Bacterial Bacterial skin infections affected about 155 million people and cellulitis occurred in about 600 million people in 2013. Bacterial skin infections include: •
Cellulitis, a diffuse
inflammation of
connective tissue with severe inflammation of
dermal and
subcutaneous layers of the
skin. Purulent cellulitis is often caused by
Staphylococcus aureus, including both
methicillin-sensitive (MSSA) and
methicillin-resistant S. aureus (MRSA). Non-purulent cellulitis is most often associated with group A beta-hemolytic streptococci, such as
Streptococcus pyogenes. •
Erysipelas, a bacterial infection which primarily affects superficial dermis, and often involves superficial lymphatics. Unlike cellulitis, it does not affect deeper layers of the skin. It is primarily caused by the Group A beta-hemolytic streptococci, with
Streptococcus pyogenes being the most common pathogen. Other causative agents of folliculitis include fungi (most commonly
Malassezia species), viruses (such as
herpes simplex virus), and mites (
Demodex species). •
Impetigo, a highly contagious ABSSSI (acute bacterial skin and skin structure infection) common among pre-school children, primarily associated with the pathogens
S. aureus and
S. pyogenes. Impetigo has a characteristic appearance with yellow (honey-coloured), crusted lesions occurring around mouth, nose, and chin. It is estimated that at any given time it affects 140 million people globally. Nonbullous impetigo is the most common form, representing approximately 70% of diagnosed cases. In rare instances, bullous impetigo can spread and lead to
Staphylococcal Scalded Skin Syndrome (SSSS), a potentially life-threatening infection. If not treated appropriately and in a timely fashion mycetoma infections can extend to deeper tissues like bones and joints causing osteomyelitis. Extensive osteomyelitis can necessitate surgical bone resections and even lower limb amputation. Some examples of common fungal skin infections include: •
Dermatophytosis, also known as ringworm, is a superficial fungal infection of the skin caused by several different species of fungi. The fungal genera which cause skin infections in humans include
Trichophyton,
Epidermophyton, and
Microsporum. Although dermatophytosis is fairly common fungal skin infection worldwide, it is more prevalent in areas with high humidity and environmental temperature. •
Oral candidiasis, also commonly referred to as oral thrush, is a fungal infection caused mainly by
Candida albicans, which affects mucosal membranes of the oral cavity and the tongue.
C. albicans accounts for approximately 95% of oral thrush cases. It is estimated that oral candidiasis affects approximately 2 million people every year worldwide. •
Onychomycosis, a fungal infection which predominantly affects toenails. Two most common causative agents of onychomycosis are
Trichophyton mentagrophytes and
Trichophyton rubrum. Estimated prevalence of onychomycosis in North America is between 8.7% to 13.8%.
Viral Virus-related cutaneous conditions caused by these obligate
intracellular agents derive from both
DNA and
RNA viruses. Some examples of viral skin infections include: •
Warts, benign proliferative skin lesions that are caused by
human papilloma virus (HPV). Warts vary in shape, size, appearance, and location on the body where they occur. For example,
plantar warts (verrucae plantaris), occur on the soles of the feet and appear as thick calluses. Other types of warts include
genital warts,
flat warts, mosaic warts, and
periungual warts. It is characterized by pruritic blister-like rash which may cover entire body, affecting all age groups. Rates of chickenpox are higher in countries which lack adequate immunization programs. In 2014, it has been estimated that global incidence of serious chickenpox infections requiring hospitalizations was 4.2 million. •
Hand, foot, and mouth disease (HFMD), is a common, often self-limiting viral illness which typically affects infants and children, however, it may also occur in adults. It is characterized by low grade fever and maculopapular rash on palms of the hands, soles of the feet, and around mouth. It is caused by the human
enteroviruses and
coxsackieviruses, a positive-sense single-stranded RNA viruses. == References ==