How to treat diphtheroids (diphtheria-like bacteria) in urine?

Treatment of Diphtheroids in Urine

Diphtheroids in urine typically do not require treatment unless the patient is symptomatic, as they are generally considered colonizers rather than true pathogens. Most cases represent asymptomatic bacteriuria, which current guidelines strongly recommend against treating in most populations 1.

Understanding Diphtheroids

Diphtheroids are aerobic, non-sporulating, pleomorphic Gram-positive bacilli that are typically commensals of the skin and mucous membranes 2. They include various Corynebacterium species that are often considered contaminants when isolated from clinical samples. However, in certain circumstances, they can be clinically significant:

• They may form biofilms and cause multidrug-resistant infections in healthcare settings 2
• Only about 18% of isolated diphtheroids represent true infection, while 82% are contaminants 3
• In urine specifically, only about 22% of diphtheroid isolates have been found to be clinically significant 3

Assessment of Clinical Significance

To determine if diphtheroids in urine represent true infection versus colonization:

1. Evaluate for symptoms:

   • Presence of dysuria, frequency, urgency, or suprapubic tenderness
   • Absence of symptoms suggests asymptomatic bacteriuria

2. Consider patient factors:

   • Pregnancy status (treatment indicated)
   • Planned urological procedures (treatment indicated)
   • Immunocompromised status
   • Presence of indwelling catheters

3. Laboratory assessment:

   • Presence of pyuria (>10 WBC/HPF)
   • Bacterial count (>10^5 CFU/mL is significant)
   • Pure growth vs. mixed flora

Treatment Recommendations

When NOT to Treat

According to the European Association of Urology (2024) and IDSA (2019) guidelines, do NOT treat asymptomatic bacteriuria in 1:

• Women without risk factors
• Patients with well-regulated diabetes mellitus
• Postmenopausal women
• Elderly institutionalized patients
• Patients with dysfunctional/reconstructed lower urinary tract
• Renal transplant recipients
• Patients before arthroplasty surgery
• Patients with recurrent UTIs

When to Treat

Treat diphtheroids in urine ONLY in the following circumstances:

1. Symptomatic infection (true UTI)
2. Pregnant women 1, 4
3. Before urological procedures breaching the mucosa 1

Treatment Options for Symptomatic Infection

If treatment is indicated, based on the most recent guidelines 5, 6:

1. First-line options:

   • Trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) 6
   • Nitrofurantoin (100 mg twice daily for 5 days) - avoid if CrCl <30 mL/min 5
   • Fosfomycin (3 g single dose) 5

2. Alternative options:

   • Cephalexin (500 mg four times daily for 5-7 days) 5
   • Amoxicillin-clavulanate (based on susceptibility testing) 5

3. Reserve options (use only when other options cannot be used):

   • Fluoroquinolones (due to high risk of adverse effects and increasing resistance) 5

Special Considerations

• Males: UTIs in males often involve the prostate and may require longer treatment courses (10-14 days) 5
• Renal impairment: Avoid nitrofurantoin if CrCl <30 mL/min; adjust doses of other antibiotics accordingly 5
• Elderly patients: May present with atypical symptoms; consider renal function when selecting antibiotics 5
• Diabetic patients: Higher risk for complications; require adequate follow-up 5

Monitoring and Follow-up

• Monitor for symptom resolution within 48-72 hours if treating symptomatic infection 5
• Follow-up cultures are generally not necessary if symptoms resolve
• Consider urological evaluation for recurrent infections, especially in males

Prevention Strategies

For patients with recurrent infections:

• Increased water intake (additional 1.5L daily) 5
• Consider cranberry products containing proanthocyanidin (36 mg) 5
• For postmenopausal women, consider vaginal estrogen therapy 5

Remember that most diphtheroids in urine represent colonization rather than infection, and unnecessary antibiotic treatment contributes to antimicrobial resistance without providing clinical benefit.