Recovery of Lactobacillus casei strain Shirota (LcS) from faeces of healthy Singapore adults after intake of fermented milk.

To validate survival of Lactobacillus casei strain Shirota (LcS) during passage through the gastrointestinal tract of healthy Singaporean young adults, 21 participants (18-25 years old) were asked to consume a 100 ml of fermented milk drink containing 1.0×108 cfu/ml of LcS daily for 14 days, and to maintain their dietary habit and life style. During and at the end of the ingestion period, both culture method (identity confirmed by ELISA) and 16s rRNA sequencing results revealed that viable LcS (7.27 and 7.64 log10 cfu/g of faeces at the ingestion period Day 7 and Day 14, respectively) and Lactobacillus could be recovered from the faeces of all the subjects. The viable LcS count from male and female were comparable for each time point. Before consumption (baseline) and 14 days after cessation of consumption of the fermented milk, LcS was not detected in most of the subjects. In this study condition, the composition of the major gut microbiota (>0.1% in relative abundance of genus) and characteristics of defaecation such as stool consistency and frequency of defecation did not change throughout the study before and after ingestion of LcS. LcS was able to survive passage through the gastrointestinal tract of Singapore adults without sustainable colonisation, but the effect of LcS on microbiota modulation, stool consistency and frequency was not observed under this study condition.

Evaluation of antibacterial activities of colistin, rifampicin and meropenem combinations against NDM-1-producing Klebsiella pneumoniae in 24 h in vitro time-kill experiments.

OBJECTIVES: To investigate the activity of colistin alone or in double and triple combination with rifampicin and meropenem against NDM-1-producing Klebsiella pneumoniae. METHODS: Eight isolates of NDM-1-producing K. pneumoniae were exposed to clinically relevant antibiotic concentrations in 24 h time-kill experiments. Three colistin concentrations were used for two of the strains. Resistance development was assessed with population analysis and sequencing of the mgrB and pmrB genes. RESULTS: Initial killing was achieved with colistin alone, but with considerable regrowth at 24 h. Combinations including colistin and rifampicin were bacteriostatic or bactericidal against all strains. Colistin plus meropenem was bactericidal against one strain, but, overall, meropenem showed little additive effects. Higher concentrations of colistin did not enhance antibacterial activity. Resistant populations and deletion or mutations in the mgrB and pmrB genes were frequently detected in endpoint samples after exposure to colistin alone. CONCLUSIONS: Based on the results of this and previous studies, the combination of colistin and rifampicin seems promising and should be further explored in vivo and considered for clinical evaluation. Meropenem seems less useful in the treatment of infections caused by high-level carbapenem-resistant NDM-1-producing K. pneumoniae. Higher colistin concentrations did not result in significantly better activity, suggesting that combination therapy might be superior to monotherapy also when colistin is prescribed using high-dose regimens in accordance with current recommendations.