Skin and Soft Tissue Infections: Introduction, Types, Signs and Symptoms, Common Pathogens, Laboratory Diagnosis, Treatment, Prevention and Control, and Keynotes


Skin and soft tissue infections (SSTIs) encompass a broad range of infections that affect the skin, underlying connective tissues, and sometimes even the muscles. These infections can be caused by various types of bacteria, viruses, fungi, and parasites, and they can occur in individuals of all ages and backgrounds. SSTIs can range from mild and localized conditions to more severe and widespread infections that can pose significant health risks.

SSTIs are categorized based on their presentation, severity, and underlying causes. Some common types of SSTIs include:

  1. Cellulitis: This is a common bacterial infection of the skin and the tissues underneath. It often starts as a red, tender area that gradually spreads and becomes swollen. Cellulitis is usually caused by bacteria like Staphylococcus and Streptococcus.
  2. Abscesses: An abscess is a collection of pus that forms as a result of the body’s response to infection. It presents as a swollen, painful lump filled with pus, and it can occur anywhere on the body. Abscesses may need to be drained to promote healing.
  3. Folliculitis: This infection targets hair follicles and appears as small, red bumps or pustules around hair follicles. It can be caused by bacteria, fungi, or viruses.
  4. Impetigo: A highly contagious bacterial skin infection, impetigo usually affects children. It leads to the formation of small blisters or sores that burst and leave behind a honey-colored crust.
  5. Necrotizing Fasciitis: This is a severe and rapidly progressing infection that affects the deeper layers of skin and surrounding tissues. It is often referred to as “flesh-eating bacteria” and requires immediate medical intervention.
  6. Erysipelas: A bacterial infection similar to cellulitis, erysipelas typically causes raised, red patches on the skin that are well-defined and have a distinct border.
  7. Herpes Simplex Virus (HSV) Infections: These infections can cause cold sores (HSV-1) or genital herpes (HSV-2). The virus lies dormant in nerve cells and can reactivate periodically, causing painful and fluid-filled blisters.
  8. Fungal Infections: Fungal skin infections like ringworm, athlete’s foot, and jock itch are common SSTIs caused by different types of fungi. They typically lead to itching, redness, and the formation of circular or irregular patches.
  9. Parasitic Infections: Scabies, caused by tiny mites that burrow into the skin, and lice infestations are examples of parasitic skin infections that can result in intense itching and discomfort.

SSTIs can range in severity from mild and self-limiting to life-threatening. Proper diagnosis and treatment are crucial to prevent complications and the spread of infection. Treatment may involve antibiotics, antifungal medications, antiviral drugs, drainage of abscesses, wound care, and supportive measures.


Skin and soft tissue infections (SSTIs) encompass a variety of conditions caused by different microorganisms and presenting with distinct clinical features. Here are some common types of SSTIs:

  1. Bacterial Infections:
    • Cellulitis: A bacterial infection of the skin and underlying tissues, causing redness, warmth, swelling, and pain.
    • Abscess: A localized collection of pus, often caused by Staphylococcus or Streptococcus bacteria.
    • Folliculitis: Inflammation of hair follicles resulting in red bumps or pustules.
    • Furuncle (Boil): A deeper infection of a hair follicle, usually forming a painful, swollen lump filled with pus.
    • Carbuncle: A cluster of furuncles that often occurs in areas with hair follicles.
    • Erysipelas: A bacterial infection characterized by raised, well-defined red patches with a distinct border.
  2. Viral Infections:
    • Herpes Simplex Virus (HSV) Infections: HSV-1 causes cold sores, while HSV-2 causes genital herpes, both resulting in painful blisters.
    • Varicella-Zoster Virus (VZV) Infections: VZV causes chickenpox (varicella) and later reactivates as shingles (herpes zoster), causing painful blisters along nerve pathways.
    • Molluscum Contagiosum: A viral infection causing small, flesh-colored or pearly nodules on the skin.
  3. Fungal Infections:
    • Tinea Infections (Ringworm): Various forms of tinea infections affect different body parts, such as tinea corporis (body), tinea pedis (feet), tinea cruris (groin), and tinea capitis (scalp).
    • Candidiasis: An infection caused by yeast of the Candida species, commonly affecting moist skin areas like the groin and under the breasts.
    • Tinea Versicolor: A fungal infection causing patches of discolored skin, often in areas with oily skin.
  4. Parasitic Infections:
    • Scabies: Infestation by tiny mites that burrow into the skin, causing intense itching and a rash.
    • Pediculosis: Infestations by lice, including head lice (pediculosis capitis), body lice (pediculosis corporis), and pubic lice (pediculosis pubis), each causing itching and irritation.
  5. Necrotizing Soft Tissue Infections:
    • Necrotizing Fasciitis: A rapidly progressing and severe infection affecting deep layers of skin and tissues, requiring urgent medical attention.
  6. Other Infections:
    • Impetigo: A highly contagious bacterial infection causing honey-colored crusts and blisters.
    • Ecthyma: A deeper form of impetigo, involving ulceration and scab formation.
    • Erythrasma: A bacterial infection causing reddish-brown patches and scaling, commonly in skin folds.

Signs and Symptoms

Skin and soft tissue infections (SSTIs) can present with a wide range of signs and symptoms, depending on the specific type of infection and its severity. Here are some common signs and symptoms associated with various SSTIs:

  1. General Signs of Infection:
    • Redness (erythema) and warmth at the site of infection.
    • Swelling and inflammation.
    • Pain or tenderness, often described as a throbbing or sharp sensation.
    • Fever and chills, especially in more severe infections.
  2. Bacterial Infections:
    • Cellulitis: Red, swollen, and tender skin, often with expanding borders.
    • Abscess: Painful, swollen lump filled with pus, often surrounded by redness.
    • Folliculitis: Red bumps or pustules around hair follicles, accompanied by itching or discomfort.
    • Furuncle (Boil): A larger, tender, painful nodule with a central pus-filled core.
    • Erysipelas: Raised, well-demarcated red patches with distinct borders, typically on the face or legs.
  3. Viral Infections:
    • Herpes Simplex Virus (HSV) Infections: Painful, fluid-filled blisters that rupture, leaving behind shallow ulcers. Tingling or itching sensations often precede outbreaks.
    • Varicella-Zoster Virus (VZV) Infections: Chickenpox presents with itchy, fluid-filled blisters that eventually crust over. Shingles causes a painful rash along a nerve pathway.
    • Molluscum Contagiosum: Flesh-colored or pearly nodules with a central depression or plug.
  4. Fungal Infections:
    • Tinea Infections (Ringworm): Circular or oval-shaped, scaly, and red or itchy patches with a clear center.
    • Candidiasis: Red, itchy rash with well-defined borders, often in skin folds and moist areas.
    • Tinea Versicolor: Patches of discolored skin that may be lighter or darker than surrounding skin.
  5. Parasitic Infections:
    • Scabies: Intense itching, especially at night, along with a rash consisting of tiny bumps and lines.
    • Pediculosis (Lice Infestations): Itching, often more severe around the scalp (head lice), groin (pubic lice), or body (body lice).
  6. Necrotizing Soft Tissue Infections:
    • Necrotizing Fasciitis: Severe pain, rapidly progressing inflammation, skin discoloration, and signs of tissue necrosis (death) that may lead to sepsis.
  7. Other Infections:
    • Impetigo: Honey-colored crusts, blisters, or red sores that burst and ooze.
    • Ecthyma: Ulcerative lesions with a crust, often occurring as a result of untreated impetigo.
    • Erythrasma: Reddish-brown patches with scaling and mild itching, commonly in skin folds.

Common Pathogens

Skin and soft tissue infections (SSTIs) can be caused by a variety of pathogens, including bacteria, viruses, fungi, and parasites. The choice of pathogen often depends on the specific type of infection. Here are some common pathogens associated with different types of SSTIs:

Bacterial Pathogens:

  1. Staphylococcus aureus: This bacterium is a common cause of many SSTIs, including cellulitis, abscesses, furuncles (boils), and impetigo. Methicillin-resistant Staphylococcus aureus (MRSA) strains are a particular concern due to their resistance to many antibiotics.
  2. Streptococcus pyogenes (Group A Streptococcus): Known for causing streptococcal infections, this bacterium can lead to conditions like cellulitis, erysipelas, and necrotizing fasciitis (flesh-eating disease).
  3. Streptococcus agalactiae (Group B Streptococcus): Often associated with infections in newborns, this bacterium can also cause skin and soft tissue infections in adults, particularly those with underlying health conditions.
  4. Enterococcus species: These bacteria can contribute to infections like cellulitis and abscesses, especially in individuals with compromised immune systems.
  5. Clostridium species: Clostridium perfringens and Clostridium septicum are examples of bacteria that can cause severe soft tissue infections, including gas gangrene and necrotizing fasciitis.

Viral Pathogens:

  1. Herpes Simplex Virus (HSV): HSV-1 and HSV-2 can cause outbreaks of painful blisters, such as cold sores (HSV-1) or genital herpes (HSV-2).
  2. Varicella-Zoster Virus (VZV): VZV causes chickenpox during the primary infection and later reactivates as shingles (herpes zoster), which can lead to painful blisters along nerve pathways.
  3. Human Papillomavirus (HPV): Certain strains of HPV can cause genital warts, plantar warts, and flat warts on the skin.

Fungal Pathogens:

  1. Dermatophytes: These fungi cause tinea infections, commonly referred to as ringworm. Different species cause various types of tinea infections on the body, feet, groin, and scalp.
  2. Candida species: Yeast of the Candida genus can lead to candidiasis, causing infections in moist areas of the body, such as the groin, armpits, and oral cavity.

Parasitic Pathogens:

  1. Sarcoptes scabiei: The mites responsible for scabies burrow into the skin, leading to intense itching and a rash characterized by small bumps and burrows.
  2. Pediculus humanus: Different species of lice, including head lice, body lice, and pubic lice, infest various parts of the body, causing itching and skin irritation.

Laboratory Diagnosis

Laboratory diagnosis of skin and soft tissue infections (SSTIs) involves various methods to identify the causative pathogens, determine their sensitivity to antibiotics, and guide appropriate treatment. The choice of diagnostic approach depends on the type and severity of the infection. Here are some common laboratory methods used for diagnosing SSTIs:

  1. Microbiological Cultures:
    • Culture and sensitivity testing involves collecting a sample (swab, aspirate, or biopsy) from the infected site and culturing it on specific media to promote the growth of bacteria, fungi, or other microorganisms.
    • This allows identification of the causative pathogen and testing its susceptibility to various antibiotics, aiding in selecting the most effective treatment.
  2. Gram Stain:
    • A Gram stain involves staining a sample from the infection site with crystal violet and iodine, followed by safranin. It helps differentiate between Gram-positive and Gram-negative bacteria based on their cell wall structure.
    • Gram staining provides rapid preliminary information about the type of bacteria present, aiding in selecting appropriate antibiotics while waiting for culture results.
  3. Molecular Testing:
    • Polymerase Chain Reaction (PCR) and other molecular methods can quickly identify specific DNA or RNA sequences of pathogens, including bacteria, viruses, and fungi.
    • These techniques are valuable for rapid identification, especially in cases where conventional culture methods may take longer.
  4. Serological Tests:
    • Some viral and fungal infections can be diagnosed through serological tests that detect antibodies or antigens in the blood.
    • For example, herpes simplex virus (HSV) and varicella-zoster virus (VZV) infections can be diagnosed using serological tests.
  5. Histopathological Examination:
    • Biopsy samples of infected tissues can be examined under a microscope to observe cellular changes, inflammation patterns, and the presence of microorganisms.
    • This method helps diagnose fungal infections, atypical bacterial infections, and conditions like necrotizing fasciitis.
  6. Imaging Studies:
  7. Blood Culture:
    • In cases of severe infections or suspected systemic involvement, blood cultures may be performed to identify pathogens circulating in the bloodstream.
  8. Antibiotic Susceptibility Testing:
    • This testing assesses the sensitivity of isolated bacteria to various antibiotics. It helps guide treatment by identifying which antibiotics are likely to be effective against the infection.


The treatment of skin and soft tissue infections (SSTIs) depends on the type, severity, and underlying cause of the infection. In general, the goals of treatment are to eliminate the causative pathogen, alleviate symptoms, prevent complications, and promote healing. Here are some common approaches to treating SSTIs:

  1. Bacterial Infections:
    • Antibiotics: Bacterial SSTIs are often treated with antibiotics based on the identified pathogen and its sensitivity. Common antibiotics include penicillins, cephalosporins, clindamycin, and fluoroquinolones. For MRSA infections, antibiotics like vancomycin or linezolid may be used.
  2. Viral Infections:
    • Antiviral Medications: For viral SSTIs like herpes simplex and shingles, antiviral drugs like acyclovir, valacyclovir, or famciclovir can help reduce the severity and duration of symptoms.
  3. Fungal Infections:
    • Antifungal Medications: Topical or oral antifungal medications, such as terbinafine, clotrimazole, or fluconazole, are used to treat fungal SSTIs like tinea infections and candidiasis.
  4. Parasitic Infections:
    • Scabies Treatment: Permethrin or ivermectin is commonly used to treat scabies, killing the mites and their eggs.
    • Lice Treatment: Over-the-counter or prescription shampoos, creams, or lotions containing permethrin, pyrethrin, or malathion can help eliminate lice infestations.
  5. Necrotizing Soft Tissue Infections:
    • Surgical Debridement: In severe cases like necrotizing fasciitis, surgical removal of dead tissue (debridement) is often necessary to prevent the spread of infection. Antibiotics are also crucial.
  6. Supportive Measures:
    • Pain Management: Over-the-counter pain relievers or prescription medications can help manage pain associated with SSTIs.
    • Wound Care: Proper wound cleaning, dressings, and management are important for preventing secondary infections and promoting healing.
  7. Hygiene and Preventive Measures:
    • Keeping the affected area clean and dry is important for preventing further infection and promoting recovery.
    • Avoiding scratching or picking at affected areas to prevent further irritation and potential secondary infections.
    • Good hygiene practices, such as handwashing, can prevent the spread of SSTIs.
  8. Follow-Up and Monitoring:
    • It’s important to follow the prescribed treatment regimen and attend any scheduled follow-up appointments to ensure the infection is responding to treatment.

Prevention and Control

Preventing and controlling skin and soft tissue infections (SSTIs) involves a combination of personal hygiene practices, infection control measures, and awareness of risk factors. Here are some strategies to help prevent and control SSTIs:

  1. Maintain Good Hygiene:
    • Regular handwashing with soap and water is essential to prevent the spread of bacteria and viruses that can cause SSTIs.
    • Keep skin clean and dry, especially in areas prone to moisture buildup, such as skin folds.
  2. Wound Care:
    • Properly clean and care for cuts, abrasions, and other wounds to prevent them from becoming infected.
    • Apply an appropriate antiseptic or antibiotic ointment to minor wounds to help prevent bacterial growth.
  3. Avoid Sharing Personal Items:
    • Avoid sharing towels, razors, clothing, and other personal items to reduce the risk of transmitting infections.
  4. Practice Safe Sex:
    • Use barrier methods (condoms) to reduce the risk of sexually transmitted infections (STIs) that can cause genital SSTIs.
  5. Vaccination:
    • Vaccines are available to prevent some viral infections that can cause SSTIs, such as the chickenpox vaccine (varicella) and the human papillomavirus (HPV) vaccine.
  6. Hygiene in Crowded Places:
    • Practice good hygiene in crowded environments like gyms, pools, and locker rooms to minimize exposure to potential pathogens.
  7. Avoid Close Contact with Infected Individuals:
    • If someone you know has an SSTI, avoid close contact until the infection is treated and resolved to prevent transmission.
  8. Maintain a Healthy Lifestyle:
    • A healthy diet, regular exercise, adequate sleep, and stress reduction can all contribute to a strong immune system that helps protect against infections.
  9. Proper Foot Care:
    • Keep feet clean and dry, wear breathable footwear, and change socks regularly to prevent fungal infections like athlete’s foot.
  10. Infection Control in Healthcare Settings:
    • Healthcare professionals should adhere to infection control practices, including hand hygiene and proper use of personal protective equipment (PPE).
  11. Prompt Treatment:
    • Seek medical attention if you notice any signs of an SSTI, as early treatment can prevent the infection from worsening and reduce the risk of complications.
  12. Education and Awareness:
    • Educate yourself and others about the causes, symptoms, and preventive measures of SSTIs to promote overall awareness and reduce transmission.


Here are some key points to remember about skin and soft tissue infections (SSTIs):

  1. Definition: SSTIs encompass a range of infections affecting the skin, underlying tissues, and sometimes muscles. They can be caused by bacteria, viruses, fungi, or parasites.
  2. Common Types: SSTIs include cellulitis, abscesses, folliculitis, furuncles (boils), impetigo, necrotizing fasciitis, viral infections like herpes simplex and shingles, fungal infections like ringworm, and parasitic infections like scabies and lice.
  3. Signs and Symptoms: Symptoms vary based on the type and severity of infection but often include redness, swelling, pain, tenderness, itching, blisters, and discharge. Fever and systemic symptoms can occur in more severe cases.
  4. Diagnosis: Diagnosis involves clinical evaluation, laboratory tests (cultures, PCR, Gram staining), histopathological examination, and imaging studies.
  5. Treatment: Treatment depends on the underlying cause and severity. Antibiotics, antivirals, antifungals, and other medications are used. Supportive care, wound management, and surgery (debridement) may be required.
  6. Prevention: Practicing good hygiene, wound care, and avoiding close contact with infected individuals can help prevent SSTIs. Vaccination, safe sex practices, and maintaining a healthy lifestyle are also important.
  7. Risk Factors: Factors like compromised immune systems, crowded environments, poor hygiene, and chronic conditions can increase the risk of SSTIs.
  8. Complications: Untreated or severe SSTIs can lead to complications such as abscess formation, tissue necrosis, cellulitis progression, sepsis, and scarring.
  9. Hand Hygiene: Regular and thorough handwashing with soap and water is a simple yet effective measure to prevent the spread of SSTIs and other infections.
  10. Early Treatment: Timely medical attention is crucial for proper diagnosis and effective treatment, reducing the risk of complications and promoting faster recovery.
  11. Healthcare Settings: In healthcare settings, infection control practices, proper use of PPE, and adherence to guidelines are important to prevent SSTI transmission.
  12. Awareness: Educating oneself and others about SSTIs, their causes, symptoms, and prevention strategies is vital for reducing their incidence.

Further Readings

  1. Books:
    • “Fitzpatrick’s Dermatology, Ninth Edition” by Sewon Kang et al.
    • “Skin and Soft Tissue Infections: A Practical Guide” by Adam J. Singer and Henry F. Chambers.
    • “Skin Infections: Diagnosis and Treatment” by J. Schaller and S. Kumar.
  2. Medical Journals and Articles:
    • Look for articles in dermatology and infectious disease journals that focus on SSTIs, their management, and recent advancements.
    • Journals like “Journal of the American Academy of Dermatology” and “Clinical Infectious Diseases” often publish relevant articles.
  3. Guidelines and Recommendations:
    • The Centers for Disease Control and Prevention (CDC) and medical organizations like the Infectious Diseases Society of America (IDSA) provide guidelines on SSTIs and their management.
  4. Online Resources:
    • Mayo Clinic ( Offers comprehensive information on various types of skin infections and their treatments.
    • WebMD ( Provides user-friendly articles on different skin and soft tissue infections.
    • DermNet NZ ( An extensive dermatology resource with detailed information on various skin conditions, including SSTIs.
  5. Medical Institutions and Universities:
    • Medical schools’ websites and academic institutions often provide educational materials on various medical topics, including SSTIs.
  6. Health Organizations:
    • The World Health Organization (WHO) and the National Institutes of Health (NIH) may have resources and publications related to infectious diseases and skin conditions.
  7. PubMed (
    • A comprehensive database of medical literature that allows you to search for specific topics related to skin and soft tissue infections.

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