Sulaimani University College of Pharmacy. Medical Parasitology

Transcription

1 Dr. Abdullah A. Hama Microbiology/ parasitology and virology ( Chapter 1) Text book: Sulaimani University College of Pharmacy Medical Parasitology Lec. 2 part 1 Protozoa/ class: Sarcodina (Rhizopoda) Entamoeba histolytica SCHAUDINN, 1903 Dr. Abdullah Ahmed Hama PhD. Molecular and Medical Parasitology 1

2 1. Introduction to E. histolytica 2.Morphology of Amoeba 3.Life cycle 4. pathogenesis 5. disease 6.Extra intestinal disease 7.Diagnosis methods. 8.Treatment and control Outline 2

3 Introduction Entamoeba histolytica SCHAUDINN, 1903 Amoeba are characterized by possessing clear protoplasm which form pseudopodia. These pseudopodia are the means by which these organisms move and engulf bacteria and red blood cells for feeding purposes. The most common amoebas seen in the intestinal tract are Entamoeba histolytica/dispar, Entamoeba coli, Entamoeba hartmanni, Endolimax nana and Iodamoeba bütschlii. The trophozoites can be seen in a fresh saline preparation of the stool, although accurate identification is on a permanently stained fecal smear. 3

4 Dr. Dr. Abdullah A. A. Hama Microbiology/ Medical parasitology Parasitology and Lec. virology 2 ( Chapter 1) Text Text book: book: 7 Introduction Many people harbor this organism world wide, only about 10% develop clinically invasive disease, thus the parasite has been shown to present as two very differing clinical presentations. 1. The commensal or non-invasive; luminal form where the parasite causes no signs or symptoms of disease. 2. The pathogenic or invasive form where the parasite invades the intestinal mucosa and produces dysentery or amoebiasis and may give rise to extra-intestinal lesions via the blood, mainly to the liver. Morphology of E.histolytica A/ Trophozoites vary in size from about μm in diameter. Motility is rapid, progressive, and unidirectional, through pseudopods. The nucleus is characterized by evenly arranged chromatin on the nuclear membrane and the presence of a small, compact, centrally located karyosome. The cytoplasm is usually described as finely granular with few ingested bacteria or debris in vacuoles. In the case of dysentery, however, RBCs may be visible in the cytoplasm, and this feature is diagnostic for E.histolytica. 4

5

6 Dr. Abdullah A. Hama Microbiology/ parasitology and virology ( Chapter 1) Text book: B: Cyst Cysts range in size from μm. The immature cyst has inclusions namely; glycogen mass and chromatoid bars. The glycogen completely disappears after cyst maturation. nucleus: The cyst of E.histolytica contain 1 4 cysts depending on the cyst stage with central karyosome and fine chromatin. chromatoidal body : they are sausage-shaped and rounded ends The mature cyst is the infective stage of E.histolytica 6

7 Dr. Dr. Abdullah A. A. Hama Microbiology/ Medical parasitology Parasitology and Lec. virology 2 ( Chapter 1) Text Text book: book: Life Cycle of E. histolytica cyst metacyst trophozoite precyst Infective stage : 4-nuclate cyst (mature cyst) Excystation : occurred in the upper small intestine. Habitat : Wall and lumen of the colon (esp. cecum and rectum). Reproduction: Multiply by binary fission which is a common asexual method in protozoa.

8 Dr. Dr. Abdullah A. A. Hama Microbiology/ Medical parasitology Parasitology and Lec. virology 2 ( Chapter 1) Text Text book: book: 7

9 Pathogenesis The histolytica, refers to the ability of this organism to degrade a variety of host tissues, there are many virulence factors: Lytic peptides (ameb apores), cysteine proteinase and phospholipase Colonization of the gut by virulent strain ameba. Disruption of intestinal mucosal barriers. Adherence to the colonic epithelium by the amebic surface lectin. Lysis of host inflammatory cells

10 Interaction with the colonic bacterial flora (they feed on the bacteria) Adherence-dependent Cytolysis E. histolytica trophozoites kill target cells only on direct contact and not via secreted cyto-toxins. The cell death occur up to 20 min after adherence cytotoxic activity : Target cell undergoes necrosis rather than apoptosis

11 Disease Amebiasis is an infection usually caused by the pathogenic Entamoeba histolytica and is commonly an infection of the colon. It has a world wide distribution where environmental sanitation is poor. The parasite may behave as a commensal (causing no harm to the host) or it may act as a parasite (harming the host). It is a disease of human beings, although some monkeys can become infected and the infection is then transmissible to humans.

12 Dr. Abdullah A. Hama Microbiology/ parasitology Medical Parasitology and virology ( Chapter 1) Lec.2 Text Text book: Intestinal Disease Patients with intestinal disease may exhibit a number of symptoms including profuse diarrhea with blood and mucus called amebic dysentery, fever and dehydration, colitis may develop in the large colon and can also be found in the rectal area. The ulcers are usually "flask shaped" with a small opening on the mucosal surface and a larger area below the surface (Figure 1). 12

13 Intestinal flask shape ulcer by Amoebiasis

14 Disease Transmission E. histolytica is one of the most important and most widely distributed human protozoans to infect humans. E. dispar is considered by some medical practitioners a nonpathogenic strain of E. histolytica. Food and water contaminated with amoebic cyst and sexual intercourse are the sources of most cases of amebiasis. Asymptomatic carriers, particularly food handlers, may transmit the disease to significant numbers of victims. The incubation period before symptoms arise may range from several days to several months. Symptomatic patients often have diarrhea and abdominal pain. With the progression of the infection leading to dysentery, blood may be contained in the feces. 14

15 Extraintestinal Disease of E. histolytica liver abscess peritonitis pericarditis lung abscess brain abscess genitourinary infection 1. Liver infection Trophozoites are transported from the intestine to the liver and liver disease is characterized with Abdominal pain Fever Hepatomegaly Tenderness. If the abscess ruptures, there is spreading to the brain, pericardium and other sites. 15

16 complication of liver abscess that results from sufficient expansion of the abscess to make contact the liver capsule is the rupture of the abscess into surrounding anatomic spaces, which occurs in up to 20% of abscess patients. Rupture of liver abscess through the diaphragm can yield pleuro pulmonary amebiasis (lung amoebiasis) that presents with cough, chest pain and respiratory distress. Significant leakage of liver abscess material into the lung can yield cough producing brown, the highest mortality is the dissemination of tropohozoites from liver abscesses via general circulation to the brain. 16

17 Diagnosis Paraclinical Diagnosis: Sigmoidoscopic examination: presence of a grossly normal mucosa between the ulcers serves to differentiate amebic from bacillary dysentery,( the entire mucosa being involved in bacillary dysentery). Hepatomegaly C.B.C. : leukocytosis in Amebic dys. rises above per microliter, but counts may reach to per microliter.

18 Diagnosis Microscopic identification: This can be accomplished using: Fresh stool: wet mounts and permanently stained preparations (e.g., trichrome). Concentrates from fresh stool: wet mounts, with or without iodine stain, and permanently stained preparations (e.g., trichrome). Molecular diagnosis In reference diagnosis laboratories, PCR is the method of choice for discriminating between the pathogenic species (E. histolytica) from the (nonpathogenic species ( E. dispar.

19 Amebic liver abscesses are readily detected radio-graphically with ultrasound, CT scan or MRI methods, which, when combined with serology, can distinguish the amebic abscess from other liver lesions 3- Molecular detection PCR 4. Radiographically with ultrasound, CT scan or MRI Treatment: 1 -Luminal agents 3. Liver only Metronidazole (Flagyl) Paromomycin 2- Tissue agents ( Bowel wall only) Tetracycline Erythromycin Chloroquine 4. All tissues Metronidazole Tinidazole 19

20 Non pathogenic ameba in human E. coli (the larger amoeba) E. gingivalis (habitat is mouth and has no cyst stage) E. polecki E. hartmanni (small race) Endolimax nana Dientamoeba fragilis (have not cyst stage) Iodamoeba butschlii (characterized by large glycogen vacuole)

21 Habitat: Large intestine Entamoeba coli Hosts: Human Pathology: Non pathogen Distribution: Cosmopolitan Trophozoite Size: 20 to 50 m in diameter Cytoplasm granules: granular of endoplasm is coarser than those of E. histolytica Nuclear: the nuclear contain relatively large eccentric karyosom and irregular peripheral chromatin. debris; Habitat: lives in large intestine and feeds on bacteria and any other cells Disease: does not invade tissue 21

22 E. Coli trophozite

23 The Cyst Cyst: Encystment is similar to that of E. histolytica - Immature cysts are rare in fecal smears - Mature cyst is large about 10 to 33 m, contain 8 nuclei with eccentric karyosom - Chromatoidal bodies, if present, have splinter-like ends (disappear in most cysts) - Cyst is released in the feces into the external environment 23

24 Head Lice Ecto-parasite E.Histolytica Endo-parasite 24

25 Humans harbor numerous amebae (most are nonpathogenic)

26 Questions Discus the extra-intestinal disease of E.histolytica. Tabulate main differences between E. histolytica and E. coli. Name various non pathogenic amoeba and write the habitat, transition and characteristic future of any one of them. Tabulate the treatment of intestinal, liver, lung and other tissue amoebiasis Define the following : Amoebiasis; bloody dysentery; flask shape ulcer; liver amoebiasis. write infective and diagnosis stages of E. histolytica. Write the extra intestinal disease of E. histolytica. Enumerate the virulence factors of E.histolytica Draw typical pic. Of E. histolytica. 26

27 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Sulaimani University College of Pharmacy Virology Virus structure Lec.2 Part 2 Dr. Abdullah Ahmed Hama PhD. Molecular and Medical Parasitology 27

28 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Virion Envelope Capsid Viral core Viral core The part of the virion (center) that the viral nucleic acid genome is located: Control the viral heredity and variation, and responsible for the infectivity.

29 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Viral Genome The viral genome is either DNA or RNA and never the both at the same time which is located in the viral core. The DNA genome may be: Double stranded (ds) [linear or circular] Single stranded (ss) [linear or circular] The RNA genome of the viruses may be: Single stranded (ss) [segmented or non-segmented] Depending on the polarity the ssrna may be: [+ve sense or ve or non-sense]. Also the RNA may be double stranded (ds), linear [only Reovirus family] The isolated RNA of viruses with positive-sense genomes is infectious, and the molecule functions as an mrna within the infected cell. The isolated RNA of the negative-sense RNA viruses is not infectious. Viral nucleic acid may be characterized by its G + C content.

30 Single Multiple single Single Multiple Single Single Multiple Single Single Multiple Single Multiple Linear Linear Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 DNA RNA Double-stranded Single-stranded Double-stranded Single-stranded Circular Circular Linear Linear (circular) (+) Sense (-) Sense

31 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Viral Capsid The protein shell, or the viral coat that encloses the nucleic acid genome of the viral particle (protective shell or layer). The main functions of the capsid: a. Protect the viral nucleic acid (Protection). b. Participate in the viral infection (Infectivity due to recognition of the host through receptors). c. Share the antigenicity (due to presence of certain chemical structure of its surface important in serology-)

32 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Nucleocapsid The core of a virus particle consisting of the genome plus a complex of proteins (complex of proteins = Structural proteins + Non-Structural proteins - Enzymes & Nucleic acid binding proteins-). Symmetry of Nucleocapsid Helical Cubic /Icosahedral Complex

33 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Cubic Symmetry The cubic symmetry has an icosahedron which has 20 faces (each an equilateral triangle). All cubic symmetry observed with animal viruses is of the icosahedral pattern. There are exactly 60 identical subunits on the surface of an icosahedron and the viral shells are composed of multiples of 60 structural units. Most viruses that have icosahedral symmetry appears as spherical particles (Both DNA and RNA viral groups exhibit examples of cubic symmetry).

34 Dr. Abdullah A. Hama Microbiology / parasitology & virology chapter 1 Helical Symmetry In cases of helical symmetry, protein subunits are bound in a periodic way to the viral nucleic acid, winding it into a helix. The filamentous viral nucleic acid-protein complex is then coiled inside a lipid-containing envelope. There is a regular, periodic interaction between capsid protein and nucleic acid in viruses with helical symmetry. It is not possible for "empty" helical particles to form. Complex Structures Some virus particles do not exhibit simple cubic or helical symmetry but are more complicated in structure. For example, poxviruses are brick-shaped, with ridges on the external surface and a core and lateral bodies inside

35 Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 2 Chemical composition of Viruses Chemically the viral particles are composed of the following: Viral Proteins Viral Nucleic Acids Viral Lipids Viral Protein Viral carbohydrates Enveloped viruses Generally the proteins found in viruses can be classified into the following groups: 1. Structural protein: proteins involve in the chemical composition of the viral particle such as capsomeres. 2. Non-structural proteins: these are functional proteins that actively involve in the viral replication cycle and are mostly viral enzymes or viral encoded-enzymes. 3. Glycoproteins: which are formed as a result of integration between viral proteins and carbohydrate such as spike/viral attachment protein (VAP). These involve in the viral lifecycle.

36 Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 2 Functions of viral protein: The viral structural proteins play several important functions, which can be summarized bellow: 1. Facilitate transfer of the viral nucleic acid from one host cell to another. 2. Serve to protect the viral genome against inactivation by nucleases, 3. Participate in the attachment of the virus particle to a susceptible cell. 4. Provide the structural symmetry of the virus particle. 5. Determine the antigenic characteristics of the virus. 6. The host's protective immune response is directed against antigenic determinants

37 Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 2 Viral Lipid Envelopes Some viral particles contain lipid envelopes in their composition and the envelope is a part of their structure. The envelope is acquired when the viral nucleocapsid buds through the cellular membrane during the viral life cycle. The process of budding takes place only at certain sites where the virus-specific proteins have been inserted into the host membrane. The specific chemical and phospholipid composition of the viral envelope is mostly determined by the cellular membrane that the virus buds from. It was noticed that the acquisition of a lipid-containing membrane is an integral step in the viral morphogenesis especially among some viral groups.

38 Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 2 Naked viruses Enveloped viruses Stable in hostile environment, and can sustain in dry environment and still retain infectivity Not damaged by acid, detergent, and heat Released by lysis of host cells Can infect the GI tract and survive the acid and bile Can spread easily via hands, dust, fomites, etc Neutralizing mucosal and systemic antibodies are needed to control the establishment of infection Labile in dry, and in arid environment (Must stay moist) Damaged by drying, acid, detergent, and heat (Must not infect the GI tract for survival) Pick up new cell membrane during multiplication Insert new virus-specific proteins after assembly Virus is released by budding Must be transmitted in the protective, droplets, secretions, blood and body fluids and both humoral and cell-mediated immunity are needed to control the infection

39 prevent effective neutralization of a virus particle by specific antibodies. Dr. Abdullah A. Hama Microbiology / parasitology & virology Lec. 2 Viral Glycoproteins Among the most important components of the viruses especially among enveloped viruses are glycoproteins. The proteins found in glycoproteins are mainly virally encoded and during progression pathways combine to carbohydrates forming glycoproteins. However, the carbohydrates added to viral proteins often reflect the host cell in which the virus is grown. The importance of viral glycoproteins can be summarized bellow: 1. They attaches the virus particle to a target cell by interacting with a cellular receptor, so they involve in the viral life cycle and infectivity. 2. They are also often involved in the membrane fusion step of infection. 3. The are important viral antigens and involve in viral antigenicity). 4. They are frequently involved in the interaction of the virus particle with neutralizing antibody and may