Revised; Original Published: 2002 / 4 pp.

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Staphylococci are opportunistic pathogens responsible for a range of infections. Many staphylococcal species are frequently found to be resistant to antibiotics. The environment is considered a potential reservoir of genes conferring antibiotic resistance, which known as the 'resistomes'. Monitoring the dissemination of antibiotic resistant staphylococci is instrumental to mitigating this global health risk. The overall aim of this study was to generate informative data regarding dissemination of antibiotic resistance in environmental and public settings. This included looking into the distribution, epidemiology characteristic and transfer of oxacillin resistant determinant mecA; gaining an insight into genomic features that contribute to multiple antibiotic resistance and pathogenicity of one S. epidermidis isolate; and understanding the stress responses in mediating oxacillin resistance in S. aureus. The use of MALDI-TOF MS allowed identification of staphylococci to species level. MALDI-TOF MS data were used for taxonomic analysis of staphylococci, and taxonomic data were then combined with isolation sites and antimicrobial susceptibility profiles to aid the understanding of dissemination of environmental resistant staphylococci. The widespread dissemination of antibiotic resistant staphylococci in the environment was demonstrated. 12% of staphylococci harboured mecA gene. Community associated SCCmec types IV and V were more prevalent than nosocomial associated SCCmec types I, II, and III in the environment. 52% of SCCmec were non-typable. In addition, 14 new environmental S. epidermidis MLST types were reported. 9 antibiotic resistant determinants that were responsible for the resistant to 7 antimicrobial classes have been identified in environmental S. epidermidis 118 (G6_2). Proteomic analysis revealed that stress responses, including SOS response, stringent response and heat shock response, mediate oxacillin resistance in S. aureus. These results demonstrate widespread multiple drug resistance in different staphylococcal species isolated from non-healthcare environments. This uncontrolled dissemination of multidrug resistant bacteria poses a potential public health threats.

Two tannin sorghums, (high-tannin, black with tannin), high anthocyanin sorghum (black), and non-tannin sorghum (white) were used to investigate the effects of sorghum phenolic compounds on in vitro starch digestibility, estimated glycemic indices (EGI) and resistant starch contents (RS) of porridges. Sorghum varieties were chosen to have a wide range of total phenols (3-23 mg/g gallic acid) and tannin contents (0-34 mg catechin eq./g). Normal corn starch, enzyme resistant high amylose corn starch, and whole sorghum grains were cooked with the aqueous fraction of sorghum bran extracts obtained with 70% aqueous acetone. Endosperms of soft and hard sorghum varieties were mixed with sorghum brans and cooked into porridges with distilled water. Hi-tannin, black and black with tannin sorghum bran extracts significantly (p<0.05) decreased starch digestibility and estimated glycemic index (EGI) while they increased resistant starch (RS) contents of normal corn starch, enzyme resistant high amylose corn starch, and whole sorghum grain porridges. The highest reduction in starch digestibility of the porridges occurred with hi-tannin sorghum bran extracts, followed by black with tannin and black sorghum bran extracts. Double cooked corn starch porridges, which were cooked with these bran extracts had EGI values of 49-67 and RS contents of 9.1-57.7%. These RS values are higher than foods such as legumes, whole pasta and whole grain cereals which are considered health foods with low EGI (36-71) and high RS contents (2.9-6.8). Only brans of condensed tannin-containing sorghum varieties (tannin, black with tannin sorghums) significantly (p<0.05) decreased starch digestibility, and EGI, and increased RS contents of the endosperm porridges. When tannin sorghum bran extracts were cooked with zein added to corn starch porridges, starch digestibility of the porridges significantly (p<0.05) increased, while RS significantly (p<0.05) decreased because the zein reacted preferentially with the tannins. The cooking trials indicated that sorghums with tannins significantly reduced the activity of digestive enzymes, reduced EGI, and increased RS contents of porridges. Thus, specialty sorghum varieties have a potential to lower EGI and increase RS contents of starchy foods. Their aqueous bran extracts have potential use to reduce risk factors for type II diabetes and obesity.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.S. in M.S.E.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2004. Directed by W. Steven Johnson. / Includes bibliographical references (leaves 141-148).