Staphylococcus lugdunensis is a bacterium commonly found on human skin that can cause serious infections. Though classified as a coagulase-negative staphylococcus (CoNS), it is more aggressive than most other CoNS species. It often behaves like Staphylococcus aureus in its capacity to induce severe disease.
Unique Features and Where It Lives
Staphylococcus lugdunensis belongs to the coagulase-negative staphylococci group, but its virulence profile is distinct. Unlike many other CoNS, it produces a cell-bound coagulase, which can cause it to be mistaken for Staphylococcus aureus in rapid laboratory tests.
This bacterium primarily inhabits human skin, particularly in areas characterized by moisture and thinner skin layers. Such locations include the groin, perineum, axillae, and the nail beds of the first toe. Its frequent presence in these lower body regions has earned it the informal description of a “below the belt” colonizer.
Laboratory identification relies on specific biochemical markers. S. lugdunensis tests positive for pyrrolidonyl arylamidase (PYR) and ornithine decarboxylase, distinguishing it from other staphylococcal species. On culture media, it produces a distinctive odor and exhibits beta-hemolysis. S. lugdunensis also forms biofilms, which are communities of bacteria encased in a protective matrix that adheres to surfaces.
Health Problems It Can Cause
Staphylococcus lugdunensis can cause a wide range of infections, often mimicking the severity of Staphylococcus aureus. Skin and soft tissue infections (SSTIs) are common, including abscesses, cellulitis, infected wounds, and paronychias.
Beyond superficial infections, S. lugdunensis can lead to more invasive conditions like bone and joint infections. These include osteomyelitis (bone infection) and septic arthritis (joint inflammation), especially in prosthetic joints. Infections related to prosthetic devices, such as catheters, pacemakers, and artificial heart valves, are also reported.
One of the most severe infections caused by S. lugdunensis is infective endocarditis, an inflammation of the heart’s inner lining, often involving heart valves. This form of endocarditis is recognized for its aggressive course, frequently leading to significant valve destruction and a high mortality rate, which can reach up to 40% for native valves and 78% for prosthetic valves. Although less common, urinary tract infections have also been attributed to this bacterium. The ability of S. lugdunensis to form biofilms on various surfaces, including medical devices, significantly contributes to its persistence and makes these infections challenging to eliminate. Biofilms protect bacteria from antibiotics and the body’s immune responses, complicating treatment efforts.
Identifying and Managing Infections
Accurate identification of Staphylococcus lugdunensis is a crucial step in managing infections, given its unique virulence among coagulase-negative staphylococci. Diagnosis typically begins with culturing samples collected from the infected site, such as blood, wound swabs, urine, or tissue biopsies. Precise laboratory identification is important to differentiate it from other CoNS, as its clinical significance and treatment approach often differ.
Specific biochemical tests aid in this differentiation, including positive reactions for pyrrolidonyl arylamidase and ornithine decarboxylase. Advanced methods like Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) or Polymerase Chain Reaction (PCR) are increasingly used for definitive species-level identification. It is noteworthy that S. lugdunensis can sometimes be misidentified as Staphylococcus aureus in rapid coagulase tests due to its production of a bound coagulase.
Treatment primarily involves antibiotic therapy. S. lugdunensis generally remains susceptible to a range of antibiotics, including beta-lactam antibiotics like penicillin and cephalosporins. However, resistance can occur, particularly to penicillin, with reported rates varying globally from 15% to 87%, necessitating antibiotic susceptibility testing to guide treatment choices. For resistant strains, or when resistance patterns are unknown, alternative antibiotics such as vancomycin, trimethoprim-sulfamethoxazole, tetracycline, or clindamycin may be considered. Beyond antibiotics, non-antibiotic interventions, such as surgical drainage of abscesses or the removal of infected prosthetic devices, are often necessary for successful treatment, especially in cases where biofilms contribute to infection persistence.