Coexistence of Tetracycline Resistance and Virulence Determinants in Klebsiella pneumoniae Isolated from Hospitalized Patients in Pakistan

Abstract

Background: Klebsiella pneumoniae is an important opportunistic pathogen and an increasingly difficult cause of healthcare-associated and community-acquired infections because of its capacity to accumulate antimicrobial-resistance determinants and virulence-associated traits. Data linking phenotypic resistance with specific resistance and virulence genes remain limited in many settings in Pakistan. This study investigated the antimicrobial susceptibility profile of clinical K. pneumoniae isolates and characterized selected tetracycline-resistance and virulence-associated genes among tetracycline-resistant isolates.

Methods: A total of 250 clinical specimens, comprising urine, sputum, and blood, were collected from patients with suspected urinary tract, respiratory, or bloodstream infections at Hayatabad Medical Complex. K. pneumoniae was identified by colony morphology, Gram staining, and biochemical testing. Antimicrobial susceptibility was determined by the Kirby–Bauer disc diffusion method according to CLSI M100, 35th edition (2025). Genomic DNA was extracted by phenol–chloroform extraction. PCR was used to detect tetA, tetB, and the selected virulence-associated target endr among tetracycline-resistant isolates.

Results: K. pneumoniae was recovered from 110/250 specimens (44.0%). The isolates showed marked resistance to ampicillin (96.36%), trimethoprim–sulfamethoxazole (86.36%), ceftriaxone (80.00%), and ciprofloxacin (63.64%). Resistance to tetracycline and doxycycline was 32.73% and 29.09%, respectively, whereas meropenem showed the lowest resistance rate (10.00%). Among the 36 tetracycline-resistant isolates screened by PCR, tetA was detected in 27 (75.00%), tetB in 22 (61.11%), and endr in 30 (83.33%).

Conclusions: The high level of resistance to several commonly used antimicrobials highlights a substantial therapeutic challenge associated with clinical K. pneumoniae in this setting. The frequent detection of tetA and tetB among tetracycline-resistant isolates, together with the high occurrence of the selected endr target, indicates a population in which antimicrobial resistance and virulence-associated determinants may coexist. These findings support continued local AMR surveillance, culture-directed therapy, antimicrobial stewardship, and further genomic investigation of resistant K. pneumoniae in Pakistan.