaded susceptibility reporting for E. aerogenes to guide antibiotic selection which remained after nomenclature change. The goal of this study is to determine if the change led to inappropriate antibiotic use.

Methods

We reviewed blood culture data from May 2016-2020 which grew Enterobacter aerogenes or Klebsiella "Enterobacter" aerogenes. We excluded polymicrobial blood cultures, patients aged 18 and under, and patients who died within 48 hours of drawing blood cultures. Appropriate therapy was defined as an antibiotic with reported susceptibility with consideration of AmpC induction for a duration appropriate to clinical syndrome with minimum of 7 days. We recorded patient demographics, nature of therapy, and clinical outcomes. We performed comparative analysis with descriptive statistics to compare the two groups.

Results

There were 38 patients with K. aerogenes bacteremia, 21 patients prior to name change and 17 afterwards. None were ESBL. Cefepime was most often used directed inpatient therapy while oral ciprofloxacin was the most common outpatient regimen with no use of ceftriaxone. Prior to name change, there was one case (4.76%) that did not receive targeted AmpC therapy while there were two afterwards (11.8%), one of which decided by the ID consult team. Table 1

Demographics (Data presented as No. (%)) Table 2

Microbiology and Outcomes (Data presented as No. (%)) Table 3

Antimicrobial Selection. One patient that received 72 hours of appropriate therapy but died prior to completion of therapy. This was labeled labelled as appropriate therapy.

Conclusion

Care must be taken when taxonomic changes of clinically relevant bacteria may potentially affect optimization of antibiotics. As the ID consultants, we must be aware of these name changes and provide up to date recommendations. Cascade reporting and documentation in the EMR may be helpful to reduce morbidity related to changes in nomenclature.

Disclosures

Sixto M. Leal, Jr., MD, PhD, GenMark Dx: Grant/Research Support|GenMark Dx: Honoraria.

Current Evidence in Delivery and Therapeutic Uses of Fecal Microbiota Transplantation in Human Diseases-Clostridium difficile Disease and Beyond

The use of fecal microbiota transplantation (FMT) was first described in China in the 4th century by Ge Hong when "yellow soup," a fecal slurry, was administered for the treatment of severe food poisoning and diarrhea, a practice that continued for centuries. Bedouin groups also consumed stools of their camels as a remedy for dysentery. FMT was also applied in veterinary medicine in Europe in the 16th century. Additional therapeutic use of human excretions was described in Europe in the 18th and 19th century and in World War II, when gut bacteria were administered to German soldiers suffering from dysentery in the North African campaign. More scientifically, Eismann, in 1958, utilized fecal transplantation via enema in 4 patients for the treatment of severe pseudomembranous colitis with success. Following this report a number of isolated cases were published describing the use of FMT by different delivery routes for the treatment of a variety of illnesses.

Loss of Vancomycin-Resistant Enterococcus Fecal Dominance in an Organ Transplant Patient With Clostridium difficile Colitis After Fecal Microbiota Transplant

We report the use of fecal microbiota transplantation in a single heart-kidney transplant recipient with recurrent Clostridium difficile, vancomycin-resistant Enterococcus (VRE) fecal dominance, and recurrent VRE infections. Fecal microbiota transplantation resulted in the reconstruction of a diverse microbiota with (1) reduced relative abundance of C difficile and VRE and (2) positive clinical outcome.

The management of urinary fistulas and strictures with percutaneous ureteral stent catheters

A method is described for percutaneous anterograde introduction of a ureteral stent catheter. The experience and treatment of 5 patients are reported: 2 ureterovaginal fistulas, 2 ureterocutaneous fistulas and 1 ureteral stricture. The capability of the technique to place a stent catheter in the presence of an almost complete separation of the ureter or through ureteral segments deformed by extensive cicatricial changes is emphasized. The method is advocated as a most effective alternative to supravesical drainage in patients with ureteral fistulas and impaired healing potential of ureters devitalized by surgical stripping and/or radiation therapy.