Table 1.

Hierarchy of Risk Factors for Extended-Spectrum ß-Lactamase Production in Escherichia coli and Klebsiella Species^{2,4,5,12–18}

Order of Hierarchy	Risk Factor
1	Recent antibiotic use (with all antibiotics, all ß-lactams excluding carbapenems, and fluoroquinolones as subgroups)
2	Travel to Europe or Asia (defined as South or South East Asia)
3	Admission to hospital within the previous 3 months
4	Length of stay in hospital before infection
5	Residence in a long-term care facility
6	Malignancy
7	Diabetes mellitus
8	Mechanical ventilation
9	Charlson score
10	Urinary catheterization
11	Central line catheterization
12	Age ≥ 65 years