Staphylococcus aureus ; Definition, Habitat, Infections, Resistance & Risks, Prevention & Treatment

Описание: 🦠 Staphylococcus aureus is a Gram-positive, coagulase-positive, facultative anaerobic coccus that forms grape-like clusters under the microscope. It’s a major human pathogen responsible for a wide range of infections—from mild skin conditions to life-threatening systemic diseases.

🔬 Key Characteristics
Gram-positive cocci in clusters

Catalase-positive, coagulase-positive

Beta-hemolytic on blood agar (clear zone of hemolysis)

Non-motile, non-spore-forming

Golden-yellow colonies on nutrient agar (hence the name aureus, meaning “golden”)

🧫 Where It’s Found
Skin, nasal passages, and mucous membranes of healthy individuals

Hospital environments, especially on medical devices and surfaces

Food products, where it can cause foodborne illness

🧪 Clinical Significance
Infection Type Examples
Skin & soft tissue Boils, impetigo, cellulitis, abscesses
Invasive infections Bacteremia, endocarditis, osteomyelitis, pneumonia
Toxin-mediated Toxic shock syndrome, scalded skin syndrome, food poisoning
Device-related Catheter infections, prosthetic joint infections
🧬 Virulence Factors
Protein A: Binds Fc region of IgG, evading immune detection

Coagulase: Clots plasma, helping shield bacteria from immune cells

Hemolysins & leukocidins: Destroy red and white blood cells

Exotoxins: Like TSST-1 (toxic shock syndrome toxin) and enterotoxins (cause food poisoning)

Biofilm formation: Especially on medical devices

💊 Treatment
Methicillin-sensitive strains (MSSA): Treated with nafcillin, oxacillin, or cefazolin

Methicillin-resistant strains (MRSA): Require vancomycin, linezolid, daptomycin, or clindamycin

Drainage of abscesses is often necessary

Infection control in hospitals is critical to prevent spread

🧠 Fun Fact
S. aureus was one of the first bacteria in which antibiotic resistance became a major clinical problem—leading to the emergence of MRSA, a global public health concern

#Staphylococcus