Macrobid Should Be Discontinued - Switch to a Susceptible Agent
The sensitivity report shows the organism is susceptible to multiple antibiotics, but nitrofurantoin (Macrobid) is notably absent from the panel, which strongly suggests the organism is NOT susceptible to nitrofurantoin and you should switch to one of the reported susceptible agents immediately.
Critical Interpretation of the Sensitivity Report
The absence of nitrofurantoin from your sensitivity panel is the key finding here. When laboratories test organisms and report susceptibilities, they typically include nitrofurantoin for urinary isolates if the organism shows susceptibility 1. The fact that nitrofurantoin is missing from this extensive panel (which includes 10 other antibiotics) indicates the organism is either resistant or the laboratory deemed it inappropriate to report, both of which mean Macrobid should not be continued 1.
Organism Characteristics Based on Susceptibility Pattern
Your sensitivity pattern reveals:
- Susceptibility to ceftazidime, ceftazidime/avibactam, and ceftolozane/tazobactam suggests this is likely a Gram-negative organism, possibly Pseudomonas aeruginosa or another non-fermenting Gram-negative bacillus 1
- Susceptibility to aminoglycosides (amikacin, tobramycin) further supports a Gram-negative pathogen 1
- This pattern is NOT typical for common UTI pathogens like E. coli or Enterococcus species, which would normally show nitrofurantoin susceptibility 1
Why Nitrofurantoin Is Inappropriate Here
Nitrofurantoin has significant limitations that make it unsuitable for this infection 2:
- It does not achieve adequate serum or tissue concentrations outside the bladder 3
- It is ineffective against Pseudomonas species and many other non-fermenting Gram-negative organisms 1
- The drug is contraindicated in patients with renal impairment (creatinine clearance <60 mL/min) 2
- It should never be used for pyelonephritis or complicated UTIs 3
Recommended Alternative Antibiotics
Based on your sensitivity report, switch to one of these oral options if this is uncomplicated cystitis 1:
- Ciprofloxacin or levofloxacin (both reported susceptible) - 500 mg twice daily for 7 days for ciprofloxacin 1
- These fluoroquinolones achieve excellent urinary concentrations and are appropriate for organisms resistant to first-line agents 1
If this is complicated UTI, pyelonephritis, or the patient is clinically unstable, use IV therapy 1:
- Ceftazidime 2g IV every 8 hours 1
- Cefepime 2g IV every 8-12 hours 1
- Piperacillin/tazobactam 4.5g IV every 6 hours 1
- Consider adding an aminoglycoside (amikacin 15 mg/kg IV daily or tobramycin) for severe infections 1
Common Pitfalls to Avoid
- Do not continue empiric therapy when susceptibilities show the organism is not covered - this is the most critical error and leads to treatment failure 1
- Do not assume all UTI organisms are susceptible to nitrofurantoin - while E. coli typically is, other pathogens like Pseudomonas, Proteus, Serratia, and Klebsiella often are not 1, 4
- Do not use nitrofurantoin for upper tract infections or complicated UTIs - it lacks adequate tissue penetration 3, 2
- Verify renal function before prescribing any alternative - many of these agents require dose adjustment 2
Clinical Context Matters
If the patient is improving clinically on Macrobid despite the susceptibility pattern, this would be unusual and should prompt reconsideration of whether this is true infection versus colonization 1. However, the standard of care is to treat based on susceptibility data, not clinical response alone, to prevent treatment failure and resistance development 1.