What is the recommended microbiology screening for a transplant patient, including tests for viral and bacterial infections, such as Cytomegalovirus (CMV) and Methicillin-resistant Staphylococcus aureus (MRSA), and latent infections like Tuberculosis (TB)?

Microbiology Screening for Transplant Candidates

All transplant candidates require comprehensive pre-transplant infectious disease screening to identify active infections requiring treatment, determine post-transplant prophylaxis strategies, and assess transplant eligibility. 1

Viral Screening Panel

Cytomegalovirus (CMV)

• Both donor and recipient must be screened by CMV serology (IgG) prior to transplant 2
• CMV serostatus determines risk stratification and prophylaxis strategy, with donor-positive/recipient-negative (D+/R-) representing the highest risk group 3, 4
• No routine pre-transplant viral load monitoring is needed; quantitative PCR monitoring begins post-transplant 2

Epstein-Barr Virus (EBV)

• Pre-transplant EBV serology (IgG) is essential for risk stratification 2, 5
• EBV-seronegative recipients receiving organs from seropositive donors have increased risk of post-transplant lymphoproliferative disorder 5, 6
• Screening helps guide post-transplant monitoring intensity 7, 5

Hepatitis B Virus (HBV)

• Screen all candidates with HBsAg, anti-HBc (total), and anti-HBs (quantitative) 4
• Anti-HBs ≥10 IU/mL indicates protective immunity from vaccination or resolved infection 4
• Positive anti-HBc with negative HBsAg indicates prior exposure and may require prophylaxis depending on organ type 4

Hepatitis C Virus (HCV)

• HCV antibody screening is mandatory for all transplant candidates 4
• Positive antibody requires confirmatory HCV RNA testing to distinguish active from resolved infection 4
• Active HCV infection does not contraindicate transplantation but requires post-transplant antiviral therapy planning 4

Human Immunodeficiency Virus (HIV)

• HIV antigen/antibody combination screening is required for all candidates 4
• HIV-positive status is no longer an absolute contraindication with modern antiretroviral therapy 4

Other Viral Pathogens

• Consider screening for HSV and VZV serology to guide prophylaxis strategies 5, 6
• Geographic-specific screening (e.g., West Nile virus, HTLV-1/2) based on epidemiologic risk 8, 6

Bacterial Screening

Methicillin-Resistant Staphylococcus aureus (MRSA)

• No routine bacterial screening is recommended by transplant guidelines 2
• However, MRSA nasal swab screening is commonly performed in clinical practice for decolonization protocols, particularly in lung and heart transplant candidates
• Cultures should only be obtained when clinical symptoms suggest active infection 2

Active Bacterial Infections

• Any suspected active bacterial infection requires appropriate cultures before transplantation 2
• Active untreated bacterial infections typically require treatment completion before proceeding with transplant 1

Mycobacterial Screening

Tuberculosis (TB)

• Screen all transplant candidates for latent TB infection 4, 1
• Interferon-gamma release assay (IGRA) such as QuantiFERON-Gold is preferred over tuberculin skin testing in transplant candidates 4
• Positive IGRA indicates latent TB requiring treatment before or after transplantation but does not contraindicate organ donation or receipt 4
• Chest radiograph should be obtained in all candidates to exclude active TB 1

Fungal Screening

Endemic Mycoses

• Screening for endemic fungi (Histoplasma, Coccidioides, Blastomyces) should be based on geographic exposure history 1, 5
• Serologic testing or antigen detection may be indicated in high-risk populations 1

Candida and Aspergillus

• No routine screening is recommended; surveillance cultures are not predictive of invasive disease 1

Parasitic Screening

Strongyloides

• Screen candidates with epidemiologic risk factors (endemic area residence or travel) with Strongyloides serology 1
• Untreated strongyloidiasis can cause fatal hyperinfection syndrome post-transplant 1

Toxoplasma

• Toxoplasma serology (IgG) is particularly important for heart transplant candidates 1, 5
• Seronegative recipients of seropositive donor hearts require prophylaxis 5

Trypanosoma cruzi (Chagas Disease)

• Screen candidates with Latin American origin or exposure history 1

Critical Timing and Documentation

All screening should be completed during the pre-transplant evaluation period, ideally before listing 1. Results must be documented and readily available at the time of transplant to guide immediate post-transplant prophylaxis decisions 2.

Common Pitfalls to Avoid

• Do not rely on historical serologies—repeat testing if previous results are more than 6-12 months old, as serostatus may change 1
• Window period infections can be missed—antibody testing alone may not detect recent infections; consider nucleic acid testing for high-risk donors 4
• False-negative results occur with hemodilution—ideally obtain samples before massive transfusions 4
• A single positive coagulase-negative Staphylococcus blood culture without symptoms is typically a contaminant, not true bacteremia 2