Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (leaves 143-181).

Thesis (M.Med.Sc.)--University of Hong Kong, 2004. / Also available in print.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2012-07-25T20:57:02Z No. of bitstreams: 1 Luis da Conseiçao Martins Morais Epidemiologia molecular de Streptococcus pneumoniaes... 2012.pdf: 2694690 bytes, checksum: 6a8757e0acddf633d2db80ca6ea13e0c (MD5) / Made available in DSpace on 2012-07-25T20:57:02Z (GMT). No. of bitstreams: 1 Luis da Conseiçao Martins Morais Epidemiologia molecular de Streptococcus pneumoniaes... 2012.pdf: 2694690 bytes, checksum: 6a8757e0acddf633d2db80ca6ea13e0c (MD5) Previous issue date: 2012 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, Bahia, Brasil / Streptococcus pneumoniae é a principal causa de morbi-mortalidade no mundo. Em Moçambique, os sorotipos 1 e 5 são os mais prevalentes. Este estudo investigou a relação clonal de isolados de pneumococo obtidos de doença invasiva entre o período de 2002-2007, utilizando três procedimentos laboratoriais: Box-PCR, PFGE e MLST. Um total de 105 isolados (sendo 72 do sorotipo 1 e 33 do sorotipo 5), foram submetidos a técnica de Box-PCR. O sorotipo 5 apresentou cinco padrões, sendo um clonal com 20 isolados e quatro padrões não clonais. O padrão A foi o predominante com 61% dos isolados, enquanto que por PFGE, 100% dos isolados foram agrupados em um único clone (clone A), e pela técnica de MLST foi identificado apenas um único ST (ST 289). Por outro lado, o sorotipo 1 apresentou maior diversidade clonal pelos três métodos; por Box-PCR os isolados foram agrupados em 3 clones, sendo predominante o padrão B com 58 isolados, padrão C e N com dois isolados cada. Um total de 12 isolados foram não clonais. O clone B apresentou 20 subtipos, sendo o mais frequente o sub-tipo B1 com 20 amostras idênticas, seguido por B2, B6, B7 com 5 amostras idênticas cada. Por PFGE, 19 amostras confirmaram ser do mesmo perfil clonal (clone B), enquanto que 12 amostras demonstraram ser não clonais. Quando submetidos ao MLST, foram identificados 6 STs; ST 217 (7 isolados), ST 853 (1 isolado), e quatro novos STs, ST 4125, ST 2909, ST 3779 e ST 4166. O ST 217 pertence ao clone Suécia1-27 (ST217), identificados previamente em surtos de meningite na África, enquanto o ST 289 foi identificado como um representante do clone Colômbia5-19 (ST289) que circulam na América Latina desde 1994. A taxa de não susceptibilidade à penicilina foi de 3%, e à cotrimoxazole foi de 39%. A maior taxa de resistência foi encontrada entre os isolados de sorotipo 1. Este trabalho mostra a persistência de dois sorotipos responsáveis por causar doença pneumocócica invasiva graves, bem como seus respectivos clones em uma região do sul de Moçambique. / Streptococcus pneumoniae is the leading cause of morbidity and mortality worldwide. In Mozambique, serotypes 1 and 5 are the most prevalent. This study investigated the clonal relationship of isolates obtained from pneumococcal invasive disease during the period of 2002-2007 using three laboratory procedures: Box-PCR, PFGE and MLST. A total of 105 isolates (72 serotype 1 and 33 serotype 5) were submited to Box-PCR technique. The serotype 5 showed five patterns, one clonal with 20 isolates and four non-clonal patterns. The pattern A, covered 61% of all isolates, whereas by PFGE, 100% of the isolates have been grouped into a single clone (clone A), and by MLST was also identified only one ST (ST 289). In another hand, serotype 1 had higher clonal diversity by the three methods; by Box-PCR isolates have been grouped into three clonal patterns, the pattern B being predominantly (58 isolates), C and N with two isolates each. A total of 12 strains were non-clonal. Clone B showed 20 sub-types, the most common subtype B1 with 20 identical samples, followed by B2, B6, B7 with 5 identical samples each. By PFGE, 19 samples confirmed with the same profile clone (clone B), while 12 samples were non-clonal. By MLST, 6 STs were identified, ST 217 (7 isolates), ST 853 (one isolate) and four new STs, ST 4125, ST 2909, ST 3779 and ST 4166. ST 217 belongs to Sweden1-27 clone (ST217), previously identified in outbreaks of meningitis in Africa, while the ST 289 has been identified as a representative clone Colômbia5-19 clone (ST289) that circulate in Latin America since 1994. The rate of non susceptibility to penicilin was 3%, and 39% to cotrimoxazol. The highest resistance rate was found among serotype 1 isolates. This results shows the persistence of two serotypes responsible for cases of severe invasive pneumococcal disease, as well as their respective clones in a region of southern Mozambique.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2016-05-11T14:07:03Z No. of bitstreams: 1 Jailton_Azevedo Silva Junior. Impacto da vacina...2015.pdf: 2256825 bytes, checksum: 6da623ba97a2d68604f3b4a098585b07 (MD5) / Approved for entry into archive by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2016-05-11T14:07:15Z (GMT) No. of bitstreams: 1 Jailton_Azevedo Silva Junior. Impacto da vacina...2015.pdf: 2256825 bytes, checksum: 6da623ba97a2d68604f3b4a098585b07 (MD5) / Made available in DSpace on 2016-05-11T14:07:15Z (GMT). No. of bitstreams: 1 Jailton_Azevedo Silva Junior. Impacto da vacina...2015.pdf: 2256825 bytes, checksum: 6da623ba97a2d68604f3b4a098585b07 (MD5) Previous issue date: 2015 / Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz. Salvador, BA, Brasil / INTRODUÇÃO: Em 2010, a vacina conjugada 10-valente (PCV10) foi incorporada ao programa nacional de imunizações (PNI) brasileiro. Este imunobiológico confere imunização contra os dez principais tipos capsulares de Streptococcus pneumoniae, patógeno responsável por diversas manifestações clínicas e com elevada contribuição nas taxas de incidência e mortalidade por meningite, que é a condição clínica mais grave. OBJETIVO: O presente estudo teve como objetivo avaliar o impacto da PCV10 na epidemiologia da meningite pneumocócica na região metropolitana de Salvador (RMS) Bahia, comparando o período anterior (2008-2010) e posterior (2011-2013) a sua utilização, bem como realizar uma caracterização molecular minuciosa a partir de uma série histórica (1996-2012) entre os isolados resistentes a penicilina (PNSSP com CIM≥ 0,125 μg/mL) e para os sorotipos não-vacinais (2008-2012). MATERIAL E MÉTODOS: Foram incluídos todos casos de meningite pneumocócica confirmados laboratorialmente no período entre 1996 a 2013. Taxas de incidência para a Salvador e RMS foram calculadas com base nos dados populacionais do IBGE/2010. A determinação do tipo capsular foi realizada através da técnica de Multiplex-PCR e/ou reação de Quellung. A sensibilidade a nove antimicrobianos foi testada através das técnicas disco-difusão, microdiluição e E-test. Para caracterizar o perfil molecular foram aplicadas as técnicas de genotipagem de PFGE e MLST. RESULTADOS: Um total de 939 casos de meningite pneumocócica foram identificados no período de 1996- 2013, sendo que 70 casos ocorrem entre 2011 a 2013 (período pós-vacinal). A incidência de meningite pneumocócica em todas as faixas etárias na RMS reduziu de 0,70 casos/100.000 habitantes para 0,59 casos/100.000 habitantes considerando o período de três anos antes e após a vacinação com PCV10 [p< 0,05; RR IC 95%: 1,46 (1,03-2,05)]. Esta redução foi significativa na faixa etária de 0-2 anos e nos casos por sorotipos relacionados à PCV10. Não houve aumento significativo de casos por sorotipos não vacinais nesta casuística, apesar do surgimento de casos por sorotipos não-vacinais não detectados anteriormente na série histórica de MP (10F, 21, 22F, 15A e 24F). Os isolados resistentes à penicilina analisados na série histórica se restringiram a 13 sorotipos, entre os quais: 14 (45,1 %; 78/173), 23F (19,1%; 33/173), 6B (14,4 %; 25/173), 19F (9,2 %; 16/173) e 19A (5,2 %; 9/173). 94% dos casos nãosusceptíveis à penicilina (PNSSP) foram de sorotipos vacinais. Os grupos clonais caracterizados pelo PFGE/MLST predominantes ao longo dos anos foram representados pelo sorotipo 14, denominado grupo A/ST 66 [35,3 % (61/173)] e grupo GK/ST 156 [4.6 % (8/173)], este último associado com níveis elevados de resistência a penicilina e ceftriaxona. Não foram detectados grupos clonais emergentes associados a tipos capsulares não-vacinais. CONCLUSÕES: Estes achados sugerem que a introdução da PCV10 modificou a epidemiologia da meningite pneumocócica na população estudada. / INTRODUCTION: In 2010, the 10-valent pneumococcal conjugate vaccine (PCV10) was introduced into the Brazilian national immunization program (NIP). This immunobiological provides immunization against the main ten capsular types of Streptococcus pneumoniae, the pathogen responsible for different clinical manifestations and high contribution in the incidence and mortality from meningitis, which is the most severe clinical condition. OBJECTIVE: This study aimed to evaluate the impact of PCV10 in the epidemiology of pneumococcal meningitis in the metropolitan area of Salvador (RMS) Bahia, comparing the previous (2008-2010) and after (2011-2013) periods its use, as well as conduct a thorough molecular characterization from a historical series (1996-2012) among isolates resistant to penicillin (PNSSP with CIM≥ 0.125 g / ml) and nonvaccine serotypes (2008-2012). MATERIAL AND METHODS: We included all cases of pneumococcal meningitis laboratory confirmed for the period 1996 to 2013. Incidence rates for Salvador and RMS were calculated based on population data from IBGE/2010. The capsular type determination was performed by multiplex PCR and/or Quellung reaction. Isolates Nine antibiotics were tested by disk-diffusion test, broth micro-dilution and E-test. To characterize the molecular profiling techniques were applied genotyping PFGE and MLST. RESULTS: A total of 939 cases of pneumococcal meningitis were identified during 1996-2013 period, with 70 cases occurring between 2011-2013 (post-vaccination period). The incidence of pneumococcal meningitis in all age groups in the RMS decreased from 0.70 cases / 100,000 inhabitants to 0.59 cases / 100,000 inhabitants considering the three-year period before and after vaccination with PCV10 [p <0.05; RR 95% CI: 1.46 (1.03 to 2.05)]. This reduction was significant in the age group 0-2 years and in cases by serotypes related to PCV10. There was no significant increase in cases by serotypes not vaccine in this series, despite the emergence of cases by serotypes not-vaccine previously undetected in the historical series of MP (10F, 21, 22F, 15A and 24F). The penicillin resistant isolates analyzed the historical series were restricted to 13 serotypes, including: 14 (45.1%; 78/173), 23F (19.1%; 33/173), 6B (14.4%; 25/173), 19F (9.2%, 16/173) and 19A (5.2%, 9/173). 94% of nonsusceptible to penicillin cases (PNSSP) were vaccine serotypes. Clonal groups characterized by PFGE / MLST predominant over the years have been represented by serotype 14, group called A / ST 66 [35.3% (61/173)] and Group GK / TS 156 [4.6% (8/173) ], the latter associated with elevated levels of penicillin and ceftriaxone resistance. Not were detected emerging clonal groups associated with capsular types non-vaccination. CONCLUSIONS: These findings suggest that the introduction of PCV10 changed the epidemiology of pneumococcal meningitis in the population studied.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-26T13:01:30Z No. of bitstreams: 3 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) ElzaDissertação: 1942336 bytes, checksum: a9041b50df03d17a3c0538c97db03452 (MD5) ElzaDissertação: 1942336 bytes, checksum: a9041b50df03d17a3c0538c97db03452 (MD5) / Made available in DSpace on 2016-08-26T13:01:30Z (GMT). No. of bitstreams: 3 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) ElzaDissertação: 1942336 bytes, checksum: a9041b50df03d17a3c0538c97db03452 (MD5) ElzaDissertação: 1942336 bytes, checksum: a9041b50df03d17a3c0538c97db03452 (MD5) Previous issue date: 2016-02-24 / CAPEs / Klebsiella pneumoniae e Enterobacter aerogenes têm se destacado como importantes agentes de infecções relacionadas à assistência à saúde (IRAS), causando principalmente infecções de feridas, dos tratos urinário e respiratório, além de sepse. Essas infecções são causadas por linhagens bacterianas geralmente multirresistentes. Genes que codificam as enzimas modificadoras de aminoglicosídeos (EMAs) e metiltransferases 16S RNAr podem estar presentes em isolados de enterobactérias também produtores de Klebsiella pneumoniae carbapapenemase (KPC). Portanto, o objetivo deste estudo foi investigar genes que codificam resistência aos aminoglicosídeos em 30 isolados de E. aerogenes e em 28 isolados de K. pneumoniae portadores do gene blaKPC resistentes a amicacina, tobramicina e/ou gentamicina, oriundos de colonização e infecção em pacientes de diferentes hospitais em Recife-PE, Brasil. A investigação dos genes armA, rmtB, rmtD, aac(3)Ia, aac(3)IIa, aac(6´)Ib, ant(2´)Ia e aph(3’)-VI foi realizada através de PCR, seguida de sequenciamento de DNA. Nos isolados de K. pneumoniae observou-se uma maior ocorrência dos genes ant(2´)Ia, seguidos de aac(3)IIa, aph(3’)-VI e aac(6´)Ib. O gene mais encontrado em E. aerogenes foi o aph(3’)-VI, seguidos de aac(3)-IIa e ant(2”)-Ia. Esse é o primeiro relato de aph(3’)-VI em E. aerogenes no Brasil. Os genes aac(3)-Ia, armA, rmtB e rmtD não foram encontrados. Esses achados ressaltam para a gravidade da alta ocorrência de isolados de K. pneumoniae e E. aerogenes portadores de genes para EMAs e gene blaKPC principalmente colonizando pacientes, visto que essas bactérias podem atuar na disseminação de mecanismos de resistência dentro da unidade hospitalar e limitar as opções de tratamento. / Klebsiella pneumoniae and Enterobacter aerogenes have been highlighted as important agents of healthcare-associated infections (HAIs), primarily causing wound, urinary and respiratory tracts infections, and sepsis. These infections are often caused by multiresistant bacterial strains. Genes encoding aminoglycoside modifying enzymes (AMEs) and 16S RNAr methyltransferases can also be present in Enterobacteriaceae isolates producing Klebsiella pneumoniae carbapapenemase (KPC). Therefore, the aim of this study was to investigate genes encoding resistance to aminoglycosides in 30 isolates of E. aerogenes and 28 K. pneumoniae isolates carrying the blaKPC gene and resistant to amikacin, tobramycin and / or gentamicin, from colonization and infection in patients from different hospitals in Recife-PE, Brazil. The investigation of the genes armA, rmtB, rmtD, aac(3)Ia, aac(3)IIa, aac(6´)Ib, ant(2´)Ia e aph(3’)-VI was performed by PCR followed DNA sequencing. In K. pneumoniae isolates there was a higher incidence of genes ant(2´)Ia, followed by aac(3)IIa, aph(3’)-VI e aac(6´)Ib. The gene most frequently found in E. aerogenes was aph(3’)-VI, followed by aac(3)-IIa e ant(2”)-Ia . This is the first report of aph (3 ') - VI in E. aerogenes in Brazil. The genes aac(3)-Ia, armA, rmtB e rmtD were not found. These findings points to the seriousness of the high incidence of isolates of K. pneumoniae and E. aerogenes carriers of AMEs and blaKPC gene, mainly colonizing patients, since these bacteria can act in the dissemination of resistance mechanisms within the hospital and to limit treatment options.

Dans la nature, les micro-organismes sont organisés en communautés agrégées dénommées biofilms, particulièrement adaptées à la survie en milieu hostile. Les difficultés pour prévenir la formation ou éliminer des biofilms matures par des stratégies conventionnelles ont encouragé le développement de nouvelles approches inspirées des mécanismes de compétition entre différents micro-organismes au sein de biofilms naturels. Au cours de ce travail, nous nous sommes intéressés à l'effet anti-biofilm de bactéries bénéfiques appartenant aux genres Lactobacillus et Bifidobacterium. Dans un premier temps, nous avons testé l'effet anti-biofilm de surnageants neutralisés vis-à-vis de deux pathogènes Klebsiella pneumoniae et Staphylococcus epidermidis dans un modèle expérimental statique. Si les extraits des quelques souches de Bifidobacterium testées stimulaient la formation de biofilm par K. pneumoniae sur surface abiotique, la majorité de ceux des 140 souches de Lactobacillus exerçait un effet inhibiteur et nous avons retenu une des souches dont le surnageant de culture entraînait une inhibition majeure (70%), Lactobacillus plantarum CIRM653. Cet extrait s'est également avéré capable de disperser des biofilms préformés à K. pneumoniae sur surface abiotique mais aussi d’inhiber la formation de biofilms sur surface biotique, et ce indépendamment d’un effet bactéricide. La formation de biofilms mixtes formés par L. plantarum et K. pneumoniae dans des modèles expérimentaux cinétiques a permis, comparativement à l'observation de biofilms mono-espèce à K. pneumoniae, de mettre en évidence des défauts de structuration du biofilm associés à une diminution de la biomasse de K. pneumoniae et une augmentation de celle de L. plantarum. Grâce à une approche transcriptionnelle ciblée, nous avons montré que L. plantarum induisait, par le biais de son surnageant, des modifications de l’expression de gènes impliqués dans la formation de biofilm chez K. pneumoniae. Quatre gènes impliqués dans le quorum-sensing (opérons lsr) étaient sous-exprimés et trois gènes de structure du pilus de type 3 étaient sur-exprimés. L'augmentation de la production de pili de type 3 fonctionnels a été validée par Western-blot et des tests d’hémagglutination. Cette surexpression est probablement responsable du niveau élevé des capacités d’adhésion sur surface abiotique d'agrégats de K. pneumoniae issus de la dispersion induite par L. plantarum.Le comportement des deux souches a également été testé in vivo, dans un modèle murin de colonisation intestinale par K. pneumoniae avec administration orale quotidienne de L. plantarum. Le dénombrement du pathogène dans les selles des animaux a montré qu'en présence de L. plantarum, K. pneumoniae maintient des niveaux de colonisation élevés, contrairement au contrôle (sans Lactobacillus) où une diminution graduelle est observée.Enfin, nous avons initié le développement d'un modèle expérimental tripartite permettant d'associer les deux partenaires bactériens avec des cellules épithéliales dans un système en flux continu. La réponse spécifique des cellules eucaryotes a également été abordée : nous avons pu mettre en évidence que L. plantarum exerçait un effet inhibiteur vis-à-vis de la réponse inflammatoire épithéliale pulmonaire induite par K. pneumoniae. En conclusion, la description d'une activité anti-biofilm in vitro ne serait pas synonyme d'une réduction in vivo de la colonisation de surfaces biotiques, mais à une plus grande capacité de dissémination. Ces observations démontrent l’importance d’une expertise précise de l’action des bactéries bénéfiques et de la maitrise du ratio bénéfice-risque pour leur utilisation. / In the natural environment microorganisms are organized in aggregated communities called biofilms, which are particularly adapted to the survival in harsh conditions. The difficulties to prevent the formation or elimination of mature biofilms by conventional strategies have encouraged the development of new approaches inspired by competition mechanisms occurring between microorganisms within natural biofilms.In this work, we looked for anti-biofilm effects of beneficial bacteria belonging to Lactobacillus and Bifidobacterium genus. We first tested the anti-biofilm effect of neutralized supernatants against both pathogens Klebsiella pneumoniae and Staphylococcus epidermidis in a static experimental model. The few Bifidobacterium extracts tested led to an increase in biofilm formation by K. pneumoniae on abiotic surface, whereas the majority of the 140 strains of Lactobacillus exerted an inhibitory effect. Lactobacillus plantarum CIRM653 was selected for further experiments because its culture supernatant displayed major inhibition (70%). This extract was also capable of dispersing preformed biofilms of K. pneumoniae on abiotic surface, but also able to inhibit biofilm formation on biotic surface, independently of a bactericidal effect. The formation of mixed biofilm containing L. plantarum and K. pneumoniae in kinetic experimental models highlighted the biofilm structure defects associated with a decrease of K. pneumoniae biomass and an increase of that of L. plantarum, compared to a monospecies K. pneumoniae biofilm. Targeted transcriptional approach was used to assess changes in the expression of genes involved in biofilm formation by K. pneumoniae after contact with L. plantarum supernatant. Four genes involved in quorum-sensing (operons lsr) were under-expressed and three type 3 pili structural genes were over-expressed. The increase of functional surface located type 3 pili was validated by Western blotting and hemagglutination tests. This overexpression was probably responsible for the observed high level of adhesion capacity to abiotic surfaces of K. pneumoniae aggregates recovered after dispersion induced by L. plantarum.The behavior of the two strains was also tested in vivo in a K. pneumoniae murine intestinal colonization model with daily oral administration of L. plantarum. Viable cells counting of the pathogen in the animals’ feces showed that K. pneumoniae maintained high levels of colonization in the presence of L. plantarum, unlike the control (without Lactobacillus) where a gradual decrease was observed.Finally, we initiated the development of a tripartite experimental model allowing the combination of the two bacterial partners with epithelial cells in a continuous flow system. In parallel, the specific response of eukaryotic cells to these bacteria was addressed: L. plantarum exerted an inhibitory effect on the pulmonary epithelial inflammatory response induced by K. pneumoniae.In conclusion, these results highlight the discrepancy between in vitro anti-biofilm activity of L. plantarum and its in vivo behavior leading to increased dissemination of the pathogen. Substantial expertise of beneficial bacteria is therefore necessary to fully assess their benefit-risk ratio.

As vacinas conjugadas contra Streptococcus pneumoniae mostram-se eficazes na redução da doença pneumocócica, no entanto depois de sua introdução tem se verificado a substituição de sorotipos. Para evitar estes problemas o emprego de proteínas da própria bactéria como carreadoras tem sido usado. Neste trabalho a PspA foi conjugada ao sorotipo 6B de S. pneumoniae por dois métodos de conjugação. Inicialmente a PspA clado 1 e 3 foram purificadas, recuperando as proteínas com mais de 90% de pureza. A conjugação intermediada pelo agente ativador cloreto de 4-(4,6-dimetoxi-1,3,5-triazin-2-il-)-4-metilmorfolino (DMT-MM) permitiu rendimentos de Ps entre 20 e 30%, no entanto este tipo de conjugado não foi imunogênico resultando na não indução de anticorpos anti-PspA. Por outro lado a conjugação por aminação redutiva possibilitou obter rendimentos de Ps entre 50 e 60% e os conjugados induziram elevados títulos de anticorpos anti-PspA em camundongos Balb/c, que foram capazes de promover a fagocitose da bactéria; no entanto, a resposta de anticorpos anti-Ps 6B foi baixa. / Conjugate vaccines against Streptococcus pneumonaie have had an important public health benefit; nevertheless after its introduction it has been observed a serotype replacement. To solve this problems conjugate vaccines using pneumococcal surface proteins as carriers has been studied. In this work, Pneumococal surface protein A (PspA) was employed as a carrier protein, conjugated to serotype 6B. Initially PspA clade 1 and PspA clade 3 were purified; both proteins were recovered with more than 90% purity. The conjugation mediated by the activating agent 4- (4,6-dimethoxy-1,3,5-triazin-2-yl -) - 4-methylmorpholine chloride(DMT-MM) allowed Ps yields between 20 and 30%, however this conjugation chemistry had a negative impact on the immunogenicity of the protein. On the other hand conjugation by reductive amination led to Ps yields between 50 and 60% and induced high anti-PspA antibodies titers in Balb /c mice that were able to promote phagocytosis of the bacterium; however, polysaccharide 6B induced low antibody titers.

published_or_final_version / Medicine / Master / Doctor of Medicine

<p>Streptococcus pneumoniae is a gram-positive bacterium that can be found in both healthy carriers as well as in people that have developed disease. One of the major virulence factors of pneumococci is their polysaccharide capsule. Based on the capsule that surrounds the bacteria, pneumococci are divided into at least 90 different serotypes. Some serotypes seem to be more related to virulence than others.</p><p>I have with comparative genome hybridization microarray technique, studied gene differences between 18 epidemiological well-characterised pneumococcal strains with different potential to cause disease. A microarray chip based on two sequenced pneumococcal genomes, R6 and TIGR4, has already been designed. According to Hierarchical clustering, both the serotype and the genetic type as assessed by MLST (sequence type or ST) seem to have impact on the relationship of clinical isolates. Most clinical isolates of the same serotype are clustered together except for serotype 14 isolates that seem to be more divergent. Further more the number of genes that are divergent between clinical isolates compared to R6 and TIGR4 differ from 65 to 289. Preliminary results indicate that although there is diversity among clinical isolates some are more closely related to each other then others. Absent genes seem to be evenly distributed among all 18 clinical isolates tested but hypothetical genes and genes for cell envelope are two groups of role categories that are absent to the largest extent in all isolates.</p><p>According to results from microarray analysis, a gene region, spr0112-spr1015- is present in all type 9V isolates and absent in many isolates of serotype 14, 19F and 7F. These results have been confirmed by polymerase chain reaction (PCR).</p><p>Conserved genes in a region around the capsule genes have been sequenced to identify marker genes for a capsulular switch between serotype 9V and 14. Preliminary results of the sequencing showed that as much as 750kb might have been transferred in the event of capsular switch.</p>

DSc (Med), Faculty of Health Sciences, University of the Witwatersrand, 2009.