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.
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.
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 ...