Correlation between Phenotypic Hypermucoviscosity and Antibiotic Resistance in Klebsiella pneumoniae

Abstract Introduction: Klebsiella pneumoniae is a Gram-negative opportunistic pathogen increasingly associated with multidrug resistant (MDR) and hypervirulence. The hypermucoviscous (HMV) phenotype, detected via the string test, is a surrogate marker for hypervirulent strains. With the rising threat of antibiotic-resistant hypervirulent strains, this study aimed to assess the correlation between phenotypic hypermucoviscosity and antibiotic resistance in K . pneumoniae clinical isolates. Materials and Methods: A cross-sectional study was conducted in a tertiary care microbiology laboratory. A total of 196 nonrepetitive K . pneumoniae clinical isolates were collected and identified as per standard procedures. The string test was used to detect the HMV phenotype. Antibiotic susceptibility was determined using the Kirby-Bauer disc diffusion method in accordance with Clinical and Laboratory Standards Institute 2020 guidelines. Extended-spectrum β-lactamase (ESBL) production was screened using the ceftazidime–clavulanate combination disc method. Results: Out of 196 isolates, 38 (19.39%) were identified as HMV-positive. These strains were predominantly isolated from respiratory specimens, especially sputum and bronchoalveolar lavage. Gentamicin resistance was significantly higher in HMV strains ( P = 0.015), and imipenem resistance was observed exclusively in HMV isolates ( P = 0.0002). ESBL production did not significantly differ between HMV (13.16%) and non-HMV strains (18.35%) ( P = 0.494). Conclusion: The study demonstrates a concerning correlation between hypermucoviscosity and resistance to key antibiotics, particularly gentamicin and imipenem. The presence of drug-resistant HMV strains in respiratory samples highlights the need for routine phenotypic screening and antimicrobial stewardship to guide effective treatment and infection control strategies.