Patient description: A 17 year old boy complains of vomiting, non-bloody diarrhea, abdominal pain, fever, chills and loss of appetite for the past 3 days. He ate a salad at a restaurant prior to his diarrhea onset. Physical exam was remarkable for pallor, jaundice, and diffuse abdominal tenderness. Lab results were as follows: Hemoglobin: 9.7 g/dL Platelet: 110,000 /cu.mm Creatinine: 3.6 mg/dL blood urea nitrogen (BUN): 73 mg/dL direct bilirubin: 2.4 mg/dL lactate dehydrogenase (LDH): 881 IU/L (normal: 110-265 IU/L) Peripheral blood smear showed a moderate number of schistocytes and helmet cells. Shiga-like toxin-producing E. coli (STEC) stx1/stx2 were found in stools. He has no other underlying disease and he is not on any medications.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Clostridium Difficile (C. Difficile) Subjects must meet all of the following to be enrolled in the study: 1. The subject or a legally authorized representative must sign informed consent; 2. The subject must be 18 years of age; 3. Subjects must have a diagnosis of CDI defined as follows: 1. Diarrhea, defined as a change in bowel habits, with > 3 liquid stools or unformed bowel movements (UBMs) [Bristol Stool Scale 6 or 7] or > 200 mL unformed stool for subjects having rectal collection devices in the 24 hours prior to start of study drug; AND 2. The subject has the following positive tests on a stool sample produced within 72 hours prior to the start of study drug as determined by A positive C. difficile glutamate dehydrogenase (GDH) test by a Food and Drug Administration (FDA)-cleared enzyme immunoassay (EIA); AND A positive toxin test (presence of either C. difficile Toxin A [TcdA] and/or C. difficile Toxin B [TcdB]) by an FDA-cleared EIA; OR A positive toxin gene test (presence of either C. difficile Toxin A gene [tcdA] and/or C. difficile Toxin B gene [tcdB]) by an FDA-cleared nucleic acid amplification test; OR A positive cell cytotoxicity neutralization assay; OR positive toxigenic culture; 4. Subjects with a diagnosis of non-severe CDI must have a white blood cell (WBC) count ≤15,000 cells/µL (15 × 10^9 cells/L) and serum creatinine <1.5 mg/dL; 5. Subjects with a diagnosis of severe CDI must have any of the following a. Criterion 1 i. WBC count >15,000 cells/µL (15 x 10^9 cells/L); OR ii. Serum creatinine 1.5 mg/dL; b. Criterion 2 i. Evidence of pseudomembranous colitis on endoscopy; OR ii. Colitis on computed tomography or magnetic resonance imaging scan or ultrasound; c. Criterion 3 i. Severe abdominal pain, vomiting, ileus, temperature >38.9°C, WBC count >15,000 cells/µL (15 x 10^9 cells/L), or albumin level <2.5 g/dL in which CDI is strongly suspected and other non-CDI causes of infection have been ruled out; 6. The subject has received no more than 24 hours of prior antimicrobial treatment for the current episode of CDI with oral/rectal vancomycin, IV/oral metronidazole, or oral fidaxomicin prior to Screening; 7. Female subjects of non-childbearing potential must be either surgically sterile (hysterectomy, bilateral tubal ligation, salpingectomy, and/or bilateral oophorectomy at least 26 weeks before Screening) or post-menopausal, defined as spontaneous amenorrhea for at least 2 years, with follicle-stimulating hormone in the post-menopausal range at Screening, based on the central laboratory's ranges; 8. Women of childbearing potential (ie, not post-menopausal or surgically sterilized) must have a negative urine and serum pregnancy test result before randomization. Participating women of childbearing potential must agree to use 1 highly effective method of contraception AND an acceptable barrier method (condom plus spermicide) OR 2 highly effective methods of contraception throughout the duration of the study and for 30 days following the last study drug administration. Highly effective methods of contraception that result in a low failure rate (ie, <1% per year) when used consistently and correctly the following: 1. Combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral, intravaginal, or transdermal), progestogen-only hormonal contraception associated with inhibition of ovulation (oral, injectable, or implantable), intrauterine device, or intrauterine hormone-releasing system for at least 12 weeks before Screening; 2. Bilateral tubal occlusion or vasectomized partner at least 26 weeks before Screening; 3. Sexual abstinence; NOTE: True abstinence, when in line with the preferred and usual lifestyle of the subject, is considered a highly effective method only if defined as refraining from heterosexual intercourse during the entire period of risk associated with the study drug treatment. Periodic abstinence (eg, calendar, ovulation, symptothermal, post ovulation methods) and withdrawal are not acceptable methods of contraception; 9. Male subjects must agree to abstain from sperm donation and use condoms with spermicide during sexual intercourse between Screening and at least 90 days after administration of the last dose of study drug. Male subjects must ensure non pregnant female partners of childbearing potential comply with the contraception requirements in Criterion 8  Subjects will not be enrolled in the study if they meet any of the following 1. The subject is likely to require surgical intervention (eg, subjects with fulminant CDI who fail to respond and progress to systemic toxicity, peritonitis, or toxic colonic dilatation and bowel perforation) and/or be switched to an already approved treatment regimen in the coming 48 hours due to a rapidly degrading condition; 2. The subject displays evidence of acute renal impairment with a creatinine clearance of <50 mL/min as measured by the Cockcroft Gault formula; 3. The subject is receiving hemodialysis or continuous venous hemofiltration; 4. The subject has ALT or AST serum levels >3 × ULN, and total bilirubin serum concentration >2 × ULN per the testing laboratory; 5. The subject displays evidence of chronic hepatic impairment (Child-Pugh class B or C); 6. The subject is pregnant or breastfeeding; 7. The subject requires the ongoing use of anti-motility agents (eg, anti-diarrheals, anti peristaltics) or laxatives, unless approved by the Medical Monitor. Chronic and continued use of such products may be permitted during the study if bowel motility has stabilized; 8. The subject requires the ongoing use of concomitant antibiotics to treat CDI (other than study drug) (eg, oral/rectal vancomycin, IV/oral metronidazole, oral fidaxomicin) or IV immunoglobulin; 9. The subject has a known hypersensitivity or intolerance to DNV3837 or sorbitol; 10. The subject has a history of active hepatitis B virus or hepatitis C virus that requires ongoing therapy, or human immunodeficiency virus with the most current cluster of differentiation 4 (CD4+) <200 copies/mL; 11. The subject has participated in other clinical research studies using an investigational antibacterial or non antibacterial agent within 1 month prior to Screening; 12. The subject is unable or unwilling, in the judgment of the Investigator, to comply with the protocol; or 13. The subject is an employee of the Investigator, study site, Sponsor, or contract research organization with direct involvement in the proposed study or other studies under the direction of the Investigator, study site, or Sponsor, or a family member of the site employee or the Investigator