Serratia UTI discussion

If you got here without taking the case quiz go back here Dysuria and fever post surgery and take it.

My Recommendation

Change to ertapenem. He will need at least 14 days of therapy and without established effective oral options it will need to be completed intravenously. In future, fosfomycin may be shown to be a good option. See below.

Why not stay on ceftriaxone?

He appears to be responding to ceftriaxone but this may be short lived. The susceptibility test did not report ceftriaxone. However the asterix next to cefazolin denotes that there is more information available if it is “clicked” on. This is what is visible after “clicking”:

“This organism has a chromosomal Inducible Beta lactamase. The organism is resistant to ampicillin, amoxicillin/clavulanic acid, piperacillin/tazobactam, and all cephalosporins.”

Serratia marcescens is a member of the so-called “SPICE” group of organisms (Serratia, Pseudomonas, Proteus, Citrobacter, Enterobacter) that all produce AmpC beta-lactamases. They are also referred to as inducible beta-lactamase producers (IBLs).

This is not an optimal means of reporting susceptibilities that will be rectified in upcoming improvements to the Cerner EMR.

Why not gentamicin or tobramycin?

Aminoglycosides are too toxic for use in this setting where other options are available. They are particularly worrisome in the elderly where renal function is often reduced.

Why not nitrofurantoin?

Nitrofurantoin is only indicated for simple cystitis in women. This man has either pyelonephritis or prostatitis.

Why not fosfomycin?

Fosfomycin is an old agent that has been “resurrected”. It’s only officially indicated as single dose therapy for simple cystitis in women. However, there is considerable interest in evaluating its role in other infections including prostatitis. See this recent paper from Clinical Infectious Diseases suggesting it may be of utility.