Michael Le Bras and Dr. William G. Pitt, Department of Chemical Engineering
Previous studies show that using antibiotic treatment together with ultrasound enhances the bactericidal effect of antibiotics on many bacterial species (6). The purpose of this research project is to apply these techniques to Streptococcus pneumoniae and the antibiotics ampicillin and gentamicin sulfate. The effectiveness of ampicillin and gentamicin sulfate coupled with the application of ultrasound on S. pneumoniae is the focus of this study.
Ampicillin is a drug of choice in combating S. pneumoniae (7). This study intents to prove that the antimicrobial activity of ampicillin is more effective when associated with ultrasound. Gentamicin sulfate is not considered a drug of choice against this bacteria (7). This study seeks to prove that ultrasound can positively enhance the effect of gentamicin sulfate against S. pneumoniae.
S. pneumoniae was chosen for this study because it is one of the most common causes of bacterial pneumonia (2,3,4). It causes pneumonia in individuals with weak immune systems such as infants, children, senior citizens, and intensive care hospital patients (2,3,4). Treatment of S. pneumoniae is becoming more difficult because many strains of this bacteria are now resistant to the commonly prescribed antibiotic penicillin (1).
Some important changes were made to the original research proposal (5). The most noteworthy change is the nutrient requirements for S. pneumoniae and the length of time necessary to incubate it prior to experiments (5,.). S. pneumoniae is very sensitive to environmental changes such as temperature, high levels of oxygen, lack of nutrients, and pH changes (ref).
S. pneumoniae ATCC 6303 was obtained from the microbiology stockroom at Brigham Young University. S. pneumoniae is grown and maintained on a sheep blood agar plate. Fourteen hours before an experiment, 10 ml of Todd- Hewitt Broth (THB) supplemented by 3 ml of calf serum is inoculated with a bacterial colony from the sheep blood agar plate and grown overnight at 37 C. Sheep blood agar, THB, and calf serum provide more nutrients than nutrient agar and tryptic soy broth (TSB) provided for this bacteria (5).
After 14 hours, the culture is diluted 1:1000 into sterile THB and calf serum and grown in a 50-ml Erlenmeyer flask on a rotary shaker at 80 RPM. The second culture is grown until it reaches its exponential growth phase. The number of bacteria in this culture is determined by serial dilutions in Physiological Saline Solution (PSS) and plating on sheep blood agar. The colonies are counted after agar is incubated for 24 hours at 37 C.
The exponential growth phase and minimum inhibitory concentration (MIC) were determined following the procedure outlined in the original proposal (5). The exponential growth phase begins five hours after the second culture (described above) is started. The MIC for ampicillin on S. pneumoniae is 0.08)g/ml and the MIC for gentamicin sulfate on S. pneumoniae is 7)g/ml. The ultrasound experiments were modified to include the special nutrient requirements of S. pneumoniae (5). They are being conducted according to the procedures described in the original proposal (5). At this time the ultrasound experiments are producing inconclusive data. Gentamicin sulfate experiments are showing signs that the ultrasound is enhancing its effect on S. pneumoniae. However, the researcher is not confident that the data is inconclusive enough for publication at this time. More experiments must be conducted to finalize these results. It is projected that the researcher will need four to six more weeks to finish the research necessary to provide conclusive information.
Despite many set backs the researcher is optimistic that the completion of this research project will yield positive results. It is still expected that ultrasound will enhance the effect of both ampicillin and gentamicin sulfate on S. pneumoniae (5). Following the completion of this project the researcher will continue to apply these techniques to other organisms known to cause respiratory diseases such as tuberculosis and fungal infections of the lungs.
The author would like to thank Dr. William Pitt for advising and providing extra funding for this project. Also the author would like to thank Dr. Richard Robison, Glen Allman, John Lee, Weston Hymas, and Andrea Reidske for answering questions and providing suggestions for completing this project.
References
- Baquero, F. 1997. Challenge for the development of new antibiotics. Journal of Antimicrobial Chemotherapy. 39, Supple. A: 1-6.
- Cargo, C. 1996. The diagnosis and management of bacterial pneumonias in infants and children. Primary Care. Clinics in Office Practice. 23:821-835.
- Crowe, H. 1996. Nosocomial pneumonia: problems and progress. Heart and Lung. 25:18-21.
- Jiménez, C., J. Caravalho, and I. Hwang. 1997. Insidious illness in active seniors, decoding atypical presentations. The Physician and Sports medicine.24: 112-116.
- Le Bras, M. 1997. ORCA Scholarship Proposal.
- Pratt, A., W. Hymas, and W.G. Pitt. 1997. Ultrasonic enhancement of antibiotic action on several species of bacteria. Submitted for publication.
- Prescott, L., J. Harley, and D. Klein. 1993. Antimicrobial Chemotherapy. Microbiology Second Edition. 325-343. Wm. C. Brown Publishers. Dubuque, Iowa.
- Ryan, J.K., Editor. J.J. Champoux, W.L. Drew, S. Falkow, F.C. Neidhardt, J.J. Plorde, and C.G. Ray.1990. Streptococci and Enterococci. Sherris Medical Microbiology, An Introduction to Infectious Diseases Third Edition. Appleton and Lange. Norwalk, Conn.