Background: Pneumococcal disease is still considered a global problem. With the introduction of pneumococcal conjugate vaccines (PCVs) serotype epidemiology changed, but antimicrobial resistance persists constituting a serious problem. The current study aimed to determine the serotype distribution and the antimicrobial susceptibility of recent Streptococcus pneumoniae isolates, following implementation of the 13-valent conjugate vaccine (PCV13). Materials and Methods: From January 2017 to December 2022 we evaluated 116 nonduplicate S. pneumoniae isolates collected from adult patients (21 - 98 years) cared for in the University Hospital of Heraklion, Crete, Greece. Pneumococcal isolates were serotyped by the Quellung reaction, and antimicrobial susceptibility testing was performed using E-test. Multidrug resistance (MDR) was defined as non-susceptibility to at least one agent in ≥3 classes of antibiotics. Results: Among the 116 isolates, 31% were recognized as invasive pneumococcal strains, while 69% were noninvasive. The isolates tested belonged to 25 different serotypes. The most prevalent serotypes were 11A (10.3%), and 35B (10.3%), followed by 3 (9.5%), 15A (7.8%), 25F (6.9%), 19A (5.3%), 35F (5.3%), and others (44.6%).The coverage rates of PCV13 and the pneumococcal polysaccharide vaccine (PPSV23) were 26.7% and 57.8%, respectively. PCV13 and PPSV23 serotypes decreased between 2017 - 2019 and 2020 - 2022, with a parallel increase in the non-vaccine types. Resistance rates to erythromycin, clindamycin, trimethoprim/sulfamethoxazole, penicillin, levofloxacin, and ceftriaxone, were 40.5%, 21.6%, 13.8%, 12.1%, 3.4%, and 0%, respectively. All isolates were susceptible to vancomycin, linezolid, and daptomycin. MDR was observed among 36 (31%) S. pneumoniae isolates. Conclusion The increasing levels of resistance in S. pneumoniae in Crete, Greece, highlight the need for continuous surveillance of antimicrobial resistance and development of strategies for its reduction, including antimicrobial stewardship programs, increased pneumococcal vaccination, and development of next generation PCVs with a wider serotype coverage.

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. Acinetobacter baumannii was the most frequently isolated pathogen (23.1%), followed by Pseudomonas aeruginosa (20.0%), Staphylococcus aureus (10.6%) and Klebsiella pneumoniae (6.8%). The isolation rate of A. baumannii significantly increased during the study period, while there were lower increases in the isolation rates of P. aeruginosa, K. pneumoniae and S. aureus.A. baumannii and P. aeruginosa were more prevalent during summer, K. pneumoniae was more common during autumn, while for S. aureus higher incidence was noted during winter. A. baumannii exhibited high resistance rates (≥90.0%) to most of the antimicrobial agents tested, and extremely high multidrug-resistance (91.0%). P. aeruginosa 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 P. aeruginosa were simultaneously resistant to ceftazidime and piperacillin/ tazobactam. Regarding K. pneumoniae, 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 K. pneumoniae isolates, 83 (65.9%), 30 (23.8%), 9 (7.2%), and 4 (4.2%) were positive for Klebsiella pneumoniae carbapenemase, New Delhi Metallo-β-lactamase, Verona Integron-Mediated Metalloβ-lactamase and OXA-48 carbapenemase, respectively. Of the total number of S. aureus, 37.2% were methicillinresistant. 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.

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. Acinetobacter baumannii was the most frequently isolated pathogen (23.1%), followed by Pseudomonas aeruginosa (20.0%), Staphylococcus aureus (10.6%) and Klebsiella pneumoniae (6.8%). The isolation rate of A. baumannii significantly increased during the study period, while there were lower increases in the isolation rates of P. aeruginosa, K. pneumoniae and S. aureus.A. baumannii and P. aeruginosa were more prevalent during summer, K. pneumoniae was more common during autumn, while for S. aureus higher incidence was noted during winter. A. baumannii exhibited high resistance rates (≥90.0%) to most of the antimicrobial agents tested, and extremely high multidrug-resistance (91.0%). P. aeruginosa 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 P. aeruginosa were simultaneously resistant to ceftazidime and piperacillin/ tazobactam. Regarding K. pneumoniae, 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 K. pneumoniae isolates, 83 (65.9%), 30 (23.8%), 9 (7.2%), and 4 (4.2%) were positive for Klebsiella pneumoniae carbapenemase, New Delhi Metallo-β-lactamase, Verona Integron-Mediated Metalloβ-lactamase and OXA-48 carbapenemase, respectively. Of the total number of S. aureus, 37.2% were methicillinresistant. 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.

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. Acinetobacter baumannii was the most frequently isolated pathogen (23.1%), followed by Pseudomonas aeruginosa (20.0%), Staphylococcus aureus (10.6%) and Klebsiella pneumoniae (6.8%). The isolation rate of A. baumannii significantly increased during the study period, while there were lower increases in the isolation rates of P. aeruginosa, K. pneumoniae and S. aureus.A. baumannii and P. aeruginosa were more prevalent during summer, K. pneumoniae was more common during autumn, while for S. aureus higher incidence was noted during winter. A. baumannii exhibited high resistance rates (≥90.0%) to most of the antimicrobial agents tested, and extremely high multidrug-resistance (91.0%). P. aeruginosa 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 P. aeruginosa were simultaneously resistant to ceftazidime and piperacillin/ tazobactam. Regarding K. pneumoniae, 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 K. pneumoniae isolates, 83 (65.9%), 30 (23.8%), 9 (7.2%), and 4 (4.2%) were positive for Klebsiella pneumoniae carbapenemase, New Delhi Metallo-β-lactamase, Verona Integron-Mediated Metalloβ-lactamase and OXA-48 carbapenemase, respectively. Of the total number of S. aureus, 37.2% were methicillinresistant. 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.