Staphylococcus aureus, a Gram-positive bacterium, manifests as non-motile, small, round cocci typically found in clusters resembling grapes. Its name derives from this cluster formation. Who does it affect? Staphylococcus aureus ranks among the top five culprits for post-injury or post-surgery infections, impacting approximately 500,000 patients annually in American healthcare settings. In medical literature, it’s often abbreviated as “S. aureus” or “Staph aureus.”
The bacterium was first identified in Aberdeen, Scotland in 1880 by surgeon Sir Alexander Ogston in pus samples from surgical abscesses. Staphylococcus aureus belongs to the Staphylococcaceae family, affecting a broad range of mammalian species, including humans. Its versatility enables easy transmission between species, including humans and animals.
Transmission of Staphylococcus aureus S. aureus commonly lurks in the environment and spreads through air droplets or aerosols. When an infected individual coughs or sneezes, tiny droplets containing the bacteria may remain airborne, posing an infection risk to others. Another common transmission route involves direct contact with contaminated objects or through bites from infected individuals or animals. Approximately 30% of healthy individuals harbor S. aureus in their nasal passages, throat, and on their skin. Clinical manifestation of infection Although about one-third of healthy individuals carry S. aureus without exhibiting symptoms, colonization typically doesn’t lead to disease in immunocompetent individuals.
However, when it causes infection, S. aureus typically invades wounds as a secondary agent rather than being the primary cause. It’s commonly isolated from abscesses, skin lesions, breast abscesses, mastitis, dermatitis, and genital tract infections. S. aureus is considered an opportunistic pathogen, exploiting compromised skin or other entry points to cause infection. In immunocompromised individuals, it can lead to life-threatening pyogenic infections affecting the skin, eyes, genital tract, and other areas. What does S. aureus cause? S. aureus can cause a variety of manifestations, including minor skin infections like pimples and impetigo, as well as more severe conditions such as boils, cellulitis, folliculitis, carbuncles, scalded skin syndrome, abscesses, pneumonia, meningitis, osteomyelitis, endocarditis, and systemic infections like toxic shock syndrome, bacteremia, and septicemia.
Diagnosis Culturing S. aureus from clinical samples isn’t necessarily significant since it’s commonly present on the skin, nasal passages, and throat of many humans and animals. However, it can be cultured from suspicious lesions, nasopharyngeal swabs, or skin samples. On culture, S. aureus colonies exhibit a distinctive glistening, opaque, yellow to white appearance on blood agar.
