Leptotrichia amnionii sp. nov., a novel bacterium isolated from the amniotic fluid of a woman after intrauterine fetal demise

Abstract

A novel bacterium was isolated and characterized from the amniotic fluid of a woman who experienced intrauterine fetal demise in the second trimester of pregnancy. The bacterium was a slow-growing, gram-negative anaerobic coccobacillus belonging to the genus LEPTOTRICHIA: Unlike Leptotrichia sanguinegens, the isolate did not grow in chopped-meat glucose broth or on sheep blood agar upon subculturing. The isolate was characterized by sequencing and analyzing its 16S rRNA gene. The 1,493-bp 16S ribosomal DNA sequence had only 96% homology with L. sanguinegens. Several phylogenetic analyses indicated that L. amnionii is a distinct species and most closely related to L. sanguiegens.

FIG. 1.

Gram stain of amniotic fluid colonies demonstrating gram-negative pleomorphic bacilli.

FIG. 2.

Evolutionary distance dendrogram of selected leptotrichial and fusobacterial 16S rRNA sequences, including that of the Leptotrichia-like sp. isolate. Two archaeal species, Methanococcus jannaschii (M59126) and Sulfolobus acidocaldarius (D14876), were chosen as out-groups for phylogenetic analysis. Sequences are identified by species name and GenBank accession number. Branch points supported by >90% bootstrap values are indicated by solid circles. Open circles represent branch points with bootstrap values in the range 75 to 89%. Branch points without circles were not resolved (bootstrap values in the range <75%) as specific groups by this analysis. The bar at the bottom indicates the number of nucleotide changes per site.