Staphylococcus aureus

Classification

Kingdom: Bacteria
Phylum: Firmicutes
Class: Bacilli
Order: Bacillales
Family: Staphylococcaceae
Genus: Staphylococcus
Species: Staphylococcus aureus

Morphology

Shape: Cocci (spherical)
Size: ~0.5-1.0 μm in diameter
Gram Stain: Gram-positive
Arrangement: Clusters (grape-like)
Motility: Non-motile
Special Features: Produces coagulase and catalase, forms golden-yellow colonies

Habitat & Distribution

Natural Habitat: Human skin and mucous membranes
Geographic Distribution: Worldwide
Human Association: Opportunistic pathogen
Transmission: Direct contact, contaminated surfaces, airborne droplets

Staphylococcus aureus is an opportunistic pathogen capable of causing a wide range of infections, from superficial skin infections to life-threatening conditions.

Virulence Factors: Protein A, coagulase, hemolysins, exotoxins
Associated Diseases: Skin infections, pneumonia, bacteremia, toxic shock syndrome
Clinical Symptoms: Abscesses, fever, swelling, redness, systemic symptoms in severe infections
High-Risk Groups: Immunocompromised individuals, hospitalized patients, people with chronic conditions

It is a major concern in healthcare settings due to its ability to develop resistance, leading to MRSA strains.

The diagnosis of Staphylococcus aureus infections relies on clinical assessment and laboratory confirmation.

Diagnostic Methods

Culture: Growth on Mannitol Salt Agar, blood agar
Microscopy: Gram staining shows Gram-positive cocci in clusters
Molecular Testing: PCR for mecA gene in MRSA detection
Serology: Not commonly used

Treatment Approaches

First-line Treatments: Beta-lactam antibiotics for MSSA
Alternative Therapies: Vancomycin, daptomycin for MRSA
Antimicrobial Resistance: MRSA strains are resistant to beta-lactams
Supportive Care: Wound drainage, intravenous fluids for severe cases

Prevention Strategies

Hand hygiene and proper sanitation
Wound care and proper bandaging
Prudent use of antibiotics to prevent resistance

Preventing Staphylococcus aureus infections relies heavily on hygiene and infection control measures, especially in hospital settings.

Global Impact

Staphylococcus aureus, particularly MRSA strains, is a major public health threat worldwide.

33%

About one in three people carry S. aureus bacteria in their nose, and about 2% carry MRSA.

Although many people carry MRSA bacteria in their nose, most do not develop serious MRSA infections.