SKIN INFECTIONS

EPIDEMIOLOGY

Skin infections are very common throughout the world. The prevalence of skin infections has been reported as follows: pyoderma (prevalence range 0.2-35%, 6.9-35% in Sub-Saharan Africa), tinea capitis (1-19.7%), scabies (0.2-24%, 1.3-17% in Sub-Saharan Africa), viral skin disorders (0.4-9%, mainly molluscum contagiosum), pediculosis capitis (0-57%). Bacterial skin infections are the most common type of skin infections. The most common bacterial skin infections are reported as impetigo, folliculitis, furunculosis and abscesses, cellulitis, scarlet fever, erysipelas, erythrasma, necrotizing fasciitis and some others.⁽¹⁾

The population of children younger than 5 years old in three widely distributed villages in Punjab, Pakistan, was examined for skin disease in November 1980. Approximately 29% of the children had infectious skin disease, with pyoderma the predominant diagnostic category.⁽²⁾

PATHOPHYSIOLOGY

Skin infections usually follows a breach in the skin, such as a fissure, cut, laceration, insect bite, or puncture wound. In some cases, there is no obvious portal of entry and the breach may be due to microscopic changes in the skin or invasive qualities of certain bacteria. Organisms on the skin and its appendages gain entrance to the dermis and multiply to cause cellulitis. Facial cellulitis of odontogenic origin may also occur. Patients with toe-web intertrigo and/or tinea pedis —as well as those with lymphatic obstruction, venous insufficiency, pressure ulcers, and obesity—are particularly vulnerable to recurrent episodes of cellulitis.⁽³⁾

The vast majority of cases of cellulitis are likely caused by Streptococcus pyogenes and, to a lesser degree, by Staphylococcus aureus. In rare cases, cellulitis results from the metastatic seeding of an organism from a distant focus of infection, especially in immunocompromised individuals. Distant seeding is particularly common in cellulitis due to S pneumoniae(pneumococcus) and marine Vibrio species. Neisseria meningitidis, Pseudomonas aeruginosa, Brucella species, and Legionella species have also been reported as rare causes of cellulitis resulting from hematogenous spread.⁽⁴⁾

NATURAL HISTORY

Skin infections, which include infections of skin, subcutaneous tissue, fascia, and muscle, encompass a wide spectrum of clinical presentations, ranging from simple cellulitis to rapidly progressive necrotizing fasciitis. Diagnosing the exact extent of the disease is critical for successful management of a patient of soft tissue infection.⁽⁵⁾

The various types of skin infections, listed according to clinical presentation and anatomic location, include the following:

• Impetigo
• Folliculitis
• Furuncles
• Carbuncles
• Erysipelas
• Cellulitis
• Necrotizing fasciitis, also known as hemolytic streptococcal gangrene, Meleney ulcer, synergistic gangrene, and Fournier gangrene (when localized to the scrotum and perineal area)
• Pyomyositis

Skin infections may be caused by any of a formidable number of pathogenic microorganisms, and they may be either monomicrobial or polymicrobial. The following are the most important pathogens:

• Staphylococcus aureus(the most common pathogen)
• Streptococcus pyogenes
• Site-specific infections - Indigenous organisms (e.g. gram-negative bacilli in perianal abscesses)
• Immunocompromised hosts and complicated skin and soft tissue infections (SSTIs) - Multiple organisms or uncommon organisms (e.g. Pseudomonas aeruginosa,beta-hemolytic streptococci, Enterococcus)
• Polymicrobial necrotizing fasciitis - Mixed infection with both aerobes (e.g. streptococci, staphylococci, or aerobic gram-negative bacilli) and anaerobes (e.g. Peptostreptococcus, Bacteroides, or Clostridium)
• Monomicrobial necrotizing fasciitis:  pyogenes

PATIENT PRESENTATION

Symptoms of a skin infection include:

• Rash (localized)
• Fever
• Chills
• Skin swelling
• Skin pain
• Skin redness
• Skin tenderness
• Skin warmth
• Pus draining from the skin
• Swollen glands (localized):
• Itching and burning

Additional symptoms of skin infection include:

• Confusion
• Fever over 102 degrees F (38.8 C)
• Headache
• Joint pains
• Leg swelling (one leg)
• Leg swelling (both legs)
• Muscle aches
• Nausea
• Vomiting
• Weakness or fatigue

DIAGNOSTIC TESTS

Many minor and superficial skin and wound infections diagnosis based on a physical examination, signs and symptoms, and experience. In addition to general symptoms, many skin infections have characteristic signs, such as the appearance of a plantar wart, and typical locations on the body, such as athlete's foot between the toes. A clinical evaluation cannot, however, definitively tell the doctor which microorganism is causing a wound infection or what treatment is likely to be effective. For that, laboratory testing is required.

Laboratory tests ⁽⁶⁾
Laboratory testing is primarily used to diagnose bacterial wound infections, to identify the microorganism responsible, and to determine its likely susceptibility to specific antimicrobial drugs. Sometimes testing is also performed to detect and identify fungal infections. Sample collection may involve swabbing the surface of a wound to collect cells or pus, aspiration of fluid or pus with a needle and syringe, and / or the collection of a tissue biopsy. For fungal evaluation, scrapings of the skin may be collected.

Testing may include:

• Bacterial culture: This is the primary test used to diagnose a bacterial infection. Part of this evaluation involves the identification of methicillin-resistant Staphylcoccus aureus(MRSA) when it is present. Results of bacterial wound cultures are usually available within 24-48 hours from the time the specimen is received in the laboratory. Results of special cultures for slow-growing organisms, such as fungi or mycobacteria, may require several weeks.
• Gram stain: This test is usually performed in conjunction with the wound culture. It is a special staining procedure that allows bacteria to be evaluated under the microscope. The results of this test are usually available the same day the sample is received in the laboratory and can give the doctor preliminary information about the microorganisms that may be causing the infection.
• Antimicrobial susceptibility: A follow-up test to the wound culture. When a pathogen is identified using the wound culture, this test is used to determine the bacteria's likely susceptibility to certain drug treatments. This information helps guide the doctor in selecting appropriate antibiotics for treatment. These results are typically available about 24 hours after isolation of the microorganism that is causing the infection.

Other tests that may be ordered include:

• KOH prep: A rapid test performed to detect fungi in a sample. The sample is treated with a special solution, placed on a slide, and examined under a microscope.
• Fungal culture: Ordered when a fungal infection is suspected. Many fungi are slow-growing and may take several weeks to identify.
• AFB culture and smear: Ordered when a mycobacterial infection is suspected. Most AFB are slow-growing and may take several weeks to identify.
• Blood culture: Ordered when infection from a wound may have spread and septicaemia is suspected.
• Molecular testing to detect genetic material of a specific organism.
• Basic metabolic panel (BMP) or Comprehensive metabolic panel (CMP): May be ordered to detect underlying conditions that can affect wound healing, including a glucose test to detect diabetes

Non-laboratory-tests
In some cases, imaging scans such as ultrasounds or x-rays may be ordered to evaluate the extent of tissue damage and to look for areas of fluid / pus.

TREATMENT OPTIONS

Treatment for skin infections depends on the underlying type and severity of the infection. The location for a skin infection is also important. For example, cellulitis on the face or hand is potentially more serious than isolated cellulitis on the leg. Another important factor is the potential for antibiotic resistance. Methicillin-resistant staph infections (MRSA infections) are more serious because they require treatment with more potent antibiotics.
General measures for skin infections include rest, elevation of the infected area, warm compresses, antibiotics, or nonsteroidal anti-inflammatory medications for pain and fever. Surgery may be required to remove infected tissue, drain an abscess, or remove a skin foreign-body.
Specific treatment for a skin infection may include:

• Rest
• Elevation of the infected area - Above the heart if possible
• Warm compresses
• Nonsteroidal anti-inflammatory medications for pain and fever : Ibuprofen, Naproxen ,Ketoprofen
• Narcotic pain medication
• Antibiotics for skin infections: Selection may be guided by culturing the skin to identify the organisms causing the infection
  • Cefepime
  • Dicloxacillin
  • Cephalexin
  • Amoxicillin and clavulanate
  • Clindamycin
  • Sulfamethoxazole-and-trimethoprim
  • Ciprofloxacin
  • Cefazolin
  • Nafcillin
  • Ceftazidime
  • Ampicillin and sulbactam
  • Imipenem and cilastatin
  • Linezolid
  • Ertapenem
  • Vancomycin Metronidazole
  • Mupirocin
• Surgery to drain a skin abscess
• Surgery to remove a skin foreign body

Lifestyle Modifications

Instruct patients on following lifestyle modifications:

• Where possible, avoid or minimize wet-work.
• Avoid excessive sweating and dry conditions which are sometimes triggers.
• Avoid scratching which worsens the condition and may cause cracks allowing bacteria to enter leading to infection. Sometimes applying cold compress to area reduces itch. Keep fingernails short.
• Avoid the substance(s) causing the irritation or allergy. Avoiding all substances can be very difficult-if not impossible-especially if these substances are encountered at work. Using barrier cream, wearing gloves, and practicing glove hygiene is often helpful.
• Minimize contact with fruit juices, fruits, vegetables, raw meat while preparing food, or wear gloves.
• Protect hands by using cotton gloves as liner under vinyl gloves.
• Shampoo and style hair while wearing vinyl gloves, if possible.
• Take off rings before wet-work or hand washing.
• Use emollients frequently to help restore normal skin barrier function. A thin smear of a thick barrier cream should be applied to all affected areas before work, and reapplied after washing and whenever the skin dries out.
• Stress management-stress triggers flare-ups in many people so reducing stress may be beneficial.

PRECAUTIONS

Precautions for skin infections include:

• Gently clean the skin every day.
• Avoid skin injuries.
• Do not scratch the skin.
• Clean skin wounds immediately after they happen.
• Clean wounds every day, until they heal.
• Keep wounds covered with a bandage.

REFERENCES

1. Turkish Journal of Family Medicine & Primary Care: TJFMPC. 2015; 9(2): 65-74doi: 10.5455/tjfmpc.177379
2. Porter MJ, Mack RW, Chaudhary MA. Pediatric skin disease in Pakistan. A study of three Punjab villages. Int J Dermatol. 1984 Nov;23(9):613-6. PubMed PMID:6519873
3. Björnsdóttir S, Gottfredsson M, Thórisdóttir AS, Gunnarsson GB, Ríkardsdóttir H, Kristjánsson M, et al. Risk factors for acute cellulitis of the lower limb: a prospective case-control study.Clin Infect Dis. Nov 15 2005. 41(10):1416-22
4. Kroshinsky D, Grossman ME, Fox LP. Approach to the patient with presumed cellulitis.Semin Cutan Med Surg. Sep 2007. 26(3):168-78
5. Abrahamian FM, Talan DA, Moran GJ. Management of skin and soft-tissue infections in the emergency department.Infect Dis Clin North Am. 2008 Mar. 22(1):89-116
6. American Association for Clinical Chemistry 2016, https://www.aacc.org/