Bacterial Pathogens in Acute Myeloid Leukemia

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Yoav Golan, MD, MS, FIDSA, attending physician and associate professor of medicine at Tufts University School of Medicine, Boston, MA, describes common bacterial pathogens that patients with acute myeloid leukemia (AML) may encounter.

Individuals with acute myeloid leukemia (AML) are exposed to a variety of microbes that are potentially pathogenic and cause disease. Among the most important bacterial pathogens are those that colonize the skin, gastrointestinal tract, and the upper airways, explains Yoav Golan, MD. The implementation of vascular accesses often violates the integrity of these membranes, and the effects of chemotherapy disrupt the mucosa of the gastrointestinal tract and oral pharynx, allowing bacteria to invade. Pathogens that are commonly encountered in the healthcare environment tend to be more resistant to antibiotic treatments and include Pseudomonas, Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), some strains of coagulase negative Staphylococci, and enteric bacteria including E. coli and Klebsiella.

One of the important aspects of infections, infection control, and treatment in patients with AML is that they have minimal support from their immune system and must rely on adequate use of antimicrobials to treat infections, notes Golan, which presents a major challenge for prevention and treatment. Infection control is complicated by the fact that many patients with AML have prolonged neutropenia that persists for several weeks. During those weeks, patients may travel to environments outside of their homes, and exposure to these different surroundings may put them at greater risk for infection.

The challenges of infection control are shared between patients with AML who do not undergo bone marrow transplantation and those who do eventually undergo bone marrow transplantation. Both populations have extended exposures to the healthcare environment, says Golan, but not all patients with AML have equal risk of infections. The risk of infection depends on two main factors, the expected severity of their neutropenia and the duration of neutropenia. The highest risk individuals are those whose neutropenia is expected to be severe (less than 100 cells/mL) and continue for longer than one week, while the lowest risk patients have neutropenia that is not predicted to go below 100 cells/mL or last for more than seven days. These groups have a different risk of infection where different prevention approaches are employed, states Golan.