We previously reported on the effects of Lactoplantibacillus plantarum DR7 on reducing Upper Respiratory Tract Infections (URTI) symptoms' score and frequency in 109 adults upon a 12-week consumption at 109 colony-forming units (CFU)/day, but several limitations were detected in the publication. Thus, the present study re-analyzed some data with the aim to address some of these weaknesses, and presents new data on duration of URTI and consumption of URTI-associated medication, as compared to the placebo. Our re-analyses found probiotic administration significantly reduced the proportion of patient days of URTI and of fever (all p < 0.05). Recent history of URTI was a prevalent co-factor in affecting duration of URTI symptoms and fever, while other demographic and clinical factors had no influence. Exploratory analyses suggested probiotic had an earlier benefit in patients without a recent history of URTI compared to those with a recent history of URTI. Therefore, recent history of infections could have a modulatory effect on probiotic efficacy. Average number of months with reported use of URTI-related medication was 3.4-times lower in the probiotic group as compared to placebo (p = 0.016) during the intervention. Taken together, our present new data further support previous findings that DR7 probiotic had a beneficial effect on URTI.
Keywords: Lactobacillus plantarum; URTI; fever; immunity; probiotic.