Rapid Direct Method for Monitoring Antibiotics in a Mouse Model of Bacterial Biofilm Infection

Abstract

We have developed a rapid, continuous method for monitoring the effectiveness of several antibacterial agents in real time, noninvasively, by using a recently described mouse model of chronic biofilm infection (J. L. Kadurugamuwa et al., Infect. Immun. 71:882-890, 2003), which relies on biophotonic imaging of bioluminescent bacteria. To facilitate real-time monitoring of infection, we used a Staphylococcus aureus isolate that was made bioluminescent by inserting a modified lux operon into the bacterial chromosome. This bioluminescent reporter bacterium was used to study the antimicrobial effects of several antibiotics belonging to different molecular families. Treatment with rifampin, tobramycin, and ciprofloxacin was started 7 days after subcutaneous implantation of catheters precolonized with 10 4 CFU of S. aureus. Three different doses of antibiotics were administered twice a day for 4 consecutive days. The number of metabolically active bacteria in untreated mice and the tobramycin-and ciprofloxacin-treated groups remained relatively unchanged over the 4-week observation period, indicating poor efficacies for tobramycin and ciprofloxacin. A rapid dose-dependent decline in metabolic activity in rifampin-treated groups was observed, with almost a 90% reduction after two doses and nearly undetectable levels after three doses. The disappearance of light emission correlated with colony counts. After the final treatment, cell numbers rebounded as a function of concentration in a time-dependent manner. The staphylococci isolated from the catheters of mice treated with rifampin were uniformly resistant to rifampin but retained their in vitro susceptibilities to tobramycin and ciprofloxacin. Since the metabolic activities of viable cells and a postantibiotic effect could be detected directly on the support matrix nondestructively and noninvasively, the methodology is specifically appealing for investigating the effects of antibiotics on biofilms in vivo. Moreover, our study points to the possible use of biophotonic imaging for the detection of the development of resistance to therapeutic agents during treatment of chronic infections in vivo.

A fully functional drug-eluting joint implant

“…While similar survival rate was observed for animals treated with VPE and VTBC, VPE (but not VTBC) completely eradicated all the bacteria in the joint. This may be partly due to Xen29’s higher susceptible to vancomycin [55] than to tobramycin [56]. …”

Investigation of four 99mTc-labeled bacteriophages for infection-specific imaging

“…One approach available to monitor the course of infection is to use bacterial strains that are genetically modified to carry a bioluminescent signal. Contag et al (12), Burns-Guydish et al (13) and Kadurugamuwa et al (15,16) used optical imaging with bioluminescent bacteria in mice as a non invasive means to monitor the progression of GI infections and the implantation of bacterial coated catheters with antibiotic treatment. Studies are under way in this laboratory to combine fluorescent tagged phage with bioluminescent bacteria to provide information on the spread, location and intensity of the infection.…”

Expression of flagella is coincident with uropathogenic Escherichia coli ascension to the upper urinary tract

“…For in vivo imaging of experimentally infected mice, hair was completely removed from both ventral and dorsal sides of the animals below the scapula including the abdominal and pelvic areas using a razor and cosmetic hair removal treatment (Veet, Reckitt Benckiser, Parsippany, NJ). Infected mice were imaged at various times after infection by using an IVIS 200 imaging system (Xenogen), as described (29). Mice were anesthetized in chambers containing 2.0% isofluorane inhalant (Baxter, Deerfield, IL).…”