Epidemiological profile of causative agents in nosocomial pneumonia: a four-year multicenter surveillance study from Georgia (2020-2023).

BACKGROUND: Nosocomial pneumonia (NP), including hospital-acquired (HAP) and ventilator-associated pneumonia (VAP), remains a leading cause of morbidity, mortality, and antimicrobial resistance worldwide. Data from Eastern Europe and the Caucasus are scarce, limiting region-specific infection control strategies.

METHODS: We conducted a prospective multicenter surveillance study across five tertiary hospitals in Georgia from May 2020 to December 2023. A total of 484 respiratory specimens were obtained from 397 adult patients with microbiologically confirmed NP. Pathogen identification was performed using culture and MALDI-TOF MS, with antimicrobial susceptibility testing according to CLSI guidelines. PCR assays detected major resistance genes. Epidemiological, molecular, and clinical outcomes were evaluated, including temporal trends and comparisons between ICU and non-ICU patients.

RESULTS: Gram-negative bacteria predominated (71.7%), with Pseudomonas aeruginosa (41.9%) as the leading pathogen, followed by Staphylococcus aureus (21.3%), Acinetobacter baumannii (13.4%), Klebsiella pneumoniae (13.0%), and Streptococcus pneumoniae (9.3%). Multidrug resistance (MDR) was identified in 80% of isolates, extensively drug-resistant (XDR) phenotypes in 18.4%, and pandrug-resistant (PDR) phenotypes in 1.4%. ESBL prevalence increased from 48.3% in 2020 to 79.8% in 2023 (p < 0.001), carbapenemase expression doubled from 15.0% to 30.2% (p < 0.01), and colistin resistance rose from 2.5% to 8.5% (p < 0.05). ICU isolates showed significantly higher MDR and XDR rates than those from non-ICU settings (p < 0.001). Thirty-day mortality correlated with resistance phenotype, ranging from 18.2% in susceptible infections to 71.4% in PDR cases.

CONCLUSIONS: This four-year study shows high and increasing antimicrobial resistance among NP pathogens in Georgia, especially in ICU settings. The rise in ESBL, carbapenemase, and colistin resistance highlights the need to strengthen antimicrobial stewardship, infection prevention, and genomic surveillance to control the spread of high-risk strains and improve patient outcomes in resource-limited settings.