Inclusion Criteria:

• Diagnosis of PSC established by alkaline phosphatase >1.5 times and/or two fold elevation of liver transaminases (AST and/or ALT) for at least 6 months duration.
• Cholangiography demonstrating intrahepatic and/or extrahepatic biliary obstruction, beading, or narrowing consistent with PSC.
• Both genders.
• Age ≥ 18 years old and < than 75 years old.
• Patient's informed consent for study participation.

Exclusion Criteria:

• Treatment with systematic antibiotics, azulfidine, ursodeoxycholic acid, corticosteroids, colchicine, methotrexate, azathioprine, cyclosporine, chlorambucil, budesonide, pentoxifylline, tacrolimus, silymarin or prednisone in the preceding three months.
• Active drug or alcohol use.
• Prior history of allergic reactions to the antibiotics which will be used in the study.
• Any condition that, in the opinion of the investigator, would interfere with the patients' ability to complete the study safely or successfully.
• Evidence of decompensated liver disease such as recurrent variceal bleeding, refractory ascites or spontaneous hepatic encephalopathy.
• Anticipated need for transplantation in one year (Mayo survival model <80% one-year survival without transplant).
• Findings highly suggestive of liver disease of other etiology such as chronic alcoholic liver disease, chronic hepatitis B or C infection, hemochromatosis, Wilson's disease, 1-antitrypsin deficiency, non-alcoholic steatohepatitis, primary biliary cirrhosis or secondary sclerosing cholangitis.
• Pregnancy or current lactation. Subjects becoming pregnant during the study will be withdrawn.