Bifidobacterium Bacteremia: Clinical Characteristics and a Genomic Approach To Assess Pathogenicity

Abstract

Bifidobacteria are commensals that colonize the orogastrointestinal tract and rarely cause invasive human infections. However, an increasing number of bifidobacterial blood culture isolates has lately been observed in Norway. In order to investigate the pathogenicity of the Bifidobacterium species responsible for bacteremia, we studied Bifidobacterium isolates from 15 patients for whom cultures of blood obtained from 2013 to 2015 were positive. We collected clinical data and analyzed phenotypic and genotypic antibiotic susceptibility. All isolates (11 Bifidobacterium longum, 2 B. breve, and 2 B. animalis isolates) were subjected to whole-genome sequencing. The 15 patients were predominantly in the extreme lower or upper age spectrum, many were severely immunocompromised, and 11 of 15 had gastrointestinal tract-related conditions. In two elderly patients, the Bifidobacterium bacteremia caused a sepsis-like picture, interpreted as the cause of death. Most bifidobacterial isolates had low MICs (Յ0.5 mg/liter) to beta-lactam antibiotics, vancomycin, and clindamycin and relatively high MICs to ciprofloxacin and metronidazole. We performed a pangenomic comparison of invasive and noninvasive B. longum isolates based on 65 sequences available from GenBank and the sequences of 11 blood culture isolates from this study. Functional annotation identified unique genes among both invasive and noninvasive isolates of Bifidobacterium. Phylogenetic clusters of invasive isolates were identified for a subset of the B. longum subsp. longum isolates. However, there was no difference in the number of putative virulence genes between invasive and noninvasive isolates. In conclusion, Bifidobacterium has an invasive potential in the immunocompromised host and may cause a sepsis-like picture. Using comparative genomics, we could not delineate specific pathogenicity traits characterizing invasive isolates.KEYWORDS DNA sequencing, antibiotic resistance, bifidobacteria, blood culture, bloodstream infections, mass spectrometry, pangenome, probiotics, susceptibility testing, virulence factors B ifidobacteria are anaerobic, nonsporulating Gram-positive rods representing ubiquitous inhabitants of the human orogastrointestinal tract and vagina. The genus consists of more than 50 species, with only 10 species being found in humans. In breast-fed infants, bifidobacteria constitute more than 80% of the intestinal microbiota, whereas bifidobacteria comprise only 3 to 6% of the adult fecal flora (1, 2). Moreover, the species distribution is different in infants and adults; Bifidobacterium adolescentis and Bifidobacterium longum subsp. longum are the major bifidobacterial species in the

Evolutionary relationships among bifidobacteria and their hosts and environments

“…Bifidobacteria are ubiquitous inhabitants of the gastrointestinal tract, vagina, and mouth of mammals, including humans and are also present in guts of insects such as bees [16,17]. They have also been found in human blood, breast milk, and sewage [18][19][20]. The genomic signatures of bifidobacteria strains in different environments can give insights into how this bacterial group adapts to their environment and what types of traits are important for these adaptations.…”

A Comparative Study of the Gut Microbiota Associated with Immunoglobulin A Nephropathy and Membranous Nephropathy

“…Out of more than 50 species assigned to Bifidobacterium, only 10 are found in humans. However, a previous study demonstrated the invasive potential of Bifidobacterium in immune compromised host 38 .…”

Segurança e Benefício do Uso de Probióticos em Pacientes Submetidos ao TCTH: Revisão Integrativa

“…Ainda são controversos os resultados encontrados na literatura quanto ao uso de probióticos em pacientes imunocomprometidos. Um estudo realizado por Esaiassen et al 15 constatou bacteremia em pacientes pediátricos imunocomprometidos que utilizaram cepas de Bifidobacterium. Um estudo realizado por Wolf et al 16 com pacientes HIV positivos e imunocomprometidos mostrou que o uso de Lactobacillus reuteri foi seguro e bem tolerado pelos pacientes, não havendo nenhuma intercorrência durante o uso do probiótico, porém não houve diferença significativa na diminuição do número de evacuações diarreicas nesses pacientes.…”