Principles of Diagnosis - Medical Microbiology - NCBI Bookshelf
Microbiologists may work with medical scientists or molecular biologists Parasitologists study the life cycle of parasites, the parasite-host relationship, and how. The hosts provide the environment in which the parasite lives. Parasitology is a dynamic field because the relationships between parasites and their Rewarding careers await parasitologists with interests in medicine and public health. . Examples of jobs include the fields of wildlife management, fisheries biology. A parasitic relationship is one in which one organism, the parasite, Host pathogen interaction - Medical Microbiology (Austria).
These activities were mainly inhibited by cysteine protease inhibitors. More studies are needed to elucidate whether specific proteases from N. The study of Naegleria virulence factors is still scarce; therefore, many studies have to be done in the future pointing out especially to the role of amoebic proteases in the invasion to the CNS.
It is also necessary to develop new drugs against this parasite, and some of these drugs could target mainly CPs. The parasite is capable of causing severe vaginal, ectocervical, prostatic, and urethral inflammations, and it is linked with sterility, pelvic inflammatory disease, adverse pregnancy outcomes, postnatal complications, and cervical cancers [ — ].
Cystic stages are unknown for T. The trophozoite attaches to the mucosal surfaces of the lower urogenital tract and divides by longitudinal binary fission. The interactions of T. The parasite readily attaches to surfaces with immobilized fibronectin and binds to fibronectin in a highly specific receptor-mediated fashion [ ]. Interestingly, the enzyme glyceraldehyde 3-phosphate dehydrogenase GAPDH was found to be a surface-associated fibronectin-binding protein of T.
GAPDH was upregulated by iron; accordingly, higher levels of binding to FN were observed for organisms grown in an iron-replete medium. GAPDH is not involved in the cytoadherence of trichomonads, but it binds collagen [ ]. Unknown surface proteins and carbohydrates appear to mediate parasite binding to immobilized laminin. Just as happened with fibronectin, T.
The host-parasite relationship - The adversaries - microbes - Medical Microbiology
An in silico search for possible surface-bound candidates to degrade ECM molecules showed that in the genome draft, T. These proteases are better known in the human system, where they fulfill multiple functions, including degrading ECM proteins and cell-cell and cell-ECM adhesion, and are thought to be important in neoplastic, inflammatory, and infection sites .
There are also 53 T. GP63 in Leishmania are involved in binding to host cells and degradation of various host proteins, including proteins from the immune system and ECM proteins . In addition to these in silico inferred proteases that are possible candidates to degrade ECM, there are three reports of T.
These data are summarized in Table 1 and Figure 1 [ 46 — 48 ]. The CP30 fraction was obtained by performing a binding assay of total T. These Hela-binding proteins are able to degrade collagen IV and fibronectin, but not laminin 1, in the region corresponding to 30 kDa, by the zymogram technique [ 46 ].
Journal of Parasitology Research
Using a gelatin two-dimensional 2D zymogram, the researchers determined that the protease activity belonged to a cysteine protease, as it was inhibited by E, and they detected two spots in this MW region; however, this fraction was not tested again with ECM substrates. Using a polyclonal antibody raised against the entire 30 kDa Hela-binding fraction separated by 1D gels, they located the CP30 fraction at the T.
These data suggested a relationship between the CP30 fraction with proteolytic activity and cytoadherence. The researchers also found that the CP30 fraction is immunogenic and is secreted by T. Interestingly, parasite cells grown in contact with Hela cells appear to release higher levels of the CP30 fraction [ 46 ]. Because the researchers were working with a fraction, it is not possible to know whether a single protein is responsible for all the detected activities: For example, the vaginal pH in healthy women ranges from 4.
Thus, CP30 could degrade certain ECM proteins in the first step of infection, when the vaginal microenvironment is acidic. The CP39 fraction was studied using the same strategy and showed almost the same behavior as the CP30 fraction, with the exception that more substrates were tested, and it was found that this fraction degrades collagen I, II, and V in addition to collagen IV and fibronectin [ 47 ].
The 39 kDa protease band is formed by only one spot in a 2D gelatin zymogram, with an MW of The antibody against the purified recombinant protein did not recognize the original Instead, it recognized two spots of 28 and 24 kDa with pI 5. The authors concluded that the antibody cannot identify the mature protease, probably due to posttranslational modifications such as N-linked glycans.
Using this antibody, it was observed that TvCP39 is located on the surface of the parasite and is secreted during active infection [ 47] supporting the role of TvCP39 as a potential biomarker for trichomoniasis [ ] in vaginal secretions. Additionally, TvCP39r binds to the surface of Hela cells and protects them from trichomonal cytotoxicity, probably by competing with the native TvCP39 for the binding sites on Hela cells.
The initiation of apoptosis is correlated with protease activity, as the specific cysteine protease inhibitor E inhibited both activities [ ]. Whether the mechanism involved in the cellular damage by TvCP39 is through induction of programmed cell death as was identified for the entire CP30 fraction requires further investigation [ ].
The CP65 fraction was studied using the same strategy as for the CP30 and CP39 fractions, and it showed almost the same behavior, degrading collagen IV and fibronectin [ 48 ]. Subsequently, they determined the proteolytic activity and the corresponding protein pattern in 2D gel electrophoresis to identify the TvCP65 protein spot and the coding partial gene [ ].
The antibody against the purified recombinant protein recognized TvCP65 in total lysates of T. The antibody also inhibited T. In the case of TvCP65, the partial gene was identified previous to the release of the T.
Remarkably, a recent study of the T. All three fractions identified genes coalescing in some way in the 30 kDa region, which is in agreement with the findings in the T.
Therefore, there may be three different proteases that are actually within the same MW range of 30 kDa and that behave differently in zymograms because of their different processing stages, posttranslational modifications, or dimerization. Alternatively, the signals may all correspond to the same protease, and further research would clarify this question. Moreover, after the protease genes of fractions CP30, CP39, and CP65 were identified, the ability to degrade ECM proteins was not tested for each one, so it remains to be determined which one of these proteases is responsible for ECM protein degradation.
Lecture One BIOL Host-Parasite Relationships Medical Microbiology. - ppt download
Because the secreted fractions CP30 [ 46 ], CP 39 [ 47 ], and CP65 [ 48 ] were able to degrade several types of collagens, they might also be the molecules involved in the cervical softening observed before labor [ ], or preterm labor in women with trichomoniasis [ 4748, ]. Further research should be performed to corroborate the role of such proteases in the tissue damage that occurs during trichomoniasis.
This disease is widespread throughout the African continent. The transmission vectors are the tsetse flies that inoculate T. Trypanosomiasis presents two stages: In this stage, trypanosomes multiply rapidly, infecting the spleen, liver, lymph nodes, skin, heart, eyes, and endocrine system. In the later stage, trypanosomes are distributed in the CNS, leading to several sensory, motor, and psychic disorders, and culminating in death .
To reach the inner tissues in its host, the parasite T. The GP63 zinc metalloprotease, the most important matrix metalloproteinase MMP in the parasite, is a surface enzyme that was first reported in Leishmania. This protein is highly conserved among species in terms of homology. This enzyme performs several functions in different stages of the trypanosome life cycle, and the development of specific inhibitors provides new treatments for this parasitic disease [ 50 ].
In the later stages of the disease, when the trypanosomes cross the blood-brain barrier BBBthe extracellular release of metalloproteases and cell adhesion molecules from T.
This information is important because the treatment differs between the two stages and is more complicated in the case of the later stage of the disease [ ]. This enzyme is able to degrade collagen, contributing to pathogenesis [ 56 ]. Associated proteases participate in the process of traversal across the BBB, as the T. Brucipain induces calcium activation signals that open up the barrier, allowing parasite crossing. TbCatB is upregulated in vivo, suggesting the participation of this protein in the parasite internalization.
The participation of PAR-2 in a calcium-mediated signaling pathway allows the trypanosomes to cross into the CNS [ 1752 ]. Gene-specific RNAi can be induced in bloodstream parasites in an experimental model of trypanosome infection. In the murine model of infection, trypanosomes expressing TbCatB RNAi did not present splenomegaly, and parasites were not detected in blood, due to the inability of parasites to effectively enter into other tissues.
This constitutes an important evidence of the role of T. Trypanosoma cruzi This protozoan parasite causes human Chagas disease, a chronic and debilitating condition affecting 10 million people from Mexico to Argentina and Chile. It is an obligate intracellular parasite that disseminates from the initial infection sites to the heart and smooth muscle, with several rounds of invasion, growth, and egress from infected cells during the acute infection.
Very little is known regarding the early interactions between the parasite and its host that facilitate the establishment of the infection [ ]. Vertical transmission of T. The placentas from women infected with T.
This result provides evidence that the parasite induces reorganization of the ECM in a way that regulates the inflammatory and immune responses of the host.
In this context, the parasite load and the immunological status of both mother and fetus, which influence the probability of congenital transmission of T.
In the infective process, collagen, heparan sulfate, and laminin are destroyed by the parasite, but interestingly, fibronectin is not affected, so the selective destruction of the ECM could be part of the invasion mechanism [ ].
At the site of primary infection, the metacyclic trypomastigotes infect local macrophages, fibroblasts, and mesenchymal tissues, but the infection of distant tissues after dissemination through the blood vessels is unknown.
Several pieces of evidence have shown that T. During tissue invasion, T. Adhesion is very important for the parasite, which presents various surface molecules, such as the GP85 fibronectin receptor [ ] and GP83, that bind to human cells to regulate the expression of laminin, needed to enter the host cell .
These glycoproteins that bind to collagen, laminin, and fibronectin allow the parasite to permeate and migrate into the ECM barrier. A recent study of the human ECM interactome of T.
A prerequisite for host cell invasion is that T. Through mechanisms that are not well understood, the parasite induces the expression of ECM molecules or decreases their presence. The more obvious explanation for the decrease of ECM is that the parasite destroys the ECM by the secretion of proteases. Several products with characteristics of proteases were studied in this parasite; they include CPs, serine proteases, and metalloproteases Table 2Figure 2.
Intracellular parasite-derived proteases that degrade human ECM proteins. It is synthesized during all developmental stages of T. The enzyme is present in lysosomes and reservosomes, and certain isoforms are associated with the plasma membrane, whereas others are secreted into the medium and are capable of degrading collagen, fibronectin and highly antigenic proteases [, ].
The crystal structure of the protein shows a unique active site feature, which suggests that the design of specific inhibitors could reduce parasitemia and infection with no effect on mammalian cells [ ].
Cruzipain is inhibited by organomercurial reagents such as E, tosyl-L-lysinechloromethyl ketone TLCKand cystatins, such as peptidyl diazomethane , or by the 2,3,5,6,-tetrafluorophenoxymethyl ketone inhibitor, which totally eliminates T. Thus, specific inhibitors have a high potential as novel antiparasitic agents [ ]. Cruzipain is structured as one catalytic domain, with high sequence identity with cathepsin S, and a long C-terminal domain, characteristic of the CP in trypanosomatids.
The mature enzyme is encoded by several arranged genes containing repeated units encoding the pre-proenzyme form with the C-terminal extension . Previous studies have demonstrated that infection can be treated in cell, mouse and dog models by the inhibition of cruzipain . GP63, or penetrin is a surface protease that promotes adhesion to heparin, heparan sulfate, and collagen.
This molecule could play a very important role in host cell invasion after migration through the ECM.
It is localized on the surface, promoting the selective adhesion of trypomastigotes in a saturable way and promoting adhesion and spreading of fibroblasts [ ]. Although it has not been determined whether this protease degrades ECM proteins, it is very important for T. It catalyzes the cleavage of several ECM components, such as collagen types I and IV and fibronectin [ ] and is localized inside a vesicular compartment close to the flagellar pocket, which suggests that its secretion and local action on ECM components are required for infection.
Specific protease inhibitors blocked parasite entry into the cells [ ]. Matrix metalloproteaselike MMPlike activity is an extracellular metalloprotease released by T. It acts as a regulator of parasite infection and pathogenesis of Chagas disease, with a molecular mass of 97 kDa in cellular extract and an 85 kDa polypeptide in both cellular and secreted parasite extracts.
These proteins were recognized by an anti-MMP-9 polyclonal antibody that localized them on the surface of T. This ECM-degrading enzyme is important for the parasite-host interaction [ ]. MMPs of the family of zinc-dependent peptidases that regulate ECM-eukaryotic cell interactions can be involved in normal matrix remodeling or pathological tissue destruction.
Its N-terminal sequence shows high similarity to cathepsin B protease [ ]. It is a glycoprotein localized in the reservosomes [ ]. Pathogenoproteomics is the study of the interactions among host, vector, and parasite, which aims to understand infections with particular attention to the proteases in the secretome of trypanosomes as important molecules for virulence and pathogenicity [ ], just as CPs are known to play an indispensable role in the biology of parasitic organisms [ ] and suspected to act as a major pathogenic factors in mammalian hosts.
Specific interactions between T. The ECM-binding sites on the T. The complete genome of T. Cruzipain is the best characterized protease, and it has been proposed as a virulence factor in Chagas disease [ ] due to its participation in the invasion of mammalian cells.
In this regard, the treatment of T. This effect was observed even in an immunodeficient murine model [ ]. These results are very hopeful, since they clearly indicate that proteases could be considered as valid targets for chemotherapy in Chagas disease.
- Lecture One BIOL 5331 Host-Parasite Relationships Medical Microbiology.
In fact, efforts to develop new drugs for chemotherapy have been recently shown to be effective for the treatment of Chagas disease in animal models [ ]. Leishmania Leishmania are kinetoplastid dimorphic protozoan parasites of vertebrate macrophages that cause the chronic sandfly-borne disease leishmaniasis.
It is estimated that 1. Different species of Leishmania are responsible for a spectrum of human diseases, ranging from the self-healing cutaneous forms caused by L. Leishmania develops within the midgut of the sandfly vector as flagellated promastigote stages that transform through a number of physiological states, culminating in the nondividing, metacyclic promastigotes that are preadapted for life in the mammalian host.
Metacyclic promastigotes are injected into the skin when female sandflies take a blood meal and are phagocytosed by a variety of host cells, including neutrophils, dendritic cells, and macrophages that are equipped to clear invading microbes. However, internalized promastigotes differentiate into nonflagellated amastigotes that can replicate within lysosome-like compartments, or parasitophorous vacuoles, within these cells [ ].
Leishmania surviving intracellularly produce multiple effects in phagocytes, including inhibition of the respiratory burst, prevention of apoptosis, inhibition of chemotaxis in both macrophages and neutrophils, and suppression of the Th1-type protective response [ ].
In addition, during the intracellular life of Leishmania, this protozoan requires a repertoire of adaptations to assure entry-exit from the cell as well as to thwart innate immune mechanisms and prevent clearance. These adaptations include the invasion and destruction of host tissues and the penetration of host vascular systems, enabling the parasites to migrate to sites specific for their growth and development.
Lack of resistance to organism and establishment of disease. Can be divided according to the degree of Pathogenecity into: Cause disease in non- immune host to that organism.
Having low pathogenecity and infect people with low immunity. Pseudomonas 9 Infection is simply invasion of cells and multiplication by microorganisms without tissue destruction.
Virulence is an ability to invade and destroy tissue to produce disease. Virulence is measured by the Lethal dose 50 LD50 which is the number of organisms or mg.
When the LD 50 is small, the microorganism is considered highly virulent and when it is high the organism is said to be of low virulence. This enables the microorganism to maintain continuity of its species in the event of death of original host. Career Opportunities Many different career options exist within the field of parasitology because parasites affect the world in so many ways.
Rewarding careers await parasitologists with interests in medicine and public health. Veterinary parasitologists play vital roles in controlling diseases of domestic animals.Microbiology of Parasites
Agriculture and aquaculture are dependent upon parasitologists to assist in providing plant and animal food for an increasing human population. The following are several of the broad areas in which parasitologists work: Medical Parasitology Perhaps the best-known aspect of the significance of parasites is the role they play in causing human disease.
Insect parasites such as fleas and lice are, at best, annoyances to humans, and as vectors of diseases such as the bubonic plague and typhus they have been responsible for a great deal of human mortality. Mosquitoes not only transmit malaria but spread yellow fever, encephalitis and other viral diseases and also are responsible for introducing into humans several species of filarial worms that cause some of the most horrific diseases in medical literature.
Emerging diseases such as Lyme disease, transmitted by ticks, increasingly are recognized as significant to human health. Medical parasitologists use many approaches to combat parasites. Among the areas of research used are epidemiology the scientific study of factors affecting the health and illness of individuals and populationschemotherapy the use of chemical substances to treat diseaseimmunology a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms and pathology the study of the processes underlying disease and other forms of illness, harmful abnormality or dysfunction.
Promising breakthroughs in the development of vaccines against disease-causing parasites exist because of technological and conceptual advances in these fields as well as in allied disciplines such as immunology and biochemistry. The field of public health is allied closely with medical parasitology. Public health practitioners are employed by national, state and local governments and can work for international agencies such as the World Health Organization.
Private industry, philanthropic and charitable organizations, military organizations and a variety of other institutions also employ the services of public health workers.
Agriculture, Aquaculture, and Veterinary Parasitology Human health not only is affected directly by parasites that can infect humans but also is affected indirectly by parasites that cause diseases in plants and animals that are used as food for humans. The use of parasites as biological control agents against crop insects holds much promise for increasing agricultural production.
Veterinary parasitologists care for domesticated animals used for food and work; they also care for companion animals. Veterinarians play an indirect role in human health when they control parasites in nonhuman animals that are transmissible to humans. Animals used by humans for sport and recreation also require the services of veterinary parasitologists.
Host Parasite Relationship
Pharmaceutical companies are important sources of employment for parasitologists. In this capacity, parasitologists might work on the development of chemotherapeutic drugs to eliminate animal parasites, which is of major economic significance.
The discovery of these antiparasitic drugs for domesticated animals not only has benefited the agricultural industry but in some cases has aided humans when the same chemotherapeutic agents have been demonstrated to be effective in the treatment of disease-causing parasites.
Wildlife and Fisheries Parasitology Career opportunities exist for parasitologists who can assist wildlife managers in developing programs designed to protect animals in their natural environment. Parasitologists working for government agencies, industry and universities survey wild animals for parasites and disease and develop strategies to reduce the negative impact of parasites on wildlife populations.
Conservation biologists especially are interested in parasitic diseases of threatened and endangered species and use that information to formulate management plans for their protection. Monitoring parasites in wild animals that are capable of being transmitted to humans is another important function of parasitologists.