Spratt, Henry G.
Giles, David K.; Levine, David (Veterinary physical therapist)
University of Tennessee at Chattanooga
Place of Publication
Enumeration of bacteria has been the subject of research for over a century. Some of the techniques that have been developed include viable plate counts, the most probable number assessment, and more modern molecular techniques. Many of the newer molecular-based techniques provide little or no information about the viability of the cells being counted, and are generally not quantitative. Having quantitative data for potentially pathogenic bacteria on surfaces can be very useful in many settings, particularly in healthcare facilities. Knowing the numbers of bacterial cells present on surfaces within healthcare facilities may be important to attempt to study the cause of healthcare associated infections (HAIs). This study was envisioned to help develop a rapid technique to quantify viable bacteria utilizing a short (5 cm) line inoculation on agar-based growth media, providing a quick assessment of the density of bacterial cells present. To do this required determination of the relationship between colony counts from line inoculations compared with viable plate counts from the same source of bacterial cells. This study of Escherichia coli and Staphylococcus aureus has produced data that suggests that there is a close relationship between the number of cells placed on a microscope slide and the colony counts obtained from swabs used to remove those cells from the slide, whether counted by a viable plate count or via a short line inoculation on an agar surface. When the number of colony forming units (CFUs) on the microscope slide are < 5000 for E. coli, and < 10,000 for S. aureus there is good correlation between the viable plate count and the line inoculation count. This relationship between the numbers of colonies in the starting material surface and the line inoculation falls off when the numbers of colonies from the source material (the microscope slide) is greater. Factors that may contribute to this loss of correlation when the source material has higher numbers of CFUs may include surface area issues similar to limitations to statistically valid viable plate counts that have been known for a century. The results of this work should lead to additional studies with different species of bacteria, as this study only included one Gram-positive, non-motile coccus (S. aureus) and one Gram-negative, motile rod (E. coli). Other species of bacteria should be studied.
B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.
Bacterial diseases; Bacterial growth
LaRue, Seth, "Calibration study of a bacterial quantification technique using transport swabs and line inoculations on agar growth medium" (2021). Honors Theses.