Mycobacterial L-forms are found in cord blood: A potential vertical transmission of BCG from vaccinated mothers

Hum Vaccin Immunother. 2016 Oct 2;12(10):2565-2571. doi: 10.1080/21645515.2016.1193658. Epub 2016 Jun 13.


Our previous studies showed that mycobacterial L-forms persist in the blood of BCG vaccinated people and that BCG vaccine is able to produce, under appropriate conditions, filterable, self-replicating L-bodies with virus-like size. Because filterability is one of the characteristics of L-forms, considerable interest has been shown in their capacity to cross the maternal-fetal barrier. The current study demonstrated isolation of mycobacterial L-form cultures from umbilical cord blood of 5 healthy newborns of healthy mothers vaccinated previously with BCG. The isolated cultures showed distinctive growth characteristics of cell wall deficient L-form bacteria. Transmission electron microscopy demonstrated presence of L-bodies with extremely small size of 100 nm and revealed morphological transformations, typical for L-forms. IS6110 Real Time PCR assay confirmed that all L-form isolates were of mycobacterial origin and belonged to Mycobacterium tuberculosis complex which includes vaccinal BCG substrains. In conclusion, we could suggest that reproductive filterable L-bodies of BCG origin are able to fall in blood circulation of the fetus by vertical transmitted pathway and colonize newborns.

Keywords: BCG; L-forms; cord blood; mycobacteria; newborns.

MeSH terms

  • BCG Vaccine / administration & dosage*
  • Female
  • Fetal Blood / microbiology*
  • Healthy Volunteers
  • Humans
  • Infant, Newborn
  • L Forms / genetics
  • L Forms / isolation & purification*
  • L Forms / ultrastructure
  • Microscopy, Electron, Transmission
  • Mycobacterium bovis / genetics
  • Mycobacterium bovis / isolation & purification*
  • Mycobacterium bovis / ultrastructure
  • Real-Time Polymerase Chain Reaction


  • BCG Vaccine