Date of Award

1-1-1985

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Microbiology & Immunology

Abstract

The purpose of this research was twofold. First, determine (1) the existence of multiple antibiotic resistant coliforms (MAR) in the sewage system of Grand Forks, (2) relative numbers of origin, (3) seasonal variation, (4) elimination by the sewage treatment system and, (5) rates of MAR transfer to a receiver organism. The second phase was to determine if MAR could be transferred into a methyl parathion degrading Flavobacterium aquatile (F. aquatile) and test its suitability as a genetic marker, and determine if this organism could survive in primary lagoon sewage (PLS) in competition with indigenous microorganisms.Grab samples of sewage were collected at various lift stations, the composite raw influent and the primary and secondary oxidation lagoons. MAR coliforms were isolated and enumerated by plating on MacConkey ager containing 10 (mu)g/ml of kanamycin, tetracycline, and ampicillin. Rates of plasmid transfer were obtained by incubating MAR coliforms with an Escherichia coli K-12 receiver. A similar method was employed for transferring MAR into F. aquatile. The stability of transconjugant F. aquatiles was ascertained by subculturing transconjugant F. aquatile in the absence of the antibiotics. Survival of F. aquatile in PLS was determined by inoculating F. aquatile into PLS and tracking survival of both total and F. aquatile populations.MAR coliforms were found to be common in the sewage system of Grand Forks. The highest population of MAR coliforms was encountered in sewage from Grand Forks Medical Park. MAR coliforms were reduced from 2-4 logs of magnitude, but were not entirely eliminated prior to discharge of effluent. Seventy five percent of MAR coliforms were capable of transferring MAR at some level. Twenty five percent could transfer at rates greater than 10('-3) transconjugants/donor. MAR and total coliform populations followed the same general trend throughout the year, but MAR coliforms may not be as sensitive to seasonal variations as the total coliform population. A Serratia liquefaciens proved capable of transferring MAR into F. aquatile. MAR transconjugants of F. aquatile were not capable of retaining the MAR phenotype at stable levels within the population. F. aquatile proved unable to compete with autochthonous microorganisms of the PLS.

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