Klebsiella (genus of Gram-negative bacteria)

Morphology and laboratory identification

Klebsiella are non-motile, facultatively anaerobic bacilli that ferment lactose, producing pink colonies on MacConkey agar. Routine identification uses Gram stain, culture characteristics, and biochemical tests; capsule presence may be demonstrated by special stains or mucoid colony morphology. Species-level identification increasingly relies on biochemical panels or molecular methods in clinical laboratories.

Common species

• Klebsiella pneumoniae – the principal pathogen in humans.
• Klebsiella oxytoca – associated with similar infections and occasionally antibiotic-associated colitis.
• Other environmental or opportunistic Klebsiella spp. with more limited clinical roles.

Clinical importance

Klebsiella species cause community-acquired and healthcare-associated infections. They are a well-known cause of pneumonia, particularly in people with underlying illness, and also cause urinary tract infections, bloodstream infections, biliary and liver abscesses, and wound infections. Rarely, organisms related to Klebsiella have been implicated in genital lesions such as donovanosis in older classifications.

Antibiotic resistance and treatment

A major concern is the ability of Klebsiella to acquire resistance genes. Extended-spectrum beta-lactamases (ESBLs) and carbapenemases have emerged and limit therapeutic options. Susceptibility testing guides therapy; severe infections may require combination treatment and consultation with infectious-disease specialists. Reports continue to describe novel resistant isolates and alerts about new drugs and resistant strains (new drug, resistant strain).

Prevention and public health

Prevention focuses on infection-control measures in healthcare settings, hand hygiene, prudent antibiotic use, surveillance and outbreak investigation. Vaccines are not yet in routine clinical use, and research on alternative therapies is ongoing.

History and taxonomy

The genus name and its classification have evolved with advances in microbiology and molecular taxonomy. Clinical laboratories follow current guidelines for identification, reporting and infection-control measures to limit spread.

Further information: Enterobacteriaceae overview, pneumonia resources, recent drug reports, resistance alerts, Klebsiella pneumoniae, donovanosis background.