[Clinical investigation on target value of T>MIC in carbapenems]

There have been few clinical reports on pharmacokinetics-pharmacodynamics (PK-PD) theory, although many basic or fundamental researches on appropriate use for the antimicrobials based on the PK-PD theory have been performed. We evaluated the target T>MIC values on meropenem and biapenem which have been obtained by basic researches. While we investigated whether the target T>MIC values were also useful for anaerobic infections. Clinical and bacteriological efficacies of meropenem and biapenem were about 70% in T>MIC over 25% or over 80% in T>MIC over 30%. When monomicrobial infections by anaerobes were occurred as abscesses, there have been no correlation between target T>MIC values and clinical effect. When polymicrobial infections between aerobes and anaerobes were occurred, we have achieved over 90% clinical efficacy when over 20% T>MIC values. These results supported the data by Craig, W. A. and Drusano, G. L. The regimen based on PK-PD theory would be useful in clinical practice including against anaerobic infections.

[Analysis on the effective dosage regimens for meropenem, biapenem and doripenem against P. aeruginosa infection based on pharmacokinetics and pharmacodynamics theory]

Recently, PK/PD (pharmacokinetics/pharmacodynamics) analysis for the antimicrobial dosage method became one of the popular categories in chemotherapy and infectious disease societies world wide. Carbapenems are often used for empiric therapy because of its broad-spectrum and activities against microorganisms. PK/PD analysis is well studied in some antibiotics including carbapenems and it is necessary also from the point of view of prevention for emergence of resistant strains. We report the result of the analysis for the effective dosage regimens of meropenem, biapenem and doripenem against Pseudomonas aeruginosa infection based on PK/PD theory with the MIC distributions against the strains isolated from the patients blood at Keio University in 2004 and 2006. The highest target attainment rate for the free drug 40% time above the MIC (40%T > or = MIC) in traditional infusion with the MIC distribution against P. aeruginosa isolated from the patients blood at Keio University Hospital in 2004 was as follows: 90.89% in 500 mg every 6 hours regimen for meropenem, 83.25% in 300 mg every 6 hours regimen for biapenem, 81.73% in 250 mg every 6 hours regimen for doripenem in the approved maximum daily dose for each agent. The highest target attainment rate for the free drug 40%T > or = MIC in prolonged infusion with the MIC distribution against P. aeruginosa isolated from the patients blood at Keio University Hospital in 2004 was as follows: 100% in 500 mg every 6 hours regimen for meropenem, 83.97% in 300 mg every 8 hours regimen for biapenem, 99.98% in 500 mg every 8 hours regimen for doripenem in the maximum daily dose for each agents. The highest target attainment rate for the free drug 40%T > or = MIC in traditional infusion with the MIC distribution against P. aeruginosa isolated from the patients blood at Keio University Hospital in 2006 was as follows: 80.57% in 500 mg dose in every 6 hours regimen for meropenem, 56.70% in 300 mg every 6 hours regimen for biapenem, 69.44% in 250 mg every 6 hours regimen for doripenem in the maximum daily dose for each agent. The highest target attainment rate for the free drug 40%T > or = MIC in prolonged infusion with the MIC distribution against P. aeruginosa isolated from the patients blood at Keio University Hospital in 2006 was as follows: 89.35% in 500 mg every 6 hours regimen for meropenem, 60.84% in 300 mg every 6 hours regimen for biapenem, 82.78% in 500 mg every 8 hours regimen for doripenem in the maximum daily dose for each agent. The target attainment rates for the free drug Css/MIC > or = 1 with continuous infusion were lower than the target attainment rates for the free drug 40%T > or = MIC in the regimens of prolonged infusion intermittent dose regimens in all three agents using both of the MIC distributions against P. aeruginosa in 2004 and 2006. The result of the PK/PD analysis for meropenem, biapenem and doripenem indicated that intermittent dose with prolonged infusion was the best method to obtain higher target attainment rate.

Peritoneal penetration of doripenem after intravenous administration in abdominal-surgery patients

OBJECTIVES

This study aimed to examine the peritoneal penetration of intravenous doripenem, a novel carbapenem used for the treatment of intra-abdominal infections.

PATIENTS AND METHODS

Doripenem (500 mg) was administered to 10 patients before abdominal surgery. Venous blood and peritoneal exudate samples were obtained at the end of infusion (0.5 h) and every hour for 6 h afterwards. The drug concentrations in serum and exudate were measured using HPLC, estimated by non-compartmental pharmacokinetic analysis and fitted to a three-compartment pharmacokinetic model in order to assess the exposure time that the drug concentration remained above MIC.

RESULTS

The AUC(0-infinity) was 59.3 +/- 7.2 mg.h/L (mean +/- SD) in serum and 49.3 +/- 6.5 mg.h/L in exudate, and the exudate/serum ratio was 0.84 +/- 0.13. The observed maximum concentration was 46.9 +/- 7.4 mg/L at 0.5 h in serum and 24.5 +/- 6.5 mg/L at 0.7 +/- 0.4 h in exudate, and the exudate/serum ratio was 0.53 +/- 0.17. The compartmental analysis showed that the average concentrations remained higher in exudate than in serum after 0.81 h post-dose, and the average drug-exposure times in serum (91% fraction unbound) and exudate were: 73.6% and 78.2% at an MIC of 1 mg/L; 37.0% and 41.5% at 4 mg/L; and 12.7% and 13.1% at 16 mg/L.

CONCLUSIONS

Following intravenous administration, doripenem penetrated well into peritoneal exudate of abdominal-surgery patients, and the drug-exposure times in exudate were greater than or equal to those estimated from serum data.

Prolonged use of carbapenems and colistin predisposes to ventilator-associated pneumonia by pandrug-resistant Pseudomonas aeruginosa

OBJECTIVE

We present our experience with five cases of pandrug-resistant Pseudomonas aeruginosa ventilator-associated pneumonia (VAP) and analysis of risk factors.

DESIGN AND SETTING

Case-control study in a 15-bed intensive care unit (ICU).

PATIENTS AND PARTICIPANTS

The study included 5 cases and 20 controls. Each case patient was matched to four contemporary controls according to gender, prior hospital admissions, hospitalization duration, ICU admission cause, Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Function Assessment (SOFA) scores on ICU admission, and length of ICU stay, and mechanical ventilation duration until first VAP episode by a multidrug-resistant bacterium.

MEASUREMENTS AND RESULTS

Recorded variables included age, gender, daily APACHE II and SOFA scores, patient medication, treatment interventions, positive cultures and corresponding antibiograms, occurrence of infection, sepsis, and septic shock, other ICU-associated morbidity, length of ICU stay and mechanical ventilation, and patient outcome. Healthcare worker and environmental cultures, and a hand-disinfection survey were performed. Pandrug-resistant P. aeruginosa isolates belonged to the same genotype and were bla (VIM-1)-like gene positive. The outbreak resolved following reinforcement of infection-control measures (September 27). The sole independent predictor for pandrug-resistant P. aeruginosa VAP was combined use of carbapenem for more than 20 days and colistin use for and more than 13 days (odds ratio 76.0; 95% confidence interval 3.7-1487.6). An additional risk factor was more than 78 open suctioning procedures during 6-26 September (odds ratio 16.0; 95% confidence interval 1.4-185.4).

CONCLUSIONS

Prolonged carbapenem-colistin use predisposes to VAP by pandrug-resistant P. aeruginosa. Cross-transmission may be facilitated by open suctioning.

Is combination therapy with betalactam plus aminoglycoside (AGL) improving the outcome of nosocomial meningitis in children?

We have been unable to document a benefit of a combination of aminoglycosides with betalactam or carbapenem antibiotics in nosocomial meningitis. This was similar to the cases of sepsis, where survival of patients did not improve with combination therapy. Combination therapy did not increase the chance of appropriateness of the therapy. 30% of those on combination therapy were considered as inappropriately treated in comparison to 2.8% of those on monotherapy (p<0.01).

Prediction of pharmacokinetics of CS-023 (RO4908463), a novel parenteral carbapenem antibiotic, in humans using animal data

The pharmacokinetics of CS-023 (RO4908463, formerly R-115685), a novel parenteral carbapenem antibiotic, in humans was successfully predicted using the data collected from mice, rats, rabbits, and dogs; while inclusion of the monkey data led to a significant underestimation of the total plasma clearance (CL). Double logarithmic plots of CL and distribution volume at the steady-state (Vss) vs. body weight in four animal species were linear with high correlation coefficients; and the predicted CL and Vss values in humans agreed well with the observed values after administration of CS-023 by an intravenous drip infusion for 30 min. The plasma concentration-time profile in humans, which was predicted using a bi-exponential equation fitted to a complex Dedrick plot of the animal data, approximated the observed profile. An underestimation of CL caused by including the monkey data in a prediction is quite likely due to the net tubular reabsorption in monkeys, but not at least in rabbits, dogs, and humans.

Effects of carbapenem exposure on the risk for digestive tract carriage of intensive care unit-endemic carbapenem-resistant Pseudomonas aeruginosa strains in critically ill patients

To determine the epidemiology and risk factors for carbapenem-resistant Pseudomonas aeruginosa (CR-PA) digestive tract colonization, weekly rectal and pharyngeal swabs were obtained in two serial incidence surveys (266 patients). Forty-two (16%) patients were CR-PA colonized (12 [29%] on admission and 30 [71%] in intensive care units). Pulsed-field gel electrophoresis showed extensive clonal diversity, although one specific clone (type B) was isolated from 11 patients. The presence of similar genotypes of CR-PA colonizing 30% of the CR-PA-colonized patients suggests the occurrence of cross-colonization; in addition, 10 pairs of carbapenem-susceptible P. aeruginosa (CS-PA) and subsequent CR-PA strains isolated from the same patients were found to be clonally identical and were considered to have been endogenously acquired (33%). All endogenously acquired CR-PA strains were isolated after exposure to a carbapenem, and 80% showed a phenotype of imipenem resistance (IR pattern) alone, while 67% of the CR-PA strains acquired by cross-transmission exhibited a multiresistant (MR) phenotype, with previous carbapenem exposure in 44%. Logistic regression analysis identified severity of acute illness (odds ratio [OR], 1.0; 95% confidence interval [CI], 1.0 to 1.1), prior carbapenem use (OR, 7.8; 95% CI, 1.7 to 35.3), and prior use of fluoroquinolones (OR, 11.0; 95% CI, 1.7 to 67.9) as independent risk factors for CR-PA digestive tract colonization. Overall, the local epidemiology of CR-PA digestive tract colonization was characterized by polyclonal endemicity with phenotype patterns of IR and MR divided evenly between patients. Restricting the use of particular agents, such as carbapenems and fluoroquinolones, should be considered advisable to minimize the problem of this antibiotic resistance. However, the possible risk for development of collateral unexpected bacterial resistance patterns should be accurately monitored.

[Clinical evaluation of biapenem for febrile neutropenia in patients with hematological disorders]

We examined the clinical evaluation of biapenem (BIPM) for febrile neutropenia in patients with hematological disorders. BIPM was administrated by drip infusion when fever developed over 37.5 degrees C with a neutrophil counts lower than 1000/microl. The underlying diseases were acute myelogenous leukemia in 16 cases, acute lymphocytic leukemia in 1, malignant lymphoma in 14, myelodysplastic syndrome in 1, aplastic anemia in 1. Microbiologically documented infections were found in 3 cases (9.1%) before treatment. Clinical effect was excellent in 9 cases, good in 11, fair in 6, poor in 7. Factors associated with efficacy rate were concomitant use of granulocytecolony stimulating factor, duration of neutropenia and neutrophil counts at day 3 of day after start of the therapy. No serious adverse events were observed in all cases, although one case developed exanthema. In conclusion, these results confirmed the efficacy and safety of BIPM for febrile neutropenia in patients with hematological disorders.

Impact of carbapenem administration on systemic endotoxemia in patients with severe sepsis and Gram-negative bacteremia

In order to investigate the effect of carbapenems on systemic endotoxemia, 20 patients with severe sepsis due to ventilator-associated pneumonia and Gram-negative bacteremia were enrolled; 10 (group A) were administered 1 g t.i.d. of imipenem/cilastatin and 10 (group B) 2 g t.i.d. of meropenem. Blood was sampled at 0 time and after 1, 2, 4, 6, 12, 24, 36, 48, 60, 72, 84 and 96 hours for detection of endotoxins (LPS), interleukin-6 (IL-6), C-reactive protein (CRP) and drug levels. LPS were determined by the QCL-1000 LAL assay, IL-6 by an enzymeimmunoassay, CRP by nephelometry and carbapenem levels by a microbiological assay. We did not find that carbapenems had any effect on the kinetics of LPS and CRP; IL-6 of group A was lower than group B at 72 and 84 hours. No correlation was observed between drug levels of any carbapenem and LPS, IL-6 or CRP. It is concluded that in septic patients with Gram-negative bacteremia administration of either imipenem or meropenem did not affect systemic endotoxemia. The above data support the safe administration of both carbapenems in patients with severe sepsis.

[Efficacy of injectable carbapenems for respiratory infections caused by Streptococcus pneumoniae and Haemophilus influenzae with Monte Carlo simulation]

Streptococcus pneumoniae and Haemophilus influenzae are two major pathogens for respiratory tract infections, and those infections might cause critically ill patients. We performed the analysis with Monte Carlo Simulation for 253 strains of S. pneumoniae and 309 strains of H. influenzae isolated in the Gifu prefecture in 2002 and 2003. As for the pneumococcal infection in patient with good immunological response, good clinical effect might be obtained by panipenem/betamipron (PAPM/BP) 500 mg, imipenem/cilastatin (IPM/CS) 500 mg, meropenem (MEPM) 500 mg and biapenem (BIPM) 300 mg, b.i.d., while for immunocompromised hosts or infections by penicillin-resistant Streptococcus pneumoniae (PRSP), PAPM/BP, 500 mg, b.i.d., or IPM/CS 500 mg, MEPM 500 mg, t.i.d. or BIPM 600 mg, b.i.d. would be recommended. As for the infections caused by H. influenzae, in patient with good immunological response, good clinical effect might be obtained by MEPM 500 mg, b.i.d or PAPM/BP 1000 mg, b.i.d., while for immunocompromised hosts, MEPM 500 mg, t.i.d. would be recommended. Monte Carlo Simulation would be one of the useful tools for appropriate antimicrobial chemotherapy also against respiratory infections.

Meta-analysis of prophylactic parenteral antibiotic use in acute necrotizing pancreatitis

BACKGROUND

Acute pancreatitis is a potentially serious condition. It carries an overall mortality rate of 10-15%. Infectious complications account for approximately 80% of deaths from acute pancreatitis, and the question arises whether or not prophylactic antibiotics are useful in the prevention of these complications. Therefore, we performed an evidence-based analysis to assess the effect of available prophylactic antimicrobial treatment on the development of infected necrosis and sepsis, need for surgery, and mortality.

METHODS

A comprehensive PubMed search was performed evaluating the value of prophylactic administration of parenteral antibiotics in patients with acute necrotizing pancreatitis. Only articles published in English language between January 1990 and May 2006 were included. The search strategy initially generated 692 articles related to antibiotics in the treatment of acute pancreatitis. This number was reduced to 97 publications related to clinical trials on the same topic. Finally, 10 randomized clinical trials concerning prophylactic parenteral antibiotics in patients with acute necrotizing pancreatitis were identified. We have performed a meta-analysis using the random-effects model to assess the impact of prophylactic antibiotics on development of infected pancreatic necrosis and sepsis, need for surgery, and overall mortality.

RESULTS

Patients with necrotizing acute pancreatitis should receive effective antibiotic prophylaxis (i.e., carbapenems intravenously) to decrease the risk of infected necrosis and sepsis and need of surgery.

CONCLUSIONS

While providing new insights into key aspects of antibiotic prophylaxis, this evidence-based analysis highlights the need for further clinical trials regarding the indications for antibiotic prophylaxis.

CW-270033, a Novel Pyrrolidinyl-thio Carbapenem, Has Potent Antimicrobial Activity in Vitro and in Vivo

CW-270033, an injectable carbapenem, is a novel, synthesized pyrrolidinyl-thio carbapenem. In the present study, the in-vitro and in-vivo antibacterial activities of CW-270033 against wild-type strains and clinical isolates were compared with those of imipenem and meropenem. CW-270033 was more active than imipenem against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) clinical isolates, but was slightly less active than meropenem. Against the Gram-positive clinical isolates methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE), CW-270033 was slightly more active than meropenem, but was less active than imipenem. CW-270033 displayed potent in-vivo activity against E. coli ATCC 25922, P. aeruginosa ATCC 27853, and S. aureus SMITH in the mouse systemic infection model; the efficacy of CW-270033 in this model was 2--7 fold higher than that of meropenem. This activity was comparable to the in-vitro activity of CW-270033. An intravenous injection of CW-270033 showed that the half-life of CW-270033 in serum in mice was about 20 min, which was about two times that of meropenem. CW-270033 was also found to be resistant to hydrolysis by the mouse renal dehydropeptidase I (DHP-I) enzyme.

Genesis of Methicillin-resistant Staphylococcus aureus and Selective Antibacterial Injection Pressure

We reported previously that cefazolin was related to an increase in methicillin-resistant Staphylococcus aureus (MRSA) between 1998 and 2000 at Yamagata University Hospital. The incidence of MRSA decreased, however, between 2001 and 2003. We examined the relationship between the use of antibacterial injection and MRSA incidence. MRSA increased in surgical and medical wards between 1998 and 2000, but decreased mainly in surgical wards between 2001 and 2003. We statistically analyed the number of inpatients detected with MRSA (MRSA patients) and the use of antibiotics per month. MRSA patients positively correlated with cephems and carbapenems, the highest positive correlation with cefazolin at a correlation coefficient (R) of 0.45 (p<0.001). In multiple linear regression analysis, cefazolin and carbapenems were chosen as independent variables of a regression equation predicting MRSA patients, during the MRSA decrease and in surgical wards. We thought, it was because carbapenems increased with cefazolin that only cefazolin was chosen as an independent variable during the MRSA increase. We found that the antibiotics as independent variables were associated with about 50% of MRSA by the multiple regression model contribution ratio. Cefazolin was used most for presurgical prophylaxis in surgical wards, and about 20% of surgical wards in medical wards. Carbapenems were use almost equally in surgical and medical wards, but the correlation with MRSA in medical wards was 0.21 (p<0.1) and in surgical wards 0.38 (p<0.005), showing a significant correlation with carbapenems in surgical wards. In conclusion, cefazolin and carbapenems were related to the incidence of MRSA, and carbapenems showed a significant correlation in the presence of cefazolin. This strongly suggests that MRSA is significantly generated when inpatients are given carbapenems after administration of cefazolin.

The Impact of an Antibiotic Cycling Program on Empirical Therapy for Gram-Negative Infections

BACKGROUND

Antimicrobial-resistant organisms are an emerging problem in the ICU. Therapy cycling empiric antibiotics between various classes may influence bacterial resistance patterns. Understanding the impact of cycling on the appropriate treatment of suspected Gram-negative infections is important.

METHODS

Data were prospectively collected on patients who were admitted to a 19-bed medical ICU (MICU). A total of 1,172 patients were admitted to the MICU for > 48 h and were evaluated during a 28.5-month period. After 4.5 months of baseline data collection, an antibiotic-cycling protocol was implemented, using four different antibiotic classes with Gram-negative activity that were cycled every 3 to 4 months. Therapy was considered to be inappropriate if the subsequent bacterial isolate was resistant to the empiric drug used.

RESULTS

There were 59 bloodstream infections (BSIs), 17 ventilator-associated pneumonias (VAPs), and 101 urinary tract infections (UTIs) involving Gram-negative bacteria among 139 patients. Fifty-five infections (31%) were due to Gram-negative bacteria resistant to one or more antibiotic agents (BSIs, 18 [30%]; VAPs, 4 [23%]; and UTIs, 33 [33%]). Fifteen patients received inappropriate empiral therapy for 18 resistant Gram-negative infections (BSIs, 7 [39%]; VAPs, 3 [75%]; UTIs, 8 [24%]). Patients receiving inappropriate therapy were more likely to die (10 patients [67%] vs 40 patients [32%], respectively; p < 0.01). There was no difference in the receipt of appropriate empirical antibiotic therapy during the baseline compared to cycling (infectious episodes, 15% vs 10%, respectively; p = 0.4).

CONCLUSIONS

Antimicrobial resistance occurred in almost 30% of ICU infections involving Gram-negative bacteria. Antibiotic cycling was not associated with significant changes in the receipt of appropriate empirical antimicrobial therapy for the treatment of ICU infections.

Frequency and predictors of colonization of the respiratory tract by VIM-2-producing Pseudomonas aeruginosa in patients of a newly established intensive care unit

The aim of this study was to examine the frequency and predictors of colonization of the respiratory tract by metallo-beta-lactamase (MBL)-producing Gram-negative bacteria in patients admitted to a newly established intensive care unit (ICU) of a tertiary care hospital. Specimens of tracheobronchial aspirates for microbiological studies were obtained every day for the first 3 days of the ICU stay and subsequently every third day for the rest of the ICU stay. PCR analysis and nucleotide sequencing were performed to identify bacteria that had MBL genes. Thirty-five patients (20 male, 15 female) were hospitalized during the initial 3 month period of functioning of the ICU. Colonization of the lower respiratory tract by Gram-negative bacteria was found in 29 of 35 patients (83 %) during the first 6-20 days (median 13 days) following admission to the ICU (13 patients with Acinetobacter baumannii, ten with Pseudomonas aeruginosa, three with Enterobacter aerogenes, two with Klebsiella pneumoniae and one with Stenotrophomonas maltophilia). Six of 29 patients (21 %) colonized with Gram-negative bacteria had bla(VIM-2)-positive P. aeruginosa isolates; one of these patients developed clinical infection due to this micro-organism. Previous use of carbapenems (P=0.01) or other beta-lactams (P=0.03), as well as a stay in the ICU of >20 days (P<0.001), were associated with colonization with bla(VIM-2)-producing P. aeruginosa. In conclusion, colonization by Gram-negative bacteria of the respiratory tract of patients in this newly established ICU was common (83 %). Use of beta-lactams, including carbapenems, was associated with subsequent colonization of the respiratory tract with MBL-positive P. aeruginosa.

Pharmacokinetics of CS-023 (RO4908463), a novel parenteral carbapenem, in healthy male Caucasian volunteers

The CS-023 concentration in plasma after administration by infusion to healthy volunteers at a dose of 700 mg was decreased, with a half-life of 1.7 h, and the cumulative urinary excretion was 59.4% of the dose. The total clearance, renal clearance, and volume of distribution were 8.12 liters/h, 4.14 liters/h, and 17.2 liters, respectively.

[Relationship between protein binding and antimicrobial activities of antibiotics against Streptococcus pneumoniae and Haemophilus influenzae]

Fifty isolates of Streptococcus pneumoniae and 42 isolates of Haemophilus influenzae were isolated from the blood of children admitted to pediatric wards of hospitals in subprefucture between January 1998 and December 2005. The susceptibilities were measured by a microbroth dilution method using a standard broth and a broth containing 4.5% albumin. Against S. pneumoniae, penicillin G, ampicillin, cefotaxime, ceftriaxone, panipenem, meropenem, vancomycin, cefditoren, cefcapene, cefteram, faropenem and tebipenem were used and against H. influenzae, ampicillin, piperacillin, cefotaxime, ceftriaxone, panipenem, meropenem, clavulanic acid/ amoxicillin, cefditoren, cefcapene, cefteram, faropenem and tebipenem were used. Against S. pneumoniae, tebipenem was the highest antimicrobial activity in oral antibiotics (MIC90; < or = 0.06 microg/ml) and panipenem showed the highest activity for intravenous antibiotics (MIC90; < or = 0.12 microg/ml). Against H. influenzae, cefditoren was the highest activity for oral antibiotics (MIC90; < or = 0.06 microg/ml) and meropenem showed the highest activity for intravenous antibiotics (MIC90; < or = 50.06 microg/ml). The MIC90s measured by albumin containing broth were higher than those measured by standard broth. Protein binding rates of ceftriaxone, cefditoren, and faropenem were greater than 90%, and the MIC90 of these antibiotics measured by albumin addition methods were over 4-fold higher than those measured by standard methods.

Challenges in Identifying New Antimicrobial Agents Effective for Treating Infections with Acinetobacter baumannii and Pseudomonas aeruginosa

Acinetobacter baumannii and Pseudomonas aeruginosa are gram-negative pathogens that target immunocompromised patients. They express a variety of determinants that confer resistance to a broad array of antimicrobial agents. Mechanisms of resistance include impaired entry through the bacterial outer membrane, production of antibiotic-modifying enzymes, active efflux, and target mutations that reduce antimicrobial affinity. It has been a challenge to identify new agents that have activity against the more resistant variants of these species. Doripenem is a carbapenem in phase 3 trials that has excellent activity against P. aeruginosa and A. baumannii. However, it lacks activity against strains that express resistance to the currently available carbapenems. Tigecycline is a newly licensed glycylcycline that lacks activity against P. aeruginosa but has encouraging activity against many A. baumannii isolates. Resistance to tigecycline can emerge during therapy, however, and is due to expression of multidrug efflux pumps.

Syntheses and pharmacokinetic studies of prodrug esters for the development of oral carbapenem, L-084

We discovered an orally active carbapenem, L-084, through pharmacokinetic studies on various prodrug esters of (1R,5S,6S)-6-[(R)-1-hydroxyethyl]-l-methyl-2-[1-(1,3-thiazolin-2-yl)azetidin-3-yl]thio-1-carbapen-2-em-3-carboxylic acid (LJC11,036). L-084 showed a strong antimicrobial activity against Gram-positive and Gram-negative bacteria and exhibited the highest intestinal absorption among synthesized prodrugs of LJC11,036.

Hospital-acquired pneumonia in the 21st century: a review of existing treatment options and their impact on patient care

Hospital-acquired pneumonia is a common nosocomial infection, with significant morbidity and mortality, and represents a major therapeutic challenge to clinicians. The therapeutic approach must be patient-oriented and institution-specific. The specific risk factors of each patient, such as previous antibiotic exposure, underlying diseases, length of hospital stay and the local patterns of antimicrobial resistance, should guide physicians in their decision of the initial optimal empirical therapy. Delays in the initiation or inappropriate/inadequate initial therapy are related to increased mortality and worse outcomes. In responding patients, as soon as culture data are available, efforts should be made to change the initial broad spectrum antibiotic regimen to a more targeted one (de-escalation). The optimal duration of treatment is a matter of debate, but courses longer than 1 week are rarely justified.

High-dose cefepime as an alternative treatment for infections caused by TEM-24 ESBL-producing Enterobacter aerogenes in severely-ill patients

This study evaluated retrospectively the efficacy of treatment with cefepime vs. a carbapenem, in combination with amikacin or ciprofloxacin, for seriously-ill patients infected with ESBL-producing Enterobacter aerogenes who were admitted to an intensive care unit. Forty-four episodes of infection were investigated in 43 patients: 21 treated with cefepime; 23 with a carbapenem. The two treatment groups did not differ statistically in terms of age, APACHE II scores, and infection sites, but the average duration of antibiotic exposure was significantly shorter in the cefepime group (8.5 days vs. 11.4 days; p 0.04). Clinical improvement was seen in 62% of patients receiving cefepime vs. 70% of patients receiving a carbapenem (p 0.59). Bacteriological eradication was achieved in 14% of patients receiving cefepime vs. 22% of patients receiving a carbapenem (p 0.76). The 30-day mortality rates related to infection were 33% in the cefepime group and 26% in the carbapenem group (p 0.44). Thus, outcome parameters did not differ significantly between the two groups. Nevertheless, a statistically significant increase in failure to eradicate ESBL-producing E. aerogenes was observed as the MICs of cefepime rose (p 0.017). Pulsed-field gel electrophoresis revealed three distinct clones, but one predominant clone harbouring the bla(TEM-24) gene was associated with most (42/44) of the episodes of infection. It was concluded that cefepime may be an alternative agent for therapy of severe infections caused by TEM-24 ESBL-producing E. aerogenes, although further studies are required to confirm these observations.

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.

In vitro and in vivo antibacterial activities of SM-216601, a new broad-spectrum parenteral carbapenem

SM-216601 is a novel parenteral 1beta-methylcarbapenem. In agar dilution susceptibility testing, the MIC of SM-216601 for 90% of the methicillin-resistant Staphylococcus aureus (MRSA) strains tested (MIC(90)) was 2 microg/ml, which was comparable to those of vancomycin and linezolid. SM-216601 was also very potent against Enterococcus faecium, including vancomycin-resistant strains (MIC(90) = 8 microg/ml). SM-216601 exhibited potent activity against penicillin-resistant Streptococcus pneumoniae, ampicillin-resistant Haemophilus influenzae, Moraxella catarrhalis, Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, with MIC(90)s of less than 0.5 microg/ml, and intermediate activity against Citrobacter freundii, Enterobacter cloacae, Serratia marcescens, and Pseudomonas aeruginosa. The therapeutic efficacy of SM-216601 against experimentally induced infections in mice caused by S. aureus, E. faecium, E. coli, and P. aeruginosa reflected its in vitro activity and plasma level. Thus, SM-216601 is a promising candidate for nosocomial bacterial infections caused by a wide range of gram-positive and gram-negative bacteria, including multiresistant pathogens.

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.

A Practical and Facile Synthesis of Azetidine Derivatives for Oral Carbapenem, L-084

An orally active carbapenem L-084, which exhibits high bioavailability in humans, has a 1-(1,3-thiazolin-2-yl)azetidin-3-ylthio moiety at the C-2 position of the 1beta-methylcarbapenem skeleton. We established a practical and cost-effective synthesis of 3-mercapto-1-(1,3-thiazolin-2-yl)azetidine (1) for further scale-up production of L-084. This synthesis method entails an industry-oriented reaction of azetidine ring-closure to yield N-benzyl-3-hydroxyazetidine (16), which is eventually converted to 1 via key intermediates, Bunte salts 19 and 20.

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.

[A preliminary study of the administration of carbapenem antibiotics in sepsis patients on the basis of the administration time]

It is important to take into consideration the duration for which the plasma concentration of the drug is higher than the Minimal Inhibitory Concentration during treatment with carbapenem antibiotics, because the antibiotics are time-dependent drugs. A preliminary study of the administration of carbapenem antibiotics on the basis of the pharmacokinetics/pharmacodynamics (PK/PD) was conducted.

SUBJECTS

Ten patients with intraabdominal infection.

METHODS

The patients were divided into two groups: the first group was assigned to administration of a carbapenem antibiotic (meropenem) at a daily dose of 0.5 g in 3 divided doses, each dose by intravenous infusion over 3 hours (Group 3 H), and the other group was assigned to administration of each dose over 30 minutes (Group 30 M). The body temperature (BT), white blood cell count (WBC), serum C-reactive protein (CRP) level, and the systemic inflammatory reactive syndrome (SIRS) score before and 96 hours after the drug administration were compared between Group 3 H and Group 30 M.

RESULTS

There were 5 patients (mean age, 67.4+/-14.6 years) in Group 3H and 5 patients (mean age, 60.0+/-12.8 years) in Group 30 M. The evaluated parameters (BT, WBC, CRP, SIRS score) before the drug administration in Groups 3 H and 30M were not significant. Group 3 H showed significant decreases in the SIRS scores at 96 hours after the drug administration, however, there were no significant differences in the BT, WBC or CRP between the two groups.

DISCUSSION

Group 3 H showed early improvement in the SIRS scores. Administration of carbapenem antibiotics based on the PK/PD is important, and requires further studies.

Malignant external otitis: treatment with prolonged usage of antibiotics and Burow's solution

Malignant external otitis is a severe infection of the external auditory canal, generally caused by Pseudomonas aeruginosa in elderly diabetics patients. We describe a case of malignant external otitis in a 63-year-old man with severe otalgia, purulent otorrhea and polypoid granulation of the external auditory canal. Local debridement, insulin treatment and 6-week intravenous antibiotic therapy with carbapemens were very effective and the granulation tissue disappeared completely. However, the patient readmitted for recurrent disease 3 weeks later, despite the oral and ear drop administration with new quinolone. No recurrence has been noted after 4-week additional treatment with intravenous carbapenems followed by 3-week treatment with Burow's solution as ear drops.

[The proper use of carbapenem examined by Monte Carlo simulation]

Monte Carlo simulation was employed for this comparative study to determine the optimal Carbapenem and its dosing strategy to cure the infections by Escherichia coli and Pseudomonas aeruginosa and to consider how the difference of each Carbapenems in dosing regimens and antibiotic activity influenced to maximize % T > MIC. This result revealed that it was important to increase a dose and a number of doses a day, in addition to great antibiotic activity for maximizing % T > MIC.

[Antibiotic prophylaxis in acute pancreatitis--is the evidence good enough?]

BACKGROUND

Randomized controlled trials on acute necrotizing pancreatitis suggest that prophylactic antibiotics can reduce mortality and morbidity in these patients by preventing pancreatic infections.

MATERIAL AND METHOD

Relevant articles were assessed using a clinical appraisal skills programme.

RESULTS

Eight trials have been published since 1990. The early trials showed that prophylactic antibiotics did reduce mortality and morbidity; however, errors of methodology weaken these results. In later trials results have varied: in September 2004, Isenmann et al. published a trial with a greatly improved design and found no effect of prophylactic antibiotics compared to antibiotic treatment on demand.

INTERPRETATION

Based on the results obtained so far, the evidence is not yet strong enough to recommend prophylactic antibiotics in acute necrotizing pancreatitis. There is still a need for a new, larger, multicentre study that pays careful attention to all aspects of the condition, for instance diagnosis and treatment of abdominal compartment syndrome, and guidelines for method and time of surgery.

[Study of administration times and clinical efficacy of carbapenems in the treatment of moderate community-acquired bacterial pneumonia]

The half-lives of carbapenems are about 1 hour. It was expected that increasing the daily frequency of administration would improve the clinical effects. We therefore studied the clinical effects of increasing the daily administration frequency of meropenem in the treatment of community-acquired bacterial pneumonia. The subjects were patients with moderate community-acquired bacterial pneumonia who were aged less than 75 years. They were divided into a BID group (28 patients receiving 0.5 g morning and evening) and a TID group (27 patients receiving 0.25 g in the morning and about midday, and 0.5 g in the evening), and the clinical effects were reviewed prospectively. Clinical efficacy on the third day was 78.6% in the BID group and 85.2% in the TID group, and over-all clinical efficacy was 89.3% in the BID group and 88.9% in the TID group. Administration periods were 12.8 +/- 4.2 days in the BID group and 10.9 +/- 3.4 days in the TID group. These results show no statistically significant difference, and suggest that the excellent clinical effect of administration of MEPM 0.5 g twice a day on moderate community-acquired bacterial pneumonia is not improved by administration three times a day.

Optimizing antimicrobial pharmacodynamics: dosage strategies for meropenem

INTRODUCTION

Carbapenems are broad-spectrum antibiotics that are often employed as the last line of therapy for patients with nonresponsive nosocomial infections. Consideration of pharmacodynamic principles in dosage regimens for these agents can maximize their antibacterial effectiveness and reduce the number of bacterial strains that survive to mutate or continue infection.

OBJECTIVE

The objectives of this review were to highlight examples of the application of pharmacodynamics to the carbapenems (particularly meropenem) and to comment on clinical utility of these dosage regimens.

METHODS

Relevant information was identified through a MEDLINE search of the literature (1980-present) using the terms carbapenem, pharmacodynamic, pharmacokinetic, pharmacoeconomic, meropenem, imipenem, ertapenem, biapenem, and panipenem. Additionally, meeting posters were identified from the International Conference of Antimicrobial Agents and Chemotherapy (years 2001-2003) and the International Conference of the American Thoracic Society (years 2002-2003). All studies demonstrating the pharmacodynamics of the carbapenems by incorporating changes in dosage strategies were included.

RESULTS

Only relevant data for meropenem were identified in our literature search. The dosage scheme for meropenem may be modified to maximize the percentage of the dosage interval that drug concentrations remain above the minimum inhibitory concentration, an important parameter related to the bacterial kill rate. Only relevant data for meropenem were identified in our literature search. Human volunteer and Monte Carlo simulation studies suggested that in the treatment of susceptible pathogens, higher meropenem doses, increased frequency of administration, or prolonged duration of infusion resulted in improved pharmacodynamics.

CONCLUSION

When proper pharmacodynamic principles are applied to dosage strategies for meropenem, clinical and microbiological outcomes can be optimized.

Antibiotics in older adults

Antibiotics are frequently prescribed in the older person, the dosification needs special care, since the pharmacokinetic parameters changes with aging and the side effects can be different in the older person. The creatinine clearance changes and we must modify the way we prescribe such antibiotics to the elderly, calculating. The variety of antibiotics now available led us to consider this paper in which we have presented the antimicrobial agents that can be considered in the treatment of the older person. We present several groups: the penicillins, cephalosporins, monobactams, carbapenems and betalactamase inhibitors or the great betalactam group. Other trimetroprin-sulfame-thoxazole, the newer macrolides (azithromycin and clarithromycin) as well as the aminoglycosides, vancomycin, clindamycin, metroridazole. The indications and contraindications are presented and reviewed.

Cefepime or carbapenem treatment for febrile neutropenia as a single agent is as effective as a combination of 4th-generation cephalosporin + aminoglycosides: comparative study

1998, a consensus meeting was held in Miyazaki, Japan, to develop an approach to management of febrile neutropenia (FN). The K-HOT study group decided to examine whether this proposal was applicable to clinical practice in a multicenter study. Patients who developed fever with neutrophil counts <1,000/microL were randomized to receive either a single antibiotic, cefepime or one of the carbapenems, or a combination of cefepime and an aminoglycoside. Patients who became afebrile within the first 3 days were continued on the same treatment. Patients who remained febrile were switched to a combination regimen if they were randomized to receive a single agent, and patients on combination medication were changed from cefepime to another cephalosporin. A total of 165 patients were entered into the trial. One hundred fifty-three patients were evaluable for response. The average age was 52 years, and 70% of the patients had acute leukemia. Severe neutropenia, defined as <100/microL at the time of FN, was seen in 62% of the patients on entry and during the course of treatment 71% of patients experienced neutrophil counts of <100/microL. Microbiologically documented infection was seen in 6.5% for monotherapy, and 10.5% for a combination treatment, and fever of unknown origin occurred in 75.3% and 59.2% of the patients in each regimen, respectively. Excellent to good response was seen in two-thirds of the patients in all treatment groups. Adverse events were minimal, and three early deaths were observed at days 9, 16, and 16 among patients treated with a single antibiotic and three in the combination regimen group at days 14, 15, and 20. These results indicate that cefepime or a carbapenem alone is as effective as a combination of cefepime and an aminoglycoside for treating FN.

[A questionnaire survey on antimicrobial chemotherapy for acute peritonitis]

A questionnaire survey on antimicrobial chemotherapy for acute peritonitis was conducted to obtain the consensus among abdominal surgeons in Japan in the period from January to March 2002. Forty-one of the 58 surgeons replied, and the following consensus was obtained. Antibiotics should be given as soon as possible the diagnosis of infection in the abdominal cavity is established. When the perforated viscus is demonstrated at operation, giving antibiotic should be reconfirmed whether it covers organisms in the perforated site or not. The ascites obtained at operation should be sent for bacterial culture. When postoperative course is eventful, considering WBC, body temperature and CRP, the drainage fluid should be sent for culture on 4 to 7 days postoperatively. Most commonly used antibiotic for perforation of duodenal ulcer is cefotiam, and it is given 4.1 +/- 1.2 days postoperatively. Target organisms at the perforation of the lower digestive tract were E. coli, Bacteroides spp., Klebsiella pneumoniae and Enterobacter spp. Carbapenems were likely given agents for the perforation of the colon, and they were given 5.0 +/- 1.4 days postoperatively.

Physicochemical analyses of phase transition and dehydration processes of a new oral 1beta-methylcarbapenem antibiotic agent, CS-834

The characterizations of the anhydrate (A-form), monohydrate (B1-form), and dihydrate (B2-form) of CS-834 were investigated by powder X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetry-differential thermal analysis (TG-DTA), infrared spectroscopy, and Karl Fischer moisture titration. The typical DSC curve of the B2-form showed five endothermic peaks at 35.0, 46.4, 56.2, 99.2, and 190.4 degrees C and an exothermic peak at 123.4 degrees C. In TG-DTA analysis, the three peaks at 35.0, 46.4, and 56.2 degrees C had a total weight loss of 7.3%, corresponding to the release of two water molecules. From morphological observation under thermomicroscopy, the endothermic peak at 99.2 degrees C was attributed to the melting of the dehydrous crystals (B0-form) and the exothermic peak at 123.4 degrees C to the recrystallization to the A-form crystals. The endothermic peak at 190.4 degrees C was due to the melting of the A-form crystals. After incubation for 6.0 h at 35, 50, 60, and 80 degrees C, the powder X-ray diffraction patterns of the B2-form indicated that it was converted into the A-form via the B1-form and B0-form. Thus CS-834 exists in homologous hydrous crystal forms in multiple-phase transformations with the dehydration of two water molecules.

[Investigation on administration method of carbapenems]

Seventy-two women diagnosed as parametritis were enrolled in this study and examined on the effective administration method of carbapenems, imipenem/cilastatin (IPM/CS), panipenem/betamipron (PAPM/BP) and meropenem (MEPM). The total dosage of each carbapenem was 1.5 g/day, and administration frequency was twice a day (0.75 g x 2) or three times a day (0.5 g x 3). We reviewed the highest body temperature, white blood cell count and CRP value, before treatment and the fourth day after the start of treatment. Three times a day method was statistically superior to twice a day method in the highest body temperature, and CRP value. When we use carbapenem antimicrobial agents, the basis of PK/PD of time above MIC would lead to the increasing clinical effects.

[Antibiotic prophylaxis of postoperative complications in surgical treatment of pulmonary, tracheal and mediastinal tumors]

A protocol of antibiotic protection, developed and used at Russian Research Center of Roentgenoradiology, is presented. This protocol of perioperative treatment is intended for control of a spectrum of bacterial infections retrospectively detected in patients with lung, tracheal, and mediastinal cancer. The efficiency of perioperative antibiotic prevention is demonstrated as exemplified by 105 patients of different age with various concomitant diseases.

Antimicrobial use and susceptibility rates in isolates from intensive care unit and other nosocomial inpatient and outpatient areas

Our objective was to evaluate the relation between antimicrobial use and susceptibility in the intensive care unit (ICU) and non-ICU inpatient areas in the Bolzano regional hospital. For the isolates of S. aureus, coagulase negative staphylococci, Enterococcus sp., P. aeruginosa and E. coli we found a pattern of significant stepwise decrease in the frequency of antimicrobial susceptibility to penicilloic beta-lactam antibiotics and first generation cephalosporins; the highest senitivity rates occurred among isolates from outpatients, followed in decreasing order by rates among isolates from non-ICU inpatients and from ICU-patients; the rate of use of this group of antimicrobial agents was relatively high in the intensive care unit (13,1%). For P. aeruginosa we observed significantly lower susceptibility-rates to second, third and fourth generation cephalosporins, carbapenems and monobactams for non-ICU inpatient areas than for outpatient or ICU areas; this paralleled with the low use of this group of agents in the ICU area (4,9%). Also, for P. aeruginosa the prevalence of susceptibility to ciprofloxacin and norfloxacin in inpatient areas was lower than in the outpatient or ICU-areas; the rate of quinolone-use was relatively low in the ICU area (4,2%).