When should antibiotic prophylaxis be given to a patient with glomerulonephritis (GN) starting immunosuppressants, especially those with a history of recurrent infections or underlying health conditions?

Antibiotic Prophylaxis in GN Patients Starting Immunosuppression

Screen for latent infections prior to initiating immunosuppression and prescribe prophylaxis based on specific risk factors—particularly Pneumocystis jiroveci pneumonia (PJP) prophylaxis with trimethoprim-sulfamethoxazole for patients with lymphocytopenia, high serum creatinine, severe anemia, or high chronicity indices on kidney biopsy. 1, 2

Pre-Immunosuppression Screening Requirements

Before starting any immunosuppressive regimen for glomerulonephritis, you must screen for latent infections as a mandatory step 1:

• Test for hepatitis B virus (HBV) in all patients with proteinuric glomerular disease, as HBV reactivation is a serious complication with B-cell depleting and alkylating agents 1
• Test for hepatitis C virus (HCV) in patients with cryoglobulinemic GN or risk factors 1
• Assess vaccination status and update as required before immunosuppression 1
• Review infection history including recurrent infections, prior opportunistic infections, and geographic exposures 1

Specific Prophylaxis Indications

Pneumocystis Jiroveci Pneumonia (PJP) Prophylaxis

Give trimethoprim-sulfamethoxazole prophylaxis if ANY of the following risk factors are present 2:

• Lymphocytopenia (absolute lymphocyte count <1000/μL) at immunosuppressant initiation 2
• High serum creatinine at baseline 2
• Severe anemia (hemoglobin <10 g/dL) 2
• High chronicity indices on kidney biopsy (>50% interstitial fibrosis/tubular atrophy) 2
• Persistent lymphocytopenia during treatment 2

The average time to PJP onset is 2.4 months after immunosuppressant initiation, making early prophylaxis critical 2. Trimethoprim-sulfamethoxazole is highly effective in preventing PJP but monitor for sulfonamide reactions, myelosuppression, and oral candidiasis 3.

Bacterial Prophylaxis

Routine antibacterial prophylaxis is NOT recommended for GN patients starting immunosuppression 3. However, specific situations require targeted antibiotic therapy:

• Active or recent bacterial infection: Treat the underlying infection completely before initiating immunosuppression 1
• Infection-related GN: Administer appropriate antibiotics (penicillin for streptococcal, prolonged therapy for endocarditis) to reduce antigenic load before or concurrent with immunosuppression 1, 4
• Do NOT use fluoroquinolone prophylaxis routinely—it lacks gram-positive coverage and promotes resistance 3

Antifungal Prophylaxis

Antifungal prophylaxis is generally not indicated for GN patients unless they are undergoing hematopoietic stem cell transplantation or have documented high risk for invasive fungal infections 3.

Antiviral Prophylaxis

• HBV-positive patients: Start antiviral therapy (entecavir or tenofovir) before immunosuppression to prevent reactivation, particularly with B-cell depleting agents 1
• Routine antiviral prophylaxis for other viruses is not indicated 3

Monitoring During Immunosuppression

Once immunosuppression is initiated, monitor closely for infection risk 1:

• Serial absolute lymphocyte counts—persistent lymphocytopenia (<500/μL) warrants PJP prophylaxis even if not initially prescribed 2
• Monitor for development of infections including opportunistic pathogens 1
• Adjust immunosuppressant doses based on GFR to minimize toxicity and infection risk 1
• Consider dose reduction in patients with persistent lymphocytopenia or recurrent infections 2

Common Pitfalls to Avoid

• Do NOT delay screening for latent infections—this must occur before immunosuppression starts, not after 1
• Do NOT use corticosteroids in IgA-dominant post-infectious GN (typically staphylococcal in elderly/diabetics), as this can worsen infection 1
• Do NOT withhold antibiotics in infection-related GN even when active infection seems resolved—the goal is reducing antigenic load 1, 4
• Do NOT ignore chronicity on kidney biopsy—high chronicity indices predict PJP risk and should trigger prophylaxis 2
• Do NOT use broad-spectrum antibacterial prophylaxis routinely—this promotes resistance without proven benefit 3

Algorithm for Decision-Making

1. Screen all patients for HBV, HCV (if indicated), and latent infections 1
2. Assess PJP risk factors at baseline: lymphocyte count, creatinine, hemoglobin, biopsy chronicity 2
3. If ≥1 PJP risk factor present: Start trimethoprim-sulfamethoxazole prophylaxis 2
4. If infection-related GN: Treat underlying infection with appropriate antibiotics before/during immunosuppression 1, 4
5. If HBV-positive: Start antiviral therapy before immunosuppression 1
6. Monitor lymphocyte counts monthly—add PJP prophylaxis if persistent lymphocytopenia develops 2
7. Adjust immunosuppressant doses for renal function to minimize infection risk 1