To analyze microbial specimen submissions, distribution of isolated pathogens and their antimicrobial resistance among heart transplant patients and provide evidence-based guidance for infection prevention and antimicrobial therapy in these patients.

A retrospective analysis was performed on various microbial specimens collected from 508 heart transplant recipients admitted to Fuwai Hospital, Chinese Academy of Medical Sciences, from January 2019 to December 2024. A total of 1 322 primary isolates were initially obtained. After excluding duplicate isolates from the same anatomical site of an individual recipient, 517 nonduplicate isolates were included for analysis. WHONET 5.6 software was used to analyze invitro antimicrobial susceptibility test results in accordance with the Clinical and Laboratory Standards Institute (CLSI) M100S34 (2024).

Among the 517 isolates, 483 were bacteria and 34 were fungi. Gramnegative bacteria predominated, accounting for 73.3% (379/517). The top five isolated pathogens were Klebsiella pneumoniae (32.1%, 166/517), Escherichia coli (9.9%, 51/517), Pseudomonas aeruginosa (8.1%, 42/517), Enterococcus faecium (6.4%, 33/517), and Enterobacter cloacae (5.2%, 27/517). Specimenbased distribution showed respiratory specimens constituted the largest proportion (60.8%), followed by urine specimens (17.3%), blood specimens (7.1%), and secretion specimens (5.5%). The detection rates of carbapenemresistant Klebsiella pneumoniae (CRKP), carbapenemresistant Pseudomonas aeruginosa, and methicillinresistant Staphylococcus aureus were 10.8%, 7.1% and 6.7%, respectively. No vancomycinresistant enterococci were detected.

Respiratory specimens dominate the submitted samples from heart transplant recipients. Gramnegative bacilli are the predominant isolates. Overall antimicrobial resistance rates are lower than the national average resistance level in China. Nevertheless, the detection rate of CRKP shows an upward trend, which warrants close clinical attention.