Pathogen distribution and risk factors for nosocomial infections in the operating room: A case-control study

Nosocomial infections remain a leading cause of postoperative morbidity and prolonged hospitalization, and they contribute to antimicrobial exposure and resistance selection. A retrospective case-control study was conducted among consecutive surgical patients treated in the operating room between January and December 2025; the sample comprised all eligible infected cases during the predefined study period and contemporaneous controls selected at a 1:1 ratio. Cases were patients who developed a postoperative nosocomial infection adjudicated using the Centers for Disease Control and Prevention and National Healthcare Safety Network definitions; controls were contemporaneous surgical patients without a nosocomial infection. Data were extracted from electronic clinical, anesthesia, operating room, laboratory, and microbiology systems. Group comparisons used Welch's t test, Mann-Whitney U test, chi-square test, or Fisher's exact test. Risk factors were assessed using univariate and multivariable logistic regression, with odds ratios and 95% confidence intervals. Culture positivity was identified in 44 of 56 cases (78.6%), with the highest specimen-level yield from operative-site and respiratory samples. Among 56 non-duplicate isolates, Gram-negative bacteria predominated (58.9%), followed by Gram-positive bacteria (32.1%) and fungi (8.9%); pathogen profiles differed by syndrome, with pneumonia largely caused by Gram-negative bacteria. In multivariable analysis, chronic obstructive pulmonary disease, longer preoperative length of stay, preoperative urinary catheterization, lower serum albumin, prolonged operative time, and intraoperative hypothermia were independently associated with infection risk. Operating room-associated nosocomial infections demonstrated syndrome-specific pathogen distributions and were linked to both host vulnerability and modifiable perioperative exposures, supporting integrated prevention and predictive strategies.