Here is an example comment from Pathology North which is added to positive blood culture reports when a Gram negative coliform species ( Enterobacteriacae eg. E. coli) has been isolated:

The comment’s rationale is to promote short course treatment and also to prompt oral antibiotic switching in a timely manner.  It also prompts consideration of source control, an important issue in all patients with sepsis. There are no data that establish a minimum duration for IV therapy.  Endocarditis and other metastatic complications are extremely rare with these species, contrasting with bacteraemia due to Staphylococcus aureus where prolonged high dose IV therapy is predicated on this risk.

The evidence base indicates that, even in bacteraemic patients,  short course treatment is appropriate for most patients once source control is achieved.  The commonest principal sites for Gram negative sepsis are the urinary tract, biliary tract and other intra-abdominal sources.  Source control of these sites may involve alleviating urinary/ biliary blockage or drainage, lavage and control of intra-abdominal collections.  Patients with an undiagnosed source need close diagnostic evaluation and consideration of whether an IV line or other invasive device is responsible (nearly always a central line).

Referencing Pathology North data on bacteraemic infections with Enterobacteriaceae (2008-2013), the principal infection sites for community acquired infections (n=2,944) were most commonly urinary tract (53% of events) followed by sepsis with undiagnosed primary source (22%), biliary tract infection (16%), other abdominal sepsis (4%), pneumonia (2%)  and gastrointestinal tract infections (1%).

In contrast, in healthcare-associated bacteraemic infections (n=878), the most common principal sites of infection were sepsis with undiagnosed primary source (27%), IV line-associated (25%), urinary tract (22%), abdominal sites (14%), pneumonia (4%) and surgical wound infection (3%).

Reference

• Sawyer et al.  Trial of Short-Course Antimicrobial Therapy for Intraabdominal Infection. N Engl J Med 2015;372:1996-2005.