Comparative in vitro activities of teichomycin and vancomycin alone and in combination with rifampin and aminoglycosides against staphylococci and enterococci

Efficacy of teicoplanin, administered in two different regimens, in the treatment of experimental endocarditis due to Enterococcus faecalis

Using a rabbit model of endocarditis, we studied the efficacy of teicoplanin against a strain of Enterococcus faecalis resistant to ampicillin. Rabbits were randomly assigned to receive no antibiotics, teicoplanin 12 or 18 mg/kg of body weight every 12h, for 9 days. The effect of treatment on bacterial counts of vegetations and survival of the animals was evaluated at the end of treatment and 10 days thereafter. The two treatment regimens of teicoplanin produced peak serum levels 18.51+/-1.84 and 34.66+/-4.19 microg/ml, and trough levels above 10 x MIC of teicoplanin for the infecting organism. Both regimens resulted in significant bacterial reduction in the vegetations as compared to the control group (p<0.001). The drug prevented relapse of the infection 10 days after discontinuation of treatment. By increasing the teicoplanin dosage no additional therapeutic benefit was observed in terms of bacterial killing, sterilization of the vegetations, and survival of the animals, although the higher doses gave numerically superior results. These findings may have meaning for the optimum use of teicoplanin in the treatment of enterococcal endocarditis.

Bacteraemia caused by coagulase-negative staphylococci exhibiting decreased susceptibility to teicoplanin

The purpose of our study was to assess the prevalence of coagulase-negative staphylococci (CoNS) isolates with reduced susceptibility to glycopeptides among the isolates responsible for bloodstream infections and to describe the epidemiology of these isolates. CoNS isolates from bloodstream infections were collected and characterized by analysis of antibiotic susceptibility and restriction fragment length polymorphism using pulsed-field gel electrophoresis. The medical records of patients with positive cultures and trends in glycopeptide use were reviewed to determine the effect of previous antibiotic treatment on the susceptibility profile of these organisms. The crude incidence of CoNS bacteraemia was 0.51 per 1000 days of hospitalization. The 15 (28.8%) strains identified as having decreased susceptibility to teicoplanin by the reference method were all hospital-acquired and displayed 13 different DNA patterns. The relative risk of harbouring strains with decreased susceptibility to teicoplanin was 3.55 among patients previously treated with vancomycin (confidence interval 95%: 2.15-5.85). The teicoplanin consumption in our institution was constant and represented about 27% of the glycopeptide consumption in daily defined doses. The implementation of programmes aiming to reduce the unnecessary use of glycopeptides should have a significant impact on the reduced-susceptibility rate because strains probably become resistant as a result of antibiotic pressure.

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.

Constant rate infusion of vancomycin in premature neonates: a new dosage schedule

AIMS

Since vancomycin's bactericidal action has been shown to be time-dependent, a constant rate infusion over 24 h might result in a better bactericidal efficacy. The purpose of this study was to define a new dosage schedule in prematures.

METHODS

Two vancomycin 24 h constant rate infusion schedules were tested in two groups of neonates. Postconceptional age (PCA) was 27 to 41 weeks in group 1 (n=24) and 28 to 51.5 weeks in group 2 (n=29). Group 1 neonates received continuous infusion of 10 to 30 mgkg(-1) day(-1), adjusted for PCA and weight. Group 2 was designed to take into account the significant relationship observed in group 1 between vancomycin clearance standardized on weight and PCA and consisted of a constant loading dose of 7 mg kg(-1) followed by continuous infusion of 10 to 40 mg kg(-1) day(-1) adjusted for PCA and weight.

RESULTS

Mean vancomycin serum concentration at steady state was 11+/-3.1 mg1(-1) in group 1 and 15.4+/-6.2 mg1(-1) in group 2. Fifty-six percent of group 1 values vs 88% of group 2 values were between 10 and 30 mg at steady state (P<0.01). Both regimens were well tolerated.

CONCLUSIONS

A loading dose of vancomycin followed by constant rate infusion of the appropriate dose adjusted for PCA and weight might improve vancomycin concentrations in neonates.

Vancomycin resistance in staphylococci

Recent emergence of vancomycin resistance in methicillin-resistant Staphylococcus aureus (VRSA) has posed a new threat to hospital infection control and antibiotic chemotherapy. Relatively low-level resistance of VRSA compared to that of vancomycin-resistant enterococci (VRE), and prevalence of S. aureus clinical strains heterogeneously resistant to vancomycin (hetero-VRSA), challenge the value of routine antibiotic susceptibility tests as a tool for the prediction of clinical efficacy of vancomycin therapy. This review summarizes the history of emergence of glycopeptide resistance in staphylococci and considers the mechanism of resistance in these organisms.

Antimicrobial interactions (synergy) of teicoplanin with two broad-spectrum drugs (cefotaxime, ofloxacin) tested against gram-positive isolates from Germany and the United States

Teicoplanin, a glycopeptide, has been widely used in some nations alone and in empiric therapy combinations to address infections caused by Gram-positive cocci. However, glycopeptide resistance and the increasing incidence of oxacillin-resistant staphylococci have compromised contemporary chemotherapy. In this study, teicoplanin was tested in combinations with ampicillin, cefotaxime with and without desacetylcefotaxime, and ofloxacin against 151 Gram-positive cocci to assess the potential for enhanced action. The strains included recent isolates from the United States and Germany having well-characterized resistance mechanisms (oxacillin-resistant staphylococci, vancomycin-resistant enterococci), each tested by NCCLS methods, checkerboard synergy tests, and kill-curves. Teicoplanin alone was active (MIC90s, 0.25-2 micrograms/mL) against all species except vanA enterococci. Drug interactions of teicoplanin with beta-lactams revealed synergy and partial synergy versus oxacillin-resistant Staphylococcus spp. (67-100%) and vancomycin-resistant enterococci (70-100%), many at clinically achievable drug concentrations. However, confirming kill-curve experiments showed static action and no significant bactericidal effect. Combinations of ofloxacin with teicoplanin or cefotaxime plus desacetylcefotaxime showed a dominant additive and indifferent interaction. Teicoplanin continues to be a viable alternative to vancomycin, especially in combination therapy with selected broad-spectrum cephalosporins or fluoroquinolones. Many emerging pathogens that test resistant to individual drugs appear to be inhibited by tested combinations, extending their potential clinical utility.

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.

In vitro evaluation of high-level, gentamicin-resistant enterococci isolated from bacteremic patients

We attempted to characterize the susceptibility of high-level, gentamicin-resistant (HLGR, minimum inhibitory concentration [MIC] > 2000 micrograms/ml) enterococcal blood isolates and evaluated a small subset of these isolates for bactericidal synergy. Thirteen Enterococcus faecalis and three Enterococcus faecium isolates that were HLGR were prospectively collected. Standard broth macrodilution techniques were used to determine the MICs and minimum bactericidal concentrations to a variety of antibiotics. Two isolates were evaluated for synergy by time-kill curve methods using combinations of penicillin and streptomycin, teicoplanin and rifampin, and vancomycin and ciprofloxacin. Teicoplanin was the most active antibiotic tested, with all isolates exhibiting susceptibility to this agent. Four E. faecalis isolates and one E. faecium isolate expressed only low-level resistance to streptomycin (LLSR, MICs 32-64 micrograms/ml). Penicillin and streptomycin produced bactericidal synergy in the LLSR isolate. The other antibiotic combinations did not result in bactericidal synergy in the two isolates tested. For HLGR enterococci that are only LLSR, the combination of penicillin-streptomycin appears to provide adequate bactericidal activity. Teicoplanin may potentially be useful for streptomycin-resistant HLGR isolates.

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.

Influence of rifampin therapy on serum bactericidal activity in the presence of cloxacillin and vancomycin

In this study the effect of rifampin on serum inhibitory and serum bactericidal titres was examined. Sera were prepared from pooled human serum to contain vancomycin (10 mg/L), cloxacillin (5 mg/L) or rifampin (1 mg/L), and the combinations cloxacillin/rifampin and vancomycin/rifampin. These five sera were tested by a microtitre method for serum inhibitory power and serum bactericidal titre against 11 strains of Staphylococcus aureus. A 48 h incubation period was required to detect full colony growth for subculture plates. It was found with all strains that the effect of the addition of rifampin to the other two antibiotics was to increase the serum inhibitory power, lower the serum bactericidal titre, increase the inhibitory/cidal ratio, and slow colony growth on subculture. In the clinical part of the study it was shown that only three of 38 sera (8%) from patients receiving betalactam or vanomycin but not rifampin gave an inhibitory/cidal ratio greater than 8, but that nine of 10 sera (90%) from patients receiving rifampin in addition to betalactam or vancomycin gave a ratio greater than 8 (P<0.001). The study verified that the effect of rifampin in serum was to increase inhibitory power and decrease bactericidal titre. The clinical significance of these results is not known and it is suggested that a high ratio of inhibitory to bactericidal titre in the presence of rifampin is to be expected, and that a low bactericidal titre under these circumstances is not necessarily an indication to modify therapy.

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

Teicoplanin, a new glycopeptide antibiotic similar to vancomycin, was evaluated for the treatment of bacterial endocarditis in an open multicenter study from May 1985 to August 1987. A total of 20 patients with positive blood culture endocarditis received teicoplanin once daily as a mean intravenous injection of 7.3 mg/kg of body weight (range, 4.8 to 10.6 mg/kg); in 17 patients, teicoplanin was combined with another antibiotic, usually an aminoglycoside. The mean duration of therapy was 28 days (range, 7 to 66 days). The diagnosis of endocarditis was confirmed by echocardiography or anatomical findings in 15 patients and established on the basis of clinical manifestations plus positive blood cultures in 5 patients. The tricuspid valve was involved in 11 of the 20 patients. Isolates from blood were 12 Staphylococcus aureus, 1 Staphylococcus hominis, 1 Micrococcus sedentarius, 1 Enterococcus faecalis, 3 Streptococcus bovis, and 2 nongroupable Streptococcus sp. At the end of therapy, bacterial eradication was achieved in 17 of 20 patients (85%), and a favorable clinical outcome had occurred in 14 of 17 evaluable patients (82%). Of these 14 patients, one relapsed 4 months after the end of treatment. Thus, teicoplanin was effective in 13 of 17 patients (76%). Mean peak levels of teicoplanin in serum were lower, 23.1 +/- 2.9 micrograms/ml, in patients who failed than in those who were cured (45.8 +/- 8.4 micrograms/ml). Side effects occurred in 7 of 20 patients (35%), and required premature discontinuation of teicoplanin in 3 patients. These side effects were fever in three patients, rash in three patients, hearing loss in two patients, and increased serum transaminase levels in two patients. This study demonstrates the efficacy of teicoplanin in the treatment of endocarditis and the need for achieving peak levels in serum close to 40 micrograms/ml. Teicoplanin should now be further evaluated in endocarditis caused by gram-positive cocci means of controlled comparative study with standard therapy.

Therapeutic update on glycopeptide and lipopeptide antibiotics

Glycopeptide antibiotics in the form of vancomycin have been available for almost 30 years. In the past, vancomycin usually was reserved as an alternative agent to treat staphylococcal and streptococcal infection in patients with a penicillin allergy or hemodialysis shunt infection. With the increasing frequency of both methicillin-resistant Staphylococcus aureus and Staphylococcus epidermidis, now it is often used as a first-line agent. Over a 10-year period, vancomycin sales have increased by almost $1 hundred million. Several new glycopeptide and lipopeptide antibiotics are in various stages of evaluation. While vancomycin resistance to date is a rare phenomenon, these drugs represent a potentially more potent and safer antibiotic alternative to vancomycin. Teicoplanin and daptomycin are two of these investigational agents.

Teicoplanin: a new glycopeptide antibiotic complex

The chemistry, microbiology, pharmacokinetics, clinical efficacy, and adverse effect profile of teicoplanin are reviewed and, where appropriate, compared with vancomycin. Teicoplanin is a glycopeptide antibiotic with potent bactericidal activity against a wide variety of aerobic and anaerobic gram-positive bacteria. In contrast to the structurally related vancomycin, teicoplanin has a prolonged elimination half-life of approximately 60 hours and it may be safely administered by the intramuscular route. Adverse effects of teicoplanin include ototoxicity, nephrotoxicity, skin rash, eosinophilia, neutropenia, and transient elevation of serum aminotransferases. Teicoplanin may be beneficial as an alternative to vancomycin for patients with poor vascular access and in those requiring long-term outpatient therapy. The role of teicoplanin in the treatment and prophylaxis of gram-positive infections will ultimately depend on its unfolding safety and efficacy profile.

Bactericidal activity and killing rate of serum in volunteers receiving teicoplanin alone or in combination with oral or intravenous rifampin

A total of 10 volunteers, in two groups of 5 each, received the following on separate days: group 1,200 mg of teicoplanin intravenously (i.v.), 600 mg of rifampin orally, or teicoplanin-rifampin; group 2,400 mg of teicoplanin i.v., 300 mg of rifampin i.v. in 60 min, or teicoplanin-rifampin. Blood samples were obtained before, at the end, and at 1 and 6 h after the administration of the antibiotics. Bactericidal activity in serum (SBA) was measured in microtiter plates against 20 clinical isolates (five strains each) of oxacillin-susceptible and-resistant Staphylococcus aureus and Staphylococcus epidermidis. The endpoint of the SBA corresponded to 99.9% killing. Killing rates were measured in serum obtained at 1 and 6 h. The concentrations of each antibiotic were measured by bioassay. The antibiotic concentrations in serum obtained at the peak and at 1 and 6 h after the end of administration were as follows: group 1, teicoplanin, 26, 15.6, and 8.4 mg/liter; rifampin, not determined, 8.3, and 3.8 mg/liter; group 2, teicoplanin, 66, 29.4, and 11.5 mg/liter; rifampin, 14.8, 3.8, and 1.2 mg/liter. Higher median SBAs were obtained after treatment with rifampin than after that with teicoplanin. No interaction was observed between rifampin and teicoplanin. This was confirmed by determination of the killing rate in serum. Teicoplanin killed more slowly than rifampin. The combination had the same killing rate as rifampin alone. Rifampin neither improved nor antagonized the bactericidal activity of teicoplanin, as determined by the SBAs or the rate of killing.

In vitro susceptibilities of four species of coagulase-negative staphylococci

The in vitro susceptibilities of 260 strains of coagulase-negative staphylococci to penicillin G, oxacillin, nafcillin, methicillin, cephalothin, and seven non-beta-lactam antimicrobial agents were determined and compared with the susceptibilities of 54 strains of Staphylococcus aureus with known patterns of susceptibility. Penicillin G susceptibility for S. aureus, Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus hominis was readily determined by using beta-lactamase tests with induced cells and with a standardized microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to the coagulase-negative species. Percentages of organisms susceptible were as follows: S. epidermidis, 7%; S. haemolyticus, 5%; and S. hominis, 47%. Oxacillin susceptibility for these four species was readily determined by using a modification of the microdilution test. MIC criteria for susceptibility used for S. aureus were applicable to S. haemolyticus and S. hominis, but alternate criteria were necessary for S. epidermidis. Percentages of organisms susceptible were as follows: S. epidermidis, 29%; S. haemolyticus, 36%; and S. hominis, 97%. Staphylococcus saprophyticus differed from the other staphylococcal species; all strains were beta-lactamase negative and were penicillin susceptible but had higher penicillin G MICs than did susceptible strains of the other species. There was total cross resistance among the penicillinase-resistant penicillins and cephalothin for the coagulase-negative staphylococci as well as for S. aureus; oxacillin MICs were more reliable than MICs of the other drugs or a standardized disk diffusion test for distinguishing resistant from susceptible strains. Vancomycin, rifampin, and ciprofloxacin were consistently active against all staphylococci. Erythromycin, clindamycin, gentamicin, and trimethoprim-sulfamethoxazole were more active against oxacillin-susceptible staphylococci than against oxacillin-resistant staphylococci.

Comparison of the in vitro activities of teicoplanin and vancomycin against Clostridium difficile and their interactions with cholestyramine

The in vitro activity of teicoplanin was compared with that of vancomycin against fecal isolates of Clostridium difficile. All strains were susceptible to both antibiotics, but teicoplanin was fourfold more active than vancomycin. Cholestyramine was found to bind teicoplanin almost completely, reducing its activity to nondetectable levels.

Comparison of the activities of coumermycin, ciprofloxacin, teicoplanin, and other non-beta-lactam antibiotics against clinical isolates of methicillin-resistant Staphylococcus aureus from various geographical locations

One hundred clinical isolates of methicillin-resistant (Metr) Staphylococcus aureus from five different geographical origins were tested for their susceptibility to 12 non-beta-lactam antibiotics by the broth microdilution technique recommended by the National Committee for Clinical Laboratory Standards. Coumermycin and rifampin showed the highest activity with of MIC90s of 0.032 micrograms/ml for each compound. No resistance was found to coumermycin, whereas a single Metr S. aureus strain was found to be resistant to rifampin. Ciprofloxacin, vancomycin, and teicoplanin were the next most active compounds with MIC90s of 0.25, 0.5, and 0.5 micrograms/ml, respectively. Norfloxacin was less active, with an MIC90 of 1.0 micrograms/ml. Amikacin was the most active aminoglycoside tested, whereas high levels of resistance were found to tobramycin and gentamicin. Doxycycline and chloramphenicol showed variable results. Geographical variations in results were seen with doxycycline, chloramphenicol, and aminoglycosides. Kill-curve studies showed that coumermycin, ciprofloxacin, teicoplanin, vancomycin, and rifampin were highly bactericidal; more than 90% of the inoculum was killed within 8 h.

Therapeutic efficacy of teicoplanin in experimental enterococcal endocarditis

The antimicrobial activities of teicoplanin and ampicillin, alone and in combination with gentamicin, were compared in experimental Streptococcus faecalis endocarditis. Bacterial titers in vegetations of rabbits treated with teicoplanin were significantly lower than those of untreated controls (P less than 0.01) and were equivalent to titers in ampicillin-treated animals. Gentamicin increased the activities of both drugs to a comparable degree.