Overview of Human Brucella

Brucella is a Gram-negative, non-spore-forming small rod-shaped bacterium belonging to the Brucellaceae family within the Proteobacteria phylum. It comprises numerous species that primarily affect livestock and wildlife, and can cause brucellosis in humans. The bacterium has a relatively simple genome with double-stranded DNA, and its high degree of genetic conservation ensures that different Brucella species are genetically very similar. Despite this, they are classified into several groups based on the host animal, such as Brucella melitensis (sheep), Brucella abortus (cattle), and Brucella suis (swine). Brucella is a facultative intracellular pathogen that can infect macrophages and survive long-term within host cells, which contributes to its difficulty in eradication and control.

Morphologically, Brucella appears as small rod-shaped structures measuring 0.5 to 0.7 micrometers in width and 0.6 to 1.5 micrometers in length. It is non-motile and does not produce flagella. It grows slowly and requires special media and prolonged incubation under laboratory conditions. One of Brucella's unique properties is its complex cell wall structure, particularly the lipopolysaccharide (LPS) component, which helps it effectively resist host immune attacks and establishes the foundation for infection.

Epidemiology

Brucellosis is a zoonotic disease that has been prevalent in human societies since the domestication of livestock. Symptoms related to Brucella were recorded as early as the late 19th century, and the disease is closely associated with livestock. Humans typically become infected through direct contact with infected animals or by consuming inadequately processed dairy products. Although industrialized countries have successfully reduced the prevalence of brucellosis through stringent control measures, it remains a serious public health issue in some developing regions, including the Middle East, the Mediterranean, Sub-Saharan Africa, Central Asia, and Latin America.

Globally, there are approximately 500,000 new cases of brucellosis each year, with the actual incidence potentially being higher due to undiagnosed cases. The prevalence of brucellosis is closely related to Brucella infection in livestock, and contact with animals such as sheep, cattle, and pigs significantly increases the risk of infection.

Figure 1. Heatmap of annual incidence per 1 million high-risk individuals in different regions
(Source: Laine CG, et al., 2023)

Diagnosis and Control

Diagnosing brucellosis presents challenges due to its symptom similarity with other diseases and the slow growth of the bacterium. Traditional diagnostic methods often require a combination of techniques. Microbiological culture is the gold standard for confirming Brucella infection, but due to the slow growth of Brucella and high laboratory requirements, cultures typically take several days to weeks. Blood or tissue cultures are the most direct methods for identifying the infecting Brucella species.

In addition to culture, serological testing is also an important diagnostic tool for brucellosis. Common serological tests include agglutination tests and ELISA (enzyme-linked immunosorbent assay), which detect antibody responses in the serum to confirm infection. However, serological tests may result in false negatives due to low antibody levels or prolonged infection duration. Recently, nucleic acid amplification technologies (e.g., PCR) have been widely used for the rapid diagnosis of brucellosis. These technologies offer high sensitivity and specificity, enabling early detection of the pathogen.

Figure 3. Diagnostic algorithm for human brucellosis
(Source: Di Bonaventura G, et al., 2021)

In terms of prevention and control, managing brucellosis primarily involves controlling infections in animals. Regular screening, vaccination, and culling of infected animals are effective measures to reduce Brucella transmission. In high-risk areas, controlling the distribution of untreated dairy products and enhancing public health education are also important preventive measures. Additionally, individuals at occupational risk, such as veterinarians and farm workers, should implement protective measures to minimize direct contact with infected animals.

In summary, Brucella, as a facultative intracellular pathogen, possesses significant infectious capability and adaptability. Its widespread prevalence in humans and animals makes it a global public health threat. Early diagnosis, appropriate antibiotic treatment, and effective control measures in animals can significantly reduce the incidence and transmission risk of brucellosis. Creative Diagnostics provides a wide choice of high-quality Brucella research supplies, including antigens, antibodies, and assay kits, to ensure the accuracy of your experiments. You may also find our related products such as B. canis and B. abortus. Please visit the product page for additional information.

Brucella ELISA Kits

Brucella Antibodies

B. abortus Antigens