Streptococcus lutetiensis is a bacterium that often lives harmlessly within the human body, yet it can also contribute to various health concerns. This article explores its characteristics, common habitats, and potential health implications.
What is Streptococcus lutetiensis?
Streptococcus lutetiensis is a Gram-positive, facultative anaerobic coccus. It retains a purple stain in a Gram stain test, indicating its cell wall structure. Its spherical shape is why it’s called a “coccus,” and “facultative anaerobic” means it can grow with or without oxygen, adapting to various body environments.
The bacterium was officially recognized and named Streptococcus lutetiensis in 2002 by Poyart et al., following detailed genetic analysis. It was previously known as Streptococcus bovis type II/1 and Streptococcus infantarius subsp. coli.
Where is Streptococcus lutetiensis Found?
Streptococcus lutetiensis is commonly found as a normal resident, or commensal organism, within the human body. Its primary habitats include the gastrointestinal tract, the urogenital tract, and the oral cavity. In these locations, it typically coexists with other microorganisms without causing harm, forming part of the complex human microbiota.
The presence of S. lutetiensis is not limited to humans; it has also been isolated from animals, including dairy cows where it can cause mastitis. Some strains have been found in food products like fermented milk and fish, suggesting its adaptability to various environments.
Health Implications of Streptococcus lutetiensis
While Streptococcus lutetiensis typically lives harmlessly in the body, it can act as an opportunistic pathogen, meaning it can cause infection when conditions are favorable, such as when the immune system is weakened or when it gains access to parts of the body it doesn’t normally inhabit. This bacterium has been linked to several health conditions. Its association with colorectal cancer is particularly notable, with higher incidences reported in patients with this condition.
S. lutetiensis can cause bacteremia, which is the presence of bacteria in the bloodstream. This can lead to more serious conditions like infective endocarditis, an inflammation of the heart’s inner lining, especially in individuals with pre-existing heart conditions. Urinary tract infections (UTIs) are another common infection linked to S. lutetiensis, as it can enter the urinary tract from its normal habitat in the gastrointestinal tract.
In some rare instances, S. lutetiensis has been implicated in neonatal infections, including sepsis and meningitis, although such cases are not commonly reported. The bacterium’s ability to transition from a harmless commensal to a pathogen often involves a disruption of the mucosal barriers in the gastrointestinal tract, allowing it to enter the bloodstream and spread to other parts of the body. This translocation can lead to infections in various organs, including prosthetic joints, where it can form biofilms.
Diagnosing and Treating Streptococcus lutetiensis Infections
Diagnosing infections caused by Streptococcus lutetiensis typically involves identifying the bacterium from patient samples. Bacterial culture is a primary method, where samples such as blood, urine, or cerebrospinal fluid are grown in a laboratory to allow the bacteria to multiply, making them easier to detect. Once cultured, microscopy can be used to observe the bacteria’s characteristic spherical shape and Gram-positive staining.
Molecular tests, such as PCR (polymerase chain reaction) for detecting specific genes like the 16S rRNA gene, can provide a more definitive identification of S. lutetiensis. Additionally, matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry can be used for rapid and accurate identification. Once an infection is confirmed and the specific bacterium is identified, treatment generally involves antibiotic therapies.
The choice of antibiotic depends on the susceptibility of the particular S. lutetiensis strain, as resistance to certain antibiotics like erythromycin and clindamycin has been reported. For instance, some isolates have shown good sensitivity to vancomycin. Early diagnosis and appropriate antibiotic treatment are important for managing these infections and improving patient outcomes, especially given the potential for serious complications like endocarditis or prosthetic joint infections.