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Key Features

Essentials of Diagnosis

  • Fever and other symptoms may be blunted because of immunosuppression

  • Organisms considered "nonpathogenic" may cause serious illness

  • The interval since transplantation and the degree of immunosuppression can narrow the differential diagnosis

  • Early empiric broad-spectrum antimicrobial therapy is often indicated because of the high infection-related morbidity and mortality

General Considerations

IMPAIRED HUMORAL IMMUNITY

  • Risk factors

    • Plasma cell myeloma (formerly multiple myeloma)

    • Chronic lymphocytic leukemia (and small lymphocyte lymphoma)

    • Acquired and congenital hypogammaglobulinemia

    • Asplenia

  • Increased infections with encapsulated organisms such as Haemophilus influenzae and Streptococcus pneumoniae

  • Although normally thought of as being linked to impaired cellular immunity, there is an association between rituximab (anti-B cell monoclonal antibody) therapy and development of Pneumocystis jirovecii infection as well as hepatitis B reactivation

GRANULOCYTOPENIA

  • Absolute granulocyte count below 1000/mcL, and especially below 100/mcL

  • Increased infections with gram-negative enteric organisms

    • Pseudomonas

    • Gram-positive cocci (particularly Staphylococcus aureus, Staphylococcus epidermidis, and viridans streptococci)

    • Candida

    • Aspergillus

    • Other fungi such as Trichosporon, Scedosporium, Fusarium, and the mucormycoses

IMPAIRED CELLULAR IMMUNITY

  • HIV infection, lymphoreticular malignancies such as Hodgkin disease, immunosuppressive medications

  • Increased infections by a large number of

    • Bacteria, such as Listeria, Legionella, Salmonella, and Mycobacteria

    • Viruses, such as herpes simplex, varicella, and cytomegalovirus (CMV)

    • Fungi, such as Cryptococcus, Coccidioides, Histoplasma, and Pneumocystis

    • Protozoa, such as Toxoplasma

TRANSPLANTATION

  • Infections immediately after transplant often involve the transplanted organ

    • Lung: pneumonia and mediastinitis

    • Liver: intra-abdominal abscess, cholangitis, and peritonitis

    • Kidney: urinary tract infections, perinephric abscesses, and infected lymphoceles

  • In contrast to solid organ transplants, in stem cell transplants the source of fever cannot be found in 60–70% of patients

  • Most infections that occur in the first 2–4 weeks are related to

    • The operative procedure and to the hospitalization itself (wound infection, intravenous catheter infection, urinary tract infection from a Foley catheter)

    • The transplanted organ

    • Compensated transplantations performed abroad through "medical tourism"; can introduce additional risk for infections, which vary by country and by transplant setting

  • Infections that occur between the first and sixth months are often related to immunosuppression

    • Reactivated herpes simplex, varicella-zoster, and CMV infections are quite common

    • Opportunistic infections with fungi (Candida, Aspergillus, Cryptococcus, Pneumocystis, and others), Listeria monocytogenes, Nocardia, and Toxoplasma are also common

  • After 6 months, when immunosuppression has been reduced to maintenance levels, infections that are found in any population occur

OTHER

  • Patients who are not specifically immunodeficient are at increased risk for infection due to

    • Debilitating injury (eg, burns or severe trauma)

    • Invasive procedures (eg, chronic central intravenous catheters, Foley catheters, dialysis catheters)

    • Central nervous system dysfunction (which predisposes patients to aspiration pneumonia and pressure injury [formerly pressure ulcers])

    • Obstructing lesions (eg, pneumonia due to ...

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