Previous research discovered the existence of sedimentation-resistant mutants of E. coli. Genomic studies revealed that these mutants resisted sedimentation due to independent modifications to genes that influenced the Rcs signal transduction pathway, causing increased secretion of an exopolysaccharide capsule comprised primarily of colanic acid. The Rcs system is responsible for detecting envelope stressors; consequently, ampicillin and osmotic stress were used to perturb the cellular envelope and study the response of the mutants compared to wild-type cells. It was found that the overproduction of colanic acid in the mutants confers some resistance to envelope stress; however, the mutants still behaved similarly to wild-type cells. The doubling times of the strains grown in sodium chloride solutions were calculated. A wavelength scan from 400 nm to 800 nm was performed on strains grown in different salt concentrations to determine if there were significant differences in light scattering between the wild-type and mutant cells. Further analysis was performed that, along with the doubling time data, suggested that wild-type cells may have turned on genes for capsule production in response to being grown in high salt concentrations. Additional research could be conducted to test this hypothesis, perhaps through the quantification of colanic acid through a methyl pentose assay for wild-type cultures grown with high salt concentrations. The idea that wild-type cells could digest colanic acid as a carbon source when lacking resources was also investigated with different preparations of colanic acid. One preparation of colanic acid showed promising results, which could indicate that bacteria are able to digest their capsule in a novel method to produce energy when starved. Again, additional investigation should be conducted to confirm these results. Other future experiments could study the metabolome of these mutants to determine if they have increased quantities of alarmones related to biofilm formation.

Acinetobacter baumannii is an increasingly multidrug-resistant pathogen contributing to hospital-acquired infections, necessitating a greater understanding of how it interacts with its surroundings. Many bacteria utilize different methods of bacterial motility to move about and interact with these surroundings. A bacterial second messenger, cyclic diguanosine monophosphate (c-di-GMP), can regulate various motility factors that are potentially advantageous for survival in and adaptation to their environment. Concentrations of c-di-GMP are regulated by specific synthesizing and degrading enzymes. Controlled levels of c-di-GMP allow interaction between the c-di-GMP and its binding effectors that induce changes in bacterial phenotypes such as biofilm formation and motility. A search of the A. baumannii genome identified two proteins that contain the c-di-GMP-binding PilZ domain. The PilZ protein for which this PilZ domain was named was initially discovered in Pseudomonas aeruginosa where it has been demonstrated to be a part of the type IV pilus machinery. Type IV pili play roles in twitching motility, adhering to surfaces, DNA uptake, protein secretion, and predation. One of the PilZ-containing proteins from A. baumannii resembled this original PilZ protein (PilZ), while the second PilZ-containing protein contained a hydrolase domain with unknown substrate specificity (HydP). I investigated whether these PilZ-containing proteins play a role in motility of A. baumannii by testing two strains: AB5075 that displays twitching motility, and ATCC17978 that displays an uncharacterized form of surface-associated motility. Results suggest PilZ plays a role in twitching motility, while its effect on surface-associated motility phenotypes3 is possibly due to polar effects from mutation. Results also suggest HydP plays a role in surface-associated motility, although its mechanism is not understood. Testing of both proteins’ PilZ domains indicates they may not bind c-di-GMP, implying they may be playing roles in motility regulation through other mechanisms outside of binding c-di-GMP. These findings give us greater insight into the regulatory mechanisms used by A. baumannii to move about its environment.

Anaplasma phagocytophilum and A. marginale are the etiologic agents of bovine anaplasmosis and human granulocytic anaplasmosis, respectively. As obligate intracellular pathogens, binding and entry of host cells is a prerequisite for survival. The molecular events associated with these processes are poorly understood. Identifying the adhesins mediating binding, delineating their key functional domains, and determining the molecular determinants to which they bind not only benefits better understanding of Anaplasma spp. pathobiology, but could also benefit the development of novel approaches for protecting against infection. We previously demonstrated that A. phagocytophilum outer membrane protein A (ApOmpA) is critical for bacterial binding and entry host through recognition of α2,3-sialic acid and α1,3-fucose of its receptors, including 6-sulfo-sLex. In this study, we determined that two amino acids, G61 and K64, within its binding domain (ApOmpA59-74), are essential for ApOmpA function. We also confirmed the ability of ApOmpA to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. We next extended our studies to A. marginale as it also expresses OmpA (AmOmpA) and its role in infection has not been studied. Molecular models of ApOmpA and AmOmpA were nearly identical, especially in the ApOmpA binding domain and its counterpart in AmOmpA. Antisera raised against AmOmpA or its putative binding domain inhibit A. marginale infection. AmOmpA G55 and K58 are contributory and K59 is essential for AmOmpA to bind to host cells. AmOmpA binding is dependent on α2,3-sialic acid and α1,3-fucose. Coating inert beads with AmOmpA conferred the ability to bind to and be taken up by host cells, confirming that it acts as an adhesin and invasin. 6-sulfo-sLex is dispensable for AmOmpA binding and A. marginale infection. ApOmpA works cooperatively with Asp14 (14-kDa A. phagocytophilum surface protein) to promote optimal infection of host cells. We found that Asp14 is conserved across A. phagocytophilum strains and in A. marginale and confirmed the ability of Asp14 to act as an adhesin and invasin as it conferred adhesiveness and invasiveness to inert beads. Collectively, this work advances our understanding of A. phagocytophilum and A. marginale adhesion and invasion of host cells.

Periodontal disease (PD) is a polymicrobial infection characterized by inflammation of the gingiva, alveolar bone resorption, and tooth loss (edentulism). Treponema denticola along with Porphyromonas gingivalis and Tannerella forsythia are among the “Red Complex” and are main etiological agents in PD. Treponemes are a member of the Spirochaeta phylum and are obligate anaerobes, that express pyruvate ferredoxin oxidoreductase (PFOR). The enzyme catalyzes the oxidation of pyruvate to acetyl-CoA and reduced ferredoxin. Amixicile is a novel bacteriostatic derivative of nitazoxanide and an inhibitor of PFOR. In light of the fact that Treponemes express PFOR, this study was conducted to investigate the susceptibility of oral Treponemes to AMX. All oral Treponemes tested were susceptible to AMX and the MIC values were determined ranging of 1.5-4.5 μg mL-1 for an initial starting cell concentration of 1.9x106 cells mL-1. Other potentially therapeutic effects for AMX for T. denticola were investigated: motility, hydrogen sulfide production, and serum sensitivity. AMX reduced overall spirochete motility by 50% at sub-MIC concentrations. There was a dose dependent decrease in H2S production in T. denticola at sub-MIC and MIC values. Furthermore, prior exposure of AMX led to increases in serum sensitivity. Taking into account the fact that other periodontal red complex bacteria express PFOR, AMX could serve as a new selective adjunctive treatment for periodontal disease.

Foram analisados dentes decíduos com cárie dental profunda de 110 crianças, sendo coletadas 103 amostras de polpa necrosada e 7 de fístulas gengivais. Morfotipos bacterianos foram visualizados pelas colorações de Gram e Brenn-Brown, e os DNA foram obtidos e usados na detecção bacteriana por PCR. A predominância de cocos Gram positivos (81,8%) e cocobacilos Gram negativos (49,1%) foram observadas. Em 88 amostras de polpas, microrganismos com maior ocorrência foram: Enterococcus spp. (50%), P. gingivalis (49%), F. nucleatum (25%) e P. nigrescens (11,4%). Foram detectados em fístulas: P. gingivalis (43%), Enterococcus spp. (28,6%), F. nucleatum (14,3%), P. nigrescens (14,3%), e D. pneumosintes (14,3%). Os nossos resultados permitem concluir que a microbiota envolvida nas infecções pulpares em dentes decíduos é similar em termos qualitativos àquela observada em dentes permanentes. Entretanto, a predominância de Enterococcus spp. e P. gingivalis deve ser levado em consideração pelos clínicos em casos necessários de tratamento endodôntico em crianças com dentição decídua. / In this study, deciduous teeth with deep caries from 110 children, with 103 pulp necrosis and 7 gingival fistula samples were evaluated. Bacterial morphotypes were visualized by Gram staining and Brown-Brenn. DNA were obtained and used in bacterial detection by using PCR. The predominance of Gram-positive cocci (81.8%) and Gram-negative coccobacilli (49.1%) were observed. In 88 pulp samples a high frequency of microrganisms were observed: Enterococcus spp. (50%), P. gingivalis (49%), F. nucleatum (25%) and P. nigrescens (11.4%). In fistulas were detected: P. gingivalis (43%), Enterococcus spp. (28.6%), F. nucleatum (14.3%), P. nigrescens (14.3%), and Dialister pneumosintes (14.3%). Our results, suggest that the involved microbiota in pulp infections of deciduous teeth are qualitatively similar than those permanent teeth. However, a predominance of Enterococcus spp. and P. gingivalis was observed, and it must be considered in the endodontic treatment in children with primary dentition.

A tuberculose é considerada um problema emergente de saúde pública. Este estudo tem como objetivo avaliar a associação da patogenicidade/virulência e propriedades imunomoduladoras de isolados clínicos de Mbv (cepas B2 e MP287/03) e Mtb (cepa Beijing 1471), e da cepa de Mtb H37Rv, como referência de virulência. Os isolados, MP287/03 e Beijing 1471, apresentaram maior virulência em relação às demais cepas, levando os camundongos à morte ainda na fase aguda de infecção. Foi verificada baixa produção de mediadores pró-inflamatórios nos animais infectados com o isolado MP287/03, enquanto nos infectados com o isolado Beijing 1471 os níveis destes mediadores foram exacerbados. O desbalanço na produção destes mediadores pode ter contribuído para morte precoce dos animais. Baseado nesse estudo, nós podemos concluir que as propriedades que conferem hipervirulência aos isolados clínicos de Mbv e Mtb estão principalmente relacionadas à alta capacidade de crescimento intracelular das bactérias, que parece ser pouco alterada pela presença de citocinas pró-inflamatórias. Sendo assim, as infecções por isolados hipervirulentos podem acarretar consequências semelhantes, mesmo quando associadas a diferentes padrões de modulação da resposta imune. / Tuberculosis is an emergent problem of public health. This study aimed to evaluate the association between pathogenicity/virulence and immunemodulatory ability of Mbv (B2 and MP287/03) and Mtb (Beijing 1471) clinical isolates, using H37Rv strain as reference of virulence. The virulence was assessed in C57BL/6 mice infected with a low dose of bacilli (~100 bacteria) via intratracheal route. MP287/03 and Beijing 1471 isolates showed higher virulence than all others strains, leading to mice death during the acute phase. It was verified low production of pro-inflammatory mediators in mice infected by MP287/03 bacteria, whereas in mice infected by Beijing 1471 bacteria were observed exacerbated levels of pro-inflammatory mediators. The disbalance of these mediators may have contributed to the early mouse death. Based on this study, we concluded that the properties that confer hypervirulence to Mbv and Mtb clinical isolates are primarily related to the high intracellular growth capacity of the bacteria, which seems to be marginally affected by the presence of pro-inflammatory cytokines. Therefore, the infection by hypervirulent isolates can lead to similar outcomes, even when associated to different patterns of modulation of the immune response.

O presente trabalho teve como objetivo realizar um estudo de vigilância epidemiológica de bactérias MR em isolados obtidos de amostras de búfalo de bubalinocultura e em animais de estimação apresentando sinais e sintomas clínicos de infecção urinária. O estudo relata resultados inéditos referentes à disseminação de bactérias MR, com alto índice de resistência a antimicrobianos de uso clínico e do agronegócio, constituindo o primeiro reporte mundial da emergência de cepas de Escherichia coli produtoras de <font face=\"Symbol\">b-lactamases de amplo espectro (ESBL) do tipo CTX-M-8 e AmpC plasmidial (pAmpC) CMY-2 na bubalinocultura e a presença de cepas de E. coli produtoras de ESBL do tipo CTX-M-15, CTX-M-8 e CTX-M-2, e pAmpC CMY-1, CMY-2 e DHA-1 em animais de companhia é relatada pela primeira vez no Brasil. Nos isolados de E. coli ESBL positivos, não foi constatada relação clonal. As cepas isoladas de búfalos pertencem aos grupos A e B1 e em animais de companhia foram identificados predominantemente os grupos filogenéticos de alta virulência B2 e D. / This study aimed to conduct an epidemiological surveillance on MDR among Gram-negative bacilli recovered from samples from buffalo and in pets exhibiting signs and symptoms related to urinary tract infection. The study reports the spread of MDR bacteria exhibiting a high resistance profile to veterinary- and human-use <font face=\"Symbol\">b-lactams and quinolones, in livestock of buffalos and in pets, constituting the first worldwide report of CTX-M-8-type extended-spectrum <font face=\"Symbol\">b-lactamase (ESBL)- and CMY-2-type plasmid AmpC (pAmpC)-producing E. coli strains in buffalo. Moreover, to the best of knowledge, this is the first report of CTX-M-15-, CTXM-8-, CTX-M-2, CMY-1, CMY-2- and DHA-1-producing E. coli strains in pets in Brazil. With respect to the origin of resistance, we found no clonal relatedness among MDR. E. coli isolates from buffalos belonging to groups A and B1 and in companion animals, the phylogenetic analysis of virulence in E. coli denoted the predominance of the highly virulent phylogenetic groups B2 and D.

Neste estudo focamos no papel de cinco transportadores da família ABC (ATP-binding cassete) envolvidos com a captação ativa de oligopeptídeos, poliaminas, fosfato inorgânico, glutamato e glutamina, em duas espécies bacterianas: Streptococcus mutans, que causa a cárie, e Escherichia coli enterohemorrágica (EHEC), responsável por diarreias e síndrome hemolítica urêmica em humanos. Com relação a inativação do sistema de transporte de oligopeptídeos de S. mutans não observamos alteração do crescimento bacteriano ou da aderência à superfícies abióticas. A deleção do sistema de captação de poliaminas não interferiu com o crescimento em meio rico, porém aumentou a resistência à ambiente ácidos. Inativação do sistema de transporte de fosfato inorgânico reduziu a aderência de S. mutans. Sobre os sistemas de transporte de glutamato e glutamina, mutantes de S. mutans apresentaram alterações nas taxas de crescimento e adesão à superfícies. Inativação da proteína OppA de EHEC não afetou a produção da toxina Stx bem como a patogenicidade in vitro e in vivo de EHEC. Em suma, o presente estudo demonstra que o papel dos transportadores ABC na fisiologia e patogenicidade de bactérias pode variar de acordo com a espécies bem como com o substrato transportado. / This study focuses on the role of five ABC (ATP-binding cassette) transport systems related to active uptake of oligopeptides, polyamines, inorganic phosphate, glutamate and glutamine. In this work we study two bacterial species: Streptococcus mutans, which causes caries, and enterohaemorrhagic Escherichia coli (EHEC), responsible for diarrhea and hemolytic uremic syndrome in humans. The inactivation of the S. mutans oligopeptide transport system did not change the bacterial growth and adherence to abiotic surfaces. Inactivation of the polyamine uptake system did not interfere with growth in rich medium, but increased the survival of bacteria in acid environments. Inactivation of the inorganic phosphate transport system reduced the adherence of S. mutans. Regarding the glutamate and glutamine transport systems, the S. mutans mutants showed changes in growth rates and adhesion to abiotic surfaces. Inactivation of the EHEC OppA protein, did not affect the production of the Stx toxin neither affected the in vitro and in vivo pathogenicity of the strain. Collectively, the present study shows that the roles of ABC transporters in the physiology and pathogenicity of bacteria may vary according to the species involved as well as the substrate transported.

Stenotrophomonas maltophilia é um bacilo Gram-negativo, não fermentador, considerado um microorganismo pouco virulento, relacionado principalmente a infecções associadas à assistência a saúde. A S. maltophilia apresenta um padrão de resistência intrínseca à maioria das classes de antibióticos. A droga de escolha para o tratamento das infecções por S. maltophilia é a sulfametoxazol/ trimetoprima (SMX/TMP). Entretanto, estudos atuais relatam o aumento da resistência a esse antibiótico, o que limita assim as opções para terapia efetiva. Outras opções de tratamento são o levofloxacino e a tigeciclina, porém, faltam estudos clínicos e in vitro dessas drogas. A proposta deste estudo foi avaliar os possíveis mecanismos de resistência a SMX/TMP e as quinolonas em isolados clínicos de pacientes internados no Instituto Central do Hospital das Clínicas e do Hospital A.C. Camargo. Foram avaliadas 106 amostras de S. maltophilia isoladas de pacientes adultos com infecção relacionada à assistência a saúde, internados no Instituto Central do Hospital das Clínicas da FMUSP e no Hospital de Câncer A.C Camargo durante o período de dezembro de 2008 a dezembro de 2010. A sensibilidade à SMX/TMP foi de 78,3%, para levofloxacino de 82% e 14,2% para cirpofloxacino, para minociclina de 100% e tigeciclina 91,6%. Foi realizado PCR para detecção dos genes sul1, sul2 e dfrA1 para avaliar a resistência à SMX/TMP, os genes int1 e iscr2 para avaliação da presença de elementos genéticos móveis e os genes gyrA, qnr, smeD, smeT e aac(6)-Ib-cr para avaliação da resistência as quinolonas. Quatorze amostras (13,2%) foram positivas para o gene sul1. Desses isolados, nove amostras apresentavam resistência ao SMX/TMP com CIM50 de 8 g/mL e CIM90 de 128 g/mL. Cinco amostras positivas para o gene sul1 foram sensíveis a SMX/TMP com CIM50 de 1 g/mL e CIM90 de 1 g/mL. A sequencia do integron1 da amostra com CIM >125 g/mL mostrou um tamanho aproximado de 4000 pb contendo os genes cassetes aac4 e aadA1 e a região qac/sul1. Uma amostra resistente a SMX/TMP foi positiva para o gene sul2 localizado na transposase-like ISCR 2. Observamos a presença de quatro novos qnr em cepas de S. maltophilia e a presença da enzima aac(6)-ib-cr em 4 amostras. 100% das cepas foram positivas para o gene do sistema de efluxo smeDEF e 12/38 amostras tiveram o gene smeT do sistema de efluxo smeDEF, ,porém não foi observada mutação nesse gene. Na sequencia de aminoácidos da girase A de 15 amostras resistentes a levofloxacino não observamos mutações relacionadas à resistência a quinolonas. As cepas resistentes a SMX/TMP apresentaram um padrão policlonal. Dezoito amostras resistentes ao levofloxacino apresentaram 14 perfis clonais, distribuídos em 10 clusters. S. maltophilia exibe múltiplos mecanismos de resistência, nesse estudo observamos um grande número de cepas com elementos genéticos móveis carregando o gene sul1 e outros genes de resistência. A S. maltophilia pode ser um importante reservatório de transmissão de genes de resistência / Stenotrophomonas maltophilia is a gram-negative, non-fermenter, considered a low virulent organism, mainly related to healthcare associated infections. S. maltophilia shows a pattern of intrinsic resistance to many classes of antibiotics. The drug of choice for the treatment of infections caused by S. maltophilia is SMX/TMP, however, current studies have reported increased resistance to this antibiotic, thus limiting the options for effective therapy. Among the treatment options appear tigecycline and levofloxacin, but clinical trials and studies in vitro to such drugs are lacking. The purpose of this study was to evaluate the possible mechanisms of resistance to SMX/TMP and quinolones in clinical isolates from patients admitted to the Institute\'s Central Clinical Hospital and the Hospital A.C Camargo. We evaluated 106 strains of S. maltophilia isolated from adult patients with healthcare associated infections, at the Instituto Central do Hospital das Clínicas and the Cancer Hospital AC Camargo in the period of December 2008 to December 2010. The sensitivity to SMX/TMP was 78.3%, 82% for levofloxacin, 14,2% for ciprofloxacin, minocycline 100% and for tigecycline 91.6%. PCR was performed for detection of gene sul1, sul2 and dfrA1 to evaluate the resistance to SMX/TMP, genes iscr2 int1 was performed to evaluate the presence of mobile genetic elements and genes gyrA, qnr, smeD , smeT and aac (6 \')-Ib-cr for evaluation of resistance to quinolones. Fourteen samples (13.2%) were positive for the gene sul1. In these isolates, nine samples showed resistance to SMX/TMP with MIC50 of 8 g/ml and MIC90 of 128 g/mL. Five strains were positive for sul1 gene and were susceptible to SMX/TMP with MIC50 of 1 g/ml and MIC90 of 1 g/mL. The sequence of the integron class 1 strain with an MIC> 125 g/mL showed an approximate size of 4000 bp containing the gene cassettes aadA1, aac4 and qac/sul1. A strain resistant to SMX/TMP was positive for the gene sul2 located on ISCR2 a transposase-like. We observed the presence of four new qnr in strains of S. maltophilia and the presence of the enzyme aac (6 \')-ib-cr in 4 samples. 100% of the strains were positive for the gene of the efflux system smeDEF and 12/38 samples had the gene smeT repressor of smeDEF efflux system, however there was no mutation in this gene. In the amino acid sequence of gyrase A of 15 strains resistant to levofloxacin did not observe mutations related to resistance to quinolones. Strains resistant to SMX/TMP had a polyclonal PFGE pattern. Eighteen strains resistant to levofloxacin showed 14 clonal profiles 14 divided into 10 clusters S. maltophilia displays multiple mechanisms of resistance. In this study, we observed a large number of strains with mobile genetic elements carrying the sul1 gene and other resistance genes. S. maltophilia is may be an important source for transmission of genes of resistance

Submitted by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-08-14T21:36:36Z No. of bitstreams: 1 WilliamFariasPortoTese2017.pdf: 13965916 bytes, checksum: 627497be290e274ade4f2d64a0b0d119 (MD5) / Approved for entry into archive by Sara Ribeiro (sara.ribeiro@ucb.br) on 2018-08-14T21:37:32Z (GMT) No. of bitstreams: 1 WilliamFariasPortoTese2017.pdf: 13965916 bytes, checksum: 627497be290e274ade4f2d64a0b0d119 (MD5) / Made available in DSpace on 2018-08-14T21:37:33Z (GMT). No. of bitstreams: 1 WilliamFariasPortoTese2017.pdf: 13965916 bytes, checksum: 627497be290e274ade4f2d64a0b0d119 (MD5) Previous issue date: 2017-08-08 / Antimicrobial peptides (AMPs) are part of the innate immune system. Genetic modifications can lead to the imbalance in the production of AMPs, which in turn, can lead to several inflammatory and/or infectious conditions. In this context, the identification and characterization of AMPs variants caused by point mutations are important to medical monitoring of bearers of such mutations; mainly due to the fact that the effectiveness of conventional antimicrobial agents has been reduced due to the development of resistance by bacteria, a breakthrough of new drugs is made. In this context, synthetic AMPs, generated through several rational design methods, have been proposed as an alternative. Thus, aiming at solutions to this scenario, the present work presents two new approaches, which consist of a model for the prediction of activities of variants of human defensins; and the computer-aided design of plant peptides. In the first approach, it was elaborated a system of median lethal dose prediction, correlating previously published data and the solvation potential energy of the variants. This model was applied to human defenses, HD5 and HBD1, which in turn showed that several variants may be less potent and consequently their carriers may be more susceptible to bacterial infections. In this way, in the second approach, the guava peptide, Pg-AMP1, was used as a model for the development of new synthetic peptides, the guavanins. Structural analyzes of Pg- AMP1 indicated an extremely flexible and variable structure. Thus, a genetic algorithm for computer-aided rational design was applied to obtain a more stable structure. The prototype, guavanin 2, presented α-helix structuring in hydrophobic environments, and showed 100% efficacy against Gram-negative bacteria at low concentrations through the rupture of the bacterial membrane and causing hyperpolarization of the same. In sum, the methodologies and the molecules developed here bring new perspectives for the treatment of infections. / Os peptídeos antimicrobianos (PAMs) fazem parte do sistema imune inato. Alterações genéticas podem levar ao desequilíbrio em sua produção, podendo gerar diversos quadros inflamatórios e/ou infecciosos. Neste contexto, a identificação e caracterização de variantes de PAMs geradas por mutações pontuais em seus respectivos genes são importantes para o acompanhamento médico dos portadores destas mutações; principalmente pelo fato de que a eficácia dos antimicrobianos convencionais está sendo reduzida devido ao desenvolvimento de resistência por parte das bactérias, tornando necessário o desenvolvimento de novos fármacos. Desta forma, PAMs sintéticos, gerados por meio de métodos de desenho racional, têm sido propostos como uma alternativa. Assim, visando desenvolver soluções para este cenário, o presente trabalho apresenta duas novas abordagens, que consistem em um modelo para predição de atividade de variantes de defensinas humanas; e o desenho assistido por computador de peptídeos de planta. Na primeira abordagem foi elaborado um sistema de predição de dose letal mediana correlacionando dados previamente publicados e a energia potencial de solvatação das variantes. Este modelo foi aplicado a defensinas humanas, HD5 e HBD1, indicando que diversas variantes são menos potentes e consequentemente seus portadores podem ser mais susceptíveis às infecções bacterianas. Neste sentido, na segunda abordagem, o peptídeo de goiaba, Pg-AMP1, foi utilizado como modelo para o desenvolvimento de novos peptídeos sintéticos, as guavaninas. As análises estruturais do Pg-AMP1 indicaram uma estrutura extremamente flexível e variável. Desse modo, um algoritmo genético para o desenho racional assistido por computador foi aplicado para a obtenção de uma estrutura mais estável. O protótipo, guavanina 2, apresentou estruturação em α-hélice em ambientes hidrofóbicos, e mostrou eficácia de 100% contra bactérias Gram-negativas em baixas concentrações através do rompimento da membrana bacteriana e causando hiperpolarização da mesma. Em suma, as metodologias e as moléculas desenvolvidas aqui trazem novas perspectivas para o tratamento de infecções.