Aerobic Microbiological Profile and Antimicrobial Resistance Trends in Sterile Body Fluid Infections Over Nine Years:...

Sterile body fluid infections represent life-threatening conditions requiring prompt, targeted therapy, yet long-term regional surveillance data on pathogen distribution and antimicrobial resistance (AMR) in these infections remain scarce. This study assessed nine-year trends in aerobic microbiological patterns and AMR in sterile body fluid isolates in a tertiary care hospital.

We conducted a retrospective observational study of all peritoneal, pleural, and pericardial fluid samples processed between 2016 and 2024. Only the first unique isolate per patient was included. Organisms were identified and antimicrobial susceptibility testing performed according to CLSI standards using automated and manual methods. Demographic and microbiological characteristics were summarized descriptively, while group comparisons used Chi-square, Fisher's exact test, ANOVA, or t-tests. Logistic regression evaluated year-on-year changes in non-susceptibility. Intermediate categories were included within non-susceptible interpretations. Institutional ethical approval was obtained.

A total of 764 unique isolates were analyzed, predominantly from peritoneal (84%) and pleural (16%) fluids. Gram-negative organisms accounted for 74.8% of isolates, with Escherichia coli, Klebsiella pneumoniae subspecies, and Pseudomonas aeruginosa being most frequent. ESBL-producing Enterobacterales constituted 24.1% of isolates, while 5.5% were CRE. MRSA represented 23.5% of Staphylococcus isolates. Non-fermenters demonstrated substantially higher resistance to carbapenems and aminoglycosides. Logistic regression showed significant annual declines in non-susceptibility to gentamicin, cefepime, ceftazidime, and meropenem (p < 0.05), while colistin exhibited a non-significant upward trend. Yeast isolates remained highly susceptible to azoles and echinocandins. Because anaerobic culture was performed selectively, findings primarily reflect aerobic and facultative organisms rather than the full pathogen spectrum.

In this aerobic dataset, Gram-negative pathogens predominate in sterile body fluid infections, with notable ESBL burden and emerging CRE. Despite encouraging improvements in susceptibility to several agents, AMR remains dynamic and clinically consequential. Findings highlight the need for ongoing surveillance, strengthened antimicrobial stewardship, and integration of molecular resistance testing to optimize empiric therapy. Although limited by its single-center retrospective design, these findings provide long-term aerobic surveillance data but must be interpreted within the context of limited anaerobic culture.