Honors Theses
Date of Award
2004
Document Type
Undergraduate Thesis
Department
Biology
First Advisor
Lydia Halda-Alija
Relational Format
Dissertation/Thesis
Abstract
Bacterial resistance to antibacterial agents is a condition in which there is no susceptibility or decreased susceptibility to antibacterial agents that ordinarily cause cell death or inhibition of bacteria. Bacterial resistance to antibacterial agents is a quantitative measurement of the efficiency or concentration expressed in micrograms per milliliter or as inhibition zones in millimeters for the diffusion technique of an antibacterial agent against a specific bacterium. In vitro methods for measurement of antibacterial activity are available that are based on testing increased concentrationsof antibacterial agent against a bacterial isolate to identify at which concentration the growth of the bacterium is inhibited. The lowest concentration at which detectable growth is inhibited is known as the minimum inhibitory concentration (MIC) of the antibacterial agent. Indeed the MIC indicates the relative measurement of the smallest concentration of antibacterial agent required to inhibit the growth (cell division) of a bacterium. Bacterial isolates from clinical environment are regularly tested for antibiotics susceptibility. Clinical isolates are selected for antibiotic susceptibility testing to monitor antibiotic resistance and multidrug-resistance so as to enhance medical therapy. However, with the increasing use of antibiotics outside the clinical area, it has become necessary to determine the antibiotics susceptibility of environmental bacterial isolates. It has become important to determine the spread of resistant organisms throughout the environment. Environmental isolates obtained from northern Mississippi wetlands were tested for antibiotic susceptibility to different class of antibiotics including novel antibiotics. Antibiotics susceptibility testing of the environmental isolates classified as being pathogenic were done using microdilution protocol specified by the National Committee on Clinical Laboratory Standards (NCCLS). The degree of growth response of each isolate in response to a particular antibiotic was recorded. Antibiotic potency for a particular isolate was determined in terms of the IC50 concentration (antibiotic concentration that affords only 50% growth of the bacteria), the minimum inhibitory concentration (lowest concentration of the antibiotic at which growth of bacteria is limited) and the minimum bactericidal concentration (the minimum concentration of the antibiotic at which growth of the organism is completely inhibited). MIC values of the antibiotics in the presence of each environmental isolate were compared to the MIC interpretative standards ((/xg/ml) for Enterobacteriacae according to NCCLS. Data from different antibiotics susceptibility testing suggested that the environmental isolates were resistant to the earlier generation of p-lactam class of antibiotics. On the contrary. resistance to tetracycline, a commonly used antibiotic in agriculture, was found to be intermediate. The environmental isolates were generally susceptible to newer generation of P-lactams, such as cefoxitin and ceftazidime. Antibiotic resistance to p-lactams is mainly attributed to the production of p-lactamase enzyme by bacteria that hydrolyzes the p-lactam ring of the P-lactams and reduces the effect of p-lactams. The newer generations of p-lactams possess a bulkier structure around the p-lactam ring to resist the action of p-lactamase enzyme. The results of this study suggest that environmental Plactamase enzyme did not evolve to recognize a bulkier structure of the new generations of P-lactams antibiotics.
Recommended Citation
Moktan, Shama, "Antibiotic Resistance in Northern Mississippi Wetlands" (2004). Honors Theses. 2238.
https://egrove.olemiss.edu/hon_thesis/2238
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