Small-colony variants (SCV) associated with specific biochemical features were described in many bacterial species. Bacteria with SCV phenotype have knocked out metabolic pathways for aerobic respiration, thus they behave like strict anaerobes.
They are handicapped in competition for nutrients with other microbes but on the other hand they are able to resist some antibiotics and survive inside eucaryotic cells. Therefore they use to cause chronic and/or recurrent infections.
Recovery of these infections is not possible without surgery. SCV phenotype seems to be a common life strategy for many bacteria.
Its occurrence and clinical importance is similar to that of biofilm formation.