This proposed study aims to document the risk factors for quinolone resistance in bloodstream isolates of E. coli. Additionally, the adequacy of empiric antibiotic therapy for E. coli bloodstream infections will be assessed. Finally, outcome will be recorded - this is all-cause mortality at 28 days from the time of the first positive blood culture. Hypothesis: Ciprofloxacin resistant strains are associated with admission from nursing home and with prior quinolone use.

The following information will be collected: age, sex, occupation, hospital location at the time of positive culture (ER, medical ward, ICU etc), date of positive culture, prior hospitalization, receipt of outpatient dialysis, home care or other regular medical care (eg, outpatient chemotherapy), presence of invasive devices, receipt of antibiotics, including their type and whether they were adequate for the resistance profile of the organism, prior positive microbiologic cultures, time and location of positive cultures, underlying diseases and severity of illness, presence of urinary or intravascular devices, recent immunomodulative therapies or radiation therapy, physical exam findings, laboratory and radiographical data, antimicrobial usage within 30 days of onset of the infection, microbiological data and resistance patterns, choice of antibiotics once organism identified, bacteriological outcomes, laboratory results, demographic information, medications, clinical outcome,gender, height, weight, ethnicity, and past medical history. We will collect information retrospectively.

Inclusion Criteria:

Clinical information is collected by chart review of "case" and "control" patients.

A "case A" patient is defined as follows:

• One or more blood cultures are positive for E. coli. The organism is ciprofloxacin resistant.

A "case B" patient is defined as follows:

• One or more blood cultures are positive for E. coli. The organism is ciprofloxacin susceptible. Additionally, 4 controls who are in hospital at the same time as cases will be selected for each case.

Exclusion Criteria:

• If they do not meet inclusion criteria

E coli positive cultures