Relevance of anaerobic bacteremia in adult patients: A never-ending story?

Márió Gajdács,Edit Urbán

doi:10.1556/1886.2020.00009

Abstract

Obligate anaerobic bacteria are considered important constituents of the microbiota of humans; in addition, they are also important etiological agents in some focal or invasive infections and bacteremia with a high level of mortality. Conflicting data have accumulated over the last decades regarding the extent in which these pathogens play an intrinsic role in bloodstream infections. Clinical characteristics of anaerobic bloodstream infections do not differ from bacteremia caused by other pathogens, but due to their longer generation time and rigorous growth requirements, it usually takes longer to establish the etiological diagnosis. The introduction of matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) has represented a technological revolution in microbiological diagnostics, which has allowed for the fast, accurate and reliable identification of anaerobic bacteria at a low sample cost. The purpose of this review article is to summarize the currently available literature data on the prevalence of anaerobic bacteremia in adults for physicians and clinical microbiologists and to shed some light on the complexity of this topic nowadays.

Highlights

Under physiological conditions, obligate anaerobic bacteria are considered important constituents of the microbiota of humans; on mucosal surfaces and in some anatomical regions their numbers exceed the number of facultative anaerobes by a magnitude of 10–1,000 [1, 2]
The relevance of anaerobic bacteria as pathogens has been described from basically all anatomical areas, these infections may be divided into two main groups: exogenous or “classical” infections are predominantly monomicrobial, toxin-mediated diseases, where the principal causative agents are spore-forming Grampositive rods, while so-called endogenous or “modern” infections are mainly polymicrobial infections, where the components of the normal bacterial microbiota are seen as pathogens [1, 2, 5, 6]
As presented above, conflicting data have accumulated in the literature regarding the incidence of anaerobic bacteremia and on the relevance of the routine use of anaerobic blood cultures

Summary

Introduction

Obligate anaerobic bacteria are considered important constituents of the microbiota of humans; on mucosal surfaces and in some anatomical regions (oral cavity, female genital tract, colon) their numbers exceed the number of facultative anaerobes by a magnitude of 10–1,000 [1, 2]. These strict anaerobes have a protective role against obligate pathogenic bacteria by consuming nutrients in the anatomical niche and by secreting short-chain fatty acids (SCFAs); this phenomenon is called colonization resistance [3]. Based on the source of the infection, Bacteroides/Parabacteroides spp. and Clostridium spp. mainly originate from the gastrointestinal tract, GPAC, pigmented Prevotella spp., Porphyromonas spp., and Fusobacterium spp. arise from the upper airways, from pulmonary sources or the female genital tract, while Cutibacterium acnes mainly originated from the skin and foreign bodies [1, 2, 12]

Objectives

Findings

Conclusion