In vitro activity of a cellulose acetate phthalate topical cream against organisms associated with bacterial vaginosis

A. Robert Neuratha,*, Yun-Yao Lia, Rosemonde Mandevilleb and Lucie Richardb

a Biochemical Virology Laboratory, New York Blood Center, 310 E. 67th Street, New York, NY 10021, USA; b Biophage, Inc., Montreal, Qué. H4P 2R2, Canada

Sir,

Cellulose acetate phthalate (CAP; Eastman, Kingston, TN, USA) used as an excipient for enteric coating of tablets and capsules,1 has antiviral activity in vitro against HIV-1 and several herpesviruses.2 Micronized CAP [(23.7 g; ‘Aquateric’) containing 66–73% CAP, a polyoxyethylene– polyoxypropylene block copolymer and distilled acetylated monoglycerides used as an enteric film coating liquid (FMC, Philadelphia, PA, USA)], incorporated into a topical cream also containing 7.89 g of colloidal silica (Cabot, Tuscola, IL, USA) per 100 g of glycerol, was shown to inactivate in vitro HIV-1, several herpesviruses and sexually transmitted bacterial pathogens without affecting lactobacilli,2 essential for maintaining normal vaginal flora.3 Ingredients of the cream other than CAP were inactive.2,4 Experiments in animal models of vaginal infection by herpesvirus type 2 (HSV-2) and HIV-1 provided evidence that the CAP cream may be an inexpensive, abundant and safe candidate microbicide with broad spectrum activity4 (and unpublished results) for prevention of sexually transmitted diseases (STDs). The aim of this study was to evaluate the activity of the CAP cream against several organisms associated with bacterial vaginosis (BV) known to increase susceptibility to HIV-1 infection.3

Bacterial isolates were obtained from the ATCC. Gardnerella vaginalis (ATCC 14018), Mycoplasma hominis (ATCC 14027), Prevotella corporis (ATCC 33547) and Mobiluncus curtisii (ATCC 35241) were each grown in liquid media recommended by ATCC, and for cfu determination on the corresponding agar plates. Briefly, G. vaginalis was grown in ATCC 1685 broth and on V blood agar plates.5 Mycoplasma hominis was grown in ATCC liquid medium 243, and for colony counting the corresponding agar plates (Difco 0142) were used. The liquid cultures were maintained under aerobic conditions at 37°C and the agar plates were incubated in the presence of 5% CO2.

P. corporis and M. curtisii were grown in ATCC media 1490 and 1015, respectively. Blood agar plates were used for growth and colony counting. Plates were incubated at 37°C in an anaerobic jar containing a gas pack generating an atmosphere of 5% CO2, 10% H2 and 85% N2. Control plates were incubated in the presence of O2 to certify the absence of aerobic microorganisms.

Isolated colonies were used to check for the typical characteristics of P. corporis and M. curtisii, i.e. (i) visual observation (white colonies becoming black after 2 weeks for P. corporis; translucent, smooth and convex colonies produced after 3 days with M. curtisii); (ii) Gram's staining negativity; (iii) catalase test; (iv) absence of growth in the presence of O2.

To assess the bactericidal activity of the CAP cream, equal volumes of the cream and bacterial suspensions in 0.14 M NaCl were mixed and incubated at 37°C for 15 min. Subsequently, the mixtures were neutralized by adding sufficient amounts of 0.43 M Na3PO4.12H2O. After 5 min at 20°C, the suspensions were serially diluted 10-fold and aliquots of each dilution were inoculated on to agar plates and incubated for 72 h at 37°C (120 h for P. corporis). For M. curtisii and P. corporis, the formulation was preincubated overnight under an anaerobic gas mixture as described above.

Exposure of each organism to the CAP cream resulted in a greatly reduced cfu number (>105 fold; TableGo). This was not observed with a control formulation lacking CAP (data not shown).


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Table. Inactivation by the CAP cream of organisms associated with BV
 
Earlier studies2,4 (and our own unpublished results) suggest that the CAP cream meets criteria desirable for a vaginal microbicide: (i) no systemic spread after topical application; (ii) low cost; (iii) wide availability of all ingredients; (iv) broad specificity resulting in prevention of transmission of several STDs; (v) well-established safety record for CAP; (vi) inactivation of the respective STD pathogens, as implied in the word ‘microbicide’. The phthalic acid residues of CAP appear essential for antiviral and microbicidal activity, probably by providing a low pH buffering system and hydrophobicity, mimicking the effect of detergents while remaining in a micronized form in the vaginal environment. Data presented here indicate that the CAP cream inactivated in vitro selected aerobic and anaerobic bacterial strains associated with BV. It seems possible that a single CAP formulation could be used both prophylactically to prevent transmission of several STDs, including HIV, and therapeutically to ameliorate BV, and thereby further decrease the probability of acquiring STDs. This concept remains to be confirmed by human clinical trials.

Acknowledgments

This work was supported in part by the Marilyn M. Simpson Charitable Trust.

Notes

J Antimicrob Chemother 2000; 45: 713–714

* Corresponding author. Tel: +1-212-570-3275; Fax: +1-212-570-3299; E-mail: rneurath{at}nybc.org Back

References

1 . Lee, J. C. (1994). Cellulose acetate phthalate. In Handbook of Pharmaceutical Excipients, 2nd edn, (Wade, A. & Weller, P. J., Eds), pp. 91–3. American Pharmaceutical Association Publishers, Washington, DC.

2 . Neurath, A. R., Strick, N., Li, Y.-Y., Lin, K. & Jiang, S. (1999). Design of a ‘microbicide’ for prevention of sexually transmitted diseases using ‘inactive’ pharmaceutical excipients. Biologicals 27, 11–21.[ISI][Medline]

3 . Martin, H. L., Jr, Richardson, B. A., Nyange, P., Lavreys, L., Hillier, S. L., Chohan, B. et al. (1999). Vaginal lactobacilli, microbial flora, and risk of human immunodeficiency virus type 1 and sexually transmitted disease acquisition. Journal of Infectious Diseases 180, 1863–8.[ISI][Medline]

4 . Gyotoku, T., Aurelian, L. & Neurath, A. R. (1999). Cellulose acetate phthalate (CAP): an ‘inactive’ pharmaceutical excipient with antiviral activity in the mouse model of genital herpesvirus infection. Antiviral Chemistry and Chemotherapy 10, 327–32.[ISI][Medline]

5 . Totten, P. A., Amsel, R., Hale, J., Piot, P. & Holmes, K. K. (1982). Selective differential human blood bilayer media for isolation of Gardnerella (Haemophilus) vaginalis. Journal of Clinical Microbiology 15, 141–7.[ISI][Medline]