Endosymbiosis and its significance in dermatology

Abstract

Proposed at the beginning of the 20^th to explain the origin of eukaryotic organelles from prokaryotes, endosymbiosis is now medically defined by various interaction patterns between microorganisms and their residing hosts, best exemplified by the bacterial endosymbiont Wolbachia identified in arthropods and filarial nematodes, which can influence normal development, reproduction, survival, and transmission of the hosts. Based on the transmission modes, vertical or horizontal, and the function of the endosymbionts, the host-symbiont dependence can be divided into primary or secondary.

In dermatology, the role of endosymbionts in skin ectoparasitosis has aroused great interests in the past years. Riesia pediculicola is a primary bacterial endosymbiont in head lice Pediculosis humanus, and supplement their hosts with B vitamins, especially pantothenic acid. In cimicosis, the Gram-negative Wolbachia can synthesize biotin and riboflavin, which are crucial for the growth and reproduction of the bedbug Cimex lectularius. In human demodicosis and rosacea, further study is required to prove the pathogenic role of the Gram-negative bacteria Bacillus oleronius or the Gram-postive bacteria Bacillus cereus demonstrated in the Demodex mites. The high infection rate of adult female ticks Ixodes ricinus with the Gram-negative bacteria Midichloria mitochondrii present in the mitochondria in diverse ovarian cells, with the high seroprevalence rate in tick-exposed subjects, raises the possibility that this nonpathogenic endosymbiont may play a role in immune response and successful transmission of the tick-borne pathogen. The anaerobic protozoan Trichomonas vaginalis and bacteria Mycoplasma hominis are two obligate parasites in the urogenital epithelium, with partially overlapping symptoms. Intracellular localization of Mycoplasma hominis can avoid host immune response and penetration of antibiotics, while Trichomonas vaginalis infected with Mycoplasma hominis seem to have a higher cytopathic activity and ameboid transformation rate. Further study on the biology and pathogenesis of different endosymbionts in dermatological parasitosis will help for development of new treatment modalities.

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