In vivo bioluminescence imaging of Burkholderia mallei respiratory infection and treatment in the mouse model

Abstract

Bioluminescent imaging (BLI) technology is a powerful tool for monitoring infectious disease progression and treatment approaches. BLI is particularly useful for tracking fastidious intracellular pathogens that might be difficult to recover from certain organs. Burkholderia mallei, the causative agent of glanders, is a facultative intracellular pathogen and has been classified by the CDC as a Category B select agent due to its highly infectious nature and potential use as a biological weapon. Very little is known regarding pathogenesis or treatment of glanders. We investigated the use of bioluminescent reporter constructs to monitor the dynamics of infection as well as the efficacy of therapeutics for B. mallei in real-time. A stable luminescent reporter B. mallei strain was created using the pUTmini-Tn5::luxKm2 plasmid and used to monitor glanders in the BALB/c murine model. Mice were infected via the intranasal route with 5 × 103 bacteria and monitored by BLI at 24, 48, and 72 h. We verified that our reporter construct maintained similar virulence and growth kinetics compared to wild-type B. mallei and confirmed that it maintains luminescent stability in the presence or absence of antibiotic selection. The luminescent signal was initially seen in the lungs, and progressed to the liver and spleen over the course of infection. We demonstrated that antibiotic treatment 24 h post-infection resulted in reduction of bioluminescence that can be attributed to decreased bacterial burden in target organs. These findings suggest that BLI can be used to monitor disease progression and efficacy of therapeutics during glanders infections. Finally, we report an alternative method to mini-Tn5::luxKm2 transposon using mini-Tn7-lux elements that insert site-specifically at known genomic attachment sites and that can also be used to tag bacteria.

In vivo bioluminescence imaging of Escherichia coli O104:H4 and role of aerobactin during colonization of a mouse model of infection

“…We recovered 4.8 x 10 6  ± 1.3 x 10 6 (at 24 h), 1.6 x 10 7  ± 4.7 x 10 6 (at 48 h), 3.2 x 10 7  ± 9.5 x 10 6 (at 72 h), and 2.3 x 10 3  ± 9.7 x 10 2 (at 168 h) CFUs of strain RJC001, confirming that colonization of the intestinal cecum occurred within 3 days of infection, and lower numbers of bacteria were recovered after 7 days. In our previous work, we reported that the threshold of bioluminescent detection is likely in the range of 1 x 10 3 - 1 x 10 4 bacteria [18]; therefore, the low numbers of the reporter strain recovered at 7 days explained the absence of the signal.…”

“…Bioluminescent images were acquired by using an IVIS Spectrum (Caliper Corp., Alameda, CA) as we previously described [18]. The ex vivo images of the intestine were acquired at each time point immediately after euthanasia.…”

Development of Bioluminescent Bioreporters for In Vitro and In Vivo Tracking of Yersinia pestis

“…Independently, two groups demonstrated that experimental melioidosis could be visualized in the mouse model [14], [15]. Furthermore, Warawa et al were able to visualize both upper and lower respiratory tract colonization, differentiate between colonization patterns of mutant bacteria, and show that luminescence detection from the thoracic cavity strongly correlated to bacterial numbers in the lung.…”

A Bioluminescent Francisella tularensis SCHU S4 Strain Enables Noninvasive Tracking of Bacterial Dissemination and the Evaluation of Antibiotics in an Inhalational Mouse Model of Tularemia

“…Pivotal experiments by Contag et al have demonstrated the usefulness of BLI in the noninvasive study of bacterial pathogenesis and the evaluation of antibiotic treatments for Salmonella enterica serovar Typhimurium (11). Subsequently, bioluminescent reporters have been introduced into other bacteria, including Mycobacterium tuberculosis (10,12), Staphylococcus aureus (13,14), Burkholderia mallei (15), and Yersinia pestis (16,17). Further, BLI has been used to evaluate vaccines (18), antibiotics (19)(20)(21), and supportive therapies (22) for a range of pathogens.…”