Once-daily aminoglycoside in the treatment of Enterococcus faecalis endocarditis: case report and review

Combatting resistant enterococcal infections: a pharmacotherapy review

INTRODUCTION

The role of enterococci in infectious diseases has evolved from a gut and urinary commensal to a major pathogen of concern. Few options exist for resistant enterococci, and appropriate use of the available agents is crucial.

AREAS COVERED

Herein, the authors discuss antibiotics with clinically useful activity against Enterococcus faecalis and E. faecium. The article specifically discusses: antibiotics active against enterococci and their mechanism of resistance, pharmacokinetic and pharmacodynamic principles, in vitro combinations, and clinical studies which focus on urinary tract, intra-abdominal, central nervous system, and bloodstream infections due to enterococci.

EXPERT OPINION

Aminopenicillins are preferred over all other agents when enterococci are susceptible and patients can tolerate them. Daptomycin and linezolid have demonstrated clinical efficacy against vancomycin-resistant enterococci (VRE). Synergistic combinations are often warranted in complex infections of high inoculum and biofilms while monotherapies are generally appropriate for uncomplicated infections. Although active against resistant enterococci, the pharmacokinetics, efficacy and safety of tigecycline and quinupristin/dalfopristin can problematical for severe infections. For cystitis, amoxicillin, nitrofurantoin, or fosfomycin are ideal. Recently, approved agents such as tedizolid and oritavancin have good in vitro activity against VRE but clinical studies against other resistant enterococci are lacking.

Gentamicin-mediated ototoxicity and nephrotoxicity: A clinical trial study

Background:

Aminoglycosides and mainly gentamicin are the most important antimicrobial agents. Two different methods of administration exist: Single and multiple doses. There has always been a controversy about the less harmful administration method, to minimize adverse effects of gentamicin – deafness and renal insufficiency. In this study, it was aimed to compare two different methods of administration to figure out the least harmful treatment method.

Materials and Methods:

In a clinical study, eighty patients aged 12–55 years who were admitted with sepsis syndrome were included in the study; they were divided into two groups: The first group received single-dose treatment (5 mg/kg) whereas the second group was treated with multiple doses (1.7 mg/kg three times a day) of gentamicin.

Results:

The results show that blood urea nitrogen (BUN) and creatinine (CR) levels were decreased in the first group. Both blood urea nitrogen and creatinine and also mean glomerular filtration rate was increased in the same group. In the second group, mean BUN and CR levels were increased while the GFR was decreased in the same group. There was also a gradual increase in GFR in the first group. GFR <80 was decreased from 20% to 5.1% in the first group while increased from 5% to 27.5% in the second group. Results of audiometric studies show 6.1% hearing problem in the first group and 12.8% in the second one.

Conclusions:

Results of the present study showed that nephrotoxicity and ototoxicity are minimized in single-dose administration compared to multiples doses.

Drug-induced acute kidney injury

PURPOSE OF REVIEW

The purpose of this review is to describe the most prevalent mechanisms of drug-induced acute kidney injury, to define the risk factors for nephrotoxicity, and to analyze the available evidence for preventive measures.

RECENT FINDINGS

Drug toxicity remains an important cause of acute kidney injury that, in many circumstances, can be prevented or at least minimized by vigilance and early intervention. Recent studies have resulted in increased insight into the subcellular mechanisms of drug nephrotoxicity. Further improvement is to be expected from the identification of early markers of nephrotoxicity and an increasing involvement of a clinical pharmacist.

SUMMARY

The main mechanisms of nephrotoxicity are vasoconstriction, altered intraglomerular hemodynamics, tubular cell toxicity, interstitial nephritis, crystal deposition, thrombotic microangiopathy, and osmotic nephrosis. Before prescribing a potentially nephrotoxic drug, the risk-to-benefit ratio and the availability of alternative drugs should be considered. Modifiable risk factors should be corrected. The correct drug dosage should be prescribed. Patients should be pre-hydrated and the glomerular filtration rate should be frequently monitored during the administration of a potentially nephrotoxic drug. Studies are needed to further elucidate the mechanisms of nephrotoxicity to design more-rational prevention and treatment strategies. Computer-based prescriber-order entry and an appropriately trained intensive care unit pharmacist are particularly helpful to minimize medication errors and adverse drug events.

Simulation of human gentamicin pharmacokinetics in an experimental Enterococcus faecalis endocarditis model

Significant differences between animal and human pharmacokinetics may be responsible for the conflicting results of experimental studies. This study determined the impact of human pharmacokinetic simulation (HPS) on gentamicin activity in an Enterococcus faecalis endocarditis model. The decrease in bacterial counts was greater with HPS than with a dose-equivalent regimen without HPS.

Special issues in the management of infective endocarditis caused by gram-positive cocci

Gram-positive cocci, mainly streptococci and staphylococci, continue to cause the majority of cases of infective endocarditis. Among the streptococci causing IE, the long-standing predominance of oral or viridans-group streptococci has progressively faded, while the number of cases caused by "enteric streptococci" (Streptococcus bovis and enterococci) has increased. While most oral streptococci and S. bovis strains remain fully sensitive to penicillin, nutritionally variant streptococci--now renamed Abiotrophia--and enterococci can exhibit resistance to penicillin and/or glycopeptides that makes endocarditis more difficult to treat. Among the staphylococci causing endocarditis, the increasing proportion of coagulase-negative and methicillin-resistant strains observed in recent years has changed the approach to choice of antibiotic therapy. The purpose of this paper is to focus on some new aspects of the management of antibiotic therapy of IE due to streptococci and staphylococci, including recent developments such as once-daily aminoglycoside administration in IE, outpatient antibiotic therapy, and the evaluation of new antibiotics.

Different aminoglycoside-resistant phenotypes in a rabbit Staphylococcus aureus endocarditis infection model

The impact of different types of enzymatic resistance on the in vivo antibacterial activity of aminoglycosides (amikacin, gentamicin, and netilmicin) was studied in the rabbit endocarditis model with four strains of Staphylococcus aureus. Animals were treated in a manner simulating the administration of a single daily human dose. Amikacin had no effect on the three kanamycin-resistant strains despite apparent susceptibility in the disk diffusion test. Gentamicin appears to be the preferable aminoglycoside for treatment of staphylococcal infections.

Extended interval aminoglycoside dosing: from concept to clinic

Extended-interval aminoglycoside dosing (EIAD), while a relatively recent concept in mainstream clinical practice, actually has its roots in the mid 1970s. Early trial and error approaches of manipulating the dosage regimen to avoid toxicity and improve efficacy have helped to characterize the pharmacodynamic properties of these drugs. The increasing successful use of EIAD and improved understanding of pharmacodynamics has helped this dosing regimen gain acceptance into routine clinical practice. A 1998 United States survey demonstrated that approximately 75% of hospitals have adopted EIAD into routine patient care. However, controversy still exists regarding some aspects of infrequent aminoglycoside administration, such as length of the drug-free interval and patient exclusion criteria. After more than 50 years of experience with the aminoglycosides we continue to learn how to most appropriately use these drugs.

Aminoglycoside nephrotoxicity: do time and frequency of administration matter?

Aminoglycosides remains the mainstay in the treatment of gram-negative infections despite their potential oto-and nephrotoxicity although alternatives with equal or better efficacy are available. Several approaches were investigated to decrease aminoglycosides nephrotoxicity. Among them, only the once-daily dosing of aminoglycosides has been brought to the clinic and physicians are now increasingly adopting this approach to reduce the toxicity of these agents. The incidence of aminoglycoside nephrotoxicity can be further reduced in view of the recent data on the circadian variations of their nephrotoxicity. In fact, it has been clearly demonstrated in both experimental animals and humans that the toxicity is maximal when the drug is injected during the rest period compared with the activity period. Thus, injecting aminoglycosides once-daily at the time of the lowest toxicity is actually the most interesting and clinically applicable approach to reduce aminoglycosides toxicity.

In vitro pharmacodynamic analysis of single daily dosing versus conventional dosing of gentamicin administered with penicillin against Enterococcus faecalis

STUDY OBJECTIVE

To compare the effectiveness of single daily dosing (SDD) versus conventional dosing of gentamicin when administered with penicillin to treat enterococcal infections.

DESIGN

In vitro pharmacodynamic model.

SETTING

Hospital laboratory.

MEASUREMENTS AND MAIN RESULTS

A 24-hour in vitro pharmacodynamic model was employed to simulate SDD and 3 times/day dosing of gentamicin, in conjunction with continuously infused penicillin, against Enterococcus faecalis. Duplicate 24-hour kill curves were generated with varying concentrations of penicillin and gentamicin alone and in combination. No difference in the rate of kill was seen between any combination of penicillin and gentamicin. Regrowth occurred only with drug combinations in which penicillin was administered continuously at the minimum inhibitory concentration. Variations in the gentamicin dosing regimen did not affect regrowth.

CONCLUSION

In the treatment of enterococcal infections, an SDD regimen for gentamicin shows no efficacy benefit compared with conventional dosing.