Brucella suis bacteremia misidentified as Ochrobactrum anthropi by the VITEK 2 system

Abstract

Ochrobactrum and Brucella are genetically related genera of the family Brucellaceae, sharing 98.8% rRNA similarity. Because of their phenotypic similarity, Ochrobactrum can be miscoded as Brucella by automated identification systems. The misidentification on blood cultures (BCs) of B. suis as O. anthropi by the VITEK 2 system is herein described. A 67-year-old male with a prosthetic mitral valve and fever was admitted with bacteremia due to a Gram-negative coccobacillus identified as O. anthropi by VITEK 2. The patient's fever persisted along with positive blood cultures despite specific antimicrobial treatment. Due to this adverse outcome, the patient was interrogated again and admitted having domestic swine. Serological tests were positive for acute brucellosis. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) of BC strains identified B. suis biovar 1. Timely identification of Brucella is essential for providing proper treatment to the patient and for advising safe handling of laboratory cultures in biological safety cabinets to prevent laboratory-acquired infection. Countries where brucellosis is endemic must be aware of this possibility.

A MALDI-TOF MS database with broad genus coverage for species-level identification of Brucella

“…The updated database allowed correct identification of Brucella isolates at the genus level in 88.4% of cases. It is important to mention that none of them was identified as Ochrobactrum spp ., a misidentification that is common with other standard identification methods [ 32 – 34 ] and recently reported using the VITEK MS database currently available [ 35 ]. Analysis at the species level gave only one discordant result, corresponding to cross identification between two Brucella species.…”

Brucella vertebral osteomyelitis misidentified as an Ochrobactrum anthropi infection

“…Regarding the initial antimicrobial therapy, ciprofloxacin is active against Brucella and can be used as an alternative in combination with other agents, mainly in non-localizing infections, but it shouldn’t be used as a single agent due to its low efficacy and unacceptable high relapse rates [ [17] , [21] , [22] ]. Several cases of misidentification with Brucella and Ochrobactrum have been reported [ [5] , [6] , [7] , [8] , [9] , [10] ]. These cases have led some laboratories to implement a safety measure with an automatic alert message whenever similar species to Brucella are identified, so that the laboratory staff may take the necessary safety precautions.…”

“…In some of this cases, the samples were later evaluated and correctly identified using Vitek ® 2 system [ [5] , [8] ]. More recently there was a case report with Vitek ® 2 system misidentifying Brucella suis as an O. anthropi [ 6 ]. To our knowledge, this is the first reported case of a misidentification of a Brucella species with O. anthropi, using a system based on MALDI-TOF technology (Vitek ® MS).…”

“…Contrarily to Brucella , Ochrobactrum spp rarely causes disease in humans; within the various species, O. anthropi seems to be the most clinically relevant. Due to being phenotypically and genetically closely related [ 4 ] several cases of misidentification have been reported [ [5] , [6] , [7] , [8] , [9] , [10] ]. Ochrobactrum is considered an opportunistic and nosocomial pathogen and mostly associated with central venous catheters infections, especially in dialysis patients [ [11] , [12] ] that lead to bacteremia and may cause localized infections such as endocarditis and osteomyelitis mainly in critically ill or immunocompromised patients [ [13] , [14] ].…”

Ochrobactrum anthropi: An emerging pathogen causing meningitis with sepsis in a neurotrauma patient

“…Furthermore, in the areas where the prevalence of Brucella is low, confusion with this organism is frequent. Similar phenotypic properties of both organisms attributes to diagnostic dilemma and misidentification by automated identification systems in the clinical laboratory [9]. Therefore, vigilant screening, rapid diagnosis and prompt institution of appropriate therapy along with implementation of effective hospital infection control practices are essential prerequisites for successful management of this pathogen.…”