Clinical characteristics of bacteraemia caused by Lactobacillus spp. and antimicrobial susceptibilities of the isolates at a medical centre in Taiwan, 2000–2014

Abstract

The clinical characteristics of 89 patients with Lactobacillus bacteraemia treated at a university-affiliated hospital in northern Taiwan during 2000–2014 were retrospectively evaluated. Lactobacillus spp. were identified by 16S rRNA sequencing analysis and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Antimicrobial susceptibilities of the isolates were determined by broth microdilution. The most commonly isolated species was Lactobacillus salivarius (n=21), followed by Lactobacillus paracasei (n=16) and Lactobacillus fermentum (n=13). Excluding three isolates with lower 16S rRNA sequence similarity, MALDI-TOF/MS provided correct identification for 84.9% (73/86) of Lactobacillus isolates. Concordant identification was lowest for Lactobacillus casei (11%). The main infection foci were intra-abdominal infection (49%) and catheter-related bloodstream infection (17%). Only one-half of the patients received adequate antibiotic treatment during the bacteraemic episode. The majority of patients with Lactobacillus bacteraemia were immunocompromised. The 7-day and in-hospital mortality rates were 21% and 62%, respectively, and underlying malignancy was associated with a higher in-hospital mortality rate (odds ratio=2.666). There were no significant differences in mortality (7-day, 14-day, 30-day and in-hospital) among patients with bacteraemia due to different Lactobacillus spp. Minimum inhibitory concentrations were highest for glycopeptides, cephalosporins and fluoroquinolones and were lowest for carbapenems and aminopenicillins. Lactobacillus bacteraemia was associated with a high mortality rate, and patient outcome was associated with underlying malignancy. MALDI-TOF/MS was able to accurately identify 84.9% of the Lactobacillus isolates, and L. salivarius was the predominant pathogen. The accuracy rate for identification of Lactobacillus spp. by MALDI-TOF/MS was lowest for L. casei.