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Anti-fungal Properties of TopicAid®

Technical Bulletin December 2003 TB4-03

Introduction

TopicAid® is a cost-effective, easily applied topical spray that promotes healing of surgical incisions, mechanical wounds and abrasions, and burns. It is indicated especially where both animal comfort and ultimate appearance of the skin/coat is important to the value of the animal. Wound healing is accelerated, and the ultimate appearance of the wound site is such that scar tissue formation is greatly reduced, an important consideration for valuable show animals. TopicAid® has also shown to be effective against the treatment of suspected chronic fungal infections in addition to acute wounds (Technical Bulletin 1-2003).

One of the important attributes of TopicAid®is its apparent anti-microbial properties (Technical Bulletin 2-2003) which is based on extensive university laboratory testing. The present study was conducted to assess the specific anti-fungal properties of TopicAid?in a controlled, laboratory setting. Fungal dermatophytes infect horses, dogs, cats and can readily cross over to humans (Kerl, 2003).

Pathogenic Fungi Tested

The following common, pathogenic fungi were acquired from the culture collection at the Center for Medical Mycology (Case Western Reserve University) or purchased from the American Type Culture Collection (ATCC, and were tested in this study:

These fungi are very common pathogens in domesticated animals and humans, responsible for many of the most common forms of dermatophytosis (Hainer, 2003). Trichophyton, for example,is one of the leading causes of hair, skin, and nail infections in humans, including scalp ringworm (tinea capitis). Microsporum canis is the most common cause of ringworm in dogs and cats, and is commonly transmitted to humans in a household with an infected pet.

Methodology Employed

Anti-fungal tests of TopicAid®were carried out in the laboratories of the Center for Medical Mycology, Case Western Reserve University, Cleveland, Ohio, USA.
The minimum inhibitory concentration (MIC) of TopicAid® against each fungal isolate was determined according to the modification of NCCLS method for susceptibility testing of dermatophytes developed at the Center for Medical Mycology (Jessup et al., 2000).


A 1:1 dilution was first prepared in DMSO in order to dissolve the TopicAid® spray. Serial dilution sprays were then made in the cell culture medium RPMI 1640 (BioWhittaker Inc.) in a range of 25 - 0.1%. Cultures were incubated for 4 days at 35? C. Inoculum size was 1 ? 3 x 103 conidia/ml.


Data were expressed as the minimal inhibitory concentration (MIC), which is defined as the lowest concentration of TopicAid® inhibiting all fungal growth. Inhibition of fungal growth was also determined as the amount of inhibition compared to growth of the control cultures (no exposure to TopicAid®).

Findings of the Study

TopicAid® showed highly potent anti-fungal properties against all seven species tested. Almost total fungal suppression occurred at TopicAid® concentrations as low as 0.4% in most fungi tested. Trichophyton rubrum and Microsporum equinum were even more susceptible, showing MICs at concentrations as low as 0.2% TopicAid® (Table 1)

Table 1. Minimal Inhibitory Concentrations of TopicAid? in eight microorganisms.

fungus

Growth inhibition can also be expressed as the amount of inhibition compared to growth control (Table 2). Again, even in concentrations as little as 0.4% TopicAid® caused nearly complete inhibition of growth of these common dermatophytes.

Table 2. Comparative inhibitory growth of fungal cultures following TopicAid® exposure.

fungus-growth

Interpretations and Conclusions

In vitro, TopicAid® shows highly effective suppression of the growth of common dermatophytic fungus. Minimal inhibitory concentrations (MIC) varied slightly, but all MICs were 0.4% or less for the seven fungal species tested.


In vitro testing in this study involved highly diluted TopicAid® in the test medium ? a typical laboratory procedure for in vitro testing of anti-fungal properties. How these in vitro data relate to the actual concentration of TopicAid® occurring when the formulation is topically applied in full strength to a wound as directed has not been determined. However, since TopicAid® is applied at full strength (100% concentration) in veterinary applications, the concentration of TopicAid® experienced by pathogens on the surface tissues of wounds or infections is likely to be very high, and certainly much higher than the effective MICs reported in this study.


In conclusion, TopicAid®has significant anti-fungal properties in vitro in a wide range of fungal dermatophytes common in both veterinary and human infections.

References

Hainer, B. L. 2003. Dermatophyte infections.
Am. Fam. Physician. 67(1):101-8.

Jessup, C.J., Warner, J., Isham, N., Hasan, I., and Ghannoum, M.A. 2000. Antifungal susceptibility testing of dermatophytes: establishing a medium for inducing conidial growth and evaluation of susceptibility of clinical isolates. J. Clin. Microbiol. 38:341-344.

Kerl, M.E. 2003. Update on canine and feline fungal diseases. Vet. Clin. North Am. Small Anim. Pract. 33:721-47.

Pomeranz A.J. and Sabnis, S.S. 2002. Tinea capitis: epidemiology, diagnosis and management strategies. Paediatr Drugs. 4:779-83.

TopicAid® is a registered trademark of Lucid Med Tec II, Ltd.