Antimicrobial activity of omiganan pentahydrochloride against contemporary fungal pathogens responsible for catheter-associated infections

(1)

ANTIMICROBIALAGENTS ANDCHEMOTHERAPY, Mar. 2008, p. 1187–1189 Vol. 52, No. 3

0066-4804/08/$08.00⫹0 doi:10.1128/AAC.01475-07

Antimicrobial Activity of Omiganan Pentahydrochloride against

Contemporary Fungal Pathogens Responsible for

Catheter-Associated Infections

䌤

Thomas R. Fritsche,

1

* Paul R. Rhomberg,

1

Helio S. Sader,

1,2

and Ronald N. Jones

1,3

JMI Laboratories, North Liberty, Iowa1_{; Universidade Federal de Sao Paulo, Sao Paulo, Brazil}2_{; and}

Tufts University School of Medicine, Boston, Massachusetts3

Received 14 November 2007/Returned for modification 18 December 2007/Accepted 28 December 2007

Omiganan, a bactericidal and fungicidal cationic peptide being developed as a topical gel for prevention of catheter-associated infections, inhibited commonly occurring fungal pathogens includingCandidaspp. (106 isolates) at<256␮g/ml and molds (including 10Aspergillusisolates) at<1,024␮g/ml. All fungi were inhibited

by omiganan at concentrations well below the 1% (10,000␮g/ml) clinical formulation, including species with

reduced susceptibility to azoles and echinocandins.

Indwelling venous access devices, especially central venous catheters, are a primary source of nosocomial bloodstream infections, accounting for an estimated 250,000 cases annually in the United States (15). While staphylococci and enterococci produce most bloodstream infections, data from the National Nosocomial Infections Surveillance system and other pub-lished sources has consistently shown that approximately 8 to 10% are produced by Candida spp. (1, 14, 15). Given the importance of fungi as pathogens in compromised hosts and difficulty in medical management of these infections, preven-tion of their occurrence can be expected to have a significant impact on overall patient morbidity and mortality and related health care expenditures (1, 4, 5, 16). The emergence of resis-tance among fungal pathogens, either appearing de novo or through selection of species with intrinsic resistance mecha-nisms (e.g., fluconazole resistance inCandida krusei), further confounds this problem and poses special challenges in patient management (3, 11).

Prevention of local catheter site infections by both bacterial

and fungal pathogens is an important component in controlling nosocomial bloodstream infections and improving patient out-comes (15, 19). Efforts to decrease infection rates have in-cluded education on proper catheter insertion techniques and care, use of sterile barrier precautions, and appropriate skin decontamination given many such infections follow from inva-sion of the transcutaneous catheter tract (15). The usual skin decontamination protocols have utilized povidone-iodine, iso-propyl alcohol, and/or chlorhexidine gluconate, including the use of a chlorhexidine-impregnated dressing (7). The recent description of human antimicrobial peptides such as defensins and cathelicidins as possible effector molecules in prevention of infection is another novel therapeutic approach based upon the antimicrobial properties of naturally occurring compounds found in leukocytes and epithelial secretions of vertebrates (8). One such agent is omiganan, a rapidly bactericidal and fungi-cidal cationic peptide analog of indolicidin that is known to significantly reduce normal skin flora counts following topical applications (18). This agent is being developed as a topical

* Corresponding author. Mailing address: JMI Laboratories, 345 Beaver Kreek Centre, Suite A, North Liberty, IA 52317. Phone: (319) 665-3370. Fax: (319) 655-3371. E-mail: [email protected].

䌤_{Published ahead of print on 7 January 2008.}

TABLE 1. Cumulative percent inhibited at omiganan MICs tested against six groups of yeasts and molds (126 isolates)

Organism group (no. of isolates tested)

Cumulative % organisms inhibited at MIC (␮g/ml) ofa_:

ⱕ0.5 1 2 4 8 16 32 64 128 256 512 1,024

Candidaspp. (106) 0 0 0 0 0 4 14 51 81 100 C. albicans(52) 0 0 0 0 0 0 2 65 100

C. glabrata(22) 0 0 0 0 0 0 0 0 18 100

C. krusei(10) 0 0 0 0 0 0 20 70 100

C. parapsilosis(11) 0 0 0 0 0 0 9 18 82 100 C. tropicalis(11) 0 0 0 0 0 36 100

Molds (20) 0 5 5 5 15 20 25 45 60 80 80 100

Aspergillusspp. (10) 0 0 0 0 0 10 20 30 50 60 60 100

Non-Aspergillus(10)b ₉ ₁₀ ₁₀ ₁₀ ₃₀ ₃₀ ₃₀ ₆₀ ₇₀ ₁₀₀

a_{Omiganan clinical formulation concentration}_⫽_10,000_␮g/ml.

b_Curvularia_{spp. (2 isolates),}_Fusarium_{spp. (2 isolates),}_{Paecilomyces variotii}_{(1 isolate),}_{Penicillium marneffei}_{(1 isolate), and}_Penicillium_{spp. (4 isolates).}

(2)

antimicrobial agent and is currently in a phase III U.S. and European clinical trial for prevention of catheter-associated infections and in preclinical development for other indications (8–10, 17, 18).

The purpose of this study was to update and expand the analysis of omiganan activity against prevalent fungal patho-gens, to better characterize the compound’s breadth of spec-trum and potency against species commonly encountered in catheter colonization and catheter-associated bloodstream in-fections, and also to establish the level of activity against prev-alent mold species. (This material was presented in part at the 47th Annual Meeting of the Interscience Conference on An-timicrobial Agents and Chemotherapy held in Chicago, IL, 11 to 20 September 2007.)

Test organisms originated from sterile site infections (126 isolates; bloodstream, respiratory tract, and deep tissues recov-ered during 2005 and 2006) and includedCandida albicans(52 isolates),Candida glabrata(22 isolates),Candida tropicalis(11 isolates),Candida parapsilosis(11 isolates),C. krusei(10 iso-lates),Aspergillusspp. (10 isolates), and other mold species (10 isolates).

Broth microdilution MIC testing was performed according to CLSI methods (documents M27-A2, M27-S2, and M38-A; 2002) (6, 12, 13). Omiganan standard powder was solubilized in sterile distilled water; other agents were handled as recom-mended by CLSI (12, 13). Panels were produced by JMI Lab-oratories (North Liberty, IA) using RPMI-1640 broth supple-mented with morpholinepropanesulfonic acid buffer; results were recorded at 48 h as specified, and interpretive criteria, where available, were those published in M27-S2 (12). Quality control (QC) was performed as recommended in M27-A2 and M38-A (12, 13) using the following QC strains:C. parapsilosis

ATCC 22019 andC. kruseiATCC 6258. Omiganan QC ranges utilized were those of Anderegg et al. (2), and all QC results for omiganan and comparator antifungal agents were within the specified control ranges.

Omiganan inhibited allCandidasp. isolates within a 4-log2 dilution range (16 to 256␮g/ml), being most active againstC. tropicalis,C. albicans, andC. krusei(concentration at which 50% or 90% of organisms are inhibited [MIC50/MIC90], 32 to 64/32 to 128␮g/ml) and least active againstC. glabrataandC. parapsilosis

(MIC50/MIC90, 128 to 256/256␮g/ml [Table 1]). Similar antifun-gal activity (MIC50, 64␮g/ml) was evident againstC. kruseiwith intrinsic resistance to fluconazole (MIC50, 32␮g/ml) compared with that ofC. albicans(MIC50, 1␮g/ml [Table 2]). While all mold isolates were inhibited byⱕ1,024 ␮g/ml of omiganan, MIC90s for non-Aspergillusspp. were generally fourfold lower than those forAspergillusspp. (Tables 1 and 2).

Among comparator antifungal agents, results were highly variable and species dependent, withC. kruseibeing the most resistant to all agents except voriconazole (Table 2). Only amphotericin B and omiganan (MIC90, 1 to 2 and 32 to 256

␮g/ml, respectively) displayed consistent activity against all yeast and mold species.

In the current clinical gel formulation of 1% gel (topical concentration, 10,000␮g/ml), omiganan was active against all commonly isolated yeast and mold pathogens (highest docu-mented MICs, 256 and 1,024␮g/ml, respectively) associated with catheter-related or sterile site infection, including those

species with intrinsically reduced susceptibilities to other anti-fungal agents (Table 2).

This cationic peptide (omiganan) represents a “first-in-class” topical agent that displays broad antifungal and antibac-terial coverage of all major pathogens responsible for local catheter site and catheter-associated bloodstream infections; none of the currently marketed topical antimicrobials (mupiro-TABLE 2. Activities of omiganan and comparator antifungal agents

tested against yeast and mold pathogens (126 isolates)

Organism (no. of isolates tested) or antimicrobial agent

MIC (␮g/ml) %

Organisms susceptible/ resistanta

50% 90% Range

Candida albicans(52)

Omiganan 64 128 32–128 —/—

Amphotericin B 1 1 0.5–1 —/—

Fluconazole 1 ⬎64 0.12–⬎64 67.3/30.8

5-Flucytosine 0.12 1 ⱕ0.03–2 100.0/0.0

Itraconazole 0.12 16 ⱕ0.008–16 50.0/48.1

Nystatin 8 8 8 —/—

Voriconazole 0.03 ⬎16 ⱕ0.008–16 75.0/25.0

Candida glabrata(22)

Omiganan 256 256 128–256 —/—

Fluconazole 4 ⬎64 1–⬎64 77.3/18.2

5-Flucytosine 0.06 0.06 ⱕ0.03–0.06 100.0/0.0

Itraconazole 0.12 0.5 0.03–1 72.7/4.6

Voriconazole 0.06 2 0.03–2 86.4/0.0

Candida krusei(10)

Omiganan 64 128 32–128 —/—

Fluconazole 32 64 32–64 0.0/100.0

5-Flucytosine 16 32 8–32 0.0/30.0

Itraconazole 0.5 0.5 0.12–0.5 10.0/0.0

Voriconazole 0.25 0.5 0.12–0.5 100.0/0.0

Candida parapsilosis(11)

Omiganan 128 256 32–256 —/—

Amphotericin B 1 1 1 —/—

Fluconazole 0.5 16 0.5–16 81.8/0.0

5-Flucytosine 0.12 0.12 0.06–0.12 100.0/0.0

Itraconazole 0.06 0.25 0.015–0.25 63.6/0.0

Voriconazole 0.015 0.12 ⱕ0.008–0.12 100.0/0.0

Candida tropicalis(11)

Omiganan 32 32 16–32 —/—

Fluconazole 0.25 ⬎64 0.12–⬎64 81.8/18.2

5-Flucytosine 0.06 0.12 0.06–0.12 100.0/0.0

Itraconazole 0.03 0.12 0.015–0.12 100.0/0.0

Voriconazole 0.015 16 0.015–16 72.7/27.3

Aspergillusspp. (10)

Omiganan 128 1024 16–1024 —/—

Amphotericin B 0.5 1 0.12–1 —/—

Fluconazole ⬎64 ⬎64 32–⬎64 —/—

5-Flucytosine ⬎64 ⬎64 1–⬎64 —/—

Itraconazole 0.03 0.06 ⱕ0.008–0.12 —/—

Nystatin 16 16 2–32 —/—

Voriconazole 0.25 0.25 0.06–0.25 —/—

Non-Aspergillussp. molds (10)

Omiganan 64 256 1–256 —/—

Amphotericin B 0.25 0.5 0.015–1 —/—

Fluconazole ⬎64 ⬎64 1–⬎64 —/—

5-Flucytosine ⬎64 ⬎64 0.25–⬎64 —/—

Itraconazole 0.06 ⬎16 ⱕ0.008–⬎16 —/—

Nystatin 8 16 0.5–16 —/—

Voriconazole 0.25 2 ⱕ0.008–⬎16 —/—

a_{Criteria as published by the CLSI (2005); —, no breakpoint available.}

(3)

cin, triple antibiotic ointment, or retapamulin) demonstrates a spectrum that has comparable breadth. Given the availability of standardized antifungal susceptibility test methods (12, 13), ongoing surveillance of fungal pathogens implicated in cathe-ter-associated infections will be an important management tool to anticipate changes in species composition, infection rates, and trends of resistance to the applied topical agents, including omiganan.

This study was funded by an educational/research grant from Cadence Pharmaceuticals.

We express our appreciation to the following individuals for assis-tance with technical support, manuscript preparation, and editorial processing: J. Streit, M. Janechek, M. Stilwell, and N. O’Mara-Mor-rissey.

REFERENCES

1.Almirante, B., D. Rodriguez, B. J. Park, M. Cuenca-Estrella, A. M. Planes, M. Almela, J. Mensa, F. Sanchez, J. Ayats, M. Gimenez, P. Saballs, S. K. Fridkin, J. Morgan, J. L. Rodriguez-Tudela, D. W. Warnock, and A. Pahissa.

2005. Epidemiology and predictors of mortality in cases ofCandida blood-stream infection: results from population-based surveillance, Barcelona, Spain, from 2002 to 2003. J. Clin. Microbiol.43:1829–1835.

2.Anderegg, T. R., T. R. Fritsche, and R. N. Jones.2004. Quality control guidelines for MIC susceptibility testing of omiganan pentahydrochloride (MBI 226), a novel antimicrobial peptide. J. Clin. Microbiol.42:1386–1387. 3.Armstrong-James, D.2007. InvasiveCandidaspecies infection: the impor-tance of adequate empirical antifungal therapy. J. Antimicrob. Chemother.

60:459–460.

4.Bouza, E., R. San Juan, P. Munoz, J. Pascau, A. Voss, and M. Desco.2004. A European perspective on intravascular catheter-related infections: report on the microbiology workload, aetiology and antimicrobial susceptibility (ESGNI-005 study). Clin. Microbiol. Infect.10:838–842.

5.Centers for Disease Control and Prevention.2005. Reduction in central line-associated bloodstream infections among patients in intensive care units—Pennsylvania, April 2001-March 2005. Morb. Mortal. Wkly. Rep.

54:1013–1016.

6.Clinical and Laboratory Standards Institute.2005. M27-S2. Quality control minimal inhibitory concentration (MIC) limits for broth microdilution and MIC interpretive breakpoints. CLSI, Wayne, PA.

7.Garland, J. S., C. P. Alex, C. D. Mueller, D. Otten, C. Shivpuri, M. C. Harris, M. Naples, J. Pellegrini, R. K. Buck, T. L. McAuliffe, D. A. Goldmann, and D. G. Maki.2001. A randomized trial comparing povidone-iodine to a chlorhexidine gluconate-impregnated dressing for prevention of central ve-nous catheter infections in neonates. Pediatrics107:1431–1436.

8.Gordon, Y. J., E. G. Romanowski, and A. M. McDermott.2005. A review of antimicrobial peptides and their therapeutic potential as anti-infective drugs. Curr. Eye Res.30:505–515.

9.Isaacson, R. E.2003. MBI-226. Micrologix/Fujisawa. Curr. Opin. Investig. Drugs4:999–1003.

10.Melo, M. N., and M. A. Castanho.2007. Omiganan interaction with bacterial membranes and cell wall models. Assigning a biological role to saturation. Biochim. Biophys. Acta1768:1277–1290.

11.Munoz, P., E. Bouza, R. San Juan, A. Voss, J. Pascau, and M. Desco.2004. Clinical-epidemiological characteristics and outcome of patients with cath-eter-related bloodstream infections in Europe (ESGNI-006 study). Clin. Microbiol. Infect.10:843–845.

12.National Committee for Clinical Laboratory Standards.2002. M27-A2. Ref-erence method for broth dilution antifungal susceptibility testing of yeasts; approved standard, 2nd ed. NCCLS, Wayne, PA.

13.National Committee for Clinical Laboratory Standards.2002. M38-A. Ref-erence method for broth dilution antifungal susceptibility testing of filamen-tous fungi; approved standard. NCCLS, Wayne, PA.

14.National Nosocomial Infections Surveillance System Report. 2004. Data summary from January 1992 through June 2004, issued October 2004. Am. J. Infect. Control32:470–485.

15.O’Grady, N. P., M. Alexander, E. P. Dellinger, J. L. Gerberding, S. O. Heard, D. G. Maki, H. Masur, R. D. McCormick, L. A. Mermel, M. L. Pearson, I. I. Raad, A. Randolph, and R. A. Weinstein.2002. Guidelines for the prevention of intravascular catheter-related infections. Centers for Disease Control and Prevention. MMWR Recommend. Rep.51:1–29.

16.Pittet, D., D. Tarara, and R. P. Wenzel.1994. Nosocomial bloodstream infection in critically ill patients. Excess length of stay, extra costs, and attributable mortality. JAMA271:1598–1601.

17.Ross, J. E., R. N. Jones, P. R. Rhomberg, and T. R. Fritsche.2007. In vitro activity of omiganan pentahydrochloride against⬎1,600 clinical trial isolates, abstr. 433, p. 139. 45th IDSA Annual Meeting, San Diego, CA.

18.Sader, H. S., K. A. Fedler, R. P. Rennie, S. Stevens, and R. N. Jones.2004. Omiganan pentahydrochloride (MBI 226), a topical 12-amino-acid cationic peptide: spectrum of antimicrobial activity and measurements of bactericidal activity. Antimicrob. Agents Chemother.48:3112–3118.

19.Viale, P., and S. Stefani.2006. Vascular catheter-associated infections: a microbiological and therapeutic update. J. Chemother.18:235–249.