General Characteristics
- Gram-negative rods (straight rods, non-spore forming).
- Facultative anaerobes.
- Oxidase-negative, catalase-positive, nitrate-reducing.
- Ferment glucose with acid and/or gas production.
- Most grow on MacConkey agar (differentiates lactose fermenters).
- Capsule present in Klebsiella (mucoid colonies).
- Flagella:
- Klebsiella = non-motile.
- Enterobacter, Serratia = motile (peritrichous flagella).
- Common opportunistic nosocomial pathogens – affect immunocompromised hosts.
Diseases Caused by K-E-S Group
Primarily nosocomial infections in immunocompromised or device-associated patients.
- 1. Pneumonia:
- Commonly Klebsiella pneumoniae
- Often necrotizing, with currant jelly sputum
- Seen in alcoholics, diabetics, ventilated patients
- 2. UTIs:
- Often catheter-associated
- Klebsiella, Enterobacter, Serratia all involved
- 3. Sepsis / Bacteremia:
- Especially in ICU settings
- Multidrug resistance makes treatment difficult
- 4. Wound infections:
- Post-surgical sites, pressure ulcers
- 5. Meningitis (Neonatal):
- Rare, usually Klebsiella or Enterobacter
- 6. Osteomyelitis (rare)
- 7. Endocarditis (IV drug use)
Diagnosis
- Sample: sputum, urine, blood, pus depending on infection site.
- Culture:
- MacConkey agar:
- Lactose fermenters = pink colonies (Klebsiella, Enterobacter).
- Serratia = colorless.
- Blood agar: Serratia = red pigmented (prodigiosin).
- Microscopy: Gram-negative rods.
- Biochemical Tests: as per table above.
- Antibiotic sensitivity testing is essential due to resistance.