A49-32 When the Unlikely Invades: Staphylococcus Haemolyticus Pleuropulmonary Infection in an Aids Patient

Introduction Staphylococcus haemolyticus is a coagulase-negative staphylococcus (CoNS) often regarded as a contaminant in clinical cultures. However, in severely immunocompromised hosts such as individuals with AIDS, this organism can shift from colonizer to invasive pathogen. Among CoNS, S. haemolyticus exhibits extensive multidrug resistance, biofilm formation, and pathogenic potential in bloodstream and prosthetic infections. Pleuropulmonary infections caused by S. haemolyticusare exceptionally rare. This case describes pleural and bloodstream infection by S. haemolyticus in an AIDS patient without prosthetic material, highlighting its emerging role as a true pathogen in deep-seated infection. Case Presentation A 34-year-old man with long-standing untreated HIV presented with one week of pleuritic chest pain, productive cough, fever, and dyspnea. He had been non-adherent to antiretroviral therapy for over one year. On arrival, he was febrile, tachypneic, and hypoxemic, requiring high-flow nasal cannula. Examination revealed decreased right-sided breath sounds. Labs showed WBC 10.9 × 10³/µL, CD4 44 cells/µL, and procalcitonin 16.8 ng/mL. Chest CT demonstrated right-sided necrotizing consolidation, cystic lesions, pleural effusion, and pneumothorax. Initial blood cultures grew Streptococcus pneumoniae; repeat cultures (hospital days 4-6) grew S. haemolyticus in both blood and pleural fluid. No indwelling lines were present. The isolate was resistant to clindamycin and erythromycin but sensitive to vancomycin, levofloxacin, and TMP-SMX. Therapy was escalated to vancomycin plus TMP-SMX, with clinical improvement and clearance of cultures. Discussion CoNS are often dismissed as contaminants, but invasive S. haemolyticus infections occur in immunocompromised hosts even without prosthetic material. Profound CD4 depletion likely facilitated hematogenous spread from mucosal sites to the pleura. The sequential isolation of S. pneumoniae followed by S. haemolyticus suggests polymicrobial or stepwise infection, a pattern seen in late-stage HIV. Recovery following directed therapy supports true pathogenicity. This case expands the spectrum of pulmonary disease attributable to S. haemolyticus and emphasizes that clinical interpretation of CoNS must account for host immune status, infection site, and culture concordance. Conclusion In patients with advanced immunosuppression, S. haemolyticus should not be dismissed as a contaminant when recovered from sterile compartments such as pleural fluid or blood. Recognition of its potential as an invasive pulmonary pathogen is critical to avoid undertreatment. Microbiologic vigilance and individualized antibiotic selection remain essential in managing opportunistic infections in AIDS.