Bacteremia During the First Year After Solid Organ Transplantation: An Epidemiological Update

Abstract

Background: There are limited contemporary data on the epidemiology and outcomes of bacteremia in solid organ transplant recipients (SOTr).

Methods: Using the Swiss Transplant Cohort Study registry from 2008 to 2019, we performed a retrospective nested multicenter cohort study to describe the epidemiology of bacteremia in SOTr during the first year post-transplant.

Results: Of 4383 patients, 415 (9.5%) with 557 cases of bacteremia due to 627 pathogens were identified. One-year incidence was 9.5%, 12.8%, 11.4%, 9.8%, 8.3%, and 5.9% for all, heart, liver, lung, kidney, and kidney-pancreas SOTr, respectively (P = .003). Incidence decreased during the study period (hazard ratio, 0.66; P < .001). One-year incidence due to gram-negative bacilli (GNB), gram-positive cocci (GPC), and gram-positive bacilli (GPB) was 5.62%, 2.81%, and 0.23%, respectively. Seven (of 28, 25%) Staphylococcus aureus isolates were methicillin-resistant, 2/67 (3%) enterococci were vancomycin-resistant, and 32/250 (12.8%) GNB produced extended-spectrum beta-lactamases. Risk factors for bacteremia within 1 year post-transplant included age, diabetes, cardiopulmonary diseases, surgical/medical post-transplant complications, rejection, and fungal infections. Predictors for bacteremia during the first 30 days post-transplant included surgical post-transplant complications, rejection, deceased donor, and liver and lung transplantation. Transplantation in 2014-2019, CMV donor-negative/recipient-negative serology, and cotrimoxazole Pneumocystis prophylaxis were protective against bacteremia. Thirty-day mortality in SOTr with bacteremia was 3% and did not differ by SOT type.

Conclusions: Almost 1/10 SOTr may develop bacteremia during the first year post-transplant associated with low mortality. Lower bacteremia rates have been observed since 2014 and in patients receiving cotrimoxazole prophylaxis. Variabilities in incidence, timing, and pathogen of bacteremia across different SOT types may be used to tailor prophylactic and clinical approaches.

Keywords: bacteremia; bloodstream infection; clinical outcomes; epidemiology; risk factors; solid organ transplant; timing.

Figure 1.

Study flowchart. Abbreviations: BSI, bloodstream infection; ICF, informed consent form; ID, infectious disease; SOT, solid organ transplant.

Figure 2.

Estimated cumulative incidence of bacteremia during the first year post-transplant: (A) in the overall cohort; (B) per transplant type; (C) based on the number of pathogens identified: mono- vs polymicrobial bacteremia; and (D) based on the type of pathogen for monomicrobial bacteremia events (gram-positive cocci vs gram-negative bacteria vs gram-positive bacteria). The temporal tendency of bacteremia during the study period is presented in (E), showing the incidence proportions of patients infected during the first year after transplant date by transplant year via locally weighted scatterplot smoothing with span 1.5, a nonparametric local regression approach. Abbreviation: BSI, bloodstream infection.

Figure 3.

Infection density by pathogens causing bacteremia during the first year after a solid organ transplant overall and by transplant type.

Figure 4.

A, Distribution of MDR pathogens through the study period. MDR pathogens included MDR and ESBL-producing GNB, MRSA, and VRE. MDR GNB definitions were based on previously published guidelines [14]. Results are presented as stacked bar charts including the proportions of MDR pathogens, non-MDR pathogens, and pathogens with unknown resistance patterns. B, Distribution of resistant pathogens through the study period, including MDR and ESBL GNB, MRSA, and VRE. MDR GNB definitions were based on previously published guidelines [14]. Results are presented as the proportion of resistant pathogens over the number of pathogens with known antibiotic susceptibilities per year. Data on bacterial drug resistance were collected after 2012; hence results are presented between 2012 and 2019. Antimicrobial resistance patterns were not available for all pathogens between 2012 and 2019. Abbreviations: BSI, bloodstream infection; ESBL, extended-spectrum beta-lactamase; MDR, multidrug-resistant; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant enterococci.

Figure 5.

All-cause 30-day mortality of SOT recipients with bacteremia: (A) overall, (B) by SOT type, (C) number of pathogens identified (mono- vs polymicrobial). Abbreviation: SOT, solid organ transplant.