Kate Johnson

September 22, 2015

SAN DIEGO — The microbiome of patients with acute myelogenous leukemia (AML) has a significant impact on the risk for infectious complication in the first 3 months of induction chemotherapy, results from a new study suggest.

"We can probably use baseline microbiome diversity, as well as the change in microbiome diversity during chemotherapy, to risk-stratify patients for infectious complications," said investigator Jessica Galloway-Peña, PhD, from the University of Texas M.D. Anderson Cancer Center in Houston.

"The majority of patients experience neutropenic fever, which is not uncommon for AML patients receiving chemo," Dr Galloway-Peña explained. "But a lot of doctors will typically treat the fever empirically, even if it doesn't have any microbiologic or clinical manifestation. We're trying to stop that."

Dr Galloway-Peña presented results from the longest longitudinal analysis of the microbiome in AML patients during induction chemotherapy here at the Interscience Conference of Antimicrobial Agents and Chemotherapy 2015.

The researchers evaluated 276 oral and 202 stool specimens collected from 34 patients with AML every 96 hours during the 26-day course of chemotherapy. Each patient provided an average of 8 oral and 6 stool samples.

 
I would like to use the microbiome as a tool.
 

All patients received prophylactic antibiotics during the course of chemotherapy, and many received other antibiotics. On average, patients received 5.4 antibiotics for 6.5 days.

Of the systemic antibiotics commonly administered, carbapenems decreased oral and stool microbial diversity most significantly (P = .03).

Microbial diversity in baseline stool samples was significantly lower in patients who developed a microbiologically or clinically defined infection during chemotherapy than in those who did not (P = .006).

During the course of chemotherapy, there was a decrease in diversity in the majority of oral specimens (P = .006) and stool specimens (P < .001).

"Of those who maintained or increased their microbial diversity, none got an infection within 90 days," Dr Galloway-Peña reported. However, of the 23 patients who experienced a decrease in diversity, nine got an infection.

In addition, rates of bacterial domination increased over the course of chemotherapy (P = .02).

"The intestine will be dominated by a particular organism, and that's generally the organism you can get infected with. Those organisms can be treated if we can see them before the infection happens," Dr Galloway-Peña explained.

"I would like to use the microbiome as a tool," she told Medscape Medical News. It could help identify which patients need to be treated prophylactically and which don't, and which patients should be put on a specific diet or receive probiotics. "I am also a proponent of fecal transplant — for certain patients," she said.

Question of Causality

The microbiome is "a very thought-provoking field," said Joseph Duncan, MD, from the University of North Carolina at Chapel Hill, who stopped to discuss the poster.

"Using microbiome analysis as a potential marker for clinical course is a very hot topic. I guess the question of causality is still huge," he told Medscape Medical News.

"Whether it's a marker or it actually drives the development of disease is completely wide open, and one of the biggest questions in most of the microbial diversity studies right now," Dr Duncan pointed out. "There may be changes in the host that actually lead to the change in microbial diversity, so it may just be a marker of bad host defenses."

Dr Galloway-Peña and Dr Duncan have disclosed no relevant financial relationships.

Interscience Conference of Antimicrobial Agents and Chemotherapy (ICAAC) 2015: Abstract B993. Presented September 20, 2015.

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