Starzyk, Marvin J.
M.S. (Master of Science)
Department of Biological Sciences
Staphylococcus aureus; Staphylococcus
Within our natural water reserves there exist staphylococci, and more importantly the Staphylococcus aureus species, a known contact pathogen. Staphylococcus aureus, can be found on the surface o f human skin and mucus membranes and is a member o f the normal flora o f these areas. While S. aureus can exist in harmony on or in our bodies as part o f the normal flora, this bacterium is like a double edged sword, always having the potential to become a serious pathogen. Because o f their potential pathogenic nature and ability to use water as a vehicle, it has been suggested that the staphylococci and more specifically, S. aureus, could serve as a better bacteriological indicator o f human contamination and disease potential o f contact water than the currently used fecal and total coliforms. S. aureus is also resistant to chlorine at the concentrations at which the average swimming pool is maintained and humans can tolerate. . The difficulty in implementing this suggestion lies in the development o f a medium that can successfully selectively recover the staphylococci. Much work has been done to develop a membrane filter medium that can accurately select for and enumerate these bacteria. Over the years, there have been various selective/differential media utilized for the isolation o f Staphylococcus including Lipovitellanin Salt Mannitol Agar (LSM). However, such media have been reported to exhibit a lower recovery rate and selectivity for staphylococci than non-selective media such as Tryptic Soy Agar (TSA). In this study, pyruvate was added to less selective media such as Vogel-Johnson and resulted in an increased recovery o f staphylococci, but the recovery rate was still low. Pyruvate was also tested as an additive to the selective medium LSM45. While the optimal colony morphology o f staphylococci occurred on LSM45 medium when 1% pyruvate was added, the recovery rate was statistically the same on TSA. With the TSA recovery set at 100%, LSM45 without pyruvate recovered 85%, and Mannitol Salt Agar (MSA) recovered 60% o f staphylococcal species. Nutritional studies showed that Staphylococcus aureus will utilize pyruvate as a sole carbon source with growth essentially equivalent to that produced with mannitol. However, the presence o f both pyruvate and mannitol together increased the staphylococcal growth on a level equivalent to the combination o f mannitol and pyruvate individual growth rates. The addition o f pyruvate to LSM45, as applied in the membrane filter technique, resulted in enhanced staphylococcal colony morphology and pigmentation for both clinical and laboratory strains exposed to environmental river water. Staphylococcus aureus on LSM45P were differentiated by color as golden colonies and the coagulase negative staphylococci as white colonies. The addition o f pyruvate was shown to lengthen the "shelf life" o f the LSM45 from less than one week to five weeks. Incorporation o f pyruvate into LSM45 medium resulted in an increase in the overall recovery rate o f environmentally stressed S. aureus and improved characteristics o f the medium for staphylococcal differentiation and enumeration.
Malekpour, Susan, "Improvement in visualization and isolation of staphylococci from environmental and clinical samples" (1997). Graduate Research Theses & Dissertations. 3515.
xi, 94 pages
Northern Illinois University
Rights Statement 2
NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.