Abstract
ObjectiveThis study aims to identify suitable lactobacilli that have anti-carbapenem-resistant Enterobacteriaceae (CRE) activity with in vitro tolerance to pepsin and bile salts.MethodsFifty-seven Lactobacillus 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.ResultsOf the 57 Lactobacillus 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 Lactobacillus strains did not change after heating but was abolished as the pH changed to 7.0. After a 24-h incubation, five of the Lactobacillus strains at a concentration of 108 CFU/ml totally inhibited the growth of carbapenem-resistant Escherichia coli (CRE316) and Klebsiella pneumoniae (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 108 CFU/ml, the decline in pH was faster than at other concentrations.ConclusionSome Lactobacillus strains exhibit anti-CRE activity, which suggests potential applications for controlling or preventing CRE colonization or infection.
Highlights
Enterobacteriaceae are normal flora of the human intestinal system, they are common pathogens causing human infections in the setting of both community-acquired and healthcare-associated infections (Hsueh et al, 2010; Toh et al, 2012; Lai et al, 2014; Jean et al, 2016)
After a 24-h incubation, five of the Lactobacillus strains at a concentration of 108 CFU/ml totally inhibited the growth of carbapenem-resistant Escherichia coli (CRE316) and Klebsiella pneumoniae (CRE632)
The resistance rates of these isolates against fusidic acid, kanamycin, trimethoprim/sulfamethoxazole, teicoplanin, and vancomycin ranged from 89.5 to 100% (Table 2). Environments, we selected these strains for the assessment their antibacterial activity
Summary
Enterobacteriaceae are normal flora of the human intestinal system, they are common pathogens causing human infections in the setting of both community-acquired and healthcare-associated infections (Hsueh et al, 2010; Toh et al, 2012; Lai et al, 2014; Jean et al, 2016). Lactobacillus can produce lactic acid, acetic acid, formic acid and other acids to reduce intestinal pH, which may be the most important mechanism These bacteria can secrete certain antimicrobial molecules, such as ethanol, fatty acid, hydrogen peroxide and bacteriocins to exert the antimicrobial activity (Georgieva et al, 2015; Inglin et al, 2015). We conducted this study to identify suitable lactobacilli that have anti-CRE activity with in vitro tolerance to pepsin and bile salts
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