Antibiotic resistance versus biofilm production in Gardnerella vaginalis
Valerie Masete1, Sylvain Godreuil2, Hélène Jean-Pierre2, Jo-Ann S. Passmore 1,3, Rémy Froissart4,*
1Institute of Infectious Disease and Molecular Medicine, University of Cape Town, South Africa; 2Centre Hospitalier Régional Universitaire de Montpellier, Hôpital Arnaud de Villeneuve, Département de Bactériologie-Virologie, Montpellier, France; 3National Health Laboratory Service, Cape Town, South Africa; 4UMR 5290 MIVEGEC, CNRS IRD Université Montpellier, France
Bacterial vaginosis (BV) is a common vaginal condition affecting reproductive-age women, especially in sub-Saharan Africa. Although BV is treatable with antibiotics, 50% of the women get recurrent BV within six months after treatment. While the etiology of BV is not well characterized, it is understood that Gardnerella vaginalis plays a critical role in BV by initiating the formation of the biofilm and by degrading vaginal mucus through the release of sialidase.
The aim of this study was thus to characterize the genotypic and phenotypic diversity (biofilm formation, susceptibility to four antibiotics using E-test method, and sialidase activity) of a large panel of vaginal G. vaginalis isolates. Using 109 G. vaginalis isolates, purified from vaginal samples of French women who were diagnosticated (through microscope observation of each fresh sample) BV-positive (75/109), BV-intermediate (20/109) or BV-negative (14/109). Of these, 90 isolates were successfully genotyped using their chaperonin-60 sequences, revealing the presence of four phylogenetic clades: 13/90 subgroup A, 17/90 subgroup B, 58/90 subgroup C and 2/90 subgroup D isolates. Sialidase activity was not detected in any of the subgroup A and D isolates but was detected at similar levels in subgroup B and C isolates. Isolates from all subgroups formed similar amounts of biofilm. Forty-five of the isolates were screened for antibiotic sensitivity: the majority (71%) were resistant to metronidazole, but sensitive to clindamycin (100%), moxifloxacin (91%) and augmentin (100%). In conclusion, G. vaginalis subgroup B and C isolates were the only ones that formed biofilms and had detectable sialidase activity, suggesting that G. vaginalis subgroups B and C are most likely to be involved in BV. These results contribute to our knowledge of BV and could be useful in future studies that aim to design better treatment strategies for BV.