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Ito A, Nanjo Y, Kajiwara C, Shiozawa A, Urabe N, Homma S, Kishi K, Yamada K, Ishii Y, Tateda K. Intrinsic clarithromycin heteroresistance in Mycobacterium avium. J Infect Chemother 2024; 30:752-756. [PMID: 38369123 DOI: 10.1016/j.jiac.2024.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 02/05/2024] [Accepted: 02/14/2024] [Indexed: 02/20/2024]
Abstract
BACKGROUND Mycobacterium avium is associated with pulmonary disease in otherwise healthy adults. Several clarithromycin-refractory cases have been reported, including some cases caused by clarithromycin-susceptible strains. OBJECTIVES To characterize the reason for the discrepancy between clinical response and antibiotic susceptibility results. METHODS We conducted population analysis of clarithromycin-tolerant and heteroresistant subpopulations of M. avium cultured in vitro and in homogenates of infected lungs of mice. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined for 28 M. avium and two M. kansasii strains. Mice were intranasally infected with M. avium and treated with or without clarithromycin (100 mg/kg) thrice weekly. They were sacrificed on day 35 and the bacteria in lung homogenates were tested for clarithromycin resistance. Population analysis assays were performed based on colony growth on plates containing two-fold dilutions of clarithromycin. RESULTS The MBC/MIC ratios were ≥8 in all 28 strains of M. avium tested. In the population analysis assay, several colonies were observed on the plates containing clarithromycin concentrations above the MIC (2-64 mg/L). No growth of M. kansasii colonies was observed on the plates containing clarithromycin concentrations ≥2 mg/L. M. avium in the homogenates of infected lungs showed clearer clarithromycin-resistant subpopulations than in vitro, regardless of clarithromycin exposure. CONCLUSION M. avium shows intrinsic heterogeneous resistance (heteroresistance) to clarithromycin. This may explain the observed discrepancies between clarithromycin susceptibility testing results and clinical response to clarithromycin treatment. Further studies are needed to confirm a link between heteroresistance and clinical outcomes.
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Affiliation(s)
- Ai Ito
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan; Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yuta Nanjo
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan; Department of Respiratory Medicine, Juntendo University School of Medicine, 3-1-3 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Chiaki Kajiwara
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Ayako Shiozawa
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Naohisa Urabe
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan
| | - Sakae Homma
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan
| | - Kazuma Kishi
- Department of Respiratory Medicine, Toho University Omori Medical Center, 6-11-1 Omori-nishi, Ota-ku, Tokyo, 143-8541, Japan
| | - Kageto Yamada
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yoshikazu Ishii
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Kazuhiro Tateda
- Department of Microbiology and Infectious Disease, Toho University School of Medicine, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
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Berlin S, Randow T, Scheuch E, Grube M, Venner M, Siegmund W. Pharmacokinetics and pulmonary distribution of gamithromycin after intravenous administration in foals. J Vet Pharmacol Ther 2017; 40:406-410. [DOI: 10.1111/jvp.12402] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 02/14/2017] [Indexed: 01/29/2023]
Affiliation(s)
- S. Berlin
- Department of Clinical Pharmacology; Center of Drug Absorption and Transport (C_DAT); University Medicine of Greifswald; Greifswald Germany
| | | | - E. Scheuch
- Department of Clinical Pharmacology; Center of Drug Absorption and Transport (C_DAT); University Medicine of Greifswald; Greifswald Germany
| | - M. Grube
- Department of General Pharmacology; Center of Drug Absorption and Transport (C_DAT); University Medicine of Greifswald; Greifswald Germany
| | - M. Venner
- Veterinary Clinic for Horses; Destedt Germany
| | - W. Siegmund
- Department of Clinical Pharmacology; Center of Drug Absorption and Transport (C_DAT); University Medicine of Greifswald; Greifswald Germany
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van der Paardt AF, Wilffert B, Akkerman OW, de Lange WC, van Soolingen D, Sinha B, van der Werf TS, Kosterink JG, Alffenaar JWC. Evaluation of macrolides for possible use against multidrug-resistant Mycobacterium tuberculosis. Eur Respir J 2015; 46:444-55. [DOI: 10.1183/09031936.00147014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 03/20/2015] [Indexed: 01/16/2023]
Abstract
Multidrug-resistant tuberculosis (MDR-TB) is a major global health problem. The loss of susceptibility to an increasing number of drugs behoves us to consider the evaluation of non-traditional anti-tuberculosis drugs.Clarithromycin, a macrolide antibiotic, is defined as a group 5 anti-tuberculosis drug by the World Health Organization; however, its role or efficacy in the treatment of MDR-TB is unclear. A systematic review of the literature was conducted to summarise the evidence for the activity of macrolides against MDR-TB, by evaluating in vitro, in vivo and clinical studies. PubMed and Embase were searched for English language articles up to May 2014.Even though high minimum inhibitory concentration values are usually found, suggesting low activity against Mycobacterium tuberculosis, the potential benefits of macrolides are their accumulation in the relevant compartments and cells in the lungs, their immunomodulatory effects and their synergistic activity with other anti-TB drugs.A future perspective may be use of more potent macrolide analogues to enhance the activity of the treatment regimen.
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Gupta R, Mehra NK, Jain NK. Fucosylated multiwalled carbon nanotubes for Kupffer cells targeting for the treatment of cytokine-induced liver damage. Pharm Res 2013; 31:322-34. [PMID: 24043294 DOI: 10.1007/s11095-013-1162-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 07/28/2013] [Indexed: 11/24/2022]
Abstract
PURPOSE To develop, characterize and exploring the sulfasalazine loaded fucoyslated multi walled carbon nanotubes for Kupffer cell targeting for effective management of cytokine-induce liver damage. METHODS Sulfasalazine was loaded into the fucosylated MWCNTs after subsequential functionalization (carboxylation, acylation and amidation) using dialysis membrane technique. The in vitro, in vivo studies were performed on macrophages J 774 cell line for Kupffer cells targeting for the treatment of cytokine-induced liver damage. RESULTS The loading of SSZ into SSZ-FUCO-MWCNTs was 87.77 ± 0.11% (n = 3). Sustained release was obtained from SSZ-FUCO-MWCNTs, with 89.12 ± 0.71% of SSZ released into medium at 48th hr. SSZ-FUCO-MWCNTs showed the 9.0 ± 0.23% hemolysis was drastically reduced from 21.62 ± 0.24% SSZMWCNTs 21.62 ± 0.24%. In SRB assay, SSZ-FUCO-MWCNTs showed more cytotoxicity than raw and SSZ-MWCNTs. In cytokine assay, SSZ- FUCO-MWCNTs exhibited significantly higher inhibition of IL-12 p40 secretion. In Western blot assay, SSZ-FUCO-MWCNTs significantly inhibit NF-κB activation. CONCLUSION The results suggested that the SSZ-FUCO-MWCNTs may be useful nano-carriers for targeted delivery to Kupffer cells in the treatment of cytokine-induced liver damage.
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Affiliation(s)
- Richa Gupta
- Pharmaceutics Research Laboratory Department of Pharmaceutical Sciences, Dr. H. S. Gour University, Sagar, MP, 470 003, India
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Hasegawa N, Nishimura T, Watabnabe M, Tasaka S, Nakano Y, Yamazaki K, Hashimoto S, Nishimura M, Ishizaka A. Concentrations of clarithromycin and active metabolite in the epithelial lining fluid of patients with Mycobacterium avium complex pulmonary disease. Pulm Pharmacol Ther 2009; 22:190-3. [DOI: 10.1016/j.pupt.2008.11.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 11/09/2008] [Accepted: 11/15/2008] [Indexed: 01/15/2023]
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6
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Mascarenhas P, Gapski R, Al-Shammari K, Hill R, Soehren S, Fenno JC, Giannobile WV, Wang HL. Clinical Response of Azithromycin as an Adjunct to Non-Surgical Periodontal Therapy in Smokers. J Periodontol 2005; 76:426-36. [PMID: 15857078 DOI: 10.1902/jop.2005.76.3.426] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
BACKGROUND Antibiotic therapy can be used in very specific periodontal treatment situations such as in refractory cases of periodontal disease found to be more prevalent in smokers. This study was designed to determine the efficacy of azithromycin (AZM) when combined with scaling and root planing (SRP) for the treatment of moderate to severe chronic periodontitis in smokers. METHODS Thirty-one subjects were enrolled into a 6-month randomized, single-masked trial to evaluate clinical, microbial (using benzoyl- DL-arginine naphthylamine [BANA] assay), and gingival crevicular fluid (GCF) pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) levels in response to SRP alone or SRP + AZM. At baseline, patients who smoked > or =1 pack per day of cigarettes who presented with at least five sites with probing depths (PD) of > or =5 mm with bleeding on probing (BOP) were randomized into the test or control groups. At baseline and 3 and 6 months, clinical measurements (probing depth [PD], clinical attachment loss [CAL], and bleeding on probing [BOP]) were performed. GCF bone marker assessment (Ctelopeptide [ICTP] as well as BANA test analyses) were performed at baseline, 14 days, and 3 and 6 months. RESULTS The results demonstrated that both groups displayed clinical improvements in PD and CAL that were sustained for 6 months. Using a subject-based analysis, patients treated with SRP + AZM showed enhanced reductions in PD and gains in CAL at moderate (4 to 6 mm) and deep sites (>6 mm) (P <0.05). Furthermore, SRP + AZM resulted in greater reductions in BANA levels compared to SRP alone (P <0.05) while rebounds in BANA levels were noted in control group at the 6-month evaluation. No statistically significant differences between groups on mean BOP and ICTP levels during the course of the study were noted. CONCLUSIONS The utilization of AZM in combination with SRP improves the efficacy of non-surgical periodontal therapy in reducing probing depth and improving attachment levels in smokers with moderate to advanced attachment loss.
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Affiliation(s)
- Paulo Mascarenhas
- Department of Periodontics/Prevention/Geriatrics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109-1078, USA
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Seral C, Michot JM, Chanteux H, Mingeot-Leclercq MP, Tulkens PM, Van Bambeke F. Influence of P-glycoprotein inhibitors on accumulation of macrolides in J774 murine macrophages. Antimicrob Agents Chemother 2003; 47:1047-51. [PMID: 12604540 PMCID: PMC149288 DOI: 10.1128/aac.47.3.1047-1051.2003] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The influence of inhibitors of P-glycoprotein (verapamil [VE], cyclosporine [CY], and GF120918 [GF]) on the cell handling of macrolides (erythromycin [ERY], clarithromycin [CLR], roxithromycin [ROX], azithromycin [AZM], and telithromycin [TEL]) was examined in J774 murine macrophages. The net influx rates of AZM and TEL were increased from 2- to 3.5-fold in the presence of these inhibitors, but their efflux was slowed only marginally. At 3 h, the inhibitors increased the levels of AZM, ERY, and TEL accumulation approximately three- to fourfold (the effect of VE, however, was lower) but did not influence CLR accumulation (the inhibitors had an intermediate behavior on ROX accumulation). The effect was concentration dependent (half-maximal increases in the level of accumulation of AZM were obtained with GF, CY, and VE at 0.5, 5, and 10 micro M, respectively). ATP depletion also caused an approximately threefold increase in the level of accumulation of AZM. Two inhibitors of MRP (probenecid [2.5 mM] and gemfibrozil [0.25 mM]) had no effect. Monensin (a proton ionophore) completely suppressed the accumulation of AZM in control cells as well as in cells incubated in the presence of VE, demonstrating that transmembrane proton gradients are the driving force causing the accumulation of AZM in both cases. Yet, VE did not alter the pH of the lysosomes (approximately 5) or of the cytosol (approximately 7.1). P-glycoprotein was detected by immunostaining at the cell surface as well as in intracellular vacuoles (endosomes and lysosomes). The data suggest that the influx of AZM, ERY, TEL, and ROX is adversely influenced by the activity of P-glycoprotein in J774 macrophages, resulting in suboptimal drug accumulation.
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Affiliation(s)
- Cristina Seral
- Unité de Pharmacologie Cellulaire et Moléculaire, Université Catholique de Louvain, Brussels, Belgium
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Schiavano GF, Celeste AG, Salvaggio L, Sisti M, Brandi G. Efficacy of macrolides used in combination with ethambutol, with or without other drugs, against Mycobacterium avium within human macrophages. Int J Antimicrob Agents 2001; 18:525-30. [PMID: 11738339 DOI: 10.1016/s0924-8579(01)00461-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The activities of clarithromycin or roxithromicin used in combination with other antimicrobial drugs were tested in human macrophages experimentally infected with 23 strains of Mycobacterium avium. Overall, clarithromycin-ethambutol-rifampicin was the most active combination tested. The reduction in intracellular viable bacilli was found to be more than 1 log(10) for 95% and more than 2 logs(10) for 65% of the strains. The second most active combination was roxithromycin-ethambutol-rifampicin, which was found to be bactericidal for about 80% and highly bactericidal for 20% of the strains. Others combinations were only bacteriostatic or weakly bactericidal for many of the strains. The addition of a third drug did not necessarily promote enhanced bacterial killing inside the macrophage.
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Affiliation(s)
- G F Schiavano
- Institute of Hygiene, University of Urbino, 61029, Urbino, Italy
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Carlson LD, Wallis CK, Coyle MB. Standardized BACTEC method to measure clarithromycin susceptibility of Mycobacterium genavense. J Clin Microbiol 1998; 36:748-51. [PMID: 9508306 PMCID: PMC104619 DOI: 10.1128/jcm.36.3.748-751.1998] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
A standardized clarithromycin susceptibility test for Mycobacterium genavense is reported. The BACTEC radiometric broth dilution test method recommended for Mycobacterium avium complex was modified to develop a reliable and reproducible procedure. Test development involved optimization of medium pH and inoculum densities for antibiotic vials as well as growth control vials. MIC control organisms included Mycobacterium simiae, Mycobacterium avium, and Mycobacterium xenopi. Growth control vials required two to three inoculum dilutions, which varied for each species. Clarithromycin MICs and MBCs for 12 isolates and 1 colonial variant of M. genavense ranged from < or = 0.06 to 0.25 microg/ml.
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Affiliation(s)
- L D Carlson
- Department of Laboratory Medicine, Harborview Medical Center, University of Washington, Seattle 98104, USA
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Fréhel C, Offredo C, de Chastellier C. The phagosomal environment protects virulent Mycobacterium avium from killing and destruction by clarithromycin. Infect Immun 1997; 65:2792-802. [PMID: 9199452 PMCID: PMC175394 DOI: 10.1128/iai.65.7.2792-2802.1997] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Murine bone marrow-derived macrophages (Mphis) infected with virulent strains of Mycobacterium avium (TMC 724 and a human clinical isolate) or with an avirulent opaque variant that spontaneously dissociates from the virulent human clinical isolate were subjected to a prolonged and continuous treatment with clarithromycin added at the MIC. The efficiency of this antibiotic in terms of inhibition of bacterial growth and bacterial degradation was evaluated during a 21-day treatment period. Growth was assessed by determination of CFU of intracellular bacteria and by a quantitative ultrastructural analysis which allowed us also to determine the extent of bacterial degradation. A similar treatment was applied to the same strains growing in liquid medium. Our data show that in liquid medium, clarithromycin caused a 90% decrease in CFU within 7 days of treatment. When applied to Mphis infected with virulent M. avium, clarithromycin immediately arrested bacterial growth but was unable to fully kill and degrade intracellularly growing virulent bacteria. After 21 days of treatment, 25% of intracellular bacteria were still morphologically intact. These bacteria resumed growth upon removal of the antibiotic, with a normal replication rate. These bacteria had not become more resistant to the drug, since the MIC was unchanged as compared to the one determined for the initial stock used to infect Mphis. Our data therefore suggest that the intraphagosomal environment protects bacteria from degradation. We propose that the inability of the drug to completely destroy bacteria is the result of a limited accessibility of the drug due to prevention of fusions between the immature phagosomes in which virulent bacteria reside and lysosomes in which clarithromycin accumulates. In accord with our proposal, we show that the avirulent opaque variant, which does not prevent phagosome-lysosome fusions (unpublished data), is finally destroyed by clarithromycin even within the phagosomal environment.
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Affiliation(s)
- C Fréhel
- INSERM U411, Laboratoire de Microbiologie, UFR de Médecine Necker Enfants Malades, Paris, France
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Heifets LB. Clarithromycin against Mycobacterium avium complex infections. TUBERCLE AND LUNG DISEASE : THE OFFICIAL JOURNAL OF THE INTERNATIONAL UNION AGAINST TUBERCULOSIS AND LUNG DISEASE 1996; 77:19-26. [PMID: 8733409 DOI: 10.1016/s0962-8479(96)90070-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
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.
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Affiliation(s)
- L B Heifets
- Department of Microbiology, University of Colorado Health Sciences Center, USA
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Ghebremichael S, Svenson SB, Källenius G, Hoffner SE. Antimycobacterial synergism of clarithromycin and rifabutin. SCANDINAVIAN JOURNAL OF INFECTIOUS DISEASES 1996; 28:387-90. [PMID: 8893404 DOI: 10.3109/00365549609037925] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Clarithromycin and rifabutin are among the most promising drugs for the therapy of infections caused by Mycobacterium avium or other atypical mycobacteria. Since synergism of combined drugs is important in order to achieve strong antimycobacterial activity, the combined inhibitory effects of antibacterial agents should also be investigated when agents are evaluated for possible use in antimycobacterial drug therapy. In the present study we examined the antimycobacterial activity of clarithromycin, rifabutin, and their combination against 51 clinical isolates of the M. avium complex from patients with acquired immune deficiency syndrome (AIDS) with disseminated mycobacteriosis. A concentration-dependent inhibition was seen for each drug. The antibacterial effect was significantly more pronounced for the combined drugs than for the agents tested separately. Synergism, against up to 88% of the strains tested, was seen for the tested drugs combined at different concentrations. All 51 M. avium strains were susceptible to the combination of 4 mg/l clarithromycin and 2 mg/l rifabutin.
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Affiliation(s)
- S Ghebremichael
- Swedish Institute for Infectious Disease Control, Karolinska Institute, Stockholm, Sweden
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Mor N, Vanderkolk J, Mezo N, Heifets L. Effects of clarithromycin and rifabutin alone and in combination on intracellular and extracellular replication of Mycobacterium avium. Antimicrob Agents Chemother 1994; 38:2738-42. [PMID: 7695255 PMCID: PMC188278 DOI: 10.1128/aac.38.12.2738] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The combined effect of clarithromycin and rifabutin against Mycobacterium avium multiplying either within human monocyte-derived macrophages or extracellularly in a liquid medium was additive: both MICs and MBCs were twofold lower for the combination than they were for each drug alone. Prolonged exposure for 4 weeks of M. avium-infected macrophages to combined concentrations that were only twofold greater than the MICs resulted in a 100-fold decrease in the number of viable bacteria, while in the drug-free controls a 100-fold or greater increase in comparison with the initial viable counts took place. Comparison of this effect with the results of the prolonged exposure to each drug alone suggested that under these experimental conditions rifabutin enhanced the antimicrobial activity of clarithromycin against intracellular bacteria. At the same time, inhibition of intracellular growth by a 2-h pulsed exposure of the infected macrophages to the combination of the two drugs was not different from the effect induced by clarithromycin alone. In conclusion, clarithromycin played the major role in the antimicrobial activity of the tested combination, while rifabutin may have enhanced this effect during a prolonged exposure of the intracellular bacteria to these two agents.
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Affiliation(s)
- N Mor
- National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206
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