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Background: Pneumocystis jirovecii pneumonia (PJP) is a potentially fatal infection afflicting the immunocompromised population, including solid organ transplant (SOT) recipients. Several risk factors have been described; however, little is known regarding the risk of PJP in SOT recipients with posttransplant lymphoproliferative disorder (PTLD). Methods: We performed a nested case‐control study of SOT recipients diagnosed with PJP from 2000 to 2020. PJP was defined as positive microscopy or polymerase chain reaction testing with compatible symptoms and radiographic findings. Control patients were matched 2:1 by year of first transplant, first transplanted organ, transplant center, and sex. Multivariable conditional logistic regression was performed to test associations with PJP and Cox regression analyzed post‐PJP outcomes. Results: Sixty‐seven PJP cases were matched to 134 controls. The most common transplant was kidney (55.2%). Fourteen patients had a history of PTLD, 12 of whom developed PJP. After adjusting for age, acute rejection, cytomegalovirus infection, PJP prophylaxis, and lymphopenia (lymphocyte count <.5 × 109/L), PTLD was independently associated with PJP (OR 14.0, 95% CI 1.7–114.5; p =.014). Lymphopenia was also a significant association (OR 8.2, 95% CI 3.2–20.7; p <.001). PJP was associated with mortality within 90 days of diagnosis (p <.001), but not after 90 days (p =.317). PJP was also associated with 90‐day death‐censored renal allograft loss (p =.026). Conclusions: PTLD is independently associated with PJP after adjustment for recognized risk factors. This is likely influenced by PTLD‐directed chemotherapy, particularly rituximab‐containing regimens. PJP is associated with early mortality, but this effect is not persistent after 90 days. PJP prophylaxis should be considered in SOT recipients with PTLD. [ABSTRACT FROM AUTHOR]

Background: Nocardia is an opportunistic pathogen that primarily affects immunocompromised individuals, including solid organ transplant (SOT) recipients. Up to 2.65% of SOT recipients develop nocardiosis; however, few studies have examined risk factors and prophylaxis for nocardiosis. Methods: We performed a multicenter, matched nested case‐control study of adult SOT recipients with culture‐confirmed nocardiosis from 2000 through 2020. Controls were matched up to 2:1 by sex, first transplanted organ, year of transplant, transplant center, and adequate post‐transplant follow‐up. Multivariable conditional logistic regression was performed to analyze associations with nocardiosis. Cox proportional hazards regression compared 12‐month mortality between infection and uninfected patients. Results: One hundred and twenty‐three SOT recipients were matched to 245 uninfected controls. Elevated calcineurin inhibitor level, acute rejection, cytomegalovirus infection, lymphopenia, higher prednisone dose, and older age were significantly associated with nocardiosis while trimethoprim‐sulfamethoxazole prophylaxis was protective (odds ratio [OR].34; 95% confidence interval [CI].13‐.84). The effect of prophylaxis was similar, though not always statistically significant, in sensitivity analyses that only included prophylaxis dosed more than twice‐per‐week (OR.30; 95% CI.11‐.80) or restricted to years 2015‐2020 (OR.33, 95% CI.09‐1.21). Nocardiosis was associated with increased 12‐month mortality (hazard ratio 5.47; 95% confidence interval 2.42‐12.35). Conclusions: Multiple measures of immunosuppression and lack of trimethoprim‐sulfamethoxazole prophylaxis were associated with nocardiosis in SOT recipients. Effectiveness of prophylaxis may be related to trimethoprim‐sulfamethoxazole dose or frequency. Trimethoprim‐sulfamethoxazole should be preferentially utilized over alternative agents in SOT recipients with augmented immunosuppression or signs of heightened immunocompromise. [ABSTRACT FROM AUTHOR]