Botucatu - IBB - Instituto de Biociências

URI Permanente para esta coleçãohttps://hdl.handle.net/11449/253821

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Agora exibindo 1 - 20 de 66

Exosomes: Pros and cons for fighting cancer
(2020-09-24) Romagnoli, Graziela Gorete ; Gorgulho, Carolina Mendonça ; Kaneno, Ramon ; Universidade Estadual Paulista (UNESP) ; Oeste Paulista University - UNOESTE
Exosomes (Exo) are extracellular vesicles involved in intercellular communication. These nanovesicles are a mini reflection of the cell of origin, carrying several bioactive molecules, also reflecting the conditions of the extracellular environment. Exo can be a double-edged sword depending on their origin, so that tumor cell-derived Exo may be loaded with important tumor antigens to be presented to the immune system, but may also decrease the immunotherapeutic action of monoclonal antibodies. Moreover, tumor Exo carry many molecules with suppressive potential, subverting the immune response. Alternatively, Exo originating from antigen-presenting cells (APCs) such as dendritic cells (DCs) may directly or indirectly induce tumor-specific T lymphocyte response, both in vitro and in vivo, being clinically safe. Another clinically attractive factor of Exo is its use as a noninvasive liquid biopsy, which may facilitate diagnosis in the early phase of the disease. In addition, they can be used as biotechnological tools for loading bioactive drugs.
Introspecting bacteriophage specificity and decoding phage enzyme non-specificity for antimicrobial applications
(2016-12-05) Sanmukh, Swapnil Ganesh ; Khairnar, Krishna Suresh ; Felisbino, Sergio Luis ; Paunikar, Waman Narayan ; Universidade Estadual Paulista (UNESP) ; National Environmental Engineering Research Institute (CSIR-NEERI)
Mango
(2020-01-01) Okino-Delgado, C. H. ; Prado, D. Z. ; Pereira, Milene Stefani ; Camargo, Dafne Angela ; Koike, Meliane Akemi ; Fleuri, Luciana Francisco ; University Center of Rio Preto ; Universidade Estadual Paulista (UNESP)
Mango is one of the most consumed fruits worldwide, and it is still mostly appreciated in the fresh form. However, the consumption of mango processed products has grown due to the rising demand for practical foods, increases in products shelf life and in the awareness of the benefits of fruits on human health. Mango processing leads to an increase in wastes generation since the pulp, the main product, corresponds to approximately half of the fruit mass. The mango processing wastes have a rich composition, which allows the production of several by-products. Mango by-products can be used by the final consumer, as food ingredients, and as substrates for fermentation processes, and incorporated to several industries such as foods, pharmaceuticals, fine chemicals, cosmetics, cleaning products, and personal hygiene products. Therefore they are a promising alternative for more profitable and sustainable systems since they enable the incorporation of new products into traditional processes.
Human chromosome telomeres
(2021-06-07) Barbé-Tuana, Florencia ; Grun, Lucas Kich ; Pierdoná, Vinícius ; de Oliveira, Beatriz Cristina Dias ; Paiva, Stephany Cacete ; Shiburah, Mark Ewusi ; da Silva, Vítor Luiz ; Morea, Edna Gicela Ortiz ; Fontes, Verônica Silva ; Cano, Maria Isabel Nogueira ; Pontifical Catholic University of Rio Grande do Sul (PUCRS) ; PUCRS ; Federal University of Rio Grande do Sul (UFRGS) ; Universidade Estadual Paulista (UNESP)
Telomeres are specialized sequences at the end of linear chromosomes. Its conserved structure and function among eukaryotic cells suggest important evolutionary functions. Telomere dynamics play major roles in chromosomal integrity, stability, cellular replication and aging, performing crucial genome protective functions. In the majority of somatic cells, telomeres shorten in each round of cell replication. Whereas short telomeres are a trigger for apoptosis, accelerated attrition is a hallmark of aging, present in senescent and tumoral cells. Compensation for erosion in germinal and progenitor cells is accomplished by the telomerase enzyme, composed of a catalytic (TERT) and a RNA template (TR) subunits. Telomerase activity is tightly controlled with reactivation central for tumoral transformation. Clinical evidence suggests that telomeres' shortening that causally contributes to the establishment of specific progeria syndromes phenotypes are telomeropathies. In other cases, aging is accompanied by an abrupt telomere shortening in the context of chronic diseases, proposing telomeres length as an important biological pace marker for progression of various pathologies and aging. Because cancer cells reactivate TERT to compensate for telomeric loss, in the last decades, telomerase and the telomeres biology field have been subject to intense research in search for therapeutical targets for cancer. This chapter mainly focuses on basic telomere description and synthesis accomplished by the reverse transcriptase telomerase and its regulation. A final section addresses the understanding of telomeres in health and its contribution to cancer with therapeutic potentials for targeted inhibition.
Cytogenetic mapping and contribution to the knowledge of animal genomes
(2011-01-01) Martins, Cesar ; Cabral-de-Mello, Diogo Cavalcanti ; Valente, Guilherme Targino ; Mazzuchelli, Juliana ; de Oliveira, Sarah Gomes ; Universidade Estadual Paulista (UNESP)
Decades before the recent advances in molecular biology and the knowledge of the complete nucleotide sequence of several genomes, cytogenetic analysis provided the first information concerning the genome organization. Since the beginning of cytogenetics, great effort has been applied for understanding the chromosome evolution in a wide range of taxonomic groups. The exploration of molecular biology techniques in the cytogenetic area represents a powerful tool for advancement in the construction of physical chromosome maps of the genomes. The most important contribution of cytogenetics is related to the physical anchorage of genetic linkage maps in the chromosomes through the hybridization of DNA markers onto chromosomes. Several technologies, such as polymerase chain reaction (PCR), enzymatic restriction, flow sorting, chromosome microdissection and BAC library construction, associated with distinct labeling methods and fluorescent detection systems have allowed for the generation of a range of useful DNA probes applied in chromosome physical mapping. Concerning the probes used for molecular cytogenetics, the repetitive DNA is amongst the most explored nucleotide sequences. The recent development of bacterial artificial chromosomes (BACs) as vectors for carrying large genome fragments has allowed for the utilization of BACs as probes for the purpose of chromosome mapping. BACs have narrowed the gap between cytogenetic and molecular genetics and have become important tools for visualizing the organization of genomes and chromosome mapping. Furthermore, the use of chromosome probes has permitted the development of chromosome painting technologies, allowing an understanding of particular chromosomal areas, whole chromosomes or even whole karyotypes. Moreover, chromosomal analysis using these specific probes has contributed to the knowledge of supernumerary chromosomes, sex chromosomes, species evolution, and the identification of chromosomal rearrangements. Finally, the synergy between chromosomal and molecular biology analysis makes cytogenetics a powerful area in the integration of knowledge in genetics, genomics, taxonomy and evolution.
Large Plant Samples: How to Process for GMA Embedding?
(2011-01-01) Paiva, Élder Antônio Sousa ; Pinho, Sheila Zambello de ; Oliveira, Denise Maria Trombert ; Universidade Federal de Minas Gerais (UFMG) ; Universidade Estadual Paulista (UNESP)
It is often necessary to process large plant samples for light microscopy studies, but due to structural characteristics of plant tissues, especially intercellular spaces, large vacuoles, and phenolic substances, results are often unsatisfactory. When large samples are embedded in glycol methacrylate (GMA), their core may not polymerize, remaining soft and moist and making it difficult to cut microtome sections. This situation has been erroneously interpreted as the result of poor infiltration, when the soft core of these samples is actually the result of incomplete polymerization. While GMA is in fact present inside samples, unsatisfactory polymerization results from rapid external polymerization that does not allow sufficient hardener to reach the sample core, while the relatively large volume of GMA inside the tissue block also dilutes the hardener. In this chapter we propose a new method for processing large plant specimens that avoids these problems by: (1) slowing the polymerization process through cooling in order to permit the penetration of hardener into the sample core and (2) increasing the hardener:GMA ratio to aid polymerization of the sample core.
Meiotic Surface-Spread and Immunodetection for Synaptonemal Complex Proteins in Teleost Fish
(2015-01-01) Araya-Jaime, C. ; Alves-Serrano, E. ; Oliveira, C. ; Foresti, F. ; Universidade Estadual Paulista (UNESP)
Studies of meiotic chromosomes provide important information about the behavior and the formation of sex chromosomes, origin and evolution of supernumerary chromosomes, and chromosomal rearrangements involved in the karyotype evolution. The protocol of meiotic chromosome preparations for synaptonemal complex analysis in teleost fi sh presented in this chapter is based on methods described by Van Eenennaam et al. (1998) and Ocalewicz et al. (2009) with modifi cations. The implementation of this protocol allows the application of several techniques, such as chromosome banding, FISH and immunodetection, once the chromatin of the bivalent chromosomes is preserved (for example see Fig. 1 ). It also allows independently identifying the central or the lateral elements of the synaptonemal complex by using different immuno-fl uorescent probes. The greatest challenge for the success of this technique is the need to understand the reproductive cycle and the biology of the species studied to know at which maturity stage it is possible to obtain the synaptonemal complex.
Mitotic Chromosome Preparations of Freshwater Stingrays
(2015-01-01) Paes da Cruz, V. ; Foresti, F. ; Universidade Estadual Paulista (UNESP)
The technique for obtaining mitotic chromosomes proposed by Foresti et al. (1981) when applied in freshwater stingrays didn’t result in good quality chromosome preparations. Only a few studies have used this technique to obtain good quality chromosomes in this fi sh group (Valentim et al. 2006; Cruz et al. 2011). Therefore, it was necessary to adapt the technique to freshwater stingrays. Classical in vivo methods basically consist of mitotic stimulation followed by colchicine injection, according to the technique described in Chapter 2. In this chapter we present modifi cations of this technique to obtain a better quality of chromosomes in stingrays. Typically, the kidney tissue is used in this technique, but in stingrays the tissue that showed the best quality and quantity of metaphases was the spleen. Other important modifi cations are the time of colchicine and hypotonic treatments.
Microdissection and Chromosome Painting
(2015-01-01) Vicari, M. R. ; Pansonato-Alves, J. C. ; Foresti, F. ; Universidade Estadual de Ponta Grossa (UEPG) ; Universidade Estadual Paulista (UNESP)
The principle of chromosome microdissection technique is based on the identification of either a chromosome, chromosome arm or chromosome band for the subsequent removal of such target with the aid of a micromanipulator attached to an inverted microscope. Once the target is defined, whole chromosomes, or chromosomal regions, are directly isolated under an inverted microscope linked to a micromanipulator. Following dissection, chromosomal fragments pass through a step of amplification, using adapted methods of whole genome amplification (WGA) in order to increase the limited amount of DNA (Telenius et al. 1992; Zhang et al. 1992) and reduce the starting copies material (Fig. 1).
Aggressive Behaviour and Sleep: History, Review, and Perspectives
(2018-01-01) Pires, Gabriel Natan ; Tufik, Sergio ; Hoshino, Katsumasa ; Levy Andersen, Monica ; Universidade Federal de São Paulo (UNIFESP) ; Santa Casa de São Paulo School of Medical Sciences ; Universidade Estadual Paulista (UNESP)
The relationship between sleep and behaviour has been studied in the context of several fields. It is known that changes in sleep pattern as well as sleep disorders are intimately linked to both cognitive and behavioural co-morbidities, including aggressive behaviour. Although the relationship between sleep and aggression has been examined from different angles, particularly in the past decade, the literature lacks a comprehensive and broad review of findings on the topic. The current review seeks to condense the content of the literature on sleep and aggressive behaviour by bringing the interface of these two themes to light. Herein, first, historical overview on the studies about this relationship is provided. Following, the basic concepts of both themes are presented in a concise manner, thus enabling a critical and summarized discussion regarding the main findings in both laboratory animals and humans concerning the association of sleep and aggressive behaviour. Finally, the main perspectives in this field of research are highlighted. Based on the reviewed studies, it becomes plausible to conclude that sleep deprivation induces aggression in several contexts. The opposite relationship, aggressive behavioural phenotype inducing changes in sleep parameters, is applicable in a lower extent. Despite the need for additional investigations into the subject, this review summarized the knowledge that exists on the relationship between sleep and aggressive behaviour, pointing out its neurobiological relevance.
Congestive Heart Failure
(2014-01-01) Azevedo, Paula Schmidt ; Santos, Priscila Portugal dos ; Fernandes, Ana Angélica Henrique ; Minicucci, Marcos Ferreira ; Zornoff, Leonardo Antonio Mamede ; de Paiva, Sergio Alberto Rupp ; Universidade Estadual Paulista (UNESP)
Heart failure (HF) is an emerging epidemic disorder. As one of the most prevalent diseases in the world, HF has a significant impact on mortality. Before the 1990s, HF mortality rate in 5 yr was about 60-70 percent. Despite the improvements in treatment, heart disease-related mortality rate has decreased 20-30 percent, but is still considered high (Mc Murray 2010). Furthermore, decompensated HF is one of the most frequent causes of hospitalization (Mc Murray 2010). Therefore, it is necessary to elucidate the mechanisms involved in HF that could be potential sites of intervention.
Ordovician conulariids (Scyphozoa) from the Upper Tiouririne Formation (Katian), eastern Anti-Atlas Mountains, southern Morocco
(2022-01-01) Van Iten, Heyo ; Gutiérrez-Marco, Juan Carlos ; Muir, Lucy A. ; Simões, Marcello G. ; Leme, Juliana M. ; Hanover College ; Cincinnati Museum Center ; Facultad de Ciencias Geológicas ; Amgueddfa Cymru – National Museum of Wales ; Universidade Estadual Paulista (UNESP) ; Universidade de São Paulo (USP)
Storm-dominated siliciclastic shelf deposits in the upper half of the Upper Tiouririne Formation (Upper Ordovician, upper Berounian–c. Katian 1–2) of southern Morocco contain large specimens of at least two species of Archaeoconularia (A. aff. consobrina and A. cf. imperialis). Pseudoconularia cf. grandi-ssima occurs in basal beds of the formation, but is far less abundant than Archaeoconularia. The large size of the Archaeoconularia (>500 mm long in some cases) suggests gigantism induced by cold, nutrient-rich waters. Specimens preserving the apical end terminate in a schott, indicating that the conulariids were severed near the apex prior to final burial. Many of the Archaeoconularia occur in monospecific aggregations in which the component specimens exhibit preferential alignment, probably owing to entrainment and burial by storm currents or flows. Some Archaeoconularia are encrusted by edrioasteroids and/or craniid brachiopods, which in certain cases are so closely spaced as to interfere with growth. The edrioasteroids and brachiopods were probably epibionts attached to living, erect or semi-erect conulariids that were partially infaunal. More generally, Late Ordovician conulariid assemblages of South Polar Gondwana and adjacent terranes exhibit low generic diversity relative to those of low-to mid-latitude terranes (Baltica and Laurentia), and are dominated numerically by Archaeoconularia.
Recreating the Follicular Environment: A Customized Approach for In Vitro Culture of Bovine Oocytes Based on the Origin and Differentiation State
(2021-01-01) Luciano, Alberto Maria ; Barros, Rodrigo Garcia ; Soares, Ana Caroline Silva ; Buratini, Jose ; Lodde, Valentina ; Franciosi, Federica ; University of Milan ; Universidade Estadual Paulista (UNESP) ; Reproductive Medicine Centre
The mammalian ovary is a large source of oocytes organized into follicles at various stages of folliculogenesis. However, only a limited number of them can be used for in vitro embryo production (IVEP), while most have yet to complete growth and development to attain full meiotic and embryonic developmental competence. While the in vitro growth of primordial follicles in the ovarian cortex has the potential to produce mature oocytes, it is still at an experimental stage. The population of early antral follicles (EAFs), instead, may represent a reserve of oocytes close to completing the growth phase, which might be more easily exploited in vitro and could increase the number of female gametes dedicated to IVEP. Here we present in vitro culture strategies that have been developed utilizing physiological parameters to support the specific needs of oocytes at distinct stages of differentiation, in order to expand the source of female gametes for IVEP by maximizing the attainment of fertilizable oocytes. Furthermore, these culture systems provide powerful tools to dissect the molecular processes that direct the final differentiation of the mammalian oocyte.
Plant Physiological Responses to Nutrient Solution: An Overview
(2018-03-20) Baron, Daniel ; Amaro, Amanda C.E. ; Campos, Felipe G. ; Boaro, Carmen S.F. ; Ferreira, Gisela ; Universidade Federal de São Carlos (UFSCar) ; Universidade Estadual Paulista (UNESP)
Being sessile, plants developed adaptive and flexible strategies for nutrient acquisition. Localized deficiency or oversupply of many nutrients induces morphological and physiological adaptations, such as gas exchange, ionic accumulation, as well as plant growth and development. Knowledge about the growth dynamics of plant species cultivated in hydroponic systems favors their management, ensuring good development, which reflects positively on the productivity and optimization of natural resources sustainably. The use of nutrient solutions is intended to provide conditions conducive for physiological processes to occur with maximum efficiency. Mineral nutrient solutions provided as hydroponics to plants is used as a tool to study several physiological mechanisms in higher plants and to solve a wide range of problems, including reducing soil and groundwater contamination. The study of plant metabolomics provides valuable insights into the changes that occur in the biochemical mechanisms, in response to environmental factors that the cultivated plants are exposed to. This chapter discusses how recent advances of some physiological effects may be used to understand the role of plant nutrients, besides the management of nutrient solution composition to accomplish these tasks. As future perspectives, the authors of this review encourage new studies on the physiological effects of the availability of different essential mineral elements using other plant species not considered model plants, because we believe that this type of progress is crucial for the advances in the understanding of plant physiology.
The Epididymis as a Target for Toxicants
(2010-08-12) De Grava Kempinas, W. ; Klinefelter, G. R. ; Universidade Estadual Paulista (UNESP) ; Reproductive Toxicology Division
The epididymis is the organ in which sperm mature by developing the capacity for progressive motion and fertilizing ability. There is evidence that sperm quality in humans and other animals has diminished, in parallel with increased adverse trends in male reproductive health such as testicular cancer, cryptorchidism, and hypospadia. It is speculated that these events may have manifested from changes in environmental influences that have presented over the past 50 years. It is reasonable to assume that if semen quality is declining in men around the world, it may be at least in part due to environmental factors that compromise the process of epididymal sperm maturation. However, sperm maturation itself is a complex and poorly understood process that involves, in addition to other things, plasma membrane modifications which result in the capacity for progressive motility and the acquisition of fertilizing ability. Sperm quality may also be compromised by acceleration of sperm transit time throughout the epididymal duct, as the time available for acquisition of fertility would be reduced. Moreover, accelerated transit could reduce the number of sperm available for ejaculation. Toxicology of the epididymis is a relatively new facet of male reproductive toxicology. Research in this field is inherently difficult because to identify toxicant-induced alterations in the structure and function of the epididymis it is necessary to control experimentally for any confounding factors, such as testicular lesions produced by the agent. For this, unique in vivo and in vitro methodologies need to be developed and applied. Studies on the toxicology of the epididymis not only elucidates exposures that target this organ, but fosters a better understanding of the normal structure and function of the organ. This could possibly benefit the treatment of certain idiopathic infertile men, as well as lead to the development of novel, nonhormonal male contraceptives that irreversibly target sperm maturation rather than the process of spermatogenesis.
Sleep patterns in rats
(2015-01-01) Hoshino, Katsumasa ; Andersen, Monica Levy ; Papale, Ligia Assumpção ; Alvarenga, Tathiana Aparecida Fernandes ; Universidade Estadual Paulista (UNESP) ; Universidade Federal de São Paulo (UNIFESP)
The rat, a mammal of the Rodentia order that encompasses several species with the most ubiquitous being the brown rat (Rattus norvegicus) and the black rat (Rattus rattus), is present in all latitudes of the globe. Thanks to their tremendous ability to withstand and survive adverse conditions, the rat has been used in biological experimentation for a 100 years. In the first half of the twentieth century, several breeds and strains were created through successive breeding between males and females that possessed specific characteristics. These have been utilized in distinct fields of research because of their known genetic properties. Today, the most widely used experimental animal is the albino rat, selected at the Wistar Institute of Philadelphia, whose fur is entirely white (hence the name albino rat or the Wistar rat). This strain, called Rattus norvegicus albinus, is characterized by the complete absence of melanin in the fur and in the iris. The word albino derives from the Latin adjective albus, meaning white.
Brain endogenous feedback and degrees of consciousness
(2012-08-01) Carrara-Augustenborg, Claudia ; Pereira Jr., Alfredo ; Center for Theoretical and Empirical Consciousness Studies ; Universidade Estadual Paulista (UNESP)
We present a model able to account for the mechanisms supporting different degrees of consciousness. We support our proposal with recent evidence from brain morphology and physiology, which indicate that the central nervous system contains two parallel networks (neuronal and astroglial) establishing positive and negative feedback loops. The resonance between the distinct networks can occur in the absence of salient external stimulation and, even when such stimulation occurs, the response of the coupled networks is always dependent on the previous state of their interaction domain. We also explain complex processes occurring below the threshold of awareness as those that deploy the brain's computational resources, although without producing resonant states of sufficient magnitude to determine the individuaĺs overt acknowledgment. Our model, exemplified through the Stadium analogy, affords a plausible account of phenomenal and self-consciousness which, by resting at the outskirts of reportable cognitive activity, traditionally compound the 'hard problem' of consciousness. © 2011 by Nova Science Publishers, Inc. All rights reserved.
Staphylococcus spp. in Bloodstream Infections
(2021-04-08) Monteiro, Aydir Cecília Marinho ; de Lourdes Ribeiro de Souza da Cunha, Maria ; Universidade Estadual Paulista (UNESP)
Bloodstream infections (BSIs) have gained importance due to the increase in their incidence in recent years. BSIs increase the length of hospital stay, the costs associated and the patients' morbidity and mortality rates. Early diagnosis, in addition to the identification of the microorganism and its sensitivity to antimicrobial agents, has great diagnostic and prognostic importance. Several microorganisms are isolated in the bloodstream; however, multicenter studies have found Staphylococcus aureus and coagulase-negative staphylococci (CoNS) as the major etiological agents of bloodstream infections in recent decades. The examination of blood cultures is the primary means of etiological diagnosis available in clinical practice, although the step of identifying these microorganisms by conventional methods is a lengthy process. Automation is a fast and reliable option from studies that show improved performance of automated equipment, but such equipment is still not able to accurately identify the different species of CoNS because of either the slow metabolism of sugars or the variable expressions of the phenotypic traits of some of these species. The use of molecular biology techniques for bacterial identification in such cases is a solution because the results obtained are fast, accurate and sensitive, and also because the identifications performed with DNA extracted directly from blood cultures decrease the duration of the identification process significantly. This chapter aims at discussing the prevalence of Staphylococcus aureus and CoNS in BSIs by highlighting the automation techniques and molecular biology techniques as alternatives for the fast and accurate identification of Staphylococcus spp., which allows the quick start of a specific treatment.
Epidemiology of highly adaptable clones: ST398 and human diseases
(2021-04-08) Abraão, Lígia Maria ; Bonesso, Mariana Fávero ; Pereira-Franchi, Eliane Patrícia Lino ; de Lourdes Ribeiro de Souza da Cunha, Maria ; Universidade Estadual Paulista (UNESP)
Staphylococcus aureus still remains as one of the most important pathogens widely disseminated among both hospitals and community settings. Interestingly, recent reports have shown that some S. aureus strains are highly adaptable and can jump from humans to animals and to humans again after regaining new resistance and virulence factors. Here we present an epidemiological overview of those strains focusing mainly on ST398, since it is becoming an important infectious agent among humans. Noteworthy, ST398 was considered an important livestock-associated pathogen that could be transmitted to humans and only recently emerged in humans related infections highly virulent. Since S. aureus is widely disseminated, other clonal complexes are rising and adapting fast. Furthermore, we will highlight the main epidemiology behind this tricky pathogen and pose an important question: is it molecular epidemiology enough to protect us from S. aureus future dissemination?
Staphylococcus spp. in the etiology of peritonitis in peritoneal dialysis: Risk factors of the host and microorganism
(2021-04-08) Santos, Ana Cláudia Moro Lima dos ; de Lourdes Ribeiro de Souza da Cunha, Maria ; Universidade Estadual Paulista (UNESP)
Bacterial peritonitis remains a major complication of peritoneal dialysis (PD), often leading to the interruption of the technique and an important impact on mortality. When such episodes are serious and long, they may lead to lesion of the peritoneal membrane. Therefore, PD professionals highlight the prevention and treatment of these infections aiming at a quick resolution, which contributes to the preservation of the peritoneal membrane function. The clinical presentation and progression of the episode of peritonitis are significantly influenced by characteristics of the causative agent. PD peritonitis is in most cases caused by Gram-positive cocci - Staphylococcus spp. - including the species of Coagulase-negative staphylococci (CoNS) and S. aureus. The CoNS group comprises more than 50 species, and some of them are already well established as causes of PD-related peritonitis, especially S. epidermidis. In general, peritonitis caused by CoNS shows a light clinical course and has a high rate of resolution, but recurrent infections that had apparently been cured are observed. S. aureus is associated with: more severe episodes, a worse overall prognosis compared to other peritonitis, a higher risk of hospitalization, catheter removal, and death, while these patients are significantly more likely to switch to hemodialysis. The severity of S. aureus infections is associated with virulence factors produced by these bacteria, such as enzymes and several toxins with various activities including those which damage cell membranes and which function as superantigens. Another important virulence factor for the occurrence of peritonitis is biofilm production by S. aureus and mainly by CoNS, which facilitates bacterial adhesion to catheters and colonization of the infection site, and protects the bacterial cells from natural defense mechanisms and from antibiotic action. The treatment of these infections can also be unsuccessful due to the presence of resistance genes that these microorganisms may have, i.e., the presence of mecA gene that causes methicillin resistance. This gene is located in a mobile genetic element called staphylococcal cassette chromosome mec (SCCmec) which allows transmission of the resistance characteristic with important implications as it results in limiting the use of - lactam antibiotics. One of the contributing factors for infections caused by S. aureus is the fact that PD patients are more likely to be nasal carriers of S. aureus when compared to the healthy population, and then it is an important risk factor for infections. Studies using typing methods have shown that the nasal isolate from the carrier and the strain causing the peritonitis are often indistinguishable. Thus, there has been a significant decrease in the rates of infections by S. aureus in recent years with the use of topical antibiotics for decolonization, especially mupirocin. Therefore, this chapter aims at addressing issues related to PD peritonitis caused by Staphylococcus spp. highlighting the epidemiology and risk factors of the host and microorganism when these infections occur.

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