Staphylococcus haemolyticus is a bacterium commonly found on human skin. While usually harmless, it can become an opportunistic pathogen capable of causing serious infections, particularly in healthcare environments.
Identifying Staphylococcus haemolyticus
Staphylococcus haemolyticus belongs to coagulase-negative staphylococci (CoNS). Unlike Staphylococcus aureus, CoNS do not produce the enzyme coagulase, involved in blood clotting. S. haemolyticus is the second most frequently isolated CoNS from clinical infections, after Staphylococcus epidermidis.
Under a microscope, Staphylococcus haemolyticus appears as spherical cells (cocci), typically 0.8 to 1.3 micrometers in diameter, often arranged in irregular, grape-like clusters. It is a Gram-positive bacterium, meaning it retains a purple stain during a common laboratory test due to its thick cell wall.
This bacterium is a facultative anaerobe, meaning it can grow in both the presence and absence of oxygen. S. haemolyticus is a common part of human skin flora, with its largest populations found in moist areas such as the armpits, perineum, and groin. It can also colonize mucous membranes.
When it Becomes a Problem
While Staphylococcus haemolyticus usually coexists harmlessly with humans, it can become an opportunistic pathogen. This means it causes infections when the body’s natural defenses are weakened or physical barriers, like the skin, are breached.
Several factors increase the risk of S. haemolyticus infection. Medical devices, such as catheters, prosthetic joints, heart valves, or cerebrospinal fluid shunts, significantly elevate this risk. Patients with weakened immune systems, those hospitalized, or undergoing surgical procedures are also more susceptible. Prolonged antibiotic use can further contribute to its opportunistic nature.
A significant factor contributing to its ability to cause disease is its capacity to form biofilms. These are communities of bacteria embedded in a slimy matrix that adhere to surfaces, especially medical devices. Biofilms make the bacteria more resistant to antibiotics and the body’s immune responses, leading to persistent infections.
Infections It Causes
Staphylococcus haemolyticus can cause various infections, particularly in healthcare settings. Bloodstream infections (bacteremia), often associated with central venous catheters, are a significant type. These can lead to serious complications, especially in immunocompromised patients.
Infections related to prosthetic devices are another common manifestation, including artificial joints, heart valves, and other implanted medical hardware. The bacterium’s ability to form biofilms on these devices contributes to the challenge of treating these infections.
Urinary tract infections (UTIs) can also be caused by S. haemolyticus, particularly in individuals with urinary catheters or undergoing urological procedures. Symptoms of UTIs can include painful urination, increased frequency, urgency, and cloudy urine.
Although less common than other Staphylococcus species, S. haemolyticus can also be involved in skin and soft tissue infections, especially in immunocompromised patients. General symptoms associated with S. haemolyticus infections can include fever, chills, and localized pain or redness, depending on the site of infection.
Managing Infections
Diagnosing a Staphylococcus haemolyticus infection involves culturing samples from the suspected infection site, such as blood, urine, or tissue. Once isolated, the bacterium can be identified through its characteristic growth patterns and biochemical tests. This helps confirm the presence of S. haemolyticus and rule out other similar bacteria.
Treatment of S. haemolyticus infections primarily involves antibiotics. However, a significant challenge is the bacterium’s high rate of antibiotic resistance. S. haemolyticus often exhibits resistance to multiple antibiotics, including methicillin, leading to strains known as methicillin-resistant Staphylococcus haemolyticus (MRSH). This resistance means many commonly used antibiotics may not be effective.
Due to this widespread resistance, antibiotic susceptibility testing is an important step. This laboratory test determines which specific antibiotics will be effective against the isolated S. haemolyticus strain. Treatment decisions are guided by these results, often requiring the use of last-resort antibiotics like vancomycin or linezolid for resistant strains.
Beyond antibiotic therapy, infection control and prevention measures are important, especially in healthcare settings. These include strict hand hygiene, proper sterilization techniques for medical devices, and careful management of indwelling catheters. These practices help limit the spread of S. haemolyticus and reduce the incidence of healthcare-associated infections.