Mistaken Identity of Brucella Infection

Abstract

We read with interest the paper "Ribosomal RNA Sequence Analysis of Brucella Infection Misidentified as Ochrobactrum anthropi Infection" by Horvat and colleagues (1). The paper reported that a Brucella isolate was misidentified as Ochrobactrum anthropi. The 16S rRNA results indicated that the isolates were Brucella species, with 100% agreement to rRNA sequences of known brucellae and low homology to Ochrobactrum anthropi sequences.Our laboratory has encountered such circumstances three times since December 2011. Strains were isolated from blood cultures of two patients suffering from fever without apparent cause and from a bone marrow culture of a patient with a left tibial lesion. They were initially identified as Bordetella bronchiseptica (1 case) and Ochrobactrum anthropi (2 cases) through the Vitek 2 Compact microbial identification system and Gram-negative (GN) identification card. As the first case (misidentified as Bordetella bronchiseptica) had brucellosis symptoms of splenomegaly, mildly elevated transaminase, typical undulant fever, and a significantly elevated lymphocyte level in his white blood cell count, 16S rRNA PCR amplification and sequencing were performed and results were analyzed using GenBank (accession numbers ACBJ01000075.1, ACEM01000005.1, NC_013118.1, and NC_009668.1). The results indicated that the highest level of identity was to Brucella abortus, Brucella melitensis, and Brucella microti among the Brucella spp., as well as Ochrobactrum anthropi ATCC 49188 (query coverage, 100%; maximum identity, 99%). However, Ochrobactrum anthropi could be excluded based on a negative result observed in the semisolid-medium motility test and flagellar staining. The results suggest that the automated microbial identification system is unreliable, so two preserved strains identified as Ochrobactrum anthropi by the Vitek test were subcultured and reevaluated. 16S rRNA PCR amplification, sequencing, and alignment were performed. The results were similar to those for the first strain; i.e., highest identity was to several isolates within the Brucella spp. and Ochrobactrum anthropi. Here again, Ochrobactrum anthropi was excluded based on a negative result from the semisolid-medium motility test and flagellar staining. We also performed the test which utilized real-time PCR followed by high-resolution melting (HRM) curve analysis to identify the Brucella strains. They were identified as Brucella melitensis. All three strains were confirmed as Brucella melitensis by the China CDC, and the patients' sera were positive for Brucella antibody using the Brucella microagglutination test. These three stains were serotyped as biovar type I.Brucella is a potential agent of bioterrorism and also a significant pathogen causing laboratory-acquired infections (2, 3). However, misidentification of Brucella species by some commercial bacterial identification systems has been previously reported (4, 5). Because of these recurring misidentifications, more and more laboratories are now relying on molecular methods to identify...

The medical diagnostic approaches with phylogenetic analysis for rare Brucella spp. diagnosis in Taiwan

“…and O. intermedium were found to be 98.6% identical [ 29 ]. Like the previous research group report [ 14 ], our study also had a similar misclassification experience with Brucella spp. in our automatic identification and 16s nucleotides blast.…”

“…Laboratories had been report some cases of Brucella initially misdiagnosed by automatic identification systems before. These errors can lead to misdiagnosis, delayed treatment, and ultimately, the infection of even more individuals [ 11 - 14 ].…”

Laboratory Diagnosis of Human Brucellosis

“…The main drawbacks of the phenotypic identification of brucellae are the long turnaround time and the exposure of laboratory technicians to a highly transmissible bacterium. In addition, commercial systems may misidentify brucellae as the closely related Ochrobactrum anthropi (103,104) or Ochrobactrum intermedium species (105), as well as the unrelated Haemophilus influenzae (106), Bergeyella zoohelcum (107), Bordetella bronchiseptica (108), or Psychrobacter phenylpyruvicus (formerly Moraxella phenylpyruvica) (109), a serious mistake that has already caused outbreaks of laboratory-acquired disease (110). The presumptive identification of brucellae should be confirmed by a molecular method (see Diagnosis of Brucellosis by Nucleic Acid Amplification Tests below) or by a positive slide agglutination reaction with specific antiserum against the bacterial O-lipopolysaccharide (O-LPS).…”

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

“…and O. anthropi may cause similar febrile diseases with non-specific clinical presentation [8,[12][13][14]. Caution must be exerted when using biochemical test systems such as API 20NE [11] and automated systems such as RapID NF Plus system [1] and VITEK 2 for bacterial identification, because misidentification of these genera has been reported [5,15].…”