In 1990-1991, in a national surveillance study, and in 1991-1992, in a followup study, both by Thornsberry et al. (1993), ciprofloxacin data from various geographical and demographical institutions were collected. Several species of bacteria have shown resistance to ciprofloxacin and norfloxacin, but the degree of resistance to these drugs has not been reported for the Stockton area. To determine the extent of this resistance, Dameron Hospital antibiograms generated from 1990 to 1994 were reviewed and compared. Results of the comparison show that susceptibility among the Gram-negative isolates, with the exception of Providencia stuartii, Acinetobacter lwoffi, and to a lesser extent Aeromonas hydrophila, has changed very little. Consistent with the national surveys, resistance of Pseudomonas aemginosa has not changed appreciably during the five-year period. Among the Gram-positive isolates that were tested against both ciprofloxacin for a five-year period (1990-1994) and norfloxacin for a three-year period (1992"' 1994), increased resistance was seen among strains of Staphylococcus aureus, S. epidermidis, S. haemolyticus, and Enterococcus jaecalis, but not among strains of Staphylococcus saprophyticus, Streptococcus pyogenes, and S. agalactiae. To determine whether resistance to one fluoroquinolone occurs also to other fluoroquinolones, several isolates of Gram-positive cocci and P. aeruginosa from the Gram-negative bacilli that showed resistance to either ciprofloxacin, norfloxacin, or both were selected from Dameron Hospital isolates and tested by the disk diffusion technique against ciprofloxacin, norfloxacin, ofloxacin, and lomefloxacin. The results indicate that differences do exist among these selected strains. Comparison of the invitro effectiveness of the various quinolones confirms that methicillin-resistant staphylococci (S. aureus, S. epidermidis, and S. haemolyticus) exhibit a higher degree of resistance to the four fluoroquinolones compared with the methicillin-susceptible strains of the same species. Resistance of the enterococci (Enterococcus jaecalis and E. jaecium) is also high. Generally, when the four fluoroquinolones were compared with each other, ofloxacin seemed to have better in vitro activity. Resistance to the quinolones consists of two proposed mechanisms: ( 1) mutation of one or both of the structural genes of the A and B subunits of DNA gyrase and (2) decreased drug accumulation due either to lower uptake by the cell or enhanced effiux out of the cell. These mechanisms of resistance are reviewed.

No description available.

No description available.

Present methods of counting and sizing of bacteria arc usually tedious and often have low statistical validity. The objective of this thesis was to investigate the feasibility of counting and sizing of bacteria with the Coulter Counter and to evaluate orifices which were prepared in this laboratory. Size distributions of Pasteurella multocida and Proteus vulgaris were obtained with the electronic particle counter. These distributions appeared to follow the normal distribution when relative per cent was plotted against diameter, The two modes of the distributions appeared far enough apart to warrant future attempts to separate quantitatively <i>P. vulgaris and P. multocida </i>in mixed suspensions. Size distributions also were obtained for <i>Staphylococcus epidermidis, Sarcina lutea,</i> and <i>Azotobacter</i>. Many variables appeared to be inherent in the electronic particle method of counting biological cells; among these are the biological cells, diluent, and electronic circuitry. Apparently the variability in the electronic circuitry caused the calibration of laboratory orifices to be impossible according to conventional methods. / Master of Science

"In order to gain an adequate idea of the sanitary condition of the drinking fountains on the North Texas State Teachers College campus, it was found necessary to approach these bacteriological studies from a seasonal point of view."--1.

Azotobacter and various fungi were grown together in nitrogen-free media. Maximal fungal growth in the medium used was possible only at the expense of Azotobacter cells and growth was always accompanied by acid production. When the medium reached a pH of 2, the bacterial cells were aggregated on fungal hyphae and the culture fluid appeared to be free of Azotobacter. Aspergillus niger grew well at the expense of viable bacteria and other fungi grew well on heat-killed cells of A. vinelandii. Members of the genus Hormodendrum, although not causing significant decrease in pH, were also able to clear turbid cultures of Azotobacter. However, clearing, which involved the attachment of bacteria to fungal hyphae, was dependent on acid production by the fungi. Bacterial aggregation was followed by hyphal attachment, bacterial inactivation, and finally, bacterial cell lysis.

<p> </p> <p>Disinfectant application on environmental surfaces is generally accepted to be effective</p> <p>against vegetative pathogens. However, several important application considerations are not being evaluated</p> <p>in the registration of these disinfectant solutions. This thesis looks into factors impacting the disinfectant wipes' bactericidal and fungicidal efficacy on hard, non-porous surfaces and how the interaction between the disinfectant solution and wipe substrate lead to changes in the efficacy of disinfection.</p>

<p>The sigma S subunit (RpoS) of RNA polymerase acts as the master regulator of stress in <em>Escherichia coli</em>, allowing adaptation and survival under unfavourable conditions such as nutrient deprivation. RpoS regulates and integrates the signals of hundreds of genes (about 10% of the genome) organized into complex networks and modules that govern the response to stress and entry of the cell into stationary phase. Although microarray studies have been performed on starvation models in <em>E. coli</em>, the expression of the RpoS regulon has not been studied in long-term cultures due to the difficulty of isolating RNA from starving cells. In this study, the development of a protocol for isolating RNA from stationary phase cells, employing hot acid phenol without the use of DNase, is described. In addition, the expression of several genes during different phases of growth is analyzed by RT-qPCR in order to validate preliminary microarray data obtained from 24 and 48 hour-old cultures. Although the results obtained by RT-qPCR agree well with the literature, they do not corroborate preliminary microarray data at the 24 and 48 hour timepoint.</p> / Master of Science (MSc)

<p>Bacteria adapt to changes in their environment by regulating gene transcription. TetR family transcriptional regulators (TFRs) constitute one of the largest groups of bacterial transcription factors and thus, characterization of TFRs is anticipated to be crucial for a better understanding of prokaryotic physiology. Of significant importance, the majority of TFRs are predicted to respond to small-molecule signals and an emerging paradigm suggests that identifying ligands of TFRs can provide direct insight into the biochemical functions of the genes they regulate. Regulatory target genes and small-molecule ligands are unknown for all but a few TFRs and therefore, generally applicable tools for identifying these basic elements of TFRs are highly desirable. We first investigated the use of genome context as a predictive tool for identifying regulatory targets of TFRs. We find that the majority of TFRs are divergently oriented from a neighboring gene, and those with a“200 bp rule” should allow us to predict at least one regulatory target for more than half of all TFRs in the public databases. Second, we developed a biosensor mechanism amenable to high-throughput screening for identifying ligands of TFRs of unknown function. Significantly, one of our biosensors has played an integral role in characterizing the ligands of a previously uncharacterized TFR. Thus, the combined use of the tools we have developed will provide considerable benefit in understanding bacterial small-molecules responses mediated by TFRs.</p> / Doctor of Philosophy (PhD)

Typescript (photocopy). / Digitized by Kansas Correctional Industries