Antibiotic resistance among Gram-negative bacteria in bloodstream infections in Shiraz, Iran (2012-2023)

Regular monitoring and conducting surveillance studies are necessary to control and treat antibiotic-resistant infections on a global scale. The present study aimed to perform a time-trend analysis of the distribution and antibiotic resistance of Gram-negative bacteria (GNB) isolated from bloodstream infections over 12 years in Iran. Throughout a 12-year duration, from January 2012 until the end of December 2023, data from the blood specimens of patients were obtained from three university teaching hospitals in Shiraz, Iran. Antimicrobial susceptibility profiles of GNB were determined using the Kirby-Bauer disk diffusion method (DDM) on Mueller-Hinton agar (MHA) media. A total of 391,762 blood samples were obtained from patients. Among these, 40,397 (10.31%) were confirmed to be positive for GNB. The frequency of GNB was higher among patients aged over 50 years. The highest number of GNB was isolated from the emergency (50.54%) ward. Escherichia coli with 42.65%, and Klebsiella spp. with 17.02% frequently isolated from blood specimens. CAZ was the most effective antimicrobial agent against Pseudomonas aeruginosa (7.16%), Acinetobacter spp. (1.18%), E. coli and Klebsiella spp. (1.17%). The trends observed in antibiotic resistance among GNB from 2012 to 2023 indicate a reduction in resistance levels for certain antibiotics: SXT decreased from 75.41 to 58.85%, TET from 82.39 to 25%, CAZ from 85.21 to 42.86%, AMP from 92.14 to 62.5%, and FEP from 100 to 67.96%. Results demonstrate a general downward trend in antibiotic resistance among GNB. However, variation in antibiotic resistance profile among GNB suggested that follow-up antimicrobial resistance (AMR) programs, along with constant screening and developing antimicrobial stewardship programs in Shiraz, are necessary.