M icrobiology
Chemotherapy 1992;38:297-302
National Reference Centre for Human Mycotic Diseases, Provincial Laboratory of Public Health, University of Alberta, Edmonton, Canada; Mycotic Diseases Branch, Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control, Public Health Service, Atlanta, Ga., USA
In vitro Activity of Amphotericin B, Hamycin and Their Novel Water-Soluble Compounds against Pathogenic Yeasts
Key Words
Abstract
In vitro activity Amphotericin B Hamycin JAI-amphotericin B JAI-hamycin Pathogenic yeasts
Twenty-eight pathogenic isolates, 4 each of Candida albicans, C. lusitaniae, C. parapsilosis, Cryptococcus neoformans, Torulopsis glabrata and Trichosporon beigelii were tested for their in vitro sensitivity to amphotericin B (AmB), hamycin (HA) and their novel water-soluble compounds, namely JAI-AmB (oral and injectable; patents pending) and JAI-HA (Jaimycin Inc., Walnut Creek, Calif., USA), using a standard double-dilution broth (1 ml/tubc) procedure. The 2 novel compounds, namely JAI-AmB and JAI-HA. contain one twenty-fifth (w/w) of the AmB and HA, respectively. Results showed that the minimal inhibitory concentrations (MICs) of AmB for all species, ex cept C. lusitaniae and Tr. beigelii (3.125-6.25 pg/ml), were 0.195-1.56 pg/ml. The values of JAI-AmB (oral) for C. albicans, C. parapsilosis, Cr. neoformans and To. glabrata ranged from 0.78 to 25 pg/ml. The MICs of JAI-AmB (oral) for the other yeasts were 100 pg/ml. All of the yeasts yielded higher MICs (3.125-100 pg/ml) against JAI-AmB (injectable) than the JAIAmB (oral) preparation. Except for C. parapsilosis (MICs 25100 pg/ml), all of the other species showed greater sensitivity to the parent HA (0.195-100 pg/ml) than AmB. The values for JAI-HA ranged from 0.195 to 100 pg/ml for all isolates, except C. tropicalis (1 (X) pg/ml). Based on our in vitro findings, in vivo efficacies of JAI-AmB and JAI-HA should be carried out.
I)r. A.S. Sekhon National Centre for Human Mycotic Diseases Provincial laboratory of Public Health University of Alberta Edmonton. Alta., T6G 2J2 (Canada)
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A.S. Sekhona A.A. Padhyeh A.K Garga Z. Hamir'
Amphotericin B (AmB) is a polyene macrolide, highly lipophilie and water insoluble. This antifungal antibiotic displays a broad spectrum of activity against most fungal path ogens. AmB remains the drug of choice for most systemic and life-threatening fungal in fections, despite a variety of side effects in cluding fever, chills, nausea, vomiting, azote mia, anemia, neurotoxicity and renal compli cations [1, 2], Due to its undesirable side effects, the use of AmB is limited in chemo therapy. In addition, the emergence of resis tance of Candida guilliermondii, C. lusitaniae and Trichosporon beigelii to AmB has been documented [3-9). Furthermore, AmB is not always effective therapeutically for opportu nistic mycoses caused by yeasts and filamen tous fungi in compromised hosts [10]. Re cently, novel water-soluble compounds of AmB and hamycin (HA), another antifungal antibiotic of the polyene family, have been de veloped by Jaimycin Inc., Walnut Creek, Calif., USA. Jaimycin Inc. produces such com pounds, identified as JAI-AmB and JAI-HA, via the ‘JAI-umbrella’ process. It utilizes the reactive terminals of each antibiotic or syn thetic pharmaceutical agent under clinical use to form new compounds. Both JAI-AmB and JAI-HA, which are unrelated to carrier sys tems such as liposomes or cyclodextrins, are neither encapsulated nor coated, and are not the subject of slow release. Rather, they are designed for better absorption, less degrada tion at the administration site and better deliv ery to the target site, with reduced toxicity as compared to their parent compounds. Fur thermore, JAI-AmB and JAI-HA contain only one twenty-fifth of the parent drug by weight [11], according to Jaimycin Inc.
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The present study was undertaken to inves tigate the in vitro activity of the newly devel oped, water-soluble compounds against some pathogenic yeasts and to compare their re sponse to that of their parent compounds.
Materials and Methods Fungi Seven species of yeasts isolated front clinical speci mens, C. albicans (PLM 1612. 1698, 1699, 1761). C. lu sitaniae (Pl.M 1645, 1646, 1647, 1648), C. parapsilosis (PLM 1237, 1238, 1249, 1250), C. tropicalis (PL.M 1928, 1933,1935,1976), Cryptococcus neofonnans (PLM 1255, 1269,1285, 1286), Torulopsisglabrata (PLM 1279, 1702, 1704,1712) and Tr. beigelii (PML 1621, 1622, 1623, 1624), were employed to study their susceptibility to AntB, HA and their respective water-soluble compounds. Also included in this study was a reference Paecilomyces variotii isolate (PLM 909 = 27.1, received from the late Dr. S. Shadomy, Medical College of Virginia, Richmond, Va., USA) to monitor the quality and re producibility of our in vitro susceptibility studies. Maintenance o f Stock Cultures Stock cultures of the yeasts were grown on phytone-yeast extract (PYE) agar slants at 37 °C for 4872 h and then stored at 0-3 °C until used. Preparation o f Inoculum Suspensions Each yeast isolate was given three passages on PYE slants, free from any antifungal or antibacterial anti biotics, and grown for 24-48 h at 37 °C. A small portion of growth (48 h) was suspended, using a sterile wireloop, in 10 ml of sterile, deionized distilled water. Stan dardized suspensions were prepared by obtaining a spectrophotometric reading of 95% T at 530 X. The procedural details have been outlined elsewhere [12]. Assay Medium and in vitro Susceptibility Test Procedure The culture medium employed was a standard M-3 antibiotic broth (Difco Laboratories; 1 ml/tube), as rec ommended by McGinnis [13]. The concentrations of each antibiotic ranged from 0.195 to 100 pg/ml. Each tube containing an antibiotic dilution was inoculated with 0.1 ml of the standardized inoculum suspension. After inoculation, these tubes were shaken gently to mix the inoculum and then incubated at 30 °C for 48 h. The minimal inhibitory concentrations (MICs) and
Sekhon/Padhye/Garg/Hamir
In vitro Activity of Polyenes against Yeasts
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Introduction
Table 1. Results of the in vitro activity of polyene antibiotics (pg/ml) against 28 pathogenic yeast isolates
Yeast
AmB MIC
MFC
JAI-AmB1 (oral) MIC
C. albicans (4)
C. lusitaniae (4)
C. parapsilosis (4)
MIC
>100 (4)
0.78 (1) 1.56 (1) 3.12 (1) 6.25 (1)
6.25 (2) 12.5 (2)
12.5 (2) >>100 (2)
25 (1) 50
3.12 (1) 6.25 (3)
6.25 (4)
> 100 (4)
> 1(X) (4)
25 (2) >>100 (2)
> KM) (4)
0.39 (4)
0.78 (1) 1.56
6.25 (1) 12.5 (1) 25 (1) 50 (1)
50 (2) 1(H) (2)
> UK) (4)
> 100
12.5 (1) 25 (2) 100
> KM)
0.78 (3)
1.56 (1)
3.12 (2) 6.25 (2)
3.125 (3)
6.25 (1)
> 100 (4)
(4)
JAI-HA1
HA MIC
MFC
MIC
MFC
100 (2)
KM) (4)
12.5 (1) 50 (2) KM) (1)
50 (1) ¿1 0 0
12.5
50 (1) 1(X)
(3)
25 (1)
1.56 (4)
> KM) (4)
(3)
(3)
> 100 (4)
(1)
(4)
Tr. beigelii (4)
1(K)
(3)
(4)
3.125 (1) 6.25 (1) > 100 (2)
3.125 (2) 12.5 (2)
> 100 (4)
50 (2) 100 (2)
12.5 (2) KM) (2)
< KM) (4)