Neisseria bacilliformis sp. nov. isolated from human infections

Abstract

Most Neisseria species are gram-negative cocci or diplococci; currently, N. elongata is the only species of human origin with a bacillary morphology. Here, we report isolation and characterization of eight strains of another bacillary Neisseria species from human infections. The organisms caused or contributed to either oral cavity-related or respiratory tract infections, and two strains were isolated from blood cultures. The 16S rRNA gene sequences of these organisms, being homogenous or nearly so (99.4 to 100% identity), matched at <96% known Neisseria species and formed a distinct group within the genus. Analysis of the cellular fatty acids showed broad similarity with a few Neisseria species. The organisms were gram negative and measured 0.6 mum by 1.3 to 3.0 mum. They grew well on chocolate agar and on sheep blood agar but did not grow on modified Thayer-Martin agar. They were positive for oxidase and negative for indole production. There was no acid production from dextrose, lactose, maltose, or sucrose. The tests for catalase reaction, nitrate reduction, and tributilin varied with the strains. These results suggest that these organisms represent a novel species within the genus Neisseria, for which the name Neisseria bacilliformis sp. nov. is proposed. The type strain is MDA2833 = ATCC BAA-1200(T) = CCUG50858(T). Distinction between N. bacilliformis and N. elongata can be made confidently by 16S rRNA gene sequencing or cellular fatty acid profiling but may be difficult by morphology or routine biochemical tests.

FIG. 1.

Phylogenetic tree of MDA2833 and its variants in relation to representative Neisseria species. Strain designations and GenBank accession numbers are as follows: N. canis ATCC 14687^T, L06170; N. cinerea LNP1646, AJ239287; N. flavescens ATCC 13120^T, L06168; N. elongata subsp. elongata ATCC 25295^T, L06171; N. meningitidis M7825, AF382301; N. pharyngis NCTC4590, AJ239281; and N. weaveri ATCC 51223^T, L10738.

FIG. 2.

Gram staining (magnification, ×1,000) (top) and electron microscopy (bar, 1 μm) (bottom) of MDA2833, a bacillary Neisseria sp.