Background: Healthcare-associated infections are a major cause of mortality worldwide, especially in intensive care units (ICUs) where severely ill patients are in a limited physical space. Aims: To investigate the incidence rate, microbial etiology, antimicrobial resistance profile, and mortality rate of healthcare-associated infections in ICUs. Methods: This observational study retrospectively reviewed the medical records of 1722 ICU patients with confirmed healthcare-associated infections at hospitals affiliated with Mashhad University of Medical Sciences in 2017–2019. The patient data collected included age, sex, comorbidities, device use, causative agents, infection type, antimicrobial resistance profile, length of stay, and mortality. Results: In total, 4077 pathogens were isolated, yielding a healthcare-associated infection incidence rate of 22.1%. The most common microorganisms were Acinetobacter spp. (25.0%), Klebsiella spp. (15.1%), Staphylococcus spp. (14.0%), and Candida spp.(12.3%). Ventilator-associated events (39.5%), urinary tract infections (22.7%), and bloodstream infections (14.8%) were the main types of infection. Comorbidities, skin and soft tissue infections, and infections with Acinetobacter spp., Klebsiella spp., Pseudomonas spp., and Candida spp. were significantly associated with higher mortality among ICU patients. Gram-positive bacteria were most resistant to ciprofloxacin (49.2%), clindamycin (38.0%), and erythromycin (37.1%). Gram-negative bacteria were most resistant to ceftazidime (71.0%), ciprofloxacin (65.2%), and cefotaxime (60.5%). The overall mortality rate was 45.2%. Conclusion: Healthcare-associated infections in nearly half of ICU patients were fatal, especially when caused by Acinetobacter spp., Klebsiella spp., Pseudomonas spp., or Candida spp. Therefore, effective strategies must be implemented to combat antibiotic-resistant bacteria, along with stricter adherence to infection control programmes.

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