Brucellosis Initially Misidentified as Ochrobactrum anthropi Bacteremia: A Case Report and Review of the Literature

Abstract

Automated identification systems may misidentify Brucella, the causative agent of brucellosis, which may be re-emerging in the United States as the result of an expanding feral swine population. We present a case of Brucella suis likely associated with feral swine exposure that was misidentified as Ochrobactrum anthropi, a phylogenetic relative.

Ochrobactrum anthropi – An Emerging Opportunistic Pathogen in Musculoskeletal Disorders – A Case Report and Review of Literature

“…3 ) [ 10 ]. API 20NE automated system misidentify O. anthropi as Brucella species because of its close relation [ 8 , 14 ]. Hence, a confirmation is required with negative serum Brucella species antibodies in a patient with severe infections caused by O. anthropi bacteremia without any proper primary focus of infection and refractory to standard treatment [ 3 ].…”

“…Colonies are small about 1mm in diameter and appear circular, low convex, smooth, shining, and entire resembling Enterobacteriaceae. Isolates of O. anthropi show mucoid appearance on MacConkey agar and are non-lactose fermenters whereas the Brucella group of organisms shows no growth in MacConkey agar [ 6 , 8 ].…”

“…A few reports have been published in the literature stating the misidentification of Brucella group of organisms due to low homology with O. anthropi [ 8 , 14 , 37 , 38 ]. Gopalsamy et al reported misidentification of O. anthropi in Brucellosis infection as both the organisms are close phylogenetic relatives which result in cross-reactivity on Western blot and 16s ribosomal RNA sequence signatures [ 8 ]. Due to the overlap between two groups of organisms, the diagnosis becomes a great challenge.…”

“…Being an opportunistic bacterium, it is noted for bacteremia, localized infections, and catheter or stent-associated infections in both immunocompetent and immunocompromised individuals [ 3 , 4 , 5 ]. Reports have been made on its diagnostic challenges and difficulty in identifying the optimal therapeutic algorithm [ 6 , 7 , 8 , 9 ]. Till date, there are no standard guidelines to diagnose and treat O. anthropi related infections [ 10 , 11 , 12 ].…”

The Retrospective on Atypical Brucella Species Leads to Novel Definitions

“…In general, the widely used commercial systems for the biochemical testing of bacteria, namely API 20NE, RapID NF Plus, and VITEK 2, have revealed pitfalls in discriminating classical and in particular atypical Brucella isolates from primarily environmental (former) Ochrobactrum spp. [23,86]. However, comprehensive phenotypic characterization shows striking intra-and inter-species variability in the substrate utilization patterns of Brucella [19,72,87].…”