Small colony variants- concluding remarks

Small colony variants (SCVs) can be isolated in vitro and in vivo under a variety of conditions, including antibiotic pressure. Various reports indicate that they are electron-deficient mutants. However, many SCVs may not revert in the presence of hemin, menadione, thiamine or thymidine and thus may not be auxotrophic mutants. It is also not known whether SCVs can revert to normal colony forms in vivo. Even though they can be isolated from many chronic infections, their role in causing these infections has not been proven conclusively. In most of the reported cases, SCVs were co-cultured with normal colony forms. Since there are no indications that the large colony forms are the revertants of SCVs, chronic infections could be due to the normal colony forms only that have persisted under those conditions. SCVs may not be responsible for fatal infections; reports associating SCVs with fatal infections are highly questionable. SCVs can be part of the normal life cycle of bacteria and may not have much clinical significance. However, the isolation of SCVs in vivo following antibiotic therapy may be indicative of the failure of antibiotics to reach throughout the site of infection at optimal concentrations, which may result in the survival of some normal bacteria and the selection of SCVs. The surviving normal bacteria may re-grow once the antibiotic pressure is removed, whereas SCVs may not have much role and may remain without causing infection since they are less virulent.

My blogs on SCVs are ending here. Next, I will start with senescent bacteria and bacterial aging model