Bacillus thuringiensis from Gladiolus

Burkholderia gladioli, a name that may sound unfamiliar, is indeed a "newcomer" in the world of laboratory animals. However, in the food industry, it’s a bacterium that has drawn significant attention. Widely found in natural environments such as soil and water sources, as well as in hospital settings and food products like tremella mushrooms, Burkholderia gladioli exhibits highly complex pathogenic properties. Foodborne outbreaks caused by this bacterium have occasionally occurred in China. To ensure food safety, GB 4789.29-2020, the "National Food Safety Standard—Microbiological Examination of Foods: Detection of Burkholderia gladioli (Pseudomonas cocovenenans subsp. farinofermentans)," outlines specific testing methods for this bacterium.

So, in experimental animals, what are the effects of Burkholderia gladioli on animal health and scientific research? This article will introduce them one by one.

Burkholderia gladioli is an aerobic, motile, non-fermentative Gram-negative bacillus that was initially identified in 1921 as a plant pathogen affecting gladiolus and other flowering plants. This bacterium can be found in soil, water in the environment, as well as on plants and fruits. As a commensal organism, it may cause pneumonia, bacteremia, chronic granulomatous disease, and can ultimately lead to death in immunocompromised patients. Hospital-acquired infections are often linked to contaminated water sources.

Burkholderia species, with their versatile metabolism, ability to produce a variety of virulence factors, and capacity to form biofilms, are well-equipped to thrive in harsh environmental conditions. Consequently, Burkholderia glumae, as an environmental bacterium, primarily spreads through direct contact. In immunocompromised mice exhibiting head-tilting symptoms, Burkholderia glumae is often detected in their drinking tubes and water bottles.

In 2004, an institution in Virginia reported an outbreak of otitis media caused by Burkholderia gladioli in immunocompromised mice, and a similar epidemic occurred in 2007 at a facility in France. In 2019, U.S. researchers found that infections with Burkholderia gladioli could be linked to automatic drinking systems, water bottles, and bottle straws. Our company’s testing data from 2020 to 2022 revealed that a domestic CRO organization detected a 3.1% positivity rate in biological products such as tumor cells—cells that, when transplanted into mice, not only induced illness but even led to mortality in the animals. Additionally, a 10.3% positivity rate was observed among laboratory mice used in experiments. These findings clearly demonstrate that Burkholderia gladioli infections pose a significant threat, whether in environmental samples, biological products, or experimental animals—both domestically and internationally.

In most cases, rodent experimental animals infected with Burkholderia gladioli show no obvious clinical symptoms. However, in immunocompromised mice, symptoms such as head tilting, circling, and rolling—characteristic of otitis media—along with weight loss, hunched posture, lethargy, dehydration, ataxia, and rotational movements when the tail is lifted may appear.

An autopsy revealed purulent infection in the ear canal, characterized by extensive neutrophil infiltration, with few lymphocytes and only a small number of macrophages and plasma cells. Vascular congestion was also observed, along with inflammatory changes in the dermis and subcutaneous layers. Additionally, the liver exhibited abscesses, with lesions ranging from no associated pathology to mild subacute vasculitis, progressing to necrotizing suppurative hepatitis. Lung involvement included mild vascular congestion and mild acute interstitial pneumonia in some mice.

If animals are infected with Burkholderia gladioli, especially immunocompromised ones, they may exhibit symptoms of otitis media, such as head tilting. Additionally, the liver can develop lesions characterized by neutrophil infiltration, while lymphocyte numbers remain low, with only a few macrophages and plasma cells present. These pathological changes can significantly impact behavioral, cellular, and liver-related research. In the context of PDX tumor studies, the infection may also affect the animals' survival time and tumor data. Moreover, inflammatory responses in the ear canal, lungs, and liver could alter the host's sensitivity to other stimuli, thereby influencing respiratory system–related studies as well.

The most commonly used methods for detecting Burkholderia glumae in gladiolus include culture and PCR testing of oropharyngeal swabs. If the animal exhibits symptoms such as head tilting, or if it has already died, ear swabs and liver samples can be collected for Burkholderia glumae culture or PCR analysis.

Infected animals can be treated with antibiotics, but this will only alleviate symptoms rather than eliminate the bacteria. Alternatively, high-chlorination or a combination of peracetic acid and hydrogen peroxide (such as Minncare by MinnChill Medical) can be used—specifically, a 2% Minncare solution should be applied twice annually to disinfect the drinking water system. Before implanting tumors, tumor samples must first be tested to confirm the absence of the bacteria; only samples that test negative are suitable for use in PDX model experiments.

When using the PDX tumor model, Burkholderia gladioli poses a significant risk to immunocompromised animals. Therefore, we urge everyone to pay close attention to this bacterium, strengthen monitoring of Burkholderia gladioli in both tumor cells and animal models, improve experimental success rates, and minimize unnecessary losses.

References

1. GB 4789.29-2020 National Food Safety Standard: Microbiological Examination of Food – Testing for Burkholderia gladioli (Pseudomonas cocovenenans subsp. farinofermentans).

2. Foley PL, LiPuma JJ, Feldman SH. 2004. Outbreak of otitis media caused by Burkholderia gladioli infection in immunocompromised mice. Comp Med 54:93–99.

3. Berard M, Medaille C, Simon M, Serre S, Pritchett-Corning K, Dangles-Marie V. 2009. Ralstonia pickettii-induced ataxia in immunodeficient mice. Comp Med 59:187–191.

4. Chereen C, Frank G, Kate B. 2019. Head Tilt in Immunodeficient Mice Due to Contamination of Drinking Water by Burkholderia gladioli. American Association for Laboratory Animal Science, Vol. 58, No. 2, 246–250.