Despite the current management of leukemia, the immune system of these patients is profoundly altered, and they continue to have many types of infections. They contribute a great deal to the morbidity and mortality of patients with leukemia, and it is important to know what types of infections are more common and why.
Leukemia features an accumulation of leukocytes that may appear to be mature, but are functionally incompetent. They are not able to trigger an immune response when they should and fail to defend the body against pathogens.
There are different types of infections in patients with leukemia. The most important are as follows:
Febrile neutropenia
Neutropenia is a reduction of blood levels of neutrophils, a type of white blood cells. They are essential to protect the body against bacterial pathogens and having leukemia with fever and low levels of neutrophils are referred to as febrile neutropenia.
Febrile neutropenia is associated with various infections in different parts of the body. For example, periodontal and oral infections by gram-negative bacteria, herpes simplex virus, and candida. Gastrointestinal infections by Clostridium difficile and anaerobes, associated with diarrhea. Lower respiratory tract infections, especially pneumonia due to pneumococci and gram-negative bacilli.
More severe infections in febrile neutropenia include bloodstream infections with staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus agents. As mentioned above, we can also have cellulitis and folliculitis caused by streptococci and staphylococci.
Infections with resistant bacteria
One of the most worrying facts about patients with leukemia is that they are susceptible to infections with bacteria resistant to antibiotics. They are continuously exposed to infections, doctors use various antibiotics over the course of the disease to treat infections, and they would naturally develop resistant organisms that make it worse still, and more difficult to manage.
The most common resistant bacteria are methicillin-resistant Staphylococcus aureus (they are resistant to penicillin, quinolones, and cephalosporin antibiotics), vancomycin-resistant staphylococci (they are resistant to a wide variety of antibiotics, especially vancomycin), and other multidrug-resistant bacteria that include Klebsiella and E. coli resistant to penicillin, cephalosporin and quinolones. In some cases, antibiotic resistance is so severe that doctors need to use a group of antibiotics called carbapenems.
Invasive fungal infections
We have mentioned above fungal infections, such as candida infections appearing in the oral cavity. However, patients with leukemia will also have complicated fungal infections that do not only stay in one tissue but migrate to other parts of the organism. The most common invasive fungal infection is candida in patients with severe immune suppression, and usually when they have central venous catheters.
Other fungal infections that become disseminated include Aspergillus infections, which usually start in the sinuses or lungs and affect the central nervous system in cases of prolonged neutropenia or in patients using steroids. If the patient has suffered from histoplasmosis, coccidiomycosis, or blastomycosis, they may reactivate during the course of the disease, and some of them become disseminated throughout the body.
Infections in non-neutropenic patients
Patients with normal or relatively normal neutrophil count may also have atypical infections in leukemia. These patients may be subject to steroids and other immunosuppressive agents that increase the risk of infections such as meningitis by Listeria monocytogenes or pneumonia by Pneumocystis jirovecci. In cases of listeriosis, ampicillin is often the drug of choice, but doctors may also consider using vancomycin, fluoroquinolones and even carbapenems depending on the sensitivity of the strain.
Other infections in this group of patients include viral infections (Herpes zoster virus, and Epstein-Barr virus), tuberculosis and atypical mycobacterial infections in cases of chronic leukemia.
Other pathogens
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.
Infections associated with chemotherapy
Patients with leukemia are treated with chemotherapeutic agents, but using these carry out a series of risks, including certain types of infection. For example, treatment with doxorubicin and other anthracyclines induce cellular death in blood cells and may reduce the neutrophil count. Alkylating agents like cyclophosphamide prevents DNA repair in leukemic cells, but also in normal cells. This leads to a higher incidence of pyogenic infections (staphylococcus aureus, streptococcus infections, Klebsiella, and others).
As you can see, leukemia is a very complex disease that should not be taken lightly. Even treatment for leukemia may lead to the development of leukemia rash and leukemia infections. Thus, it is usually administered under a hospital setting, and patients are isolated with many precautions to prevent infections by opportunist agents. All of these measures are not excessive. They are fundamental for the recovery of the patient and his prognosis.
References
Chandran, R., Hakki, M., & Spurgeon, S. (2012). Infections in leukemia. Sepsis-An Ongoing and Significant Challenge.
Betz, B. L., & Hess, J. L. (2010). Acute myeloid leukemia diagnosis in the 21st century. Archives of pathology & laboratory medicine, 134(10), 1427-1433.
Creutzig, U., van den Heuvel-Eibrink, M. M., Gibson, B., Dworzak, M. N., Adachi, S., de Bont, E., … & Lehrnbecher, T. (2012). Diagnosis and management of acute myeloid leukemia in children and adolescents: recommendations from an international expert panel. Blood, The Journal of the American Society of Hematology, 120(16), 3187-3205.