This is a randomized (1:1), double-blind, double-dummy, phase I study to compare the effects of Omadacycline versus Moxifloxacin on gut microbiota and the resistomes in healthy adult volunteers.The study consists of 3 phases: Screening, double-blind treatment, and follow-up. Healthy volunteers aged 18-40 years, who meet entry criteria, are randomly assigned to a treatment group using an Interactive Voice Response System/Interactive Web Response System (IxRS) and receive the first dose of the study drug.

The study consists of 3 phases: Screening, double-blind treatment, and follow-up. Healthy volunteers aged 18-40 years, who meet entry criteria, are randomly assigned to a treatment group using an Interactive Voice Response System/Interactive Web Response System (IxRS) and receive the first dose of the study drug.

Inclusion Criteria:

1. Sign an Informed Consent Form (ICF) prior to the commencement of any study-related procedures.
2. Chinese healthy male and female subjects aged between 18 and 40 years (inclusive).
3. Body mass index (BMI) between 18.5 and 23.9 kg/m2 (inclusive).
4. Complete the stool sample collections required during screening.

Exclusion Criteria:

1. Subjects with clinically significant medical history of cardiovascular, hepatic, renal, gastrointestinal or psychiatric conditions, or any other condition as deemed by the investigators that may potentially jeopardize subject safety or impact study outcomes.
2. Subjects who have undergone any major surgery within 4 weeks prior to the first dose of study drug administration.
3. Subjects who have previously undergone gastrointestinal surgery that may affect the absorption of the study drug (eg. Intestinal resection surgery, fistula surgery).
4. During screening, subjects with positive tests for hepatitis C antibodies, hepatitis B surface antigen, or hepatitis B virus (HBV) DNA or HBV RNA, or known positive tests for human immunodeficiency virus (HIV).
5. Subjects with Fridericia-corrected QT interval (QTcF) > 450 milliseconds (males) or > 470 milliseconds (females); or known to have long QT syndrome; or using medications that may cause arrhythmia or prolong QT interval, and/or experiencing tachyarrhythmia.
6. Subjects with a history of irritable bowel syndrome (with or without constipation) -