Programme Hospitalier Recherche Clinique, Institut Pasteur, Inserm, French Public Health Agency.

BackgroundMultilocus sequence typing (MLST) is currently the reference method for genotyping Streptococcus agalactiae strains, the leading cause of infectious disease in newborns and a major cause of disease in immunocompromised children and adults. We describe here a genotyping method based on multiple locus variable number of tandem repeat (VNTR) analysis (MLVA) applied to a population of S. agalactiae strains of various origins characterized by MLST and serotyping.ResultsWe studied a collection of 186 strains isolated from humans and cattle and three reference strains (A909, NEM316 and 2603 V/R). Among 34 VNTRs, 6 polymorphic VNTRs loci were selected for use in genotyping of the bacterial population. The MLVA profile consists of a series of allele numbers, corresponding to the number of repeats at each VNTR locus. 98 MLVA genotypes were obtained compared to 51 sequences types generated by MLST. The MLVA scheme generated clusters which corresponded well to the main clonal complexes obtained by MLST. However it provided a higher discriminatory power. The diversity index obtained with MLVA was 0.960 compared to 0.881 with MLST for this population of strains.ConclusionsThe MLVA scheme proposed here is a rapid, cheap and easy genotyping method generating results suitable for exchange and comparison between different laboratories and for the epidemiologic surveillance of S. agalactiae and analyses of outbreaks.

These findings have important implications for the interpretation of trends in maternal mortality in the context of HIV. The apparent survival benefit of pregnant HIV-positive women is largely due to their low fertility in the latest stage of the disease. As the HIV epidemic matures and more women become severely ill, any potential adverse effects associated with HIV and pregnancy may be increasingly offset by selection effects, and maternal mortality may not increase further.

No abstract