Sortase A is a housekeeping enzyme of Gram-positive bacteria that catalyses the anchoring of surface proteins to the bacterial peptidoglycan. The enzyme works to establish an interaction between bacteria and host cells and is essential for pathogenesis. This makes Sortase A a potential suitable target for inhibition, in order to treat bacterial infections. In this degree project Sortase A from Staphylococcus aureus was explored and potential inhibitors were investigated by performing enzyme activity and bacterial binding assays. A robust FRET assay was developed and optimized for a recombinant version of the enzyme and serves as a good starting point for studying inhibition.

A genetic algorithm was employed to select the optimal combination of preprocessing variables, including data pretreatment, data manipulation and feature extraction procedures, for eventual clustering of a data set consisting of hyperspectral images acquired by a focal plane array Fourier transform infrared (FPA-FTIR) spectrometer. The data set consisted of infrared images of bacterial films, and the classification task investigated was the discrimination between Gram-positive and Gram-negative bacteria. The genetic algorithm evaluated combinations of variables pertaining to bacterial film thickness tolerances, baseline correction, pixel co-addition, outlier removal, smoothing, mean centering, normalization, derivatization, integration and principal component selection. Following numerous iterations of unsupervised processing, the genetic algorithm arrived at a sub-optimal solution yielding a clustering accuracy of 97.8% and a data utilization of 28.6%. The results provided insight into the co-dependencies of the pre-processing variables and their consequential effect on the selected data. The robustness of the classification model was evaluated and reinforced by the successful classification of two distinct validation sets. The overall success of the genetic algorithm suggests that it is an effective time saving resource for the optimization of pre-processing variables that does not require operator intervention.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Title from first page of PDF file (viewed Feb. 19, 2009). Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xv, 139 p.; also includes graphics (some col.) Includes bibliographical references (p. 123-139).

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Timothy M. Logan, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Sept. 14, 2005). Document formatted into pages; contains xix, 166 pages. Includes bibliographical references.

Made available in DSpace on 2014-06-11T19:24:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-15Bitstream added on 2014-06-13T19:10:40Z : No. of bitstreams: 1 witzel_cl_me_botfm_parcial.pdf: 120396 bytes, checksum: ec18337e12bca612c7c9844103a8160d (MD5) Bitstreams deleted on 2014-06-27T19:00:45Z: witzel_cl_me_botfm_parcial.pdf,Bitstream added on 2014-06-27T19:02:01Z : No. of bitstreams: 1 witzel_cl_me_botfm.pdf: 1277080 bytes, checksum: c6e53fb083813be017b346181b7be466 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / As Infecções estafilocócicas são grande causa de mortalidade e morbidade. A emergência de isolados de Staphylococcus aureus resistente à meticilina (MRSA) originários da comunidade na década de 1990 trouxe desafios para sua prevenção e abordagem terapêutica. A identificação da prevalência e características de MRSA adquirido em comunidade (CA-MRSA) em populações de alto risco pode fornecer valiosas informações para compreensão de sua epidemiologia. O objetivo deste estudo foi identificar a prevalência, os fatores de risco e as características moleculares de CA-MRSA isolado em nasofaringe de uma população carcerária em Avaré, Brasil. Foram coletados swabs nasais de 302 homens encarcerados no Centro de Ressocialização de Avaré. A caracterização da resistência à meticilina foi feita através de difusão em disco (Oxacilina e Cefoxitina) e identificação do gene mecA (por Reação em Cadeia de Polimerase (PCR). Utilizou-se também PCR para identificação dos genes lukF-PVe lukS-PV que codificam a leucocidina de Panton-Valentine. Fatores de risco para colonização nasal por S. aureus e por MRSA foram avaliados em modelos univariados e multivariados (regressão logística). A prevalência de colonização nasal por S. aureus como um todo foi de 16,5%, e a MRSA (definida como positividade para o gene mecA), de (02) 4,0%. Os testes de difusão com disco de Oxacilina e Cefoxitina identificaram 2 (4%) resistentes simultaneamente a Oxacilina e Cefoxitina. Nenhum dos isolados de S. aureus apresentou genes codificadores da PVL. As amostras positivas para gene mecA apresentaram SCCmec tipo IV, confirmando esta tipagem presente em amostras comunitárias.Uma das amostras positivas para gene mecA apresentou SCCmec IV-d, que pelo método PFGE agrupou em 85,7% com o clone JCSC 4469 de origem japonesa. Os fatores de risco para... / Staphylococci infections are a major cause of morbidity and mortality. The emergence of methicillin-resistant Staphylococcus aureus (MRSA) isolates original from the community in the 1990s brought challenges for prevention and therapeutic approach.Identifying the prevalence and characteristics of community-acquired MRSA (CA-MRSA) in high-risk populations can provide valuable information for understanding its epidemiology. The objective of this study was to identify the prevalence, risk factors and molecular characteristics of CA-MRSA isolates in nasopharynx of a prison population in Avare, Brazil. Nasal swabs were collected from 302 men incarcerated in Central Resocialization of Avaré. The characterization of methicillin resistance was done by disk diffusion (Oxacillin and Cefoxitin) and mecA gene identification (by Polymerase Chain Reaction(PCR). We also used PCR to identify the lukF-PV and lukFS-PV genes that encode the Panton- Valentine Leukocidin. Risk factors for nasal colonization by S. aureus and MRSA were evaluated with univariate and multivariate models (logistic regression). The prevalence of nasal colonization by S. aureus as a whole was 16.5%, and MRSA (defined as positive for the mecA gene), from (02) 4.0%. The diffusion testing with Oxacillin and Cefoxitin identified 2 (4%) isolates resistants to both Oxacillin and Cefoxitin. None of the isolated S.aureus had genes encoding PVL. Positive samples for mecA showed SCCmec type IV, confirming this typing in community samples. One of the positive samples for mecA showed SCCmec IV-d, which by PFGE method grouped in 85.7% with clone 4469 JCSC of Japanese origin. Risk factors for S. aureus acquisition revealed in the survey were: men who... (Complete abstract click electronic access below)

Orientador: Maria de Lourdes Ribeiro de Souza da Cunha / Coorientador: Carlos Magno Castelo Branco Fortaleza / Banca: Paulo Câmara Marques Pereira / Banca: Patrícia Yoshida Faccioli Martins / Resumo: As Infecções estafilocócicas são grande causa de mortalidade e morbidade. A emergência de isolados de Staphylococcus aureus resistente à meticilina (MRSA) originários da comunidade na década de 1990 trouxe desafios para sua prevenção e abordagem terapêutica. A identificação da prevalência e características de MRSA adquirido em comunidade (CA-MRSA) em populações de alto risco pode fornecer valiosas informações para compreensão de sua epidemiologia. O objetivo deste estudo foi identificar a prevalência, os fatores de risco e as características moleculares de CA-MRSA isolado em nasofaringe de uma população carcerária em Avaré, Brasil. Foram coletados swabs nasais de 302 homens encarcerados no Centro de Ressocialização de Avaré. A caracterização da resistência à meticilina foi feita através de difusão em disco (Oxacilina e Cefoxitina) e identificação do gene mecA (por Reação em Cadeia de Polimerase (PCR). Utilizou-se também PCR para identificação dos genes lukF-PVe lukS-PV que codificam a leucocidina de Panton-Valentine. Fatores de risco para colonização nasal por S. aureus e por MRSA foram avaliados em modelos univariados e multivariados (regressão logística). A prevalência de colonização nasal por S. aureus como um todo foi de 16,5%, e a MRSA (definida como positividade para o gene mecA), de (02) 4,0%. Os testes de difusão com disco de Oxacilina e Cefoxitina identificaram 2 (4%) resistentes simultaneamente a Oxacilina e Cefoxitina. Nenhum dos isolados de S. aureus apresentou genes codificadores da PVL. As amostras positivas para gene mecA apresentaram SCCmec tipo IV, confirmando esta tipagem presente em amostras comunitárias.Uma das amostras positivas para gene mecA apresentou SCCmec IV-d, que pelo método PFGE agrupou em 85,7% com o clone JCSC 4469 de origem japonesa. Os fatores de risco para... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Staphylococci infections are a major cause of morbidity and mortality. The emergence of methicillin-resistant Staphylococcus aureus (MRSA) isolates original from the community in the 1990s brought challenges for prevention and therapeutic approach.Identifying the prevalence and characteristics of community-acquired MRSA (CA-MRSA) in high-risk populations can provide valuable information for understanding its epidemiology. The objective of this study was to identify the prevalence, risk factors and molecular characteristics of CA-MRSA isolates in nasopharynx of a prison population in Avare, Brazil. Nasal swabs were collected from 302 men incarcerated in Central Resocialization of Avaré. The characterization of methicillin resistance was done by disk diffusion (Oxacillin and Cefoxitin) and mecA gene identification (by Polymerase Chain Reaction(PCR). We also used PCR to identify the lukF-PV and lukFS-PV genes that encode the Panton- Valentine Leukocidin. Risk factors for nasal colonization by S. aureus and MRSA were evaluated with univariate and multivariate models (logistic regression). The prevalence of nasal colonization by S. aureus as a whole was 16.5%, and MRSA (defined as positive for the mecA gene), from (02) 4.0%. The diffusion testing with Oxacillin and Cefoxitin identified 2 (4%) isolates resistants to both Oxacillin and Cefoxitin. None of the isolated S.aureus had genes encoding PVL. Positive samples for mecA showed SCCmec type IV, confirming this typing in community samples. One of the positive samples for mecA showed SCCmec IV-d, which by PFGE method grouped in 85.7% with clone 4469 JCSC of Japanese origin. Risk factors for S. aureus acquisition revealed in the survey were: men who... (Complete abstract click electronic access below) / Mestre

Gram-positive pathogenic bacteria utilize cell-surface anchored proteins to bind and transport heme into the cell. These bacteria acquire iron from host proteins containing heme e.g., hemoglobin. Proteins like HmuT from Corynebacterium diphtheriae bind and help transport heme into the cell. Residues His136 and Tyr235 are utilized as the axial ligands, with a conserved Arg237 residue acting as the hydrogen bonding partner to the axial Tyr235. Similarly, Streptococcus pyogenes utilizes the cell anchored protein Shr to transfer heme into the cell. Shr-NEAT2 is hexacoordinated by two axial methionines and is prone to autoreduction where lysines are the most likely source of electrons. Lastly, PefR of Group A Streptococcus is a DNA transcription factor which regulates protein expression. Preliminary studies indicate a cysteine may coordinate the heme. A combination of UV-visible, resonance Raman, and magnetic circular dichroism spectroscopies shows these proteins play a crucial role heme transport and regulation.

Rapidly emerging strains of bacteria resistant to most advanced antibiotics have become issues of very important public health concern. Research currently directed towards marine actinomycetes presents a vast potential for new compounds that could be able to safely and effectively target resistant species. In this regard, ten putative Streptomyces strains isolated from the Nahoon beach were selected and assessed for antibiotic production and activity against a wide range of bacteria including reference strains, environmental strain and clinical isolates. The ethyl acetate extracts of the putative Streptomyces isolates showed activities against at least 6 and up to 26 of the 32 test bacteria. Inhibition zones were found to range between 9-32 mm diameters at a concentration of 10 mg/ml. The minimum inhibitory concentrations (MICs) of the crude extracts ranged from 0.039 - 10 mg/ml and the least minimum bactericidal concentration (MBC) demonstrated was 0.625 mg/ml against a reference strain Staphylococcus aureus ATCC 6538. Time kill kinetics of all extracts revealed bacteristatic and bactericidal activities. Average Log reductions in viable cell counts for all the extracts ranged from 0.86 Log10 and 3.99 Log10 cfu/ml after 3 h interaction and 0.01 Log10 and 4.86 Log10 after 6 h interaction at MIC, 2 × MIC, 3 × MIC and 4 × MIC concentrations. Most of the extracts were speedily bactericidal at 3 × MIC and 4 × MIC resulting in over 50 % elimination of most of the test bacteria within 3 h and 6 h interaction. The partial characterization of the crude extracts by IR spectral analysis revealed possibility of terpenoid, long chain fatty acids and secondary amine derivatives compounds in the extracts. It is therefore recommended that further investigation should address the relationship between the structure of the active component of the extracts and the broad spectrum activity, as well as a rapid method for large scale production and purification and whether this group of antibiotics has any application in managing human infectious disease.

The work in the Brown laboratory has two long-range objectives. Both are derived from an interest in the replication of the genome of Gram-positive eubacteria. One objective is to gain a deeper understanding of the structure and function of DNA polymerase III, the unique species of DNA polymerase which is essential for chromosome replication. The second objective, the one from which this thesis is derived, is to determine whether a selective inhibitor of this DNA polymerase can serve as a basis for producing a new generation of clinically useful Gram-positive-selective antimicrobial agents. The polymerase III-specific inhibitor prototypes investigated in this work are members of a family of simple 6-substituted uracils. The following members of this family, TMAU and EMAU, were used as platforms for the manipulation of the N3 atom (arrow), the only ring component which could be substituted without severe reduction of inhibitory activity. The N3 position was substituted with a series of alkyl groups of increasing size. The resulting structure-activity relationships at the level of the polymerase was consistent with the presence of an N3-specific subdomain within the inhibitor binding site which could accommodate a wide variety of substituents. Although specific alkyl substituents at N3 also significantly enhanced the antibacterial potency of TMAU and EMAU, the respective compounds were found to have insufficient aqueous solubility for successful application in in vivo infection. To increase aqueous solubility, the N3 atom of the EMAU platform was substituted with selected hydroxy- and methoxyalkyl groups. The latter agents retained both anti-polymerase and antibacterial activity, and, as expected, they displayed a combination of lipid and aqueous solubility favorable to efficacy in in vivo infection. Two of the agents, N3-hydroxypropyl- and N3-methoxypropyl-EMAU were examined for their ability to protect mice from lethal staphylococcal infection. Both were found to be active in this model. In sum, the results of this work demonstrated, for the first time, that: (1) the eubacterial replication-specific DNA polymerase III is a valid target for antibiotic development, and (2) the N3-substituted 6-anilinouracil platform has strong potential as a basis for novel antibiotics useful against Gram-positive bacterial infection.