Which antibiotics test can do after resistance?

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antimicrobial susceptibility testing after antibiotic resistance culture report guidance

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antimicrobial resistance susceptibility testing

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https://www.cdc.gov/antimicrobial-resistance-laboratory-netw…

The urine culture grew Klebsiella pneumoniae >100,000 CFU/mL, resistant to almost all routine antibiotics tested, including meropenem and ertapenem. This is a multidrug-resistant, likely carbapenem-resistant organism.

Tests to request within 48 hours while the laboratory still has the preserved isolate:

Carbapen-R Xpert / carbapenemase gene test
- Your report specifically advises M279: CARBAPEN-R-XPERT.
- It detects resistance genes such as NDM, KPC, VIM, IMP, and OXA-48. This helps the doctor choose the appropriate newer antibiotic.
Advanced susceptibility testing for newer antibiotics
- Your report advises M140 for other antibiotic-combination drugs.
- Ask for MIC/susceptibility testing for agents such as:
  - Ceftazidime-avibactam
  - Aztreonam-avibactam, or ceftazidime-avibactam plus aztreonam
  - Meropenem-vaborbactam
  - Imipenem-relebactam
  - Cefiderocol
    Which is appropriate depends on the carbapenemase gene result. CDC notes that expanded susceptibility testing can identify options for highly resistant Enterobacterales, including testing of ceftazidime-avibactam plus aztreonam for metallo-beta-lactamase producers. CDC testing guidance
Colistin broth microdilution (BMD)
- Your report specifically recommends M299: Colistin BMD, also within 2 days.
- The current report says colistin is intermediate, and routine methods can be unreliable. BMD is the confirmatory test. Colistin should not be started without an infectious-disease specialist's decision because of kidney and nerve toxicity.

Important: the report also states the urine has very low pus cells (0-1 WBC/HPF) and suggests the result could be contamination or colonization, particularly if there are no urinary symptoms. Bacteria in urine alone do not always require antibiotics; symptoms distinguish a UTI from asymptomatic bacteriuria. Goldman-Cecil Medicine, p. 43.

So, do not self-start antibiotics. See the treating doctor or an infectious-disease specialist urgently with this report, especially if there is fever, chills, flank/back pain, burning urination, vomiting, confusion, low blood pressure, or reduced urine output.

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