Bloodstream infection due to Herbaspirillum sp.: case series and review of literature.

Herbaspirillum species are Gram-negative bacteria belonging to the class Betaproteobacteria, order Burkholderiales. The phylogenetic and phenotypic similarities among these groups easily lead to species misidentification. Herbaspirillum bacteraemia is an uncommon clinical entity. The objective of this review is to collect information to contribute to the management of this infection. We describe our own case series and review the cases reported in the literature. Cancer appears as the major underlying disease. The main source of bacteraemia was respiratory. Phenotypic identification methods often misidentify this species. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and molecular methods identify at genus level, but species assignment is not reliable. Herbaspirillum spp. showed a highly susceptible antimicrobial profile. β-Lactams showed good activity with low MIC values, except ampicillin. All isolates were resistant to colistin, suggesting an intrinsic resistance mechanism. Herbaspirillum spp. is an uncommon pathogen. MALDI-TOF MS or molecular methods are necessary to achieve a reliable genus identification. These species are not multidrug resistant. Piperacillin/tazobactam or ceftazidime might be a good treatment for this microorganism.