Novel Brucella strain (BO1) associated with a prosthetic breast implant infection

Abstract

We report the microbiological, biochemical, and molecular characterization of an unusual Brucella strain (BO1) isolated from a breast implant wound in a 71-year-old woman with clinical symptoms consistent with brucellosis. Initial phenotypic analysis, including biochemical and antimicrobial susceptibility testing, cellular fatty acid analysis, and molecular analysis based on DNA-DNA reassociation and the presence of multiple copies of IS711 element suggested that the isolate was a Brucella-like organism, but species determination using microbiological algorithms was unsuccessful. Furthermore, molecular data based on 16S rRNA gene sequencing and multilocus sequence analysis demonstrated that BO1 was an unusual Brucella strain and not closely related to any currently described Brucella species. However, comparison with equivalent sequences in Ochrobactrum spp. confirms that the isolate is much more closely related to Brucella than to Ochrobactrum spp., and thus the isolate likely represents an atypical and novel strain within the genus Brucella.

FIG. 1.

Colony morphology of BO1 strain after 48 h of growth on SBA incubated at 37°C in 5% CO₂.

FIG. 2.

Phylogenetic tree based on analysis of 16S rRNA gene sequence data indicating relationships between BO1 and other Brucella (represented by the B. ovis type strain) and Ochrobactrum species. MEGA 3.1 was used to generate the dendrogram using the neighbor-joining algorithm with Kimura two-parameter correction and a 1,000-step bootstrap. The bar indicates 0.01 substitutions per nucleotide position. The sequence from the Afipia felis type strain was used as an outgroup. GenBank accession numbers are in parentheses.

FIG. 3.

Detection of the IS711 element in BO1, B. ovis, and B. melitensis 16M by PCR. The amplicons were separated by electrophoresis using a 2% E-Gel agarose gel.

FIG. 4.

Unrooted phylogenetic reconstruction of the relationships between Brucella STs and BO1. The tree was constructed with concatenated sequence data representing nine distinct genetic loci (4,396 bp) using the neighbor-joining approach.

FIG. 5.

Relationships between Brucella, BO1, and Ochrobactrum sequences at eight distinct housekeeping genes. The trees were constructed by using the neighbor-joining method, and percent bootstrap confidence levels of internal branches were calculated from 1,000 resamplings of the original data.