What is a suitable treatment option for a 41-year-old patient with a history of pulmonary embolism and deep vein thrombosis (DVT) with an undefined hypercoagulable disorder, who has a sulfa allergy and presents with a recurrent urinary tract infection (UTI) caused by Escherichia coli (E. coli) resistant to ampicillin, after initial improvement with Macrobid (nitrofurantoin)?

From the Guidelines

For this patient with recurrent UTI symptoms after completing a course of Macrobid (nitrofurantoin), I would recommend ciprofloxacin 500 mg orally twice daily for 7 days. This fluoroquinolone antibiotic is an appropriate choice given the patient's sulfa allergy (ruling out trimethoprim-sulfamethoxazole) and the culture results showing E. coli resistant only to ampicillin, as noted in the guidelines 1. Ciprofloxacin provides excellent coverage against the identified E. coli and Streptococcus anginosis. The patient should complete the full course even if symptoms improve before completion. Given her history of hypercoagulable disorder with previous pulmonary embolism and DVT, ciprofloxacin is preferable to extended nitrofurantoin treatment, which could increase thrombotic risk with prolonged use, as suggested by the potential for collateral damage and resistance patterns 1. Adequate hydration should be maintained during treatment, and the patient should be advised that ciprofloxacin may cause tendon inflammation rarely, so any new joint or tendon pain should prompt medical evaluation. If symptoms persist after this treatment course, further evaluation for complicated UTI or structural abnormalities would be warranted.

Some key points to consider in the treatment of this patient include:

• The efficacy of ciprofloxacin in treating UTIs, with clinical cure rates of 90% (85-98%) and microbiological cure rates of 91% (81-98%) 1
• The importance of completing the full treatment course, even if symptoms improve before completion, to ensure eradication of the infection
• The potential risks and side effects of ciprofloxacin, including tendon inflammation and the need for adequate hydration
• The consideration of alternative treatment options, such as fosfomycin or pivmecillinam, in cases where ciprofloxacin is not suitable or effective, as discussed in the guidelines 1.

Overall, the choice of ciprofloxacin for this patient is based on the most recent and highest quality evidence available, including the guidelines from the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases 1.

From the FDA Drug Label

The bacteriologic cure rates overall for levofloxacin and control at the test-of-cure (TOC) visit for the group of all patients with a documented pathogen at baseline (modified intent to treat or mITT) and the group of patients in the mITT population who closely followed the protocol (Microbiologically Evaluable) are summarized in Table 20 Microbiologic eradication rates in the Microbiologically Evaluable population at TOC for individual pathogens recovered from patients randomized to levofloxacin treatment are presented in Table 21.

The patient has a sulfa allergy, and the urine culture grew E. coli only resistant to ampicillin and streptococcus anginosis.

• Levofloxacin is a potential treatment option for this patient, given its effectiveness against E. coli and other pathogens.
• The patient's past medical history of pulmonary embolism and DBT with a undefined hypercoagulable disorder should be considered when selecting an antibiotic.
• However, based on the provided information, levofloxacin appears to be a suitable choice for the treatment of this UTI 2.

From the Research

Treatment Options for UTI

Given the patient's sulfa allergy and the resistance pattern of the E. coli isolate, the following treatment options can be considered:

• Nitrofurantoin: As shown in the study 3, nitrofurantoin has an excellent susceptibility profile against E. coli, with 99.4% of isolates being susceptible.
• Fosfomycin: The study 3 also demonstrated that fosfomycin has a high susceptibility rate against E. coli, with 100% of isolates being susceptible.

Considerations for Patients with Sulfa Allergy

For patients with a sulfa allergy, it is essential to consider the cross-reactivity between sulfa antibiotics and non-antibiotics, as discussed in the studies 4 and 5. However, in this case, the patient's allergy is to sulfa, and the alternative treatments (nitrofurantoin and fosfomycin) are not sulfa-based, making them potential options.

Resistance Patterns and Treatment

The study 6 highlights the concern of resistance to antibiotic treatment, particularly fluoroquinolones, in E. coli. The study 7 also discusses the mechanisms of resistance in E. coli, including the acquisition of genes coding for extended-spectrum β-lactamases and plasmid-mediated quinolone resistance. However, in this case, the E. coli isolate is only resistant to ampicillin, and the patient has already shown improvement with Macrobid (nitrofurantoin) before the return of symptoms. Therefore, re-treatment with nitrofurantoin or consideration of fosfomycin as an alternative may be appropriate, as supported by the studies 3 and 7.