E. coli is gram-negative, facultatively anaerobic, bacilli. It is a member of Enterobacteriaceae and normal flora in the human intestine. It most commonly causes urinary tract infections, diarrhea, or intra-abdominal infections. It may cause pneumonia and neonatal meningitis. Some virulent strains have results in outbreaks in healthy populations; severe complication and even death have been reported. E. coli causes health-care associated infections. Those with ESBL are multidrug resistant. Recently, emergence of carbapenem-resistant E. coli poses great threat to healthcare system.