The mouth is a complex biological ecosystem normally containing over 700 different species of bacteria. These bacteria live in an exopolysacchride matrix biofilm. Usually, bacteria colonize the oral cavity benignly. However, there are several studies in critically ill patients demonstrating changes in oral flora with acute illness. Identification of respiratory pathogens in the mouth has led researchers to hypothesize that a relationship exists between the oral cavity and pulmonary infections. A common complication of allogeneic peripheral blood stem cell transplant (PBSCT) is infection and pneumonia. Identification of potential pathogens in the oral cavity of allogeneic stem cell patients could indicate a similar association between oral pathogens and infection. A few studies describe the oral microbial community in these patients and the possibility that these organisms are a source of infection.

The primary objective of this study is to describe the changes in oral microbial flora of allogeneic SCT patients at three time points during their treatment and recovery. Observed differences in microbial organisms from baseline (prior to transplantation), through neutropenia (within 48 hours of nadir post-transplantation) and myeloid engraftment (14-21 days post transplantation) will be described.

In the course of their treatment, if patients develop respiratory signs and symptoms that require either a re-admission to an inpatient unit or intensive care unit admission, then additional oral specimens will be collected.

The secondary objective is to assess the oral microbial flora found after development of respiratory signs and symptoms in allogeneic PBSCT patients in the first 100 days post-transplant. In addition, if the patient requires intubation, tracheal aspirates and oral specimens will be collected.

The population is composed of adult patients who are planning to undergo an allogeneic PBSCT and can provide informed consent. The design is a prospective, descriptive study of the microbial flora of the oral cavity of adult allogeneic stem cell transplant patients. Saliva specimens, dental plaque and mucosal brushings will be collected at the three different times. Oral specimens will be obtained from patients who develop respiratory signs or symptoms that require an additional inpatient or intensive care unit admission. Patients will be followed and assessed for respiratory signs, symptoms, inpatient or ICU admission until day 100 post-transplant. The presence of bacteria (type and species) will be determined by molecular genetics. The identification of bacteria will be studied using various comparative molecular techniques, including DNA arrays and Real-Time Polymerase Chain Reaction (RT-PCR).