5-9

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5-9. ANTI-INFECTIVE AGENTS

a. General. Anti-infective agents work to suppress local or superficial infections only. These agents do not cure the disease, but they do remove the organisms causing infection. Examples of such agents include antibacterial, antifungal, and antiparasitic medications.

b. Anti-infective Agents.

(1) Types of topical antibacterial agents include bacitracin ointment, bacitracin-Neomycin ointment, polysporin topical ointment, and Neosporin^® ointment. Bacitracin is an antibiotic obtained from Bacillus subtillis. Bacitracin is effective against a broad spectrum of organisms including streptococci, staphylococci, and spirochetes. Bacitracin ointment can be applied directly on a skin lesion. DO NOT use bacitracin on a patient who is being treated with drugs for muscular problems or kidney problems.

 

(2) Mixtures of the antibiotics bacitracin, gramicidin, neomycin, and polymyxin B are commonly used to treat superficial infections. Mixtures of these antibiotics are very effective, and it is rare that organisms become resistant to treatment. Preparations include the following:

(a) Neosporin, Neo-Polycin (Polymyxin B, Neosporin and Bacitracin) in ointment, lotion, and powder form.

 

(b) Neosporin G cream (Polymyxin B, Neomycin, Gramicidin).

 

(c) Bacimycin ointment (Bacitracin, Neomycin).

(3) Single agents used to treat infections include:

(a) Erythromycin--one percent ointment (Ilotycin).

 

(b) Chloramphenicol--one percent cream (Chloromycetin^®).

 

(c) Gentamicin—one-tenth percent cream/ointment (Garamycin^®).

 

(d) Bacitracin ointment.

 

(e) Neomycin ointment.

c. Antifungal Actions.

(1) General. A fungus is a plant-like organism of the same class to which mushrooms and molds belong. They are everywhere in our environment, and those that cause systemic infection are often geographically limited. Although fungi are common plant pathogens, only about fifty of the thousands of known species are pathogenic to humans.

 

(2) Antifungal agents. An antifungal is an agent that destroys or prevents the growth of fungi. Some agents are used topically, while others are used systemically. The successful treatment of fungal infections depends on accurate identification of the offending fungus followed by proper selection and use of an antifungal drug. Most superficial infections can be adequately treated with topical therapy. Systemic fungal infections require the use of orally or intravenously administered drugs, some of which are toxic.

 

(3) Specific antifungal agents.

(a) Tolnaftate (Tinactin^®). This is a topical antifungal agent used in the treatment of athlete's foot, jock itch, and ringworm. The dosage of the drug depends on the extent of the affected area. Tolnaftate is available as a solution, cream, powder, and as an aerosol powder. All containers should be labeled "FOR EXTERNAL USE ONLY." This drug is especially useful in treating superficial fungal infections that are resistant to other topical agents. Additionally, tolnaftate does not enter the patient's system when applied to the skin and does not produce skin sensitivity.

 

(b) Undecylenic Acid (Desenex^®). This is an antifungal agent employed in the treatment of superficial fungus infections of the skin. Since it is fungistatic (an agent that inhibits growth of fungi) and not fungicidal (a substance that destroys fungus), attention must be given to other forms of hygiene. This agent may cause irritation on raw lesions; therefore, astringents are used to assist in reducing the rawness and irritation. An example of such an astringent is zinc, which may be incorporated into ointments, powders, and aerosols.

 

(c) Iodochlorhydroxyquin (Vioform^®). This medication is chiefly used to treat amebic dysentery, but it may also be applied topically to treat various skin conditions. LIodochlorhydroxyquin exhibits antibacterial, antifungal, and antipruritic properties when it is applied to the skin. It can, therefore, be used to

treat almost every kind of eczema. Both water-soluble creams and ointments of this medication can be purchased commercially.

 

(d) Nystatin (Mucostatin^®). Nystatin is active against a number of yeasts and molds that cause "diaper rash" and thrush. Nystatin is relatively nontoxic, but nausea, vomiting, and diarrhea may occur if taken orally. This drug has staining properties, and patients using the drug should be cautioned. Nystatin is available as an ointment, in oral suspension, and in tablets.

 

(e) Selenium sulfide (Selsun^®). This agent is a topical antifungal used in the treatment of dandruff and seborrheic dermatitis. The patient should be instructed not to use this medication if blistered, raw, or oozing areas are present on the scalp, and also to keep the medication away from the eyes. Selsun^® is a prescription drug intended for external use only as is Selsun Blue^®, an over-the-counter product. Both of these products may slightly discolor light colored hair.

(4) Candidiasis (Moniliasis®). Candidiasis, a superficial fungal infection, may involve almost any skin or mucous surface of the body. These fungal infections usually affect moist skin or mucous membranes. The mouth disease thrush is an example of this type of fungal infection. Medications that are used to treat this fungal infection include the following:

(a) Amphotericin B (Fungizone^®). This agent is an antibiotic with antifungal activity and is used both topically and systemically. Amphotericin B may exert a "drying" effect on the skin, and in some cases may stain the skin. This drug is

available as a cream, lotion, ointment, and parenteral injection (intravenous or intramuscular injection).

 

(b) Nystatin (Candex, Mycostatin^®, Nilstat^®). See paragraph 5-9c(3)(d).

 

(c) Clotrimazole (Lotrimin^®). This is a broad-spectrum antifungal effective as a topical agent in the treatment of infections caused by disease-producing fungi and by Candida albicans (a yeast-like fungus responsible for thrush and vaginitis). Side effects associated with the use of this product include itching, burning, peeling, blisters, and erythema (redness).

 

(d) Miconazole (Monistat-Derm^®). Miconazole is a synthetic antifungal effective against the common dermatophytes (any fungus which can cause a skin disease). The side effects for miconazole are the same as for clotrimazole in the previous paragraph. This product is available in cream form for either topical or vaginal applications, lotions for topical application, and in an injectable form.

(5) Dermatophytosis. Dermatophytosis is any superficial fungal infection of the skin; for example, athlete's foot. Superficial skin infections are caused by dermatophytes, fungi that invade only dead skin tissue or skin appendages such as the stratum corneum of the epidermis, nails, or hair. Dermatophytes cause a variety of skin lesions from mild and noninflammatory to acute causing a strong reaction by the body's immune system. The term tinea means superficial fungal infection and in combination with a second term indicates the location of the fungal disease (e.g., corporis, meaning body). Here are several superficial fungal infections with their respective treatments.

(a) Tinea corporis (body ringworm). This fungus involves the body with the exception of the scalp, hands, feet, groin, nails, and hair. This fungus can cause a variety of skin lesions: noninflammatory, scaly plaques; inflammatory pustules; or deep, tumorous lesions. Generally, there are only one to three lesions. Small lesions can be treated with a two percent miconazole cream or a 1 percent alotrimazole cream or lotion. Either medication should be rubbed on the affected area twice a day, continuing 7 to 10 days after the lesions disappear. Medication usually cures this fungus except in persons who suffer from a disease that affects their entire system.

 

(b) Tinea pedis (athlete's foot). Ringworm of the feet, more commonly known as athlete's foot, is a common fungal infection that usually begins between the toes and eventually may appear on the arch of the foot. The most effective treatment is griseofulvin. Medication should be started as soon as the disease is diagnosed. Improvement may not be seen immediately. Griseofulvin may not cure the condition, but it does prevent the disease from becoming more severe. Tinea pedis frequently recurs, causing some patients to require treatment for many months. Complete cure of athlete's foot is difficult, but this skin problem can be controlled with long-term therapy.

 

(c) Tinea capitis (scalp ringworm). This fungus mainly attacks children, is highly contagious, and may become epidemic. There are three forms of tinea capitis: inflammatory, noninflammatory, and favus (a chronic fungus infection of the scalp). Oval patches of hair loss occur in noninflammatory tinea capitis. A boggy, pustular nodule is present in inflammatory tinea capitis, and a crusty, scaly area around the hair near its exit from the scalp is characteristic of favus. In most cases, this fungal infection can be cured by giving microcrystalline griseofulvin, one twenty-fifth to one tenth mg by mouth daily or twice daily for two weeks. This medication must be given with meals or milk. A lotion or cream of two percent miconazole or one percent clotrimazole may be rubbed in twice daily. This fungus is very persistent but usually clears up spontaneously at puberty. Even if not treated, most scalp ringworm infections will clear up spontaneously in one or two years.

 

(d) Tinea cruris (groin ringworm). This fungus, commonly called jock itch, may be caused by several organisms. The fungus is more common in men than in women, and itching may be severe. Lesions usually appear on the thighs. Tight clothing, moisture, and heat cause the fungal organisms to grow. Athletes and other individuals who perspire a lot are particularly susceptible to groin ringworm. Treatment is two percent miconazole cream or one percent clotrimazole cream applied to the lesions. The disease usually clears up promptly with treatment.

 

(e) Tinea unguium (ringworm of the nails). This fungus is caused by an organism similar to the one which causes athlete's foot. Nails become thickened, lusterless, and debris accumulates under the free edge of the nail. Eventually, the nail may separate and come off. Treatment may be successful if griseofulvin is applied until the nail has regrown completely and all infected material is gone. This process may require six to twelve months.

(6) Systemic anti-infective agents. An anti-infective agent is a drug which is used in the treatment or prevention of infections. These agents are also called chemotherapeutic agents. Antibiotics and sulfonamides are two examples of these agents. Broad spectrum antibiotics are effective against specific microorganisms in both gram-positive and gram-negative classes. Narrow spectrum antibiotics affect only a few microorganisms. The majority of these antibiotics are penicillin derivatives with a specific spectrum for gram-positive organisms only. Included in anti-infective agents are potassium penicillin G (injection and tablet form) and tetracycline tablets.

(a) Potassium penicillin G. Natural penicillins are derived from certain species of molds and other fungi. They produce their effects by inhibiting biosynthesis of cell wall mucopeptides. Therefore, all classes of penicillin are bacterial. Natural penicillins are narrow spectrum antibiotics which are primarily effective against gram-positive and a few gram-negative bacteria. The natural penicillins such as potassium penicillin G are the first drug of choice in the treatment of infection caused by gram-positive and a few gram-negative bacteria. Intramuscular injection of potassium penicillin G provides maximal blood concentration within thirty to sixty minutes. The action of the injection lasts a relatively short period of time which means that injections are required every three to four hours to maintain sufficient medication in the blood. The injection must be given deep into the muscle because of the frequency of injections and the pain produced by the medication.

 

(b) Tetracycline tablets. Tetracycline is a broad spectrum antibiotic effective against gram-positive and gram-negative bacteria. Tetracycline drugs originate from strains of streptomycin containing broth that is fermented in deep tanks. If this drug is administered orally, absorption takes place in the stomach and upper portion of the small intestine. Tetracycline clears up the skin condition of acne pustules by reducing the concentration of irritant fatty acids in the sebum. When used in the treatment of acne, the dose is 250 mg every day or twice a day. DO NOT give tetracyclines to children during tooth development. Caution anyone taking this drug to avoid antacids, milk, dairy products, iron, or foods containing aluminum, calcium, or magnesium.

d. Topical Antiparasitic Agents. These agents are destructive to itch mites (scabicide). Both lice and mites of Sarcoptes scabiei are parasites that attack humans and cause skin lesions. Lice bite the skin to obtain blood which they feed on. Leaving their eggs and excrement on the skin, lice are passed on from person to person. The Sarcoptes scabiei mite, barely visible with the naked eye, causes severe itching at night. The disease scabies caused by this mite is usually acquired by sleeping with an infested individual or by other close contact. Gamma Benzene Hexachloride ointment (lindane, Kwell^R) is the drug of choice for the treatment of lice and scabies infestations. Usually, one application is sufficient to eliminate the problem.

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