Gram-negative toe web infection is a relatively common infection. It is commonly found on people who are engaged in athletic activities while wearing closed-toe or tight fitting shoes. It grows in a moist environment. Gram-negative is mixed bacterial infection with the following organisms:

- Moraxella

- Alcaligenes

- Acinetobacter

- Pseudomonas

- Proteus

- Erwinia

This mixing of infection and organisms may also cause a mild secondary infection of tinea pedis.

A recent retrospective study of all cases of Ecthyma gangrenosum from 2004-2010 in a university hospital in Mexico shows that neutropenia in immunocompromised patients is the most common risk factor for ecthyma gangrenosum.

The newborn`s exposure to the maternal vaginal bacterial flora which contains aerobic and anaerobic bacterial flora can lead to the development of anaerobic bacterial infection. These infections include cellulitis of the site of fetal monitoring (caused by "Bacterodes" spp.), bacteremia, aspiration pneumonia (caused by "Bacterodes" spp.), conjunctivitis (caused by clostridia,) omphalitis (caused by mixed flora), and infant botulism. Clostridial species may play a role in necrotizing enterocolitis. Management of these infection necessitates treating of the underlying condition(s) when present, and administration of proper antimicrobial therapy

Condition predisposing to anaerobic infections include: exposure of a sterile body location to a high inoculum of indigenous bacteria of mucous membrane flora origin, inadequate blood supply and tissue necrosis which lower the oxidation and reduction potential which support the growth of anaerobes. Conditions which can lower the blood supply and can predispose to anaerobic infection are: trauma, foreign body, malignancy, surgery, edema, shock, colitis and vascular disease. Other predisposing conditions include splenectomy, neutropenia, immunosuppression, hypogammaglobinemia, leukemia, collagen vascular disease and cytotoxic drugs and diabetes mellitus. A preexisting infection caused by aerobic or facultative organisms can alter the local tissue conditions and make them more favorable for the growth of anaerobes. Impairment in defense mechanisms due to anaerobic conditions can also favor anaerobic infection. These include production of leukotoxins (by "Fusobacterium" spp.), phagocytosis intracellular killing impairments (often caused by encapsulated anaerobes and by succinic acid ( produced by "Bacteroides" spp.), chemotaxis inhibition (by "Fusobacterium, Prevotella" and "Porphyromonas" spp.), and proteases degradation of serum proteins (by Bacteroides spp.) and production of leukotoxins (by "Fusobacterium" spp.).

The hallmarks of anaerobic infection include suppuration, establishment of an abscess, thrombophlebitis and gangrenous destruction of tissue with gas generation. Anaerobic bacteria are very commonly recovered in chronic infections, and are often found following the failure of therapy with antimicrobials that are ineffective against them, such as trimethoprim–sulfamethoxazole (co-trimoxazole), aminoglycosides, and the earlier quinolones.

Some infections are more likely to be caused by anaerobic bacteria, and they should be suspected in most instances. These infections include brain abscess, oral or dental infections, human or animal bites, aspiration pneumonia and lung abscesses, amnionitis, endometritis, septic abortions, tubo-ovarian abscess, peritonitis and abdominal abscesses following viscus perforation, abscesses in and around the oral and rectal areas, pus-forming necrotizing infections of soft tissue or muscle and postsurgical infections that emerge following procedures on the oral or gastrointestinal tract or female pelvic area. Some solid malignant tumors, ( colonic, uterine and bronchogenic, and head and neck necrotic tumors, are more likely to become secondarily infected with anaerobes. The lack of oxygen within the tumor that are proximal to the endogenous adjacent mucosal flora can predispose such infections.

Gram-negative toe web infection is a cutaneous condition that often begins with dermatophytosis.

Hot tub folliculitis (also known as "Pseudomonas aeruginosa" folliculitis) is a common type of folliculitis, a condition which causes inflammation of hair follicles.

This condition is caused by an infection of hair follicles due to the bacterium "Pseudomonas aeruginosa". The bacterium is commonly found in hot tubs, water slides, and such places. Children are more prone to this because they usually stay in the water longer than adults. Hot tub folliculitis appears on the skin in the form of a rash, roughly resembling chicken pox and then develops further to appear as a pimple. Hot tub folliculitis can be extremely painful and/or itchy, and left alone without scratching will go away much more quickly. If the rash is aggravated, it can stay, worsen, and spread, lasting for months. By that time, it is much more difficult to treat. The dots usually go away after about 7 to 10 days but the condition leaves a hyperpigmented lesion that goes away after a few months.

Normally, the rash does not need specific treatment and will go away on its own. Antibiotics may be prescribed in some cases. If the rash continues to appear longer than the 7- to 10-day time period, a physician should be consulted. Folliculitis that is not treated properly could worsen and cause abscesses.

The exact cause of Majocchi's granuloma is not well established however a dysfunctinoal immune system may be a causative factor. The first form of MG, the superficial perifollicular form occurs predominately on the legs of otherwise healthy young women who repeatedly shave their legs and develop hair follicle occlusions that directly or indirectly disrupt the follicle and allow for passive introduction of the organism into the dermis. Hence, the physical barrier of the skin is important because it prevents the penetration of microorganisms. Physical factors that play a major role in inhibiting dermal invasion include the interaction among keratin production, the rate of epidermal turnover, the degree of hydration and lipid composition of the stratum corneum, CO levels, and the presence or absence of hair. Keratin and/or necrotic material can also be introduced into the dermis with an infectious organism to further enhance the problem. In immunocompromised individuals, the use of topical corticosteroids may lead to a dermatophyte infection due to local immunosuppression.

Gram negative bacterial species are responsible for approximately 24% of all cases of healthcare-associated bacteremia and 45% of all cases of community-acquired bacteremia. In general, gram negative bacteria enter the bloodstream from infections in the respiratory tract, genitourinary tract, gastrointestinal tract, or hepatobiliary system. Gram-negative bacteremia occurs more frequently in elderly populations (65 years or older) and is associated with higher morbidity and mortality in this population.

"E.coli" is the most common cause of community-acquired bacteremia accounting for approximately 75% of cases. E.coli bacteremia is usually the result of a urinary tract infection. Other organisms that can cause community-acquired bacteremia include "pseudomonas aeruginosa", "klebsiella pneumoniae", and "proteus mirabilis". "Salmonella" infection, despite mainly only resulting in gastroenteritis in the developed world, is a common cause of bacteremia in Africa. It principally affects children who lack antibodies to Salmonella and HIV+ patients of all ages.

Among healthcare-associated cases of bacteremia, gram negative organisms are an important cause of bacteremia in the ICU. Catheters in the veins, arteries, or urinary tract can all create a way for gram negative bacteria to enter the bloodstream. Surgical procedures of the genitourinary tract, intestinal tract, or hepatobiliary tract can also lead to gram negative bacteremia. "Pseudomonas" and "enterobacter" species are the most important causes of gram negative bacteremia in the ICU.

There are several risk factors that increase the likelihood of developing bacteremia from any type of bacteria. These include:

- HIV infection

- Diabetes Mellitus

- Chronic hemodialysis

- Solid organ transplant

- Stem cell transplant

- Treatment with glucocorticoids

- Liver failure

In Belgium the prevalence of nosocomial infections is about 6.2%. Annually about 125,500 patients become infected by a nosocomial infection, resulting in almost 3000 deaths. The extra costs for the health insurance are estimated to be approximately €400 million/year.

Eosinophilic folliculitis associated with HIV infection typically affects individuals with advanced HIV and low T helper cell counts. It affects both men and women as well as children with HIV and is found throughout the world.

EF may also affect individuals with hematologic disease such as leukemia and lymphoma. It may also affect otherwise normal infants in a self-limited form. HIV-negative individuals can also develop EF — this is more common in Japan.

Most carbuncles, boils, and other cases of folliculitis develop from "Staphylococcus aureus".

Folliculitis starts with the introduction of a skin pathogen to a hair follicle. Hair follicles can also be damaged by friction from clothing, an insect bite, blockage of the follicle, shaving, or braids too tight and too close to the scalp. The damaged follicles are then infected by "Staphylococcus". Folliculitis can affect people of all ages.

Iron deficiency anemia is sometimes associated with chronic cases.

The organism enters directly through the breakdown of mechanical defense barriers such as mucosa or skin. Immunocompromised conditions make the patient more susceptible to this infection and septicemia. In case of septicemia, the bacteria reaches the skin via the bloodstream. Defective humoral or cellular immune system increases the risk because the organism is not able to be cleared from the bloodstream. The main mechanism of the organism that is causing the typical skin lesions is the invasion of the organism into the arteries and veins in the dermis and subcutaneous tissues of the skin. This perivascular invasion leads to nodular formation, ulceration, vasculitis and necrosis due to impaired blood supply. Perivascular involvement is achieved by direct entry of bacteria through the skin or hematogenous spreading in case of sepsis.

Superficial pustular folliculitis (also known as "Impetigo of Bockhart" and "Superficial folliculitis") is a superficial folliculitis with thin-walled pustules at the follicular openings.

The methods used differ from country to country (definitions used, type of nosocomial infections covered, health units surveyed, inclusion or exclusion of imported infections, etc.), so the international comparisons of nosocomial infection rates should be made with the utmost care.

Gram-negative folliculitis occurs in patients who have had moderately inflammatory acne for long periods and have been treated with long-term antibiotics, mainly tetracyclines, a disease in which cultures of lesions usually reveals a species of "Klebsiella", "Escherichia coli", "Enterobacter", or, from the deep cystic lesions, "Proteus".

There is no certainty about the cause of this disorder, but it is known that the bacterium Staphylococcus aureus has a central role. This bacterium can be detected in the lesions of most patients. It is unclear if a primarily sterile infection with secondary colonization by Staphylococcus aureus is present, or if this bactery itself leads at first to a strong immune reaction. Another possibility is that the toxins produced by this bacterium could act as superantigens that activate directly the T-cells over the variable domain of T-cell receptors. Nonetheless "Staphylococcus aureus" can by found in almost all patients affected by this disorder, while it is only seen in 20–30% of non-affected people.

As Staphylococcus aureus is not always found in people that suffer from folliculitis decalvans, other factors must be present. Through examinations in families it was found that there is a family connection to the occurrences, which leads to the conclusion that there is a genetic predisposition for it; for example, patients with folliculitis decalvans could have a hereditary different opening of the hair follicle that could facilitate the lodging of the bacteria. Immunologically, another possibility is that specially strong intercellular fixation protein ICAM-1 contributes to numerous inflammations with its strong effect of attracting neutrophiles such as granulocytes and lymphocytes.

Pyoderma means any skin disease that is pyogenic (has pus). These include superficial bacterial infections such as impetigo, impetigo contagiosa, ecthyma, folliculitis, Bockhart's impetigo, furuncle, carbuncle, tropical ulcer, etc. Autoimmune conditions include pyoderma gangrenosum. Pyoderma affects more than 111 million children worldwide, making it one of the three most common skin disorders in children along with scabies and tinea.

Folliculitis is the infection and inflammation of one or more hair follicles. The condition may occur anywhere on the skin except the palms of the hands and soles of the feet. The rash may appear as pimples that come to white tips on the face, chest, back, arms, legs, buttocks, and head.

Historically, there have been many types of dermatophytes that were known to cause Majocchi's granuloma. Trichophyton violaceum used to be one of the most common species of dermatophytes to cause this disease. Today, however, Trichophyton rubrum proves to be the main culprit is most cases. These fungi are keratinophilic and colonize or infect the superficial keratinized tissues (the skin, nails, and hair) of humans and animals. The organisms are usually restricted to the non-living cornified layer of the epidermis and do not invade beyond the epidermis. The fungi are usually unable to penetrate into viable tissues in a immunocompetent host and therefore many times the infection incidence is higher in immune compromised individuals. There are two forms of MG: (i) the small, perifollicular papular form, which is a localized dermal infection that usually occurs in healthy individuals and (ii) the form featuring deep subcutaneous plaques or nodular lesions that occur in immunosuppressed hosts. Tinea corporis is the name of the subset of this disease that only remains restricted to the stratum corneum. Otherwise, the atypical deeper involvement is known as Majocchi's granuloma. Because keratinophilic dermatophytes digest keratin, the introduction of keratin into the dermis may also act as a medium for continued growth of the organism.

Irritant folliculitis is a cutaneous condition and usually occurs following the application of topical medications.

The cause of EF is unknown. A variety of microorganisms have been implicated, including the mite Demodex, the yeast Pityrosporum, and bacteria. An autoimmune process has also been investigated.

Eosinophilic pustular folliculitis of infancy (also known as "Eosinophilic pustular folliculitis in infancy," "Infantile eosinophilic pustular folliculitis," and "Neonatal eosinophilic pustular folliculitis") is a cutaneous condition characterized by recurrent pruritic crops of follicular vesiculopustular lesions.

Nematode dermatitis is a cutaneous condition characterized by widespread folliculitis caused by "Ancylostoma caninum".

Fungal folliculitis (also known as Majocchi granuloma) is a skin condition characterized by a deep, pustular type of tinea circinata resembling a carbuncle or kerion.