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M E Klepser

Publications and source records attributed to M E Klepser.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of Etest, chequerboard dilution and time-kill studies for the detection of synergy or antagonism between antifungal agents tested against Candida species.

Currently, there is considerable debate regarding the best in vitro method for testing antifungal combinations against Candida spp. In this study, we compared the results obtained by chequerboard dilution, time-kill studies and Etest for several antifungal combinations against Candida spp. Three Candida albicans isolates (fluconazole MICs of 1.0, 32 and >256 mg/L) and three non-albicans Candida isolates (C. glabrata, C. tropicalis and C. krusei) were tested in RPMI 1640 medium. By chequerboard testing, the majority of antifungal combinations were found to be indifferent. Notably, antagonism was identified by time-kill studies and by Etest for combinations of amphotericin B-fluconazole, but it was not detected by the chequerboard method. Pre-exposure of isolates to fluconazole did not affect results of the Etest or chequerboard method, but it did increase the frequency of antagonism noted by time-kill methods. This study indicates that chequerboard dilution testing in RPMI medium may not reliably detect the attenuation of amphotericin B activity. Of the three methods, Etest was the simplest to use and yielded reproducible results for testing antifungal combinations.

Amphotericin B↗
PubMed2001

Evaluation of amphotericin B and flucytosine in combination against Candida albicans and Cryptococcus neoformans using time-kill methodology.

In this study, time-kill methods were used to evaluate the antifungal activity of amphotericin B and flucytosine, alone and in combination, against six isolates of Candida albicans and Cryptococcus neoformans. Five regimens were tested against each isolate: (1) flucytosine, (2) low-dose amphotericin B, (3) high-dose amphotericin B, (4) low-dose amphotericin B plus flucytosine, and (5) high-dose amphotericin B plus flucytosine. Low-dose amphotericin B and flucytosine, administered alone and simultaneously, demonstrated fungistatic activity against all sample isolates except C. albicans 90028, in which fungicidal activity was detected with the combination. High-dose amphotericin B, alone and in combination, resulted in a rapid fungicidal effect in all isolates. In both the low and high-dose combinations, indifferent activity was demonstrated against all tested isolates. By virtue of the absence of an antagonistic interaction between these two agents, complementary pharmacokinetic profiles, and non-overlapping toxicities, continued clinical use of these agents in combination may be considered.

Amphotericin B↗
PubMed2001

Comparative bactericidal activities of ciprofloxacin, clinafloxacin, grepafloxacin, levofloxacin, moxifloxacin, and trovafloxacin against Streptococcus pneumoniae in a dynamic in vitro model.

Several new quinolones that exhibit enhanced in vitro activity against Streptococcus pneumoniae have been developed. Using a dynamic in vitro model, we generated time-kill data for ciprofloxacin, clinafloxacin, grepafloxacin, levofloxacin, moxifloxacin, and trovafloxacin against three isolates of quinolone-susceptible S. pneumoniae. Three pharmacokinetic profiles were simulated for each of the study agents (0.1, 1, and 10 times the area under the concentration-time curve [AUC]). Target 24-h AUCs were based upon human pharmacokinetic data resulting from the maximal daily doses of each agent. Ciprofloxacin was the least active agent against all three isolates. With regimens that simulated the human 24-h AUC, ciprofloxacin resulted in an initial, modest decline in the numbers of CFU per milliliter; however, by 48 h the numbers of CFU per milliliter returned to or exceeded the starting inoculum. At the AUC, levofloxacin resulted in variable bacteriostatic and bactericidal activities against the isolates. The remaining agents yielded bactericidal (99.9% reduction) activity by 48 h with regimens that simulated the AUC. At 0.1 time the AUC ciprofloxacin and levofloxacin produced no inhibitory effect, grepafloxacin exhibited bacteriostatic activity, trovafloxacin had mixed static and cidal activities, and clinafloxacin and moxifloxacin caused significant reductions in the numbers of CFU per milliliter by 48 h. All six agents produced cidal activity at 10 times the AUC. In this dynamic in vitro model of infection, the quinolones demonstrated various degrees of activity against S. pneumoniae. The rank order of activity, with respect to bactericidal effect, was ciprofloxacin (least active) << levofloxacin < grepafloxacin, trovafloxacin < clinafloxacin and moxifloxacin (most active). The rank order of the agents with respect to the selection of resistance was ciprofloxacin (most likely) > grepafloxacin, moxifloxacin, and trovafloxacin > levofloxacin > clinafloxacin.

Anti-Infective Agents↗
PubMed2001

Antifungal resistance among Candida species.

Isolation of Candida sp less susceptible to traditional therapies and recovery of increasingly resistant isolates during antifungal therapy are growing problems. It is important for clinicians to be aware of trends and mechanisms responsible for the expression of resistance.

Antifungal Agents↗
PubMed2000

Comparison of oral immediate-release (IR) and extended-release (ER) metronidazole bactericidal activity against Bacteroides spp. using an in vitro model of infection.

We used an anaerobic infection model capable of simulating human serum pharmacokinetic parameters (C(max), C(min), half-life, and AUC) to compare the activity of oral immediate-release (IR) and extended-release (ER) MTZ formulations. Four oral regimens of MTZ plus a control regimen were simulated in the model: [i] (IR) 500 mg q8h, [ii] ER 750 mg q12h, [iii] ER 750 mg q24h, and [iv] ER 1500 mg q24h. Two clinical Bacteroides fragilis isolates (MICs 0.5, 4.0 microg/mL) and two non-fragilis Bacteroides isolates (MICs 0.5, 3 microg/mL) were studied. All four oral MTZ regimens exhibited rapid, bactericidal activity (> or =3-log(10) decrease from the starting inoculum) within 12 h against both fragilis and non-fragilis Bacteroides isolates. Overall, no appreciable difference in the rate of bacteria killing was noted among the four MTZ formulations against either B. fragilis isolates (P = 0.907, 0.737) or non-fragilis isolates (P = 0.809, 0.768). We conclude that ER MTZ dosed at 12 or 24-h intervals possesses equivalent bactericidal activity to standard IR MTZ dosed every eight hours against susceptible Bacteroides spp.

Administration, Oral↗
PubMed2000

In vitro pharmacodynamic characteristics of flucytosine determined by time-kill methods.

Two Candida albicans isolates, three non-albicans Candida isolates (Candida glabrata, Candida krusei, and Candida tropicalis), and one Cryptococcus neoformans isolate were evaluated by time-kill methods to characterize the relationship of flucytosine concentrations to antifungal activity and the duration of the post-antifungal effect (PAE). Against Candida and Cryptococcusisolates, flucytosine at concentrations > 1 x MIC exhibited fungistatic (</=99% reduction in CFU) activity over a 24-h time-period. The rate and extent of fungistatic activity of flucytosine against all isolates was generally not increased when 5-FC concentrations exceeded 4 x MIC. A notable PAE was detected for flucytosine against both Candida and Cryptococcus species that persisted 2 to 4 h. These in vitro data suggest that flucytosine is predominately a concentration-independent fungistatic agent at clinically achieved serum concentrations. This pharmacodynamic characteristic coupled with the persistent PAE and the relatively long half-life of flucytosine in humans (> 5 h), suggests lower daily dosing may possible without loss of antifungal efficacy.

Antifungal Agents↗
PubMed2000

Postantifungal effects of echinocandin, azole, and polyene antifungal agents against Candida albicans and Cryptococcus neoformans.

The postantifungal effect (PAFE) of fluconazole, MK-0991, LY303366, and amphotericin B was determined against isolates of Candida albicans and Cryptococcus neoformans. Concentrations ranging from 0. 125 to 4 times the MIC were tested following exposure to the antifungal for 0.25 to 1 h. Combinations of azole and echinocandin antifungals (MK-0991 and LY303366) were tested against C. neoformans. Fluconazole displayed no measurable PAFE against Candida albicans or Cryptococcus neoformans, either alone or in combination with either echinocandin antifungal. MK-0991, LY303366, and amphotericin B displayed a prolonged PAFE of greater than 12 h against Candida spp. when tested at concentrations above the MIC for the organism and 0 to 2 h when tested at concentrations below the MIC for the organism.

Amphotericin B↗
PubMed2000

Evaluation of voriconazole pharmacodynamics using time-kill methodology.

Voriconazole is an investigational azole antifungal agent with activity against a variety of fungal species, including fluconazole-susceptible and -resistant Candida species and Cryptococcus neoformans. In this study, we employed in vitro time-kill methods to characterize the relationship between concentrations of voriconazole and its fungistatic activity against Candida albicans, Candida glabrata, Candida tropicalis, and C. neoformans. Isolates were exposed to voriconazole concentrations ranging from 0.0625 to 16 times the MIC, and the viable colony counts were determined over time. The 50 and 90% effective concentrations (EC(50) and EC(90), respectively) were determined at 8, 12, and 24 h following the addition of voriconazole. At each time point, near-maximal fungistatic activity, as indicated by the EC(90), was noted at a drug concentration of approximately three times the MIC. Additionally, EC(50) and EC(90) did not change over time, thus suggesting that the rate of activity was not improved by increasing concentrations. Voriconazole exhibits non-concentration-dependent pharmacodynamic characteristics in vitro.

Antifungal Agents↗
PubMed2000

Novel triazole antifungal agents.

The risk of opportunistic infections is greatly increased in patients who are immunocompromised due to AIDS, cancer chemotherapy and organ or bone marrow transplantation. Candida albicans is often associated with serious systemic fungal infections, however other Candida species such as Candida krusei, Candida tropicalis and Candida glabrata, as well as Cryptococcus neoformans and filamentous fungi such as Aspergillus, have also emerged as clinically significant fungal pathogens. Two triazole antifungal agents, fluconazole and itraconazole, were introduced over a decade ago and since then have been used extensively for the prophylaxis and treatment of a variety of fungal infections. Although both drugs are effective and have their place in therapy, limitations regarding the utility of these agents do exist. For example, fluconazole is not effective for the prophylaxis or treatment of Aspergillus species and has limited activity against C. krusei and C. glabrata. The use of itraconazole has been limited secondary to concerns regarding unpredictable bioavailability. The rising incidence of fungal infections and the reported increase of non-albicans candidal infections noted over the past two decades highlight the need for new antifungal agents with improved spectra of activity. Several new triazole agents are in various phases of preclinical and clinical trials and may be available for human use in the near future. Three such agents voriconazole, posaconazole and ravuconazole are reviewed and compared with existing agents.

AIDS-Related Opportunistic Infections↗
PubMed2000

Assessment of patients' perceptions and beliefs regarding herbal therapies.

We evaluated the demographics and beliefs regarding safety and efficacy of herbal therapy among individuals in Iowa and assessed the willingness to discuss the use of these products with health care providers. We distributed 1300 surveys to two random samples: patients attending eight clinics, and residents of the state (mailing). Data were categorized according to herb use and compared between users and nonusers. The response rate was 61% (794 people), with 41.6% of respondents reporting herb use. They were predominately white women and were likely to have had education beyond high school (p<0.05). Their use of prescription drugs was high (p<0.05). Although users rated safety and efficacy of herbs higher than nonusers (p<0.05), both groups believed that health care providers should be aware of use and would provide this information.

Adult↗
PubMed2000

Comparison of the serum and intracellular pharmacokinetics of azithromycin in healthy and diabetic volunteers.

STUDY OBJECTIVE: To compare serum and intracellular pharmacokinetics of azithromycin in healthy volunteers and patients with diabetes. DESIGN: Open-label, parallel study. SETTING: Clinical research center. SUBJECTS: Twelve patients with diabetes and 12 healthy volunteers. INTERVENTIONS: Subjects were given a single 500-mg dose of azithromycin followed by 250 mg/day for 2 days. Blood samples were obtained just before and after the third dose for up to 24 hours for serum and 168 hours for intracellular measurement of azithromycin. MEASUREMENTS AND MAIN RESULTS: Pharmacokinetic parameters were calculated by noncompartmental methods and compared with a t test. The groups did not differ in maximum concentration, time to maximum concentration, or area under the concentration-time curve in serum or polymorphonuclear cells (PMNs). Differences in the PMN:serum ratio were observed at the 24-hour time point (healthy 1209 +/- 432, diabetic 859 +/- 286, p=0.051). CONCLUSION: In general, the pharmacokinetics of azithromycin are comparable in diabetics and healthy volunteers. Accumulation of drug in macrophages was slightly lower in patients.

Adult↗
PubMed1999

The changing face of nosocomial candidemia: epidemiology, resistance, and drug therapy.

The changing epidemiology and therapy of nosocomial candidemia are discussed. The frequency of nosocomial bloodstream infections by Candida species has risen dramatically in the past two decades. The arrival of antifungal drugs with better tolerability than conventional amphotericin B has resulted in widespread use of systemic antifungal therapy. With the introduction of new systemic antifungals, however, there have been major shifts in the epidemiology of candidal bloodstream infections toward species with less susceptibility to the available antifungal agents. Reports of in situ antifungal resistance are also becoming more common. Strategies for preventing the emergence of resistance have been suggested but have not undergone clinical trials. Antifungal susceptibility testing is becoming an increasingly important tool in the management of nosocomial candidemia. Treatments that have been undergoing investigation for use in these infections include combination therapies, lipid-based amphotericin B formulations, cytokines as adjuvant therapy, and novel antifungal agents such as voriconazole, SCH56592, and echinocandins. New antifungals in development may offer enhanced activity against pathogenic Candida species with less toxicity than amphotericin B. Antifungal susceptibility testing will play a major role in determining the treatment of resistant infections.

Antifungal Agents↗
PubMed1999

Unsafe and potentially safe herbal therapies.

Unsafe and potentially safe herbal therapies are discussed. The use of herbal therapies is on the rise in the United States, but most pharmacists are not adequately prepared educationally to meet patients' requests for information on herbal products. Pharmacists must also cope with an environment in which there is relatively little regulation of herbal therapies by FDA. Many herbs have been identified as unsafe, including borage, calamus, coltsfoot, comfrey, life root, sassafras, chaparral, germander, licorice, and ma huang. Potentially safe herbs include feverfew, garlic, ginkgo, Asian ginseng, saw palmetto, St. John's wort, and valerian. Clinical trials have been used to evaluate feverfew for migraine prevention and rheumatoid arthritis; garlic for hypertension, hyperlipidemia, and infections; ginkgo for circulatory disturbances and dementia; ginseng for fatigue and cancer prevention; and saw palmetto for benign prostatic hyperplasia. Also studied in formal trials have been St. John's wort for depression and valerian for insomnia. The clinical trial results are suggestive of efficacy of some herbal therapies for some conditions. German Commission E, a regulatory body that evaluates the safety and efficacy of herbs on the basis of clinical trials, cases, and other scientific literature, has established indications and dosage recommendations for many herbal therapies. Pharmacists have a responsibility to educate themselves about herbal therapies in order to help patients discern the facts from the fiction, avoid harm, and gain what benefits may be available.

Drug Interactions↗
PubMed1999

In vitro pharmacodynamic properties of MK-0991 determined by time-kill methods.

MK-0991 has demonstrated activity against a variety of fungal pathogens. We evaluated the MIC endpoint for MK-0991 by reading the endpoint using three methods and comparing these results with minimum fungicidal concentrations and electron micrographs. The concentration that resulted in 80% inhibition of fungal growth compared with control, similar to the endpoint for the azole antifungal agents, provided the most consistent results. Additionally, we investigated the time-kill properties of this agent against two isolates each of Candida albicans, Candida glabrata and Candida tropicalis at concentrations ranging from 0.125 x MIC to 16 x MIC. Kill curves were performed using RPMI buffered with morpholine propanesulfonic acid as growth media. Samples were obtained at predetermined time points over 24 h and plated for colony counting. Fungicidal activity was observed with one isolate of C. albicans, two isolates of C. glabrata, and one isolate of C. tropicalis. MK-0991 displayed concentration-dependent activity, which was fungicidal or fungistatic depending on the isolate tested.

Anti-Bacterial Agents↗
PubMed1999

Evaluation of low-dose, extended-interval clindamycin regimens against Staphylococcus aureus and Streptococcus pneumoniae using a dynamic in vitro model of infection.

We have previously described the activity of low-dose clindamycin in extended-interval dosing regimens by determination of bactericidal titer in serum. In this study, we used a one-compartment in vitro dynamic infection model to compare the pharmacodynamics of clindamycin in three intravenous-dosing regimens (600 mg every 8 h [q8h], 300 mg q8h, and 300 mg q12h) against three clinical isolates of Staphylococcus aureus and two clinical isolates of Streptococcus pneumoniae. Test organisms were added to the central compartment of the model to yield a starting inoculum of 10(6) CFU/ml. Clindamycin was injected as a bolus into the central compartment at appropriate times over 48 h to simulate the q8h or q12h dosing regimens. Drug-free culture medium was then pumped through the system to mimic a half-life of 2.4 h. At predetermined time points during the experiment, samples were removed from the central compartments for colony count determination and drug concentration analysis. The rates of killing did not significantly differ among the three clindamycin dosing regimens against either S. aureus or S. pneumoniae (P = 0.88 or 0.998, respectively). Likewise, no significant differences in activities were detected among the three regimens against staphylococci (P = 0.677 and 0.667) or pneumococci (P = 0.88 and 0.99). Against an S. aureus isolate exhibiting inducible macrolide-lincosamide-streptogramin B resistance, none of the three clindamycin regimens prevented regrowth of the resistance phenotype in the model. In this model, clindamycin administered at a low dose in an extended-interval regimen (300 mg q12h) exhibited antibacterial activity equivalent to that of the 300- or 600-mg-q8h regimen.

Anti-Bacterial Agents↗
PubMed1998

Strategies in the treatment of penicillin-resistant Streptococcus pneumoniae.

The epidemiology, resistance mechanisms, susceptibility testing, treatment, prevention, and clinical importance of penicillin-resistant Streptococcus pneumoniae (PRSP) infection are discussed. PRSP is an established presence in the United States, with some geographic areas reporting decreased susceptibility in up to half of isolates. The mechanism of resistance to beta-lactam antibiotics in S. pneumoniae is genetic changes resulting in decreased binding of drug to the bacterial cell wall. Emerging PRSP strains have necessitated testing as a tool in selecting drugs for treating life-threatening infections. Opinions differ on how to treat these infections empirically. Non-life-threatening infections, such as otitis media, are still often treated successfully with amoxicillin, amoxicillin-clavulanate potassium, or a third-generation cephalosporin. Currently recommended initial treatment of pneumococcal pneumonia in otherwise healthy patients requiring hospitalization consists of cefuroxime, ceftriaxone, or cefotaxime; some authors continue to emphasize injectable penicillin. Once the mainstay of empirical treatment of pneumococcal meningitis, penicillin has largely been abandoned in favor of cefotaxime or ceftriaxone. Vaccination remains an underutilized strategy in atrisk populations. The clinical importance of penicillin resistance among pneumococci is still uncertain. Changing patterns in the susceptibility of S. pneumoniae to penicillin make selection of appropriate therapy increasingly difficult. Key considerations are the site of infection and the level of resistance.

Anti-Bacterial Agents↗