Phenotypic and Molecular Detection of Carbapenemase-Producing Klebsiella pneumoniae Isolated from Patients Admitted to Teaching Hospitals in Shiraz, Iran

Background: Carbapenem-resistant Klebsiella pneumoniae (Cr-KPN) poses a significant global public health challenge. Objectives: This study aimed to investigate the prevalence and expression levels of carbapenemase-encoding genes in Cr-KPN isolated from patients admitted to teaching hospitals in Shiraz, Iran. Methods: A total of 671 distinct clinical samples were collected from two teaching hospitals in Shiraz. Initial identification and final confirmation of K. pneumoniae isolates were carried out using conventional biochemical tests and PCR assays, respectively. The detection of carbapenemase-producing K. pneumoniae, both phenotypically and genotypically, was performed through modified carbapenem inactivation methods (mCIM) and multiplex PCR assays. Real-time PCR was utilized to assess the expression levels of carbapenemase-encoding genes. Results: The overall frequency of K. pneumoniae strains was 14.9% (n = 100/671). mCIM indicated that 26% of K. pneumoniae isolates exhibited carbapenemase production. Furthermore, 24% and 17% of K. pneumoniae isolates demonstrated resistance to imipenem and meropenem, respectively. The blaIMI/IMP gene was detected in 91% of the isolates. Among imipenem-resistant isolates, 62.5% tested positive for the blaOXA-48 gene. Additionally, 29.4%, 76.5%, and 11.8% of meropenem-resistant isolates were positive for the blaKPC, blaOXA-48, and blaNDM genes, respectively. Real-time PCR analysis revealed increased expression levels of blaKPC (1.66-fold), blaOXA-48 (7.30-fold), blaNDM (4.22-fold), and blaIMI/NMC (2.39-fold) genes in resistant isolates when exposed to imipenem. Conclusions: These findings underscore the significance of establishing active surveillance networks to monitor and track the dissemination of carbapenemase-producing K. pneumoniae, which presents a global public health threat.