Background

Microscopic view of Staphylococcus spp. collected during CHP study.

Staphylococci are Gram-positive, spherical bacteria measuring approximately 0.5–1.5 μm in diameter. They divide in multiple planes, forming characteristic grape-like clusters when viewed under a microscope. These bacteria are non-motile, non-spore-forming, and catalase-positive. Staphylococci commonly colonize the human body, with the anterior nares (nose) serving as the primary reservoir, while the skin and intestines are also frequent colonisation sites. Although colonization is often harmless, it may increase the risk of invasive infections. Clinically, staphylococci are associated with a wide range of diseases, including impetigo, furuncles and carbuncles, wound infections, staphylococcal scalded skin syndrome, toxic shock syndrome, and food intoxication.

Staphylococci are classified based on their ability to produce the enzyme coagulase into coagulase-positive staphylococci (CoPS), such as Staphylococcus aureus, and coagulase-negative staphylococci (CoNS), such as Staphylococcus epidermidis.

Coagulase-Positive Staphylococci

Staphylococcus aureus – the most important human pathogen; causes skin infections, pneumonia, bacteremia, and toxic shock syndrome.
Staphylococcus pseudintermedius – commonly associated with dogs; occasionally infects humans.
Staphylococcus intermedius – primarily found in animals, rare in humans.
Staphylococcus hyicus – mainly an animal pathogen.
Staphylococcus delphini – associated with marine mammals and other animals; uncommon in humans.

Coagulase-Negative Staphylococci

Staphylococcus epidermidis – the most common CoNS; associated with catheter and prosthetic device infections.
Staphylococcus saprophyticus – a common cause of urinary tract infections in young women.
Staphylococcus haemolyticus – often multidrug-resistant and associated with hospital-acquired infections.
Staphylococcus hominis – part of normal skin flora; opportunistic pathogen.
Staphylococcus lugdunensis – although coagulase-negative, it can cause severe infections resembling those caused by S. aureus.

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