In vitro activities of ertapenem (MK-0826) against recent clinical bacteria collected in Europe and Australia

Comparative in vitro activity and the inoculum effect of ertapenem against Enterobacteriaceae resistant to extended-spectrum cephalosporins

The in vitro activity and the inoculum effect of ertapenem were evaluated against a total of 70 Enterobacteriaceae isolates resistant to extended-spectrum cephalosporins. The extended-spectrum beta-lactamase phenotypic confirmatory disk diffusion test was performed and AmpC-inducible species were detected using cefoxitin/cefotaxime disk antagonism tests. beta-Lactamases were characterised by isoelectric focusing and TEM-specific polymerase chain reaction. Minimum inhibitory concentrations (MICs) were determined by the National Committee for Clinical Laboratory Standards agar dilution method. Ertapenem showed excellent activity against almost all isolates tested, with MIC(50) and MIC(90) values of 0.03 mg/L and 0.12 mg/L, respectively. When the inoculum was increased 100-fold, susceptibility decreased from 98.6% to 65.7% for cefepime and from 75.7% to 54.3% for piperacillin/tazobactam, without changing for ertapenem. The data from this study suggest that this new carbapenem may be useful for treating mixed infections involving Enterobacteriaceae isolates resistant to third-generation cephalosporins.

Evaluation of the in vitro activity of ertapenem and nine other comparator agents against 337 anaerobic bacteria

Ertapenem activity in vitro was compared with that of nine reference antibiotics against 337 anaerobes by determining minimal inhibition concentrations (MICs). Amongst 246 Gram-negative anaerobes, 4, 8, 3, 4, 7, 2 and 52 strains showed resistance to ertapenem, amoxicillin/clavulanic acid, ticarcillin/clavulanic acid, piperacillin/tazobactam, cefoxitin, imipenem and clindamycin, respectively, and all strains were inhibited by metronidazole. Ertapenem MIC(50) values were 0.5, 0.25, 0.06 and <or=0.03mg/L for the Bacteroides fragilis group, Prevotella spp., fusobacteria and Gram-positive cocci, respectively. Overall resistance rates were 2.1%, 51.3%, 2.4%, 1.2%, 1.5%, 7.1%, 0.6%, 22% and 1.5% for ertapenem, amoxicillin, amoxicillin/clavulanic acid, ticarcillin/clavulanic acid, piperacillin/tazobactam, cefoxitin, imipenem, clindamycin and metronidazole, respectively. Ertapenem showed a broad spectrum and good activity against anaerobes.

Multicenter antimicrobial susceptibility survey of gram-negative bacteria isolated from patients with community-acquired infections in the People's Republic of China

A survey of 2,099 gram-negative bacilli from community infections at seven centers in the People's Republic of China is reported. The rates of resistance of 1,615 isolates of the family Enterobacteriaceae were as follows: 40.8% for ciprofloxacin, 32.2% for gentamicin, 0% for imipenem or ertapenem, and 14.7% for cefotaxime. The rates of extended-spectrum beta-lactamase production were 16% for Escherichia coli and 17% for Klebsiella.

Ertapenem: a review of its use in the treatment of bacterial infections

The Group 1, 1 beta-methyl carbapenem ertapenem (Invanz) is approved for parenteral use in patients with complicated intra-abdominal infection (cIAI), community-acquired pneumonia (CAP) and acute pelvic infection caused by susceptible strains of certain designated organisms in both the US and the EU. Additional approved indications in the US include complicated skin and skin structure infection (cSSSI) and complicated urinary tract infection (cUTI). Ertapenem is approved for use in adults in both the US and the EU and in paediatric patients aged >or=3 months in the US. Ertapenem has a broad spectrum of in vitro activity against Gram-negative pathogens, including extended-spectrum beta-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae, Gram-positive pathogens and anaerobic pathogens. It has similar efficacy to comparator antibacterials such as piperacillin/tazobactam in cSSSI (including diabetic foot infection), cIAI and acute pelvic infection and ceftriaxone with or without metronidazole in cIAI, cUTI and CAP. The drug has also shown efficacy in the treatment of paediatric patients with complicated community-acquired bacterial infections. Ertapenem has a convenient once-daily administration schedule and is generally well tolerated. Thus, ertapenem is an important option for the empirical treatment of complicated community-acquired bacterial infections in hospitalised patients.

Quantification of the carbapenem antibiotic ertapenem in human plasma by a validated liquid chromatography–mass spectrometry method

BACKGROUND

Ertapenem (Invanz) is a newly developed carbapenem beta-lactam antibiotic. LC-MS is the method of choice for therapeutic drug monitoring (TDM) of a variety of drugs including antibiotics. No validated LC-MS method for ertapenem quantification is described in the literature so far.

METHODS

A rapid and robust LC-MS quantification method for ertapenem was developed and validated for clinical routine application in plasma samples. After immediate stabilisation with MES buffer (pH 6.5), samples were prepared for LC-MS analysis using simple protein precipitation. LC-MS coupling was realised by the use of a Phenomenex Synergi 4micro Polar-RP A80 Mercury LC column (10 x 2.0 mm) in combination with a Single-MS (Agilent 1100 LC-MSD SL) operating in negative selected ion monitoring (SIM) detection mode with ceftazidime as internal standard for adequate selective and sensitive analysis.

RESULTS

LC-MS method validation by means of determination of limit of detection (LOD 0.1 microg mL-1), lower limit of quantification (LLOQ 1 microg mL-1), linearity (0.1-50 microg mL-1), recovery (> 90%), intra- and inter-day precision (RSD < 10%), accuracy (> 90%), inter-subject variability (< 10% at LLOQ), drug stability in plasma (> 3 months) and in post-extracted samples (> 99% for 24 h), and matrix effects (process efficiency > 90%) showed excellent performance parameters considering Guidance for Industry - Bioanalytical Method Validation.

CONCLUSION

This method is perfectly appropriate for routine quantification of ertapenem and possibly other polar carbapenem beta-lactam antibiotics.

Assay of ertapenem in human serum by high-performance liquid chromatography

Ertapenem is a new carbapenem with a broad spectrum of activity and an extended half-life, permitting once daily administration. Although high-performance liquid chromatography (HPLC) methods have been described for ertapenem, these are complex and involve column switching and thus this type of assay may not suitable for use in routine clinical microbiology laboratories. In this study we report a rapid, straightforward HPLC method for the detection of ertapenem in human serum.

Pharmacodynamics of moxifloxacin against anaerobes studied in an in vitro pharmacokinetic model

The antibacterial effects of moxifloxacin against Bacteroides fragilis, Clostridium perfringens, and gram-positive anaerobic cocci (GPAC) were studied in an in vitro pharmacokinetic model. Initially, a dose-ranging study with area under the concentration-time curve (AUC)/MIC ratios of 6.7 to 890 was used to investigate the effect of anaerobic conditions on the AUC/MIC antibacterial effect (ABE) relationship with Escherichia coli. The AUC/MIC ratios for 50% and 90% effects, using a log CFU drop at 24 h as the antibacterial effect measure, were 34 and 59, respectively, aerobic and 54 and 96, respectively, anaerobic. These values are not significantly different. Dose ranging at AUC/MIC ratios of 9 to 216 against the anaerobes indicated a differing AUC/MIC ABE pattern, and the AUC/MICs for 50% and 90% effects were lower: for B. fragilis, they were 10.5 and 25.7, respectively; for C. perfringens, they were 8.6 and 16.2; and for GPAC, they were 7.3 and 17.4. The maximum-effect log drops were as follows: for B. fragilis, -3.2 +/- 0.2 logs; for C. perfringens, -3.7 +/- 0.1 logs; and for GPAC, -2.5 +/- 0.1 logs. Although the anaerobes were not eradicated, there was no emergence of resistance. Comparison of the ABE of moxifloxacin to that of ertapenem against B. fragilis indicated that moxifloxacin was superior at 24 h and 48 h. In contrast, ertapenem was superior to moxifloxacin against GPAC at 24 h and 48 h and against C. perfringens at 48 h. Both drugs performed equivalently against C. perfringens at 24 h. Monte Carlo simulations using human serum AUC data and an AUC/MIC anaerobe target of 7.5 suggests a >90% target achievement at MICs of <2 mg/liter. This divides the B. fragilis wild-type MIC distribution. The pharmacodynamic properties of moxifloxacin against anaerobes are different than those against aerobic species. The clinical implications of these differences need further exploration.

Multicentre survey of the in-vitro activity of seven antimicrobial agents, including ertapenem, against recently isolated Gram-negative anaerobic bacteria in Greece

The in-vitro activities of penicillin, ticarcillin-clavulanic acid, cefoxitin, imipenem, ertapenem, metronidazole and clindamycin were evaluated against 138 Gram-negative anaerobic isolates (82 Bacteroides fragilis group, 17 non-fragilis Bacteroides spp., 31 Prevotella spp., four Fusobacterium spp., two Veillonella spp., one Porphyromonas sp. and one Tissierella praeacuta) collected from six general hospitals in Athens, Greece. Overall rates of non-susceptibility (both resistant and intermediately-resistant) to penicillin and ticarcillin-clavulanic acid were 81.8% and 2.3%, respectively. The rates of non-susceptibility to cefoxitin and clindamycin were 30.3% and 31.1%, respectively, and that for metronidazole was 4.3% (four Prevotella spp. isolates, one Porphyromonas sp. isolate and one B. fragilis isolate). Only the single B. fragilis isolate was nim-positive by PCR. Only one B. fragilis isolate was resistant to both carbapenems tested, while six more Bacteroides spp. isolates were imipenem-susceptible and ertapenem-non-susceptible. The MIC range, MIC(50) and MIC(90) values were comparable for imipenem and ertapenem, although ertapenem MIC(90)s were one or two two-fold dilutions higher.

Pharmacokinetics and pharmacodynamics of imipenem during continuous renal replacement therapy in critically ill patients

The pharmacokinetics of imipenem were studied in adult intensive care unit (ICU) patients during continuous venovenous hemofiltration (CVVH; n=6 patients) or hemodiafiltration (CVVHDF; n=6 patients). Patients (mean+/-standard deviation age, 50.9+/-15.9 years; weight, 98.5+/-15.9 kg) received imipenem at 0.5 g every 8 to 12 h (total daily doses of 1 to 1.5 g/day) by intravenous infusion over 30 min. Pre- and postmembrane blood (plasma) and corresponding ultrafiltrate or dialysate samples were collected 1, 2, 4, and 8 or 12 h (depending on dosing interval) after completion of the drug infusion. Drug concentrations were measured using validated high-performance liquid chromatography methods. Mean systemic clearance (CL(S)) and elimination half-life (t1/2) of imipenem were 145+/-18 ml/min and 2.7+/-1.3 h during CVVH versus 178+/-18 ml/min and 2.6+/-1.6 h during CVVHDF, respectively. Imipenem clearance was substantially increased during both CVVH and CVVHDF, with membrane clearance representing 25% and 32% of CL(S), respectively. The results of this study indicate that CVVH and CVVHDF contribute to imipenem clearance to a greater degree than previously reported. Imipenem doses of 1.0 g/day appear to achieve concentrations adequate to treat most common gram-negative pathogens (MIC up to 2 microg/ml) during CVVH or CVVHDF, but doses of 2.0 g/day or more may be required to adequately treat and prevent resistance in pathogens with higher MICs (MIC=4 to 8 microg/ml). Higher doses should only be used after consideration of potential central nervous system toxicities or other risks of therapy in these severely ill patients.

Ertapenem: review of a new carbapenem

The carbapenems are beta-lactam-type antibiotics with an exceptionally broad spectrum of activity. Ertapenem is a new carbapenem developed to address the pharmacokinetic shortcomings (short half-life) of imipenem and meropenem. Ertapenem shares similar structural features with meropenem, including its stability to dehydropeptidase-1, allowing it to be administered without a dehydropeptidase-1 inhibitor. Ertapenem, like imipenem and meropenem, demonstrates broad-spectrum antimicrobial activity against many Gram-positive and -negative aerobes and anaerobes and is resistant to nearly all beta-lactamases, including extended-spectrum beta-lactamases and AmpCs. However, it differs from both imipenem and meropenem in demonstrating limited activity against Enterococcusspp., Pseudomonasaeruginosa and other nonfermentative Gram-negative bacteria commonly associated with nosocomial infections. The extensive protein binding of ertapenem extends the half-life and allows for once-daily dosing. Prospective, multicenter, randomized, double-blind, comparative clinical studies demonstrate similar clinical efficacy of ertapenem compared with other agents. Clinical trials of complicated intra-abdominal infection, acute pelvic infection, complicated skin and soft-structure infection, community-acquired pneumonia and complicated urinary tract infections demonstrated that ertapenem has equivalent efficacy and safety compared with ceftriaxone and piperacillin/tazobactam. Ertapenem is a promising new carbapenem with excellent efficacy and safety for the treatment of a variety of community-acquired infections. It also appears to be of great value as an outpatient parenteral antimicrobial therapy.

Pharmacodynamic profile of ertapenem against Klebsiella pneumoniae and Escherichia coli in a murine thigh model

The pharmacodynamic profile of ertapenem was evaluated in a neutropenic mouse thigh infection model. Extended-spectrum beta-lactamase (ESBL)-positive and ESBL-negative clinical strains of Escherichia coli and Klebsiella pneumoniae were studied. MICs ranged from 0.0078 to 0.06 microg/ml with standard inoculum tests. Ertapenem doses were administered once to five times daily to achieve various exposures, reported as the percentage of the dosing interval that the concentration of free ertapenem was in excess of the MIC (%T>MIC(free)). Mean values for the static exposure and 80% maximally effective exposure (ED(80)) were 19% (range, 2 to 38%) and 33% (range, 13 to 65%) T>MIC(free), respectively. Differences in exposure requirements based on the presence of an ESBL resistance mechanism or bacterial species were not evident. In addition, experiments using a 100-fold higher inoculum did not decrease the magnitude of the reduction in bacterial density from baseline achieved compared to lower-inoculum studies. The pharmacodynamic parameter of %T>MIC(free) correlated well with bactericidal activity for all isolates, and the static and ED(80) exposures are consistent with those reported previously for carbapenems.

Selectivity of ertapenem for Pseudomonas aeruginosa mutants cross-resistant to other carbapenems

OBJECTIVES

Ertapenem and other carbapenems will be used increasingly, as extended-spectrum beta-lactamases become more prevalent even among community-acquired pathogens. There is, however, concern that this use will select for resistances to imipenem and meropenem in nosocomial pathogens, notably Pseudomonas aeruginosa, and we investigated the validity of this concern.

METHODS

Single-step selection experiments were performed by plating P. aeruginosa cultures on to agar containing doubling dilutions of ertapenem. MIC patterns, outer membrane protein profiles and the effects of efflux inhibitors were examined for selected mutants.

RESULTS

At 2-8 x MIC, ertapenem selected (i) for OprD(-) mutants of P. aeruginosa, with cross-resistance only to carbapenems, (ii) for putative efflux types with broader cross-resistance, and also (iii) for various less familiar phenotypes. Efflux mutants were predominantly, but not exclusively, selected from carbenicillin-hypersusceptible strains and OprD(-) mutants largely from strains with normal levels of carbenicillin susceptibility. Whilst these data indicate potential cross-selectivity, they must be set against the observation that 20% serum raised the ertapenem MICs, and the drug concentrations needed for mutant selection, by over four-fold, reflecting the compound's strong protein binding. Since, following a 1 g intravenous dose the free ertapenem concentration in the serum falls below 4 mg/L--corresponding to the lower of two MIC(50) estimates--within 4 h (17% of the dosage interval) selectivity in vivo should be minimized.

CONCLUSIONS

Whilst ertapenem can select for P. aeruginosa mutants with cross-resistance to imipenem and ertapenem in vitro, this selectivity should be minimal under clinical conditions.

Actividad de ertapenem y otros 19 antimicrobianos frente a Streptococcus pneumoniae y Haemophilus influenzae aislados del tracto respiratorio resistentes a betalactámicos

INTRODUCTION

Ertapenem is a new carbapenem with a long half-life that has a broad spectrum of action against Gram-positive and Gram-negative bacteria. Although, clinically indicated for the treatment of the polymicrobial abdominal infection, other uses are possible, due to the broad spectrum of action of this antimicrobial agent.

OBJECTIVE

The purpose of this study was to examine the susceptibility to ertapenem of Streptococcus pneumoniae and Haemophilus influenzae strains with resistance to beta-lactam antibiotics.

METHODS

The study comprised 105 S. pneumoniae strains with a reduced susceptibility to penicillin G, 86 S. pneumoniae strains resistant to penicillin, and 100 H. influenzae strains resistant to ampicillin isolated fron clinical respiratory samples collected in the 21 participating microbiology laboratories. Susceptibility to antimicrobials was tested using an agar dilution method.

RESULTS

The S. pneumoniae strains with intermediate resistance to penicillin were highly susceptible to carbapenems, with MIC90 of 0,25 and 0,5 mg/l for imipenem and ertapenem, respectively. Among the penicillin-resistant strains the MIC90 values for imipenem and ertapenem were 1 and 2 mg/l respectively. Carbapenems were very active against the whole group of H. influenzae strains, particullary ertapenem, which inhibited 90% of the series at a concentration of 0,12 mg/l.

CONCLUSIONS

Ertapenem is a powerful agent against the most common respiratory bacterial pathogens, including those with resistance mechanisms effective against other compouunds. Few strains can currently be considered resistant to this carbapenem, which is at least comparable to imipenem, cefotaxime or the modern fluorquinolones. Such performance, and its favorable pharmacokinetic characteristics, make ertapenem an interesting option for the treatment of respiratory tract infections.

Beta-lactam antibiotics: newer formulations and newer agents

beta-Lactam antibiotics share a common structure and mechanism of action, although they differ in their spectrum of antimicrobial activity and utility in treating different infections. The current classes include the penicillins, the penicillinase-resistant penicillins, the extended- spectrum penicillins, the cephalosporins, the carbapenems, and the monobactams. This article discusses some of the newest beta-lactams available for use in the United States: ertapenem, cefditoren, and cefepime. A new formulation of amoxicillin-clavulanate, which contains higher doses of amoxicillin, is also discussed.

Ertapenem pharmacokinetics and impact on intestinal microflora, in comparison to those of ceftriaxone, after multiple dosing in male and female volunteers

The pharmacokinetics of ertapenem and ceftriaxone were investigated in an open, randomized, two-period crossover study after single- and multiple-dose administration in 10 healthy volunteers (five women and five men). Both antibiotics were administered intravenously once daily for 7 days at dosages of 1 g (ertapenem) and 2 g (ceftriaxone). The concentrations of the antibiotics in serum and urine were quantified by the agar well diffusion method bioassay and, in addition, for ertapenem only, by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). For ertapenem the maximum concentration of the drug in plasma (C(max)) was 256 mg/liter, the half-life was 20.7 h, and the area under the plasma concentration-time curve (AUC) was 830 mg. h/liter. The concentrations in fecal samples were (mean value) 37.2 and 32.7 mg/kg on day 4 and day 8, respectively. Ceftriaxone exhibited a mean C(max) of 315 mg/liter, a half-life of 7.6 h, and an AUC of 1,556 mg. h/liter. The mean concentrations in fecal samples were 153 and 258 mg/kg on day 4 and day 8, respectively. No accumulation of ertapenem or ceftriaxone was detected at steady state. A slightly but significantly decreased AUC for ertapenem was detected for the female volunteers. No serious adverse event was observed. Both antibiotics induced a marked decrease in the anaerobic microflora (4-log-unit decreases in lactobacilli, bifidobacteria, clostridia, and bacteroides) and Escherichia coli, whereas the number of enterococci increased (4 log units). A slight overgrowth of yeasts was observed with both regimens. In all cases the microflora returned to normal levels on days 21 to 35.

Ertapenem as initial antimicrobial monotherapy for patients with chronic obstructive pulmonary disease hospitalized with typical community-acquired pneumonia

This report describes a post-hoc analysis of two large studies of typical community-acquired pneumonia (CAP) in hospitalized patients, focusing on demographics, disease characteristics, and outcome in patients with and without chronic obstructive pulmonary disease (COPD). In both studies, ertapenem 1 g IV daily was compared with ceftriaxone 1 g IV daily as initial antimicrobial therapy. Clinically improving patients could be switched to oral antibiotic therapy after 3 days. Of the 857 patients treated in both studies, 264 (31%) had COPD. The proportions of patients who were male, were >/=65 years of age, had a Pneumonia Severity Index of IV/V, or had Haemophilus influenzae isolated in a baseline culture were higher in patients with COPD. Streptococcus pneumoniae was the most common pathogen both in patients with and without COPD. Clinical response rates in assessable patients 7-14 days after completion of therapy for the combined treatment groups were 90% (187/208) for patients with COPD and 93% (424/456) for those without COPD (odds ratio 0.7 [95% CI, 0.4-1.2], P = 0.17). Of assessable COPD patients, 109/121 (90%) treated with ertapenem and 78/87 (90%) treated with ceftriaxone achieved a favorable clinical response (odds ratio 1.0 [95% CI, 0.6-1.8], P = 0.94). The outcome in patients with or without COPD was similar regardless of therapy. In patients with COPD as well as in the overall study population, the efficacy of ertapenem as initial antimicrobial monotherapy for patients with serious typical community-acquired pneumonia was comparable to that of ceftriaxone.

Antibiotic susceptibility in neonatal invasive isolates of Streptococcus agalactiae in a 2-year nationwide surveillance study in Germany

The antimicrobial susceptibility of 296 invasive neonatal group B streptococcus isolates from a nationwide 2-year surveillance study in Germany was investigated. All isolates were susceptible to beta-lactams, linezolid, quinupristin-dalfopristin, and vancomycin. Erythromycin and clindamycin resistance was found in 10.1 and 5.7%, respectively. The ermB, ermTR, or mefA gene was detected in all but one of the erythromycin-resistant isolates.

Pharmacodynamic modeling of carbapenems andfluoroquinolones against bacteria that produce extended-spectrum beta-lactamases

BACKGROUND

Bacteria that produce extended-spectrum beta-lactamases (ESBLs) are resistant to penicillins,cephalosporins, and monobactams. The results of clinical studies suggest that the carbapenems imipenem and meropenem may be effective against bacteria that produce ESBLs, although it is not known whether the new once-daily carbapenem ertapenem or the fluoroquinolones are useful against infections caused by ESBL-producing bacteria.

OBJECTIVE

The present study compared the simulated pharmacodynamics of the carbapenems imipenem,meropenem, and ertapenem; the simulated pharmacodynamics of the fluoroquinolones levofloxacin, gatifloxacin, and ciprofloxacin with those of the carbapenems; and the simulated pharmacodynamics of levofloxacin 750 mg with those of levofloxacin 500 mg, all against gram-negative isolates that did and did not produce ESBLs

METHODS

Pharmacokinetic data were obtained from studies in healthy humans. Minimum inhibitory concentrationsMICs) for bacteria that did and did not produce ESBLs were determined in triplicate using broth-microdilution techniques as recommended by National Committee for Clinical Laboratory Standards guidelines. Monte Carlo simulation was used to construct pharmacodynamic models for imipenem, meropenem, ertapenem, levofloxacin, gatifloxacin, and ciprofloxacin. Pharmacodynamic measures of interest were the probability of the free concentration remaining above the MIC >-40% of the time (T>MIC > or =40%) for carbapenems and the likelihood of achieving a free AUC:MIC ratio > or =125 for fluoroquinolones.

RESULTS

MICs were determined for 39 isolates that produced ESBLs and 45 isolates that did not Bacteria that did not produce ESBLs were > or =93% susceptible to all carbapenems and fluoroquinolones tested. Among bacteria that produced ESBLs, rates of susceptibility to the specific agents were as follows: imipenem, 100%; meropenem, 97%; ertapenem, 87%; levofloxacin, 54%; gatifloxacin, 44%; and ciprofloxacin, 36%. In the pharmacodynamic models, imipenem and meropenem had an equal likelihood of achieving a free T>MIC > or =40% against bacteria that produced ESBLs (> or =97%) and bacteria that did not produce ESBLs (> or =98%). In contrast, the likelihood of ertapenem achieving a free T>MIC > or =40% was lower against bacteria that produced ESBLs (78%) than against bacteria that did not produce ESBLs (94%). Similarly, the fluoroquinolones were less likely to achieve a free AUC:MIC ratio > or =125 against bacteria that produced ESBLs (2%-13%) than against bacteria that did not produce ESBLs (85%-91%).

CONCLUSIONS

Carbapenems had superior in vitro activity against bacteria that produced ESBLs compared with fluoroquinolones. Pharmacodynamic modeling based on local ESBL-producing isolates and pharmacokinetic data from healthy humans indicated that imipenem and meropenem may have a greater likelihood of achieving pharmacodynamic targets against bacteria that produce ESBLs than ertapenem or fluoroquinolones.

Role of beta-lactamases and porins in resistance to ertapenem and other beta-lactams in Klebsiella pneumoniae

High-level resistance to ertapenem was produced by beta-lactamases of groups 1, 2f, and 3 in a strain of Klebsiella pneumoniae deficient in Omp35 and Omp36. From a wild-type strain producing ACT-1 beta-lactamase, ertapenem-resistant mutants for which the ertapenem MICs were up to 128 microg/ml and expression of outer membrane proteins was diminished could be selected.

Ertapenem: a review of its use in the management of bacterial infections

Ertapenem, a carbapenem antibacterial, has in vitro activity against many Gram- negative (including Enterobacteriaceae) and Gram-positive aerobic and anaerobic bacteria that are commonly associated with various infections.Once-daily parenteral (intravenous or intramuscular) ertapenem 1g was as effective as comparator antimicrobial agents (piperacillin/tazobactam or ceftriaxone +/- metronidazole) in patients with bacterial infections in randomised, double-blind, multicentre clinical trials. Response rates with ertapenem were 84% and 87% (combined microbiological and clinical) in patients with complicated intra-abdominal infections (CIAI), 82% (clinical) in patients with complicated skin and skin structure infections (CSSSI), 86% and 92% (microbiological) in patients with complicated urinary tract infections (CUTI), 92% (clinical) in patients with community-acquired pneumonia (CAP) associated with typical pathogens and 94% (clinical) in patients with acute pelvic infection. Respective response rates were statistically equivalent to those with comparators (81-94%). The efficacy of ertapenem was equivalent to that of piperacillin/tazobactam in patients infected with Enterobacteriaceae or anaerobes and to ceftriaxone in patients infected with Enterobacteriaceae. Ertapenem was generally well tolerated by patients with bacterial infections, with most adverse events being mild to moderate in severity. The most common ertapenem-associated adverse events were diarrhoea, infused vein complication, nausea, headache, vaginitis in females, phlebitis and/or thrombophlebitis and vomiting.

CONCLUSION

Ertapenem is a broad-spectrum parenteral antibiotic with activity against many Gram-negative (including Enterobacteriaceae) and Gram-positive aerobic and anaerobic bacteria and is suitable for once-daily administration. Ertapenem has a role in the treatment of CAP associated with typical respiratory pathogens and is of particular value in the treatment of polymicrobial infections (such as CIAI, CSSSI, CUTI and acute pelvic infections), especially where Enterobacteriaceae and anaerobic bacteria are involved.

Evaluation of outpatient treatment with ertapenem in a double blind controlled clinical trial of complicated skin/skin structure infections

OBJECTIVES

The patient characteristics and the efficacy and safety of ertapenem 1 g once daily vs. piperacillin-tazobactam 13.5 g divided Q6H were examined in patients who received outpatient parenteral antimicrobial therapy (OPAT) during a clinical trial of complicated skin/skin structure infections.

METHODS

The population analyzed included 363 patients treated at US sites in a large randomized double-blind study.

RESULTS

In this analysis, 146 (40%) patients at 19 (66%) sites were managed by OPAT. A lower proportion of treated patients who received OPAT had severe infection (12% vs. 20%, P=0.03). In evaluable patients managed by OPAT, 45 (83.3%) of 54 treated with ertapenem and 41 (82.0%) of 50 treated with piperacillin-tazobactam were cured at the test of cure assessment 10-21 days post-therapy (OR 1.2 (95% CI, 0.4-3.2), P=0.78). The safety profile of both drugs was generally similar; diarrhoea was the most common adverse event in both groups.

CONCLUSIONS

In this trial of complicated skin/skin structure infection, OPAT was commonly used by US investigators. Among patients who received OPAT, ertapenem 1 g daily was as effective as piperacillin-tazobactam 3.375 g Q6H.

Ertapenem Therapy for Community-Acquired Pneumonia in the Elderly

OBJECTIVES

To compare the efficacy and safety of ertapenem, 1 g once a day, with ceftriaxone, 1 g once a day, for treatment of the subgroup of patients aged 65 and older with community-acquired pneumonia (CAP) requiring parenteral therapy.

DESIGN

Combined data from patients aged 65 and older in two randomized, double-blind clinical trials.

SETTING

Eighty international centers.

PARTICIPANTS

Eight hundred fifty-seven treated patients, of whom 351 were aged 65 and older.

INTERVENTIONS

Intravenous or intramuscular ertapenem or ceftriaxone with the option to switch to oral amoxicillin-clavulanate after at least 3 days of parenteral therapy.

MEASUREMENTS

Clinical efficacy was assessed at completion of parenteral therapy and 7 to 14 days after all therapy had been completed (test of cure (TOC) assessment). Bacterial eradication was assessed at the TOC visit. Safety was assessed daily during study therapy and for 14 days thereafter.

RESULTS

One hundred forty-eight clinically evaluable patients aged 65 and older were treated with ertapenem and 125 with ceftriaxone. Pathogens were identified in 157 (57.5%) patients (the most common being Streptococcus pneumoniae), most of which were penicillin-susceptible. Clinical cure rates were 95.9% for patients in the ertapenem group and 92.7% for patients in the ceftriaxone group at completion of parenteral therapy and 93.9% and 90.4%, respectively, at the TOC assessment. Overall bacterial eradication rates were 92.8% (77 of 83) for patients treated with ertapenem and 93.2% (69 of 74) for those treated with ceftriaxone. The most common drug-related adverse experiences in both treatment groups were diarrhea and mild to moderate elevation of serum aminotransferase levels.

CONCLUSION

Ertapenem 1 g once a day was highly effective for treatment of elderly patients with CAP requiring parenteral therapy and was as effective as ceftriaxone. Ertapenem was generally well tolerated, with an overall safety profile similar to ceftriaxone.

In vitro activity of ertapenem against anaerobes isolated from the respiratory tract

Ertapenem is a novel parenteral carbapenem with a long serum half-life. Its spectrum of activity is similar to that of imipenem and meropenem against Gram-positive bacteria, Enterobacteriaceae and fastidious Gram-negative bacteria but it is less active against Pseudomonas aeruginosa and Acinetobacter spp. Several studies were performed in the United States but only one European study has shown that ertapenem has an excellent activity against anaerobes. The objectives of the present study were to test the activity of ertapenem against anaerobes isolated prospectively from the lower and upper respiratory tracts, and to compare their susceptibility with that of anaerobic isolates from other body sites. Fifty-three isolates from the respiratory tract, as well as 50 isolates from various other body sites were tested with E-tests against six antibiotics. For respiratory isolates and for isolates from other sites, MIC 90 values (mg/l) were, respectively, >32 and >32 for penicillin, 0.38 and 0.75 for amoxicillin/clavulanate, 48 and >256 for ceftriaxone, 0.12 and 0.75 for ertapenem, 12 and >256 for clindamycin and 2 and 12 for moxifloxacin. The higher susceptibility of respiratory tract isolates was mainly due to the different distribution of isolated species: only three respiratory isolates but 22 other isolates belonged to the Bacteroides fragilis group. This study confirms the excellent anti-anaerobic activity of ertapenem against anaerobic isolates from the respiratory tract.

Ertapenem versus piperacillin-tazobactam for treatment of mixed anaerobic complicated intra-abdominal, complicated skin and skin structure, and acute pelvic infections

BACKGROUND

Anaerobes are an important component of many serious, deep tissue infections, especially complicated intra-abdominal (IAI), complicated skin and skin structure (SSSI), and acute pelvic (PI) infections. This study compares the efficacy of ertapenem, 1 g once a day, in the treatment of adults with anaerobic IAI, SSSI, and PI to piperacillin-tazobactam, 3.375 g every 6 hours.

METHODS

Three randomized, double-blind trials comparing ertapenem to piperacillin-tazobactam for treatment of IAI, SSSI, and PI were conducted. This subgroup analysis included 623 patients, whose baseline culture grew one or more anaerobic pathogens, from these three studies.

RESULTS

Anaerobes most commonly isolated were Bacteroides fragilis group (IAI) and peptostreptococci (SSSI and PI). The median duration of ertapenem and piperacillin-tazobactam therapy, respectively, in these subgroups was 6 and 7 days for IAI, 7 and 8 days for SSSI, and 4 and 5 days for PI. Cure rates for all evaluable patients with anaerobic infection were 89.3% (242/271) for ertapenem and 85.9% (220/256) for piperacillin-tazobactam (95% CI for the difference, adjusting for infection, -2.6% to 9.3%), indicating that the two treatments were equivalent. Cure rates by infection, for ertapenem and piperacillin-tazobactam, respectively, were as follows: IAI, 86.4% (133/154) and 82.4% (117/142); SSSI, 84.4% (27/32) and 82.4% (28/34); PI, 96.5% (82/85) and 93.8% (75/80). The frequency and severity of drug-related adverse experiences were comparable in both treatment groups.

CONCLUSION

In this subgroup analysis, ertapenem was as effective as piperacillin-tazobactam for treatment of adults with moderate to severe anaerobic IAI, SSSI, and PI, was generally well tolerated, and had a similar safety profile.

Ertapenem versus piperacillin/tazobactam in the treatment of complicated intraabdominal infections: results of a double-blind, randomized comparative phase III trial

OBJECTIVE

To examine the clinical efficacy and safety of ertapenem, a novel beta-lactam agent with wide activity against common pathogens encountered in intraabdominal infection.

SUMMARY BACKGROUND DATA

Ertapenem has a pharmacokinetic profile and antimicrobial spectrum that support the potential for use as a once-a-day agent for the treatment of common mixed aerobic and anaerobic infections. METHODS This prospective, randomized, controlled, and double-blind trial was conducted to compare the safety and efficacy of ertapenem with piperacillin/tazobactam as therapy following adequate surgical management of complicated intraabdominal infections.

RESULTS

Six hundred thirty-three patients were included in the modified intent-to-treat population, with 396 meeting all criteria for the evaluable population. Patients with a wide range of infections were enrolled; perforated or abscessed appendicitis was most common (approximately 60% in microbiologically evaluable population). A prospective, expert panel review was conducted to assess the adequacy of surgical source control in patients who were failures as a component of evaluability. For the modified intent-to-treat groups, 245 of 311 patients treated with ertapenem (79.3%) were cured, as were 232 of 304 (76.2) treated with piperacillin/tazobactam. One hundred seventy-six of 203 microbiologically evaluable patients treated with ertapenem (86.7%) were cured, as were 157 of the 193 (81.2%) treated with piperacillin/tazobactam.

CONCLUSIONS

In this study, the efficacy of ertapenem 1 g once a day was equivalent to piperacillin/tazobactam 3.375 g every 6 hours in the treatment of a range of intraabdominal infections. Ertapenem was generally well tolerated and had a similar safety and tolerability profile to piperacillin/tazobactam. A formal process for review of adequacy of source control was found to be of benefit. The results of this trial suggest that ertapenem may be a useful option that could eliminate the need for combination and/or multidosed antibiotic regimens for the empiric treatment of intraabdominal infections.

Ertapenem once a day versus piperacillin-tazobactam every 6 hours for treatment of acute pelvic infections: a prospective, multicenter, randomized, double-blind study

OBJECTIVE

To compare ertapenem therapy with piperacillin-tazobactam therapy for the management of acute pelvic infections.

METHODS

In a multicenter, double-blind study, 412 women with acute pelvic infection were assigned to one of two strata, namely obstetric/postpartum infection or gynecologic/postoperative infection, and were then randomized to ertapenem, 1 g once a day, or piperacillin-tazobactam, 3.375 g every 6 hours, both administered intravenously.

RESULTS

In total, 163 patients in the ertapenem group and 153 patients in the piperacillin-tazobactam group were clinically evaluable. The median duration of therapy was 4.0 days in both treatment groups. The most common single pathogen was Escherichia coli. At the primary efficacy endpoint 2-4 weeks post therapy, 93.9% of patients who received ertapenem and 91.5% of those who received piperacillin-tazobactam were cured (95% confidence interval for the difference, adjusting for strata, -4% to 8.8%), indicating that cure rates for both treatment groups were equivalent. Cure rates for both treatment groups were also similar when compared by stratum and severity of infection. The frequency and severity of drug-related adverse events were generally similar in both groups.

CONCLUSIONS

In this study, ertapenem was as effective as piperacillin-tazobactam for the treatment of acute pelvic infection, was generally well tolerated, and had an overall safety profile similar to that of piperacillin-tazobactam.

Comparative in vitro activity of ertapenem against bacterial pathogens isolated from patients with lower respiratory tract infections

This study compared the in vitro activity of ertapenem, ceftriaxone, cefepime, ciprofloxacin and amoxicillin-clavulanate against 381 aerobic and facultative bacterial pathogens isolated from 320 patients with acute bacterial exacerbation of chronic bronchitis or community-acquired pneumonia. Streptococcus pneumoniae and Haemophilus influenzae accounted for 54.6% of the isolates. The ertapenem MIC was < or =2 mg/L for 98.4% of isolates and > or =8 mg/L for 1.0% (all methicillin-resistant Staphylococcus aureus). Ertapenem had the most potent activity against Enterobacteriaceae, Moraxella catarrhalis, and methicillin-susceptible S. aureus, and its activity against H. influenzae and H. parainfluenzae, all strains of which were susceptible, was not altered by beta-lactamase production. Only one S. pneumoniae strain, a penicillin-resistant isolate, was resistant to ertapenem. Ertapenem was highly active in vitro against pyogenic bacteria recovered from patients with community-acquired lower respiratory tract infections.

A prospective, randomized, double-blind multicenter comparison of parenteral ertapenem and ceftriaxone for the treatment of hospitalized adults with community-acquired pneumonia

BACKGROUND

Ertapenem is a once-daily parenteral beta-lactam licensed in the United States in November 2001 and in Europe in May 2002.

OBJECTIVE

This study compared the efficacy and safety profiles of ertapenem with those of ceftriaxone for the treatment of hospitalized adult patients with serious community-acquired pneumonia (CAP) requiring parenteral therapy.

METHODS

In this prospective, double-blind (with sponsor blinding), multicenter study, adult patients with CAP were stratified by Pneumonia Severity Index (< or = 3 or > 3) and age (< or = 65 or > 65 years) and randomized (2:1) to receive IV or intramuscular (IM) ertapenem 1 g once daily or IV or IM ceftriaxone 1 g once daily. Investigators could switch patients to an oral antimicrobial agent if clinical improvement was shown after at least 3 days of parenteral therapy.

RESULTS

A total of 364 patients were randomized to treatment: 239 to the ertapenem group and 125 to the ceftriaxone group. Three patients in the ertapenem group and 2 in the ceftriaxone group did not receive study therapy. Of the treated patients, 77.1% (182/236) of patients in the ertapenem group and 75.6% (93/123) in the ceftriaxone group were clinically evaluable. Among clinically evaluable patients, the mean (SD) durations of parenteral and total (parenteral plus optional oral) therapy were 5.5 (2.6) and 11.5 (2.7) days for ertapenem and 5.6 (2.8) and 11.7 (3.0) days for ceftriaxone, respectively. Streptococcus pneumoniae was the most frequently isolated pathogen in both treatment groups. Cure rates were 92.2% for clinically evaluable patients in the ertapenem group and 93.6% for those in the ceftriaxone group (95% CI for the difference, adjusted for stratum, -8.6 to 5.7), fulfilling the criteria for statistical equivalence. At completion of parenteral therapy, 94.7% of patients in the ertapenem group and 95.8% in the ceftriaxone group showed clinical improvement. Infused vein complications (ertapenem, 3.4% [8/236]; ceftriaxone, 7.3% [9/123]) and elevated transaminase levels (ertapenem, 6.3% [13/207]; ceftriaxone, 7.1% [8/113]) were the most common adverse events in both groups.

CONCLUSIONS

In this study of hospitalized adult patients, ertapenem therapy, with an oral switch option, was as effective as ceftriaxone with the same oral switch option for treatment of CAP requiring initial parenteral therapy. The overall safety profiles of the 2 drugs were comparable.

Ertapenem monotherapy versus combination therapy with ceftriaxone plus metronidazole for treatment of complicated intra-abdominal infections in adults

The efficacy and safety of intravenous (IV) ertapenem, 1 and 1.5 g once a day, for treatment of adults with complicated intra-abdominal infection were compared with those of IV ceftriaxone 2 g once a day plus IV metronidazole 500 mg every 8 h. After at least 3 days of IV therapy and satisfactory clinical response, patients could be switched to oral ciprofloxacin plus metronidazole. Fifty-nine patients were randomized to receive ertapenem 1 g and 51 to receive ertapenem 1.5 g; 55 patients were randomized to each comparator group. At the test of cure, 4-6 weeks post therapy, in the 1 g cohort, 84% (26/31) of patients treated with ertapenem and 85% (35/41) with comparator therapy had a favourable clinical and microbiological assessment. Success rates in the 1.5 g cohort were 83% (22/29) and 77% (24/31) in the ertapenem and comparator groups, respectively. Drug-related adverse events were generally similar in both treatment groups. Ertapenem 1 or 1.5 g once a day followed by optional oral therapy appeared similar to combined therapy with ceftriaxone plus metronidazole with the same optional oral switch for treatment of complicated intra-abdominal infections in adults. Although not compared directly in a randomized fashion, the efficacy and safety profiles of ertapenem 1 and 1.5 g appeared comparable. Ertapenem was generally well tolerated and had an overall safety profile similar to ceftriaxone plus metronidazole.

Ertapenem versus ceftriaxone followed by appropriate oral therapy for treatment of complicated urinary tract infections in adults: results of a prospective, randomized, double-blind multicenter study

The efficacy and safety of intravenous (i.v.) ertapenem (1 g once a day) with the option to switch to an oral agent for treatment of adults with complicated urinary tract infections (UTIs) were compared with that of i.v. ceftriaxone (1 g daily) with the same oral switch option in a multicenter, double-blind, prospective, randomized study. At entry, 592 patients were assigned to one of two strata: acute pyelonephritis or other complicated UTI without acute pyelonephritis. After a minimum of 3 days, patients could be switched to an oral antimicrobial agent. A total of 159 patients in the ertapenem group and 171 patients in the ceftriaxone group were microbiologically evaluable. Approximately 95% of patients in each treatment group were switched to oral therapy. The most common pathogens were Escherichia coli and Klebsiella pneumoniae. At the primary efficacy endpoint 5 to 9 days after treatment, 91.8% of patients who received ertapenem and 93.0% of those who received ceftriaxone had a favorable microbiological response (95% confidence interval for the difference, adjusting for strata, -7.6 to 5.1%), indicating that outcomes in the two treatment groups were equivalent. Microbiological success rates for the two treatment groups were similar when compared by stratum and also by severity of infection. The frequency and severity of drug-related adverse events were generally similar in both treatment groups. In this study, ertapenem was as effective as ceftriaxone for the initial treatment of complicated UTIs in adults, was generally well tolerated, and had a similar overall safety profile.

General microbiology and in vitro susceptibility of anaerobes isolated from complicated skin and skin-structure infections in patients enrolled in a comparative trial of ertapenem versus piperacillin-tazobactam

In a recently completed study of once-a-day ertapenem versus piperacillin-tazobactam every 6 h in the treatment of complicated skin and skin-structure infections, 540 patients were randomized in a 1rcolon;1 ratio and assigned to 1 of 2 strata: those with a complicating underlying disease or all others. The most common infections in the study were deep soft-tissue abscess (18.9%), followed by diabetic lower extremity infection (18.1%); 7.0% of these were perineal cellulitis/abscess. With the exception of methicillin-resistant Staphylococcus aureus, almost all of the predominant aerobic pathogens were susceptible to both study drugs. Eighty-seven patients (16%) had >/=1 anaerobe identified in their baseline wound cultures, with a total of 232 anaerobic isolates. Of the 141 anaerobes tested for susceptibility, 97.2% were susceptible to ertapenem and 97.9% to piperacillin-tazobactam. Ertapenem had excellent in vitro activity against the most common aerobic pathogens and almost all anaerobes recovered from patients with infections of the skin and skin structures.

In vitro activity of ertapenem (MK-0826) against multi-drug resistant Streptococcus pneumoniae compared with 13 other antimicrobials

We tested ertapenem (MK-0826), a new carbapenem, and 13 other antimicrobials by microbroth dilution against 102 isolates of Streptococcus pneumoniae, selected to include organisms resistant to a variety of drug classes. Ertapenem MICs ranged from < or =0.008 to 4 mg/l, MIC(50)=0.5 mg/l, and MIC(90)=2 mg/l. Based on MIC(90), ertapenem potency was 4-fold greater than cefuroxime, 2-fold greater than amoxycillin/clavulanate, =penicillin, 2-fold less than meropenem and ceftriaxone, and 4-fold less than imipenem. Other drug classes including macrolides, tetracycline and fluoroquinolones were less potent overall than the carbapenems. Linezolid (MIC(90)=1 mg/l) was the only agent tested for which all isolates were fully susceptible. Activity of ertapenem decreased as MICs to penicillins, cephalosporins, other carbapenems and macrolides increased. Isolates resistant to clindamycin, tetracycline or fluoroquinolones showed no obvious decrease in ertapenem activity when compared with susceptible isolates with the majority of isolates resistant to these drug classes inhibited by ertapenem at concentrations less than 1 mg/l. Ertapenem may prove useful as an alternative to ceftriaxone and other agents in the treatment of community-acquired pneumonia (CAP) due to S. pneumoniae, including infections caused by organisms with reduced susceptibilities to other antimicrobial agents.

Pharmacokinetics and pharmacodynamics of piperacillin/tazobactam when administered by continuous infusion and intermittent dosing

BACKGROUND

Although intermittent bolus dosing is currently the standard of practice for many antimicrobial agents, beta-lactams exhibit time-dependent bacterial killing. Maximizing the time above the minimum inhibitory concentration (MIC) for a pathogen is the best pharmacodynamic predictor of efficacy. Use of a continuous infusion has been advocated for maximizing the time above the MIC compared with intermittent bolus dosing.

OBJECTIVE

This study compared the pharmacokinetics and pharmacodynamics of piperacillin/tazobactam when administered as an intermittent bolus versus a continuous infusion against clinical isolates of Pseudomonas aeruginosa and Klebsiella pneumoniae.

METHODS

Healthy volunteers were randomly assigned to receive piperacillin 3 g/ tazobactam 0.375 g q6h for 24 hours, piperacillin 6 g/tazobactam 0.75 g continuous infusion over 24 hours, and piperacillin 12 g/tazobactam 1.5 g continuous infusion over 24 hours. Five clinical isolates each of P aeruginosa and K pneumoniae were used for pharmacodynamic analyses.

RESULTS

Eleven healthy subjects (7 men, 4 women; mean +/- SD age, 28 +/- 4.7 years) were enrolled. Mean steady-state serum concentrations of piperacillin were 16.0 +/- 5.0 and 37.2 +/- 6.8 microg/mL with piperacillin 6 and 12 g, respectively. Piperacillin/tazobactam 13.5 g continuous infusion (piperacillin 12 g/tazobactam 1.5 g) was significantly more likely to produce a serum inhibitory titer > or = 1:2 against P aeruginosa at 24 hours than either the 6.75 g continuous infusion (piperacillin 6 g/tazobactam 0.75 g) or 3.375 g q6h (piperacillin 3 g/ tazobactam 0.375 g). There were no statistical differences against K pneumoniae between regimens. The median area under the inhibitory activity-time curve (AUIC) for the 13.5 g continuous infusion was higher than that for 3.375 g q6h and the 6.75 g continuous infusion against both P aeruginosa and Kpneumoniae (P < or = 0.007, 13.5 g continuous infusion and 3.375 g q6h vs 6.75 g continuous infusion against K pneumoniae). The percentage of subjects with an AUIC > or = 125 was higher with both 3.375 g q6h and the 13.5 g continuous infusion than with the 6.75 g continuous infusion against P aeruginosa and K pneumoniae (both, P < 0.001 vs 6.75 g continuous infusion against K pneumoniae).

CONCLUSIONS

Piperacillin 12 g/tazobactam 1.5 g continuous infusion consistently resulted in serum concentrations above the breakpoint for Enterobacteriaceae and many of the susceptible strains of P aeruginosa in this study in 11 healthy subjects. Randomized controlled clinical trials are warranted to determine the appropriate dose of piperacillin/tazobactam.

A prospective, multicenter, randomized, double-blind study comparing ertapenem and ceftriaxone followed by appropriate oral therapy for complicated urinary tract infections in adults

OBJECTIVES

To compare the efficacy and safety of ertapenem, a new once-daily parenteral beta-lactam, with that of ceftriaxone for the initial empiric treatment of adults with complicated urinary tract infections (cUTIs).

METHODS

In a multicenter, prospective, double-blind study, patients with cUTIs were stratified as to whether they had acute pyelonephritis or other cUTIs (without pyelonephritis) and randomized to receive ertapenem, 1 g once a day, or ceftriaxone, 1 g once a day. After 3 days, patients with a satisfactory clinical response could be switched to an oral antimicrobial agent.

RESULTS

Of 258 randomized patients, 97 (55.4%) in the ertapenem group and 53 (63.9%) in the ceftriaxone group were evaluated microbiologically. Almost all patients in each treatment group were switched to oral therapy. The mean duration of therapy was similar in both treatment groups: parenteral, approximately 4 days; total, approximately 13 days. The most common pathogen was Escherichia coli. At the primary efficacy endpoint, 5 to 9 days after treatment, 85.6% of patients who received ertapenem and 84.9% who received ceftriaxone had a favorable microbiologic response, indicating that the two treatment groups were equivalent. The frequency and severity of drug-related adverse events were generally similar in both treatment groups.

CONCLUSIONS

In this study, ertapenem was as effective as ceftriaxone for the initial treatment of cUTI in adults, was generally well tolerated, and had a similar safety profile.

Comparative in vitro activities of ertapenem against aerobic and facultative bacterial pathogens from patients with complicated skin and skin structure infections

This study compared the in vitro activities of ertapenem (Merck & Co., Inc.), ceftriaxone, amoxicillin-clavulanate, and piperacillin-tazobactam against 518 aerobic and facultative bacterial pathogens isolated from 340 patients with complicated skin and skin structure infections. Ciprofloxacin was also tested against Gram-negative isolates. Gram-positive cocci accounted for 68.1% of the aerobic bacteria; Staphylococcus aureus was the most common isolate (45.6%). The ertapenem MIC was < or = 2 microg/ml for 80.9% of isolates and > or = 8 microg/ml for 16.2% (including isolates of enterococci, methicillin-resistant S. aureus, Pseudomonas aeruginosa, and other nonfermentative Gram-negative bacteria). Against methicillin-susceptible S. aureus, ertapenem had the most potent activity. Ertapenem was the most active drug against Enterobacteriaceae (100% susceptible), whereas amoxicillin-clavulanate was least active (66% susceptible). Piperacillin-tazobactam was the most active drug against P. aeruginosa (100% susceptible), followed by ciprofloxacin (87% susceptible). In summary, ertapenem was highly active in vitro against many aerobic and facultative bacterial pathogens commonly recovered from patients with complicated skin and skin structure infections.

Use of surrogate antimicrobial agents to predict susceptibility to ertapenem

Broth or agar dilution susceptibility test results for Enterobacteriaceae (11,775 strains), anaerobes (2888 strains), staphylococci (2206 strains), Haemophilus spp. (840 strains), group A streptococci (280 strains), group B streptococci (269 strains), Streptococcus pneumoniae (709 strains), and 160 other streptococci were analyzed to identify surrogate antimicrobial agents to predict susceptibility to ertapenem. Ertapenem MIC interpretive categories approved by the United States FDA were compared to those of imipenem, oxacillin (staphylococci), or penicillin (streptococci). Ertapenem resistance was rare (1.2%) among 8187 consecutively collected clinical isolates of Enterobacteriaceae, including a large proportion of isolates from intensive care units. Absolute categorical agreement between ertapenem and imipenem, and very major (false susceptible) and major errors (false resistant) using imipenem to predict ertapenem results were 97.2%, 0.9%, and 0.4%, respectively, for Enterobacteriaceae (10,992 strains tested against both drugs) and 99.0%, 0.2%, and 0% for anaerobes. All Haemophilus spp., groups A and B streptococci, penicillin-susceptible and -intermediate S. pneumoniae, and other penicillin-susceptible streptococci were susceptible to ertapenem. All oxacillin-susceptible Staphylococcus aureus were ertapenem susceptible, except 1 that was intermediate. Surrogate antimicrobial agents that can be used to reliably predict ertapenem susceptibility by MIC tests are imipenem for Enterobacteriaceae and anaerobes, oxacillin for staphylococci, and penicillin for streptococci.

Safety and local tolerability of intramuscularly administered ertapenem diluted in lidocaine: a prospective, randomized, double-blind study versus intramuscular ceftriaxone

BACKGROUND

Ertapenem is a new, structurally unique, parenteral beta-lactam antimicrobial agent that can be administered once daily.

OBJECTIVE

This study compared the local tolerability of ertapenem 1 g once a day administered intramuscularly (IM) versus IM ceftriaxone, with both drugs reconstituted in lidocaine.

METHODS

In this prospective, double-blind, multicenter study, adult patients with lower respiratory tract infection, skin infection, or urinary tract infection requiring initial parenteral therapy were randomly assigned in a 3:1 ratio to treatment with IM ertapenem 1 g once daily or IM ceftriaxone 1 g once daily. Although study drugs were administered by unmasked personnel, the patients, investigators, and the sponsor medical reviewer were blinded. Patients who improved clinically could be switched to oral amoxicillin-clavulanate after at least 2 days of IM therapy. Tolerability and safety analyses were carried out for the treated population, and efficacy analyses were performed for the modified intent-to-treat population.

RESULTS

A total of 117 patients were randomized. The 87 patients in the ertapenem group and 30 in the ceftriaxone group received IM therapy for a mean duration of 4.1 and 3.8 days, respectively. During treatment, 35.6% (31/87) of patients treated with ertapenem and 43.3% (13/30) of those treated with ceftriaxone experienced > or =1 symptom at the local injection site; the most common symptom was tenderness, followed by pain. Symptoms were moderate to severe in only 1 patient (1.1%) in the ertapenem group and 3 patients (10.0%) in the ceftriaxone group. Clinical drug-related adverse events were reported during IM therapy in 14 patients (16.1%) in the ertapenem group and 5 patients (16.7%) in the ceftriaxone group. Mean +/- SD creatine kinase concentrations, measured in all patients, were 204.8+/-234.8 U/L at the end of IM ertapenem therapy and 382.9+/-721.1 U/L at the end of IM ceftriaxone therapy; at follow-up, values had returned to normal or had decreased in all cases.

CONCLUSIONS

Ertapenem 1 g (reconstituted in lidocaine) administered once daily IM was generally well tolerated. The tolerability and safety profiles of IM ertapenem therapy in this study were comparable to those of IM ceftriaxone therapy.