Pyogenic Skin Infection

What "pyogenic skin infection" means

Pyogenic comes from the Greek for "pus-producing". A pyogenic infection is one where bacteria trigger a strong white-blood-cell response, and the dead cells, bacteria and fluid collect as pus. Doctors also use the older word pyoderma (pus in the skin) for this group. Pyoderma gangrenosum is a confusing exception: despite its name it is an inflammatory ulcer condition, not an infection.

Skin infections are often split into:

• Purulent infections: those with pus, such as abscesses and boils. These are the pyogenic infections, and staph is usually the cause.
• Non-purulent infections: such as cellulitis and erysipelas, which cause spreading redness without a pus collection and are usually caused by strep.

This split guides treatment, as recommended by the Infectious Diseases Society of America.

Types of pyogenic skin infection

See also boils for home care of single boils.

Causes and risk factors

Staphylococcus aureus lives harmlessly in the nose or on the skin of about a third of people. It causes infection when it gets through breaks in the skin: cuts, bites, shaving nicks, scratched eczema or friction. MRSA (methicillin-resistant staph) is now a common cause of community skin abscesses. Group A strep causes some impetigo and ecthyma.

Risk factors include:

• diabetes, especially with high blood sugar
• eczema, scabies and other itchy skin conditions
• obesity and skin folds
• close-contact sports, shared razors and towels, gyms
• crowded living, such as prisons, barracks and dormitories
• injecting drug use
• weakened immunity, including chemotherapy and HIV
• recent hospital stay or antibiotic use

Pyogenic skin infection in adults

Adults most often get boils, abscesses, folliculitis and infected wounds rather than impetigo. Recurrent boils in the armpits and groin can be hidradenitis suppurativa, a chronic inflammatory condition that needs different treatment. In people with diabetes, foot infections can progress silently because of reduced sensation, so any pus or redness on the feet needs prompt review (see diabetic foot infection).

Diagnosis

Most pyogenic infections are diagnosed by looking at them. A clinician may:

• feel whether a lump is fluctuant (pus-filled) or use bedside ultrasound to find a hidden collection
• send pus for culture to identify the bacteria and its antibiotic sensitivities, especially for recurrent, severe or MRSA-suspected infections
• check blood sugar if infections keep recurring
• take blood tests and blood cultures if you have fever or look unwell

Treatment

Small boils and folliculitis

• warm, moist compresses for 10 to 15 minutes, 3 to 4 times a day, to help the boil come to a head and drain
• keep the area clean and covered once it drains
• do not squeeze or lance boils at home, which can push infection deeper
• antiseptic washes may help folliculitis

Abscesses

Incision and drainage is the main treatment. A clinician numbs the skin, opens the abscess and drains the pus. Antibiotics are added for abscesses larger than about 2 cm, multiple abscesses, surrounding cellulitis, fever, very young or old age, or weak immunity.

Antibiotics

• Topical antibiotics such as mupirocin for limited impetigo.
• Oral antibiotics for widespread impetigo, carbuncles, abscesses with spreading redness, or fever. The choice depends on local MRSA rates. Options active against MRSA include doxycycline, trimethoprim-sulfamethoxazole and clindamycin.
• IV antibiotics in hospital for severe or rapidly spreading infection.

Recurrent infections

For recurrent boils, doctors may recommend decolonization: an antibiotic ointment in the nostrils for several days, chlorhexidine body washes, and washing towels and bedding hot. Other household members may need treatment too.

Complications

• cellulitis and lymphangitis
• scarring
• bloodstream infection and sepsis
• spread to bones, joints or heart valves (rare)
• post-streptococcal kidney inflammation after strep impetigo

Prevention

• keep cuts and scrapes clean and covered until healed
• do not share towels, razors, sports gear or clothing
• shower after contact sports and clean shared equipment
• control blood sugar and treat eczema well
• wash hands regularly

Frequently asked questions

What does pyogenic skin infection mean?

It means a bacterial skin infection that produces pus. "Pyogenic" means pus-forming. Boils, carbuncles, abscesses, impetigo, infected hair follicles and infected wounds are all pyogenic skin infections, usually caused by staph or strep bacteria.

What bacteria cause pyogenic skin infections?

Staphylococcus aureus causes most, including the antibiotic-resistant form MRSA. Streptococcus pyogenes (group A strep) causes some impetigo and ecthyma. Other bacteria can be involved in bites, diabetic foot infections and wounds contaminated with soil or water.

Is a pyogenic skin infection contagious?

Yes, the bacteria can spread by direct skin contact and shared towels, razors and sports equipment, especially from draining sores. Cover wounds, wash hands and avoid sharing personal items until the infection has healed.

How is a pyogenic skin infection treated in adults?

Small boils are treated with warm compresses. Abscesses usually need incision and drainage by a clinician. Antibiotics are added when the infection is large, spreading, multiple or comes with fever, and for people with diabetes or weak immunity.

Why do I keep getting skin infections with pus?

Recurring pus-forming infections are often due to carrying staph in the nose or on the skin, diabetes, eczema, friction, or hidradenitis suppurativa in the armpits and groin. A doctor can culture the pus, check blood sugar and suggest decolonization.