Table 2.

Microbiological profile of IE in PLWH vs. HIV-negative patients

Pathogen / Feature	PLWH (HIV-Positive)	HIV-Negative Patients	Notes / Context
Staphylococcus aureus	24.2–75% of cases; MRSA up to 27.5%, often community-acquired (OR 2.73, 95% CI: 1.30–5.71)	Up to 86% of cases; MRSA ~12.5%	Leading cause in both groups; more MRSA in PLWH
Streptococci	5–14.1%; less frequent than in HIV-negative patients	More frequent; linked to left-sided IE	Non-PLWH studies show Mitis (33%), Pyogenic (17%), S. mitis/oralis, S. agalactiae, S. dysgalactiae, S. gallolyticus common
Enterococci	Rare, but increased in IVDUs over time (1.3% → 4.4%); associated with higher mortality (OR 4.6, p=0.07)	Reported, but less highlighted	Rising trend in IVDUs
Gram-negative bacteria	Atypical organisms frequent (e.g., Bacillus cereus 58.3%, Klebsiella, Micrococcus)	Rare pathogens (e.g., Pseudomonas, H. parainfluenzae, E. corrodens) more in IVDU-IE	Saliva use in IVDU linked to unusual pathogens
Fungi	Candida albicans (1.8%) – rare	Rare (also Candida, sporadic cases)	Low prevalence in both
Polymicrobial infections	Occasional, with culture-negative IE more common (due to immunosuppression)	Seen in IVDU-IE (higher risk of polymicrobial/fungal)	Culture-negative cases rising in some cohorts
IVDU-related trends	Staphylococci predominate; atypical/culture-negative more common in PLWH IVDUs	S. aureus leading cause in IVDUs; longer hospital stays, lower mortality than non-IVDU-IE	IVDU-IE differs from non-IVDU-IE in pathogen profile and outcomes

IE: infective endocarditis, TEE: Transthoracic & Transesophageal Echocardiography (TEE), CA-MRSA: Community-Associated Methicillin-Resistant Staphylococcus Aureus, IVDU: intravenous drug users, PLWH: people living with human immunodeficiency virus, HIV: human immunodeficiency virus