Bacterial skin infections account for 0.5% of outpatient visits to primary care, and are the 28th most common diagnosis in hospitalized patients. The causes vary depending on the type of infection, and the treatment will change depending on the bacteria responsible for the condition. Each infection will affect the skin in different ways.
The most common bacterial skin infections are cellulitis, erysipelas, impetigo, folliculitis, furuncles and carbuncles. All skin infections have in common inflammation; the typical findings of inflammation are warmth, redness, pain, and swelling of the affected area.
Cellulitis is a painful and erythematous (causes redness and high temperature to the touch of the skin) bacterial infection that affects the deepest layers of the skin (the dermis and subcutaneous tissue). The infection can occur in any area of the body, but it is more common on the limbs.
The clinical symptom is inflammation of the skin. A way to differentiate cellulitis from other skin conditions is because the lesion has no defined borders and the appearance of the skin changes resembling an orange peel. The symptoms include pain, discomfort, reduced mobility of the affected area, and depending on the extension of the infection fever and muscle aches and pain can be present.
Different bacteria cause cellulitis (no relation to cellulite), but the most common ones are staphylococcus aureus and streptococcus pyogenes. These bacteria typically live on the surface of a healthy skin. Cellulitis tends to appear in places where the natural barrier of the skin is loss such as surgical wounds, trauma, fungus infections, and eczema. Other factors that increase someone’s risk for cellulitis include being overweight, having chronic edema on the limbs (for example secondary to cardiac or kidney disease), and diabetes. When not treated properly the infection can progress and expand to reach other layers causing infection of the muscles and bone. In this case the infection is a lot harder to handle but not impossible to cure.
Cellulitis is most common on the limbs but when cellulitis appears in other areas like the face and around the eyes is considered an emergency and the patients’ needs to be admitted to the hospital.
For the majority of the cases, cellulitis can be managed at home with the use of oral antibiotics, typically between five to ten days. For some patients, those with larger affected areas, systemic symptoms (such as fever), or risk factors like diabetes; in hospital treatment is suggested to prevent complications. In some cases, it will be necessary to drain the cellulitis to facilitate the healing process. In general, cellulitis can be easily treated when the patients visit the doctors in the beginning of the infection.
Erysipelas are also present as a painful and erythematous bacterial infection, but unlike cellulitis, it only affects the dermis and lymphatic vessels. Because the affection is more superficial, clinically the patient will have the signs of inflammation but the borders of the erysipelas are defined, making it easy to differentiate from other infections. The most common site of infection are the limbs, but it can happen on any area of the body. Erysipelas can appear on skin that seems healthy, so it is not necessary to have a lesion that affects the natural barrier of the skin like on cellulitis.
This infection is caused almost exclusively by streptococcus pyogenes, a bacteria that lives on the skin and can be treated easily with oral antibiotics. The complications and possible risk factors are the same as in cellulitis.
Impetigo is a common bacterial skin infection among children between two and five-years old. Impetigo classifies by:
- Non-bullous: it presents as clusters of erosions, or small vesicles or pustules. The lesion has a honey-yellow crust on top. Although it can happen in any area of the body, it is very common to happen around the mouth and in areas where the barrier of the skin is lost, like wounds, and herpes simplex infection. Is caused by staphylococcus aureus and streptococcus
- Bullous: this form of impetigo presents as a large bulla. These are thin-walled pockets containing yellow fluid. Bullous impetigo is caused by staphylococcus aureus
Impetigo can be treated using topic antibiotic creams. Treatment with oral antibiotics is only required when the patient has systemic symptoms such as fever and muscle aches and pain.
Folliculitis occurs when hair follicles become inflamed. This can happen because of physical injury (like shaving) or chemical irritation. In most cases, folliculitis manifests as a painless or tender pustule (small bump that contains pus) with the hair strand in the middle of it that tends to heal on its own leaving no scarring. One or multiple lesions can happen at the same time. Folliculitis is not associated with systemic symptoms and these are only present in very rare occasions. The most common bacteria that causes folliculitis is staphylococcus aureus. Ninety percent of the people with folliculitis will not need treatment, but in those who will, topical antibiotic creams can be used to accelerate the healing process.
5. Furuncles and Carbuncles
These two bacterial skin infections appear as a complication of folliculitis. When the follicular infection progresses and penetrates deeper and extends out from the follicle. Clinically they present as abscess or boil.
A furuncle is a tender and fluctuant mass filled with purulent material. They can occur in any area of the body but are more common in areas of friction, especially in people that use tight clothing.
Carbuncles are an aggregate of infected hair follicles. They are deep and painful masses that usually open and drain. Systemic symptoms can be present with carbuncles, but not on furuncles. Patients refer to having fever and muscles aches and pain.
To treat these infections drainage is usually suggested. The doctor will make a small incision to help drain the pus. In some cases, oral antibiotic treatment is required.