Efficient intermittent rifapentine-moxifloxacin-containing short-course regimen for treatment of tuberculosis in mice.

Long-half-life drugs raise the hope of once-a-week administration of antituberculous treatment. In a previous study with the murine model of tuberculosis, the most active intermittent regimen which contained rifapentine (RFP), isoniazid (INH), and moxifloxacin (MXF) given once a week during 5.5 months, preceded by 2 weeks of daily treatment with INH, rifampin (RIF), pyrazinamide (PZA), and MXF, was less active than the standard 6-month daily RIF-INH-PZA regimen. We evaluated with the same model similar regimens in which we increased the dosing of rifapentine from 10 to 15 mg/kg of body weight and of moxifloxacin from 100 to 400 mg/kg. Mice infected intravenously by 6.2 x10(6) CFU of Mycobacterium tuberculosis H37Rv were treated 2 weeks later when infection was established. After 6 months of treatment, all mice had negative lung culture. After 3 months of follow-up, no relapse occurred in the two groups that received moxifloxacin at 400 mg/kg, whatever the dosage of RFP, and in the group receiving the standard RIF-INH-PZA control regimen. In contrast, in the two groups receiving moxifloxacin at a lower dosage, the relapse rate was significantly higher (13% in mice receiving RFP at 15 mg/kg and 27% in those receiving RFP at 10 mg/kg). Finally, the fully intermittent once-a-week regimen (26 drug ingestions) of INH, RFP (15 mg/kg), and MXF (400 mg/kg) led to a relapse rate of 11%. In conclusion, when used at high dosage, rifapentine and moxifloxacin are very efficient when combined with isoniazid in a once-a-week treatment in mouse tuberculosis.

Impact of iron loading on the activity of isoniazid or ethambutol in the treatment of murine tuberculosis.

OBJECTIVE: To assess the impact of iron loading on the activity of isoniazid and ethambutol in the treatment of murine tuberculosis. DESIGN: Iron-loaded and iron-normal female Balb/C mice infected with 1.5 x 10(7) colony forming units of Mycobacterium tuberculosis were treated with either isoniazid or ethambutol for 28 days. RESULTS: For both treatments, the outcome was impaired by the iron loading: bactericidal activity of isoniazid was partially but significantly reduced and ethambutol bactericidal activity was totally inhibited. CONCLUSION: The treatment of tuberculosis in patients with iron loading should be longer than for normal patients or should contain an additional drug.

Effectiveness of once-weekly rifapentine and moxifloxacin regimens against Mycobacterium tuberculosis in mice.

Mice infected with 1.6 x 10(7) CFU of Mycobacterium tuberculosis were treated 14 days later for 6 months with a regimen of once-weekly 10 mg of rifapentine and 75 mg of isoniazid per kg of body weight supplemented with either 150 mg of streptomycin per kg or 100 mg of moxifloxacin per kg during either both the 2-week daily initial and once-weekly continuation phases or only in the daily 2-week initial phase. On completion of treatment, all lung cultures were negative, except for three mice, each with a single colony: two whose rifapentine-isoniazid regimen was supplemented with streptomycin during the whole course of therapy and one whose rifapentine-isoniazid regimen had no initial daily phase, but was supplemented with streptomycin and moxifloxacin during the whole course of therapy. After 3 months of follow-up, positive lung cultures were obtained from 61 and 56% of mice supplemented with streptomycin during either the full course of therapy or only the daily 2-week initial phase, respectively, and 15 and 50% of mice supplemented with moxifloxacin during either the full course of therapy or only the daily 2-week initial phase, respectively. These results suggest that moxifloxacin has sterilizing activity against M. tuberculosis.

A randomized comparison of two clarithromycin doses for treatment of Mycobacterium avium complex infections.

Two dosages of clarithromycin were compared for treatment of disseminated Mycobacterium avium disease of AIDS patients: high-dose (HD): 1,000 mg or 750 mg b.i.d. according to body weight, and low-dose (LD): 1,000 mg or 750 mg q.d. Patients with high probability of M. avium positive blood culture on day 0 received a 42-day clarithromycin treatment with HD (n = 27) or LD (n = 28) at random after stratification according to body weight. Assessment procedures, including quantitative blood cultures, were performed at days 14, 28 and 42. Forty-five patients were eligible for clinical and 28 for bacteriological evaluation. Bacteriological success was observed in 12 HD and 11 LD patients, partial success in one HD and two LD and failure in none of the HD and two LD (p = 0.33). Between days 0 and 42, log decreases in CFU counts/ml were (mean +/- SD) 3.13 +/- 0.82 (HD) and 2.67 +/- 1.8 (LD) (p = 0.38). Fever and night sweats significantly improved similarly in both groups; no change in spleen and liver size was observed on CT scans. Eight patients died during the study but no death was reported as drug related. Sixteen patients (HD = 6, LD = 10) discontinued the treatment because of side effects. A trend towards improved bacteriological effectiveness and reduced tolerance was observed in the HD group but the difference was not significant. With a power of 0.70, no dose effect was demonstrated between the two tested dosages. A daily dose of 1,000 mg clarithromycin was tested in drug combinations to treat disseminated M. avium infection in AIDS patients.

How effective is KRM-1648 in treatment of disseminated Mycobacterium avium complex infections in beige mice?

Although the MICs of 3'-hydroxy-5'-(4-isobutyl-1-piperazinyl)benzoxazinorifamycin, or KRM-1648 (KRM), for Mycobacterium avium complex (MAC) were significantly lower than those of other drugs, its in vivo activity was very weak. Beginning 28 days after inoculation, beige mice that had been infected intravenously with 1.87 x 10(7) CFU of MAC 101 were administered KRM alone, clarithromycin (CLARI) alone, or CLARI plus KRM six times weekly for 16 weeks. In contrast to the mice treated with CLARI-containing regimens, the mortality and the mean spleen weights of mice treated with KRM alone (either 10 or 20 mg/kg of body weight per dose) did not differ significantly from those of untreated mice, their numbers of CFU were very much greater than pretreatment values, and multiplication of MAC was only slightly inhibited. Although monotherapy by KRM selected KRM-resistant mutants, the selection was very weak; the mean number of CFU and the frequency of KRM-resistant mutants increased by no more than 1 order of magnitude after 16 weeks of treatment with KRM at 20 mg/kg per dose. Selection of CLARI-resistant mutants was inhibited but not completely prevented by treatment of the mice with CLARI plus KRM. These results indicate that KRM displayed only a weak bacteriostatic effect against the isolate tested in the beige mouse model; its ability to enhance the antimicrobial effect of CLARI or to prevent emergence of CLARI-resistant mutants was very limited.

Acquired resistance in Mycobacterium avium complex strains isolated from AIDS patients and beige mice during treatment with clarithromycin.

Clarithromycin has been reported to select clarithromycin resistant mutants of Mycobacterium avium complex (MAC) during treatment with clarithromycin in AIDS patients and beige mice. We selected resistant mutants in vitro at a frequency of 5 x 10(-9). Clarithromycin resistant strains of MAC isolated in AIDS patients and beige mice as well as derivatives selected in vitro had a unique pattern of acquired cross-resistance to macrolides and related antibiotics. In contrast, the pattern of resistance to non-macrolide antibiotics remained unchanged in clarithromycin resistant strains. A dramatic decrease in ribosome affinity for clarithromycin and erythromycin was found in clarithromycin resistant strains, but no mutation was found in the peptidyl domain of the 23S rRNA, indicating that another ribosomal modification is involved.

In vitro and in vivo activities of levofloxacin against Mycobacterium tuberculosis.

In tests with 18 drug-susceptible strains of Mycobacterium tuberculosis, the MIC at which 50% of the strains are inhibited by levofloxacin (LVFX) was one dilution less than that at which 50% of the strains are inhibited by ofloxacin (OFLO), but the MICs at which 90% of the strains are inhibited were similar. The in vivo activity of LVFX against M. tuberculosis was compared with the activities of isoniazid, OFLO, and sparfloxacin (SPFX). Mice were inoculated intravenously with 1.74 x 10(6) CFU of H37Rv, and treatments began the next day and were carried out six times weekly for 4 weeks. The severity of infection and effectiveness of treatment were assessed by survival rate, spleen weights, gross lung lesions, and enumeration of CFU in the spleen. In terms of CFU counts, the ranking of the anti-M. tuberculosis activities of the treatments used ran in the following order: LVFX (300 mg/kg of body weight) = SPFX (100 mg/kg) > isoniazid > SPFX (50 mg/kg) > OFLO (300 mg/kg) = LVFX (150 mg/kg) > OFLO (150 mg/kg) = LVFX (50 mg/kg). It seems, therefore, that the in vivo activity of LVFX is comparable to that produced by a twofold-greater dosage of OFLO. It is assumed that the maximal clinically tolerated dosage of LVFX is similar to that of OFLO, i.e., 800 mg daily, which is equivalent to 300 mg of LVFX per kg in mice. Because LVFX displayed powerful bactericidal activity, promising effects against human tuberculosis may be achieved if patients are treated with the maximal clinically tolerated dosage of LVFX.

Selection of clarithromycin-resistant Mycobacterium avium complex during combined therapy using the beige mouse model.

Sixteen weeks of treatment with clarithromycin (CLARI) alone displayed significant bactericidal activity against Mycobacterium avium complex infection in beige mice. Only two combined regimens, CLARI combined with an initial 4 or 8 weeks of amikacin (AMIKA), displayed activity greater than that displayed by CLARI alone. Four other combined regimens, CLARI combined with ethambutol (EMB), rifabutin (RBT), or both EMB and RBT during the entire 16 weeks of treatment or with AMIKA administered in an initial 2-week course showed bactericidal activity not significantly greater than that of CLARI alone. After 16 weeks of treatment, CLARI-resistant mutants were isolated from the majority of mice that had been treated with CLARI alone, CLARI-RBT, CLARI-EMB, or CLARI-EMB-RBT, as was the case for untreated controls, but the frequencies of occurrence of mutants were significantly greater in the groups treated with these combinations or CLARI alone. On the other hand, no CLARI-resistant mutants were isolated from the mice that had been treated with the combination of CLARI plus an initial 4 or 8 weeks of AMIKA and were isolated from only a tiny proportion of mice that had been treated with CLARI plus an initial 2 weeks of AMIKA. Therefore, only treatment with CLARI combined with an initial 4 or 8 weeks of AMIKA but not combined with RBT or EMB or both, could enhance the activity of the drug treatment and prevent the selection of CLARI-resistant mutants.

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

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.

Selection of a gyrA mutant of Mycobacterium tuberculosis resistant to fluoroquinolones during treatment with ofloxacin.

A strain of Mycobacterium tuberculosis resistant to ofloxacin was selected in a patient with a long history of multidrug-resistant tuberculosis eventually treated by ofloxacin combined with other second-line drugs. A mutation in the gyrA gene was hypothesized to be the mechanism of acquired resistance to ofloxacin in this strain. Chromosomal DNA of strains MTB1, isolated before treatment and susceptible to ofloxacin (MIC, 1 microgram/mL), and MTB2, isolated during treatment and resistant to ofloxacin (MIC, 32 micrograms/mL), was amplified by polymerase chain reaction (PCR) using two oligonucleotide primers highly homologous to DNA sequences flanking the quinolone resistance-determining region in gyrA of mycobacteria. Comparison of the nucleotide sequences of the 150-bp fragments obtained by PCR revealed a point mutation in MTB2 leading to the substitution of histidine for aspartic acid at a position corresponding to residues involved in quinolone resistance in Escherichia coli (Asp87), Staphylococcus aureus (Glu88), and Campylobacter jejuni (Asp90).

Sparfloxacin, ethambutol, and cortisol receptor inhibitor RU-40 555 treatment for disseminated Mycobacterium avium complex infection of normal C57BL/6 mice.

Sparfloxacin (50 mg/kg of body weight given subcutaneously each day), alone or in combination with ethambutol (50 mg/kg given subcutaneously each day), was examined for its therapeutic efficacy against experimental infection induced with the Mycobacterium avium complex in normal C57BL/6 mice. In addition, the potential anti-infective role of RU-40 555 (100 mg/kg given intraperitoneally each day), a drug that inhibits the cortisol receptors, was examined in the same model. Treatments were started 24 h after intravenous bacterial challenge and were continued for 21 days. Compared with controls, sparfloxacin or ethambutol decreased the CFU counts in spleens and lungs (P < 0.001). The sparfloxacin plus ethambutol combination was more effective than sparfloxacin alone in spleens (P < 0.001) but not in lungs. The sparfloxacin plus ethambutol plus RU-40 555 combination was more effective than the sparfloxacin plus ethambutol combination in spleens and lungs (P < 0.001). Thus, in this model, RU-40 555 enhanced the antibacterial activities of the antibiotics tested. Results of the study showed that normal C57BL/6 mice infected with the M. avium complex can be used for the evaluation of antimicrobial agents.

[Potential value of the amoxicillin-clavulanic acid combination in general medicine, gynecology-obstetrics and pediatrics departments]. / Intérêt potentiel de l'association amoxicilline + acide clavulanique dans les services de medecine, gynécologie-obstétrique et pédiatrie.

This study compares the probability of in vitro activity of amoxicillin-clavulanic acid combination (AMOX-CLA) with those of amoxicillin (AMOX), cephalothin (CEPH), cotrimoxazole (COT) and nalidixic acid (NAL) on the 2 003 strains isolated during the first semester of 1983 in 5 wards of medicine (MED), 2 of gynecology-obstetrics (GYN) and 1 of pediatrics (PED) at the Pitié-Salpêtrière Hospital. As expected, AMOX-CLA was active on most of the strains of S. aureus, E. coli, P. mirabilis, Klebsiella and Bacteroides resistant to AMOX. AMOX-CLA was active on 70 to 86% of all strains, a higher rate than that of AMOX in all situations taken in concert. AMOX-CLA was more often active than AMOX on urinary strains by 17% in MED and GYN, 26% in neonates and 37% in children; it was more often active by 16% on strains isolated from the genital tract and from specimens taken at birth, and by 43% on strains isolated from pus. AMOX-CLA showed the same activity rate as CEPH whatever the infection and was as often active as COT and NAL on urinary strains in MED. On the opposite, activity rates of AMOX-CLA were lower by 6 to 15% than those of COT and NAL on urinary strains in GYN and PED of COT on strains isolated from pus in MED, GYN and PED. Therefore, AMOX-CLA was superior to AMOX in every case, and comparable to CEPH and often COT and NAL, whose use is restricted in pregnant women and neonates owing to side effects.