Objective To analyze the distribution, antimicrobial resistance trends, and clinical characteristics of Gram-negative bacteria in patients with bloodstream infections (BSIs) in a hospital in Yiwu area.

Methods Data on Gram-negative bacterial strains isolated from positive blood cultures at Yiwu Central Hospital between January 2019 and December 2024 were retrospectively collected and analyzed using WHONET 5.6 and SPSS 26.0. Inter-year differences were compared using the chi-square test, and annual trends were assessed using the Cochran-Armitage trend test. The Benjamini-Hochberg procedure was applied for multiple comparison correction.

Results A total of 1,478 Gram-negative strains were isolated. The top five species were Escherichia coli (50.81%), Klebsiella pneumoniae subsp. pneumoniae (24.22%), Pseudomonas aeruginosa (7.10%), Acinetobacter baumannii (3.86%), and Enterobacter cloacae (2.64%). The detection rate and proportion of E. coli increased rapidly year by year, while the proportion of K. pneumoniae subsp. pneumoniae began to decline from 2023. Regarding departmental distribution, the top five departments were Gastrointestinal Hernia Surgery (21.31%), Hepatobiliary-Pancreatic Surgery (18.61%), the Intensive Care Unit (11.50%), Vascular Surgery (4.26%), and the Emergency Intensive Care Unit (3.45%). The proportion of isolates from surgical departments, particularly Gastrointestinal Hernia Surgery, rose markedly. Additionally, the detection number and proportion among young and middle-aged patients (21~50 years) increased annually. The detection rates of extended-spectrum β-lactamase (ESBL)-producing E. coli, ESBL-positive K. pneumoniae subsp. pneumoniae, carbapenem-resistant E. coli, carbapenem-resistant K. pneumoniae, carbapenem-resistant P. aeruginosa, and carbapenem-resistant A. baumannii were 42.21%, 16.39%, 1.33%, 17.21%, 15.24%, and 59.65%, respectively. Trend analysis revealed that K. pneumoniae subsp. pneumoniae exhibited significant annual decreases in resistance rates to all tested antimicrobials. For E. coli, only the cefoperazone-sulbactam resistance rate showed a significant downward trend, while it remained highly susceptible to carbapenems, amikacin, and tigecycline (resistance rates <2% in most years). P. aeruginosa showed significant decreasing trends in resistance to cefoperazone-sulbactam, ceftazidime, cefepime, carbapenems, and fluoroquinolones. No statistically significant resistance trends were observed for A. baumannii, which remained highly susceptible only to polymyxin B and tigecycline.

Conclusion E. coli and K. pneumoniae subsp. pneumoniae were the predominant Gram-negative pathogens causing BSIs in this hospital. The proportion of isolates from surgical departments represented by Gastrointestinal and Hernia Surgery increased rapidly, accompanied by an elevated proportion of middle-aged and young adult patients aged 20~50 years. Overall antimicrobial resistance rates remained stable, with decreasing trends detected for certain species. Continuous antimicrobial resistance surveillance, routine etiological testing before antimicrobial administration, and rational drug selection should be implemented to curb bacterial resistance.

1. KadriSS, LaiYL, WarnerS, et al. Inappropriate empirical antibiotic therapy for bloodstream infections based on discordant in-vitro susceptibilities[J]. Lancet Infect Dis, 2021, 21(2): 241-251. DOI: 10.1016/S1473-3099(20)30477-1.

2. EvansL, RhodesA, AlhazzaniW, et al. Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021[J]. Crit Care Med, 2021, 49(11): e1063-e1143. DOI: 10.1097/CCM.0000000000005337.

3. ZhaoS, WuY, DaiZ, et al. Risk factors for antibiotic resistance and mortality in patients with bloodstream infection of Escherichia coli[J]. Eur J Clin Microbiol Infect Dis, 2022, 41(5): 713-721. DOI: 10.1007/s10096-022-04423-6.

4. WatersJ, ShorrAF. Bloodstream infection and gram-negative resistance: the role for newer antibiotics[J]. Antibiotics (Basel), 2023, 12(6): 977. DOI: 10.3390/antibiotics12060977.

5. P N, KumarD, MeenaDS, et al. Difficult-to-treat resistant gram-negative blood stream infections[J]. Indian J Med Microbiol, 2023, 44: 100364. DOI: 10.1016/j.ijmmb.2023.02.007.

6. KadriSS, LaiYLE, RicottaEE, et al. External validation of difficult-to-treat resistance prevalence and mortality risk in gram-negative bloodstream infection[J]. Open Forum Infect Dis, 2019, 6(4): ofz110. DOI: 10.1093/ofid/ofz110.

7. CaoW, ShenL, ZhaoJ, et al. Microbial epidemiology and antimicrobial resistance of bloodstream infections in hospitalized patients during 2019-2023 in Xiangyang, China[J]. Can J Infect Dis Med Microbiol, 2025, 2025: 9969709. DOI: 10.1155/cjid/9969709.

8. JiangZQ, WangSD, FengDD, et al. Epidemiological risk factors for nosocomial bloodstream infections: a four-year retrospective study in China[J]. J Crit Care, 2019, 52: 92-96. DOI: 10.1016/j.jcrc.2019.04.019.

9. LiuZ, ZhangL, ZouJ. Epidemiological characteristics and antimicrobial resistance of pathogens isolated from blood cultures in southern Jiangxi, China, 2020-2024[J]. Front Cell Infect Microbiol, 2026, 15: 1727877. DOI: 10.3389/fcimb.2025.1727877.

10. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing. 34th ed. CLSI supplement M100. Wayne, PA: CLSI; 2024.

11. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk Susceptibility Tests. 14th ed. CLSI standard M02; Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically. 12th ed. CLSI standard M07. Wayne, PA: CLSI; 2024.

12. 中华人民共和国国家卫生健康委员会. 医院感染监测标准: WS/T 312—2023[S]. 北京: 国家卫生健康委员会, 2023.

13. VostalAC, GranceM, PowersJH3rd, et al. Demographics, epidemiology, mortality and difficult-to-treat resistance patterns of bacterial bloodstream infections[J]. BMJ Open, 2025, 15(3): e094861. DOI: 10.1136/bmjopen-2024-094861.

14. 郭燕, 丁丽, 胡付品, 等. 2024年CHINET中国细菌耐药监测[J].中国感染与化疗杂志, 2025, 25(6): 597-607.GuoY, DingL, HuFP, et al. Antimicrobial resistance profile of clinical isolates in hospitals across China:report from the CHINET Antimicrobial Resistance Surveillance Program,2024[J]. Chinese Journal of Infection and Chemotherapy, 2025, 25(6): 597-607. DOI: 10.16718/j.1009-7708.2025.06.002.

15. CuiY, YiC, ZhangC, et al. Risk factors for bloodstream infection among patients admitted to an intensive care unit of a tertiary hospital of Shanghai, China[J]. Sci Rep, 2024, 14: 12943. DOI: 10.1038/s41598-024-63594-8.

16. 杨思恒, 张学武, 胡国启, 等. 2019—2022年我院血流感染病原菌分布及耐药性分析[J]. 内科理论与实践, 2023, 18(6): 424-430.YangSH, ZhangXW, HuGQ, et al. Analysis of distribution and drug resistance of pathogenic bacteria of bloodstream infection in a tertiary hospital from 2019 to 2022[J]. Journal of Internal Medicine Concepts & Practice,  2023, 18(6): 424-430. DOI: 10.16138/j.1673-6087.2023.06.009.

17. ZhangY, WangH, LiY, et al. Drug susceptibility and molecular epidemiology of Escherichia coli in bloodstream infections in Shanxi, China[J]. PeerJ, 2021, 9: e12371. DOI: 10.7717/peerj.12371.

18. YanM, ZhengB, LiY, et al. Antimicrobial susceptibility trends among gram-Negative bacilli causing bloodstream infections (CARST 2011-2020)[J]. Infect Drug Resist, 2022, 15: 2325-2337. DOI: 10.2147/IDR.S358788.

19. TammaPD, HeilEL, JustoJA, et al. IDSA 2024 guidance on the treatment of antimicrobial-resistant gram-negative infections[J/OL]. Clin Infect Dis, 2024: ciae403. DOI: 10.1093/cid/ciae403.