The bacterium Globicatella sanguinis is a rare, Gram-positive coccus that has emerged as a cause of severe human infections. It belongs to a lineage of bacteria known for being difficult to identify using traditional laboratory methods. The organism was first isolated and established as a new species and genus in 1992 following detailed analysis of clinical isolates that had previously been misidentified. This classification revealed a previously unrecognized opportunistic pathogen often linked to serious, life-threatening conditions.
Biological Profile and Characteristics
Globicatella sanguinis is taxonomically classified within the phylum Bacillota, a group that also includes common bacteria like Streptococcus and Enterococcus. Morphologically, it presents as ovoid, Gram-positive cocci that typically arrange themselves in short chains or pairs. It is a catalase-negative organism, which helps differentiate it from some other Gram-positive cocci.
When cultured, G. sanguinis often exhibits alpha-hemolysis on blood agar, meaning it partially breaks down red blood cells and gives colonies a greenish hue. It is considered a facultatively anaerobic bacterium, capable of growing with or without oxygen. Phenotypically, the organism closely resembles viridans group streptococci and Aerococcus species, contributing to its history of misidentification.
Specific biochemical tests are necessary to confirm its identity. G. sanguinis strains are generally positive for the bile esculin test and can tolerate growth in media containing 6.5% sodium chloride. Conversely, it is typically negative for the leucine aminopeptidase (LAP) reaction, a characteristic that differentiates it from certain other streptococcus-like bacteria.
Clinical Spectrum of Infection
Infection with G. sanguinis is associated with a range of invasive and potentially life-threatening diseases. The most frequently reported presentation is bacteremia, an infection of the bloodstream that can rapidly progress to sepsis. Symptoms usually include high fever, chills, and a severe systemic response.
The bacterium has an affinity for the lining of the heart, making it a known cause of infective endocarditis. This infection of the heart’s inner lining or valves can cause significant structural damage. Patients may experience prolonged fever, fatigue, and the development of a new or changing heart murmur.
G. sanguinis also causes localized infections beyond the bloodstream and heart. Cases have been documented involving the central nervous system, leading to meningitis. Furthermore, it is a sporadic cause of urinary tract infections (UTIs) and has been implicated in deep tissue infections like osteomyelitis.
Vulnerable Populations and Acquisition
Infections caused by G. sanguinis are opportunistic, primarily affecting individuals whose body defenses are weakened or compromised. The infection disproportionately affects patients at the extremes of age, including infants under five and adults over 65 years old. The majority of reported cases have occurred in females, though the reason for this gender bias is not fully understood.
Underlying medical conditions significantly increase the risk of contracting the infection. Chronic illnesses such as diabetes mellitus, cancer, or pre-existing heart valve abnormalities predispose individuals to invasive disease. Conditions resulting in a compromised immune system, such as immunosuppressive therapy, also increase susceptibility.
The exact natural reservoir of G. sanguinis is still being investigated, but it is suspected to colonize human mucosal surfaces, particularly the urogenital or lower gastrointestinal tracts. Acquisition occurs when the bacterium breaches these natural barriers to enter the bloodstream, often following a medical procedure or due to mucosal integrity breakdown. The pathogen has also been linked to infections associated with foreign materials, such as prosthetic joints or ventriculoperitoneal shunts.
Identification and Management
Identification
Accurately identifying G. sanguinis is challenging due to its phenotypic resemblance to more common bacteria. Traditional laboratory methods relying on biochemical reactions frequently misidentify the organism as a member of the viridans group streptococci. This difficulty can lead to delays in appropriate treatment.
The most reliable confirmation relies on advanced molecular techniques. Laboratory specialists use 16S ribosomal RNA (rRNA) gene sequencing to identify the genus, often requiring sequencing of the sodA gene for species-level confirmation. Modern mass spectrometry techniques, such as MALDI-TOF MS, are also increasingly used for rapid and accurate identification.
Treatment
Management of G. sanguinis infection must be guided by antibiotic susceptibility testing, given the organism’s unpredictable resistance profile. For serious infections like bacteremia or endocarditis, the preferred initial treatment is often a combination of antibiotics. This typically involves Penicillin G or ampicillin combined with an aminoglycoside like gentamicin, as penicillin susceptibility is generally maintained.
A clinical concern is the organism’s elevated Minimum Inhibitory Concentrations (MICs) to third-generation cephalosporins (e.g., ceftriaxone and cefotaxime). This resistance pattern means that standard empirical therapy for a streptococcal-like infection may fail. For patients with a penicillin allergy, vancomycin is typically used in combination with gentamicin as an alternative regimen. Therapy duration is extended, often lasting four to six weeks, particularly for endocarditis or infections involving prosthetic materials.