Skin infections
Skin infections are conditions caused by various microorganisms, including bacteria, fungi, and viruses, that affect the skin's integrity and function. These infections often arise when the body's defenses are compromised, allowing harmful pathogens to invade. Common bacterial infections include impetigo, folliculitis, and cellulitis, primarily caused by Staphylococcus aureus and Streptococcus pyogenes. Fungal infections, such as dermatophytosis, typically affect keratin-rich areas and can manifest as athlete's foot or ringworm, with conditions exacerbated by moisture and poor hygiene. Viral infections, notably herpes simplex virus (HSV), present as painful rashes with grouped vesicles and can lead to recurrent outbreaks.
Risk factors for skin infections include poor hygiene, minor skin injuries, underlying health issues, and environmental factors. Diagnosis generally relies on clinical observation and laboratory tests, including cultures for bacterial and viral infections, while treatment varies from topical ointments for mild cases to systemic therapies for more severe infections. Preventative measures include maintaining good hygiene, properly caring for wounds, and avoiding contact with contaminated surfaces or individuals. Understanding these infections can help individuals manage symptoms effectively and seek appropriate medical attention when necessary.
Skin infections
ANATOMY OR SYSTEM AFFECTED: Skin
Definition
Infections of the skin can be viral or bacterial in nature or may be caused by a fungus or parasite.
Causes
Skin infections are the result of the body’s inability to fight foreign microorganisms that may cause damage or disease if left untreated. Humans are hosts for many bacterial species that colonize the skin as normal flora. Staphylococcus aureus and Streptococcus pyogenes are infrequent resident flora, but they account for a wide variety of pyodermas (bacterial skin infections). Predisposing factors to infection include minor trauma, preexisting skin disease, poor hygiene, and, rarely, impaired host immunity. Impetigo is one example of a superficial bacterial skin infection. Others are folliculitis and cellulitis.
Dermatophytosis is infection with fungi, organisms with a high affinity for keratinized tissue, such as skin, nails, and hair. Three fungal genera (Trichophyton, Microsporum, and Epidermophyton) account for the vast majority of these infections. Fungal reservoirs for these organisms include soil, animals, and infected humans.
The skin may also be infected with viruses, small pathogens that can replicate only inside the cells of living organisms. A common example of a virus that infects skin is the herpes simplex virus (HSV). This infection causes a painful, self-limited, often recurrent dermatitis characterized by small grouped vesicles on an erythematous base. The disease is often mucocutaneous. HSV type 1 is usually associated with orofacial disease, and HSV type 2 is usually associated with genital infection.
Risk Factors
Poor hygiene habits or injury to the skin provide excellent conditions for bacterial growth. Yeast and other fungal infections are more common in immunocompromised persons, persons with diabetes, persons receiving antibiotics, and older adults. Fungi grow in moist conditions and the folds of skin. Studies have shown that tinea pedis, commonly known as athlete’s foot, is the most frequent clinical form of dermatophytosis, accounting for 59 percent of fungal skin infections. Viruses can spread easily through contact with contaminated persons or surfaces. About 85 percent of the population has antibody evidence of HSV type 1 infection. HSV type 2 infection is responsible for 20 to 50 percent of genital ulcerations in sexually active persons.
Symptoms
In general, skin infections usually involve a rash of some type as well as itching, redness, and sometimes blisters (bullae) or other types of lesions. For example, with the bacterial skin infection impetigo, two clinical types exist, nonbullous and bullous. The nonbullous type is more common and typically occurs on the face and extremities, initially with vesicles or pustules on reddened skin. The vesicles or pustules eventually rupture to leave a characteristic honey-colored (yellow-brown) crust. Bullous impetigo, almost exclusively caused by S. aureus, exhibits flaccid bullae with clear yellow fluid that rupture and leave a golden yellow crust.
Fungal and yeast infections on the body may give rise to the raised red rings of ringworm or the cracking and redness on the skin of the feet in athlete’s foot or in the groin area in jock itch. Involvement of the nails is onychomycosis; the nails may thicken, discolor, and finally crumble and fall off.
Viral infections also tend to cause rashes, itching, and redness. Herpes simplex is characterized by small grouped vesicles on an erythematous base.
Screening and Diagnosis
The diagnosis of a bacterial infection is by clinical presentation; confirmation of this infection, however, is by laboratory culture. For fungal and yeast infections, a potassium hydroxide preparation or culture helps to establish the diagnosis. A viral culture helps to confirm the diagnosis of viral skin infections, such as those caused by HSV. A direct fluorescent antibody (DFA) is a useful but less specific test. Serology is helpful only for diagnosing primary viral infections.
The Tzanck smear, a cytodiagnostic technique, can be helpful in the rapid diagnosis of HSV, varicella zoster virus, bacterial bullous impetigo, autoimmune bullous diseases, genodermatoses, and many types of cutaneous tumors. However, it is less sensitive than culture and DFA.
Other techniques used to diagnose skin infections include Wood's light, potassium hydroxide (KOH) examination, or in cases of severe infection, a computed tomography or magnetic resonance imaging (MRI) scan may be used to examine the extent of inflammation, gas formation, and infection.
Treatment and Therapy
For bacterial infections such as impetigo, topical treatment is adequate—for example, either with bacitracin (Polysporin) or mupirocin (Bactroban), applied twice daily for seven to ten days. Systemic therapy may be necessary for persons with extensive disease.
For most persons with yeast and other fungal infections, topical treatment with terbinafine (Lamisil), clotrimazole (Lotrimin, Mycelex, Canesten, Desenex), or econazole (Spectazole, Ecostatin) cream is adequate when applied twice daily for six to eight weeks.
Viral infections may also be difficult to treat. For example, primary HSV treatment may be acyclovir (Sitavig, Zovirax), given as follows: either 200 milligrams (mg) taken orally five times a day or 400 mg taken orally three times a day, both for ten days.
Prevention and Outcomes
Good general health and hygiene help to prevent bacterial skin infections, such as impetigo. Cleaning minor cuts and scrapes thoroughly with soap and clean water is also essential. To prevent yeast and other fungal infections, one should avoid sharing clothing, sports equipment, towels, or sheets; wash clothes in hot water; use fungicidal soap after suspected exposure to ringworm; and avoid walking barefoot, instead wearing appropriate protective shoes in locker rooms and sandals at the beach. Avoidance is the best prevention for many viral infections, such as HSV.
Bibliography
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