In vitro activity of oritavancin alone or in combination against vancomycin-susceptible and -resistant enterococci

OBJECTIVES

The optimal treatment for serious infections due to Enterococcus spp. is unknown although combination antimicrobial therapy is often recommended for invasive infections to achieve bactericidal activity and improve clinical outcomes. Oritavancin is a novel lipoglycopeptide agent with in vitro activity against enterococci, including vancomycin-resistant VanA-type Enterococcus faecium. Data on its activity in combination with other antibacterials are limited. The objective of this study was to evaluate the activity of oritavancin alone and in combination with ceftriaxone, daptomycin, gentamicin, linezolid and rifampicin against vancomycin-susceptible and -resistant enterococci in in vitro time-kill analyses.

METHODS

Five enterococcal strains were used for all experiments: three vancomycin-resistant VanA-type E. faecium clinical bloodstream isolates, vancomycin-resistant VanA-type E. faecium ATCC 700221 and vancomycin-susceptible Enterococcus faecalis ATCC 29212. Individual drugs were tested at ¼, ½, 1, 2 and 4× MIC. Oritavancin combination experiments were performed with each agent at ¼× MIC.

RESULTS

Daptomycin was the most active single agent and was bactericidal against all strains at 4× MIC, followed by oritavancin, which was bactericidal against all three clinical VRE strains at ≥2× MIC. In combination experiments at ¼× MIC, oritavancin was synergistic with gentamicin against strains not displaying high-level aminoglycoside resistance. No other synergy against VRE strains was observed in any experiment. Strain- and drug-dependent antagonism was observed for many combinations.

CONCLUSIONS

These in vitro data do not support the routine use of combination therapy with oritavancin in the treatment of infections due to VRE.

Pathogenic relevance of Lactobacillus: a retrospective review of over 200 cases

Given that Lactobacillus has been reported to be the causative pathogen in many types of infection despite debate regarding the organism's clinical significance, a literature review was conducted to investigate the treatments and outcomes of Lactobacillus infections reported to date. In this article, the characteristics of over 200 reported cases of Lactobacillus-associated infections are summarized. Lactobacillus was found to be frequently associated with endocarditis and bacteremia. Lactobacillus was also associated with a variety of other infections including, but not limited to, peritonitis, abscesses, and meningitis. The species casei and rhamnosus were the most common. The isolates tended to be most sensitive to erythromycin and clindamycin and most resistant to vancomycin. The species that was most sensitive to vancomycin was acidophilus. The overall mortality rate was nearly 30%. There was a significant association between mortality and polymicrobial infection (P=0.004). In the subset of patients with bacteremia, increased mortality was associated with inadequate treatment (P=0.001) and polymicrobial bacteremia (P=0.044).

The Macrolide Antibiotics: A Pharmacokinetic and Pharmacodynamic Overview

The macrolide antimicrobial family is comprised of 14, 15 and 16 member-ringed compounds that are characterized by similar chemical structures, mechanisms of action and resistance, but vary in the different pharmacokinetic parameters, and spectrum of activity. The macrolides accumulate in many tissues such as the epithelial lining fluid and easily enter the host defense cells, predominantly macrophages and polymorphonuclear leukocytes (PMNs). Concentrations of the macrolides in respiratory tract tissues and extracellular fluids are in almost all cases higher than simultaneously measured serum concentrations, making them useful for respiratory tract infections. This review will focus on pharmacokinetic and pharmacodynamic aspects of the clinical relevant macrolides including azithromycin, clarithromycin, dirithromycin, erythromycin and roxithromycin.

Levofloxacin penetration into epithelial lining fluid as determined by population pharmacokinetic modeling and monte carlo simulation

Levofloxacin was administered orally to steady state to volunteers randomly in doses of 500 and 750 mg. Plasma and epithelial lining fluid (ELF) samples were obtained at 4, 12, and 24 h after the final dose. All data were comodeled in a population pharmacokinetic analysis employing BigNPEM. Penetration was evaluated from the population mean parameter vector values and from the results of a 1,000-subject Monte Carlo simulation. Evaluation from the population mean values demonstrated a penetration ratio (ELF/plasma) of 1.16. The Monte Carlo simulation provided a measure of dispersion, demonstrating a mean ratio of 3.18, with a median of 1.43 and a 95% confidence interval of 0.14 to 19.1. Population analysis with Monte Carlo simulation provides the best and least-biased estimate of penetration. It also demonstrates clearly that we can expect differences in penetration between patients. This analysis did not deal with inflammation, as it was performed in volunteers. The influence of lung pathology on penetration needs to be examined.

Postantibiotic effects of ABT-773 and amoxicillin-clavulanate against Streptococcus pneumoniae and Haemophilus influenzae

This study determined the postantibiotic effect (PAE) of ABT-773 versus that of amoxicillin-clavulanate against clinical isolates of Streptococcus pneumoniae and Haemophilus influenzae. The PAEs of ABT-773 and amoxicillin-clavulanate ranged from 2.3 to 6.0 h and 0 to 2.2 h against S. pneumoniae and from 2.7 to 9.1 h and 0 to 0.8 h against H. influenzae, respectively.

Multi-hospital analysis of antimicrobial usage and resistance trends

We report a pilot study comparing antimicrobial usage and antimicrobial resistance trends for prominent nosocomial pathogens between 1994-1996. A convenience sample of ten hospitals participated in this retrospective review. We found a large variation in antimicrobial use and resistance trends and that many hospitals did not have data readily available to evaluate drug usage and resistance rates. A significant strong positive correlation was observed between the usage of ceftazidime and the prevalence of ceftazidime resistant Pseudomonas aeruginosa (r = 0.8, p = 0.005) and of ceftazidime resistant Enterobacter species (r = 0.8, p = 0.02). The presence of antibiotic control policies correlated with lower rates of some resistant strains and less antibiotic use. Our findings can be a useful starting point for hospitals that want to systematically measure antimicrobial use and resistance. Hospital laboratories, pharmacies, and infection control departments must work together to develop databases that will facilitate such measurements.

Mechanism of action of and resistance to quinolones

A topoisomerase was identified as the bacterial target site for quinolone action in the late 1970s. Since that time, further study identified two bacterial topoisomerases, DNA gyrase and topoisomerase IV, as sites of antibacterial activity DNA gyrase appears to be the primary quinolone target for gram-negative bacteria. Topoisomerase IV appears to be the preferential target in gram-positive organisms, but this varies with the drug. Three mechanisms of resistance against quinolones are mutations of topoisomerases, decreased membrane permeability, and active drug efflux. Although these mechanisms occur singly, several resistance factors are often required to produce clinically applicable increases in minimum inhibitory concentrations. Appropriate drug selection and dosage and prudent human and veterinary interventions are important factors in controlling the emergence of resistance.

Antimicrobial-coated/bonded and -impregnated intravascular catheters

OBJECTIVE

To review the literature regarding the prevention of catheter colonization and catheter-related bloodstream infections (CRBIs) with the use of antimicrobial-coated/bonded and -impregnated intravascular catheters.

DATA SOURCES

Primary and review English-language literature were identified using MEDLINE (1966-September 2000) pertaining to the key terms antibiotic, antimicrobial, antiseptic, silver, and bonded, coated, Impregnated catheters. In addition, textbooks and relevant reference lists were reviewed.

DATA EXTRACTION

All articles identified through the data sources were evaluated. Information deemed relevant to the objectives of the review was included.

DATA SYNTHESIS

Significant morbidity and mortality are associated with the development of CRBIs. Preventative measures such as modification of these catheters with antimicrobial coating/bonding have produced varying results. Trials evaluating cefazolin, teicoplanin, vancomycin, silver, and chlorhexidine-silver sulfadiazine (C-SS) used for coated/bonded intravascular catheters have not demonstrated a consistent decrease in the incidence of CRBIs. However, a meta-analysis of trials evaluating C-SS intravascular catheters demonstrated a statistically significant reduction in CRBIs. A larger reduction in CRBIs has been reported with minocycline-rifampin (M-R) versus C-SS intravascular catheters. Use of the M-R and C-SS catheters may result in a cost savings of $100 million and reduce as many as 12,000 CRBI-related deaths annually when used short term (<7 d).

CONCLUSIONS

When used for short-term catheterization, M-R catheters appear to be superior to the currently available C-SS catheters at preventing CRBIs. Significant cost savings and reduction in mortality can be anticipated with the use of M-R catheters.

A prospective and retrospective analysis of the nephrotoxicity and efficacy of lipid-based amphotericin B formulations

STUDY OBJECTIVE

To determine the usage patterns of the lipid-based amphotericin B formulations at our institution and to compare the observed nephrotoxicity and efficacy of these formulations.

DESIGN

Prospective and retrospective observational study

SETTING

Urban 350-bed teaching hospital.

PATIENTS

Sixty-seven nonhemodialysis patients who were prescribed greater than 3 days of amphotericin B lipid complex (ABLC) or liposomal amphotericin B (L-AmB) from 1996-1999.

MEASUREMENTS AND RESULTS

Forty-six patients received ABLC and 21 received L-AmB. Oncology patients accounted for most prescriptions of both formulations. Amphotericin B lipid complex most frequently was prescribed for treatment of documented fungal infections (50%), followed by treatment of neutropenic fever (33%). Liposomal amphotericin B most frequently was prescribed for treatment of neutropenic fever (62%), followed by treatment of documented fungal infections (29%). Seventy-eight percent of patients treated with ABLC and 90% of those who received L-AmB were started on the lipid-based formulation due to being refractory or intolerant to prior antifungal therapy. Two (4.4%) patients receiving ABLC and four (19%) patients receiving L-AmB experienced nephrotoxicity at the end of therapy (NS). Of the patients with a documented fungal infection, 20 out of 23 (87%) of those treated with ABLC and 4 out of 5 (80%) of those treated with L-AmB had a complete or partial response to therapy (NS). One patient with febrile neutropenia had a breakthrough fungal infection while receiving L-AmB.

CONCLUSION

No significant differences in nephrotoxicity or efficacy were found between ABLC and L-AmB. Until further studies indicate clinically significant differences in nephrotoxicity between the two liposomal amphotericin B formulations, it is recommended that economics continue to be the major determinant for product selection.

Steady-state plasma and intrapulmonary concentrations of levofloxacin and ciprofloxacin in healthy adult subjects

STUDY OBJECTIVE

To determine the steady-state plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of levofloxacin and ciprofloxacin.

DESIGN

Multiple-dose, open-label, randomized pharmacokinetic study.

PARTICIPANTS

Thirty-six healthy, nonsmoking adult subjects were randomized either to oral levofloxacin, 500 or 750 mg once daily for five doses, or ciprofloxacin, 500 mg q12h for nine doses.

INTERVENTIONS

Venipuncture, bronchoscopy, and BAL were performed in each subject at 4 h, 12 h, or 24 h after the last administered dose of antibiotic.

MEASUREMENT AND RESULTS

Mean plasma concentrations of levofloxacin and ciprofloxacin were similar to those previously reported. For once-daily dosing of levofloxacin, 500 mg, the mean (+/- SD) steady-state concentrations at 4 h, 12 h, and 24 h in ELF were 9.9 +/- 2.7 microg/mL, 6.5 +/- 2.5 microg/mL, and 0.7 +/- 0.4 microg/mL, respectively; AM concentrations were 97.9 +/- 80.0 microg/mL, 36.7 +/- 23.4 microg/mL, and 13.8 +/- 16.0 microg/mL, respectively. For levofloxacin, 750 mg, the mean steady-state concentrations in ELF were 22.1 +/- 14.9 microg/mL, 9.2 +/- 5.3 microg/mL, and 1.5 +/- 0.8 microg/mL, respectively; AM concentrations were 105.1 +/- 65.5 microg/mL, 36.2 +/- 26.1 microg/mL, and 15.1 +/- 2.0 microg/mL, respectively. The concentrations of ciprofloxacin at 4 h and 12 h in ELF were 1.9 +/- 0.9 microg/mL and 0.4 +/- 0.1 microg/mL, respectively; AM concentrations were 34.9 +/- 23.2 microg/mL and 6.8 +/- 5.9 microg/mL, respectively. The differences in the ELF concentrations of the two levofloxacin groups vs those of the ciprofloxacin group were significant (p < 0.05) at each sampling time.

CONCLUSIONS

Levofloxacin was more extensively distributed into intrapulmonary compartments than ciprofloxacin and achieved significantly higher steady-state concentrations in plasma and ELF during the 24 h after drug administration.

Quinupristin-dalfopristin: an overview

Synercid (RP 59500), the first injectable streptogramin antibiotic, is composed of two semisynthetic pristinamycin derivatives, quinupristin and dalfopristin. Individually, each component has bacteriostatic activity against staphylococci and streptococci, but together, the agents exhibit synergy, leading to bactericidal activity. The combination drug, however, is bacteriostatic against Enterococcus faecium and has poor activity against Enterococcus faecalis. Despite a short half-life, an extended postantibiotic effect allows the agent to be dosed every 8-12 hours. Both drugs are largely hepatically metabolized and excreted in bile. Although not metabolized by cytochrome P450 3A4, quinupristin-dalfopristin can inhibit agents that are metabolized through this pathway. Dosage adjustments may be necessary in patients with hepatic dysfunction. Alterations in renal function have minimal effects on the agent's pharmacokinetics. Adverse events include arthralgia, myalgias, and infusion-related pain. Based on available data, quinupristin-dalfopristin appears to have a role in treating severely ill patients with infections due to multiresistant gram-positive pathogens.

Early bactericidal activity of paromomycin (aminosidine) in patients with smear-positive pulmonary tuberculosis

The early bactericidal activity of the aminoglycoside paromomycin (aminosidine) in doses of 7.5 and 15 mg/kg of body weight was measured in 22 patients with previously untreated smear-positive pulmonary tuberculosis. The fall in log(10) CFU per milliliter of sputum per day during the first 2 days of treatment for 7 patients receiving a paromomycin dosage of 7.5 mg/kg/day was 0.066, with a standard deviation (SD) of 0.216 and confidence limits from -0.134 to 0.266, and that for 15 patients receiving 15 mg/kg/day was 0.0924, with an SD of 0.140 and confidence limits from 0.015 to 0.170. The difference between the mean and zero was not significant for the 7. 5-mg/kg dose group but was significant for the 15-mg/kg dose group (t = 2.55, P = 0.023). Since paromomycin has no cross-resistance with streptomycin and has no greater toxicity than other aminoglycosides, these results suggest that it has the potential to substitute for streptomycin in antituberculosis regimens and may be a particularly valuable addition to the drug armamentarium for the management of multidrug-resistant tuberculosis.

Long-term clarithromycin decreases prednisone requirements in elderly patients with prednisone-dependent asthma

Prolonged use of prednisone is associated with serious side effects, such as osteoporosis, particularly among elderly individuals. Macrolide antibiotics exhibit anti-inflammatory effects that are distinct from their antimicrobial properties. Thus, the purpose of this case report is to describe the effects of prolonged treatment with clarithromycin, 500 mg bid, in reducing prednisone requirements in three elderly patients with prednisone-dependent asthma. Three patients (one woman and two men) aged 63 to 69 years, who had been treated with 5 to 10 mg prednisone daily for at least the last 12 months, were given clarithromycin, 500 mg bid. They were followed regularly for changes in daily prednisone dose, spirometry, quality of life, and adverse events. The prednisone dose was tapered in a stepwise fashion at each clinic visit. Within 3 to 6 months of initiation of treatment with clarithromycin, and throughout the 12-month follow-up, two of three patients discontinued prednisone therapy, while the third patient displayed increased spirometry readings and noted an increasingly better quality of life. Pulmonary function tests were stable or improved over this time period, with no reported adverse events, including increased rate of infections. One patient relapsed upon discontinuation of clarithromycin therapy but has since responded to re-initiation of treatment. Long-term oral clarithromycin may have a role in reducing prednisone requirements in elderly patients with prednisone-dependent asthma.

In vitro activities of a new ketolide, ABT-773, alone and in combination with amoxicillin, metronidazole, or tetracycline against Helicobacter pylori

The in vitro activity of ABT-773, a new ketolide, was compared with those of clarithromycin, amoxicillin, metronidazole, and tetracycline against 15 strains of Helicobacter pylori. The MIC of ABT-773 at which 90% of isolates were inhibited was 0.25 microg/ml, which was 3 dilutions higher than that of the most active agent, clarithromycin. Synergy and antagonism were not seen with any combinations. Additive activity was seen with tetracycline, metronidazole, and amoxicillin in 100, 60, and 40% of the combinations, respectively.

Postantibiotic effects and bactericidal activities of clarithromycin-14-hydroxy-clarithromycin, versus those of amoxicillin-clavulanate, against anaerobes

The bactericidal activities and postantibiotic effects (PAE) of clarithromycin-14-hydroxy-clarithromycin and amoxicillin-clavulanate against Bacteroides fragilis and Peptostreptococcus anaerobius were determined. A concentration of twice the MIC resulted in bactericidal activity against four of four and three of four organisms at 24 h with clarithromycin-14-hydroxy-clarithromycin and amoxicillin-clavulanate, respectively. The PAE of clarithromycin-14-hydroxy-clarithromycin was 1.44 to 3.20 h, compared to the less than 1 h of amoxicillin-clavulanate. Clarithromycin-14-hydroxy-clarithromycin possesses good activity against susceptible anaerobes.

Bactericidal activity and postantibiotic effect of levofloxacin against anaerobes

The bactericidal activity and postantibiotic effect (PAE) of levofloxacin against nine anaerobes were determined. Levofloxacin at concentrations of the MIC and twice the MIC was bactericidal at 24 h to five of nine and nine of nine strains, respectively. The PAE of levofloxacin following a 2-h exposure ranged from 0.06 to 2.88 h.

In-vitro synergy of paromomycin with metronidazole alone or metronidazole plus hydroxymetronidazole against Helicobacter pylori

The in-vitro activities of paromomycin and metronidazole alone or paromomycin and metronidazole plus hydroxymetronidazole (2:1 ratio) were studied against 19 Helicobacter pylori isolates using an in-vitro chequerboard technique. Partial synergy was demonstrated for the majority of isolates (11/19) for both combinations tested. When hydroxymetronidazole was added to the parent compound, the number of metronidazole-sensitive isolates demonstrating synergy increased to 5/12, compared with 1/12 for the combination that did not include the metabolite. In metronidazole-resistant isolates there was a shift from an additive effect to partial synergy for the combination containing hydroxymetronidazole. The in-vitro activity of paromomycin and the synergic effect that is achieved in combination with metronidazole and hydroxymetronidazole render paromomycin suitable for further investigation as a treatment option for H. pylori infection.

Pharmacoeconomic analysis of ampicillin-sulbactam versus cefoxitin in the treatment of intraabdominal infections

We conducted a retrospective pharmacoeconomic analysis of a prospective, multicenter, double-blind, randomized, controlled trial comparing the beta-lactamase inhibitor combination ampicillin-sulbactam (96 patients) and the cephalosporin cefoxitin (101) in the treatment of intraabdominal infections. An institutional perspective was adopted for the analysis. The primary outcomes of interest were cure and failure rates, development of new infection, and antibiotic-related adverse events. Epidemiologic data pertaining to outcomes was retrieved primarily from the trial, although results of other published studies were taken into consideration through extensive sensitivity analyses. Data pertaining to potential resource use and economic impact were retrieved mainly from the University Health Consortium and hospital-specific sources. When considering only costs associated with drug acquisition through cost-minimization analysis, a potential savings of $37.24/patient may be realized with ampicillin-sulbactam relative to cefoxitin based on an average 7-day regimen. Outcome data collected for the entire hospitalization during the trial revealed an approximately 9% greater frequency of failure with cefoxitin relative to ampicillin-sulbactam. When considering all outcomes of interest in the initial base-case analysis, a potential cost savings of approximately $890/patient may be realized with ampicillin-sulbactam relative to cefoxitin. In assessing the impact of the significant variability in probability and cost estimates, Monte Carlo analysis revealed a savings of $425/patient for ampicillin-sulbactam over cefoxitin (95% CI -$618 to $1516 [corrected]). Given the model assumptions, our analysis suggests a 78% certainty level that savings will be experienced when ampicillin-sulbactam is chosen over cefoxitin.

Comparison of charcoal- and starch-based media for testing susceptibilities of Legionella species to macrolides, azalides, and fluoroquinolones

We compared growth characteristics of 46 Legionella strains grown on buffered charcoal yeast extract alpha (BCYE alpha) agar and buffered starch yeast extract (BSYE) agar and MICs of macrolides, azalides, and fluoroquinolones for these organisms. Growth was poor and not reproducible on BSYE agar. Growth was excellent on BCYE alpha, and MICs were easy to interpret. BCYE alpha is superior to BSYE for testing susceptibilities of Legionella species by agar dilution.

In vitro activity of clarithromycin alone and in combination with ciprofloxacin or levofloxacin against Legionella spp.: enhanced effect by the addition of the metabolite 14-hydroxy clarithromycin

Clarithromycin is metabolized to an active metabolite, 14-hydroxy clarithromycin. These compounds have demonstrated excellent in vitro activity against Legionella species, with both agents having significantly lower MICs than erythromycin. Using a checkerboard assay, the activity of clarithromycin and its hydroxy metabolite, alone and in combination, was examined against 41 Legionella organisms. The activity of clarithromycin and 14-hydroxy clarithromycin, in a 2:1 ratio, plus ciprofloxacin or levofloxacin was also determined. Activity of the antibiotic combinations was determined by calculating the fractional inhibitory concentration index. An agar dilution method using buffered charcoal yeast extract media was used for susceptibility and synergy testing. An inoculum of 10(4) CFU/spot was used, with all plates incubated at 35 degrees C for 48 h. The MIC90 for clarithromycin or 14-hydroxy clarithromycin alone was 0.5, versus 0.25 microgram/mL for the combination. Additive effects were observed with clarithromycin and its hydroxy metabolite for 61% of the Legionella species, with fractional inhibitory concentration indices ranging from 0.63 to 1.25. The 14-hydroxy metabolite significantly increased the activity of both fluoroquinolone/clarithromycin combinations. Based on these data, in vitro susceptibility testing of agents such as clarithromycin should be reevaluated to account for the activity of active metabolites.

Pharmacokinetics and pharmacodynamics of two multiple-dose piperacillin-tazobactam regimens

The pharmacokinetics and pharmacodynamics of two multiple-dose regimens of piperacillin-tazobactam (3.375 g every 6 h and 4.5 g every 8 h) were evaluated at steady state for 12 healthy adult volunteers. Inhibitory and bactericidal activities for the two regimens were determined with five American Type Culture Collection (ATCC) organisms (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Bacteroides fragilis). The percentage of time that plasma concentrations remained above the MIC (T > MIC) for each organism and dosage regimen was calculated. Areas under the inhibitory (AUIC0-24) and bactericidal activity (AUBC0-24) curves were calculated with the trapezoidal rule by using the reciprocal of the inhibitory and bactericidal titers determined for each dosage regimen. In order to assess the validity of predicted measures of bactericidal (AUC0-24/MBC) and inhibitory (AUC0-24/MIC) activity to determine bacteriological response to beta-lactam antimicrobial agents, AUC0-24/MBC and AUC0-24/MIC values were compared with measured AUBC0-24 and AUIC0-24 values. Total body clearance values were equivalent for piperacillin (183.96 +/- 22.66 versus 181.72 +/- 19.54 ml/min/1.73 m2, P > 0.05) and tazobactam (184.71 +/- 19.89 versus 184.87 +/- 18.35 ml/min/1.73 m2, P > 0.05) following the administration of the 3.375-g-every-6-h and 4.5-g-every-8-h dosages, respectively. Comparison of area under the plasma concentration-time curve (AUC0-24) for piperacillin (967.74 +/- 135.56 microg x h/ml versus 978.88 +/- 140.96 microg x h/ml) and tazobactam (120.14 +/- 15.78 microg x h/ml versus 120.01 +/- 16.22 microg x h/ml) revealed no significant differences (P > 0.05) between the 3.375-g-every-6-h and 4.5-g-every-8-h regimens, respectively. Both regimens provided T > MIC values of > 60% for all organisms tested. Measured values of bactericidal (AUBC) and inhibitory (AUIC) activity were significantly different (P < 0.05) from predicted values (AUC0-24/MBC and AUC0-24/MIC) for all organisms studied with the exception of the bactericidal activity for P. aeruginosa and S. aureus. Additionally, ATCC organisms possessing the same MICs and MBCs exhibited great differences in measured AUBC0-24 and AUIC0-24 values. Reasons for this difference may be inherent differences in organism specific susceptibility.

In vitro synergy testing of clarithromycin and 14-hydroxyclarithromycin with amoxicillin or bismuth subsalicylate against Helicobacter pylori

The activity of clarithromycin-14-hydroxyclarithromycin (2:1 ratio) and bismuth subsalicylate or amoxicillin against Helicobacter pylori was determined by the checkerboard technique in vitro. Clarithromycin-14-hydroxyclarithromycin and amoxicillin resulted in additive effects in 7 of 22 isolates, compared to 14 of 22 isolates when bismuth subsalicylate was substituted for amoxicillin. Synergy was not demonstrated and is probably not responsible for the clinical success of treatment combinations containing clarithromycin.

Intrapulmonary steady-state concentrations of clarithromycin and azithromycin in healthy adult volunteers

The steady-state concentrations of clarithromycin and azithromycin in plasma were compared with concomitant concentrations in epithelial lining fluid (ELF) and alveolar macrophages (AM) obtained in intrapulmonary samples during bronchoscopy and bronchoalveolar lavage from 40 healthy, nonsmoking adult volunteers. Mean plasma clarithromycin, 14-(R)-hydroxyclarithromycin, and azithromycin concentrations were similar to those previously reported. Clarithromycin was extensively concentrated in ELF (range of mean +/- standard deviation concentrations, 34.4 +/- 29.3 microg/ml at 4 h to 4.6 +/- 3.7 microg/ml at 24 h) and AM (480 +/- 533 microg/ml at 4 h to 99 +/- 50 microg/ml at 24 h). The concentrations of azithromycin in ELF were 1.01 +/- 0.45 microg/ml at 4 h to 1.22 +/- 0.59 microg/ml at 24 h, and those in AM were 42.7 +/- 28.7 microg/ml at 4 h to 41.7 +/- 12.1 microg/ml at 24 h. The concentrations of 14-(R)-hydroxyclarithromycin in the AM ranged from 89.3 +/- 52.8 microg/ml at 4 h to 31.3 +/- 17.7 microg/ml at 24 h. During the period of 24 h after drug administration, azithromycin and clarithromycin achieved mean concentrations in ELF and AM higher than the concomitant concentrations in plasma.

Pharmacokinetics of intramuscularly administered aminosidine in healthy subjects

Aminosidine is an older, broad-spectrum aminoglycoside antibiotic that has been shown to be effective in in vitro and animal models against multiple-drug-resistant tuberculosis and the Mycobacterium avium complex. The objective of this randomized, parallel trial was to characterize the single-dose pharmacokinetics of aminosidine sulfate in healthy subjects (eight males, eight females). Sixteen adults (mean [+/- standard deviation] age, 27.6 +/- 5.6 years) were randomly allocated to receive a single, intramuscular aminosidine sulfate injection at a dose of 12 or 15 mg/kg of body weight. Serial plasma and urine samples were collected over a 24-h period and used to determine aminosidine concentrations by high-performance liquid chromatographic assay. A one-compartment model with first-order input, first-order output, and a lag time (Tlag) and with a weighting factor of 1/y2 best described the data. Compartmental and noncompartmental pharmacokinetic parameters were estimated with the microcomputer program WinNonlin. One subject was not included (15-mg/kg group) because of the lack of sampling time data. On average, subjects attained peak concentrations of 22.4 +/- 3.2 microg/ml at 1.34 +/- 0.45 h. All subjects had plasma aminosidine concentrations below 2 microg/ml at 12 h, and all but two subjects (one in each dosing group) had undetectable plasma aminosidine concentrations at 24 h. The dose-adjusted area under the concentration-time curve from 0 h to infinity of aminosidine was identical for the 12- and 15-mg/kg groups (9.29 +/- 1.5 versus 9.29 +/- 2.2 microg x h/ml per mg/kg; P = 0.998). Similarly, no significant differences (P > 0.05) were observed between dosing groups for peak aminosidine concentration in plasma, time to peak aminosidine concentration in plasma, Tlag, apparent clearance, renal clearance, elimination rate constant, and elimination half-life. A significant difference was observed for the volume of distribution (0.35 versus 0.41 liters/kg; P = 0.037) between the 12 and 15 mg/kg dosing groups. Now that comparable pharmacokinetic profiles between dosing groups have been demonstrated, therapeutic equivalency testing via in vitro pharmacokinetic and pharmacodynamic modelling and randomized clinical trials in humans should be conducted.

Therapeutic modalities for mechanical cleansing of the colon

Mechanical cleansing of the colon is an accepted standard of practice prior to colon surgery, and endoscopic and radiographic procedures. Cleansing the bowel prior to these procedures increases the accuracy of the diagnostic procedures and decreases the morbidity and mortality following surgery, where fecal contamination is a concern. Mechanical cleansing agents are sometimes used for acute constipation, but because of the extent and harshness of the evacuation they induce, and because of their adverse effects, they are not used for long-term management of constipation. Dosages vary among products, procedures, and individuals. Manufacturer guidelines should be consulted for proper dosing and administration.

In vitro synergy testing of macrolide-quinolone combinations against 41 clinical isolates of Legionella

Combination antimicrobial therapy against Legionella species has not been well studied. Several quinolones have activity against Legionella strains, which prompted this in vitro search for a synergistic combination with the macrolides. By a checkerboard assay, erythromycin, clarithromycin, and azithromycin, each in combination with ciprofloxacin and levofloxacin, were tested for synergy against 46 isolates of Legionella. The agar dilution method was employed using buffered charcoal-yeast extract media. A final inoculum of 10(4) CFU per spot was prepared from 24-h growth of each isolate. Plates were incubated at 35 degrees C for 48 h. Synergy, partial synergy, additive effect, or indifference was observed for all combinations of antibiotics tested. There was no antagonism observed. Synergy occurred to a significantly greater extent for the clarithromycin-levofloxacin (P = 0.0001) and azithromycin-levofloxacin (P = 0.003) combinations versus erythromycin-levofloxacin. The azithromycin-ciprofloxacin combination demonstrated significantly greater synergy than did either erythromycin-ciprofloxacin (P = 0.003) or clarithromycin-ciprofloxacin (P = 0.001). The newer macrolides clarithromycin and azithromycin may be more active in combination with a fluoroquinolone than is erythromycin.

Piperacillin/tazobactam: a new beta-lactam/beta-lactamase inhibitor combination

OBJECTIVE

To discuss the antimicrobial activity, pharmacokinetics, clinical efficacy, and adverse effect profile of piperacillin/tazobactam, a new beta-lactan/beta-lactamase inhibitor combination.

DATA SOURCES

Literature was identified by MEDLINE search of the medical literature, review of selected references, and data provided by the manufacturer.

STUDY SELECTION

In vitro susceptibility data were surveyed from studies following the methods of the National Committee for Clinical Laboratory Standards. Data evaluating clinical efficacy were selected from all published trials and abstracts. Additional information concerning safety, chemistry, and pharmacokinetics was reviewed.

DATA SYNTHESIS

The antimicrobial activity of piperacillin is enhanced by addition of tazobactam against gram-positive, gram-negative, and anaerobic bacteria. Tazobactam is active against a broad spectrum of plasmid and chromosomally mediated enzymes and has minimal ability to induce class I chromosomally mediated beta-lactamase enzymes. Piperacillin/tazobactam's expanded activity appears encouraging in the treatment of mixed aerobic and anaerobic infections. Direct comparisons of ticarcillin/clavulanate and piperacillin/tazobactam for the treatment of lower respiratory tract infections showed piperacillin/tazobactam to be clinically superior, and in the treatment of skin and soft tissue infections the 2 agents were comparable. For the treatment of intraabdominal infections, piperacillin/tazobactam was at least as effective as imipenem/cilastatin and clindamycin plus gentamicin.

CONCLUSIONS

The combination of tazobactam with piperacillin results in an antimicrobial agent with enhanced activity against most beta-lactamase-producing organisms. Preliminary data indicate that piperacillin/tazobactam has proven clinical efficacy in the treatment of a variety of infections, especially polymicrobic infections.

Development of resistance during antimicrobial therapy: a review of antibiotic classes and patient characteristics in 173 studies

The incidence of emergent resistance and clinical factors affecting its development were evaluated by retrospective review of 173 studies encompassing over 14,000 patients. Eight antibiotic classes and 225 individual treatment regimens were evaluated. Emergent resistance occurred among 4.0% of all organisms and 5.6% of all infections treated. It appeared to be significantly more frequent with penicillin and aminoglycoside monotherapy, with significantly lower rates associated with imipenem-cilastatin, aztreonam, and combination therapy. Clinical failure also appeared to be significantly more likely to occur after emergence of resistance among organisms treated with fluoroquinolones or aminoglycosides. Infections associated with higher resistance rates were cystic fibrosis, osteomyelitis, and lower respiratory tract infections. Resistance was most common in patients in intensive care units or receiving mechanical ventilation. It was also significantly frequent among studies performed in university or teaching hospitals. Organisms associated with high resistance rates were Pseudomonas aeruginosa, Serratia, Enterobacter, and Acinetobacter sp. Factors such as infection type, underlying diseases, type of institution, and specific pathogens warrant consideration when examining emergent resistance.

Bacterial resistance to beta-lactam antibiotics

The historical development of antibiotic resistance, mechanisms of resistance, classification schemes for beta-lactamases, the clinical relevance of resistance, and approaches to overcoming resistance are reviewed. The promise of eradication of infectious diseases has not been fulfilled, in great part owing to the emergence of antibiotic-resistant organisms. Although genes for bacterial resistance may have existed before the clinical use of antibiotics, selection of new resistant strains is driven by the widespread use of antimicrobials in humans and animals. The most commonly prescribed antimicrobials in the United States are the beta-lactam antibiotics, and the most common mechanism of bacterial resistance to these agents is inactivation by beta-lactamase. The clinical and economic consequences of therapeutic failure and relapse--extended hospital stays, increased morbidity and mortality, and the use of potentially more toxic and costly antimicrobial agents--require new strategies to prevent the spread of resistant organisms and to limit future resistance.

In vitro activities of metronidazole and its hydroxy metabolite against Bacteroides spp

Metronidazole is metabolized to two major oxidative products: an acid metabolite and a hydroxy metabolite. While the activity of the acid metabolite is negligible, the activity of the hydroxy metabolite is approximately 65% of the activity of the parent drug. Pharmacokinetic studies of metronidazole and its hydroxy metabolite have shown that the MICs of both compounds remain above the MICs for most anaerobic organisms over an 8-h dosing interval. By a checkerboard assay, the combined activities of metronidazole and the hydroxy metabolite were examined against 4 quality control strains of Bacteroides species. Macrobroth tube dilutions were set up with Wilkins-Chalgren broth. Serial twofold dilutions of each agent were performed to achieve final concentrations ranging from 0.06 to 4.0 micrograms/ml. The MICs for Bacteroides fragilis and B. distasonis were 1.0 microgram/ml for both parent drug and metabolite. For B. thetaiotamicron and B. ovatus, the MICs of metronidazole and the hydroxy metabolite were 1.0 and 2.0 micrograms/ml, respectively. Synergy was determined by calculating the fractional inhibitory concentration (FIC) index. The interpretative criteria for the FIC index were as follows: synergy, FIC < or = 0.5; partial synergy, 0.51 to 0.75; indifference, FIC 0.76 to 4.0; and antagonism, FIC > 4.0. Partial synergy was observed for the four anaerobes tested, with FIC indices ranging from 0.63 to 0.75. On the basis of this data, in vitro susceptibilities to agents such as metronidazole may ultimately require reevaluation to account for active metabolites.

Continuous infusion of loop diuretics in the critically ill: a review of the literature

OBJECTIVES

a) To present the pharmacodynamic concepts behind the administration of loop diuretics via continuous infusion; b) to review the clinical trials and reports in critically ill patients that have described this method of drug delivery; and c) to discuss the data.

DATA SOURCES

Review of MEDLINE and International Pharmaceutical Abstracts from 1966 to the present.

STUDY SELECTION

Study design was not a factor in selecting literature for this review. All studies, case reports, and case series describing infusion of a loop diuretic are included.

DATA EXTRACTION

Cited literature was found in peer-reviewed clinical or basic science journals.

DATA SYNTHESIS

There is a pharmacodynamic basis for the use of a controlled infusion of the loop diuretics in critically ill patients requiring extensive diuresis. Animal and human volunteer studies have demonstrated a clear improvement in efficiency of diuresis by controlled infusion Clinical studies in critically ill patients have demonstrated an improved diuretic response with a controlled infusion. Adverse effects appear to be minimal, and the amount of drug required for effect is less than the required amount for bolus administration.

CONCLUSION

Administration of loop diuretics by continuous intravenous infusion may improve diuresis in critically ill patients who require prompt, controllable diuresis, or who demonstrate "diuretic tolerance" to conventional administration regimens. Despite few, well-designed studies using this method of administration in clinical practice, pharmacodynamic concepts support continuous infusion over bolus administration, including decreased dosage requirements, improved diuretic response and few adverse effects.

Surveillance of treated and untreated funguria in a university hospital

STUDY OBJECTIVE

To determine the influence of treatment on the microbiologic outcome of funguria.

DESIGN

Retrospective case series.

SETTING

A 300-bed tertiary care teaching hospital in a large metropolitan area.

SUBJECTS

141 hospitalized patients, 18 years of age or older, with at least one urine culture positive (> or = 10(2) cfu/ml) for fungi.

INTERVENTIONS

Retrospective review of medical records to determine the microbiologic outcome of funguria.

MAIN RESULTS

Funguria developed rapidly in individuals with known predisposing factors. Urinalysis did not routinely detect the presence of fungi or pyuria. Symptoms such as fever, dysuria, and frequency were generally absent. Funguria persisted whether it was due to Candida albicans or nonalbicans species. There were no statistical differences in the microbiologic outcomes of treated and untreated funguria.

CONCLUSIONS

Funguria is a rapidly developing, often benign and persistent process. Minimizing predisposing risks, such as removing indwelling urinary catheters, is beneficial in its management. Pharmacologic treatment of funguria due to C. albicans or non-albicans species does not influence the microbiologic outcome.

Steady-state pharmacokinetics of cefoperazone and sulbactam in patients with acute appendicitis

OBJECTIVE

To determine the steady-state pharmacokinetics of intravenously administered cefoperazone and sulbactam when given in combination to patients with acute appendicitis.

METHODS

Six patients with normal renal and hepatic function received cefoperazone 2 g with sulbactam 1 g prior to appendectomy and then every 12 hours. Serial blood samples were collected after each patient received at least three doses of cefoperazone/sulbactam.

RESULTS

Cefoperazone and sulbactam could be best described by a two-compartment model. Mean +/- SD values for cefoperazone steady-state volume of distribution (Vssd), elimination half-life (t1/2 beta), clearance (Cl), and area under the curve (AUC0-t) were 19.8 +/- 8.0 L, 3.97 +/- 1.06 h, 62.6 +/- 16.3 mL/min, and 556.9 +/- 122.0 mg.h/L, respectively. Sulbactam Vssd, t1/2 beta, Cl, and AUC0-t were 34.7 +/- 13.9 L, 1.39 +/- 0.4 h, 288.6 +/- 68.2 mL/min, and 64.8 +/- 24.5 mg.h/L, respectively.

CONCLUSIONS

Compared with data from healthy volunteers, cefoperazone exhibited a decreased Cl and increased Vssd and t1/2 beta in patients with acute appendicitis. An increased Vssd also was observed for sulbactam. The disposition of cefoperazone/sulbactam is altered in this group of patients; however, these changes are not likely to warrant a dosage reduction.

Frequency, pathogenicity and microbiologic outcome of non-Candida albicans candiduria

A retrospective review of urine cultures obtained from patients at the University of Illinois Hospital revealed that the frequency of isolation of non-albicans Candida species increased significantly from 1990 to 1991 (p = 0.0003), while the frequency of isolation of Candida albicans species decreased significantly (p = 0.0006). Patients with urine cultures positive for non-albicans Candida species of Torulopsis glabrata during 1991 were identified for review. Sixty-seven patients were eligible for evaluation. Non-albicans candiduria developed in an average of 12 days. Identical fungal species were isolated from the blood following a positive urine culture in only two patients. Twenty patients were treated; candiduria persisted in 9 (45%), while resolution occurred in 11 (55%). The remaining 47 patients were not treated. Non-albicans candiduria persisted in 30 (64%) of these patients and resolved in 15 (32%); in the remaining two patients (4%) the microbiologic outcome was undetermined. The difference in microbiologic outcomes between treated and untreated patients was not significant using the Chi-square test (p = 0.170). Non-albicans candiduria developed rapidly, frequently persisted whether treated or untreated, and rarely progressed to candidemia.

Penetration of clarithromycin into lung tissues from patients undergoing lung resection

The concentrations of clarithromycin and its active principal metabolite, 14-(R)-hydroxy-clarithromycin, were determined in lung tissue obtained during lung resection and compared with concomitant concentrations in plasma. Concentrations of the parent and metabolite were determined by high-performance liquid chromatography. The 15 patients studied were given 500 mg orally every 12 h for a minimum of five doses to achieve steady-state concentrations. The mean concentrations of clarithromycin and 14-(R)-hydroxy-clarithromycin in plasma just prior to the final dose were 1.38 and 0.67 micrograms/ml, respectively, and those 4 h after the final dose (at the time of lung resection) were 1.89 and 0.80 microgram/mL, respectively. The concentrations of the parent and metabolite in lung tissue at the time of lung resection averaged 54.3 and 5.12 micrograms/g, respectively, with a mean calculated ratio of concentrations of the parent to metabolite being 11.3 in lung tissue and 2.4 in plasma. Clarithromycin and its active metabolite are extensively distributed into human lung tissue.

Eikenella corrodens as an intra-abdominal pathogen

Eikenella corrodens is a facultative anaerobe found as normal flora in the oral cavity, gastrointestinal system, and genitourinary tracts. It is most often associated with infections of the head and neck or those due to human bite wounds. However, the organism can be an important pathogen in intra-abdominal infections. Our case report and review of the literature revealed 19 cases of E. corrodens infections of the intra-abdominal cavity. The most common intra-abdominal site of infection was the appendix, noted in seven of the 19 reported cases. Abscess formation was noted in 15 of the 19 reports. The clinical course of the infection in most patients appeared to be indolent, evolving over several days. The majority (11 of 19) of patients described in these cases were less than 25 years old. E. corrodens is usually found concomitantly with other organisms. There appears to be a specific association between E. corrodens and streptococcal species. The drugs of choice for treatment of infections due to E. corrodens are ampicillin, penicillin, or a second generation cephalosporin. This organism is resistant to drugs traditionally active against anaerobic organisms, such as clindamycin and metronidazole.

Central nervous system toxicity associated with meperidine use in hepatic disease

Meperidine-associated central nervous system (CNS) excitatory toxicities are believed to be caused by accumulation of the active metabolite normeperidine. Normeperidine is eliminated by the kidneys and accumulates in patients with renal insufficiency, sickle cell disease, and cancer. In patients with cirrhosis, the metabolism of meperidine is decreased, leading to accumulation of the parent drug and possible CNS depressive effects similar to hepatic encephalopathy. Although the elimination of normeperidine is decreased as well in these patients, the ratio of normeperidine to meperidine is generally low, and the narcotic effects of meperidine usually predominate. This is the first reported case of CNS excitatory toxicities in a patient with alcoholic hepatitis and cirrhosis, and normal renal function. Administration of multiple doses of meperidine in patients with hepatic disease should be discouraged.

Oral antibiotic usage in hospitalized patients

With the introduction of the fluoroquinolones, oral antibiotic usage is becoming an increasingly important issue. The medical record of 119 patients receiving oral antibiotics at a university hospital were reviewed to examine demographics and patterns of usage. The population was predominantly female and below 50 years of age. Urinary tract infections were most common followed by infections of the respiratory tract and skin and skin structure. The majority of usage was empiric in nature. The most commonly prescribed antibiotics were trimethoprim/sulfamethoxazole, cephalexin, and ampicillin/amoxicillin. Monotherapy with an oral agent was observed in 82% of the cases. Intravenous antibiotics were administered prior to oral therapy in 61% of the patients studied. The authors observed a trend from combination intravenous therapy to single-agent oral therapy. Of the patients discharged on an oral antibiotic, 84% received a prescription for the agent originally prescribed for them in the hospital. Tracking of oral antibiotic inpatient use is effective at assessing major trends in usage.

In vivo activity of paromomycin against susceptible and multidrug-resistant Mycobacterium tuberculosis and M. avium complex strains

Encouraged by in vitro results, we have assessed the in vivo activity of paromomycin (PRM) against Mycobacterium tuberculosis, multidrug-resistant (MDR) M. tuberculosis (resistant to isoniazid, rifampin, and streptomycin), and Mycobacterium avium complex in C57BL/6 mice and their beige counterparts. In all these experiments, PRM was effective in preventing mortality from a mycobacterial infection and was significantly more active than the drug-free control (P < 0.0005) in reducing the CFU relative to the mean log CFU in the lungs, livers, and spleens of infected animals. In the drug-susceptible M. tuberculosis experiment, PRM given at 100 and 200 mg/kg of body weight was significantly less active than isoniazid at 25 mg/kg (P < 0.0005) in reducing the mean log CFU in the lungs, livers, and spleens of infected mice. In the MDR M. tuberculosis experiment, PRM given at 200 mg/kg was effective, relative to the drug-free control, in reducing the mean log CFU of an isolate of M. tuberculosis resistant to isoniazid, rifampin, and streptomycin. In the M. avium complex experiment, PRM given at 200 mg/kg was as effective as amikacin at 50 mg/kg in reducing the mean log CFU in the lungs, livers, and spleens of infected mice. On the basis of our experiments, we believe that PRM has promising activity in vivo in the treatment of infections caused by M. tuberculosis, MDR M. tuberculosis, and M. avium complex.

Treatment of cryptosporidial diarrhea in an AIDS patient with paromomycin

OBJECTIVE

To report a case of diarrhea caused by Cryptosporidium in an AIDS patients which was successfully treated with paromomycin.

CASE SUMMARY

An AIDS patient with a 12-month history of cryptosporidial diarrhea unresponsive to other treatment measures was treated with paromomycin 500 mg q6h for 14 days. Before initiating therapy, the patient was experiencing, on average, 20 bowel movements per day and had lost more than 25 kg. After therapy was initiated, the number of bowel movements dropped to 1-2 per day and the patient began to gain weight. The diarrhea recurred when therapy was discontinued. After retreatment for 14 days with paromomycin 500 mg q6h, the diarrhea stopped. The patient has not had a recurrence of Cryptosporidium diarrhea, stool cultures remain negative for Cryptosporidium oocysts, and the patient has regained most of the weight.

DISCUSSION

Literature concerning the use of paromomycin for the treatment of cryptosporidiosis is discussed. A treatment algorithm for the management of cryptosporidiosis in AIDS patients is presented.

CONCLUSIONS

We believe that we have presented a clear example of a case in which paromomycin was effective in treating and eradicating intestinal cryptosporidiosis in an AIDS patient. Paromomycin is the most effective agent available to date for the treatment of this devastating complication of AIDS.

Therapeutic monitoring and pharmacist intervention in a Hansen's disease clinic

OBJECTIVE

To describe the role of the clinical pharmacist in a Hansen's disease (HD, leprosy) clinic and to describe the development, validation, and operation of a dapsone compliance monitoring program.

RATIONALE

HD remains a major, worldwide healthcare problem. Dapsone is the drug of choice for treatment of HD; however, high rates of noncompliance with this agent have been reported by many treatment centers. The assessment of compliance in HD patients is important to help distinguish between treatment failure secondary to noncompliance or to the development of resistance.

SETTING

In the US, the Chicago Regional Hansen's Disease Center at the University of Illinois at Chicago is one of ten centers that provide comprehensive care to patients diagnosed with this condition. This article reviews the clinical pharmacy services and dapsone compliance program in the clinic encompassing the years 1983-93.

RESULTS

The clinical pharmacist provides a variety of clinical services in the clinic as well as coordinating the clinical research program. A pharmacist-generated dapsone compliance program led to improvement in compliance rates and clinical outcome. This improvement in compliance has been sustained over an extended period of time.

CONCLUSIONS

The clinical pharmacy services performed in the HD clinic provide a model for pharmacy involvement in other chronic disease states. The dapsone compliance program has been successful in improving patient care and obtaining reimbursement for clinical pharmacy services.