Leptotrichia and leptothrix: linguistic incident, or difficulties of microbiological diagnostics?

Abstract

In medical literature bacteria of the genera Leptotrix and Leptotrichia are often considered as identical. Actually, they are antipodes, standing very far apart from each other in evolutionary terms. The confusion arose due to morphological similarity (filamentous forms). Leptotrix is a type of iron bacteria that live in neutral and slightly acidic fresh waters with a very low concentration of organic matter. The energy metabolism of leptotrix is strictly aerobic, oxidative, and chemoorganoheterotrophic (they oxidize divalent iron ions into trivalent iron to produce energy). Its clinical role has not yet been proven. Bacteria of the genus Leptotrichia are normal inhabitants of the oral cavity, urogenital tract and intestine of humans, they are strict anaerobes (some strains are microaerophiles). They cause inflammatory diseases in patients with immunosuppression of different genesis. However, assessment of their clinical role, when they are isolated from non-sterile habitats, requires the use of a skilled ecological approach, including knowledge of the dynamics of cell numbers, the dominance of a particular species, etc. It is absolutely unacceptable to diagnose the diseases caused by leptotrichia on the base of smear microscopy results (for example, smears of discharge from urogenital tract).