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Delayed resistance selection for doripenem when passaging Pseudomonas aeruginosa isolates with doripenem plus an aminoglycoside.

Doripenem (formerly S-4661), a parenteral carbapenem, was tested in combination with an aminoglycoside (gentamicin) to determine the resistance selection of these codrugs during subinhibitory passaging using 6 Pseudomonas aeruginosa isolates. The organisms were selected based on doripenem and gentamicin MIC values to include isolates with MIC values near the susceptible breakpoints of both compounds and 1 strain highly resistant to gentamicin. Baseline MIC values were established for doripenem (2-8 microg/mL) and gentamicin (4 to >256 microg/mL) using reference broth microdilution methods, and passaging was carried out over 7 consecutive days. Doripenem MIC values increased 2 to >/=8-fold in 4 isolates, whereas 2 strains maintained the baseline doripenem MIC. When the experiment was performed with doripenem plus gentamicin, 3 strains maintained the original doripenem MIC values, 2 strains had a 2-fold increase, and only 1 strain showed a 4-fold increase in the doripenem MIC values. Previous studies have demonstrated doripenem to be more potent than other members in its class when tested against P. aeruginosa. The combination of doripenem and an aminoglycoside may be an effective treatment of infections caused by P. aeruginosa with elevated carbapenem MIC values with lower risk of selecting further resistance.

Aminoglycosides↗

Antimicrobial activity of doripenem (S-4661): a global surveillance report (2003).

The spectrum of activity and potency of doripenem, a broad-spectrum parenteral carbapenem currently in clinical development, was evaluated using 16 008 clinical bacterial isolates collected as part of an international surveillance project during 2003. Using reference broth microdilution methods, doripenem was found to be highly active against oxacillin-susceptible Staphylococcus aureus and coagulase-negative staphylococci (2705 and 297 isolates, respectively; MIC90s 0.06 mg/L), with a potency greater than that of other carbapenem antibiotics. Against enterococci (1474 isolates), with the exception of Enterococcus faecium, doripenem displayed modest activity (MIC50 4). Doripenem was among the most potent agents tested against Streptococcus pneumoniae, viridans group streptococci and beta-haemolytic streptococci (885, 140 and 397 isolates; MIC(90)s 0.5, 0.5 and 0.03 mg/L, respectively). For Enterobacteriaceae (> 6200 isolates), doripenem was four- to 32-fold more active than imipenem against wild-type isolates (MIC90s 0.03-0.5 mg/L). MIC90s for confirmed extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae (121 and 155 isolates; 0.06 and 0.12 mg/L, respectively) were two-fold higher than for wild-type isolates. Doripenem was also active against Citrobacter spp., Enterobacter spp. and Serratia spp. (MIC90s 0.06-0.25 mg/L), including ceftazidime-resistant isolates. Doripenem and meropenem were the most active agents among all beta-lactams against Pseudomonas aeruginosa (829 isolates; MIC50/90s 0.5/8 and 0.5/16 mg/L, respectively), whereas doripenem and imipenem were the most active agents against Acinetobacter spp. (155 isolates; MIC50/90s 0.5/4 and <or= 0.5/2 mg/L, respectively). Doripenem was slightly more potent (MIC50 2 mg/L) than ertapenem and imipenem (MIC50 4 mg/L), and had a potency similar to that of meropenem (MIC50 2 mg/L), against Burkholderia cepacia (20 isolates). Both Haemophilus influenzae (1824 isolates) and Moraxella catarrhalis (108 isolates), including beta-lactamase-positive isolates, were susceptible to doripenem (MIC90s 0.25 and 0.03 mg/L, respectively). Doripenem displays the favourable characteristics of other carbapenems, and appears to offer certain advantages in terms of potency, spectrum and beta-lactamase stability when compared with some carbapenems used currently to treat nosocomial infections.

Anti-Bacterial Agents↗

Doripenem (S-4661), a novel carbapenem: comparative activity against contemporary pathogens including bactericidal action and preliminary in vitro methods evaluations.

OBJECTIVES: To investigate the potency of doripenem, a broad-spectrum carbapenem characterized by a wider spectrum of activity combining antimicrobial and bactericidal features of imipenem and meropenem. METHODS: This parenteral compound was studied against recent clinical isolates (2001-2002) from a worldwide organism collection. A total of 902 strains were susceptibility tested by reference methods against doripenem and six to 28 comparators including ertapenem, imipenem and meropenem. The organisms tested included: Enterobacteriaceae (281 strains), Acinetobacter spp. (33), Pseudomonas aeruginosa (35), Stenotrophomonas maltophilia (36), other non-fermenters (22), Haemophilus influenzae (61), Moraxella catarrhalis (33), oxacillin-susceptible staphylococci (39), enterococci (84), streptococci (163), various anaerobes (98), and other Gram-positive species such as Corynebacterium and Bacillus spp. (17). RESULTS: Against Enterobacteriaceae, the average doripenem MIC90 was 0.03 mg/L (range, < or =0.015-0.25 mg/L). Doripenem was two- to 16-fold more potent than imipenem and comparable to ertapenem and meropenem; all doripenem MIC values with enteric bacilli were < or =4 mg/L. Doripenem was active against Aeromonas (MIC50, 0.03 mg/L), Bacillus spp. (MIC50, 0.03 mg/L) and all tested anaerobic species (MIC range, < or =0.015-4 mg/L), but was less active against S. maltophilia (MIC90, >32 mg/L) and Enterococcus faecium (MIC90, >32 mg/L) among the enterococcal species. Time-dependent bactericidal action was observed for doripenem and broth MIC results were slightly greater when compared to agar MIC results. In pilot testing, the optimal doripenem disc concentration was 10 microg, identical to standardized reagents for other clinically available carbapenems. CONCLUSIONS: Doripenem appears to be a potent carbapenem with a spectrum resembling currently marketed antipseudomonal carbapenems, but with greater activity when tested against some non-fermentative bacillary strains. Continued evaluation of doripenem against isolates resistant to other beta-lactams appears to be warranted.

Anti-Bacterial Agents↗

Comparative in vitro antimicrobial activity of a new carbapenem, doripenem: tentative disc diffusion criteria and quality control.

OBJECTIVES: To determine the spectrum of activity of doripenem and to propose tentative MIC and disc diffusion breakpoints. METHODS: The in vitro susceptibilities of 2137 bacterial isolates, representing 28 different species, to doripenem, imipenem and meropenem were determined by the NCCLS broth microdilution and disc diffusion testing methods. RESULTS: The doripenem MIC(50)s/(90)s were (in mg/L) for Enterobacteriaceae, 0.06/0.25; Pseudomonas aeruginosa, 0.25/1; Haemophilus influenzae, 0.12/0.5; streptococci, 0.016/0.5 and for staphylococci, 0.06/4. Like other carbapenems tested, doripenem MIC(50)s/(90)s were >32/>32 and 0.5/32 mg/L for the enterococci and non-fermentative Gram-negative bacilli (excluding P. aeruginosa), respectively. Against members of the Enterobacteriaceae and H. influenzae, doripenem was generally more active than imipenem and the same as or slightly less active than meropenem. Values for the non-fermentative Gram-negative bacilli excluding P. aeruginosa were comparable for all three carbapenems. Doripenem MICs increased with increasing resistance to methicillin (staphylococci), penicillin (streptococci) and strains that were beta-lactamase-negative ampicillin-resistant (Haemophilus). Doripenem exhibits excellent activity against extended-spectrum beta-lactamase-producing strains of Escherichia coli and Klebsiella spp. The NCCLS disc diffusion test was performed simultaneously on all organisms. CONCLUSIONS: Assuming the MIC susceptible breakpoints for doripenem are < or =1 mg/L for the streptococci and < or =2 mg/L for all other genera, then disc diffusion zone diameter breakpoints can be proposed. In addition, MIC and/or disc diffusion quality control ranges of doripenem were determined for 10 ATCC reference strains.

Carbapenems↗

Absence of convulsive liability of doripenem, a new carbapenem antibiotic, in comparison with beta-lactam antibiotics.

beta-Lactam antibiotics have been suggested to have some degree of convulsive activity and neurotoxicity in experimental animals as well as in clinical situations. We examined the convulsive activities of a new carbapenem antibiotic, (+)-(4R,5S,6S)-6-[(1R)-1-hydroxyethyl]-4-methyl-7-oxo-3-[[(3S,5S)-5-[(sulfamoylamino)methyl]-3-pyrrolidinyl]thio]-1-azabicyclo[3.2.0]hept-2-ene-2-carboxic acid monohydrate (doripenem) using several animals and compared them with beta-lactam antibiotics. In intravenous (IV) injection studies, imipenem/cilastatin, at 400/400mg/kg produced seizure discharges on electroencephalogram (EEG) accompanied with clonic convulsions in rats. Meropenem showed only wet dog shaking behavior at 200 and 400mg/kg. Doripenem caused no changes in the EEG and behavior in rats at 400mg/kg. Imipenem/cilastatin IV potentiated the pentylenetetrazol (PTZ)-induced convulsions in mice at 250/250 mg/kg, while meropenem, panipenem/betamipron, cefazolin or doripenem did not cause any marked effects at up to 500 mg/kg. In mouse intracerebroventricular (ICV) injection studies, imipenem, panipenem and cefazolin induced clonic convulsions in a dose-dependent manner in mice. Doripenem and meropenem did not induce convulsions at up to 100 microg/mouse. In dog ICV injection studies, imipenem produced generalized seizure discharge with clonic convulsions at 100 microg/dog. Meropenem also produced spikes or seizure discharges at 100, 300 and 1,000 microg/dog. However, doripenem had no effects on the EEG and behavior in dogs at any doses. In in vitro binding studies, imipenem, panipenem, cefazolin and meropenem inhibited [(3)H]muscimol binding to the GABA(A) receptor in mouse brain homogenates while doripenem did not cause any inhibition at up to 10mM. In addition, doripenem had no influence on the anti-convulsant actions of valproic acid in the PTZ- or bicuculine-induced convulsive model. These results clearly indicate that doripenem has no convulsive activity, suggesting that its neurotoxicity may be negligible in clinical use.

Alanine↗

Doripenem versus Pseudomonas aeruginosa in vitro: activity against characterized isolates, mutants, and transconjugants and resistance selection potential.

Doripenem is a broad-spectrum parenteral carbapenem under clinical development in Japan and North America. Its activities against (i) Pseudomonas aeruginosa isolates with graded levels of intrinsic efflux-type resistance, (ii) mutants with various combinations of AmpC and OprD expression, (iii) PU21 transconjugants with class A and D beta-lactamases, and (iv) P. aeruginosa isolates with metallo-beta-lactamases were tested by the agar dilution method of the National Committee for Clinical Laboratory Standards. Selection of resistant P. aeruginosa mutants was investigated in single- and multistep procedures. Doripenem MICs for isolates without acquired resistance mostly were 0.12 to 0.5 microg/ml, whereas meropenem MICs were 0.25 to 0.5 microg/ml and imipenem MICs were 1 to 2 microg/ml. The MICs of doripenem, meropenem, ertapenem, and noncarbapenems for isolates with increased efflux-type resistance were elevated, whereas the MICs of imipenem were less affected. The MICs of doripenem were increased by the loss of OprD but not by derepression of AmpC; nevertheless, and as with other carbapenems, the impermeability-determined resistance caused by the loss of OprD corequired AmpC activity and was lost in OprD- mutants also lacking AmpC. The TEM, PSE, PER, and OXA enzymes did not significantly protect P. aeruginosa PU21 against the activity of doripenem, whereas MICs of > or =16 microg/ml were seen for clinical isolates with VIM and IMP metallo-beta-lactamases. Resistant mutants seemed to be harder to select with doripenem than with other carbapenems (or noncarbapenems), and the fold increases in the MICs were smaller for the resistant mutants. Single-step doripenem mutants were mostly resistant only to carbapenems and had lost OprD; multistep mutants had broader resistance, implying the presence of additional mechanisms, putatively including up-regulated efflux. Most mutants selected with aminoglycosides and quinolones had little or no cross-resistance to carbapenems, including doripenem.

Bacterial Outer Membrane Proteins↗

Comparative activities of doripenem versus isolates, mutants, and transconjugants of Enterobacteriaceae and Acinetobacter spp. with characterized beta-lactamases.

Doripenem (S-4661), a new parenteral carbapenem, was tested against over 250 clinical isolates, mutants, and transconjugants of Enterobacteriaceae and Acinetobacter spp., selected or derived for their beta-lactamase expression characteristics. Imipenem, meropenem, and ertapenem were tested as comparators, along with cephalosporins and piperacillin-tazobactam, by using National Committee for Clinical Laboratory Standards agar dilution methodology. Doripenem MICs were from 0.03 to 0.25 microg/ml for Klebsiella isolates, irrespective of the presence of extended-spectrum beta-lactamases (ESBLs) or plasmid-mediated AmpC or hyperproduced K1 beta-lactamase. Similarly, MICs of doripenem for both AmpC-inducible and -derepressed Enterobacter isolates were 0.06 to 0.5 microg/ml. ESBL production did not raise the MICs of doripenem for Escherichia coli transconjugants, and studies with known expression mutants confirmed that neither inducible nor depressed AmpC beta-lactamase expression was protective in Enterobacter cloacae, Citrobacter freundii, Serratia marcescens, or Morganella morganii. In all of these respects, doripenem resembled meropenem and imipenem, whereas the MICs of ertapenem were raised (but still < or =1 microg/ml) for many ESBL-producing klebsiellas and AmpC-derepressed E. cloacae and C. freundii strains. Resistance to all carbapenems, including doripenem (MICs of mostly 16 to 64 microg/ml, compared with 0.25 to 1 microg/ml for typical strains), was seen in Acinetobacter isolates with metallo-beta-lactamases or OXA-carbapenemases. Isolates of Klebsiella and Serratia spp. with IMP, KPC, and SME beta-lactamases also were resistant to doripenem (MICs, 8 to >64 microg/ml) and to other carbapenems, although the continued apparent susceptibility (MICs, < or =0.5 microg/ml) of E. coli derivatives with cloned IMP-1 and NMC-A beta-lactamases suggested that carbapenem resistance might require other factors besides the enzymes.

Acinetobacter↗

Doripenem: S 4661.

Doripenem [S 4661] is a new parenteral carbapenem antibacterial undergoing clinical trials in Japan and North America. It is characterised by a 1beta-methyl group and a sulfamoylaminomethyl substituted pyrrolidylthio group at the C2 position. The compound has good activity against both Gram-positive and Gram-negative bacteria and superior activity to meropenem and imipenem against Pseudomonas aeruginosa. It possesses higher stability than imipenem or meropenem against animal dehydropeptidase I. The compound is stable to most beta-lactamases produced by Gram-negative bacteria. Shionogi has stated that doripenem is expected to be effective at low doses. In May 2003, Shionogi and Peninsula Pharmaceuticals (USA) entered a licensing agreement for doripenem under which Peninsula obtained exclusive rights (including sublicense rights) to market and develop the product in North America. Shionogi will manufacture doripenem for worldwide distribution. Doripenem is currently undergoing phase III trials in Japan for pneumonia, chronic respiratory tract infections (RTIs) and urinary tract infections (UTIs). In its November 2002 pipeline, Shionogi stated that it plans to file a NDA in Q4 of 2003. Doripenem is also in phase II studies in hospitalised patients with complicated urinary tract infections including pyelonephritis. In September 2003, Peninsula announced it had completed enrolment in this trial, and results are expected later in the year. Doripenem has also completed two phase I studies in healthy volunteers with a number of different dosing regimens.

Anti-Bacterial Agents↗

Pharmacokinetics and tissue penetration of a new carbapenem, doripenem, intravenously administered to laboratory animals.

The pharmacokinetic properties of doripenem following 20 mg/kg i.v. infusion were studied in various laboratory animals. The concentrations of doripenem in plasma, urine and tissue samples were determined by bioassay. Mean AUC0(0-infinityS) (microg x h/ml) and urinary recoveries (UR, %, 0-24 h) were 14.1 and 36.3 in mice, 9.3 and 42.1 in rats, 47.9 and 47.6 in rabbits, 78.6 and 83.1 in dogs and 44.1 and 51.0 in monkeys, respectively. In monkeys, with co-administration of probenecid, the mean AUC(0-infinity) of doripenem increased about 2.2 times and urinary excretion was delayed slightly. In mice, the doripenem level was highest in the blood plasma, followed by the kidney, liver, lung, heart and spleen. These doripenem levels in various tissues rapidly decreased and no accumulation was observed. Serum protein binding rates (%) of doripenem were 25.2 in mice, 35.2 in rats, 11.8 in rabbits, 10.2 in dogs, 6.1 in monkeys and 8.1 in humans, respectively.

Animals↗

Comparative activity of doripenem and three other carbapenems tested against Gram-negative bacilli with various beta-lactamase resistance mechanisms.

Doripenem (formerly S-4661), a novel carbapenem antimicrobial, was compared with ertapenem, imipenem, and meropenem using reference broth microdilution test methods against wild-type and various resistant microbial subsets (380 strains). Doripenem and meropenem were consistently more potent than ertapenem or imipenem when tested against Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter spp. Ertapenem exhibited minimum inhibitory concentration (MIC) elevations for some isolates producing AmpC and extended-spectrum beta-lactamases, in contrast to greater enzyme stability for doripenem and other carbapenems tested. Multiple beta-lactamase (TEM, SHV, CTX-M, OXA, CMY types)-producing Escherichia coli had doripenem MIC values at </=0.016 mug/mL (with higher values for ertapenem). Doripenem appears to be a promising, potent carbapenem for parenteral use against contemporary Gram-negative bacilli producing various beta-lactamases.

Anti-Bacterial Agents↗

Activities of doripenem (S-4661) against drug-resistant clinical pathogens.

Doripenem (formerly S-4661), a new 1-beta-methyl carbapenem, was challenged with a worldwide collection of 394 drug-refractory isolates. For endemic extended-spectrum beta-lactamase- and stably derepressed AmpC-producing enteric bacilli, the doripenem MICs at which 90% of the isolates were inhibited (MIC90s) were 0.03 to 0.5 microg/ml, generally lower than those of comparator carbapenems. A greater proportion of strains among carbapenem-resistant nonfermentative gram-negative bacilli were inhibited by doripenem at < or =4 microg/ml, and doripenem was the most active carbapenem (MIC90, 1 to 4 microg/ml) against penicillin-resistant streptococci.

Bacteria↗

Doripenem.

Doripenem is a new member of the carbapenem class of beta-lactam antibiotics with broad-spectrum coverage of Gram-positive, Gram-negative and anaerobic pathogens similar to imipenem and, especially, meropenem. This parenteral antibiotic may offer slightly more activity than meropenem against selected pathogens, including coverage of some strains of Pseudomonas aeruginosa strains not susceptible to the other antipseudomonal carbapenems. Empiric therapy with doripenem, as with other antipseudomonal carbapenems, may be useful in hospital and intensive care unit settings where multidrug resistance has emerged, especially in Gram-negative enteric pathogens. When P. aeruginosa or multidrug-resistant Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus or vancomycin-resistant enterococci are involved, doripenem must be used in combination. Doripenem has a broad spectrum of activity against many common hospital pathogens, including P. aeruginosa and Burkholderia cepacia, which is similar to meropenem.

Bacteria, Anaerobic↗

In vitro activities of doripenem and comparator agents against 364 anaerobic clinical isolates.

The in vitro activities of doripenem against 364 anaerobic isolates were measured and compared to those of ertapenem, imipenem, meropenem, ceftriaxone, and levofloxacin. All of the carbapenems were active against nearly all Bacteroides fragilis group isolates. Doripenem was either comparable to or slightly less active than imipenem and meropenem against most isolates but more active than the other penems against Clostridium difficile. Doripenem appears to have excellent activity against a broad range of anaerobes.

Anti-Bacterial Agents↗

In vitro activity of doripenem against Pseudomonas aeruginosa and Burkholderia cepacia isolates from both cystic fibrosis and non-cystic fibrosis patients.

The in vitro activities of doripenem, imipenem, levofloxacin, piperacillin, ceftazidime, aztreonam, tobramycin, and cefepime were determined for 160 isolates of Pseudomonas aeruginosa (82 from cystic fibrosis [CF] patients) and 34 isolates of Burkholderia cepacia. Doripenem MIC90s were lower than those of all other comparative agents against all isolates combined and against all P. aeruginosa isolates. Doripenem was as active as levofloxacin and 2- to 32-fold more active than the other comparative agents against B. cepacia.

Anti-Bacterial Agents↗

In vitro antimicrobial activity of doripenem, a new carbapenem.

The doripenem MICs at which 90% of the tested strains were inhibited ranged from 0.03 to 1 microg/ml for 10 species of Enterobacteriaceae (n = 351), from 0.03 to 0.12 microg/ml for oxacillin-susceptible staphylococci (n = 119), from 4 to 32 microg/ml for oxacillin-resistant staphylococci (n = 64), from < or =0.008 to 0.06 microg/ml for penicillin-susceptible streptococci (n = 132), and from 1 to 4 microg/ml for penicillin-resistant streptococci (n = 51). Overall, doripenem demonstrated in vitro activity similar to that of meropenem against gram-negative pathogens and to that of imipenem against gram-positive pathogens.

Anti-Bacterial Agents↗

In vitro activity of doripenem (S-4661) against multidrug-resistant gram-negative bacilli isolated from patients with cystic fibrosis.

Doripenem 50% inhibitory concentrations (MIC50) and 90% inhibitory concentrations (MIC90) for multidrug-resistant strains of mucoid Pseudomonas aeruginosa (n=200 strains), nonmucoid P. aeruginosa (n=200), and Burkholderia cepacia complex (n=200) isolated from patients with cystic fibrosis were 8 and 32, 8 and 64, and 8 and 32 microg/ml, respectively. Doripenem had somewhat better activity than established antimicrobial agents.

Anti-Bacterial Agents↗

Use of pharmacokinetic-pharmacodynamic target attainment analyses to support phase 2 and 3 dosing strategies for doripenem.

A doripenem population pharmacokinetic model and Monte Carlo simulations were utilized for dose regimen decision support for future clinical development. Simulation results predict that 500 mg of doripenem administered over 1 h every 8 h would be effective against bacterial strains with MICs less than 2 microg/ml and that less susceptible strains could be treated with prolonged infusions.

Adolescent↗

Potency of carbapenems for the prevention of carbapenem-resistant mutants of Pseudomonas aeruginosa: the high potency of a new carbapenem doripenem.

The potencies of the carbapenems; doripenem (DRPM), meropenem (MEPM) and imipenem (IPM) in preventing the emergence of carbapenem-resistant mutants were examined in Pseudomonas aeruginosa strains. The carbapenems predominantly selected carbapenem-resistant mutants or carbapenem mutants with reduced susceptibilities that were specifically resistant to carbapenems and had arisen as a result of the reduced level of expression of the outer membrane protein with a molecular weight of about 48,000 (OprD). The potency of carbapenems in preventing the growth of the mutants differed for DRPM, MEPM and IPM. The isolation frequency of the mutant was examined on agar plates containing each of the carbapenems at a concentration of 1/2 or 1/4 MIC of each carbapenem for that mutant. Mutants were not selected on agar containing DRPM at a frequency of greater than 10(-9) per cell per generation, whereas mutants of each strain were selected on agar containing MEPM or IPM at frequencies of 10(-7) to 10(-9) per cell per generation. The drug concentrations and the drug concentration range for the selective increase of carbapenem resistant mutants in the broth culture containing each carbapenem differed for each carbapenem. DRPM exhibited both the lowest drug concentration and the narrowest range of drug concentration for selection of the carbapenem-resistant mutants. The results shown in this report indicated that DRPM exhibited the greatest ability to prevent the emergence of the mutant.

Anti-Bacterial Agents↗