MICR 201 Microbiology for Health Related Sciences

1. MICR 201 Microbiology for Health Related Sciences Microbiology- a clinical approach by Anthony Strelkauskas et al. 2010 Chapter 14: Parasitic and fungal infections

2. Why is this chapter important? • Over the last five chapters, we have looked at the pathogenicity of bacteria and viruses. In this chapter, we look at the last two groups of infectious organisms, the parasites and the fungi, which are both eukaryotic. • Fungal infections are usually opportunistic, but parasitic infections affect billions of people in the world.

3. Map for chapter 14

4. Parasites

5. Parasitic infections • Parasites can be divided into two groups: • Protozoans– microscopic, single-celled eukaryotes. • Helminths– worms, macroscopic, multicellular eukaryotes with organ systems. • Disease causing parasites depend on their infected host for survival. • Often involve multiple hosts in which specific developmental stages reached • Definitive host – adults develop, sexual reproduction • Intermediate host – asexual reproduction occurs

6. Significance of parasitic infections • Parasitic infections major problem worldwide. • More than 500 million people infected with malaria. • More than 2 million (mostly children) die each year from malaria. • Entamoeba are intestinal parasites that infect 10% of the world population. • Trypanosoma parasites infect 16 million people in Latin America each year.

7. Pathogenesis of parasitic infections • Often the host response contributes to the pathogenesis. • The host defense reaction can cause: • Tissue damage • Allergic or anaphylactic reactions

8. Parasitic protozoans • Parasitic protozoans cause a wide variety of infections. • Affect large number people throughout the world. • Parasitic protozoans vary in size. • Contain membrane-bound nuclei and cytoplasm. • Cytoplasm divided into: • Inner form – endoplasm • Outer form – ectoplasm • Classified on the basis of their methods of movement and reproduction.

9. Protozoans: morphology, classification & physiology

10. Protozoans: morphology, classification & physiology • Most infectious protozoans: • Facultative anaerobes • Heterotrophs • Highly developed reproductive system • Actively dividing form is called trophozoite • Some form cyst • Way of protecting themselves. • Mechanism of transmission from host to host.

11. Sporozoans • Intracellular parasites. • Alternate between sexual and asexual reproduction. • Important diseases: • Malaria • Toxoplasmosis • Together, affect one third of the world population.

12. Malaria • Caused by Plasmodium species • Febrile illness • Found throughout the world • Transmitted by bite of female Anopheles mosquito • Mortality mainly in children and immunocompromised adults.

13. Female Anopheles mosquito transmits malaria

14. Life cycle of Plasmodium Mosquito Human

15. Plasmodium infects hepatocytes and erythocytes

16. Pathogenesis of malaria (1) • Symptoms of malaria include: • Fever (cold and hot periods, in some forms of malaria synchronized) • Anemia, jaundice • Circulatory changes • Anemia is caused by the destruction of red blood cells. • Accompanied by depression of marrow function • Enlarged spleen.

17. Pathogenesis of malaria (2) • Thrombocytopenia is common in malaria. • Bleeding (hemorrhages) • Danger: cerebral malaria in infections with P. falciparum • Abnormal behavior, impairment of consciousness, delusions • Paralysis, seizures • Coma and death

18. Cerebral malaria • Erythrocyte aggregation in small blood vessels • Coagulation disorder • Multiple petechial hemorrhages • Inflammation

19. Malaria relapses • P. ovale and P. vivax can develop into hypnozoites in liver cell • These can go dormant for prolonged times • Can become reactivated and develop into merozoites causing an acute malaria attack.

20. The jaundice often observed in malaria is caused by________. • Erythrocyte aggregation in the brain • Infection of hepatocytes • Liberation of large amounts of hemoglobin when merozoits exit erythrocytes • All of the above. • None of the above.

21. What type of organelle for locomotion do sporozoa use? • Flagella • Pseudopodia • Cilia • Pili • None.

22. Rhizopods: amebas • Most primitive form of protozoans: • Multiply by simple binary fission • Move by using pseudopodia • Produce a chitin wall for protection • Referred to as a cyst • Entamoeba histolytica is an obligate intracellular parasite. • Passed from host to host as cysts: • Fecal-oral route of infection • Ingestion of a single cyst can cause infection • Third highest parasitic cause of deaths worldwide: • Only malaria and schistosomiasis are higher • Amebiasis is on the rise in the US.

23. Pathogenesis of amebiasis • Initial infection is via the fecal-oral route. • Systemic amebiasis occurs only after colon colonized. • Produces several virulence factors and enzymes. • Membrane lesions • Cellular death. • Infection usually mild and asymptomatic. • Lesions can open the intestine for bacterial and viral infection.

24. Flagellates • Four flagellates cause human disease: • Trichomonas, Giardia • Noninvasive • Low morbidity rates • No intermediate host required • Leishmania, Trypanosoma • Invasive • High morbidity rates • Frequently lethal • Intermediate host required • Flagellates widespread in nature. • Use flagella for movement through host. • Multiply by binary fission.

25. Trypanosoma

26. Trypanosomiasis • By the protozoan Trypanosoma. • Motile • Fusiform • Moves in a spiral fashion • Transmitted by vectors: • African form via tse tse fly – causes sleeping sickness (encephalitis) • American form via kissing bug – causes Chagas’ disease (organ megaly) • Chronic infection • Invade endothelial cells in brain (sleeping disease) or organ tissue (Chagas disease) • Escape immune response by changing their change antigens frequently

27. Ciliates • Protozoa that move with cilia • Example : Balantidium coli cause dystentery. Image: Left: Balantidium coli cyst. Right: Balantidium coli trophozoite in a wet mount at 1000x magnification. Credit: PHIL, Oregon Public Health Laboratory.

28. Parasitic helminths • Macroscopic multicellular parasites. • Body covered by a tough acellular cuticle. • Some have suckers, hooks, or plates used for attachment. • Helminths have: • Differentiated organs • Primitive nervous systems • Primitive excretory systems • Highly developed reproductive systems • Do not have a circulatory system.

29. Helminthic infections • Three types of parasitic helminths: • Differentiated based on alimentary tract and reproduction Nematodes (round worm) Cestodes (tape worm) Trematodes (fluke)

30. Nematodes • Roundworms. • Complete intestinal tract. • Diecious (male and female individuals). • Two subgroups: • Intestinal nematodes • Tissue nematodes sharonapbio-taxonomy.wikispaces.com

31. Intestinal nematodes • Several types of intestinal nematodes: • Pinworms (Enterobius vermicularis) Large roundworms (Ascaris lumbricoides) • Characteristics: • Fusiform body shape • Tough outer cuticle • Male and female forms • Thousands offspring produced • Eggs must incubate outside the host to become infective • There is a larval form.

32. Symptoms of intestinal nematode infection • Intestinal nematode infection produce: • Malnutrition • Discomfort • Anemia • Occasionally death • Symptoms depend on number of worms: • Low numbers may be asymptomatic

33. Enterobiusvermicularis • Pinworm, Enterobius vermicularis, ubiquitous parasite of humans. • More than 200 million people infected each year. • Most of infections in children. • Pinworms attach to mucosa of cecum. • Females migrate down to perianal tissue to lay eggs. • Eggs stick to tissue, bedding, towels or fingers. • Eggs can be inhaled or swallowed. • Eggs hatch in the upper intestine. • Larvae migrate down to the cecum

34. Ascarislumbricoides • Largest and most common intestinal nematode. • Adult worms live in small intestine. • Female parasites lay 250,000-500,000 eggs per day. • Eggs passed into feces. • Eggs embryonate in soil for 3 weeks. • Very resistant to environmental pressure. • Viable for up to 6 years.

35. Ascarislumbricoides • Once ingested, eggs produce a larval stage. • Larvae penetrate intestinal mucosa and invade liver. • Exit from hepatic vein, enter the heart, progress to the lung. • Rupture in the alveolar spaces. • Can be coughed up and swallowed. • Symptoms include • Fever, coughing, wheezing, shortness of breath • Worms pass out of the body in a variety of ways: • Vomiting, in stool, crawl out of the anus, nose, mouth, and ears.

36. Ascarislumbricoides

37. Tissue nematodes • Tissue nematodes can induce disease in: • Tissues • Blood • Lymph system • They can live for years in subcutaneous tissues and lymph vessels. • Tissue nematodes can discharge live offspring called microfilariae. • Circulate through the blood or tissue • Can be ingested by blood sucking insects. • Examples include Wucheria and Trichinella

38. Microfilariae can be transmitted by mosquitoes Image: Left: Microfilaria of Wuchereria bancrofti in thick blood smear stained with Giemsa. Center: Photograph of a female Aedes aegypti mosquito as she was in the process of obtaining a "blood meal." Laboratory strains of Aedes aegypti can be infected with Brugia. Credit: DPDx, PHIL

39. Trichinellaspiralis • Lives in the duodenum and jejunum of flesh eating mammals. • Particularly found in swine and bears. • Trichinella larvaeenter through the host vascular system and are distributed widely. • Larvae that penetrate the skeletal muscle survive. • Can become encapsulated in muscle (skeletal, heart) • Can remain viable for 5-10 years. • Some larvae enter the central nervous system and cause encephalitis.

40. Cestodes • Cestodes are commonly called tapeworms. • They are the largest of the intestinal parasites. • They do not have an alimentary tract. • Nutrients are absorbed across the cuticle. • Monoecious (hermaphrodites)

41. Cestodes • The adult body has three sections: • Head – the scolex which may have a rostellum (hooks) and has suckers to adhere to the intestinal wall • Regenerative neck • Segmented body with proglottidesthat contain a hermaphroditic unit

42. Trematodes (flukes) • Have a bilateral symmetry • Have two deep suckers: • One in the oral cavity for food uptake • One on the ventral side of the worm for attachment • Have incomplete alimentary tract (mouth, intestine, but no outlet) • Almost all are monoecious (exception: Schistosoma, these are also round)

43. Trematodes • Trematodescan live for decades in human tissue and blood vessels. • They produce progressive damage to vital organs. • Eggsare excreted from the human host. • They must reach water in order to hatch. • Hatching releases larvae called miracidia. • Miracidiapenetrate snails or fish, the intermediate host. • Miracidia develop into cercariae. • Cercariae are released from the snail or fish. • Cercariaeenter the definitive host and develop into adults that lay eggs • Schistosomacercariae invade skin of humans.

44. Disease causing trematodes • Three major groups of flukes invade humans: • Lung flukes – Paragonimus species • Liver flukes – Clonorchis species • Blood flukes – Schistosoma species

45. Schistosomiasis • Two to three hundred million people are infected worldwide and up to one million people die each year. • There are male and female forms. • Schistosome couples mate in the portal vein. • They stay conjoined for life. • They use suckers to ascend the mesenteric vessels. • They lay eggs in the submucosal veins • 300 to 3000 eggs can be laid per day for as long as 35 years. • Eggs penetrate the veins and enter hollow organs • Intestine • Bladder • Eggs induce inflammation • Bladder cancer can develop

46. Fungi

47. Fungal infections • Mycology is the study of fungi. • Fungi are important for the environment. • Fungi are commensal organisms. • They are normally harmless to humans. • Fungi can be opportunistic pathogens. • Most fungal infections are opportunistic.

48. Fungal structure and growth • Fungi are eukaryotes with cell walls. • The cell wall contains glucan, mannan, and chitin. • The cell membrane contains ergosterol. • Fungi use heterotrophic metabolism. • They obtain carbon from decaying organic matter. • Most are obligate aerobes but some are facultative anaerobes. • No fungi are obligate anaerobes.

49. Fungal structure and growth • There are two forms: • Molds– multicellular, form hyphae, distinct morphology used for diagnostics • Yeasts– unicellular, budding • Fungi reproduce either sexually or asexually. • Asexual reproduction: • Through conidia • Involves mitotic division and budding • Sexual reproduction: • Involves spores - ascospores, zygospores, or basidiospores

50. Molds and hyphae