Treating Serious Infections: Focus on Cefepime

Comparisons of parenteral broad-spectrum cephalosporins tested against bacterial isolates from pediatric patients: report from the SENTRY Antimicrobial Surveillance Program (1998–2004)

A contemporary collection of 12737 strains from pediatric patients (<18 years) isolated over a 7-year period (1998-2004) from 52 sentinel hospitals in North America was tested to determine the comparative antimicrobial potency of broad-spectrum parenteral cephalosporins and selected comparator agents. Most of the strains (84.1%) were isolated from blood stream or respiratory tract infections. The rank order of the top 10 pediatric pathogens analyzed was Streptococcus pneumoniae (15.5%) >Haemophilus influenzae (14.6%) >Staphylococcus aureus (13.8%) >Moraxella catarrhalis = coagulase-negative staphylococci (8.0%) >Escherichia coli (7.8%) >Pseudomonas aeruginosa (5.2%) >Klebsiella spp. (4.8%) >Enterococcus spp. (4.7%) > beta-hemolytic streptococci (4.4%). Both cefepime and ceftriaxone (MIC(90), 1 microg/mL; 93.9% and 93.7% susceptible, respectively) were highly active against S. pneumoniae. However, the S. pneumoniae strains showed reduced susceptibility to ceftazidime (56.6%), as well as penicillin (56.6%) < trimethoprim-sulfamethoxazole (57.1%) < erythromycin (66.2%) < tetracycline (71.4%). beta-Hemolytic streptococci showed 100.0% susceptibility to penicillin, cefepime, and ceftriaxone. Cefepime and ceftriaxone exhibited high activity against oxacillin (methicillin)-susceptible S. aureus, (MIC(90), 4 microg/mL; 100.0% and 99.8% susceptible, respectively), whereas ceftazidime (MIC(90), 16 microg/mL) was active against only 86.7% of strains. H. influenzae strains showed complete susceptibility to cefepime, ceftriaxone, and levofloxacin (MIC(90), < or =0.5 microg/mL; 100.0%), and 34.0% of H. influenzae and 99.2% of M. catarrhalis strains produced beta-lactamase. Although the 3 cephalosporins tested (cefepime, ceftriaxone, and ceftazidime) were very active (98.6-99.6% susceptible) against E. coli, cefepime (99.0% susceptible) was slightly more active than ceftriaxone and ceftazidime (96.4% and 95.1% susceptible, respectively) against Klebsiella spp. Cefepime was also the most active beta-lactam agent tested against Enterobacter spp. (MIC(90), 2 microg/mL; 99.3% susceptible), whereas the susceptibility rates of other broad-spectrum beta-lactams (ceftriaxone, ceftazidime and piperacillin-tazobactam) were significantly lower (78.4-81.5%). Against P. aeruginosa, imipenem and piperacillin-tazobactam showed the highest susceptibility rates (94.4% and 93.3%, respectively), whereas imipenem and cefepime showed the lowest resistance rates (1.4% and 2.3%, respectively). Our results indicate that cefepime was the most broad-spectrum cephalosporin analyzed and remains a very potent alternative for the treatment of contemporary pediatric infections in North America.

Pharmacodynamic profiling of cefepime in plasma and cerebrospinal fluid of hospitalized patients with external ventriculostomies

Population pharmacokinetic (PK) modeling and Monte Carlo simulation (MCS) were used to describe the pharmacodynamic profile of cefepime in the both plasma and cerebrospinal fluid (CSF). Plasma and CSF cefepime data were obtained from a PK study of 7 hospitalized patients with external ventricular drains. Concentration-time profiles in plasma and CSF were modeled using a 3-compartment model with zero-order infusion and first-order elimination and transfer. Estimates of the PK parameters were identified in the Big Non Parametric Adaptive Grid with adaptive gamma (BigNPAG) program of Leary, Jelliffe, Schumitzky, and Van Guilder. MCS (10,000 subjects) was performed to estimate the probability of attaining the targets of free plasma concentration (20% protein binding) and total drug CSF concentration of 50-100% T>minimal inhibitory concentration (MIC) for MICs 0.06-8 mg/L for cefepime 2 g, iv, every 8 h (0.5-h infusion); cefepime 2 g, iv, every 12 h (0.5-h infusion); and cefepime 2 g (0.5-h infusion) once and 250 mg/h continuous infusion. After the Bayesian step, the observed-predicted regression and r(2) for plasma and CNS were as follows: plasma, observed=0.984 x predicted+2.570, r(2)=0.944; CSF, observed=0.785 x predicted+0.868, r(2)=0.821. The median penetration of cefepime as measured by AUC(CSF)/AUC(plasma) was 7.8%. In the MCS, the target attainment rates in plasma for 60-70% fT>MIC were high at each MIC value between 0.03 and 8 microg/mL for each regimen examined. In CSF, none of the regimens achieved 50-100% T>MIC for>80% of patients for MICs>0.5 mg/L.