Owing to the wide variety of possible causes, skin infections clinically present in a heterogenous manner and only few aspects can be generalized: Usually, a skin infection triggers an immune response, and the interactions between the causative pathogens and the patient's immune system result in an inflammation. The latter is characterized by the five cardinal signs of inflammation, i.e., by calor, dolor, rubor, tumor and functio laesa. Additionally, molecules released by microorganisms or the body's own immune cells may mediate systemic effects. Moderate to severe skin infections may thus be associated with fever, chills, hypotension and tachycardia. Streptococcus pyogenes is very likely to induce such systemic symptoms, which is reflected in its name.

• Swelling

  MRSA infections can appear like a pimple or boil, with redness, swelling, pain, or pus. Serious infections may spread into the blood and cause blood infections. [pharmacytimes.com]

  P. multocida wound infections are characterized by acute onset of erythema, pain, and swelling. This infection has rarely been reported in dermatology journals from Japan. [ncbi.nlm.nih.gov]

  Symptoms are a deep red color and swelling. A vaccination was the cause of this infection. [staph-infection-resources.com]

  NEWSLETTERS Receive the latest local updates in your inbox New York City is seeing an outbreak of a rare skin infection that comes from handling raw seafood, causing skin lesions, pain and swelling to the hands and arms and even difficulty moving fingers [nbcnewyork.com]

• Inflammation

  Infection of the skin is distinguished from dermatitis, which is inflammation of the skin, but a skin infection can result in skin inflammation. [en.wikipedia.org]

  However, the molecular mechanisms that orchestrate initiation and termination of inflammation in skin infection are incompletely understood. [ncbi.nlm.nih.gov]

  When this happens, inflammation can occur. Like any other part of your body, your skin can be involved in immune responses. Inflammation in the skin often causes a rash to form. [healthline.com]

  Purulent inflammation of hair follicles and development of small abscesses characterize furunculosis. [symptoma.com]

• Streptococcal Infection

  Systemic administration of penicillins, or erythromycin or a tetracycline in penicillin-sensitive individuals, is effective in streptococcal infections. [apps.who.int]

  Scarlet fever may accompany streptococcal pyoderma or wound infection (surgical scarlet fever). Transient lymphadenitis occurs, and significant regional lymphadenopathy is characteristic of streptococcal impetigo. [atsu.edu]

  However, because the lesions of bullous impetigo can be large and both forms of impetigo can have satellite lesions, an oral antibiotic with activity against S. aureus and group A beta-hemolytic streptococcal infection is warranted in nonlocalized cases [aafp.org]

  Streptococcal infection is usually characterised by acute onset of rapidly spreading erythema, lymphangitis and lymphadenopathy. Staphylococcal cellulitis is usually associated with purulent lesions with erythema. [nps.org.au]

• Intravenous Drugs

  Cellulitis can be caused by normal skin flora or by exogenous bacteria, and often occurs where the skin has previously been broken: cracks in the skin, cuts, blisters, burns, insect bites, surgical wounds, intravenous drug injection or sites of intravenous [en.wikipedia.org]

  Approximately 15% of the patients had a history of recent or current intravenous drug use, and 13% had diabetes mellitus. Major abscess was slightly more frequent in DISCOVER 1, as was cellulitis in DISCOVER 2. [nejm.org]

• Surgical Procedure

  This species can cause skin and soft tissue infections after trauma or surgical procedures, pulmonary infections and disseminated diseases in immunocompromised patients. It has been rarely documented after tattoo procedures. [ncbi.nlm.nih.gov]

  Curettage is a minor surgical procedure in which the doctor scrapes off the lesions. Herpes Simplex Virus The herpes simplex virus (HSV) typically causes a recurrent cluster of tender, burning blisters on or around the mouth or lips. [orthoinfo.aaos.org]

• Diarrhea

  Interestingly, administration of glucocorticoids, for the patient's nephrotic syndrome, alleviated the patient's chronic diarrhea and decreased the incidence of skin infections. [ncbi.nlm.nih.gov]

  Salmonella causes fever, diarrhea, and abdominal cramps. Symptoms typically last between 4 and 7 days. Vibrio causes diarrhea when ingested, but it can also cause severe skin infections when it comes in contact with an open wound. [onhealth.com]

  It usually develops suddenly with: A high fever Nausea and vomiting A rash on your palms and soles that resembles sunburn Confusion Muscle aches Diarrhea Abdominal pain Septic arthritis Septic arthritis is often caused by a staph infection. [mayoclinic.org]

• Blister

  MARAZZI/SCIENCE PHOTO LIBRARY Sores (non-bullous impetigo) or blisters (bullous impetigo) can start anywhere – but usually on exposed areas like your face and hands Credit: SCIENCE PHOTO LIBRARY It's also common for blisters to start around your middle [nhs.uk]

  If it is caused by staphylococcus, people will notice larger blisters that appear to contain a clear fluid. These blisters stay intact for a longer period of time compared to the smaller ones. [doctorsthatdo.org]

  Herpes present itself as a fluid filled blister on top of red skin. Once the blister breaks open it appears with a crusty painful scab 2, 3. There is no cure for the herpes virus but treatments include Valtrex and prophylactic medications. [ghsa.net]

  Symptoms include pus-filled blisters or pustules. Blisters can range in size from peas to large rings. There is often oozing honey-colored liquid and yellowish scabs. Impetigo tends to occur on the face, arms, or legs. [massgeneral.org]

  Although there are many different types of skin infections, symptoms commonly include lesions, blisters, or sores. [orthoinfo.aaos.org]

• Dermatitis

  AD was diagnosed and assessed according to the validated European Task Force on Atopic Dermatitis. DNA samples of patients were analyzed for allelic variants in the promoter and coding exon of FLG. [ncbi.nlm.nih.gov]

  Skin rashes and irritations, or contact dermatitis, are common skin disorders caused by substances that irritate the skin or cause an allergic skin reaction. [walgreens.com]

  […] of moderate to severe Atopic Dermatitis. [centerwatch.com]

  نحن نعالج الترجمة Allergic contact dermatitis is a form of contact dermatitis. It appears in the form of a rash and is the manifestation of an allergic response caused by contact with certain chemicals. [bumrungrad.com]

• Eczema

  […] into the relative risk for atypical mycobacterial infections in the setting of eczema. [ncbi.nlm.nih.gov]

  Controlling Eczema to Prevent Skin Infections Prevention is easier when eczema is under control. To help keep skin in good shape, follow these steps: Moisturize. Daily moisturizing is key. [everydayhealth.com]

  Eczema is not contagious, which means you cannot give eczema to someone else and you cannot get eczema from someone else. Sometimes when the skin is red, weepy and blistered, it may become infected. [healthnavigator.org.nz]

  Eczema also makes patients more susceptible to staph infections. [livescience.com]

• Skin Disease

  Concepts Disease or Syndrome ( T047 ) MSH D012874 SnomedCT 267839004, 156325001, 19824006, 108365000 English Disease, Infectious Skin, Diseases, Infectious Skin, Infectious Skin Disease, Infectious Skin Diseases, Skin Disease, Infectious, Skin Diseases [fpnotebook.com]

  The result reveal that Skin Diseases Expert System has been successfully detecting skin diseases and displaying the result of identification process. Cite This Paper Andino Maseleno, Md. [doi.org]

  A patient with skin infection due to Mycobacterium avium is reported. A 9-year-old female had 10 subcutaneous nodules and two ulcers on the abdomen and legs. She had no medical history of systemic disease, skin disease or immunosuppressive therapy. [ncbi.nlm.nih.gov]

  Results: Prevalence rate of caregivers" skin diseases was 76.6%. Diagnosis of Skin disease was contact dermatitis 42.5%, scabies 26.9%, and skin xerosis 25.0%. The Mean RSI score was 3.81 and MP was 4.12. [dbpia.co.kr]

• Skin Lesion

  A 42-year-old fisherman was first presented with skin lesions while fishing for hake. [ncbi.nlm.nih.gov]

  The primary treatment of an abscess or purulent skin lesion (one discharging pus) is incision and drainage. [momsteam.com]

  The SSA considers the following factors when assessing your Chronic Skin Infection Diagnosis: Skin Lesions. [disability-benefits-help.org]

• Burning Sensation

  Anthony's Fire because it can be very painful and cause an intense, burning sensation. Erysipelas is similar to cellulitis but affects different skin layers. Streptococcus is the usual culprit. [verywellhealth.com]

  The infection causes a burning sensation along with itchiness in the genital area. Thrush can occur inside your mouth too and is known as Oral thrush. Symptoms include white patches on your tongue and inner cheeks and soreness. [doctordoctor.com.au]

  Oil of oregano is quite strong and can cause a burning sensation on skin, so make sure to dilute it with vitamin E or some cod liver oil — water won't work well to dilute because it doesn't mix with oils. [wikihow.com]

Patients presenting with dermatological lesions should undergo a thorough general and dermatological examination. This approach does not only aim at clarifying whether a patient suffers from a skin infection or not, it may also allow to recognize signs indicating an underlying disease. As has been mentioned above, immunodeficient patients are at particularly high risks of contracting infectious diseases, and immunodeficiency may be caused by diseases as common as diabetes mellitus [10]. The presence of primary disorders may also affect the choice of treatment [11].

In most cases, skin infections are diagnosed clinically. The patient's response to empirical treatment may then confirm this diagnosis, or indicate the need for further diagnostic measures. It is not generally recommended to delay treatment until the causative pathogen has been isolated and defined. In moderate to severe cases, however, representative specimens should be obtained before antimicrobials are administered. If they are tested for the presence of determined microorganisms, the respective results may already be available when a change of the therapeutic regimen is required. In detail, the following techniques may be applied:

• Gram staining and microscopic examination of samples
• Isolation of pathogens and evaluation of resistance to antimicrobials
• Immunoassays
• Serological tests
• Molecular biological tests like polymerase chain reaction
• Histopathological analysis of tissue samples

• Staphylococcus Aureus

  Staphylococcus aureus (DMST 20651), Staphylococcus epidermidis (ATCC 12228) and Candida albicans (ATCC 90028). [ncbi.nlm.nih.gov]

  Particular care has to be taken if a patient proves to be infected with methicillin-resistant Staphylococcus aureus. [symptoma.com]

Treatment primarily aims at eliminating the causative pathogen, but appropriate wound care is also indicated. Either systemic and topical treatment may be indicated, depending on the extension of the dermatological lesion.

If a bacterial skin infection is suspected and an antibiogram is not yet available, antibiotics with known effectivity against Gram-positive, lactamase-resistant strains should be applied. Cephalosporins and fluoroquinolones are most frequently used, but bacteria may present with resistances to those compounds in certain geographic regions. Thus, knowledge about the local resistance situation is required to take this decision. Particular care has to be taken if a patient proves to be infected with methicillin-resistant Staphylococcus aureus. A total of more than twenty pharmacological agents are approved for the therapy of skin infections, with vancomycin, ceftaroline, tedizolid, dalbavancin, oritavancin, and telavancin being active against methicillin-resistant strains [12].

Infections with fungi are treated with antimycotics, e.g., with azoles like miconazole, ketoconazole, itraconazole or fluconazole, with terbinafine, or with amorolfine [13]. Otherwise, recommendations are similar to those given above. Antifungal therapy may also be administered systemically or topically.

Antiviral therapy, preferentially with acyclovir, is required if the patient suffers from an infection with Herpesviridae, Poxviridae or other viral pathogens.

Some skin infections may require incision and drainage or even more extensive surgery.

The majority of skin infections are associated with a good to excellent prognosis, depending on the availability of proper medical attention. However, even well-treatable skin infections may considerable limit the patient's life quality. Pain, pruritus and psychological burden are only three examples for symptoms related to dermatological disorders that may interfere with carrying out everyday tasks and maintaining an active social life.

Few skin infections are life-threatening, e.g., the above mentioned staphylococcal scalded skin syndrome, but mortality may also be registered in patients suffering from seemingly uncomplicated infections with multiresistant pathogens.

Even under physiological conditions, many species of microorganisms colonize the human skin. Here, it is important to distinguish a colonization from an infection: A person does benefit from the presence of several microorganisms on their skin, while others are rather classified as commensals. The entirety of those microorganisms constitutes the physiological skin flora, and its composition varies depending on the precise area of skin in question, on endogenous host factors and exogenous environmental factors. In general, species pertaining to bacterial genres Corynebacterium, Propionibacterium and Staphylococcus are most abundant [1]. With regards to fungi, Malassezia spp. dominate the microbiome. Little is known about viruses being part of the skin flora.

Moreover, the skin disposes of non-specific and specific defense mechanisms to prevent a skin infection. Keratinocytes, for instance, may release antimicrobial peptides and cytokines, namely defensins, histatins and cathelicidin as well as IL-1β, IL-6, IL-10 and TNF-α, among others [2] [3] Some are released constitutively, others upon stimulation by microbial structures or pro-inflammatory cytokines.

In sum, for a skin infection to take place, one or more of the following conditions need to be fulfilled:

• Breakdown of physical barrier, e.g., in case of wounds
• Deficiency of non-specific or specific immunity
• Highly virulent pathogen or large infectious dose

A complete list of possible etiologic agents cannot be provided, but some examples shall be given:

• Staphylococcus aureus, including methicillin-resistant strains
• β-hemolytic Streptococcus spp.
• Dermatophytes like Trichophyton spp. and Microsporum canis
• Yeasts like Candida spp. and Malassezia spp.
• Herpes simplex virus and varicella zoster virus
• Human papillomavirus
• Molluscum contagiosum virus and other Poxviridae

In general, skin infections are very common and may affect men and women, people of all races and age groups. However, incidence, prevalence and distribution of determined skin infections vary significantly. Tinea pedis is a dermatophytic infection of interdigital areas of the foot, and the disease' prevalence has been reported to be about 3% in the general population and up to 60% in selected populations at high risks [4]. Incidence rates increase with age and men are affected more often than women. Similarly high prevalence rates have been reported for impetigo, a disease caused by an infection with Gram-positive cocci: In Australia and Oceania, approximately 40% of the population show signs of impetigo [5]. On the other hand, Staphylococcus aureus may induce staphylococcal scalded skin syndrome, a rare type of skin infection typically diagnosed in neonates and infants. This life-threatening disease only affects about 1 in 10,000,000 habitants per year [6].

Both from an epidemiological and a clinical point of view, the increased incidence of skin infections with methicillin-resistant Staphylococcus aureus is alarming [7].

The skin is composed of epidermis and dermis as well as skin appendages like sweat glands, sebaceous glands, hairs and nails. For pathogens to reach deeper layers of the skin, they need to overcome the epidermis. This is most easily done if the patient presents a cut or laceration, or an insect bite. However, the precise point of entry is not always traceable.

Distinct medical terms have been coined to describe skin infections that compromise its individual components, and those terms may already imply if an infection is mild or severe, if its acute or chronic. The following list shall serve as an orientation to this end:

• Impetigo is a superficial skin infection mainly diagnosed in pediatric patients. Staphylococcus aureus is the causative pathogen of bullous impetigo; β-hemolytic Streptococcus spp., mainly Streptococcus pyogenes, cause non-bullous impetigo.
• If not adequately cared for, impetigo may turn into ecthyma, a type of skin infection that extends into the dermal layer. Lesions are often covered by eschar-like indurated plaques. Development of ecthyma is frequently associated with occlusion of impetigo, poor general hygiene and immunodeficiency due to malnutrition.
• Erysipelas also refers to an infection of the upper layers of the skin, but this type of skin infection involves lesions of lymphatic vessels. It is most frequently caused by Streptococcus pyogenes, and other β-hemolytic Streptococcus spp. play minor roles in erysipelas etiology.
• Cellulitis refers to a poorly demarcated inflammation of the dermis and subcutaneous tissues, and pathogens usually enter through damaged skin. Of note, pathogens may also cause cellulitis after hematogenous or lymphatic spread from distant foci of infection. The most common etiologic agents of cellulitis are β-hemolytic Streptococcus spp. and Staphylococcus aureus [8].
• Pyoderma is a deep skin infection associated with pus formation. Similar to the aforedescribed conditions, Gram-positive cocci account for the majority of pyoderma cases. Of note, pyoderma gangrenosum is a skin disease of unknown etiology. It is marked by deep ulcers and necrotizing areas, but intents to isolate causative pathogens usually yield negative results.
• Folliculitis describes an inflammation of hair follicles; it is most commonly caused by an infection with Staphylococcus aureus, Pseudomonas aeruginosa or fungi. Accordingly, folliculitis can be detected in patients suffering from tinea capitis, tinea corporis and tinea pedis, among others.
• Purulent inflammation of hair follicles and development of small abscesses characterize furunculosis [9].
• Warts are the result of benign epithelial growth triggered by an infection with human papillomavirus, which is largely facilitated by pre-existing epithelial lesions.

All measures aiming at the preservation of the integrity of the skin and a strong immune system may help to reduce the individual risk of skin infections. With regards to the former, both a lack of skin hygiene as well as an excess to this effect may have detrimental consequences. The physiological skin flora protects from infections by means of competitive exclusion. Thus, alterations of the normal microbiome may predispose for skin infections.

Moreover, direct contact to contaminated skin or surfaces should be avoided. To this end, it is recommended to cover wounds, not to share personal hygiene products, to wash hands regularly, and to use disinfectants when necessary.

The skin is the human's largest organ and covers an area of approximately 1.8 square meters in adults [1]. It fulfills a myriad of functions, one of them being to protect the human body from noxious agents present in its environment. Since the skin constitutes the interface with the outside world, it is continuously exposed to such noxious agents, e.g., to bacterial, fungal or viral microorganisms. Under determined conditions, which are discussed further in the following sections of this article, those microorganisms may invade the patient's skin and start to multiply in excess. This way, a skin infection develops.

The vast majority of skin infections are not life-threatening, but they may considerably restrict the patient's quality of life. Their diagnosis is usually based on physical examination alone, and treatment is often chosen empirically. And indeed, this rapid, low-cost approach to therapy may work since most types of skin infection are caused by only few distinct pathogens. However, it also bears the risk of misdiagnosis, inappropriate treatment and spread of infection. Thus, further diagnostic measures are indicated in case of severe skin infections, e.g., isolation and determination of the causative pathogen and histopathological analysis of skin biopsy samples.

Skin infection is a very general term; it refers to the invasion and multiplication of pathogens within the patient's skin. Skin infections may be provoked by bacteria, fungi and viruses, whereby the most common causative agents are Staphylococcus aureus, Streptococcus spp., and dermatophytes. Distinct skin infections vary largely regarding their manifestation, their severity and extension, as well as their distribution across the population.

Some types of skin infection are very common, e.g., impetigo, superficial, bacterial infection mainly diagnosed in pediatric patients, and tinea pedis, which is also known as "athlete's foot"; others are rare. Although few skin infections are life-threatening, pain, pruritus and psychological stress associated with such diseases may considerably reduce the patient's quality of life. The vast majority of those infections is curable, but affected individuals tend to delay medical checks until the infection spread. This behavior leads to prolonged treatment times, higher costs and possibly a worse prognosis. Thus, it is recommended to consult a physician in a timely manner, and to learn about possible preventive measures. The physician may clear any doubts regarding a proper skin hygiene.

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