Mobiluncus – a contributor or cause of bacterial vaginosis

Mobiluncus is a gram-variable anaerobic bacteria found in the human vagina and bowel, with two species found – Mobiluncus curtisii and Mobiluncus mulieris. Mobiluncus was recognised in vaginal fluids as early as 1895, and were first isolated in 1913. These species have around 22 individual strains.

Mobiluncus is known to develop biofilms, are very mobile, and are better attachers to vaginal epithelial cells than G. vaginalis. Mobiluncus attaches to glucose or mannose, but if those sugars are not present, the bacteria can use adhesins – special adhesive excretions that allow attachment. The attachment is toxic to the cell. 

Mobiluncus has an association with Gardnerella vaginalis and is antibiotic resistant, particularly to the typical bacterial vaginosis (BV) treatment of metronidazole. Mobiluncus species are difficult to culture, making PCR testing important in BV. The bacteria are proving somewhat complex to define, and there isn’t a lot of information on the exact nature of the bacteria, or its role in vaginal health.

Mobiluncus is found in up to 82 per cent of women with BV, but positive PCR test results of this bacteria in women without BV ranges from zero to 38 per cent. The fact it is resistant to antibiotics is not discussed by many doctors who treat BV, and metronidazole continues to be prescribed regardless with an unacceptably high failure rate. Proper testing is therefore of paramount importance when dealing with suspected bacterial vaginosis, to determine bacteria present before treatment is prescribed.

Mobiluncus has been found in other parts of the body, including breast and umbilical abscesses, placentas, and blood cultures, in women with preterm delivery, and pelvic inflammatory disease.

Another name for Mobiluncus species, due to a coincidental co-discovery, is Falcivibrio. Mobiluncus has been likened to other bacterial families, Actinomycetales or Bacteroidaceae. Determining the Gram stain was also problematic, with results positive for both gram-negative and gram-positive, leaving researchers with gram-variable as the final answer.

     References

  • Forsum, U. The biology of Mobiluncus. Venereology, Vol. 14, No. 4, 2001: 169-73.
  • Costello, J., Blaize, J., L’Amoreaux, W., & McCoy, E. (2007). Ultrastructure of the Pathogenic Bacteria Mobiluncus mulieris. Microscopy and Microanalysis, 13(S02), 336-337.
  • De Boer JM, Plantema FH. Ultrastructure of the in situ adherence of Mobiluncus to vaginal epithelial cells. Can J Microbiol. 1988 Jun;34(6):757-66.
  • A. Menolascina, B. Nieves*, Z. Calderas, and C.L. Sanoja, Adherence and Cytotoxicity Capacity of Mobiluncus Strains Isolated from Patients with Bacterial Vaginosis, Anaerobe (1999) 5, 487±489 Article No. anae.1999.0295