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Essentials of Diagnosis
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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
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General Considerations
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IMPAIRED HUMORAL IMMUNITY
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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
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Risk factor is absolute granulocyte count below 1000/mcL (1 × 109/L), and especially below 100/mcL (0.1 × 109/L)
Increased infections with:
Gram-negative enteric organisms (particularly Pseudomonas)
Gram-positive cocci (particularly Staphylococcus aureus, Staphylococcus epidermidis, and viridans streptococci)
Candida
Aspergillus
Other fungi such as Trichosporon, Scedosporium, Fusarium, and the mucormycoses
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IMPAIRED CELLULAR IMMUNITY
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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
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Infections that occur immediately after the 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 after transplant are related to
The operative procedure and to the hospitalization itself (wound infection, intravenous catheter infection, indwelling urinary [Foley] catheter–related urinary tract infection)
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 after transplant are often related to immunosuppression
Reactivated herpes simplex, varicella-zoster, HBV, 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
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