Distribution and antimicrobial resistance analysis of gram-negative bacilli isolated from a tertiary hospital in Central China: a 10-year retrospective study from 2012 to 2021

Abstract

Background: Gram-negative bacilli are one of the most common causes of various infections in clinical. The emergence and global spread of multi-drug resistant gram-negative bacilli has become a major challenge in the global public health field.

Methods: A total of 51,189 non-repetitive strains of gram-negative bacilli were isolated in clinical settings. The antimicrobial susceptibility testing was conducted by using the automated VITEK 2 compact system and the matched AST susceptibility test card, complemented by the disk diffusion method. The antimicrobial susceptibility results were interpreted by CLSI. Rates of MDR and XDR in Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa were investigated. Used the chi-square test to determine whether the antimicrobial resistance rates of four major gram-negative bacilli isolated from ICU and non-ICU department have statistical differences.

Results: Escherichia coli (31.4%), Klebsiella spp. (21.2%), Acinetobacter spp. (13.8%), and P. aeruginosa (11.0%) were the most frequently isolated gram-negative bacilli. Escherichia coli was the top one organism isolated from urinary tract (68.4%), bloodstream (39.9%), body fluid (33.2%), wound and pus (37%), except for respiratory tract (8.8%). Whereas Acinetobacter baumannii and K. pneumoniae were the major isolated organisms from respiratory tract. Acinetobacter baumannii showed high resistance to fluoroquinolones, β-lactam/β-lactamase inhibitor combinations class, ceftazidime, cefepime, imipenem, and meropenem, the resistance rates reached more than 70%. Ceftazidime showed a lower resistance rate to E. coli than ceftriaxone. For E. coli, fluoroquinolones showed a high resistance rate (ciprofloxacin 61.36% and levofloxacin 53.97%), whereas amikacin, carbapenems exhibited a lower resistance rate fluctuating at 2%. Acinetobacter baumannii and K. pneumoniae showed rapid increases in carbapenem resistance whereas E. coli had the lowest resistance rate and remain stable at 2%. Acinetobacter baumannii exhibited the highest rate of MDR and XDR, reaching 60-80 and 45-55%, respectively. Compared to non-ICU departments, the resistance rates of four major gram-negative bacilli in the ICU department were much higher and the differences were statistically significant (p < 0.05).

Conclusion: Amikacin, carbapenems, and piperacillin/tazobactam exhibited relatively high sensitivity, whereas fluoroquinolones showed high resistance rate whether they can be the first-line antimicrobials for empirical treatment of UTI should take more consideration. The gram-negative bacilli in ICU were more resistance than that in non-ICU. These findings are helpful for clinicians using antimicrobials reasonably.

Keywords: Central China; antimicrobial resistance; carbapenems; fluoroquinolones; gram-negative bacilli.

Figure 1

The isolation rates of the six major gram-negative bacilli between 2012 and 2021.

Figure 2

Distribution of organisms most frequently isolated from five specimen types between 2012 and 2021. n represents the total number of strains of gram-negative bacilli: (A) Respiratory tract, n = 22209; (B) Bloodstream, n = 3854; (C) Urinary tract, n = 8694; (D) Body fluid, n = 10307; (E) Wound and pus, n = 1182.

Figure 3

Comparison of 12 antibiotics resistance rates between Escherichia coli and Klebsiella pneumoniae. ^* represents the difference was statistically significant (p < 0.05).

Figure 4

Change of resistance of four major clinically isolated gram-negative bacilli to imipenem and meropenem from 2012 to 2021.