What Is MSSA?

Methicillin-sensitive Staphylococcus aureus (MSSA) is a type of bacteria that resides on the skin or inside the nose of many individuals without causing illness. However, when the bacteria enter the body through a break in the skin or other vulnerable areas, they can lead to infections, ranging from mild to life-threatening.

Unlike MRSA (methicillin-resistant Staphylococcus aureus), MSSA responds to a wider variety of antibiotics, making it easier to treat. Despite this, MSSA can still cause severe infections if not promptly diagnosed and treated. Understanding how it spreads, its symptoms, and how to prevent it is key to protecting your health.

Types of MSSA Infections

MSSA can cause different types of infections depending on where the bacteria spread:

  • Skin infections: Occur when bacteria enter through a cut, scratch, or wound.

  • Bone infections (Osteomyelitis): Develop when bacteria reach the bone through the blood or nearby infected tissues.

  • Heart infections (Endocarditis): MSSA can infect the inner lining or valves of the heart.

  • Pneumonia: Happens when MSSA invades the lungs.

  • Food poisoning: Arises from consuming food contaminated with MSSA.

  • Mastitis: Infection of breast tissue, particularly in chestfeeding individuals.

Skin Infections

Skin is the most common site for MSSA infections. Symptoms include:

  • Red, swollen area that is warm to the touch

  • Painful or tender bump filled with pus

  • Fever

  • Possible drainage of fluid

These infections can resemble boils, spider bites, or pimples.

Bone Infections (Osteomyelitis)

MSSA bacteria reaching the bone can lead to osteomyelitis. Signs may include:

  • Deep bone pain

  • Swelling and redness over the affected bone

  • Persistent fever

  • General feeling of illness or malaise

  • Excessive sweating

Heart Infections (Endocarditis)

When MSSA infects the heart, especially the valves or inner lining, symptoms can be severe:

  • Fever and chills

  • Fatigue and weakness

  • Joint and muscle pain

  • Irregular or rapid heartbeat

  • Shortness of breath

  • Cough

  • Night sweats

  • Broken blood vessels under the skin (petechiae)

Pneumonia from MSSA

If MSSA infects the lungs, it can cause bacterial pneumonia, presenting with:

  • High fever

  • Chills

  • Chest pain

  • Persistent coughing

  • Difficulty breathing

Food Poisoning

When MSSA contaminates food, it can cause food poisoning symptoms within 30 minutes to 8 hours:

  • Nausea

  • Vomiting

  • Diarrhea

  • Abdominal cramps

Mastitis

Breast infections in nursing individuals often develop due to cracked or damaged nipples:

  • Painful, swollen breasts

  • Warmth and tenderness in affected areas

  • Fever

  • Chills

How MSSA Spreads

MSSA bacteria can be transferred by:

  • Direct contact with infected skin or body fluids

  • Touching contaminated surfaces (towels, razors, doorknobs)

  • Sharing personal items

  • Improper food handling by carriers

Colonization means that a person carries the bacteria without being sick but can still infect others.

Risk Factors

Certain individuals are more susceptible to MSSA infections:

  • People with open wounds or burns

  • Those with chronic illnesses (diabetes, cancer, lung disease)

  • Immunocompromised individuals (chemotherapy, HIV, corticosteroid users)

  • Hospital patients or recent surgery patients

  • People who inject drugs

  • Athletes in contact sports

  • People who share personal items

  • Individuals with implanted medical devices (e.g., heart valves, pacemakers)

Diagnosis

Healthcare providers diagnose MSSA through:

  • Physical examination: Looking for signs of redness, warmth, swelling, or drainage

  • Skin culture: Swabbing the infected site for lab testing

  • Blood tests: To check for systemic spread

  • Imaging tests: X-rays, CT scans, or MRIs to detect internal involvement

  • Bone biopsy: Confirms bone infections

  • Stool tests: Used if food poisoning is suspected

Treatment Options

Treatment for MSSA depends on the location and severity of infection:

Antibiotics

These medications either kill or inhibit MSSA growth. Common choices include:

  • Dicloxacillin

  • Nafcillin

  • Erythromycin

  • Clindamycin

Topical or oral antibiotics are used for minor infections, while more serious infections require intravenous antibiotics.

Incision and Drainage

If abscesses or boils are present, doctors may surgically drain the pus to speed up healing. Antibiotics are usually prescribed afterward.

Surgery

Severe infections like osteomyelitis or endocarditis may require surgical removal of infected tissue or medical devices.

Prevention Strategies

You can prevent MSSA infection or transmission by:

  • Washing hands thoroughly with soap and water

  • Keeping wounds clean and covered

  • Avoiding the sharing of towels, razors, or personal hygiene items

  • Not preparing food if you have an active skin infection

  • Sanitizing frequently touched surfaces at home or in the gym

Potential Complications

If left untreated, MSSA infections can lead to:

  • Sepsis: A life-threatening systemic infection

  • Toxic shock syndrome (TSS): A severe condition caused by toxin-producing strains

  • Abscesses or deep tissue infections: Leading to long-term damage

  • Recurrent infections

  • Organ failure in critical cases

When To See a Doctor

Seek immediate care if you experience:

  • Unexplained fever or chills

  • Redness or swelling that worsens

  • Painful, draining sores

  • Symptoms of pneumonia or endocarditis

  • Severe abdominal pain after food intake

Early diagnosis and treatment are critical in preventing severe complications.

Living With MSSA

A diagnosis of MSSA does not mean lifelong infection. With appropriate antibiotics and wound care, most people fully recover. However, proper hygiene and adherence to medical instructions are essential to avoid reinfection or spreading it to others.

  • Complete all prescribed medications

  • Practice wound care and infection control

  • Inform healthcare providers of your history with MSSA