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Infections in immunocompromised patients. I. Pathogenesis, etiology, and diagnosis
Abstract:
Granulocytopenia is the major factor predisposing cancer patients to infection, chiefly by bacteria. Most of the infections are caused by gram-negative aerobic organisms (Escherichia coli, Pseudomonas aeruginosa, and Klebsiella sp) that arise from endogenous gastrointestinal, mucosal, or cutaneous flora (often modified by hospital-acquired pathogens). Some fungi (Candida sp and Aspergillus sp) are also likely to invade granulocytopenic patients. The next most important factor predisposing cancer patients to infection is alteration of anatomic barriers. Mucosal and skin protection is compromised by tumors, radiotherapy, chemotherapy, surgical diagnostic and therapeutic procedures, and intravenous lines and other devices. The pathogens found in cases of altered anatomical barriers are similar to those encountered in patients with granulocytopenia, which is a major cause of alteration of anatomical barriers. The third factor predisposing patients to serious bacterial and nonbacterial infections is immunosuppression, especially in patients with lymphomas, multiple myelomas, and chronic lymphatic leukemia. The pathogens isolated in these patients include Listeria monocytogenes, Salmonella sp, Brucella sp, Mycobacterium sp, and Nocardia asteroides, although P aeruginosa and staphylococci may be found as well. Viruses (herpes simplex, herpes zoster, and vaccinia), parasites, fungi, and Pneumocystis carinii and Toxoplasma gondii are involved in many infections in these patients, in whom cell-mediated immunity is impaired. In neutropenic patients, antimicrobial or antifungal therapy should be instituted before the microbiological diagnosis is made; in immunosuppressed patients, therapy is optimally guided by a specific microbiological diagnosis.
Insights
Cancer patients face infection risks primarily due to granulocytopenia (low white blood cell counts), compromised physical barriers, and immunosuppression. Prompt antimicrobial or antifungal therapy is crucial for neutropenic and immunosuppressed individuals.
Area of Science:
- Oncology
- Infectious Diseases
- Immunology
Background:
- Granulocytopenia is a primary risk factor for bacterial infections in cancer patients, often caused by Gram-negative organisms from endogenous flora.
- Altered anatomical barriers, due to cancer treatments and devices, also increase infection susceptibility.
- Immunosuppression, particularly in hematologic malignancies, predisposes patients to a wide range of bacterial, fungal, viral, and parasitic infections.
Purpose of the Study:
- To elucidate the key factors predisposing cancer patients to infections.
- To identify common pathogens associated with each predisposing factor.
- To highlight the importance of timely and appropriate antimicrobial therapy.
Main Methods:
- Review of established knowledge on infection risks in cancer patients.
- Categorization of predisposing factors: granulocytopenia, altered anatomical barriers, and immunosuppression.
- Identification of associated pathogens for each category.
Main Results:
- Gram-negative bacteria are common in granulocytopenic patients; fungi like Candida and Aspergillus are also prevalent.
- Similar pathogens affect patients with altered anatomical barriers, which are often caused by granulocytopenia.
- Immunosuppressed patients are susceptible to diverse pathogens including Listeria, Salmonella, Mycobacterium, viruses, and Pneumocystis.
Conclusions:
- Prompt empirical antimicrobial or antifungal therapy is recommended for neutropenic patients before diagnosis.
- For immunosuppressed patients, treatment guided by specific microbiological diagnosis is optimal.
- Understanding these risk factors and pathogens is critical for managing infections in cancer care.