An Overview of Virulence, Resistance, and Clinical Significance of Klebsiella Infections.

Gram-negative, encapsulated, non-motile bacilli called Klebsiella species are commonly found in the environment and are a natural component of both human and animal flora. Among the genus, Klebsiella pneumoniae and Klebsiella oxytoca are the most clinically significant, while emerging species such as Klebsiella variicola and Klebsiella aerogenes are increasingly recognized in human infections. These organisms act as opportunistic pathogens and are associated with a variety of community-acquired and nosocomial infections, particularly in immunocompromised and hospitalized patients. Common clinical manifestations include urinary tract infections, pneumonia, bloodstream infections, wound and soft-tissue infections, intra-abdominal infections, and meningitis. The pathogenicity of Klebsiella species is attributed to multiple virulence factors, including a prominent polysaccharide capsule, adhesins, siderophores, lipopolysaccharide, and the ability to form biofilms. In recent years, the clinical importance of these organisms has grown as a result of the global emergence of multidrug-resistant (MDR) strains. The production of extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases, and carbapenemases has significantly reduced the effectiveness of commonly used antibiotics. Furthermore, MDR-hypervirulent (MDRhv) clones, which are linked to serious infections and few treatment choices, have emerged as a result of the convergence of multidrug resistance and hypervirulence. Accurate laboratory diagnosis and testing for antibiotic susceptibility are crucial for appropriate management and control of these infections.