Differences and trends in pathogens between ventilator-associated pneumonia and non-ventilator-associated pneumonia: data from 61 hospitals in Suzhou, China, 2020–2024

Objective

To investigate the differences in pathogenic bacterial profiles between ventilator-associated pneumonia (VAP) and non-ventilator-associated hospital-acquired pneumonia (NV-HAP) and to provide data to support clinical infection prevention and control.

Design

A retrospective observational study using surveillance data, accompanied by a statistical analysis of pathogen-related variables between the two study cohorts.

Setting

Sixty-one secondary and tertiary healthcare institutions in a single city. Data were extracted from the city’s regional healthcare-associated infection surveillance platforms.

Participants

Inpatients (≥18 years old) diagnosed with confirmed hospital-acquired pneumonia (HAP), including VAP and NV-HAP, at the aforementioned 61 healthcare institutions during the study period. Patients with community-acquired pneumonia (CAP) were excluded.

Outcome measures

(1) Pathogen distribution in patients with VAP and NV-HAP; (2) temporal trends in pathogen isolation rates (January 2020–December 2024) in both groups; (3) antimicrobial resistance

characteristics of major pathogens, including detection/composition ratios of key multidrug-resistant organisms (MDROs): carbapenem-resistant Acinetobacter baumannii (CRAB), methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Escherichia coli (CREC), carbapenem-resistant Klebsiella pneumoniae (CRKP) and carbapenem-resistant Pseudomonas aeruginosa (CRPA); (4) susceptibility of major pathogens to antimicrobials.

Results

Pathogen distribution differed between the two groups, with Gram-negative bacteria being predominant in both groups (73.72% vs 80.98%). Among patients with NV-HAP, the isolation rates of K. pneumoniae , Burkholderia cepacia and Candida albicans showed a decreasing trend, whereas A. baumannii exhibited a slow increase. In patients with VAP, the isolation rates of K. pneumoniae and B. cepacia decreased, whereas Stenotrophomonas maltophilia increased. The proportion of drug-resistant bacteria was higher in patients with VAP than in those with NV-HAP (28.12% vs 19.74%). CRAB showed higher detection and composition ratios in the former group (77.37% and 48.05%, respectively). The MRSA detection rates were approximately 50% in both groups, whereas the CREC detection rate was below 6%. CRPA detection increased in patients with VAP, whereas CRKP and CRPA detection rates decreased in patients with NV-HAP. The antimicrobial resistance profiles of major pathogens were similar between the two groups. K. pneumoniae and E. coli remained susceptible to most antimicrobials, whereas CRKP and CREC were susceptible to only a few agents, such as tigecycline and polymyxin B. A. baumannii exhibited high resistance rates, with both A. baumannii and CRAB being susceptible only to tigecycline, minocycline and polymyxin B. P. aeruginosa and CRPA were largely susceptible to most antimicrobials. S. maltophilia exhibited a ceftazidime resistance rate exceeding 36%, and B. cepacia exhibited ticarcillin/clavulanate and cefoperazone/sulbactam resistance rates exceeding 67%. The resistance rates of S. aureus and MRSA to penicillin, erythromycin and clindamycin ranged from 41.83% to 98.72%. The resistance rates of C. albicans to commonly used antifungal agents were below 8%.

Conclusion

The two groups differed in the distribution and antimicrobial resistance of the pathogens and MDROs, and these profiles fluctuated over time. Patients with VAP have a higher percentage of drug-resistant bacteria, requiring special attention to CRAB and CRPA. Local microbiological epidemiological surveillance should be strengthened to improve infection prevention, control strategies and guide empirical antibiotic therapy.