Prevalence and Antimicrobial Resistance Trends among Lower Respiratory Tract Pathogens in Crete, Greece, 2017-2022.

Background: Lower respiratory tract infections (LRTIs) are the most common infections in humans accounting for significant morbidity and mortality. Management of LRTIs is complicated due to increasing antimicrobial resistance. This study investigated the prevalence and trends of antimicrobial resistance for bacteria isolated from respiratory samples of patients with LRTIs.

Materials And Methods: Sputum and bronchial washings were collected from patients of all ages hospitalized with LRTIs and were analyzed by the microbiological laboratory in the University Hospital of Heraklion, Crete, Greece, from January 2017 to December 2022. Identification of the bacterial isolates was performed by matrix-assisted laser desorption ionization-time of flight mass spectrometry and antimicrobial susceptibility testing by Vitek 2 system.

Results: A total of 4,008 strains were isolated from 3,427 respiratory samples. was the most frequently isolated pathogen (23.1%), followed by (20.0%), (10.6%) and (6.8%). The isolation rate of significantly increased during the study period, while there were lower increases in the isolation rates of , and and were more prevalent during summer, was more common during autumn, while for higher incidence was noted during winter. exhibited high resistance rates (≥90.0%) to most of the antimicrobial agents tested, and extremely high multidrug-resistance (91.0%). showed the lowest rate of resistance for colistin (1.4%). Among β-lactams, resistance rates to piperacillin/tazobactam, ceftazidime, cefepime, imipenem and meropenem were 26.2%, 27%, 25.8%, 29.2% and 29.9%, respectively. A total of 162 (68.1%) meropenem-resistant were simultaneously resistant to ceftazidime and piperacillin/tazobactam. Regarding , high rates of resistance were observed for the third and fourth generation cephalosporins, namely cefotaxime, ceftriaxone, ceftazidime, and cefepime and the carbapenems, imipenem and meropenem ranging from 46.2% to 53.8%. Carbapenem-resistance was detected among 46.2% of the isolates. Among the 126 carbapenem-resistant isolates, 83 (65.9%), 30 (23.8%), 9 (7.2%), and 4 (4.2%) were positive for carbapenemase, New Delhi Metallo-β-lactamase, Verona Integron-Mediated Metallo-β-lactamase and OXA-48 carbapenemase, respectively. Of the total number of , 37.2% were methicillin resistant. Low rates of resistance were detected in trimethoprim/sulfamethoxazole (3.3%), gentamicin (2.8%), and rifampicin (0.9%). All isolates were susceptible to linezolid, daptomycin, tigecycline, teicoplanin, and vancomycin.

Conclusion: Regularly updated surveillance of local microbial prevalence and monitoring of antimicrobial resistance patterns is of paramount importance to guide the empiric treatment of LRTIs.