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Patient receiving chemotherapy
Photo by Rhoda Baer

SAN DIEGO—Monitoring the microbiome during chemotherapy might help reduce infections in leukemia patients, according to research presented at ICAAC/ICC 2015.

The researchers studied buccal and fecal samples from patients with acute myeloid leukemia (AML) who were undergoing induction chemotherapy.

This revealed that decreased microbial diversity was associated with an increased risk of infection.

Jessica Galloway-Peña, PhD, of The University of Texas MD Anderson Cancer Center in Houston, and her colleagues described this work in a poster presentation at the meeting (poster B-993).

The team analyzed samples from 34 AML patients. All of the patients received prophylactic antimicrobials, and 91% received systemic antibiotics. The patients received an average of 5.4 different antibiotics for an average duration of 6.5 days.

The researchers collected buccal and fecal specimens from the patients every 96 hours over the course of induction chemotherapy. This yielded 276 buccal and 202 fecal samples—an average of 8 oral and 6 stool samples per patient.

The team used 16S rRNA V4 region sequencing to assign bacterial taxa and calculate α- and β-diversities. They had a total of 16,082,550 high-quality reads.

Analyzing these data, the researchers found that decreased microbial diversity, both at baseline and throughout induction, was associated with an increased risk of infection.

“We found the baseline microbial diversities from stool samples were significantly lower in patients that developed infections during chemotherapy compared to those that did not [P=0.006],” Dr Galloway-Peña said.

She and her colleagues also found that, overall, there was a significant decrease in oral (P=0.006) and intestinal (P<0.001) microbial diversity over the course of chemotherapy, although not all patients experienced decreases. There was a linear correlation between oral and stool microbiome changes (P=0.004).

In addition, over the course of induction, there was a significant increase (P=0.02) in the rates of bacterial domination (>30% of the microbiome dominated by 1 organism) by common causes of bacteremia, such as Streptococcus, Bacteriodes, Rothia, and Staphylococcus.

However, if patients were able to maintain a healthy microbiome overall or if they experienced an increase in microbial diversity over the induction course, they remained infection-free in the 90 days after induction.

Dr Galloway-Peña and her colleagues also assessed the role common antibiotics play in microbial diversity. And they found that carbapenems significantly decreased diversity.

There was a significant difference in oral and stool diversity when patients received carbapenems for at least 72 hours and when they did not (P=0.03). But there was no significant difference for piperacillin-tazobactam (P=1.0) or cefepime (P=0.48).

“This study shows that, in the future, doctors could use microbiome sampling in order to predict the chance of infectious complications during chemotherapy and that monitoring of a patient’s microbiome during induction chemotherapy could also predict their risk for microbial-related illness during subsequent treatments,” Dr Galloway-Peña said.

In addition, monitoring the microbiome could potentially mitigate the overuse of antimicrobials by allowing physicians to stratify patients according to their risk of developing an infection. end hematology article

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