Pharmacology
Rifaximin is a semisynthetic broad spectrum antibacterial drug, derived through chemical modification of the natural antibiotic rifamycin. It has very low bioavailability due to its poor absorption after oral administration. Because of this local action within the gut and the lack of horizontal transfer of resistant genes, the development of bacterial resistance is rare, and most of the drug taken orally stays in the gastrointestinal tract where the infection takes place. Mechanism of action
Rifaximin interferes with transcription by binding to the β-subunit of bacterial RNA polymerase. This results in the blockage of the translocation step that normally follows the formation of the first phosphodiester bond, which occurs in the transcription process. This in turn results in a reduction of bacteria populations, including gas-producing bacteria, which may reduce mucosal inflammation, epithelial dysfunction, and visceral hypersensitivity. Rifaximin has broad spectrum antibacterial properties against both gram positive and gram negative anaerobic and aerobic bacteria. As a result of bile acid solubility, its antibacterial action is limited mostly to the small intestine and less so the colon. A resetting of the bacterial composition has also been suggested as a possible mechanism of action for relief of IBS symptoms. Additionally, rifaximin may have a direct anti-inflammatory effect on gut mucosa via modulation of the pregnane X receptor. Other mechanisms for its therapeutic properties include inhibition of bacterial translocation across the epithelial lining of the intestine, inhibition of adherence of bacteria to the epithelial cells, and a reduction in the expression of proinflammatory cytokines.
Tinea imbricata (also known in parts of Indonesia as “Kaskado”) is a superficial fungal infection of the skin limited to southwest Polynesia, Melanesia, Southeast Asia, India, and Central America. : 303  The skin lesions are often itchy, and mainly in the torso and limbs. The name is derived from the Latin for "tiled" (imbricata) since the lesions are often lamellar. It is often treated with griseofulvin or terbinafine.The risk of developing tinea imbricata is probably inherited as an autosomal recessive trait.Tinea imbricata is associated with Trichophyton concentricum. Tinea pseudoimbricata
The term "tinea pseudoimbricata" synonymous with "tinea indecisiva", was coined to describe a form of tinea mimicking the concentric rings of tinea imbricata, but is caused by local or systemic immunosuppression. Since then, 3 cases of Trichophyton tonsurans have been associated with it, as well as Trichophyton rubrum which can trigger mycosis fungoides. Mixed infections with scabies have been described to produce tinea pseudoimbricata.As of 2015 in India, corticosteroid–antifungal–antibacterial combinations sold as over-the-counter drug have led to an increase in chronic, recurrent, difficult to treat fungal infections of the skin, including tinea pseudoimbricata. See also
Skin lesion
List of cutaneous conditions

References


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