A Scoring System for Pneumocystis Pneumonia Based on Clinical Symptoms and Laboratory Findings in a Rat Model

Background and Objective: Effective clinical prediction of Pneumocystis carinii pneumonia (PCP) is quite critical, especially in high risk groups. Different scoring systems have been reported to help the physicians before patients entering the acute stage. This research study was conducted to evaluate the possibility of grading the disease based on clinical symptoms and laboratory findings of pneumocystosis in a rat model. Materials and Methods: Twenty female rats (two-month age, a weight of 150-200 g, Sprague- Dawley strain) were stimulated artificially by methyl prednizolone acetate to infect them. Changes of clinical signs and symptoms were followed up for two months. All changes were registered and graded according to defined criteria. Oral swab, broncho-alveolar lavage, and lung homogenate were collected before injection and at weeks 2, 3, 4, 5, 6 and 7 from test and control groups. All specimens were tested by Giemsa and Gomori’s metenamin silver staining and PCR methods. Results: Three stages were determined for infection of PCP on the basis of clinical symptoms and laboratory findings. Conclusion: With regard to the correlation between staining and PCR results and clinical symptoms in the studied groups, those animal models under suppressed immune system are in a healthy condition up to 10 days after injection, but those from days 11-20, 21-30, and over 30 are in phases 1, 2 and 3 respectively.