The goal of this study is characterize the changes in bacterial diversity of the nares of hemodialysis patients. Another goal is to determine when hemodialysis patients become colonized with the bacteria Staphylococcus aureus, as nasal colonization with S. aureus is a major risk factor for invasive infection in hemodialysis patients. Fifteen subjects will be recruited into the study. Nasal swabs will be collected every month for six months or until one month after S. aureus colonization in order to determine any changes in the bacterial communities of the nose. Clinical data will also be collected to evaluate the possible influence of external factors on changes in the microbial communities in the patients' noses. This study will provide preliminary data on whether oral- and/or nasal-administered probiotics can eliminate nasal carriage of S. aureus.

Inclusion Criteria:

• Male and female subjects aged 18 years or older
• On a stable hemodialysis schedule three times a week at Tufts Medical Center outpatient hemodialysis unit
• Able to speak English, Spanish, Cantonese, or Mandarin (One of these languages is spoken by >95% of our hemodialysis population)
• Provides informed consent to participate in the study
• No plans to be absent from the dialysis unit in the next 6 months
• Willingness to report on adverse events during the study period

Exclusion Criteria:

• Patients in which hemodialysis was indicated for acute renal failure secondary to septic shock, acute tubular necrosis, or other condition which is felt to be temporary or secondary to a life threatening illness or likelihood of hemodialysis for less than 6 months.
• Treatment with systemic anti-staphylococcal antibiotic therapy within 30 days prior to enrollment or planned use of topical mupirocin applied to the nares
• Receiving peritoneal dialysis (concordance between the colonizing and infecting strain is not as high as in the hemodialysis population (105))
• Absolute neutrophil count less than 500/mm3 or anticipated fall in neutrophil count < 500/mm3 (e.g. as a result of recent chemotherapy)
• Bleeding diathesis such as platelets count less than 20 or INR >4 within the last 30 days
• On immunosuppressive therapy
• Anticipated renal transplant during the next 6 months
• Evidence of active bowel leak, acute abdomen or colitis

Patients from the Boston Dialysis Center Inc outpatient hemodialysis clinic of Tufts Medical Center.