Emergence of hypervirulent ESBL-producing Klebsiella pneumoniae with high virulence and antibiotic resistance in Southwest of Iran

This study investigates the prevalence of hypervirulent Klebsiella pneumoniae (hvKp) in clinical isolates, emphasizing hypermucoviscosity, virulence-related genes, capsular serotype, and extended-spectrum β-lactamase (ESBL) genes. During a 12-month surveillance study, a total of 144 K. pneumoniae isolates were obtained from various clinical specimens of patients referred to teaching hospitals in Yasuj, Iran. Antimicrobial susceptibility testing was performed for various classes of antibiotics using the disk diffusion method. Detection of virulence genes (rmpA, rmpA2, iucA, peg-344), capsular serotype (K1, K2), and ESBLs (blaSHV, blaTEM, blaCTX-M) was conducted using polymerase chain reaction (PCR). A total of 31 isolates (21.5%) were identified as hvKp, while 113 (78.5%) were classified as cKp. Among hvKp, iucA (100%) and rmpA2 (77.4%) were the most prevalent virulence genes, while among all K. pneumoniae isolates, rmpA, rmpA2, and iucA were detected in 11.1%, 16.7% and 21.5%, respectively. Capsular serotype K2 was found in 21.5% of isolates and 9.7% of hvKp, while serotype K1 was not detected in any isolate. ESBL production was observed in 22.2% of isolates and 22.6% of hvKp. Genotypically, blaSHV, blaCTX-M, and blaTEM were identified in 88.9%, 69.4%, and 58.3% of isolates and in 90.3%, 100%, and 74.2% of hvKp, respectively. The highest resistance to third-generation cephalosporins, including cefotaxime, ceftazidime, and ceftriaxone, was observed among all 144 K. pneumoniae isolates as well as hypervirulent strains, whereas gentamicin showed the highest susceptibility. Multidrug-resistant (MDR), extensively drug-resistant (XDR), and carbapenem-resistant K. pneumoniae (CRKP) were identified in 72.9%, 59.7%, and 79.2% of isolates, respectively. In comparison, all these resistance phenotypes were observed in 90.3% of hvKp strains. These findings demonstrate strong coexistence of virulence and resistance in K. pneumoniae, particularly among hvKp. The high prevalence of virulence factors such as iucA (100%) and rmpA2 (77.4%), with MDR, XDR, and CRKP phenotypes detected in 90.3% of hvKp isolates, indicates a critical situation and emphasizes the need for accurate molecular diagnosis, continuous monitoring, and rational antibiotic use.