Clinical Manifestations by Species and Subspecies
Symptoms and localization of the pathological process depend on the specific microorganism causing the infection.
Classical Friedländer's bacillus (K. pneumoniae subsp. pneumoniae) This is a leading nosocomial pathogen, primarily affecting the respiratory and urinary tracts. It displays pronounced multidrug resistance.
- Causes non-specific respiratory tract infections (bronchitis, pneumonia).
- Infects the urinary system.
- Can cause foodborne toxicoinfections.
- Responsible for purulent-septic complications: postpartum and neonatal infections (intestinal infections, pneumonia, and high-mortality neonatal sepsis).
Specific K. pneumoniae subspecies
- K. pneumoniae subsp. ozaenae: Colonizes the mucosa of the nasal cavity and paranasal sinuses. A hallmark clinical feature is the production of foul-smelling nasal discharge (ozena).
- K. pneumoniae subsp. rhinoscleromatis: The causative agent of rhinoscleroma (affecting the upper respiratory tract). Pathomorphologically, it is characterized by granuloma formation leading to tissue fibrosis and sclerosis. The disease is chronic due to intracellular persistence.
Other clinically significant species
- K. oxytoca: Frequently causes healthcare-associated infections, particularly in urology.
- K. granulomatis: The causative agent of donovanosis (granuloma inguinale), a sexually transmitted infection endemic to tropical climates (rarely transmitted via non-sexual contact). It manifests as ulcerating granulomatous lesions of the skin and subcutaneous tissue.
Immune Response Features
Immunity against Klebsiella infections has specific characteristics. Humoral response alone generally lacks protective efficacy. The primary defense mechanism is phagocytosis, which requires prior opsonization of the bacteria by specific antibodies.
In chronic infections such as rhinoscleroma, the pathogen resides intracellularly within host cells for prolonged periods. This intracellular persistence leads to delayed-type hypersensitivity (DTH) reactions.
Microbiological Diagnostics
The choice of diagnostic method depends on the clinical presentation and the suspected site of infection.
- Bacteriological method (primary). Clinical specimens may include sputum, urine, stool, blood, or pus. Inoculation is performed on lactose-containing differential media. The primary goal is isolating a pure culture and identifying the species or subspecies.
- Serological method. Includes the complement fixation test (CFT) using specific O-antigens.
- Bacterioscopic method. Used specifically for diagnosing donovanosis. Biopsy material from the granuloma is stained with Giemsa stain. The key diagnostic finding is the visualization of Donovan bodies in smears.
Treatment and Prevention
Specific prophylaxis for Klebsiella infections has not been developed, and no approved vaccines are currently available.
Treatment involves the use of Klebsiella bacteriophage and antibacterial therapy. Due to high virulence factors and multidrug resistance, antibiotic selection must be strictly guided by antimicrobial susceptibility testing (antibiogram) results.