Activities of WIN-57273, minocycline, clarithromycin, and 14-hydroxy-clarithromycin against Mycobacterium avium complex in human macrophages

MICs of clarithromycin, amikacin, isoniazid, rifabutin, ciprofloxacin, sparfloxacin, ethambutol, and clofazimine were determined for six isolates of Mycobacterium avium complex (MAC) from AIDS patients both by the radiometric method and by an ex vivo model of infection in human macrophages. The median MICs in macrophages were similar or slightly lower than values found in broth, except for amikacin, which had slightly higher MICs inside the cells. Combinations of clarithromycin with other antimicrobial agents showed that clarithromycin-clofazimine and clarithromycin-rifabutin were synergistic on five of six strains while clarithromycin-amikacin and clarithromycin-isoniazid were antagonistic on one and two strains, respectively. The addition of amikacin made the combinations of clarithromycin-clofazimine and clarithromycin-ethambutol synergistic against all the MAC strains. In the macrophage model, the combination of clarithromycinclofazimine (mean survival, 21%) and clarithromycin-rifabutin (mean survival, 29%) showed a strong reduction in viable counts compared with single drugs, while clarithromycin-amikacin was less active than single drugs alone. In general, the addition of amikacin did not improve the activity of the combinations, except for clarithromycin-isoniazid-amikacin (mean survival, 19%), which was significantly more active than either clarithromycin-isoniazid or clarithromycin-amikacin. The use of the macrophage model can suggest new combinations of antimicrobial agents with anti-MAC activity which, on the basis of their in vitro effectiveness, would probably be disregarded for assay in animal models.Mycobacterium avium complex (MAC) infections are very common in AIDS patients, with an estimated prevalence of 43% in the 2 years following the diagnosis of AIDS (25). Therapy for MAC diseases usually involves the combination of several drugs, not only to obtain a greater antimycobacterial effect but also to decrease the probability of selecting resistant mutants (13,15). In some studies, the efficacy of different antimicrobial combinations has been evaluated in vitro (12,34), while in others the activity has been investigated with human macrophages (MP) (33,35,37) or in the murine MP cell line J774 (33,35,36). The Public Health Service Task Force on Prophylaxis and Therapy for MAC recently recommended clarithromycin (CLA)-containing regimens for therapy for disseminated infections by these organisms in AIDS patients (20). At the present time, only for a few reports has the activity of CLA-containing combinations been studied, by in vitro and ex vivo methods, on the same strains (27,28).In this study, we assessed the susceptibility of MAC strains isolated in Italy from AIDS patients (7) by determining the MICs of eight antimicrobial agents both by the radiometric method (11) and by a model of human monocyte-derived MP infection (22,23). This was adopted to evaluate the relationship between the extracellular and intracellular activities of drugs with different capacities for accumulating within MP (31)....

Section: Discussionsupporting

confidence: 77%

In vitro and ex vivo activities of antimicrobial agents used in combination with clarithromycin, with or without amikacin, against Mycobacterium avium

Fattorini

Piersimoni

et al. 1995

“…The MO-1 strain of MAC, used in our previous studies (2,(8)(9)(10)(11)(12), was isolated from a patient with AIDS and used after a single subculture on mycobacterial Middlebrook 7H11 agar (Difco Laboratories, Detroit, Mich.) supplemented with Middlebrook OADC enrichment (Difco). One flat transparent colony was picked and cultivated at 37ЊC in Middlebrook 7H9 broth (Difco) supplemented with ADC enrichment (Difco) in Falcon tissue culture flasks (Becton Dickinson, Oxnard, Calif.).…”

Section: Methodsmentioning

confidence: 99%

Use of normal C57BL/6 mice with established Mycobacterium avium infections as an alternative model for evaluation of antibiotic activity

Cohen

Perronne

Lazard

et al. 1995

Self Cite

Several murine models have been used to evaluate the activities of antimicrobial agents against Mycobacterium avium infection. The main model used is the beige mouse model, but beige mice are expensive and not easily available. Thus, we developed a model of infection in wild C57BL/6 mice. The drugs that exhibited some activity in a previous model of early infection were evaluated in a new model of established infection. Sparfloxacin (50 mg/kg of body weight), ethambutol (50 mg/kg), minocycline (25 mg/kg), and the inhibitor of the cortisol receptors RU-40555 (100 mg/kg) were compared with clarithromycin (50 mg/kg). Treatments were started 5 weeks after the inoculation and were continued for 21 days. Sparfloxacin and RU-40555, which exhibited a moderate activity in the model of early infection, were not effective in this model of established infection. Clarithromycin and combinations with clarithromycin kept their activities against M. avium infection, both in the spleen and in lungs. The present model of established infection of normal C57BL/6 mice is more relevant than the model of early infection for a stringent evaluation of drugs.Disseminated Mycobacterium avium complex (MAC) infection is one of the most common bacterial infections in patients with AIDS (7). The experimental evaluation of the activities of antimicrobial agents against MAC is done in cellular models using macrophages or in animal models. The main animal model used is the beige mouse model (1,5). This model uses mice that are deficient in natural killer cells, providing a kind of immunodeficiency different from that of AIDS in humans. Beige mice, which often develop spontaneous tumors, are expensive and not easily available. Alternative models of mice with cellular immunodeficiency, such as TxCD4 Ϫ mice, Thxb mice, or nude mice, have been suggested (3, 4). TxCD4 Ϫ mice are C57BL/6 mice thymectomized at 4 weeks of age and treated intravenously with anti-CD4 antibodies. Thxb mice are adult thymectomized BALB/c mice that are subjected to lethal whole-body gamma irradiation and are reconstituted with syngeneic bone marrow cells. Nude mice require a sterile environment. These models, difficult to realize, are not easily used for routine investigations. We have shown that the CFU counts of MAC in organs of untreated wild C57BL/6 mice progressively rose after an initial 4-week plateau (10). The bacterial load reaches concentrations higher than 10 8 CFU/g of spleen and higher than 10 7 CFU/g of lung after 6 months of infection, without the spontaneous clearance of bacteria observed with Swiss Webster mice (4-6). The model of early infection of normal C57BL/6 mice may be used for a rapid screening of drugs (8,9,10). In patients with AIDS, MAC infection has a subacute or a chronic clinical course. Thus, a model of established infection of C57BL/6 mice should be more relevant than the model of early infection for mimicking human infection and should represent a more stringent model for the evaluation of antimicrobial agents.Clarithromycin is now considere...

“…Three clinical isolates of M. avium, MO-1, N-93043, and N-92159, obtained from the blood of AIDS patients were used for the in vitro studies. Strain MO-1 was used for the in vivo studies; this strain has been used in our previous studies (3,4,12,13). Cell suspensions with predominantly (Ͼ95%) transparent colony morphologies cultivated in Middlebrook 7H9 broth (Difco Laboratories, Detroit, Mich.) supplemented with ADC enrichment (Difco) were used as described previously (13).…”

Section: Methodsmentioning

confidence: 99%

Activities of roxithromycin against Mycobacterium avium infections in human macrophages and C57BL/6 mice

Struillou

Cohen

Lounis

et al. 1995

Self Cite

The activity of roxithromycin against three clinical isolates of Mycobacterium avium was compared with that of clarithromycin both in a model of infection of human monocyte-derived macrophages and in a model of established infection of C57BL/6 mice. In the cell culture model, roxithromycin and clarithromycin were bactericidal for strains MO-1 and N-92159 and bacteriostatic for strain N-93043. For the three strains, the differences between the intracellular activities of roxithromycin and clarithromycin were not significant after 7 days of treatment. Mice were infected with the MO-1 strain. Drugs were given by gavage at a dosage of 200 mg/kg of body weight 6 days per week for 16 weeks starting 5 weeks after infection. At the end of treatment, clarithromycin was more effective than roxithromycin in lungs; roxithromycin was as effective as clarithromycin in spleens. Thus, the activity of roxithromycin was comparable to that of clarithromycin both in vitro and in vivo.New macrolides are among the most active antibiotics against the Mycobacterium avium complex. Clarithromycin, in particular, has been proven to be effective in treating disseminated M. avium infection in AIDS patients (6, 10) and is now the reference macrolide for this indication. Among other macrolides, although roxithromycin has been shown to be active in vitro against M. avium (1, 2, 11, 14, 15), its activity has been neither compared with that of clarithromycin nor evaluated in vivo. The purpose of the present study was to evaluate the anti-M. avium activity of roxithromycin compared with that of clarithromycin both in vitro in a model of infection of human monocyte-derived macrophages and in vivo in a model of established infection in C57BL/6 mice. MO-1, N-93043, and N-92159, obtained from the blood of AIDS patients were used for the in vitro studies. Strain MO-1 was used for the in vivo studies; this strain has been used in our previous studies (3,4,12,13). Cell suspensions with predominantly (Ͼ95%) transparent colony morphologies cultivated in Middlebrook 7H9 broth (Difco Laboratories, Detroit, Mich.) supplemented with ADC enrichment (Difco) were used as described previously (13). The organisms were passaged through C57BL/6 mice to maintain the virulence of the organisms. MATERIALS AND METHODS Strains of M. avium. Three clinical isolates of M. avium,Antimicrobial agents. Roxithromycin (Roussel-Uclaf, Romainville, France) and clarithromycin (Abbott France, Rungis, Val de Marne, France) were provided as standard powders by the manufacturers. In the cell model, the lactobionate salt of clarithromycin was used and was dissolved in distilled water; roxithromycin was dissolved in methanol and was subsequently diluted in distilled water. For the in vivo studies, suspensions in carboxymethyl cellulose were used for both antibiotics tested.In vitro susceptibility. The MICs were determined by the agar macrodilution method by using Mueller-Hinton agar medium supplemented with 10% Middlebrook OADC enrichment (Difco) (17).Human macrophage model. (i) Human m...