Staphylococcus aureus (Staph) is a common bacteria found on the skin and in the nose of approximately 30% of people. The bacteria cause infection when they enter the body, usually through a cut, scrape, or other break in the skin. While often causing minor infections, the progression of a staph infection can range from small skin irritation to a serious, life-threatening systemic illness. The severity depends on the bacterial strain, the site of entry, and the speed of intervention.
Initial Manifestations of Staph
The infection begins when Staphylococcus aureus colonizes a breach in the skin barrier, leading to localized inflammation. This earliest stage often presents as folliculitis, which appears as small, pus-filled bumps surrounding a hair follicle. These minor infections are generally contained and may resolve on their own.
A boil (furuncle) is a painful, pus-filled lump that develops under the skin. A carbuncle represents a cluster of interconnected boils that extend deeper into the tissue. Impetigo is a superficial manifestation involving fluid-filled blisters that rupture and form a honey-colored crust on the skin’s surface. At this point, the infection is still confined to the superficial layers of the skin.
Spread into Deeper Tissue and the Bloodstream
When the body’s defenses are overwhelmed, the bacteria can penetrate beyond the skin’s outer layers. One common invasive result is cellulitis, a spreading infection of the underlying dermis and subcutaneous fat tissue. Cellulitis appears as an area of skin that is hot, swollen, painful, and rapidly expanding, often lacking the defined pus pocket seen in a boil.
A more concerning progression is the bacteria’s entry into the bloodstream, known as bacteremia. Once the bacteria are circulating through the body, they can travel to distant sites and establish secondary infections. Bacteremia allows Staph to infect the bone, causing osteomyelitis, or the heart, leading to infective endocarditis. The presence of Staph in the blood requires immediate, aggressive treatment.
Life-Threatening Systemic Outcomes
Uncontrolled spread of the bacteria or the production of powerful toxins can lead to dangerous systemic outcomes. Sepsis occurs when the body’s response to the infection causes widespread inflammation that damages tissues and organs. The resulting organ dysfunction and dangerously low blood pressure is known as septic shock, which can quickly become fatal.
Toxic Shock Syndrome (TSS) is a life-threatening condition caused by specific toxins (superantigens) produced by certain Staph strains. These toxins cause activation of the immune system, leading to fever, rash, and multisystem organ failure. Infective endocarditis, a severe inflammation of the heart’s inner lining and valves, is a complication of bacteremia that can destroy heart tissue and cause strokes.
Stopping the Infection Cycle
Intervention is necessary to halt the infection’s progression and prevent systemic outcomes. Diagnosis begins with culturing a sample of infected tissue from a swab or, if bacteremia is suspected, drawing blood for a blood culture. These tests determine the specific type of bacteria and its susceptibility to various antibiotics.
For localized infections like boils and carbuncles, incision and drainage (I&D) is often the primary treatment, releasing the trapped pus and reducing bacterial load. Antibiotic therapy is the mainstay of treatment. However, the rise of Methicillin-resistant Staphylococcus aureus (MRSA) complicates this process. MRSA strains are resistant to common antibiotics, often requiring stronger, sometimes intravenous, medications like vancomycin or linezolid to clear the infection.