Patient description: The patient is a 60-year-old woman admitted to the stroke department with a recent history of a second course of intravenous antibiotics for aspiration pneumonia. She is febrile and complained of abdominal pain and diarrhea (bowel movements eight times in 3 hours, large volumes of greenish, liquid stool each time). The patient's abdomen is generally tender and distend with hyperactive bowel sounds. She is febrile (38.4°C), tachycardic (113/min) and hypotensive (80/40 mmHg). The stool samples must were positive for Clostridium difficile toxin.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Melanoma Have a histologically or cytologically confirmed diagnosis of unresectable stage III or IV melanoma. Patient may not have a diagnosis of uveal or mucosal melanoma Have received any number of prior systemic therapies for metastatic disease. Prior radiation therapy (any number) and interferon use (any formulation and/or duration) in the adjuvant or metastatic disease settings is permitted. Vaccine therapy will be counted as systemic therapy Patient must currently be receiving systemic PD-1 immunotherapy with pembrolizumab or nivolumab to be eligible. Patients who have received PD-1 immunotherapy in the adjuvant setting and then replaced are eligible Must be PD-1 inhibitor refractory/resistant defined as having received at least 2 doses of pembrolizumab with documented systemic disease progression on staging imaging. PD will be defined as increase in tumor burden > 20% relative to nadir (minimum recorded tumor burden) by v1.1. Once PD is confirmed, initial date of PD documentation will be considered as the date of disease progression. Patients can be enrolled at any time following initiation of PD-1 therapy assuming they have not had (at any time) a record of response to PD-1 therapy (prior best response of stable disease acceptable; prior best response of complete/partial response - unacceptable). For patients receiving adjuvant PD-1 inhibitor therapy, initial date of PD documentation will be considered as the date of disease progression Patients with CNS progression (parenchymal but not leptomeningeal) are eligible if CNS metastases are treated and deemed stable (with a repeat CT/MRI imaging study) prior to the enrollment date. If radiation is used to treat CNS parenchymal disease, a 2 week washout period will apply (counted from Day 1 treatment). Stability must be confirmed with a repeat CT/MRI imaging study performed as part of the screening evaluation (at least 2 weeks after radiation). Patients with new CNS metastases identified during screening are ineligible Consent to receive FMT administered endoscopically (colonoscopically) and undergo necessary bowel preparation pre-procedure Understand infectious risks associated with FMT administration. Although FMT infusate has been screened for bacteria, viruses, fungi and parasites there is a risk of transmission of known and unknown infectious organisms contained in the donor stool. Post-FMT bacteremia (e.g. E. coli), sepsis and fatal events may rarely occur Understand non-infectious risks associated with FMT administration. Possible allergy and/or anaphylaxis to antigens in donor stool; theoretical risk of developing disease possibly related to donor gut microbiota including but not limited to: obesity, metabolic syndrome, cardiovascular disease, autoimmune conditions, allergic/atopic disorders, neurologic disorders, psychiatric conditions and malignancy  Presence of absolute contra-indications to FMT administration: Toxic megacolon Severe dietary allergies (e.g. shellfish, nuts, seafood) Inflammatory bowel disease Anatomic contra-indications to colonoscopy Patients receiving PD-1 therapy whose disease is responding or stable (as defined by v1.1) Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy or used an investigational device within 4 weeks of the first dose of treatment Highly symptomatic patients (e.g., declining ECOG performance status; rapidly worsening symptoms; rapid progression of disease; progression of tumor at critical anatomical sites (e.g., spinal cord compression) requiring urgent alternative medical intervention) are not eligible Expected to require any other form of systemic or localized antineoplastic therapy while on study Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy (> 10 mg prednisone daily or equivalent) or any other form of immunosuppressive therapy prior to trial treatment. Patients receiving systemic steroids at physiologic doses are permitted to enroll assuming steroid dose is not above the acceptable threshold (> 10 mg prednisone daily or equivalent) Has a known history of a hematologic malignancy, primary brain tumor or sarcoma, or of another primary solid tumor, unless the patient has undergone potentially curative therapy with no evidence of that disease for five years. NOTE: The time requirement also does not apply to patients who underwent successful definitive resection of basal or squamous cell carcinoma of the skin, superficial bladder cancer, in situ cancers including cervical cancer, breast cancer, melanoma, or other in situ cancers Active central nervous system (CNS) metastases and/or leptomeningeal involvement. Patients with treated brain metastases will be re-screened (MRI brain or CT head with IV contrast). Patients with previously treated brain metastases may participate provided they are stable (without evidence of progression by MRI/CT for at least two weeks prior to the first dose of study drug), have no evidence of new or enlarging brain metastases and are off systemic steroids (≤ 10 mg/day prednisone or equivalent) for at least one weeks prior to enrollment. Patients with leptomeningeal disease (leptomeningeal enhancement on MRI/CT imaging and/or positive CSF cytology) are not eligible to enroll. Patients with no history of CNS disease will not require a repeat MRI brain unless they have symptoms to suggest new brain metastases Had a severe hypersensitivity reaction to treatment with pembrolizumab or any of its excipients Has an active autoimmune disease or a documented history of autoimmune disease or syndrome that requires systemic steroids or immunosuppressive agents. Patients with vitiligo, type I diabetes, resolved childhood asthma/atopy are exceptions to this rule. Patients who require intermittent use of bronchodilators or local steroid injections are not excluded from the study. Patients with hypothyroidism stable on hormone replacement are not excluded from the study