In terms of epidemiological characteristics, Gram-negative bacteria producing AmpC β - lactamase consisted of the highest percentage in patients over 40 years old (75%), having underlying diseases (cirrhosis, diabetes, or immunocompromised ones) (63.6%); used to be on cephalosporin III treatment 3 months before (34.1%), hospital admission 6 months before (59.1%), ICU admission (18.2%).