Brief Answer:
It mainly depends on the antibiogram (Culture sensitivity report of the urine)...

Detailed Answer:
Hello there,
Welcome to 'Ask A Doctor' service...
I've gone through your query in details...
I can understand your concerns...

Well, first of all, I suppose (correct me if otherwise) Proteus Mirabilis is detected this time only while there were other organisms detected in urine earlier...

The most important factors deciding upon the need for IV antibiotics would be the Antibiogram (it'd be given in the Urine Culture and Sensitivity study, which could be already done before starting Zosyn)...

So, I'd request you to kindly upload the complete urine Culture Sensitivity report so that I can review it in details to see the nature of the detected bacteria (Proteus in this case)...You can upload/attach them to the 'Reports section' of this web-page only...

See, there are several factors to decide upon the need for IV antibiotics and PICC line is one of the safest devices to keep in case of long term requirements...

Chronic interstitial cystitis itself is an aetiology for developing resistant bugs...Since this is the third time IV antibiotic therapy initiated, chances of developing resistance to antibiotics are also high (higher the chances, stronger the antibiotics and the only preferable route is, unfortunately, IV only...)

Could you kindly provide some specific details (as follows) so that I can assist you specifically:

-Is the patient bed-ridden? If yes, then please let me know the relevant past medical history...

-Is the patient on a urinary catheter (Foley's catheter)?

-Is the patient diabetic?

-How is the overall health (nutrition status, bowel-bladder habits etc)?

It'd be a pleasure to assist you further, but kindly provide these details so that I can guide you specifically...

Take Care
Kind Regards

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