Impetigo – Causes, Symptoms, Diagnosis, Treatment

Impetigo is a highly contagious bacterial skin infection. It’s caused by the Staphylococcus Aureus bacteria. While an Impetigo skin infection is more common among children, skin-to-skin contact athletes, like wrestlers and BJJ artists, are also susceptible.

Impetigo is a bacterial infection that involves the superficial skin. The most common presentation is yellowish crusts on the face, arms, or legs. Less commonly there may be large blisters that affect the groin or armpits. The lesions may be painful or itchy. Fever is uncommon.

It is typically due to either Staphylococcus aureus or Streptococcus pyogenes. Risk factors include attending daycare, crowding, poor nutrition, diabetes mellitus, contact sports, and breaks in the skin such as from mosquito bites, eczema, scabies, or herpes. With contact, it can spread around or between people.

It generally appears on

• Face
• Nose
• Mouth
• Hands
• Forearms
• Behind the knees

Types of Impetigo

There are two main types of impetigo: Non-bullous and bullous.

Non-bullous impetigo, or impetigo contagiosa

• Around 70 percent of cases of impetigo are of this type.
• Small red blisters appear around the mouth and nose, or, occasionally, in the extremities. The blisters soon burst and ooze either fluid or pus, leaving thick, yellowish-brownish golden crusts. As the crusts dry, they leave a red mark which usually heals without scarring.
• Although the sores are not painful, they may be very itchy. It is important not to touch or scratch them to prevent the infection from spreading to other parts of the body and other people.

In rare cases, symptoms may be more severe, with a fever and swollen glands.

Bullous impetigo

• Bullous impetigo is caused by a certain strain of Staphylococcus aureus that secretes a type of toxin that targets the skin layer. It mainly affects infants under the age of 2 years.
• The toxin attacks a protein that helps keep the skin bound together. As soon as this protein is damaged, the bacteria can spread rapidly.
• Medium to large-sized fluid-filled blisters appears on the trunk, legs, and arms. The skin around the blister is red and itchy, but not sore. They often spread rapidly and eventually burst, leaving a yellow crust. The crust normally heals with no scarring.

Ecthyma 

Ecthyma is a more serious form of impetigo in which the infection penetrates deep into the skin’s second layer, the dermis. Signs and symptoms include:

• Painful fluid- or pus-filled sores that turn into deep ulcers, usually on the legs and feet
• A hard, thick, gray-yellow crust covering the sores
• Swollen lymph glands in the affected area
• Little holes the size of pinheads to the size of pennies appear after crust recedes
• Scars that remain after the ulcers heal

The blisters are not painful, but they may be very itchy. Patients must try not to touch or scratch them.

Causes and Risk Factors of Impetigo

The pathogens mainly involved in causing impetigo are

• Staphylococcus aureus – This is the most common one and causes both the bullous and non-bullous types
• Streptococcus pyogenes – This causes mainly non-bullous impetigo
• Methicillin-resistant Staphylococcus aureus (MRSA) – Impetigo is becoming resistant to a lot of antibiotics and hence this new class of bacteria is also another cause.

People who are at risk of getting impetigo are

• Children – They quickly catch these infections when they are in contact with other children who might have had it. Touching infected toys and other infected objects can lead to spreading the infection. Children in the age group 2-5 are most prone to this infection. Impetigo spreads very fast in crowded places like childcare centers and schools.
• Adults with compromised immunity – Those with diabetes and other preexisting conditions are at risk. Secondary impetigo is also possible in people who have had scabies or eczema.
• People who live in warm climates – Impetigo bacteria thrive well usually during the summer season.
• Poor hygiene habits
• Direct contact with a person who has impetigo
• Using personal items such as towels, linen or clothing of a person with impetigo
• Anemia
• Chronic dermatitis
• Malnutrition
• Crowded conditions
• Participation in skin-to-skin contact sports such as football
• Warm, humid weather
• People with diabetes or a compromised immune system

Symptom of Impetigo

Fever and swollen glands are common with this type of impetigo.

Symptoms could include

• Blisters
• Itching
• Skin Lesion
• Vesicular Rash
• Skin Lesion Crusting
• Pain
• Swollen Lymph Nodes
• Arm Pain
• Stinging of Skin
• Blanching of Skin
• First appears as a red spot or spots
• Mature into blisters.
• Blisters eventually break and oozing a clear or cloudy like fluid
• Fluid dries into a yellow-brown crust.
• Sores can be itchy and painful
• Fatigue
• Weakness of muscles
• Headaches and vomiting.

Non-bullous impetigo

• A less severe form of impetigo
• Begins as a single, red sore which forms a blister
• When the blister breaks, a yellowish exudate dries to form a crust
• Areas affected are most commonly the face and extremities (arms, legs)
• Sores are not painful but may be itchy
• Multiple lesions may form
• Minimal redness around the lesion
• Fever is rare
• Lymph nodes may be tender

Bullous impetigo

• A more severe form of impetigo
• Presents initially as rapidly enlarging soft bullae with sharp margins
• Blisters do not have a red border, but surrounding skin may be reddened
• When blister breaks, in 3-5 days, it forms an oozing, yellow crust
• Areas affected are usually moist diaper areas, armpits and legs
• Systemic symptoms more likely, such as fever and diarrhea

 Folliculitis

• Small red, often itchy, papules and/or pustules at the base of hair shafts especially on neck, groin or armpits

Furuncles or boils

• Secondary lesions which may follow folliculitis
• Start as a tender, reddened area or a folliculitis
• Progress to a hard, tender area with a white pustule at the center
• The pustule may break open and drain or maybe surgically opened
• May progress to carbuncles which are aggregates of furuncles that form an infected area under the skin. Carbuncles are reddened, tender areas from the size of a pea to as large as a golf ball which forms one or more pustules and may be accompanied by fever, fatigue and a general feeling of malaise

Diagnosis of Impetigo

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DIAGNOSIS	DISTINGUISHING FEATURES
Atopic dermatitis	Chronic or relapsing pruritic lesions and abnormally dry skin; flexural lichenification is common in adults; facial and extensor involvement is common in children
Candidiasis	Erythematous papules or red, moist plaques; usually confined to mucous membranes or intertriginous areas
Contact dermatitis	Pruritic areas with weeping on sensitized skin that comes in contact with haptens (e.g., poison ivy)
Dermatophytosis	Lesions may be scaly and red with slightly raised “active border” or classic ringworm; or maybe vesicular, especially on feet
Discoid lupus erythematosus	Well-defined plaques with an adherent scale that penetrates into hair follicles; peeled scales have “carpet tack” appearance
Ecthyma	Crusted lesions that cover ulceration rather than an erosion; may persist for weeks and may heal with scarring as the infection extends to the dermis
Herpes simplex virus	Vesicles on an erythematous base that rupture to become erosions covered by crusts, usually on the lips and skin
Insect bites	Papules usually are seen at the site of the bite, which may be painful; may have associated urticaria
Pemphigus foliaceus	Serum and crusts with occasional vesicles, usually starting on the face in a butterfly distribution or on the scalp, chest, and upper back as areas of erythema, scaling, crusting, or occasional bullae
Scabies	Lesions consist of burrows and small, discrete vesicles, often in finger webs; nocturnal pruritus is characteristic
Sweet’s syndrome	Abrupt onset of tender or painful plaques or nodules with occasional vesicles or pustules
Varicella	Thin-walled vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop

DIAGNOSIS	DISTINGUISHING FEATURES
Bullous erythema multiforme	Vesicles or bullae arise from a portion of red plaques, 1 to 5 cm in diameter, on the extensor surfaces of extremities
Bullous lupus erythematosus	The widespread vesiculobullous eruption that may be pruritic; tends to favor the upper part of the trunk and proximal upper extremities
Bullous pemphigoid	Vesicles and bullae appear rapidly on widespread pruritic, urticarial plaques
Herpes simplex virus	Grouped vesicles on an erythematous base that rupture to become erosions covered by crusts, usually on the lips and skin; may have prodromal symptoms
Insect bites	Bullae are seen with pruritic papules grouped in areas in which bites occur
Pemphigus Vulgaris	Nonpruritic bullae, varying in size from 1 to several centimeters, appear gradually and become generalized; erosions last for weeks before healing with hyperpigmentation, but no scarring occurs
Stevens-Johnson syndrome	The vesiculobullous disease of the skin, mouth, eyes, and genitalia; ulcerative stomatitis with hemorrhagic crusting is the most characteristic feature
Thermal burns	History of burn with blistering in second-degree burns
Toxic epidermal necrolysis	Stevens-Johnson–like mucous membrane disease followed by a diffuse generalized detachment of the epidermis
Varicella	Thin-walled vesicles on an erythematous base that start on trunk and spread to face and extremities; vesicles break and crusts form; lesions of different stages are present at the same time in a given body area as new crops develop

 

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Treatment of Impetigo

Many mild skin infections are self-limiting and do not require topical antibiotics. Avoid the use of topical antibiotics for mild infections to prevent the development of antibiotic resistance.

Non-pharmacological treatment

Impetigo

• Crusts may be removed with warm water or saline compresses applied for 10 minutes, 3 or 4 times daily. Some guidelines recommend the removal of crusts for cosmetic reasons and to help topical antibiotics absorb better; other guidelines suggest it is not necessary. Conflicting evidence, but it is not harmful to remove the crusts if the patient desires
• Topical disinfectants, such as chlorhexidine or hydrogen peroxide, are ineffective. Soap and water is all that is necessary for cleansing
• Wash area up to 4 times a day with soap and water
• Avoid scratching or picking sores as this may spread infection
• Wash hands often and avoids touching other parts of your body or others after touching lesions
• Keep fingernails short
• Keep the infected person’s clothing and towels separate from other members of the family. Launder frequently

Folliculitis and Furuncles

• Apply saline or warm water compresses to the affected areas for 10 to 15 minutes three times daily. This increases circulation to the area and helps the pustule to rupture and drain
• Do not squeeze the sores as this may cause the infection to spread
• Wash hands often and after touching the affected area
• Avoid tight-fitting clothing
• Shave in the direction of hair growth; avoid shaving affected area
• Sores may be covered with non-stick gauze dressings
• Try to minimize friction on affected areas

OTC drug options for superficial bacterial skin infections

These products have little evidence of efficacy for impetigo or folliculitis, but maybe an option.

• Bacitracin 500IU/g ointment applied to the area up to 3 times a day. Bacitracin is only effective against Gram-positive bacteria
• Polymyxin B sulfate/ gramicidin cream applied to the area up to 3 times a day
• Polymyxin B sulfate/ bacitracin ointment applied up to 3 times a day.
• Polymyxin B sulfate/ bacitracin/ gramicidin ointment up to 3 times a day
• Products containing polymyxin combinations have both a Gram-positive and Gram-negative spectrum of activity; however, they are not as effective as mupirocin or fusidic acid (see below)
• Bacitracin has been associated with contact dermatitis
• Acetaminophen or ibuprofen may be recommended for pain

Prescription drug options

Impetigo (mild)

• Patients are considered non-infectious after 48 hours of treatment
• Both Mupirocin and Fuscidic acid are equally efficacious

Mupirocin 2% Cream or Ointment inhibits bacterial protein synthesis. It is considered to be at least as effective as oral antibiotics when used to treat mild impetigo caused by gram-positive bacteria. (Level 1 [likely reliable] evidence)

• Each gram of product contains 20mg mupirocin. The ointment is a water-soluble base which contains polyethylene glycol. The cream is an oil and water-based emulsion
• Mupirocin penetrates outer layers of skin with minimal systemic absorption.
• Ointment provides a more occlusive treatment. If necessary, the area can be covered with gauze

Dosage

• Apply sparingly to the infected area, 2-3 times a day for 5 days. If no significant healing occurs after 48 hours refer to the patient’s primary care provider

Pregnancy

• Animal studies have not reported any safety issues but human data is limited. Only small amounts of mupirocin are absorbed after topical use and there are no reports of teratogenicity—risk appears minimal. However, consider avoiding unless the benefit outweighs the risk. Systemic agents [penicillins, cephalosporins, clindamycin, and erythromycin (except estolate)] are indicated for impetigo and are safe in pregnancy, so maybe an appropriate alternative.

Lactation: No problems documented with breastfeeding

• Anyone with hypersensitivity to propylene glycol should avoid mupirocin ointment
• Mupirocin ointment should not be applied intranasally because of propylene glycol content

Fusidic Acid 2% Cream or Sodium Fusidate 2% Ointment inhibits bacterial protein synthesis with comparable activity to mupirocin. It may be bacteriostatic or bactericidal depending on a number of bacteria causing the infection. Fusidic acid is inactive against gram-negative bacteria

• Each gram of ointment contains 2% sodium fusidate in an ointment base containing lanolin. Each gram of cream contains 2% fusidic acid
• Anyone with an allergy to lanolin should avoid fusidic acid ointment
• Up to 2% of fusidic acid is absorbed systemically.
• Ointment provides a more occlusive treatment. If possible, the area can be covered with gauze

Dosage

• Apply sparingly 3 to 4 times a day for 5 days. If no significant healing occurs within 48 hours refer to the patient’s primary care provider

Pregnancy

• Fusidic acid crosses the placenta when administered systemically. The effects of topical fusidic acid have not been studied in pregnancy, although there are no reports of teratogenicity. Systemic agents (penicillins, cephalosporins, clindamycin, and erythromycin) are indicated for folliculitis and furuncles and are safe in pregnancy, so maybe an appropriate alternative if non-pharmacologic treatment does not suffice

Lactation

• Fusidic acid is excreted to a certain extent in breast milk. The effects of topical fusidic acid have not been studied during breastfeeding
• Fucidin-H has no evidence for improved outcomes vs. fusidic acid monotherapy

Folliculitis and Furuncles

• Folliculitis should be treated with non-pharmacologic measures for 1 week. If not resolved, topical antibiotic treatment may be indicated.

Mupirocin 2% Cream or Ointment inhibits bacterial protein synthesis of Gram-positive bacteria.

• Each gram of ointment contains 20mg mupirocin in a water-soluble ointment base containing polyethylene glycol. The cream is an oil and water-based emulsion
• Penetrates outer layers of skin with minimal systemic absorption
• Ointment provides a more occlusive treatment. If necessary, the area can be covered with gauze

Dosage: Apply sparingly to the infected area, 3 times a day for 7 days

Fusidic Acid 2% Cream or Sodium Fusidate 2% Ointment inhibits bacterial protein synthesis with comparable activity to mupirocin. It may be bacteriostatic or bactericidal depending on a number of bacteria causing the infection. Fusidic acid is inactive against gram-negative bacteria.

• Each gram of ointment contains 2% sodium fusidate in an ointment base containing lanolin. Each gram of cream contains 2% fusidic acid
• Anyone with an allergy to lanolin should avoid using the fusidic acid ointment
• Up to 2% of fusidic acid is absorbed systemically
• Ointment provides a more occlusive treatment. If necessary, the area can be covered with gauze

Dosage: Apply sparingly 3 times a day for 7 days

Prevention

• Wash hands thoroughly and frequently – after using the bathroom, before cooking and eating, playing with pets and cleaning or dressing a wound
• Ensure that each family member has his or her own toothbrush, washcloth and towel
• Separate the infected person’s bed linens, towels, and clothing from those of other family members, and wash these items in hot water
• Teach your child not to share personal items such as eating utensils, clothes, towels, toothbrushes or lip balm with other children
• Clean and treat injuries with mild soap, antibacterial ointment and then cover with gauze
• Practice good personal hygiene by showering or bathing every day
• , washing your child’s hair and trimming his or her nails regularly
• Teach your child not to scratch or pick scabs, wounds or sores as the area under the nails breeds bacteria
• Keep your child at home until the infection has healed.

References

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1. https://en.wikipedia.org/wiki/Impetigo
2. https://www.mayoclinic.org/diseases-conditions/impetigo/symptoms-causes/syc-20352352
3. https://www.ncbi.nlm.nih.gov/pubmed/25250996
4. https://www.ncbi.nlm.nih.gov/books/NBK430974/
5. https://www.ncbi.nlm.nih.gov/pubmed/7899177
6. https://www.ncbi.nlm.nih.gov/books/NBK279537/
7. https://www.ncbi.nlm.nih.gov/pubmed/16218885
8. https://www.sciencedirect.com/topics/medicine-and-dentistry/impetigo
9. https://medsask.usask.ca/superficial-bacterial-skin-infections
10. https://www.sciencedirect.com/science/article/pii/S0190962287701716

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