AUTHOR=Chen Chi-Chung , Lai Chih-Cheng , Huang Hui-Ling , Huang Wen-Yu , Toh Han-Siong , Weng Tzu-Chieh , Chuang Yin-Ching , Lu Ying-Chen , Tang Hung-Jen 

TITLE=Antimicrobial Activity of Lactobacillus Species Against Carbapenem-Resistant Enterobacteriaceae

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.00789

DOI=10.3389/fmicb.2019.00789

ISSN=1664-302X

ABSTRACT=<sec><title>Objective</title><p>This study aims to identify suitable lactobacilli that have anti-carbapenem-resistant <italic>Enterobacteriaceae</italic> (CRE) activity with <italic>in vitro</italic> tolerance to pepsin and bile salts.</p></sec><sec><title>Methods</title><p>Fifty-seven <italic>Lactobacillus</italic> spp. strains encompassing nine species were collected for investigation. Their viabilities in the presence of pepsin and bile salts were tested using tolerance tests. Their anti-CRE effects were assessed by agar well diffusion and broth microdilution assay, as well as time-kill test.</p></sec><sec><title>Results</title><p>Of the 57 <italic>Lactobacillus</italic> isolates collected, 31 had a less than 2-log reduction in their viability in both pepsin and bile salt tolerance tests. Of these 31 isolates, 5 (LUC0180, LUC0219, LYC0289, LYC0413, and LYC1031) displayed the greatest anti-CRE activity with a CRE zone of inhibition greater than 15 mm in agar well diffusion assays. The minimal inhibitory percentages of supernatants from these five strains against CREs ranged from 10 to 30%. With the exception of LUC0180, which had a minimal bactericidal percentage ≥ 40%, the bactericidal percentage of all the strains ranged from 20 to 40%. The inhibitory effect of the cell-free culture supernatants from these <italic>Lactobacillus</italic> strains did not change after heating but was abolished as the pH changed to 7.0. After a 24-h incubation, five of the <italic>Lactobacillus</italic> strains at a concentration of 10<sup>8</sup> CFU/ml totally inhibited the growth of carbapenem-resistant <italic>Escherichia coli</italic> (CRE316) and <italic>Klebsiella pneumoniae</italic> (CRE632). After a 48-h incubation, the growth of CRE316 was completely inhibited under each concentration of lactobacilli based on time-kill test. Furthermore, when the concentration of lactobacilli was at 10<sup>8</sup> CFU/ml, the decline in pH was faster than at other concentrations.</p></sec><sec><title>Conclusion</title><p>Some <italic>Lactobacillus</italic> strains exhibit anti-CRE activity, which suggests potential applications for controlling or preventing CRE colonization or infection.</p></sec>