The present report describes the misidentification of Brucella spp. from a positive blood culture using traditional microbiology tests. A molecular test identified the bacterium as Ochrobactrum anthropi. According to the information available, this report is the first to include this type of case in Mexico.

Administration of empirical antibiotic therapy prior to microbiological diagnosis is thought to be associated the failure of subsequent bacterial growth in culture. The aim of this study was to detect bacterial pathogens via direct amplification and sequencing of the 16S rDNA gene in samples showing negative culture results as alternative diagnostic tools to troubleshoot difficult samples. Twenty-three (7.66 %) positive samples were detected, most of which were monomicrobial infections; 15 of the cases were identified as HAIs, 6 had catheter colonisation, and 2 had sample colonisation. The pathogens identified included Escherichia, Salmonella, Pseudomonas spp., Enterococcus spp. and coagulase-negative staphylococci (CoNS). The most frequent infections were bacteraemia and urinary tract infection, but meningitis, warm infection and soft tissue infection were also documented. These findings emphasise the efficacy and usefulness of molecular diagnosis, thus 16S rDNA gene analysis is strongly indicated by HAIs diagnostics.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-016-1949-3) contains supplementary material, which is available to authorized users.