Klebsiella (K. pneumoniae)

Klebsiella is a genus of Gram-negative, encapsulated, non-motile bacteria within the Enterobacteriaceae family, with Klebsiella pneumoniae being the most clinically significant species [1]. These bacteria are ubiquitous in nature and are common commensals of the human gastrointestinal tract, but they act as opportunistic pathogens causing severe infections such as pneumonia, urinary tract infections, and sepsis, particularly in healthcare settings [2]. Klebsiella is a primary driver of the global antimicrobial resistance crisis due to its high prevalence of extended-spectrum beta-lactamases (ESBLs) and carbapenemases, which render most standard antibiotics ineffective [3]. Treatment often requires specialized combination therapies or last-resort agents like polymyxins, though resistance to these is also emerging [4]. Understanding the virulence factors, such as the thick polysaccharide capsule and siderophores, is crucial for developing new therapeutic and preventive strategies [5]. The genus is also known for its ability to form biofilms, which further complicates treatment by protecting the bacteria from both the host immune system and antibiotic penetration [6].

Other names

Klebsiella speciesK. pneumoniaeK. oxytocaFriedlander's bacillusKlebsiella aerogenes

Antibiotics targeting Klebsiella species generally function through several distinct mechanisms: inhibition of cell wall synthesis by binding to penicillin-binding proteins (e.g., carbapenems, cephalosporins), inhibition of protein synthesis by targeting the 30S or 50S ribosomal subunits (e.g., aminoglycosides, tigecycline), or disruption of the bacterial outer membrane (e.g., polymyxins) [1][3][5].