We have bacteria throughout the body, especially in the skin and mucosa. Thus, doctors may disregard certain positive culture results in the belief that these are not pathogenic bacteria but normal flora. However, leukemia patients are immunocompromised hosts, and several bacteria that would not usually harm immunocompetent individuals will cause much trouble in leukemia patients.
One example is Fusarium, which is commonly found in the skin, but it is a mold that may develop fatal and rapidly progressing infections in some patients. Corynebacterium bacilli are common in catheter infections, but in leukemia patients, it may lead to sepsis with a 34% mortality. Another example is Bacillus cereus, which is a common cause of transient foodborne illness, but in leukemia patients, it causes necrotizing gastritis, septic shock, pneumonia, brain abscess, and multiorgan failure.