Antimicrobial Susceptibilities and Clinical Sources ofDialisterSpecies

Abstract

Seventy-four strains representing the four species of the genus Dialister were isolated from various clinical samples. Dialister pneumosintes and Dialister micraerophilus were the two mainly encountered species. Fifty-five isolates were tested against 14 antimicrobial agents. Decreased susceptibilities to piperacillin, metronidazole, macrolides, fluoroquinolones, and rifampin were demonstrated. The clinical impact of these decreased susceptibilities remains to be investigated but should prompt microbiologists to perform antimicrobial susceptibility testing for clinically important Dialister spp.Four species are currently described in the genus Dialister: Dialister pneumosintes, Dialister invisus, Dialister micraerophilus, and Dialister propionicifaciens, the last three being described since 2003 (5, 11). They are small, anaerobic or microaerophilic gram-negative coccobacilli that grow as small, circular, tiny, and transparent colonies on Columbia blood agar, making their recovery in mixed anaerobic cultures relatively difficult. Besides, strains may be difficult to distinguish from tiny, gram-negative anaerobic cocci. Usually, Dialister spp. could be distinguished from members of the genus Veillonella by both the absence of nitrate reduction and the pattern of susceptibility to special-potency disks. Indeed, they display susceptibility to kanamycin (500 g), bile (1 mg), and metronidazole (50 g) and resistance to vancomycin (5 g) and colistin (10 g) disks, whereas Veillonella species are susceptible to the colistin disk, except for Veillonella montpellierensis and Veillonella ratti (10, 11). However, due to their biochemical characteristics (i.e., asaccharolytic and nonreactive in conventional biochemical tests), identification of members of the genus Dialister often requires molecular methods such as 16S rRNA gene sequencing (11). The involvement of Dialister spp. in human infections is now clearly established. D. pneu-

<i>Dialister pneumosintes</i> Bacteremia Caused by Dental Caries and Sinusitis

“…Morio et al investigated 33 isolates of D. pneumosintes obtained at their hospital in France (21) and reported that there were no cases of resistance to any betalactam agents, fluoroquinolones or metronidazole, similar to the findings of previous cases (19) and the current case, with the exception of susceptibility to penicillin. In the present case, we initially administered cefepime and subsequently added levofloxacin.…”

Alteration of Fecal Microbiota Profiles in Juvenile Idiopathic Arthritis. Associations with HLA-B27 Allele and Disease Status

“…In HLA-B27 negative-ERA patients, we found Haemophilus and Eggerthella , recently associated with rheumatoid arthritis (Zhang et al, 2015; Chen et al, 2016). Moreover, when considering only the ERA group, in HLA-B27 positive patients we also showed enrichment of Lactobacillus , observed as potential arthritogenic agent via its cell wall pepetidoglycan (Severijnen et al, 1989), Clostridium cluster XI , that includes C. difficile , a well-known proinflammatory and colitis inducing-bacterium, and Dialister , frequently found in periodontitis and other infections (Morio et al, 2007). …”

The Complex Vaginal Flora of West African Women with Bacterial Vaginosis

“…Whether relapses may be due to re-infections accompanying intercourse remains controversial [29], [30]. Systematically administered metronidazole has little or no activity against M. hominis , Bifidobacterium , and G. vaginalis and only moderate activity against Dialister [31], [32]. Metronidazole has predictable activity against Prevotella , Leptotrichia , and Eggerthella [33], [34].…”