Anaerobic, non-sporulating, Gram-positive bacilli bacteraemia characterized by 16S rRNA gene sequencing

Abstract

Owing to the difficulties in identifying anaerobic, non-sporulating, Gram-positive bacilli in clinical microbiology laboratories, the epidemiology and clinical spectrum of disease of many of these bacteria have been poorly understood. The application of 16S rRNA gene sequencing in characterizing bacteraemia due to anaerobic, non-sporulating Gram-positive bacilli during a 4-year period is described. The first case of Olsenella uli bacteraemia, in a patient with acute cholangitis, is also reported. Among 165 blood culture isolates of anaerobic, Gram-positive bacilli, 75 were identified as Propionibacterium acnes by phenotypic tests and 21 as members of other anaerobic, non-sporulating Gram-positive bacilli by 16S rRNA gene sequencing. Of these 96 isolates, 16 (17 %) were associated with cases of clinically significant bacteraemia, among which 10 (63 %) were caused by Eggerthella, four (25 %) by Lactobacillus and one (6 %) by each of Eubacterium tenue and O. uli. Five of the 10 Eggerthella isolates were Eggerthella lenta, whereas the other five belonged to two novel Eggerthella species, with Eggerthella hongkongensis being almost as prevalent as Eggerthella lenta. Underlying disease in the gastrointestinal tract, isolation of Eggerthella and Lactobacillus, and monomicrobial bacteraemia were associated with clinically significant bacteraemia, whereas isolation of P. acnes and polymicrobial bacteraemia were associated with pseudobacteraemia. Most patients with clinically significant bacteraemia had underlying diseases, with diseases in the gastrointestinal tract being most common. The overall mortality rate was 31 %. Immunocompromised patients with clinically significant bacteraemia due to anaerobic, non-sporulating, Gram-positive bacilli other than P. acnes should be treated with appropriate antibiotics. The unexpected frequency of isolation of Eggerthella from blood cultures and its association with clinically significant disease suggest that this genus is probably of high pathogenicity. Further studies to look for specific virulence factors are warranted.

Dynamics and diversity of the ‘Atopobium cluster' in the human faecal microbiota, and phenotypic characterization of ‘Atopobium cluster' isolates

“…We detected the species, respectively, in the DGGE profiles of donors 6 and 5. Upon identifying O. uli-associated bacteraemia in a patient with acute cholangitis but no evidence of dental disease, Lau et al (2004b) suggested that the bacterium responsible for the infection was of GI origin. There are currently only two reports of the isolation of G. pamelaeae in the literature: one strain was isolated from the sigmoid region of the colon of a 33-year-old male patient suffering from acute Crohn's disease (Würdemann et al, 2009); the other was isolated in pure culture from an 82-year-old patient with disseminated rectosigmoid carcinoma with fresh blood and mucus in his stool (Woo et al, 2010).…”

Eggerthella lentaBacteremia after Endoscopic Retrograde Cholangiopancreatography in an End-Stage Renal Disease Patient

“…Also a group in Hong Kong also reported that 18% of clinically significant bacteremia caused by anaerobic, gram-positive bacilli were related to E. lenta [2]. Furthermore, E. lenta bacteremia is primarily community acquired [2,3].…”

“…A few studies reported the susceptibilities of E. lenta [3,6,7,15]. In the article by Mosca et al, including 29 strains of E. lenta clinical isolated, all were susceptible to clindamycin, piperacillin and imipenem [15].…”

“…Especially in patients with predisposing factors, bacteremia is associated with high mortality [3,6,7,14].…”

“…Many of these bacteria are considered as contaminants in blood culture, but some Eggerthella species isolated from blood culture are clinically significant [3]. In particular, Eggerthella lenta is rarely isolated from blood but may occur as an opportunistic pathogen with high morbidity and mortality.…”