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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 UTI?

a. Acinetobacter baumannii (A. baumannii)

b. Escherichia coli (E. coli)

c. Pseudomonas aeruginosa (P. aeruginosa)

d. Staphylococcus saprophyticus (S. saprophyticus)

Answer b is correct. The majority of UTIs are caused by gram-negative bacteria, of which E. coli is the most common pathogen. Table 23-1 lists the bacterial causes of UTIs and E. coli is the most common organism of uncomplicated and complicated UTIs. However, empiric therapy with E. coli will often cover/treat other organisms listed within Table 23-1. The exception would be Pseudomonas, select bacter organisms (eg, Citrobacter), and Enterococci.

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Table 23-1. Bacterial Causes of UTIs
  Uncomplicated (%) Complicated (%)
Gram-Negative
Escherichia coli 70-95 21-54
Proteus mirabilis 1-2 1-10
Klebsiella spp 1-2 2-17
Citrobacter spp <1 5
Enterobacter spp <1 2-10
Pseudomonas aeruginosa <1 2-19
Other <1 6-20
Gram-Positive
Staphylococcus saprophyticus 5-10 1-4
Enterococci 1-2 1-23
Group B streptococci <1 1-4
Staphylococcus aureus <1 1-2
Other <1 2

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. 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 UTIs. Although cefdinir is not indicated for treatment of UTIs, 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 ...

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