Objective To assess the rates of co-infections between human papillomavirus (HPV) and 13 key markers of bacterial vaginosis in cervical samples by multiplex polymerase chain reaction in a population with a high rate of abnormal cytology and a positive HPV test.

Methods The study included a total of 213 women aged 18–72 years screened using Papanicolaou smears for determining cervical abnormalities and for HPV and bacterial vaginosis by single-target and multiplex polymerase chain reaction.

Results A total of 83 (39%) women were negative for intraepithelial lesion or malignancy cytology and 130 (61%) had abnormal cytology. HPV-DNA prevalence was 69.9% and bacterial vaginosis was 72.7 %. Co-infections between bacterial vaginosis with HPV-DNA and high-risk HPV were associated with an increased risk for squamous intraepithelial lesions of low-grade cytology and high-grade squamous intraepithelial lesions plus cervical cancer. The most frequent bacterial vaginosis agent was Gardnerella vaginalis (33.8%), and co-infection with HPV-DNA and high-risk HPV increased the risk for squamous intraepithelial lesions of low grade cytology and high-grade squamous intraepithelial lesions plus cervical cancer. Co-infection between Megasphaera type I and high-risk HPV increased the risk for high-grade squamous intraepithelial lesions plus cervical cancer.

Conclusions Our results reinforce the hypothesis that some bacterial vaginosis agents may play a role as co-factors in HPV-mediated cervical carcinogenesis, at least in some populations.