Bartonella elizabethae

Bartonella elizabethae is a gram-negative bacterium primarily found in rats, dogs, and humans, and is transmitted mainly by fleas. It can cause a range of problems, including endocarditis, chronic lymphadenopathy, and severe manifestations like bacillary angiomatosis, particularly in immunocompromised individuals.

What is Bartonella?

Bartonella species are gram-negative bacteria that cause various infections, including cat scratch disease (CSD), trench fever, Oroya fever, and bacillary angiomatosis. These infections are usually spread through fleas, lice, sandflies, or by direct contact with infected animals like cats. 

The most common types of Bartonella infections in humans are caused by Bartonella henselae, Bartonella quintana, and Bartonella bacilliformis, with Bartonella elizabethae also becoming more recognized as a cause. 

Bartonella infections can be hard to diagnose because the bacteria are difficult to grow in labs, but doctors use tests like blood tests and PCR to help. 

While mild infections may not need treatment, more severe cases are treated with antibiotics like azithromycin, doxycycline, and rifampin.

What is Bartonella elizabethae?

Bartonella elizabethae is a species of Bartonella that primarily infects rats, humans, and dogs. It is transmitted via fleas and linked to various human diseases, including culture-negative endocarditis. 

It has been identified in both wild and domestic rodent populations, particularly in areas like Thailand, Georgia, and Kenya. Higher infection rates are observed in urban environments. Fleas from infected rats can spread the bacteria, though the exact transmission mechanisms to humans remain unclear.

This pathogen has been studied in various rodent species, showing significant infection rates in fleas and lice, which serve as vectors. 

Although direct human-to-human transmission via animals is not well-documented, cases of humans infected with Bartonella elizabethae have been reported, especially in populations with close exposure to infected rodents. Bartonella elizabethae infection has been associated with endocarditis.

Further research is needed to understand the full transmission cycle and human health impact of Bartonella elizabethae, especially in urban areas where rodents and ectoparasites are prevalent.

Clinical Significance of Bartonella elizabethae Infection

Bartonella elizabethae (B. elizabethae), primarily associated with rats, can infect humans and dogs, causing conditions like culture-negative endocarditis and chronic lymphadenopathy. It is commonly found in high-risk populations like intravenous drug users.

Symptoms of B. elizabethae infection may include:

• Endocarditis: fever, malaise, and systemic signs. Diagnosis is difficult due to intermittent bacteremia.
• Lymphadenopathy: swollen lymph nodes, common in Bartonella infections.
• Fever and Malaise: these are general symptoms seen in Bartonellosis.
• Neurological Symptoms: headaches, fatigue, and cognitive dysfunction, though these are more commonly seen with other Bartonella species.
• Severe Disease Manifestations: severe manifestations of Bartonellosis, including bacillary angiomatosis and peliosis hepatis, are typically seen in immunocompromised individuals, with symptoms such as vascular proliferative lesions affecting the skin, bones, liver, or spleen, and blood-filled spaces in the liver, often accompanied by systemic signs like fever and malaise. These conditions can lead to significant morbidity, especially in patients with HIV or those receiving organ transplants.

B. elizabethae is transmitted primarily by fleas, with rats acting as a reservoir. The transmission route to humans is not fully understood, but fleas and other ectoparasites are believed to play a key role. 

Given the serious complications and diagnostic challenges, B. elizabethae should be considered in differential diagnoses, particularly for individuals exposed to rats or fleas.

Who Should Get Tested for Bartonella elizabethae?

Testing for Bartonella elizabethae should be considered for individuals with risk factors such as exposure to fleas or rodents, or those who are immunocompromised. These groups are particularly susceptible to Bartonella infections. 

Additionally, testing is recommended for patients presenting with symptoms like prolonged fever, unexplained fatigue, and neurological symptoms such as headache or encephalitis.

It is especially valuable in cases of persistent endocarditis with negative blood cultures or in patients with unexplained systemic infections. Early identification of Bartonella infections can significantly impact the treatment course and outcomes.

Test Procedure and Interpretation

The following section outlines the typical test procedures and results interpretation:

Testing Procedure and Preparation Requirements

Testing for Bartonella elizabethae typically involves collecting blood, tissue samples, or cerebrospinal fluid (CSF). The most common detection methods include PCR (Polymerase Chain Reaction) or serological testing to identify Bartonella DNA or antibodies. 

Various methods can be used to determine the presence of Bartonella organisms:

• Microscopic Stains: Giemsa staining can help identify B. bacilliformis in Oroya fever, while silver stains like Warthin-Starry are used for other types of Bartonella bacteria, though they are not always very specific.
• Cultures: Blood cultures can grow Bartonella species, but this test is not usually used for mild cases and requires a long time (up to 21 days) to get results.
• Serology: Blood tests, like Western blot and measuring IgM/IgG levels, are cost-effective and useful for diagnosing conditions like cat scratch disease and endocarditis, though they may not work as well in people with weak immune systems.
• Polymerase Chain Reaction (PCR): PCR is a very accurate test that finds Bartonella DNA in tissue or fluid samples, especially for conditions like endocarditis, and can still work even if the patient has been treated with antibiotics.

Normal Reference Ranges

In healthy individuals, Bartonella elizabethae biomarkers should be absent or undetectable in blood and CSF. 

Clinical Implications of Elevated Levels

Elevated levels of Bartonella elizabethae biomarkers often indicate active infection or chronic colonization. High levels, especially in tissues like blood or CSF, are strongly associated with infection. 

Additional assessment may be required, including testing for coinfections and imaging studies. 

Clinical Implications of Decreased Levels

Low or undetectable levels may suggest the absence of infection or the successful resolution of an infection following treatment. However, low levels can also occur in the early stages of infection, latent infections, or during the resolving phase. Additionally, serological testing can also demonstrate low levels in immunocompromised patients, regardless of infection status.

As a result, clinicians should be cautious when interpreting low levels and consider the clinical context. It may be necessary to retest patients, particularly if symptoms persist despite negative results.

Order Testing for Bartonella Infections

Click here to compare testing options and order tests for the presence of Bartonella infections.