Staphylococcus hominis is a Gram-positive, coagulase-negative bacterium commonly found on human skin. While generally a harmless resident of the skin’s natural microbial community, it can become an opportunistic pathogen when the body’s defenses are compromised or it gains access to internal tissues.
A Normal Skin Dweller
Staphylococcus hominis is a prominent component of the normal human skin flora. It is particularly abundant in areas rich in apocrine glands, such as the armpits and pubic region, where moisture is retained. In one study, S. hominis accounted for approximately 22% of all Staphylococcus species recovered from human skin, making it the second most frequently isolated coagulase-negative Staphylococcus after Staphylococcus epidermidis.
This bacterium contributes to the skin’s microbial ecosystem and can play a protective role. Research suggests that S. hominis can produce molecules that inhibit the growth of harmful bacteria, such as Staphylococcus aureus, thereby helping to maintain skin health. While individual strains may colonize the skin for shorter periods, typically several weeks to months, its widespread presence highlights its common and generally benign association with humans.
When It Causes Problems
While Staphylococcus hominis is often harmless, it can become an opportunistic pathogen, particularly in individuals with weakened immune systems or those in healthcare settings. Factors facilitating infection include compromised skin barriers, such as surgical wounds, cuts, or medical device insertion. Foreign materials like catheters, prosthetic joints, or artificial heart valves can provide surfaces where S. hominis can form biofilms, making bacterial clearance difficult for the immune system and antibiotics.
Skin and soft tissue infections are possible, though more severe infections can occur, especially in hospitalized patients. These may include bloodstream infections (bacteremia) and infections related to medical implants. Endocarditis, an infection of the heart’s inner lining, has also been associated with S. hominis, particularly with artificial valves. Symptoms of these infections can vary depending on the site but may include fever, redness, swelling, pain, or signs of systemic illness.
Addressing Infections and Resistance
Diagnosing Staphylococcus hominis infections involves collecting samples from the suspected infection site, such as blood cultures or pus aspirates, and then identifying the bacterium through laboratory tests. These tests include bacterial culture and biochemical analysis, followed by antibiotic susceptibility testing to determine effective antibiotics. This step is important because S. hominis strains can exhibit varying resistance patterns.
Treatment involves antibiotics, but a concern is antibiotic resistance. Some strains of S. hominis have developed resistance to multiple antibiotics, including methicillin, known as Methicillin-Resistant Staphylococcus hominis (MRSH). This resistance can complicate treatment choices, making common antibiotics ineffective. Vancomycin, linezolid, or daptomycin are considered for methicillin-resistant strains, while methicillin-susceptible strains respond to beta-lactam antibiotics such as oxacillin or cefazolin. Proper antibiotic stewardship is important to preserve the effectiveness of available treatments.
Steps for Prevention
Preventing Staphylococcus hominis infections involves maintaining good hygiene and protecting skin integrity. Regular handwashing, especially before and after caring for wounds or handling medical devices, reduces the spread of bacteria. Proper wound care, including cleaning and covering cuts or abrasions, prevents S. hominis from entering deeper tissues. Keeping the skin healthy and moisturized helps maintain its natural barrier function. In healthcare environments, strict adherence to infection control protocols minimizes the risk of healthcare-associated infections, particularly for vulnerable patients with medical devices or compromised immune systems.