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Chapter 23. Urinary Tract Infections

GB is a 28-year-old woman with a chief complaint of dysuria. Symptoms started 3 days ago. The physician orders a urinalysis and a urine culture. What is the most likely bacterial cause of the urinary tract infection (UTI)?

a. Acinetobacter baumannii

b. Escherichia coli

c. Pseudomonas aeruginosa

d. Staphylococcus saprophyticus

Answer b is correct. The majority of UTIs are caused by gram-negative bacteria, of which E. coli is the most common pathogen. E. coli is the most common organism of uncomplicated and complicated UTIs. However, empiric therapy with E. coli will often cover/treat other less common organisms. The exception would be Pseudomonas, select bacter organisms (eg, Citrobacter), and Enterococci.

Answer a is incorrect. A. baumannii is a nosocomial organism and a cause of catheter-associated UTIs.

Answer c is incorrect. P. aeruginosa is a nosocomial organism and causes <20% of UTIs.

Answer d is incorrect. S. saprophyticus only causes 5% to 10% of uncomplicated UTIs. It is the most common gram-positive bacteria causing uncomplicated UTIs.

GB is a 28-year-old woman with a chief complaint of dysuria. Symptoms started 3 days ago. The physician orders a urinalysis and a urine culture. What is appropriate empiric therapy for GB? Patient has normal renal function and no medication allergies. Current home medications include metoprolol and omeprazole.

a. Cefdinir

b. Linezolid

c. Amoxicillin

d. TMP-SMX

Answer d is correct. TMP-SMX is appropriate empiric therapy for GB. If the local E. coli resistance rate for TMP-SMX is high, ciprofloxacin would be an appropriate choice.

Answer a is incorrect. Cefdinir is an oral third-generation cephalosporin commonly used for acute otitis media in pediatrics. It is not indicated for treatment of urinary tract infections (UTIs). Although cefdinir is not indicated for treatment of urinary tract infections, you may see an oral cephalosporin utilized. Bacteria are becoming increasingly more resistant and management is driven by in vitro results of a culture and susceptibility report. There are often times when an E. coli UTI is resistant to SMX/TMP and quinolones; therefore, alternative therapy may be utilized (even if it is not indicated).

Answer b is incorrect. Linezolid is an antibiotic that covers gram-positive bacteria exclusively. It is primarily used to treat methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE). Both MRSA and VRE can cause UTIs, but GB does not need to be empirically covered with linezolid.

Answer c is ...

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