Susceptibility of Antibacterial Chemicals on
Pseudomonas aeruginosa

Research performed by:

Clayton Brady

Health Science Biology Major

Tennessee Technological University

Susceptibility of Antibacterial Chemicals on
Pseudomonas aeruginosa

Abstract

The objective this research is to determine if chemicals commonly found in the antibacterial sprays we use so abundantly today can in fact render potentially hazardous bacteria, such as Pseudomonas aeruginosa, non-viable. Bacteria can be resistant to many types of these agents. Pseudomonas aeruginosa will be used as a test subject for this experiment because of its resistance to many different agents. It is believed that the chemicals will have no effect on Pseudomonas aeruginosa. Although Isopropyl alcohol, Vesphene, and 1M Hydrochloric acid may disinfect some bacteria it is not effective as an antibacterial agent against Pseudomonas aeruginosa. Bleach however, was very effective against the bacteria.

Key Words

Pseudomonas aeruginosa

Biofilm

Antimicrobial

Antibacterial

Introduction

The distribution of pathogens causing nosocomial infections, especially antimicrobial-resistant pathogens, changes with time and varies among hospitals and among different locations in the same hospital. The increasing number of immunocompromised patients and increased use of indwelling devices, as well as widespread use of antimicrobial agents in hospital settings, particularly in intensive care units, contributes to antimicrobial resistance among pathogens causing nosocomial infections. (Hseuh, 2002) Many diseases arise from bacteria that grow resistant to the agents that are made to combat them.  One of these bacteria is Pseudomonas.

A Pseudomonas infection is caused by a bacterium, Pseudomonas aeruginosa and may affect any part of the body. In most cases, however, Pseudomonas infections strike only persons who are very ill, usually hospitalized. (Rowland, 2001) Pseudomonas aeruginosa is an opportunistic pathogen that engages in a plasmid exchange with other bacteria making it very hard to kill because of its ability to build resistance to many cleaners and medicines. Pseudomonas aeruginosa is responsible for 16% of nosocomial pneumonia cases, 12% of hospital-acquired urinary tract infections, 8% of surgical wound infections, and 10% of bloodstream infections. (Rowland, 2001) Patients can contract infections such as Pseudomonas aeruginosa after endoscopic retrograde cholagiopancreatography (ERCP) through contamination of instruments. Decontamination of the instrument and surroundings should be carried out after use, followed by disinfection. (Smith, 1994)

Through new research, scientists can develop new antimicrobial agents and antibiotics to ensure the elimination of a bacterium for a limited period of time.  It is difficult to treat a Pseudomonas infection because the bacterium becomes resistant to so many antibiotics. After a number of years, the bacteria that persist become resistant to all antibacterial treatment. (Anonymous, 2001) Individually, Pseudomonas aeruginosa cells can be controlled by antibiotics but when the bacteria form biofilms they are much harder to fight and can cause untreatable lethal infections. (Greenberg, 1998)

The objective this research is to determine if chemicals commonly found in the antibacterial sprays we use so abundantly today can in fact render potentially hazardous bacteria, such as Pseudomonas aeruginosa, non-viable. 

It is believed that the chemicals will have no effect on Pseudomonas aeruginosa.

Materials and Methods

This experiment required Petri dishes, a synthetic stock of Pseudomonas aeruginosa, an inoculation loop, and a sterilizer (incinerator) for streaking the plates. The chemicals used were Isopropyl Alcohol, 1 M Hydrochloric Acid, 5 % Hypochlorite Bleach, and Vesphene. All of these chemicals are commonly used to disinfect areas contaminated with bacteria. In order to have the bacteria to grow, an incubation device was needed. A ruler was needed to measure the zone of inhibition around the discs. Finally, an autoclave was required to sterilize the tools after use.

The method used in my experiment was the Mueller Hinton / Pseudomonas Agar Disc Diffusion Assay Tests. (Goss, 2001) Using aseptic techniques, the experiment began with taking an inoculating loop, sterilizing it by way of heating it, and obtaining a sample of the bacteria being used. The bacteria were then exposed to discs dipped in each of the four chemicals.  The dishes were separated into quadrants for each of the four chemicals tested. The bacteria were given a full day to grow and on the third day the zone of inhibition was observed and measured for results.

Results

After careful aseptic experimentation, Pseudomonas aeruginosa was rendered non-viable by one of the chemicals used in the experimental process. There was not a zone of inhibition observed for the Vesphene, Isopropyl Alcohol and the 1 M Hydrochloric Acid. The bleach had a zone of inhibition that measured 21 millimeters. Please refer to the table in appendix A.

Discussion

Pseudomonas infections can be spread within hospitals by health care workers, medical equipment, sinks, disinfectant solutions and food. (Rowland, 2001) Decontamination of the instruments as well as the hospital itself should be carried out after each use. (Smith, 1994) Hospitals worldwide are continuing to face the crisis of the upsurge and dissemination of antimicrobial-resistant bacteria, particularly those causing nosocomial infections n ICU patients. (Hsueh, 2002)

This experiment was performed to find a solution to the growing problem previously mentioned. The other chemicals, perhaps effective on other types of bacteria, were ineffective against Pseudomonas aeruginosa. In fact three of the chemicals had no zone of inhibition; proving that Isopropyl alcohol, Vesphene, and HCL (1M) are not effective antimicrobial chemicals. Bleach, however was very effective in rendering the bacteria non-viable, proving my hypothesis incorrect.

After a number of years, bacteria become resistant to all antibacterial treatment. (Anonymous, 2001) An experiment in Pseudomonas aeruginosa showed that the bacteria can strengthen their links by communication with one another using a certain chemical, through the process of biofilm forming. Although bacteria can be eliminated by antibacterial sprays, they exhibit stronger resistance when biofilms are already formed. (Greenberg, 1998) It would be very interesting to conduct this same study on biofilmed stock to determine the effectiveness of bleach on the bacteria.

Conclusions

• Bacteria forming biofilms is extremely hard to kill and prevent.

• Bleach (5% hypochlorite solution) was found to be an effective antibacterial agent proving my hypothesis wrong.

• Although Isopropyl alcohol, Vesphene, and HCL (1M) may disinfect some bacteria it is not effective as an antibacterial agent against Pseudomonas aeruginosa.

• Hospitals relying on the above mentioned chemicals to disinfect their operating rooms may not be as safe as previously thought.

Acknowledgements

Dr. Karen Kendell-Fite at Columbia State Community College.

Appendix A.

Pseudomonas aeruginosa Disk Diffusion Chart
Disc Diffusion Assays
	Susceptible	Resistant	Zone of Inhibition
Isopropyl Alcohol		+
1 M HCl		+
5 % hypochlorite bleach	+		21 centimeters
Vesphene		+

Literature Cited

Anonymous. 2001. Bacterium may teach scientists how to kill cancer cells. (Pseudomonas aeruginosa). Cancer Weekly.

Greenberg, Peter. 1998. Best way to kill bacteria? Stop them talking. World Disease Weekly Plus. 17

Goss, S. 2001-2002. Control of Microbial Growth. Health Science Microbiology Laboratory Manual. 62-66

Hsueh, Po-Ren et al. 2002. Antimicrobial drug resistance in pathogens causing nosocomial infections at a University Hospital in Taiwan. Emerging Infectious Diseases. 63

Rowland, Belinda. 2001. Pseudomonas infections. The Gale Encyclopedia of Medicine. Second Edition.

Smith, Frances. 1994. Pseudomonas infection. Nursing Times. v90. n46. 55

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