Evaluation of teicoplanin for treatment of endocarditis caused by gram-positive cocci in 20 patients

Clinical practice guidelines for therapeutic drug monitoring of teicoplanin: a consensus review by the Japanese Society of Chemotherapy and the Japanese Society of Therapeutic Drug Monitoring

Background

Owing to its low risk of adverse effects, teicoplanin has been extensively used in patients with infections caused by MRSA. To promote the better management of patients receiving teicoplanin, we have updated the guidelines for therapeutic drug monitoring (TDM).

Methods

The guidelines were developed by a committee following the methodology handbook published by the Japanese Medical Information Distribution Service. Nine clinical questions were selected. The committee conducted a systematic review and meta-analysis to establish evidence-based recommendations for the target trough concentration (C_min). An initial electronic database search returned 515 articles, and 97 articles qualified for a full review. Four and five studies were included for the efficacy evaluation of cut-off C_min values of 15 and 20 mg/L, respectively.

Results

Compared with C_min < 15 mg/L, a target C_min value of 15–30 mg/L resulted in increased clinical efficacy in patients with non-complicated MRSA infections (OR = 2.68; 95% CI = 1.14–6.32) without an increase in adverse effects. Although there was insufficient evidence, target C_min values of 20–40 mg/L were suggested in patients with complicated or serious MRSA infections. A 3 day loading regimen followed by maintenance treatment according to renal function was recommended to achieve the target trough concentrations. Because of the prolonged half-life of teicoplanin, measurement of the C_min value on Day 4 before reaching steady state was recommended.

Conclusions

The new guideline recommendations indicate the target C_min value for TDM and the dosage regimen to achieve this concentration and suggest practices for specific subpopulations.

The Role of the Coagulase-negative Staphylococci (CoNS) in Infective Endocarditis; A Narrative Review from 2000 to 2020

Coagulase-negative staphylococci (CoNS) are part of the microbiota of human skin and rarely linked with soft tissue infections. In recent years, CoNS species considered as one of the major nosocomial pathogens and can cause several infections such as catheter-acquired sepsis, skin infection, urinary tract infection, endophthalmitis, central nervous system shunt infection, surgical site infections, and foreign body infection. These microorganisms have a significant impact on human life and health and, as typical opportunists, cause peritonitis in individuals undergoing peritoneal dialysis. Moreover, it is revealed that these potential pathogens are mainly related to the use of indwelling or implanted in a foreign body and cause infective endocarditis (both native valve endocarditis and prosthetic valve endocarditis) in patients. In general, approximately eight percent of all cases of native valve endocarditis is associated with CoNS species, and these organisms cause death in 25% of all native valve endocarditis cases. Moreover, it is revealed that methicillin-resistant CoNS species cause 60 % of all prosthetic valve endocarditis cases. In this review, we describe the role of the CoNS species in infective endocarditis, and we explicated the reported cases of CoNS infective endocarditis in the literature from 2000 to 2020 to determine the role of CoNS in the process of infective endocarditis.

Efficacy of teicoplanin monotherapy following initial standard therapy in Enterococcus faecalis infective endocarditis: a retrospective cohort study

PURPOSE

Teicoplanin is often used in Enterococcus faecalis infective endocarditis as a relay in case of penicillin side effects, or in outpatients. We assessed the efficacy of teicoplanin used as continuation therapy after initial standard treatment of E. faecalis endocarditis.

METHODS

All adult patients consecutively diagnosed between 1997 and 2016 for E. faecalis endocarditis were retrospectively reviewed. Patients who received standard therapy (ST) were compared to those switched to teicoplanin to complete the treatment (teicoplanin therapy, TT).

RESULTS

Seventy-one patients were enrolled: 34 in the ST group and 37 in the TT group. Amoxicillin was replaced by teicoplanin after a median duration of 18 days (IQ_25 - 75 12-21). Teicoplanin (5.8 ± 2.3 mg/kg) was administered for a median duration of 29 days (IQ_25 - 75 25-34). Gentamicin therapy was similar. Overall duration of antimicrobial therapy was 42 days (IQ_25 - 75 35-43) in the ST group, and 46 days (IQ_25 - 75 43-49) in the TT group (p = 0.001). Global and endocarditis-related mortality rates were 22/34 (65%) and 13/34 (38%) in the ST group, and 14/37 (38%) and 3/37 (8%) in the TT group (p ≤ 0.05). Relapses occurred in 2/26 patients who survived the treatment phase in the ST group (8%) and in 3/37 in the TT group (8%, p = 0.68). All relapses in the TT group occurred in patients presenting prosthetic valve endocarditis. Finally, 20 patients were cured in the ST group (59%), and 33 patients in the TT group (89%, p = 0.003).

CONCLUSIONS

In E. faecalis endocarditis, the switch to teicoplanin in selected patients following an initial phase of standard treatment represents an alternative, particularly for outpatient therapy. Caution should be exercised in cases of prosthetic valve endocarditis.

Treatment of Infection and Colonization Caused by Methicillin-Resistant Staphylococcus aureus

The mechanism of methicillin resistance confers resistance to all available B-lactam antibiotics; consequently, B-lactam antibiotics have no role in therapy of methicillin-resistant Staphylococcus aureus (MRSA) infections. Vancomycin remains the drug of choice. Teicoplanin and daptomycin are two investigational antibiotics related to vancomycin in structure and in spectrum of activity. In clinical trials employing relatively low doses, neither was as effective as vancomycin. Trials at higher doses are on-going. Quinolones, ciprofloxacin in particular, have been used successfully to treat infections caused by MRSA; however, the usefulness of quinolones may be limited by the tendency of resistance to emerge during therapy. Quinolones probably should be used only in combination with another active agent, such as rifampin, when treating serious infections caused by MRSA. Other agents may be active in vitro against MRSA, but clinical data showing their effectiveness are lacking. Rifampin combination regimens appear most effectively to eradicate colonization with MRSA.

The use and therapeutic drug monitoring of teicoplanin in the UK

Teicoplanin dosage recommendations for specific infections have been modified in recent years. However, there was no significant increase in the proportion of pre-dose concentrations > 20 mg/L between 1994 and 1998 in samples sent for teicoplanin assay at the Regional Antimicrobial Reference Laboratory, Bristol, UK. A questionnaire on the use of teicoplanin and therapeutic drug monitoring (TDM) was sent to all UK National External Quality Assurance Scheme antibiotic assay users. Teicoplanin was widely used in the UK, although vancomycin was more popular as a choice of glycopeptide. Fewer than 25% recommended teicoplanin TDM during routine use, the main reasons being perceived lack of toxicity and lack of evidence for the use of teicoplanin TDM. Pre-dose concentrations < 20 mg/L were considered appropriate for treatment of bacteraemia caused by methicillin-resistant Staphylococcus aureus by 53% of those responding. Data sheet advice was relied upon more than TDM as an indication of therapeutic dosing. Microbiologists who mainly used vancomycin tended to perform more TDM and seek higher serum concentrations when using teicoplanin than those who preferentially used teicoplanin.

Limitations of presently available glycopeptides in the treatment of Gram-positive infection

The glycopeptide antibacterial drugs vancomycin and teicoplanin are widely used in hospitals for therapy of severe or multiresistant Gram-positive infections, notably staphylococcal, enterococcal and rarely pneumococcal. Vancomycin has also been used in the management of Clostridium difficile enteropathy. The incidence and potential for resistance differ between agents. The in vitro activity, pharmacokinetics and clinical use of glycopeptide, as well as epidemiology of glycopeptide resistance are discussed. There are limited comparative studies indicating the need for further investigation. Therapeutic drug monitoring has been widely used for vancomycin and less commonly for teicoplanin, but remains controversial. Advances in our understanding of their pharmacodynamics and clinical studies are helping clarify the situation. This paper reviews the current literature and highlights limitations of glycopeptides in treating Gram-positive infection.

Efficacy of teicoplanin-gentamicin given once a day on the basis of pharmacokinetics in humans for treatment of enterococcal experimental endocarditis

With the aim of investigating home therapy for enterococcal endocarditis, we compared the efficacy of teicoplanin combined with gentamicin given once a day or in three daily doses (t.i.d.) with the standard treatment, ampicillin plus gentamicin administered t.i.d., for treating experimental enterococcal endocarditis. The antibiotics were administered by using "human-like pharmacokinetics" (H-L), i.e, pharmacokinetics like those in humans, that simulated the profiles of these drugs in human serum. Animals with catheter-induced endocarditis were infected intravenously with 10(8) CFU of Enterococcus faecalis EF91 (MICs and MBCs of ampicillin, gentamicin, and teicoplanin, 0.5 and 32, 16 and 32, and 0.5 and 1 microg/ml, respectively) and were treated for 3 days with ampicillin H-L at 2 g every 4 h plus gentamicin H-L at 1 mg/kg every 8 h, or teicoplanin H-L at 10 mg/kg every 24 h, alone or combined with gentamicin, administered at dose of H-L at 1 mg/kg every 8 h or H-L at 4.5 mg/kg every 24 h. The results of therapy for experimental endocarditis due to EF91 showed that teicoplanin alone was as effective as ampicillin alone in reducing the bacterial load (P > 0.05). The combination of ampicillin or teicoplanin with gentamicin was more effective than the administration of both drugs alone in reducing the log(10)CFU/gram of aortic vegetation (P < 0.01 and P < 0.05, respectively). Teicoplanin plus gentamicin H-L at 4.5 mg/kg, both administered every 24 h, showed an efficacy equal to the "gold standard," ampicillin plus gentamicin H-L at 1 mg/kg t.i.d. (P > 0.05). Increasing the interval of administration of gentamicin to a single daily dose combined with teicoplanin resulted in a reduction of bacteria in the vegetations equivalent to that achieved with the recommended regimen of ampicillin plus thrice-daily gentamicin in the treatment of experimental endocarditis due to E. faecalis. Teicoplanin plus gentamicin, both administered once a day, may be useful home therapy for selected cases of enterococcal endocarditis.

The role of glycopeptide antibiotics in the treatment of infective endocarditis

There are several sets of guidelines for the treatment of infective endocarditis, reflecting the need for differing treatment in various countries and times. This review considers the need for differing treatment modalities and in particular the utility of the glycopeptide antibiotics vancomycin and teicoplanin. Specific recommendations are offered as to when to consider the use of glycopeptides, appropriate dosage, length of treatment course and whether to use monotherapy or combined therapy. Used judiciously, the glycopeptides give results as good as can be achieved with other antimicrobial agents without exceptional toxicity. The potential of teicoplanin for use in the outpatient treatment of infective endocarditis is considered.

Pharmacodynamics, pharmacokinetics, and therapeutic drug monitoring of glycopeptides

The glycopeptide antibacterial drugs, vancomycin and teicoplanin, are widely used in hospitals for therapy of severe or multiresistant infection that has a positive results on Gram's stain test. Although vancomycin resistance is common in some hospital-acquired Enterococcus sp and resistance to teicoplanin occurs among Staphylococci sp glycopeptides remain the cornerstone of therapy for infection due to methicillin-resistant Staphylococcus aureus (MRSA), coagulase-negative Staphylococcus organisms, and infection related to implanted devices. Therapeutic drug monitoring (TDM) of these agents remains controversial, but advances in our understanding of their pharmacodynamics and further clinical studies are helping clarify the situation. In the future, a more rational approach to monitoring will probably result in less intensive monitoring of vancomycin but more intensive monitoring of teicoplanin.

Infective endocarditis and glycopeptides

BACKGROUND

Despite the number of antibacterial agents currently available, endocarditis remains a difficult disease to treat and the mortality rate has not fallen in recent years. The glycopeptides have good activity against the Gram-positive bacteria commonly implicated in endocarditis (staphylococci, both coagulase-positive and negative; enterococci and streptococci).

OBJECTIVES

To assess the impact of the glycopeptides vancomycin and teicoplanin on the therapy of infectious endocarditis caused by Gram-positive bacteria.

METHODS

A retrospective review of all major published or recently conducted studies using vancomycin or teicoplanin to treat endocarditis.

RESULTS

Cure rates obtained with vancomycin and teicoplanin are similar, but there are no controlled studies to investigate this. Vancomycin nephrotoxicity limits its use in endocarditis, in particular when used in combination with an aminoglycoside. By contrast, teicoplanin shows little nephrotoxic potential, even in patients with some degree of renal impairment or when given in combination with an aminoglycoside. Teicoplanin should be used at doses of 6 mg/kg/day or higher to achieve satisfactory cure rates.

CONCLUSIONS

Clinical data on the use of glycopeptides in endocarditis suffer from a lack of controlled trials. Although teicoplanin appears to offer some advantages over vancomycin in the therapy of endocarditis, there is an urgent need for randomized, clinical trials before definitive conclusions can be drawn.

Comparative safety of teicoplanin and vancomycin

Teicoplanin have different safety profiles which can affect choice. Nephrotoxicity is significantly less likely to occur during treatment with teicoplanin than vancomycin when an aminoglycoside is being given concurrently. 'Red man' syndrome is a troublesome effect of vancomycin infusion which is extremely uncommon with teicoplanin use. Rash and fever can be dose-related phenomena but patients reacting to one glycopeptide may not react to both. Although thrombocytopenia is more frequent with teicoplanin, it is reversible and seldom seen at standard doses.

Anti-gram-positive agents. What we have and what we would like

The usefulness of many anti-Gram-positive antibiotics is being compromised by the spread of antibiotic resistance in bacteria. The most reliable agents for serious infections are the glycopeptide agents vancomycin and teicoplanin. The appropriate maintenance dosage for teicoplanin in serious infections is 6 mg/kg/day, i.e. usually 400 mg/day. There are 3 exceptions for which the daily maintenance dosage should be 12 mg/kg/day and these are intravenous drug abusers, septic arthritis (but not osteomyelitis), and Staphylococcus aureus endocarditis treated with teicoplanin monotherapy. When teicoplanin is given at these doses, it achieves clinical and bacteriological results that are equivalent to those obtained with vancomycin, irrespective of pathogen or type of infection. The toxicity profile favours teicoplanin over vancomycin, especially when other, potentially toxic, drugs are coadministered. Teicoplanin also has an advantage in terms of ease and convenience of administration, which, together with its lack of need for routine blood level monitoring, facilitates its use outside hospital. New agents hold some promise for the future; however, oral agents, if developed, could present the risk of being overused, which might compromise their long term utility.

Pharmacodynamics of vancomycin alone and in combination with gentamicin at various dosing intervals against methicillin-resistant Staphylococcus aureus-infected fibrin-platelet clots in an in vitro infection model

We compared the pharmacodynamic activities of vancomycin with or without gentamicin in an in vitro infection model with methicilin-resistant Staphylococcus aureus-infected fibrin-platelet clots. Infected fibrin-platelet clots (FPCs) were prepared with human cryoprecipitate, human platelets, thrombin, and the organism (approximately 10[9] CFU of MRSA-494/g) and were suspended with monofilament line in an infection model capable of simulating human pharmacokinetics. Antibiotics were bolused to simulate vancomycin regimens of 2 g every 24 h (q24h), 1 g q12h, 500 mg q6h, and continuous infusion (steady-state concentration of 20 microg/ml) and gentamicin regimens of 1.5 mg/kg of body weight q12h and 5 mg/kg once daily (q.d.). Model experiments were performed in duplicate over 72 h. FPCs were removed from the models in quadruplicate at 0, 8, 24, 32, 48, 72 h, weighed, homogenized, diluted, and plated to determine colony counts. The inoculum density at 72 h was used to compare bactericidal activities between the regimens. All regimens containing vancomycin significantly decreased the bacterial inoculum compared to the growth control (P < 0.001). Vancomycin monotherapy regimens were similar in bacterial kill regardless of dosing frequency. The addition of gentamicin (either q12h or q.d.) significantly improved the bactericidal activity of the vancomycin q6h, q12h, and q24h regimens (P < 0.001). The greatest reduction in bacterial density at 72 h (P < 0.001) and the most rapid rate of kill (time to 99.9% killing) were achieved with the regimen consisting of 2 g of vancomycin q24h plus gentamicin (q.d. or q12h).

A closer look at vancomycin, teicoplanin, and antimicrobial resistance

The worldwide increase in the incidence of resistant Gram-positive infections has renewed interest in the glycopeptide class of antimicrobial agents. Two glycopeptides are available in many parts of the world--vancomycin and teicoplanin. These two agents appear to differ in several respects, including: potential for selecting microbial resistance, dosing convenience, safety, and efficacy in severe infection. Teicoplanin appears to have lower toxicity and greater convenience; however, its widespread acceptance has been plagued by concerns over antimicrobial resistance, efficacy, and appropriate dosing. A review of available studies suggests that teicoplanin, when dosed at 6 mg/kg/day, is better tolerated than vancomycin 15 mg/kg/q12h; however, at these doses, it appears to be somewhat less effective than vancomycin in serious Staphylococcus aureus infection, such as endocarditis. Although higher doses of teicoplanin, 12 mg/kg/day to 30 mg/kg/day, have been associated with efficacy comparable to that of vancomycin in serious S. aureus infections, such doses may eliminate some of the safety advantages conferred by lower teicoplanin doses. Teicoplanin has been associated with resistance among coagulase-negative staphylococci and the selection of resistance in S. aureus. There is some evidence that widespread use of teicoplanin might accelerate the development of S. aureus resistance to both teicoplanin and vancomycin. The selection of an appropriate glycopeptide in an individual patient should be based not only on convenience, but also on a determination of optimal efficacy, safety at an efficacious dose, and the potential for resistance.

Population pharmacokinetic study of teicoplanin in severely neutropenic patients

The teicoplanin pharmacokinetics (PK) of 30 febrile and severely neutropenic patients (polymorphonuclear count, < 500/mm3) with hematologic malignancies were compared with those determined for five healthy volunteers (HV). Neutropenic patients were given piperacillin combined with amikacin, and teicoplanin was added to the regimen the day fever developed in patients suspected of having a staphylococcal infection or 48 h later. Teicoplanin was given intravenously at a dosage of 6 mg/kg of body weight at 0, 12, and 24 h and once a day thereafter. Five to eleven blood samples per patient were collected. Teicoplanin concentrations were measured by liquid chromatography. A bicompartmental model was fitted to the data by a nonlinear mixed-effect-model approach. Multiple-linear regression analysis was applied in an attempt to correlate PK parameters to nine covariates. The mean trough concentrations of teicoplanin 48 h after the onset of treatment and 24 h after the last injection (last trough) +/- standard deviations were 8.8 +/- 4.1 and 17.5 +/- 13.5 mg/liter, respectively. A significant increase was noted in the mean rate of elimination clearance of teicoplanin in neutropenic patients compared with that of HV (0.86 versus 0.73 liter/h, P = 0.002), as was the case with rates of distribution clearance (5.89 versus 4.94 liter/h, P = 0.002); the mean half-life of distribution was significantly shorter in patients than in HV (0.43 versus 0.61 h, P = 0.002). In contrast, the volumes of the central compartment (ca. 5.8 liters for both groups), the volumes of distribution at steady state (HV, 37.6 liters; patients, 55.9 liters), and the elimination half-lives (HV, 39.6 h; patients, 52.7 h) were not significantly different between HV and neutropenic patients. Interindividual variabilities of rates of clearance (coefficient of variation [CV], 43%) and elimination half-lives (CV, 56%) were mainly explained by the variabilities among rates of creatinine clearance. Interindividual variabilities of the volumes of the central compartment (CV, 33%) and the volumes of distribution at steady state (CV = 51%) were correlated to interindividual variabilities among numbers of leukocytes and the ages of patients, respectively. On the basis of the population PK model of teicoplanin, simulations were made to optimize the dosing schedule. A supplemental 6 mg/kg dose of teicoplanin at 36 h resulted in a trough concentration at 48 h of 16.0 +/- 4.5 mg/liter, with only 7% of patients having a trough concentration of less than 10 mg/liter, compared with 46% of patients on the usual schedule.

Efficacy of vancomycin and teicoplanin alone and in combination with streptomycin in experimental, low-level vancomycin-resistant, VanB-type Enterococcus faecalis endocarditis

The efficacy of vancomycin (VM) and teicoplanin (TE), alone and in combination with streptomycin (SM), against enterococci that express low-level VanB-type VM resistance was investigated in experimental endocarditis using isogenic strains of Enterococcus faecalis susceptible to glycopeptides and aminoglycosides or inducibly resistant to low levels of VM (MIC = 16 micrograms/ml). VM was significantly less active against the resistant strain than against the susceptible strain, establishing that low-level VanB-type VM resistance can influence therapeutic efficacy. By contrast, TE had equally good activity against both strains. VM or TE combined with SM was synergistic and bactericidal against the resistant strain in vitro. While both combinations were efficient in reducing bacterial density in vivo, TE plus SM was significantly superior to VM plus SM if valve sterilization was considered. These data suggest that despite the presence of low-level VanB-type resistance, combination therapy with a glycopeptide and SM (and presumably other aminoglycosides to which there is not high-level resistance) will nevertheless provide effective bactericidal activity.

Micrococcus luteus endocarditis: case report and review of the literature

This paper includes a report on a case of prosthetic valve endocarditis due to Micrococcus luteus and a review of the sixteen cases of endocarditis due to Micrococcus species reported in the literature. The patient was successfully treated with rifampicin combined for two weeks with gentamicin and vancomycin and for another four weeks with teicoplanin. The hospital course was uneventful and no surgery was required.

Protein binding and serum bactericidal activities of vancomycin and teicoplanin

In a randomized crossover study, the protein binding and serum bactericidal activities (SBAs) of vancomycin and teicoplanin against Staphylococcus aureus and Streptococcus pyogenes were investigated in six healthy volunteers. Total concentrations in serum 1 h postadministration of vancomycin and teicoplanin were 25.5 +/- 2.7 and 10.8 +/- 8.9 mg/liter, respectively; mean free concentrations were 14.6 +/- 2.0 and 0.6 +/- 0.9 mg/liter, respectively. Protein binding for vancomycin was 36.9% +/- 2.87%, and that for teicoplanin was 97.4% +/- 2.6%. SBA determined in pooled human serum at 1 h against S. aureus ranged from 1:8 to 1:32 for both vancomycin and teicoplanin. Against S. pyogenes SBA at 1 h ranged from 1:16 to 1:128 for vancomycin and 1:256 to 1:2,048 for teicoplanin. In vitro kill curve studies showed that vancomycin is slowly bactericidal and that teicoplanin is bacteriostatic. Despite having less in vitro cidal activity against the study isolates and having low or unrecordable levels of free drug in serum, teicoplanin demonstrated a similar or better SBA than vancomycin. SBA was more closely related to the total drug level (r = 0.77 for S. aureus and r = 0.79 for S. pyogenes) than the free level of teicoplanin (r = 0.59 for S. aureus and r = 0.56 for S. pyogenes). The high level of protein binding of teicoplanin did not seem to impair its antibacterial activity as measured by its SBA.

Experience with outpatient intravenous teicoplanin therapy for chronic osteomyelitis

Thirty-seven patients with acute exacerbations of chronic osteomyelitis caused by methicillin-susceptible Staphylococcus aureus (n = 13), methicillin-resistant Staphylococcus aureus (n = 12), methicillin-susceptible coagulase-negative staphylococci (n = 9), methicillin-resistant coagulase-negative staphylococci (n = 1) and enterococci (n = 2) were treated intravenously with teicoplanin. After a loading dose of 7 to 16 mg/kg (median 11 mg/kg) for 4 to 7 days, patients received 9 to 25 mg/kg (median 14 mg/kg) on Mondays, Wednesdays and Fridays in an outpatient setting to reach trough serum levels between 5 mg/l and 15 mg/l. The duration of treatment ranged from 28 to 150 days (median 60 days). Cure was obtained in 14 (38%) and improvement in 17 (46%) cases, and failure was observed in 6 (16%) patients. Adverse effects occurred in 6 patients, and caused discontinuation of treatment in 3 patients. The financial savings exceeded US$60,000 per patient compared with the high hospitalization costs of inpatient treatment.

The importance of pharmacokinetic/pharmacodynamic surrogate markers to outcome. Focus on antibacterial agents

Pharmacokinetic/pharmacodynamic surrogate relationships have been used to describe the antibacterial activity of various classes of antimicrobial agents. Studies that have evaluated these relationships were reviewed to determine which of these surrogate markers were further dependent on antimicrobial class. The fluoroquinolone and aminoglycoside agents exhibit concentration-dependent killing. Studies have demonstrated that peak serum concentration: minimum inhibitory concentration (MIC) and area under the serum concentration-time curve (AUC): MIC ratios are important predictors of outcome for these antimicrobial agents. Area under the inhibitory concentration-time curve (AUIC24) [i.e. AUC24/MIC] is a useful parameter for describing efficacy for these agents, while an adequate peak concentration: MIC ratio seems necessary to prevent selection of resistant organisms. For beta-lactam antibiotics, the duration of time that the serum concentration exceeds the MIC (T > MIC) was the significant pharmacokinetic/pharmacodynamic surrogate in cases where the bacterial inoculum was low, or where very sensitive organisms were tested. However, in studies using more resistant organisms or larger inoculum sizes there is some concentration-dependence to the observed effect. Studies using reasonable dosage intervals have demonstrated covariance between T > MIC and AUC/MIC ratio for beta-lactam antibiotics. Since glycopeptide antibiotics display relatively slow but concentration-independent killing, and are cell wall active agents similar to beta-lactams, it has been presumed that T > MIC is the important pharmacokinetic surrogate related to efficacy for these agents. Some studies have shown that a concentration multiple of the MIC may be necessary for successful outcome with vancomycin. AUIC24 may prove to be an important pharmacokinetic surrogate if both time and concentration are indeed important parameters. To select an appropriate antimicrobial agent, the clinician must consider many patient-specific as well as organism-specific factors. Utilisation of known pharmacokinetic/pharmacodynamic surrogate relationships should help to optimise treatment outcome.

Use of teicoplanin in community medicine

Administration of parenteral antibiotics to outpatients is increasingly used to reduce hospital costs, to reduce loss of earnings for the patient and to improve the quality of life in patients requiring prolonged antibiotic treatment. The glycopeptides are required for treatment of infections caused by methicillin resistant staphylococci and some enterococci, or for treatment of patients allergic to beta-lactam agents. For home therapy, teicoplanin has some advantages over vancomycin in that it requires only once-daily bolus administration, does not necessitate monitoring of serum concentrations and offers the choice of intravenous or intramuscular administration. Teicoplanin has been used to complete treatment of endocarditis at home in selected patients, streptococcal disease being the most suitable form of endocarditis for this treatment. In open trials, teicoplanin has been found effective in home therapy of osteomyelitis but, as with other agents, prolonged dosage can be associated with adverse effects. It has also been used for home treatment of infections of the respiratory tract, intravascular catheters and soft tissue. Despite its higher acquisition costs, teicoplanin is to be preferred over vancomycin because of the reduced administration and assay costs and fewer adverse effects.

Teicoplanin alone or combined with rifampin compared with vancomycin for prophylaxis and treatment of experimental foreign body infection by methicillin-resistant Staphylococcus aureus

The prophylactic and therapeutic activities of teicoplanin were evaluated in two different experimental models of foreign body infections caused by methicillin-resistant Staphylococcus aureus (MRSA). In a guinea pig model of prophylaxis, subcutaneously implanted tissue cages were infected at a > 90% rate by 10(2) CFU of MRSA in control animals. A single dose of 30 mg of teicoplanin per kg of body weight administered intraperitoneally 6 h before bacterial challenge was as effective as vancomycin in preventing experimental infection in tissue cages injected with either 10(2), 10(3), or 10(4) CFU of MRSA. In a rat model evaluating the therapy of chronic tissue cage infection caused by MRSA, the efficacy of a 7-day high-dose (30 mg/kg once daily) regimen of teicoplanin was compared with that of vancomycin (50 mg/kg twice daily). Whereas high levels of teicoplanin were found in tissue cage fluid, continuously exceeding its MBC for MRSA by 8- to 16-fold, no significant reduction in the viable counts of MRSA occurred during therapy. In contrast, either vancomycin alone or a combined regimen of high-dose teicoplanin plus rifampin (25 mg/kg twice daily) could significantly decrease the viable counts in tissue cage fluids. Whereas the bacteria recovered from tissue cage fluids during therapy showed no evidence of teicoplanin resistance, they failed to be killed even by high levels of this antimicrobial agent. The altered susceptibility of in vivo growing bacteria to teicoplanin killing might in part explain the defective activity of this antimicrobial agent when used as monotherapy against chronic S. aureus infections. These data may indicate the need for a combined regimen of teicoplanin with other agents such as rifampin to optimize the therapy of severe staphylococcal infections.

Role of tolerance in treatment and prophylaxis of experimental Staphylococcus aureus endocarditis with vancomycin, teicoplanin, and daptomycin

The role of Staphylococcus aureus tolerance in the treatment and prophylaxis of endocarditis in rats was investigated. The efficacies of vancomycin, teicoplanin, and daptomycin, alone and in combination with rifampin, were compared in rats with endocarditis infected with a tolerant strain of S. aureus and in rats with endocarditis infected with its nontolerant variant. In vitro the cloxacillin-tolerant strain was also tolerant to vancomycin and teicoplanin, but not to daptomycin. However, tolerance to these antibiotics did not influence the results of treatment of experimental S. aureus endocarditis. There was no difference in the bacterial densities in the vegetations of rats infected with either the tolerant or the nontolerant strain after 5 days of treatment with any of the antibiotic regimens. Of all antibiotics, daptomycin was the most effective in reducing bacterial numbers in vegetations. Combination of rifampin with vancomycin or teicoplanin improved the results of treatment for the tolerant as well as the nontolerant strains. Daptomycin was as effective alone as in combination with rifampin. In contrast, tolerance influenced the prophylactic effects of vancomycin and teicoplanin. The proportion of rats with sterile vegetations after prophylaxis with vancomycin or teicoplanin at a low dose was lower for those infected with the tolerant strain than for those infected with the nontolerant strain. A low dose of daptomycin was equally effective against the tolerant and the nontolerant strains. However, higher doses of all three antibiotics afforded almost full protection against both strains.

4-week treatment of streptococcal native valve endocarditis with high-dose teicoplanin

The efficacy and safety of a 4-week course of intravenous teicoplanin (500 mg every 12 h for the first 2 days and 10 mg/kg of body weight every 24 h thereafter) in the treatment of streptococcal native valve endocarditis in 20 patients were evaluated. All blood isolates were inhibited by a concentration of 0.12 micrograms of teicoplanin per ml. Serum bactericidal activity levels were measured 1/2 and 24 h after antibiotic infusion on days 5 to 7 of therapy in 19 patients, and titers of greater than or equal to 1:32 and greater than or equal to 1:8, respectively, were obtained with 17 patients (89%). On the other hand, for two patients who were infected with teicoplanin-tolerant Streptococcus bovis, serum bactericidal activity levels of less than 1:2 were found. Of 20 patients, 4 were excluded from further analysis because of protocol violation or prosthetic valve infection. Of the remaining 16 patients, 6 did not complete teicoplanin therapy because of early death (1 patient) or drug fever (5 patients). Among patients who developed drug fever, three who discontinued teicoplanin by day 15 were switched to penicillin therapy, whereas the remaining two, who discontinued teicoplanin on day 22 and 25, respectively, did not receive any further therapy and have shown no relapse during the follow-up. Of 10 patients who completed trial therapy, 9 were cured and 1 relapsed. It is concluded that a 4-week course of high-dose teicoplanin may be a useful regimen for home treatment of selected cases of streptococcal native valve endocarditis. However, drug fever and infection with teicoplanin-tolerant S. bovis may be factors of concern with this therapeutic approach.

[The role of the bacteriological laboratory in the criteria for choosing and monitoring antibiotic treatment]

The constant development of clinical bacteriology and the consequence this has on the way an infected patient is approached and treated require that be examined a bacteriology laboratory's contribution in choosing and monitoring an antibiotic treatment. In the economic context of hospitals, one of the aims is to rationalize the prescription of biological investigations, as well as that of antibiotic treatments. The patient's history, his clinical state as well as the place where he has been admitted must be taken into account to establish, together with microbiologists, a hierarchy of the biological investigations required and to adapt the antibiotic treatment. In the laboratory, both the bacteriostatic and bactericidal sensitivity to antibiotics may be assessed in vitro. The best therapeutic antibiotic concentrations may be obtained by monitoring the pharmacokinetics of antibiotics.

Double-blind comparison of teicoplanin versus vancomycin in febrile neutropenic patients receiving concomitant tobramycin and piperacillin: effect on cyclosporin A-associated nephrotoxicity

A prospective, randomized, and double-blind study comparing teicoplanin with vancomycin in the initial management of febrile neutropenic patients was conducted. Teicoplanin was administered at 6 mg per kg of body weight every 24 h (q24h) intravenously (i.v.) after initial loading at 6 mg/kg q12h for three doses. Vancomycin was administered at 15 mg/kg q12h i.v. Patients also received piperacillin (3 g q4h i.v.) and tobramycin (1.5 to 2.0 mg/kg q8h i.v.). Of 53 patients enrolled, 50 were judged to be evaluable. Among these, 25 received teicoplanin and 25 received vancomycin. At enrollment, both groups were comparable in age, sex, renal function, underlying hematologic condition, and concurrent therapy. Both groups had similar sites of infection and microbial pathogens. Empirical antimicrobial therapy resulted in the cure of or improvement in 23 (92%) teicoplanin patients and 21 (84%) vancomycin patients (P = 0.67). Failures occurred with two vancomycin patients but no teicoplanin patients. Clinical response was indeterminate for two patients in each group. Adverse reactions occurred significantly more often in the vancomycin group than in the teicoplanin group (P = 0.01), and these reactions required the termination of the study regimens of 6 vancomycin versus 0 teicoplanin patients (P = 0.02). Nephrotoxicity was observed more frequently in the vancomycin group (10 versus 2 patients; P = 0.02). Subgroup analysis revealed a significant deterioration of renal function when vancomycin and cyclosporin A, but not teicoplanin and cyclosporin A, were used concurrently (P = 0.02). Among patients who received vancomycin and amphotericin B or teicoplanin and amphotericin B concurrently, deterioration in renal function was equivalent in both groups. Teicoplanin in the dosage employed was tolerated better than vancomycin in the empirical treatment of fever and neutropenia in our patient population.

An open study of teicoplanin in the treatment of gram-positive infections

Teicoplanin, a new glycopeptide antibiotic similar to vancomycin, was evaluated in treating 36 hospitalized patients suffering from various Gram-positive infections. The 36 patients received teicoplanin once daily as a mean intravenous injection of 550 mg/day (range 200-800 mg/day). Previous antimicrobial therapy was used in 28% of patients. The mean duration of therapy was 7.5 days (range 3-38 days). The overall clinical success rate was 94%. 24/36 patients (66%) had positive microbiology. Elimination of the pathogens was seen in 75% of all evaluable cases. Four patients with early prosthetic valve endocarditis due to coagulase negative Staphylococcus (3 patients) and Propionibacterium acnes (1 patient) had a favorable clinical and microbiological outcome. No adverse drug reactions were observed. Teicoplanin is safe and effective in the therapy of many different infections caused by Gram-positive bacteria.

Intravenous or intramuscular teicoplanin once daily for skin and soft-tissue infections

Teicoplanin is a new glycopeptide antibiotic with potent activity against gram-positive bacteria and pharmacokinetics that allow once daily administration. To study the efficacy and safety of teicoplanin for skin and soft-tissue infections, 75 patients received teicoplanin intravenously (38) or intramuscularly (37, of which 16 were outpatients). Of 62 clinically evaluable patients, 97 percent of teicoplanin iv and 93 percent of teicoplanin im patients were cured or improved. All teicoplanin iv patients and 64 percent of teicoplanin im patients were cured microbiologically at 24-48 hours posttherapy. Persistence of organisms frequently was associated with skin ulcers or abscess cavities and usually had no bearing on clinical outcome. Possible adverse clinical and laboratory reactions caused by teicoplanin occurred in 4 of 38 teicoplanin iv patients (11 percent) and in 8 of 37 teicoplanin im patients (22 percent). Reactions were mild and resolved with discontinuation of teicoplanin in most cases. In this study, teicoplanin appeared to be safe, efficacious, and convenient for both hospital staff and patients, and potentially cost-effective for the treatment of skin and soft-tissue infections. In particular, teicoplanin appears to be appropriate for outpatient parenteral therapy.

Teicoplanin in perspective. A critical comparison with vancomycin

Teicoplanin is a new glycopeptide antibiotic with a chemical structure related to vancomycin. The proposed advantages of teicoplanin over vancomycin are discussed. These include lower incidence of side-effects, lower toxicity (especially in combination with aminoglycosides), lower dosage frequency and the possibility of intramuscular administration. There is only a limited number of studies comparing both agents; more studies are still needed before firm conclusions can be drawn. Therapeutic drug monitoring is not usually necessary for teicoplanin; the situation is not clear for vancomycin. There is some doubt whether the incidence of resistance is as infrequent for teicoplanin as it is for vancomycin. Teicoplanin appears to be a promising alternative to vancomycin, but more data are needed on the relative clinical efficacy and the development of resistance to both drugs.

Influence of low-level resistance to vancomycin on efficacy of teicoplanin and vancomycin for treatment of experimental endocarditis due to Enterococcus faecium

Emergence of vancomycin-resistant strains among enterococci raises a new clinical challenge. Rabbits with aortic endocarditis were infected with Enterococcus faecium BM4172, a clinical strain resistant to low levels of vancomycin (MIC, 16 micrograms/ml) and susceptible to teicoplanin (MIC, 1 micrograms/ml), and against its susceptible variant E. faecium BM4172S obtained in vitro by insertional mutagenesis (MICs, 2 and 0.5 micrograms/ml, respectively). Control animals retained 8 to 10.5 log10 CFU/g of vegetation. We evaluated in this model the efficacy of vancomycin (30 mg/kg of body weight; mean peak and trough serum levels, 27 and 5 micrograms/ml, respectively), teicoplanin (standard dose, 10 mg/kg; mean peak and trough levels, 23 and 9 micrograms/ml, respectively; and high dose, 20 mg/kg; mean peak and trough levels, 63 and 25 micrograms/ml, respectively), gentamicin (6 mg/kg; mean peak and trough levels, 8.6 and less than 0.1 micrograms/ml, respectively), alone or in combination, given every 12 h intramuscularly for 5 days. Teicoplanin standard dose was as active as vancomycin against both strains. Vancomycin was not effective against E. faecium BM4172 but was highly effective against E. faecium BM4172S (7.5 +/- 1.1 log10 CFU/g of vegetation versus 4.9 +/- 1.0 log10 CFU/g of vegetation for vancomycin against E. faecium BM4172 and E. faecium BM4172S, respectively; P = 0.0012). A high dose of teicoplanin was more effective than vancomycin against E. faecium BM4172 (4.4 +/- 1.8 log10 CFU/g of vegetation versus 7.5 +/- 1.1 log10 CFU/g of vegetation for teicoplanin high dose and vancomycin, respectively; P less than 0.05). Against E. faecium BM4172 glycopeptide-gentamicin combinations were the most effective regimens in vitro and in vivo (2.8 +/- 0.7 and 3.5 +/- 1.3 log10 CFU/g of vegetation for vancomycin plus gentamicin and teicoplanin standard dose plus gentamicin, respectively; P < 0.05 versus single-drug regimens). We concluded that high-dose teicoplanin or the combination of a glycopeptide antibiotic plus gentamicin was effective against experimental infection due to E. faecium with low-level resistance to vancomycin.

Comparative effect of protein binding on the killing activities of teicoplanin and vancomycin

The effect of protein binding on the activity of teicoplanin against Staphylococcus aureus was evaluated. Bactericidal rates of teicoplanin in cation-supplemented Mueller-Hinton broth (SMHB) and in a 1:1 mixture of pooled human serum and cation-supplemented Mueller-Hinton broth (PHS-SMHB) were compared with those of vancomycin. Eight concentrations of each drug ranging from 15 to 150 micrograms/ml were studied in two series which correspond to the concentrations in serum achieved with low- (6 mg/kg of body weight once daily) and high-dose (30 mg/kg once daily) teicoplanin. Overall, the bactericidal rate of teicoplanin was lower than that of vancomycin. In the presence of serum, the bactericidal rate of teicoplanin in PHS-SMHB was lower than that in SMHB, often resulting in only one log10 drop in CFU over a 24-h period. There was no statistical difference in the bactericidal rates of high- and low-concentration teicoplanin in either medium. Additionally, concentration-dependent killing in SMHB was not evident with either agent. The bactericidal rates of teicoplanin and vancomycin in a 1:1 mixture of serum ultrafiltrate and SMHB at 60 micrograms/ml were also studied. It was noted that the bactericidal rate of neither agent was affected by the presence of serum ultrafiltrate. This finding is consistent with teicoplanin's high degree of protein binding (reported to be greater than 90% in undiluted serum) and further substantiates the hypothesis that only the free drug is active against microorganisms. These data support protein binding as being a factor in teicoplanin activity against S. aureus.

Randomized study of vancomycin versus teicoplanin for the treatment of gram-positive bacterial infections in immunocompromised hosts

Seventy-four immunocompromised patients with severe infection due to gram-positive organisms were randomized to receive either vancomycin or teicoplanin. Extensive cancer was present in 71 patients, of whom 47 died within a month. The types of infections were 46 bacteremias (39 associated with central catheters), 24 skin and soft tissue infections (3 with bacteremia), and 7 others (mainly bronchopneumonia). The most frequent pathogen was Staphylococcus epidermidis, followed by Staphylococcus aureus. Microbiological eradication was obtained in 23 of 35 evaluable patients treated with vancomycin (65.7%) and 28 of 36 patients treated with teicoplanin (77.8%) (P = 0.4). Clinical cure and improvement were obtained in 26 of 35 patients (74.3%) and 27 of 36 patients (75.0%), respectively. No significant side effects were observed with teicoplanin, in contrast to reversible increases in serum creatinine (three patients) and skin rashes (four patients) with vancomycin. Superinfection was observed in five patients treated with vancomycin and two patients treated with teicoplanin. No relation was found between peak concentration in serum (at steady state) or bactericidal titers and outcome.

Treatment of infection and colonization caused by methicillin-resistant Staphylococcus aureus

The mechanism of methicillin resistance confers resistance to all available beta-lactam antibiotics; consequently, beta-lactam antibiotics have no role in therapy of methicillin-resistant Staphylococcus aureus (MRSA) infections. Vancomycin remains the drug of choice. Teicoplanin and daptomycin are two investigational antibiotics related to vancomycin in structure and in spectrum of activity. In clinical trials employing relatively low doses, neither was as effective as vancomycin. Trials at higher doses are on-going. Quinolones, ciprofloxacin in particular, have been used successfully to treat infections caused by MRSA; however, the usefulness of quinolones may be limited by the tendency of resistance to emerge during therapy. Quinolones probably should be used only in combination with another active agent, such as rifampin, when treating serious infections caused by MRSA. Other agents may be active in vitro against MRSA, but clinical data showing their effectiveness are lacking. Rifampin combination regimens appear most effectively to eradicate colonization with MRSA.

Failure of treatment with teicoplanin at 6 milligrams/kilogram/day in patients with Staphylococcus aureus intravascular infection. The Infectious Diseases Consortium of Oregon

Patients with blood cultures positive for gram-positive cocci were enrolled in a prospective randomized double-blind comparative trial of vancomycin at 15 mg/kg every 12 h versus teicoplanin at 6 mg/kg every 12 h for three doses and then 6 mg/kg every 24 h. A total of 54 patients were randomized, and 40 were evaluable. Of the 40, 9 had infection of indwelling vascular catheters. Four infections were due to Staphylococcus aureus, and five were due to Staphylococcus epidermidis. In concert with catheter removal, all patients were treated successfully, regardless of which drug they were taking. Of 31 patients without an indwelling catheter, 19 were infected with S. aureus, and 12 of the 19 had either endocarditis or mycotic aneurysm. Six of eight patients given teicoplanin failed treatment, as opposed to one of four patients given vancomycin (P = 0.14). Of greater concern, four of four patients with left-sided endocarditis or mycotic aneurysm failed to recover when given teicoplanin, as opposed to one of three patients given vancomycin (P = 0.07). Although not quite statistically significant, the unexpectedly high number of treatment failures with teicoplanin resulted in a decision to discontinue patient enrollment. It is suggested that future trials explore the efficacy of larger doses of teicoplanin.

Treatment of bone, joint, and vascular-access-associated gram-positive bacterial infections with teicoplanin

Teicoplanin, a glycopeptide antibiotic, was evaluated for safety and efficacy in the treatment of vascular-access-associated bacteremias and of bone and joint infections due to susceptible gram-positive organisms. Of 35 patients enrolled, 26 had osteomyelitis, 8 had vascular-access-associated bacteremias, and 1 had a joint infection. A total of 38 gram-positive isolates were identified: 23 Staphylococcus aureus and 6 coagulase-negative staphylococcus and 9 streptococcus isolates. After at least 6 months of follow-up, 17 patients were evaluable for efficacy: 10 of 14 (71%) with osteomyelitis and 3 of 3 with vascular-access-associated bacteremias had full resolution of their infections. Inadequate debridement, the presence of metal, and inadequate dosing were likely causes of two failures and two relapses in patients with osteomyelitis. For all but two organisms, teicoplanin MICs were less than or equal to 2 micrograms/ml. Patients who responded had median peak and trough serum bactericidal levels at serum dilutions of 1:64 and 1:16; trough levels of teicoplanin in serum were greater than 30 micrograms/ml. Patients did not respond as expected to daily doses of 4 mg/kg of body weight, which consequently were increased to greater than or equal to 15 mg/kg. Audiology testing of 20 patients found 2 with a mild loss of high-frequency hearing; 1 patient complained of tinnitus. Patients tolerated peak levels in serum as high as 127 micrograms/ml and trough levels of 49 micrograms/ml. However, 5 of 18 patients (28%) whose daily dose was greater than or equal to 12 mg/kg developed drug fever and rash and had teicoplanin discontinued. Further study of the antibiotic at such higher doses is needed.

Teicoplanin pharmacokinetics in healthy volunteers after administration of intravenous loading and maintenance doses

Teicoplanin is an investigational glycopeptide antibiotic that is structurally and microbiologically similar to vancomycin. Since teicoplanin possesses a very long elimination half-life, the manufacturer suggests that the drug be administered every 12 h for the first day of therapy and once daily thereafter. We studied the multiple-dose (6 mg/kg per dose) pharmacokinetics of teicoplanin in volunteers following intravenous administration every 12 h for 5 days and then every 24 h for 9 days in an attempt to identify the optimal duration of the every-12-h loading-dose regimen. Multiple serum samples were obtained throughout the study, including intensive sampling after the first and last doses; urine was collected during the entire study. A three-exponential equation was fitted to the serum concentration data. The mean terminal-phase half-life was 157 +/- 93 h. Concentrations of teicoplanin in serum similar to those observed after the administration of the last dose (day 14) were observed following the fourth or fifth dose given every 12 h. Therefore, it is suggested that for clinical dosing regimens for teicoplanin, dosing every 12 h for approximately 48 h should be used, followed by once-daily dosing thereafter.

Antimicrobial susceptibilities of Erysipelothrix rhusiopathiae

The in vitro susceptibilities of 10 isolates of Erysipelothrix rhusiopathiae to 16 antimicrobial agents were determined. Penicillin and imipenem were the most active agents, followed by piperacillin, cefotaxime, ciprofloxacin, pefloxacin, and clindamycin. Some resistance was observed with erythromycin, tetracycline, and chloramphenicol. Activity was poor or absent with vancomycin, teicoplanin, daptomycin, trimethoprim-sulfamethoxazole, gentamicin, and netilmicin.

Teicoplanin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic potential

Teicoplanin is a glycopeptide antibiotic with a molecular structure which is related to that of vancomycin. Gram-positive bacteria such as staphylococci (including methicillin-resistant strains), streptococci, enterococci and many anaerobic Gram-positive bacteria are susceptible to teicoplanin in vitro. Teicoplanin has an exceptionally long half-life, allowing once-daily intramuscular or intravenous administration. Teicoplanin is clinically and bacteriologically effective against a wide variety of Gram-positive infections such as septicaemia, endocarditis, skin and soft tissue infections and infections associated with venous catheters. The drug is equally efficacious against methicillin-resistant and -susceptible staphylococci. Adverse effects with teicoplanin are generally limited to local effects or hypersensitivity reactions. While teicoplanin has the potential for ototoxicity and nephrotoxicity, the incidence appears to be quite low when recommended serum concentrations are maintained. Teicoplanin is a valuable alternative to vancomycin, and providing controlled comparative studies prove equivalent safety and efficacy between the 2 glycopeptides the more easily administered teicoplanin should become the preferred antibacterial agent.

Efficacy of teicoplanin in two dosage regimens for experimental endocarditis caused by a beta-lactamase-producing strain of Enterococcus faecalis with high-level resistance to gentamicin

Optimal therapy for the treatment of infections caused by strains of enterococci demonstrating high-level resistance to gentamicin and other aminoglycosides has not been established. The present study examined the efficacy of teicoplanin, a glycopeptide antibiotic active against gram-positive bacterial infections in various animal models, in the treatment of experimental endocarditis due to a beta-lactamase-producing strain of Enterococcus faecalis with high-level resistance to gentamicin. Vancomycin was used as a comparative antibiotic. In the first set of experiments, both antimicrobial agents were administered by continuous intravenous infusion for 5 days at dosages which yielded comparable mean levels in serum (plus or minus the standard deviation) of 14.6 +/- 4.3 micrograms/ml for teicoplanin and 14.3 +/- 2.2 micrograms/ml for vancomycin. These regimens proved similarly effective in sterilizing cardiac vegetations (38 versus 50% of treated animals, respectively; P greater than 0.05). Mean (plus or minus the standard deviation) residual bacterial titers within vegetations were reduced to 3.2 +/- 1.2 log10 CFU/g and 3.4 +/- 1.7 log10 CFU/g, respectively. In separate experiments, the potential of teicoplanin to cure endocarditis was assessed, using two dosage regimens: (i) 30 mg/kg per day (mean level in serum, 13 micrograms/ml) for 10 days or (ii) 150 mg/kg per day (mean level in serum, 84 micrograms/ml) for 5 days. Surviving animals were sacrificed 10 days after the discontinuation of therapy. Both teicoplanin regimens were more effective than the comparative vancomycin (150 mg/kg per day) regimen: 92 versus 43% cured (P =0.025) in the standard-dose group, and 82 versus 37% cured (P = 0.015) in the high-dose group. Results in this rat model of enterococcal endocarditis show that teicoplanin may prove useful in the treatment of serious infections due to high level-gentamicin-resistant enterococci in humans.

Effects of dosage, peak and trough concentrations in serum, protein binding, and bactericidal rate on efficacy of teicoplanin in a rabbit model of endocarditis

The effect of dosage and the relative importance of peak and trough concentrations in serum for efficacy of teicoplanin were examined in a rabbit model of aortic valve endocarditis. Concentrations of teicoplanin in serum exceeded the MIC by several hundredfold, yet teicoplanin was less rapidly bactericidal than penicillin both in vitro and for endocarditis caused by a strain of Streptococcus sanguis. Because teicoplanin was 90% protein bound in rabbit serum, low free-drug concentrations probably resulted in less activity in vivo than in vitro. Because teicoplanin has a relatively low bactericidal rate and a high degree of protein binding, a sustained concentration in serum several times greater than the MIC may be important for efficacy in vivo. An intravenous regimen with relatively high peak concentrations in serum was less effective than an intramuscular regimen for endocarditis caused by a strain of Staphylococcus aureus, indicating that high peaks are unlikely to be an important determinant of efficacy. The therapeutically more relevant concentration in serum may be the trough.