Lactobacillus jensenii is an anaerobic, Gram-positive, rod-shaped bacillus belonging to the Lactobacillus genus, a classification of lactic acid bacteria. It is an integral part of the human microbiome, particularly in the female reproductive tract. This organism’s primary function is fermenting carbohydrates into lactic acid, a process that shapes the environment where it resides.
The Commensal Nature of Lactobacillus jensenii
Lactobacillus jensenii is a dominant species found in a healthy vaginal ecosystem, maintaining a protective environment within the lower reproductive tract. It is often the second most prevalent Lactobacillus species, following Lactobacillus crispatus. The protective mechanism centers on the production of lactic acid, which keeps the vaginal pH stable and acidic, typically between 3.5 and 4.5. This low-pH environment inhibits the colonization and growth of many harmful microorganisms. L. jensenii also produces compounds like hydrogen peroxide. By attaching to the vaginal epithelial cells, this species forms a protective barrier, actively competing with unwelcome bacteria and yeast for nutrients and space.
When Lactobacillus jensenii Causes Disease
While generally a beneficial resident, Lactobacillus jensenii can transition into an opportunistic pathogen, causing infection when host defenses are compromised or when the bacteria migrate from their usual habitat to sterile body sites. The types of infections associated with L. jensenii are typically rare but can be quite severe, including systemic issues like bacteremia and endocarditis. Less severe, localized infections include pyelonephritis and abscesses in the renal or perinephric tissues. Risk factors that predispose an individual to these infections include a compromised immune system, the presence of prosthetic heart valves, or recent genitourinary instrumentation. In some cases, the use of probiotics containing Lactobacillus species has also been identified as a potential, though rare, source of systemic infection. Furthermore, research has linked the presence of specific strains of L. jensenii in the vaginal microbiome to an increased risk of adverse pregnancy outcomes, such as preterm birth.
Methods for Identifying the Infection
Confirming an infection caused by L. jensenii requires precise laboratory methods because it is a common commensal organism. The diagnostic process begins with collecting samples from the suspected site of infection, such as blood cultures, urine samples, or tissue from an abscess. Since Lactobacillus species are generally slow-growing, specialized culture media are often required for optimal isolation. Initial identification involves Gram staining, which confirms Gram-positive, rod-shaped bacteria. However, distinguishing pathogenic L. jensenii from other non-harmful Lactobacillus species requires more advanced techniques. Species-level identification is typically achieved using molecular methods, such as Polymerase Chain Reaction (PCR) or 16S ribosomal RNA gene sequencing. Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) mass spectrometry provides rapid and accurate species identification by analyzing the protein profile of the isolate. Precise identification is necessary to ensure the correct organism is targeted for treatment.
Management and Treatment Protocols
Treatment for symptomatic Lactobacillus jensenii infection relies on antibiotic therapy guided by susceptibility testing performed on the isolated bacterial strain. This testing is necessary because Lactobacillus species vary in their response to antimicrobial agents. L. jensenii is generally susceptible to broad-spectrum agents like ampicillin or high-dose penicillin. For serious infections, such as endocarditis or bacteremia, combination therapy is often employed, typically involving a beta-lactam antibiotic, such as penicillin, combined with an aminoglycoside like gentamicin. A challenge in treating Lactobacillus infections is their intrinsic resistance to vancomycin, though L. jensenii can show variable susceptibility, necessitating careful testing. In cases of severe infection or when the isolate is resistant to first-line agents, alternative combinations, such as teicoplanin and meropenem, may be used. Following the successful elimination of the infection, restoring the healthy balance of the native flora is important, sometimes using targeted probiotics.