Antibiotic treatment for this case

The main facts that influence targeted therapy are:

• Mr Jenkins had a (severe) urinary sepsis and we have good evidence of the etiological agent: an ESBL-producing E. coli

• Although he is still febrile, the clinical course is favourable

• No evidence of abscess or urinary obstruction has been found

Considering all these facts, Mr. Jenkins probably benefits from:

• Continuing intravenous antibiotic therapy, at least until he is afebrile

• Continuing therapy with a single antibiotic

• Narrowing antimicrobial spectrum

Although probably the most active ß-lactam among the choices is meropenem, carbapenem is one of the most valuable drugs available in the antibiotic armamentarium and should be protected whenever possible.

Carbapenem-sparing strategies are needed in an era of increasing antimicrobial resistance. In this regard, as we seek to treat a urinary tract infection, which is a “low-risk” source provided there is no abscess nor obstruction and that the patient has clinically improved, amoxicillin/clavulanate (if the intravenous presentation is available) or piperacillin/tazobactam could be appropriate treatment options. Since we do not need anti-Pseudomonas activity, amoxicillin/clavulanate would be our choice if we were willing to continue therapy with a ß-lactam. In addition it has the advantage of an easy IV to PO switch.

Mr Jenkins could also be treated using non ß-lactam mono therapy with either amikacin or TMP/SMX.

Since Mr Jenkins is elderly, I would avoid amikacin if possible due to is nephron and ototoxicity.

TMP/SMX would be preferred to amikacin especially when the patient is ready for the IV to PO switch. In addition, TMP/SMX would be a better option than amikacin and even that ß-lactam if a prostate involvement (prostatitis) is suspected given its PK/PD properties. 

You may find the paper from the Scottish Antimicrobial Prescribing Group (SAPG) which provides advice for optimising antimicrobial prescribing for multi-drug resistant Gram-negative bacteria useful.