Transmission of infectious agents in healthcare settings: a systematic review of healthcare-associated infections

OBJECTIVES: This study aimed to systematically analyse original research publications to provide a comprehensive assessment of the transmission chain of healthcare-associated infections (HAIs). The review focused on identifying transmission routes, sources of pathogen detection, and the predominant microorganisms detected in healthcare environments. METHODS: A systematic review was performed following PRISMA methodology. Relevant studies were searched in PubMed and Scopus databases using predefined keywords. RESULTS: Forty-four original studies published in English between January 2015 and July 2025 were included. Indirect transmission was reported in 37 (84.1%) studies, while 27 (61.4%) studies identified it as the sole transmission route. Fomites were reported as the sole source of pathogen detection in 30 (68.2%) studies. Among studies investigating fomites or environmental contamination, stethoscopes were the leading contaminated item (n = 5, 13.5%). Among detected microorganisms, Gram-negative bacilli (n = 94, 51.1%) and Gram-positive cocci (n = 76, 41.3%) prevailed. The dominant bacterial genus was Staphylococcus spp. (n = 55, 29.9%), whereas Staphylococcus aureus represented the leading species (n = 25, 13.6%), followed by Klebsiella pneumoniae (n = 12, 6.5%) and Escherichia coli (n = 11, 6.0%). Multidrug-resistant strains, including methicillin-resistant Staphylococcus aureus (n = 11, 6.0%) were also observed. CONCLUSION: Indirect transmission through contaminated fomites represented the predominant transmission pathway, including medical devices such as stethoscopes. Staphylococcus aureus was among the most frequently detected microorganisms, while multidrug-resistant organisms were also reported. These findings emphasize the importance of infection prevention and control measures in healthcare settings.