E. coli Classification
No, Escherichia coli (E. coli) is a gram-negative bacillus, not a gram-positive coccus. 1, 2
Microbiological Characteristics
E. coli is definitively classified as:
- Gram-negative rod-shaped bacterium in the family Enterobacteriaceae 1, 2
- Bacillus morphology (rod-shaped), not coccus (spherical) 1, 2
- Facultative anaerobic organism that commonly inhabits the lower intestinal tract of warm-blooded animals 2
Clinical Context
Understanding E. coli's gram-negative classification is critical for antibiotic selection:
- Gram-negative coverage is essential when treating E. coli infections, as it is the most common gram-negative facultative organism causing intra-abdominal infections 3
- Antibiotics must be active against enteric gram-negative aerobic and facultative bacilli for community-acquired infections involving E. coli 3
- In biliary infections, E. coli is among the most frequently encountered gram-negative bacteria requiring coverage 3
Common Pitfall
Do not confuse E. coli with gram-positive organisms like Enterococci or Staphylococci, which are gram-positive cocci and require different antimicrobial coverage 3. While both may coexist in polymicrobial infections (particularly intra-abdominal or biliary infections), their gram stain characteristics and antibiotic susceptibilities differ fundamentally 3.