A curated, searchable collection of real-world infectious disease cases from the American Society for Microbiology. Each case guides readers through the full clinical journey—from patient presentation and diagnostic challenges to pathogen identification, treatment decisions, and high-yield teaching pearls—bridging microbiology, clinical reasoning, and patient care.
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This report details one confirmed and one potential human case of influenza A(H5N1) detected through an expanded subtyping protocol. The confirmed case involved a patient presenting with respiratory symptoms, where H5N1 was identified via PCR and sequencing. The second case, a healthcare worker, showed serological evidence of exposure without clear symptoms. Current surveillance often misses community-acquired infections by focusing only on those with known animal exposure. Implementing universal H5 subtyping on all influenza A-positive samples allowed for broader detection. Teaching point: Expanded laboratory surveillance beyond animal exposure criteria is crucial for early detection of novel zoonotic influenza strains and understanding community transmission.
This article is a response to a commentary on a previous case report regarding dual β-lactam success in Mycobacterium abscessus infections. While the original case report demonstrated positive outcomes, this response emphasizes the need for caution in interpreting such results. It highlights the complex nature of M. abscessus, particularly its inducible β-lactamase (BlaMab) and potential for resistance development. The authors advocate for rigorous susceptibility testing, including time-kill assays, and careful consideration of host factors and clinical context before broadly applying dual β-lactam therapies. Teaching point: Interpreting treatment success for complex pathogens like Mycobacterium abscessus requires caution, comprehensive susceptibility testing, and consideration of resistance mechanisms.
This case describes nosocomial transmission of highly pathogenic avian influenza (HPAI) in an immunocompromised resident clinic cat. The feline patient, likely exposed to HPAI via raw meat or fomites from infected poultry, presented with severe respiratory distress, lethargy, and anorexia. Diagnosis was confirmed through molecular testing for influenza A virus. The cat's immunocompromised state exacerbated the infection, leading to a critical condition. This incident highlights the zoonotic potential of HPAI and the critical importance of stringent infection prevention and control measures in veterinary settings, especially when dealing with vulnerable animals. Teaching point: Strict biosecurity protocols are essential to prevent zoonotic disease transmission, even in seemingly controlled environments.
This report describes invasive fungal infections in patients receiving Bruton tyrosine kinase inhibitors (BTKIs). A 75-year-old male with chronic lymphocytic leukemia on acalabrutinib presented with fever and cough. Imaging revealed pulmonary infiltrates, and bronchoalveolar lavage identified Aspergillus fumigatus, diagnosed as invasive pulmonary aspergillosis. He was successfully treated with isavuconazole. Another case involved a 66-year-old male with mantle cell lymphoma on acalabrutinib who developed rhinocerebral mucormycosis, confirmed by biopsy. This highlights BTKIs as a risk factor for severe invasive fungal infections like aspergillosis and mucormycosis. Teaching point: Clinicians should maintain a high index of suspicion for invasive fungal infections in BTKI-treated patients presenting with compatible symptoms.
A premature neonate, requiring prolonged hospitalization, intensive care, multiple surgeries, and broad-spectrum antibiotics, developed a systemic fungal infection. Initial blood cultures identified a Candida species, later confirmed as Candida berthetii through molecular sequencing. The infant received antifungal treatment with amphotericin B and fluconazole, eventually recovering. This case represents the first documented human systemic infection by C. berthetii, highlighting the diagnostic challenges of emerging fungal pathogens in vulnerable populations like preterm infants. Teaching point: Advanced molecular diagnostics are crucial for identifying rare or emerging pathogens, especially in immunocompromised patients where timely and accurate diagnosis can significantly impact treatment and outcome.
A 62-year-old male kidney transplant recipient presented with a penile ulcer, initially misdiagnosed as herpes simplex. Biopsy revealed granulomatous inflammation, and subsequent PCR confirmed Mycobacterium tuberculosis complex. Further investigation uncovered miliary tuberculosis affecting the lungs, liver, and spleen. The patient, on immunosuppressants, was successfully treated with anti-tuberculous therapy. This case highlights how tuberculosis can present atypically in immunocompromised individuals, with a rare extrapulmonary manifestation like penile involvement being the sentinel sign of disseminated disease. Prompt recognition of unusual presentations is crucial for early diagnosis and management in this vulnerable population. Teaching point: Atypical extrapulmonary tuberculosis can be the first manifestation of disseminated disease in immunocompromised patients, requiring high clinical suspicion.
A patient presented with an infection caused by New Delhi metallo-beta-lactamase (NDM-1)-producing Escherichia coli. This carbapenem-resistant Enterobacterales (CRE) strain exhibited susceptibility to aztreonam, an unusual finding for NDM-1 producers. The diagnosis was confirmed through microbiological testing, identifying the specific NDM-1 enzyme. The infection was successfully managed with aztreonam monotherapy, demonstrating its potential utility in cases where NDM-1 producing organisms retain susceptibility. This case highlights the importance of comprehensive susceptibility testing, as it can reveal unexpected treatment options for highly resistant pathogens. Teaching point: Aztreonam can be an effective treatment for NDM-1-producing E. coli if susceptibility is confirmed, despite typical resistance patterns.
This case report highlights a diagnostic pitfall involving a pediatric patient with suspected cytomegalovirus (CMV) infection, where initial CMV PCR results were false-negative due to viral sequence variation. The patient's clinical presentation and specific symptoms are not detailed in the provided snippet, but the core issue revolves around the unreliability of PCR when viral genetic mutations occur. Subsequent investigation revealed the variant, emphasizing the importance of considering viral genomic diversity in diagnostic testing. Accurate CMV diagnosis is crucial for immunocompromised patients to prevent serious consequences. Teaching point: Viral sequence variations can lead to false-negative PCR results, necessitating careful interpretation and potentially alternative diagnostic methods.
A 59-year-old male with a history of follicular lymphoma presented with fever, pancytopenia, and disseminated lesions, ultimately leading to multi-organ failure. The patient, originally from El Salvador, had recently received chemotherapy. Post-mortem examination and PCR analysis confirmed fulminant reactivation of Trypanosoma cruzi, specifically the TcI genotype, causing widespread amastigote infection in various organs, including the heart and brain. Despite treatment with benznidazole, the infection was fatal. This case highlights the critical importance of considering T. cruzi reactivation in immunocompromised patients from endemic areas, even in the absence of typical Chagas disease symptoms. Teaching point: Chagas disease reactivation in immunocompromised patients can be fulminant and fatal, requiring high clinical suspicion.