Comparative in-vitro activity of twenty antimicrobial agents against clinical isolates of Mycobacterium avium complex

Single-dose pharmacokinetics of isepamicin in young and geriatric volunteers

Isepamicin is a new aminoglycoside antibiotic with activity against both gram-negative and gram-positive bacteria. The pharmacokinetics of isepamicin were evaluated after a 0.5-hour intravenous infusion of alpha 15-mg/kg dose to groups of young adults and geriatric volunteers. Isepamicin was safe and well tolerated. No adverse events related to the infusion were reported. As age increased, there were increases in the elimination phase half-life (t1/2 beta) and the area under the plasma concentration-time curve extrapolated to infinity (AUC0-infinity), and decreases in systemic (Cl) and renal clearance (Clr). The changes seen in Cl with age were a result of changes in renal function estimated by creatinine clearance (Clcr). There were no apparent correlations between age and maximum plasma concentration (Cmax), half-life of the tau-phase (t1/2 tau), volume of distribution at steady-state (Vdss), or the amount of isepamicin excreted in urine within 24 hours after dose administration (Ae24 hrs). When comparing the elderly (61-80 years old) with the younger (21-60 years) volunteers, the (AUC0-infinity), and t1/2 beta values were higher in the elderly and the Cl and Clr values were lower, but Cmax, t1/2 tau and Vdss were similar in the two age groups. The contribution of the tau-phase to the overall AUC was minimal and similar for the two age groups. Also, there were no gender effects on the pharmacokinetics of isepamicin in both the young and elderly volunteers. These results demonstrate that changes in the pharmacokinetics of isepamicin in the elderly are attributable to changes in renal function, whereas age, per se, is not a significant factor.

In vitro activities of rifabutin, azithromycin, ciprofloxacin, clarithromycin, clofazimine, ethambutol, and amikacin in combinations of two, three, and four drugs against Mycobacterium avium

Multidrug therapy is recommended for treatment of Mycobacterium avium complex (MAC) bacteremia in patients with AIDS. Azithromycin, clarithromycin, rifabutin, ciprofloxacin, ethambutol, clofazimine, and amikacin have all been suggested for use in treating MAC bacteremia, but the most active combinations of these drugs have not been identified, nor has the minimum number of drugs needed for effective therapy been determined. To address the former, the in vitro bactericidal activities of all two-, three-, and four-drug combinations of these seven agents was determined by using 10 blood-derived strains of MAC isolated from patients with AIDS. The activities of the 132 drug combinations were compared by statistical analysis of survival means (analysis of variance) and further evaluated by determining the percentage of strains considered susceptible to each combination. When susceptibility was defined as a decrease in CFU of > or = 2 log10, no two- or three-drug combination and only two four-drug combinations were active against all 10 MAC strains. When a less stringent definition was applied (> or = 1 log10 decrease in CFU), 1 two-drug combinations, 9 three-drug combinations, and 31 four-drug combinations showed activity against all 10 strains. Eighteen selected drug combinations were also tested for intracellular activity in MAC-infected J774 cells. Combinations which contained amikacin as a component were considerably less active against intracellular MAC organisms than against organisms in broth. The opposite result was obtained for the combination of clarithromycin plus clofazimine.

Clarithromycin against Mycobacterium avium complex infections

The turning point in antimicrobial therapy of Mycobacterium avium infections came with the development of two new macrolides, clarithromycin and azithromycin. Controlled clinical trials, the first ever conducted with any agent among patients with M. avium infection, indicated the high efficiency of clarithromycin, in either acquired immune deficiency syndrome (AIDS) patients having a disseminated infection or non-AIDS patients with localized pulmonary disease. Monotherapy with clarithromycin resulted in elimination of bacteremia in almost all patients with disseminated infection, which is inevitably followed by a relapse of bacteremia in patients who survived long enough to reach this event. The strains susceptible to clarithromycin isolated before therapy contained 10(-8) or 10(-9) resistant mutants, and the relapses of bacteremia were caused by multiplication of these pre-existing mutants. Clarithromycin-resistance was associated with a mutation in the 23S rRNA gene. Cross-resistance between clarithromycin and azithromycin was confirmed with laboratory mutants and clinical isolates. At least two methods for determining the susceptibility of the M. avium isolates to clarithromycin are available: one is minimum inhibitory concentration (MIC) determination on Mueller-Hinton agar (pH 7.4) supplemented with 10% Oleic acid-albumin-dextrose catalase, the other is MIC determination in 7H12 broth, also at pH 7.4. The breakpoints for 'susceptible' for these methods are < or = 8.0 micrograms/ml and < or = 2.0 micrograms/ml, respectively. The breakpoints for 'resistant' are > 128 micrograms/ml for the agar method and > 32.0 micrograms/ml for the broth method. The predictability value of MIC determination was confirmed by comparing the test results with the patients' clinical and bacteriological response to therapy. The remaining major problem in the therapy of the M. avium infections is a selection of companion drugs to be used in combination with clarithromycin (or azithromycin) to prevent the emergence of the macrolide-resistance. A number of clinical trials are now in progress to find a solution to this problem.

Type frequency and antimicrobial susceptibility of Mycobacterium avium-intracellulare complex strains isolated in Italy from AIDS and non-AIDS patients

Typing of the glycopeptidolipid antigens performed by thin layer chromatography on 59 Mycobacterium avium-intracellulare (MAC) strains isolated in Italy from AIDS patients showed that the most frequent types were 1, 4, 3, 8, and 21 (24, 19, 14, 14 and 8% of the strains, respectively). Among non-AIDS patients, types 1, 4 and 8 were also frequently found. The antimicrobial susceptibility tested in agar and/or liquid media to a panel of drugs indicated in clofazimine and rifabutin effective agents against both AIDS and non-AIDS strains. The data obtained show that MAC type distribution in Italy appears to be different from that reported for other countries. No major differences in drug susceptibility between AIDS and non-AIDS related strains were found.

New macrolide antibiotics: usefulness in infections caused by mycobacteria other than Mycobacterium tuberculosis

OBJECTIVE

To compare the pharmacology, in vitro activity, and clinical use of the new macrolide antibiotics, azithromycin and clarithromycin, in the treatment of infections caused by mycobacteria other than Mycobacterium tuberculosis.

DATA IDENTIFICATION

An English-language literature search using MEDLINE (1987-1994), Index Medicus (1987-1994), Program and abstracts of the 31st (1991) and 32nd (1992) Interscience Conference on Antimicrobial Agents and Chemotherapy, and bibliographic reviews of related textbooks, review articles, and professional society publications.

STUDY SELECTION

105 articles were selected. In vitro and in vivo reports on the pharmacokinetics, microbiology, pharmacology, and effectiveness of clarithromycin and azithromycin were assessed to compare their effectiveness and safety. Emphasis was placed on the use of these new drugs in treating infections caused by Mycobacterium avium complex, Mycobacterium chelonae, and Mycobacterium fortuitum infections.

RESULTS

A review of the in vitro activity of the new macrolides revealed moderate to very good activity against many strains of mycobacteria other than M. tuberculosis. Early clinical trials show promising results in pulmonary infections, lymphadenitis, cutaneous infections, and disseminated infections.

CONCLUSIONS

The new macrolides, azithromycin and clarithromycin, show great promise for treating infections caused by these acid-fast bacteria. Clarithromycin is recommended as a component of combination therapy for the treatment of M. avium complex infections in patients with AIDS. The development of resistance in patients, particularly when these agents are used alone, has been reported.

Single and double drug susceptibility testing of Mycobacterium avium complex and mycobacteria other than the tubercle (MOTT) bacilli by a micro-dilution broth minimum inhibitory concentration (MIC) method

SETTING

The incidence of Mycobacterioses is increasing annually, especially in patients with AIDS. There is no clear correlation between in vitro drug susceptibility testing of mycobacteria other than the tubercle (MOTT) bacilli and the in vivo response. Although in vitro, MOTT bacilli appear resistant, some patients respond to treatment possibly as a result of a synergistic action between the drugs being used.

OBJECTIVE

To produce a simple method to determine which individual drugs or combinations of drugs will be effective in killing the causative organism.

DESIGN

A broth microdilution method, using microtitre plates, was used to determine the minimum inhibitory concentration (MIC) of the drugs alone and then in combination.

RESULTS

It was found that the MIC values of the test drugs varied between but were constant within each of the species. Mycobacterium xenopi, M. malmoense and M. kansasii showed a large amount of susceptibility while M. avium complex, M. fortuitum and M. chelonae were limited in their response. These results were reproducible. The test was also easy to perform. The drug combination studies showed that each strain of the M. avium complex tested exhibited synergy between different combinations of drugs.

CONCLUSION

This method, therefore, can be used to indicate individual or combinations of drugs that will or will not act upon the Mycobacterium species isolated. The method was also very rapid, giving a result within 7 days.

In vitro activities of free and liposomal drugs against Mycobacterium avium-M. intracellulare complex and M. tuberculosis

We compared MICs and MBCs of various free- and liposome-incorporated antimicrobial agents against several patient isolates of Mycobacterium avium-M. intracellulare complex and certain American Type Culture Collection strains of M. avium, M. intracellulare, and Mycobacterium tuberculosis. Seven of 19 agents were selected for incorporation into liposomes. The MICs of these agents for 50 and 90% of isolates tested (MIC50s and MIC90s, respectively) ranged from 0.5 to 62 micrograms/ml. Members of the M. avium-M. intracellulare complex were resistant to killing by most of the other agents tested in the free form. However, clofazimine, resorcinomycin A, and PD 117558 showed complete killing of bacteria at concentrations ranging from 8 to 31 micrograms/ml, represented as MBC90s. Among the liposome-incorporated agents, clofazimine and resorcinomycin A had the highest killing effects (MBC90s, 8 and 16 micrograms/ml, respectively). Furthermore, both free and liposome-incorporated clofazimine had equivalent growth-inhibitory and killing effects on all American Type Culture Collection strains of M. avium, M. intracellulare, and M. tuberculosis tested. These results show that the antibacterial activities of certain drugs, particularly those of clofazimine and resorcinomycin, were maintained after the drugs were incorporated into liposomes.

Clarithromycin. A review of its pharmacological properties and therapeutic use in Mycobacterium avium-intracellulare complex infection in patients with acquired immune deficiency syndrome

Results from noncomparative and placebo-controlled studies demonstrate the efficacy of clarithromycin in the treatment of disseminated Mycobacterium avium-intracellulare complex (MAC) infection in patients with acquired immune deficiency syndrome (AIDS). Whether given alone or in combination with other antimycobacterial treatments, doses of 500 to 2000mg (typically 1000mg) administered twice daily are effective in controlling bacteraemia in these patients. Clarithromycin has also been shown to improve clinical symptoms of infection and may improve quality of life in AIDS patients with MAC infection. Clarithromycin is generally well tolerated when used in the doses typically required for the treatment of MAC infection (1000 or 2000 mg/day). Gastrointestinal disturbances are the most commonly occurring adverse events and occur most frequently at dosages of 4000 mg/day. Thus, clarithromycin, as monotherapy or in combination with other antimycobacterial agents, is well tolerated and effectively eradicates MAC from the blood in the short term in patients with AIDS: however, short term monotherapy may lead to bacterial resistance, underscoring the importance of long term treatment with a combination of antimycobacterial agents. While the optimal combination regimen to prevent the development of resistance to antimycobacterial agents. While the optimal combination regimen to prevent the development of resistance to antimycobacterial agents by MAC remains to be determined, clarithromycin will almost certainly be a valuable agent in any such combination.

Clarithromycin therapy of experimental Treponema pallidum infections in hamsters

Clarithromycin was shown to be effective therapy for Treponema pallidum infections in hamsters. Clarithromycin therapy was effective when initiated either 1 or 8 days after infection. The delay in initiation of therapy allowed an active infection to develop. The treponemal burden in lymph tissue of treated hamsters was eradicated, as determined by dark-field microscopy and by inoculation of lymph material into susceptible hamsters. Treatments with clarithromycin and the 14-hydroxy metabolite of clarithromycin were equally effective. Therapy with clarithromycin and penicillin was not antagonistic and did not appear to be synergistic when the two drugs were given concurrently. Pharmacokinetic evaluation of clarithromycin in hamsters showed that the doses which produced effective therapy yielded concentrations in serum similar to those routinely achieved in human sera. These findings demonstrate that clarithromycin is effective in treating active or incubating syphilis in the hamster model and could be useful in treating humans.

Activity of clarithromycin against Mycobacterium avium complex infection in beige mice

The activity of clarithromycin alone and in combination with other antimycobacterial agents was evaluated in the beige (C57BL/6J bgj/bgj) mouse model of disseminated Mycobacterium avium complex (MAC) infection. A dose-response experiment was performed with clarithromycin at 50, 100, 200, or 300 mg/kg of body weight administered daily by gavage to mice infected with approximately 10(7) viable MAC. A dose-related reduction in spleen and liver cell counts was noted with treatment at 50, 100, and 200 mg/kg. The difference in cell counts between treatment at 200 and 300 mg/kg was not significant. Clarithromycin at 200 mg/kg of body weight was found to have activity against three additional MAC isolates (MICs for the isolates ranged from 1 to 4 micrograms/ml by broth dilution). Clarithromycin at 200 mg/kg in combination with amikacin, ethambutol, temafloxacin, or rifampin did not result in increased activity beyond that seen with clarithromycin alone. Clarithromycin in combination with clofazimine or rifabutin resulted in an increase in activity beyond that seen with clarithromycin alone. The combination of clarithromycin with clofazimine or rifabutin should be considered for evaluation in the treatment of human MAC infections.

Activities of various quinolone antibiotics against Mycobacterium leprae in infected mice

Previously, pefloxacin and ofloxacin were found to be active against Mycobacterium leprae in vitro, in experimental animals, and in clinical trials of lepromatous leprosy patients. In this study, we compared certain more recently developed fluoroquinolones (lomefloxacin, PD 124816, WIN 57273, temafloxacin, and sparfloxacin) with pefloxacin and ofloxacin in M. leprae-infected mice at doses of 50, 150, and 300 mg/kg given five times weekly. All seven of the fluoroquinolones studies were active against M. leprae; temafloxacin and sparfloxacin were the most active, being fully bactericidal at all three dosage schedules. Additionally, sparfloxacin was found to be fully bactericidal at 15 and 30 mg/kg given five times weekly.

Clarithromycin-ciprofloxacin-amikacin for therapy of Mycobacterium avium-Mycobacterium intracellulare bacteremia in patients with AIDS

A combination of clarithromycin, ciprofloxacin, and amikacin for the treatment of Mycobacterium avium-Mycobacterium intracellulare bacteremia was evaluated in 12 AIDS patients. Mycobacteremia cleared in all patients by 2 to 8 weeks of treatment, and symptoms resolved. Four patients died; all had negative blood cultures until death, and disseminated M. avium-M. intracellulare complex infection was not considered the primary cause of death.

In vitro activity of DNA gyrase inhibitors, singly and in combination, against Mycobacterium avium complex

The in vitro activities of the DNA gyrase inhibitors ciprofloxacin, coumermycin, and novobiocin against 31 clinical isolates of Mycobacterium avium complex were studied using a microdilution technique. Minimal inhibitory concentrations (MICs) were determined in 4 days using Middlebrook 7H9 broth, and minimal bactericidal concentrations (MBCs) were determined by subculturing to Middlebrook 7H10 agar. MICs were: ciprofloxacin, 0.5-greater than 16 (mean, 4.1) micrograms/ml; novobiocin, 4-greater than 128 (mean, 54.7) micrograms/ml; and coumermycin, 2-greater than 16 (mean, 17.5) micrograms/ml. MBCs were usually more than two dilution steps higher than MICs. Checkerboard studies failed to reveal synergistic or antagonistic inhibitory activity of DNA gyrase-A and DNA gyrase-B inhibitors in vitro.

Clarithromycin, a unique macrolide. A pharmacokinetic, microbiological, and clinical overview

The in vitro and in vivo spectrum of antibacterial activity of clarithromycin is summarized and related to its human pharmacokinetics. In vitro studies by several investigators have documented clarithromycin's activity against bacterial agents of respiratory tract infections, skin and soft tissue infections, and sexually transmitted diseases. Clinical cure rates of 52%-83% (pneumonia), 79%-96% (bronchitis), 82%-96% (pharyngitis), 58% (sinusitis), and 78% (skin/skin-structure infections) have been reported in patients receiving clarithromycin in comparative trials. Respective bacteriologic eradication rates in clarithromycin recipients have been reported as 57%-89%, 79%-96%, 88%-100%, 89%, and 90%. In vitro and in vivo studies suggest that clarithromycin, when combined with its major human metabolite, 14-hydroxyclarithromycin, is also effective against Haemophilus influenzae. A New Drug Application claiming efficacy in the treatment of lower respiratory tract infection, sinusitis, pharyngitis, and skin and skin-structure infections caused by susceptible pathogens has been filed with the Food and Drug Administration (FDA). This review summarizes relevant pharmacokinetic, microbiological, and clinical data for clarithromycin.

Evaluation of the bactericidal activity of temafloxacin

Although the fluoroquinolones share many properties, these agents differ in their ability to kill the same bacterial strain. The bactericidal activity of temafloxacin against a number of pathogens has been compared with that of other fluoroquinolones by determination of minimal bactericidal concentration, time-kill kinetics, and postantibiotic effect. Studies have demonstrated that temafloxacin has equivalent or superior ability to kill when compared with other fluoroquinolones. Temafloxacin, ciprofloxacin, and PD 117558 were more active than other fluoroquinolones against Mycobacterium avium complex, with 90% minimal bactericidal concentrations (MBC90S; 8-16 micrograms/mL) four- to eightfold greater than 90% minimal inhibitory concentrations (MIC90S; 2 micrograms/mL). Against Chlamydia trachomatis the MIC90 and MBC90 of temafloxacin were both 0.25 microgram/mL; ciprofloxacin was less active (MBC90 twice the MIC90), and norfloxacin was least active. Temafloxacin demonstrated more rapid killing kinetics than did ciprofloxacin or ofloxacin at all concentrations tested against Streptococcus pyogenes. Findings were similar against Streptococcus pneumoniae at antibiotic concentrations of 1-2 micrograms/mL. Similar time-kill curves against Escherichia coli were observed for temafloxacin, ciprofloxacin, and difloxacin. Time-kill kinetics of temafloxacin against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) were superior to those of ciprofloxacin and ofloxacin. Postantibiotic effect with temafloxacin against Legionella pneumophila showed a considerable delay in regrowth, and temafloxacin delayed regrowth of MRSA and MSSA to a greater extent than did ciprofloxacin or ofloxacin. By the three methods used in the studies to assess bactericidal activity that are currently published, temafloxacin had equivalent or superior activity to the comparative fluoroquinolones tested. Other organisms remain to be tested and the significance of these findings determined in clinical studies.

In vitro testing of clarithromycin in combination with ethambutol and rifampicin against Mycobacterium avium complex

The activity of clarithromycin in combination with ethambutol and rifampicin was tested at concentrations achievable in serum against 20 strains of Mycobacterium avium complex. The combination of clarithromycin plus rifampicin showed inhibition of 11 of the strains and bactericidal synergism against seven of the strains. When ethambutol was added, a bactericidal effect was observed against 16 strains. On the basis of these in vitro data it seems that clarithromycin in combination with rifampicin and ethambutol may be a promising drug for the effective treatment of infections caused by M. avium complex.

Effect of pH on the in vitro potency of clarithromycin against Mycobacterium avium complex

Employing 7H11 agar medium at pH 6.6, the MICs of clarithromycin for 50% (MIC50) and 90% (MIC90) of 19 strains of Mycobacterium avium complex were 8 and 16 micrograms/ml, respectively. However, the MICs were 2 to 3 log2 dilutions lower in the 7H11 medium adjusted to pH 7.4, and the MICs on 10% OADC (oleic acid-albumin-dextrose-catalase)-enriched Mueller-Hinton agar at pH 7.3 were also 2 log2 dilutions lower than those measured on 7H11 agar at pH 6.6. Therefore, clarithromycin is more active at a physiologic than at an acidic pH.

Activities of sparfloxacin, azithromycin, temafloxacin, and rifapentine compared with that of clarithromycin against multiplication of Mycobacterium avium complex within human macrophages

The activities of sparfloxacin, azithromycin, temafloxacin, and rifapentine against two virulent strains of the Mycobacterium avium complex isolated from patients with AIDS were evaluated in a model of intracellular infection and were compared with that of clarithromycin. Human monocyte-derived macrophages were infected with the M. avium complex at day 6 of culture. The intracellular CFU was counted 60 min after inoculation. The intracellular and supernatant CFU was counted on days 4 and 7 after inoculation. The concentrations used, which were equal to peak levels in serum, were 10 micrograms of rifapentine per ml (MICs for the two strains, 4 and 16 micrograms/ml), 4 micrograms of clarithromycin per ml (MICs, 8 and 4 micrograms/ml), 1 microgram of azithromycin per ml (MICs, 32 and 16 micrograms/ml), 4 micrograms of temafloxacin per ml (MICs, 2 and 16 micrograms/ml), and 1 microgram of sparfloxacin per ml (MICs, 0.5 and 2 micrograms/ml). Compared with controls on day 7 after inoculation, clarithromycin (P less than 0.001), sparfloxacin (P less than 0.001), and azithromycin (P less than 0.001 for the first strain, P less than 0.02 for the second) slowed intracellular replication. Rifapentine (P less than 0.001) and temafloxacin (P less than 0.001) slowed intracellular replication of the first strain but not of the second strain. Azithromycin plus sparfloxacin was as effective as sparfloxacin alone. In this macrophage model, sparfloxacin or clarithromycin (difference not significant) exhibited a better efficacy than rifapentine, azithromycin, or temafloxacin against intracellular M. avium complex infection.

Newly documented antimicrobial activity of quinolones

The improved antimicrobial activity of newer fluoroquinolones and novel applications recently found for the drugs already marketed are reviewed. Several new compounds are more active against gram-positive bacteria than the presently marketed fluoroquinolones. WIN 57273, the most potent compound in vitro on a weight basis, is 16 to 128 times more active than ciprofloxacin against various staphylococci, streptococci, Enterococcus spp., Corynebacterium spp., Listeria monocytogenes and Bacillus spp. BMY 40062, PD 117558, PD 127391, sparfloxacin, temafloxacin and tosufloxacin also show enhanced in vitro efficacy against these species. These drugs also possess increased activity against various anaerobes, notably Clostridium perfringens, Clostridium difficile and the Bacteroides fragilis group. Mycobacterium tuberculosis, rapidly growing mycobacteria other than Mycobacterium chelonae, and Mycobacterium leprae are often susceptible to quinolones displaying bactericidal activity which is potentially useful for curing difficult-to-treat mycobacteriosis. In addition, a number of new products, notably those containing a cyclopropyl group, are more active than reference fluoroquinolones against Mycobacterium leprae. Sparfloxacin, BMY 40062 and WIN 57273 compare favorably with older fluoroquinolones in the killing of intracellular Legionella spp., and several of the newer compounds have greater antichlamydial potency. Improved antibacterial activity has also been found against Mycoplasma hominis, Ureaplasma urealyticum, Acinetobacter spp. and Pseudomonas maltophilia. By contrast, the newer quinolones have similar or less activity against Pseudomonas aeruginosa and Enterobacteriaceae. Recently, pefloxacin, ofloxacin and ciprofloxacin were found to be active against protozoa, including Plasmodium spp., Trypanosoma cruzi and Leishmania donovani, but not against Toxoplasma gondii. In the near future, more specific research testing unusual pathogens may lead to the identification of quinolones with more selective activity.