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Infection is a major cause of morbidity and mortality in patients with severe inherited or acquired neutropenia or aplastic anemia, qualitative disorders of neutrophils, and, notably, those persons receiving chemotherapy for treatment of hematologic neoplasms. Severe neutropenia and monocytopenia often result from the combined effects of replacement of marrow with malignant cells and superimposed intense chemotherapy. The severity and duration of the neutropenia determine the risk of infection. Bacterial infections may result in rapid clinical deterioration and, if not treated appropriately, death. Fungal, viral, and parasitic infections also may result in potentially lethal complications during or after chemotherapy. Methods of diagnosis of bacterial, fungal, viral, and protozoal infection are considered and treatment regimens described. The use of home antibiotic may be appropriate for certain patients. Because prevention of infection during periods of neutropenia should reduce morbidity and improve outcome, attention is focused on prophylaxis therapy against bacterial, parasitic, viral, and/or fungal infections.

Acronyms and Abbreviations

Acronyms and abbreviations that appear in this chapter include: CMV, cytomegalovirus; MRSA, methicillin-resistant Staphylococcus aureus; RSV, respiratory syncytial virus.

The risk of infection exists in many persons with hematologic diseases, including patients with severe inherited or acquired neutropenia or aplastic anemia, qualitative disorders of neutrophils, and those persons receiving intensive, marrow-suppressive chemotherapy. The profound pancytopenia that results from cytoreductive chemotherapy is a common manifestation of hematopoietic suppression. During the periods of neutropenia that follow such chemotherapy, infection develops in most patients. Patients with neoplasms of the lymphoid system commonly manifest altered humoral and cellular immunity, resulting in an increased incidence of nonbacterial infection.

Severity of Neutropenia

Bacterial, fungal, viral, and parasitic organisms may cause infection in neutropenic patients. Bacterial infections are the most frequent and usually the most serious. The risk for bacterial infection increases when the neutrophil count falls to less than 500/μL (0.5 × 109/L) and becomes especially pronounced at neutrophil counts less than 100/μL (0.1 × 109/L).1 The rate of decline and duration of neutropenia are important in determining the risk of bacterial infection. Disruption of mucosal barriers, especially in the oral cavity, esophagus, and bowel, further favors the development of infection by providing portals of entry.

Bacterial Pathogens

Historically, Gram-negative bacilli have been the most commonly isolated pathogens. These organisms include Klebsiella, Escherichia coli, Pseudomonas, and Proteus. These bacteria are responsible for a variety of infections, including pneumonia, soft-tissue infections, perirectal infections, and primary bacteremia. Urinary tract infections are less frequent unless a urinary catheter is present or urinary tract obstruction has developed. Meningitis is uncommon.

At present, roughly half of all documented infections in neutropenic patients are caused by Gram-positive pathogens. Staphylococcal species and enterococcus are now the pathogens most frequently isolated from neutropenic patients.2 This finding may result, in part, from the popularity of semipermanent venous catheters and from the ...

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