Outcome of Enterococcus faecalis infective endocarditis according to the length of antibiotic therapy: Preliminary data from a cohort of 78 patients

Differential in vitro susceptibility to ampicillin/ceftriaxone combination therapy among Enterococcus faecalis infective endocarditis clinical isolates

OBJECTIVES

To investigate the genomic diversity and β-lactam susceptibilities of Enterococcus faecalis collected from patients with infective endocarditis (IE).

METHODS

We collected 60 contemporary E. faecalis isolates from definite or probable IE cases identified between 2018 and 2021 at the University of Pittsburgh Medical Center. We used whole-genome sequencing to study bacterial genomic diversity and employed antibiotic checkerboard assays and a one-compartment pharmacokinetic-pharmacodynamic (PK/PD) model to investigate bacterial susceptibility to ampicillin and ceftriaxone both alone and in combination.

RESULTS

Genetically diverse E. faecalis were collected, however, isolates belonging to two STs, ST6 and ST179, were collected from 21/60 (35%) IE patients. All ST6 isolates encoded a previously described mutation upstream of penicillin-binding protein 4 (pbp4) that is associated with pbp4 overexpression. ST6 isolates had higher ceftriaxone MICs and higher fractional inhibitory concentration index values for ampicillin and ceftriaxone (AC) compared to other isolates, suggesting diminished in vitro AC synergy against this lineage. Introduction of the pbp4 upstream mutation found among ST6 isolates caused increased ceftriaxone resistance in a laboratory E. faecalis isolate. PK/PD testing showed that a representative ST6 isolate exhibited attenuated efficacy of AC combination therapy at humanized antibiotic exposures.

CONCLUSIONS

We find evidence for diminished in vitro AC activity among a subset of E. faecalis IE isolates with increased pbp4 expression. These findings suggest that alternate antibiotic combinations against diverse contemporary E. faecalis IE isolates should be evaluated.

State-of-the-Art Review: Persistent Enterococcal Bacteremia

Persistent enterococcal bacteremia is a commonly encountered and morbid syndrome without a strong evidence base for optimal management practices. Here we highlight reports on the epidemiology of enterococcal bacteremia to better describe and define persistent enterococcal bacteremia, discuss factors specific to Enterococcus species that may contribute to persistent infections, and describe a measured approach to diagnostic and therapeutic strategies for patients with these frequently complicated infections. The diagnosis of persistent enterococcal bacteremia is typically clinically evident in the setting of repeatedly positive blood culture results; instead, the challenge is to determine in an accurate, cost-effective, and minimally invasive manner whether any underlying nidus of infection (eg, endocarditis or undrained abscess) is present and contributing to the persistent bacteremia. Clinical outcomes for patients with persistent enterococcal bacteremia remain suboptimal. Beyond addressing host immune status if relevant and pursuing source control for all patients, management decisions primarily involve the selection of the proper antimicrobial agent(s). Options for antimicrobial therapy are often limited in the setting of intrinsic and acquired antimicrobial resistance among enterococcal clinical isolates. The synergistic benefit of combination antimicrobial therapy has been demonstrated for enterococcal endocarditis, but it is not clear at present whether a similar approach will provide any clinical benefit to some or all patients with persistent enterococcal bacteremia.

Recurrent bacteremia with Enterococcus faecalis, the clinical findings predicting endocarditis, and genomic characterization of the isolates: a retrospective cohort study

Multiple episodes of Enterococcus faecalis bacteremia (EfsB) may indicate a relapse and be due to an undiagnosed infective endocarditis (IE). The aims were to study the clinical presentation of patients with EfsB with focus on the risk of recurrent infection and IE, identify potential improvements of the management, and to investigate whether E. faecalis isolates from different episodes in the same patient were identical. In a retrospective study, a cohort of patients with monomicrobial (M) EfsB episodes was analyzed. Clinical data from medical records were collected. Furthermore, blood culture isolates from patients with multiple episodes were subjected to whole genome sequencing and multilocus sequence typing. In 666 episodes of MEfsB, 69 patients with IE and 43 with recurrent infections were found. Patients without IE, but with a following episode diagnosed as IE, were compared to those without a following episode. Variables significantly correlated with IE were long duration of symptoms, growth in all blood cultures, unknown origin of infection, heart murmur, and predisposition for IE. Transesophageal echocardiography, all negative, was done in 4 out of 11 episodes during the first episodes, later diagnosed with IE. In 28 of 31 patients with two or more EfsB episodes, isolates with identical sequence type were found. Episodes of EfsB in patients later diagnosed with IE showed features of IE already during the first episodes, were not adequately evaluated, are due to identical isolates, and most likely represent true relapses. Risk factor analysis should guide the use of echocardiography.

A retrospective study of Enterococcus faecalis infective endocarditis: comparison of clinical characteristics and outcomes associated with treatment

Introduction

A synergistic antibiotic combination of a penicillin and gentamicin (AG) or ceftriaxone (AC) is used in the management of Enterococcus faecalis infective endocarditis (EFIE). We compare the treatment outcomes between AG and AC, including low and high dose ceftriaxone (1 and 2 g 12 hourly).

Methods

A retrospective cohort study of patients treated for EFIE at single tertiary centre (2012–2019). Outcome measures examined were 90- and 180-day mortality, treatment associated adverse events and relapse of bacteraemia (within 1 year).

Results

39 patients were enrolled [61.6% given (AC) (n = 24), 24% received ACL (n = 10) and 34% received ACN (n = 14)], 38.4% received AG (n = 15). We noted a difference in the mortality outcomes at 90 and 180 days between those treated with AG and AC overall (6.7% and 33.3%, respectively) although this did not reach statistical significance (P = 0.114, P = 0.061). No significant difference was noted between these groups in incidence of relapsed bacteraemia with two cases noted in the AC cohort (8.3%, 2/24) and none observed (0/15) in the AG cohort (P = 0.662, P = 0.414). A greater number of adverse events was observed in the AG group (11/15, 73.3%) compared to the overall AC group (6/24, 25.0%) (P = 0.009), with no difference between the high and low dose ceftriaxone groups (P = 0.05).

Conclusion

Combination treatment of EFIE with AC is associated with a reduced number of adverse events in comparison to AG groups. Although increased mortality was observed in the AC group, this did not reach statistical significance, and reflects the greater comorbidities and reduced capacity for surgical source control in this cohort.

Ampicillin plus ceftriaxone therapy against Enterococcus faecalis endocarditis: A case report, guidelines considerations, and literature review

Enterococcus faecalis infective endocarditis (EFIE) continues to be a very serious disease, showing considerable morbidity and mortality rates which are influenced by the spread of multi-drug resistant strains occurred in the last decades. Although aminoglycosides were considered the treatment of choice of EIFE, in recent years several studies have investigated alternative therapeutic approaches, including combinations of beta-lactams, mainly because of the aminoglycoside-renowned nephrotoxicity and the widespread development of high-level aminoglycosides resistance (HLAR). In this scenario, we reported a case involving a prosthetic valve infective endocarditis caused by an aminoglycoside-resistant E. faecalis strain which was successfully treated with ampicillin plus ceftriaxone despite the presence of artificial heart valve and the patient’s severe clinical conditions.

Time to abandon ampicillin plus gentamicin in favour of ampicillin plus ceftriaxone in Enterococcus faecalis infective endocarditis? A meta-analysis of comparative trials

Background

Current guidelines recommend either ampicillin plus ceftriaxone (AC) or amoxicillin/ampicillin plus gentamicin (AG) with an equivalent class IB recommendation in Enterococcus faecalis endocarditis. However, previous observational studies suggest that AC might be favourable in terms of adverse events.

Objectives

To investigate whether AC is non-inferior to AG, and if it is associated with less adverse events.

Methods

In June 2021, a systematic literature search using the databases PubMed/MEDLINE, CDSR, CENTRAL, CCAs, EBM Reviews, Web of Science and LILACS was conducted by two independent reviewers. Studies were considered eligible if (P) patients included were ≥ 18 years of age and had IE with E. faecalis, (I) treatment with AC was compared to (C) treatment with AG and (O) outcomes on in-hospital mortality, nephrotoxicity and adverse events requiring drug withdrawal were reported. Odds ratios and 95% confidence intervals were calculated using random-effects models with the Mantel–Haenszel method, the Sidik–Jonkman estimator for τ² and the Hartung–Knapp adjustment.

Results

Treatment with AC was non-inferior to AG, as depicted by no significant differences in-hospital mortality, 3-month mortality, relapses or treatment failure. Furthermore, AC was associated with a lower prevalence of nephrotoxicity (OR 0.45 [0.26–0.77], p = 0.0182) and drug withdrawal due to adverse events (OR 0.11 [0.03–0.46], p = 0.0160) than AG.

Conclusions

Treatment with AC was non-inferior to treatment with AG, and it was associated with a reduced prevalence of nephrotoxicity and drug withdrawal due to adverse events. Thus, combination therapy with AC appears favourable over AG in patients with E. faecalis IE.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01971-3.

Ampicillin Plus Ceftriaxone Regimen against Enterococcus faecalis Endocarditis: A Literature Review

Enterococcus faecalis infective endocarditis (EFIE) continues to represent a potentially fatal infectious disease characterized by elevated morbidity and mortality. Despite advances in antimicrobial therapy, changing demographics and the reduced availability of useful antibiotics combined with the dissemination of multi-drug resistant strains, the mortality rate remained unchanged in the last decades. Nowadays, optimizing the antibiotic regimen is still of paramount importance. Historically, aminoglycosides were considered as a cornerstone for treatment even though their use is associated with a high risk of kidney failure. It is against this background that, in recent years, several studies have been carried in order to assess the validity of alternative therapeutic approaches, including combinations of beta-lactams, that, acting synergistically, have yielded useful results in different clinical settings. In this scenario, we searched and critically report clinical studies assessing the efficacy and safety of double beta-lactam therapy in treating EFIE.

Outpatient continuous-infusion benzylpenicillin combined with either gentamicin or ceftriaxone for enterococcal endocarditis

BACKGROUND

Treatment regimens requiring multiple daily dosing for enterococcal endocarditis are challenging to deliver in the outpatient setting. Continuous-infusion benzylpenicillin via a 24 h elastomeric infusor, combined with either once-daily gentamicin or ceftriaxone, requires only one nursing encounter daily and is commonly used in New Zealand.

OBJECTIVES

To assess the therapeutic success and adverse antibiotic effects of these regimens.

METHODS

A retrospective observational case series from multiple hospitals of patients aged 15 years or over with enterococcal endocarditis diagnosed between July 2013 and June 2019 who received at least 14 days of outpatient continuous-infusion benzylpenicillin combined with either gentamicin or ceftriaxone for synergy.

RESULTS

Forty-three episodes of enterococcal endocarditis in 41 patients met inclusion criteria. The primary synergy antibiotic was gentamicin in 20 episodes and ceftriaxone in 23 episodes. For the 41 initial treatment courses, 31 (76%) patients were cured, 3 (7%) patients developed relapsed endocarditis during or following antibiotic treatment and 7 (17%) patients continued with long-term suppressive oral amoxicillin following IV antibiotic treatment. There was no difference in the relapse rate between the two groups (P = 0.59). Seven (35%) adverse antibiotic effects were documented in the gentamicin group and none in the ceftriaxone group (P < 0.01). Two deaths (5%) occurred within the 6 month follow-up period.

CONCLUSIONS

Outpatient treatment of enterococcal endocarditis with continuous-infusion benzylpenicillin combined with either once-daily gentamicin or ceftriaxone following a period of inpatient treatment is usually effective. A significantly higher rate of adverse effects was seen with gentamicin, favouring ceftriaxone as the initial synergy antibiotic.

Enterococcus faecalis endocarditis: what's next?

Enterococcus faecalis infective endocarditis (EFIE) is a complex entity in rapid evolution. Although largely relevant findings from recent studies have advanced the knowledge on EFIE and led to some changes in clinical guidelines, there are still a number of gaps to be filled. Coordinated, international, multicenter efforts are needed to obtain quality data that rend the health systems and scientific community prepared enough to understand and handle this infection. In this Perspective, some of the most relevant aspects concerning the epidemiology, clinical presentation and outcomes, diagnostic approaches and antibiotic therapy of EFIE are addressed. Also, several potential future clinical developments in the field are discussed.

Clinical Factors Associated with Reinfection versus Relapse in Infective Endocarditis: Prospective Cohort Study

We aimed to identify clinical factors associated with recurrent infective endocarditis (IE) episodes. The clinical characteristics of 2816 consecutive patients with definite IE (January 2008–2018) were compared according to the development of a second episode of IE. A total of 2152 out of 2282 (94.3%) patients, who were discharged alive and followed-up for at least the first year, presented a single episode of IE, whereas 130 patients (5.7%) presented a recurrence; 70 cases (53.8%) were due to other microorganisms (reinfection), and 60 cases (46.2%) were due to the same microorganism causing the first episode. Thirty-eight patients (29.2%), whose recurrence was due to the same microorganism, were diagnosed during the first 6 months of follow-up and were considered relapses. Relapses were associated with nosocomial endocarditis (OR: 2.67 (95% CI: 1.37–5.29)), enterococci (OR: 3.01 (95% CI: 1.51–6.01)), persistent bacteremia (OR: 2.37 (95% CI: 1.05–5.36)), and surgical treatment (OR: 0.23 (0.1–0.53)). On the other hand, episodes of reinfection were more common in patients with chronic liver disease (OR: 3.1 (95% CI: 1.65–5.83)) and prosthetic endocarditis (OR: 1.71 (95% CI: 1.04–2.82)). The clinical factors associated with reinfection and relapse in patients with IE appear to be different. A better understanding of these factors would allow the development of more effective therapeutic strategies.

Enterococcus faecalis Endocarditis and Outpatient Treatment: A Systematic Review of Current Alternatives

The selection of the best alternative for Enterococcus faecalis infective endocarditis (IE) continuation treatment in the outpatient setting is still challenging. Three databases were searched, reporting antibiotic therapies against E. faecalis IE in or suitable for the outpatient setting. Articles the results of which were identified by species and treatment regimen were included. The quality of the studies was assessed accordingly with the study design. Data were extracted and synthesized narratively. In total, 18 studies were included. The treatment regimens reported were classified regarding the main antibiotic used as regimen, based on Aminoglycosides, dual β-lactam, teicoplanin, daptomycin or dalbavancin or oral therapy. The regimens based on aminoglycosides and dual β-lactam combinations are the treatment alternatives which gather more evidence regarding their efficacy. Dual β-lactam is the preferred option for high level aminoglycoside resistance strains, and for to its reduced nephrotoxicity, while its adaptation to the outpatient setting has been poorly documented. Less evidence supports the remaining alternatives, but many of them have been successfully adapted to outpatient care. Teicoplanin and dalbavancin as well as oral therapy seem promising. Our work provides an extensive examination of the potential alternatives to E. faecalis IE useful for outpatient care. However, the insufficient evidence hampers the attempt to give a general recommendation.

Four weeks versus six weeks of ampicillin plus ceftriaxone in Enterococcus faecalis native valve endocarditis: A prospective cohort study

Enterococcus faecalis infective endocarditis (EFIE) is a severe disease of increasing incidence. The objective was to analyze whether the outcome of patients with native valve EFIE (NVEFIE) treated with a short course of ampicillin plus ceftriaxone (4wAC) was similar to patients treated according to international guidelines (6wAC). Between January 2008 and June 2018, 1,978 consecutive patients with definite native valve IE were prospectively included in a national registry. Outcomes of patients with NVEFIE treated with 4wAC were compared to those of patients who received 6wAC. Three hundred and twenty-two patients (16.3%) had NVEFIE. One hundred and eighty-three (56.8%) received AC. Thirty-nine patients (21.3%) were treated with 4wAC for four weeks and 70 patients (38.3%) with 6wAC. There were no differences in age or comorbidity. Patients treated 6wAC presented a longer duration of symptoms before diagnosis (21 days, IQR 7-60 days vs. 7 days, IQR 1-22 days; p = 0.002). Six patients presented perivalvular abscess and all of these received 6wAC. Surgery was performed on 14 patients (35.9%) 4wAC and 34 patients (48.6%) 6wAC (p = 0.201). In-hospital mortality, one-year mortality and relapses among 4wAC and 6wAC patients were 10.3% vs. 11.4% (p = 0.851); 17.9% vs. 21.4% (p = 0.682) and 5.1% vs. 4.3% (p = 0.833), respectively. In conclusion, a four-week course of AC may be considered as an alternative regimen in NVEFIE, notably in patients with shorter duration of symptoms and those without perivalvular abscess. These results support the performance of a randomized clinical trial to evaluate the efficacy of this short regimen.

Successful treatment of relapsed enterococcal endocarditis with amoxicillin/clavulanate: A case report

Enterococcus is considered to be a common cause of endocarditis with unfavorable outcomes. We report a case of successful treatment of relapsed prosthetic valve Enterococcus faecalis endocarditis with oral amoxicillin/clavulanate. Enterococcal endocarditis is associated with a high relapse rate, even with the recommended treatment duration by the guidelines. Oral therapy is increasingly considered as part of the management of such serious infections.

In vitro and in vivo Synergistic Effects of Florfenicol and Thiamphenicol in Combination Against Swine Actinobacillus pleuropneumoniae and Pasteurella multocida

Potential synergism between florfenicol (FF) and thiamphenicol (TAP) was investigated for in vitro efficacy against Actinobacillus pleuropneumoniae and/or Pasteurella multocida as well as in vivo efficacy in swine. Among isolates of A. pleuropneumoniae (n = 58) and P. multocida (n = 79) from pigs in Taiwan that were tested, high percentages showed resistance to FF (52 and 53%, respectively) and TAP (57 and 53%, respectively). Checkerboard microdilution assay indicated that synergism [fractional inhibitory concentration index (FICI) ≤ 0.5] was detected in 17% of A. pleuropneumoniae (all serovar 1) and 24% of P. multocida isolates. After reconfirming the strains showing FICI ≤ 0.625 with time kill assay, the synergism increased to around 32% against both bacteria and the number could further increase to 40% against resistant A. pleuropneumoniae and 65% against susceptible P. multocida isolates. A challenge-treatment trial in pigs with P. multocida showed that the FF + TAP dosage at ratios correspondent to their MIC deduction was equally effective to the recommended dosages. Further on the combination, the resistant mutation frequency is very low when A. pleuropneumoniae is grown with FF + TAP and similar to the exposure to sub-inhibitory concentration of FF or TAP alone. The degree of minimum inhibitory concentration (MIC) reduction in FF could reach 75% (1/4 MIC) or more (up to 1/8 MIC for P. multocida, 1/16 for A. pleuropneumoniae) when combined with 1/4 MIC of TAP (or 1/8 for A. pleuropneumoniae). The synergism or FICI ≤ 0.625 of FF with oxytetracycline (47%), doxycycline (69%), and erythromycin (56%) was also evident, and worth further investigation for FF as a central modulator facilitating synergistic effects with these antimicrobials. Taken together, synergistic FF + TAP combination was effective against swine pulmonary isolates of A. pleuropneumoniae and P. multocida both in vitro and in vivo. Thus, this study may offer a potential alternative for the treatment of A. pleuropneumoniae and P. multocida infections and has the potential to greatly reduce drug residues and withdrawal time.

Comparison of Dual β-Lactam therapy to penicillin-aminoglycoside combination in treatment of Enterococcus faecalis infective endocarditis

BACKGROUND

Dual β-lactam therapy and a penicillin-aminoglycoside combination are first line regimens in the treatment of penicillin-susceptible Enterococcus faecalis infective endocarditis (EFIE). Our aim was to compare ampicillin plus ceftriaxone (A+C) to ampicillin plus gentamicin (A+G) in the treatment of EFIE.

METHODS

This was a retrospective cohort study of adults (≥18 years) patients diagnosed with EFIE at Mayo Clinic campuses in Rochester, Minnesota, and Phoenix, Arizona and treated with either A+C or A+G. Main outcome measurements were 1 year mortality, nephrotoxicity, and EFIE relapse rates.

RESULTS

Eighty-five cases of EFIE were included in this investigation. The majority (n=67, 79%) of patients received A+G while 18 (21%) patients received A+C as initial treatment. On admission, patients who received A+C had a higher Charlson Comorbidity Index (median [IQR], 4 [3, 4 vs. 2 [1, 4]; P=.008) and a higher baseline serum creatinine (median [IQR], 1.2 [0.9, 1.6] vs. 0.9 [0.8, 1.2] mg/dL, P=.020). The 1 year mortality rates were similar for both treatment groups, 17% vs. 17%, P=.982. Each group had 1 case of relapsing EFIE. Patients who received A+G had worse kidney function outcome demonstrated by a greater increase in serum creatinine at end of therapy (median [IQR] difference, +0.4 [0.2, 0.8] vs. -0.2 [-0.3, 0.1] mg/dL, P≤.001).

CONCLUSION

A+C appears to be a safe and efficacious regimen in the treatment of EFIE. Patients treated with A+C had lower rates of nephrotoxicity and no differences in relapse rate and 1-year mortality as compared to that of the A+G group.

Correction: Outcome of Enterococcus faecalis infective endocarditis according to the length of antibiotic therapy: Preliminary data from a cohort of 78 patients

[This corrects the article DOI: 10.1371/journal.pone.0192387.].