This prospective, multicenter, randomized, double-blind, placebo-controlled clinical study, into the group of children in the hospital that use clinical antibiotics from one month to three years old，by observing the given antibiotics at the same time with the whole bowel raw or placebo, prevent the happening of the antibiotic associated diarrhea, evaluate the whole bowel prevention clinical efficacy and safety of AAD.

This prospective, multicenter, randomized, double-blind, placebo-controlled clinical study, into the group of children in the hospital that use clinical antibiotics from one month to three years old，by observing the given antibiotics at the same time with the whole bowel raw or placebo, prevent the happening of the antibiotic associated diarrhea, evaluate the whole bowel prevention clinical efficacy and safety of AAD.

Outcome measures

1. MAIN OUTCOME MEASURES: The incidence of diarrhea (stool frequency and character daily rates), the duration of diarrhea, the degree of diarrhea occur.
2. Secondary outcomes: intestinal flora and relevant metabolites, micro-environmental changes.

Inclusion Criteria:

1. Children aged 1-3 years
2. no diarrhea-related symptoms
3. the diagnosis of lower respiratory tract infection (acute bronchitis, pneumonia) in hospitalized children
4. the need for penicillins, cephalosporin antibiotic treatment, treatment for 7-14 days, combined with other antimicrobial agents alone
5. parent or guardian signed informed consent (6）Not used in children with related traditional Chinese medicine injection

Exclusion Criteria:

1. diarrhea in the group, or 2 weeks before admission into children with diarrhea
2. children with ICU wards, digestive tract malformations, children with gastrointestinal surgery, congenital heart disease, artificial heart surgery, children with rheumatic heart disease, infective endocarditis
3. receiving immunosuppressive agents in children
4. Children who received any probiotic preparation 2 weeks before enrollment