AmpC E. coli Discussion

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My recommendation

Imipenem. Carbapenems are reliable therapy for AmpC E. coli pyelonephritis. Commonly used beta-lactams (ceftriaxone and piperacillin/tazobactam) are not. Read more about carbapenems here Carbapenem notes.

Why not nitrofurantoin?

This woman has pyelonephritis as evidenced by her systemic symptoms. Nitrofurantoin in only indicated for thetreatment of cystitis, not pyelonephritis.

Why not tobramycin?

Tobramycin would be effective therapy for this infection but is considerably more toxic than is imipenem. Close monitoring of drug levels improves safety but nephrotoxicity, ototoxicity and vestibulotoxicity are common.

Why not ertapenem?

Ertapenem is a newer, once daily carbapenem that would be effective therapy in this case. Currently it is reserved for use in outpatient settings in British Columbia though that is being reconsidered.

Why not fosfomycin?

Fosfomycin is an old antibiotic making a comeback and its only approved indication is for the therapy of simple cystitis in a 3 gram single dose form. However, it is one of the only oral options for resistant organisms like in this case and experience with its use for pyelonephritis and other indications is growing.

Take home

This case is a great example of the relentless progression of antibiotic resistance and the need to be very careful with the remaining effective antibiotics. E. coli is present in large numbers in all people. It is the most common cause of urinary tract infections and, until recently, was relatively easy to treat with several reliable oral antibiotic options. These AmpC strains of E. coli are challenging. If you are interested in more in-depth treatment of AmpC beta-lactamases look here Clin. Micro. Rev – Beta Lactamases.

The scenario presented here is now a regular occurence in BC. The use of carbapenems is increasing and with it the worry of promoting and sustaining carbapenem-resistant organisms (CPOs) for which there are almost no antibiotic options. This makes efforts at prevention of urinary tract infections more important than ever. Attention to hydration and catheter use in hospitals and long term care are particularly important.

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