Fungi, Protozoa, and Helminthes

1
Fungi, Protozoa, and Helminthes
2
Fungi
3
Kingdom Fungi

• Divided into 2 groups
• macroscopic fungi (mushrooms, puffballs, gill
  fungi)
• microscopic fungi (molds, yeasts)
• Majority are unicellular or colonial

4
Fungal Organization

• Mold
• Hyphae
• Mycelium
• Yeast
• Soft, uniform texture and appearance
• Thermal dimorphism
• grow as molds at 30C and as yeasts at 37C

5
(No Transcript)
6
Fungal Organization - Mold

• Fungal Cell Structure
• Cell walls contain chitin
• Energy reserve is glycogen
• Nonmotile
• Produce wind-blown spores
• Grow toward food source
• Conidia / spores

7
Fungal Organization

• Yeasts
• Unicellular (bicellular)
• False hyphae
• Beta-glycan cell wall structure

8
Fungal Nutrition

• All are heterotrophic
• Majority harmless saprobes
• Some are parasites
• Live on the tissues of other organisms, but none
  are obligate

9
Fungal Reproduction

• Primarily through spores formed on reproductive
  hyphae
• Asexual reproduction spores are formed through
• Budding or mitosis
• Sporangiospores
• Conidia
• Arthrospore
• Chlamydospore
• Blastospore
• Phialospore
• Microconidium or macroconidium
• porospore

10
(No Transcript)
11
(No Transcript)
12
Reproductive strategies

• Sexual reproduction
• Spores are formed following fusion of male and
  female strains and formation of sexual structure
• Sexual spores and spore-forming structures are
  one basis for classification
• Zygospores
• Ascospores
• Basidiospores

13
Zygospores
14
Ascospores
15
Basidiospores
16
Yeast

• Budding
• cloning
• Sometimes form pseudohypha

17
Fungal Classification

• Yeast verse Mold
• Asexual verse Sexual (reproductive strategies)
• Terrestrial or water

18
Fungal Classification

• Subkingdom Amastigomycota
• Terrestrial inhabitants including those of
  medical importance
• Zygomycota zygospores sporangiospores and some
  conidia
• Ascomycota ascospores conidia
• Basidiomycota basidiospores conidia
• Deuteromycota majority are yeasts and molds
  no sexual spores known conidia

19
Fungal Classification

• Subkingdom Mastigomycota

20
Diagnosis and identification require

• macroscopic and microscopic observation of
• asexual spore-forming structures and spores
• hyphal type
• colony texture and pigmentation
• physiological characteristics
• genetic makeup
• culturing in selective and enriched
• media
• Reverse important!!!!

21
Roles of Fungi

• Adverse impact
• mycoses, allergies, toxin production
• destruction of crops and food storages
• Beneficial impact
• decomposers of dead plants and animals
• sources of antibiotics, alcohol, organic acids,
  vitamins
• used in making foods and in genetic studies

22
Characterization of Fungal Infections

• Systemic
• Subcutaneous
• Cutaneous
• Superficial
• Opportunistic

23
Systemic fungal infections by true pathogens
24
Histoplasma capsulatum

• Histoplasmosis
• typically dimorphic
• distributed worldwide
• most prevalent in eastern central regions of US
• grow in moist soil high in nitrogen content
• inhaled conidia produce primary pulmonary
  infection
• may progress to systemic involvement of a variety
  of organs chronic lung disease
• amphotericin B, ketoconazole

25
Coccidioides immitis

• Coccidioidomycosis
• distinctive morphology
• blocklike arthroconidia in the free-living stage
• arthrospores inhaled from dust
• Creates spherules and nodules in the lungs
• lives in alkaline soils in semiarid, hot climates
  
• endemic to southwestern US
• amphotericin B treatment

26
(No Transcript)
27
Blastomyces dermatitidis

• Blastomycosis
• dimorphic
• free-living species distributed in soil
• midwestern and southeastern US
• inhaled 10-100 conidia convert to yeasts
  multiply in lungs
• symptoms include cough, chest pains and fever
• chronic cutaneous, bone, nervous system
  complications
• amphotericin B

28
Blastomyces dermatitidis
29
Paracoccidioides brasiliensis

• Paracoccidioidomycosis
• distributed in Central South America
• lung infection occurs through inhalation or
  inoculation of spores
• systemic disease not common
• ketoconazole, amphotericin B, sulfa drugs

30
Subcutaneous Mycoses
31
Sporothrix schenckii

• Sporotrichosis (rose-gardeners disease)
• dimorphic
• very common saprobic fungus that decomposes plant
  matter in soil
• infects appendages and lungs
• Lymphocutaneous variety
• occurs when contaminated plant matter penetrates
  the skin
• pathogen forms a nodule
• spreads to nearby lymph nodes
• Potassium iodide orally
• Amphotericin B in unresponsive cases

32
Lymphocutaneous Sporotrichosis
33
Mycetoma

• when soil microbes are accidentally implanted
  into the skin
• progressive, tumorlike disease of the hand or
  foot due to chronic fungal infection
• may lead to loss of body part
• caused by Pseudallescheria or Madurella

34
Cutaneous Mycoses
35
Cutaneous Mycoses

• Dermatophytoses
• infections strictly confined to keratinized
  epidermis (skin, hair, nails)
• ringworm tinea
• 39 species in the genera Trichophyton,
  Microsporum, Epidermophyton
• communicable among humans, animals, soil
• infection facilitated by moist, chafed skin

36
Examples of dermatophyte spores. (a) Regular,
numerous microconidia of Trichophyton. (b)
Macroconidia of Microsporum canis, a cause of
ringworm in cats, dogs, and humans. (c)
Smooth- surfaced macroconidia in
clusters characteristic of Epidermophyton.
37
Dermatophytoses

• Ringworm of scalp
• tinea capitis
• affects scalp hair-bearing regions of head
• hair may be lost
• Ringworm of body
• tinea corporis
• occurs as inflamed, red ring lesions anywhere on
  smooth skin
• Ringworm of groin
• tinea cruris
• jock itch
• affects groin scrotal regions
• Ringworm or foot hand
• tinea pedis tinea manuum
• spread by exposure to public surfaces occurs
  between digits on soles
• Ringworm of nails
• tinea unguium
• persistent colonization of the nails of the hands
  feet that distorts the nail bed

38
Ringworm Treatment

• Topicals
• ointments containing tolnaftate, miconazole or
  menthol camphor
• lamisil or griscofulvin 1-2 years

39
Superficial Mycoses
40
Superficial Mycoses

• Tinea versicolor causes mild scaling, mottling of
  skin
• Malassezia furfur
• White piedra is whitish or colored masses on the
  long hairs of the body
• Trichosporan beigelli
• Black piedra causes dark, hard concretions on
  scalp hairs
• Piedraia hortae

41
Hortaea werneckii

• Tinea nigra
• Dematiaceous yeast-like hyphomycete found in
  tropical and subtropical areas
• Extremely halophilic environments
• Slow growing

42
Opportunistic Pathogens
43
Candida albicans

• Candidiasis
• widespread yeast
• infections can be short-lived, superficial skin
  irritations to overwhelming, fatal systemic
  diseases
• budding cells of varying size may form both
  elongate pseudohyphae true hyphae
• forms off-white, pasty colony with a yeasty odor

44
Candida albicans

• Normal flora of oral cavity, genitalia, large
  intestine or skin
• 20 of humans
• Account for 80 of nosocomial fungal infections
• Account for 30 of deaths from nosocomial
  infections

45
Candida albicans

• Thrush
• occurs as a thick, white, adherent growth
• mucous membranes of mouth throat
• Vulvovaginal yeast infection
• painful inflammatory condition of the female
  genital region
• causes ulceration whitish discharge
• Cutaneous candidiasis
• occurs in chronically moist areas of skin and
  burn patients

46
(No Transcript)
47
Cryptococcus neoformans

• Crypotcoccosis
• widespread encapsulated yeast
• inhabits soils around pigeon roosts
• common infection of AIDS, cancer or diabetes
  patients

48
Cryptococcus neoformans

• infection of lungs leads to cough, fever, and
  lung nodules
• dissemination to meninges and brain
• causes severe neurological disturbance
• death

49
Pneumocystis (carinii) jiroveci

• causes pneumonia (PCP)
• most prominent opportunistic infection in AIDS
  patients
• forms secretions in the lungs that block
  breathing
• can be rapidly fatal if not controlled with
  medication
• small, unicellular fungus

50
Aspergillus

• Aspergillosis
• very common airborne soil fungus
• 600 species
• 8 involved in human disease
• inhalation of spores causes fungus balls in lungs
  and invasive disease in the eyes, heart, brain
• amphotericin B nystatin

51
(No Transcript)
52
Zygomycosis

• Zygomycota are extremely abundant saprobic fungi
• found in soil, water, organic debris, food
• Genera most often involved are Rhizopus, Absidia,
  Mucor
• usually harmless air contaminants
• invade the membranes of the nose, eyes, heart,
  brain of people with diabetes, malnutrition with
  severe consequences

53
Mycotoxicoses

• Fungal toxins lead to mycotoxicoses
• usually caused by eating poisonous or
  hallucinogenic mushrooms
• aflatoxin toxic and carcinogenic
• grains, corn peanuts
• lethal to poultry and livestock
• Stachybotrys chartarum
• sick building syndrome
• severe hematologic and neurological damage

54
Parasites
55
Parasitology

• Study of eucaryotic parasites, protozoa and
  helminths
• Cause 20 of all infectious diseases
• Less prevalent in industrialized countries
• Increasingly common in AIDS patients

56
(No Transcript)
57
Kingdom Protista

• Algae
• Protozoa

58
Protozoa

• 100,000 species
• _at_ 25 are important pathogens
• Vary in shape, lack a cell wall
• Most are unicellular
• Colonies are rare
• Most are harmless, free-living in a moist habitat
• Some are animal parasites
• Spread by insect vectors
• All are heterotrophic
• Feed by engulfing other microbes and organic
  matter

59
Protozoa

• Most have locomotor structures
• flagella, cilia, or pseudopods.
• Exist as trophozoite
• motile feeding stage
• cyst
• Dormant resting stage when conditions are
  unfavorable for growth and feeding
• All reproduce asexually, mitosis or multiple
  fission
• Many also reproduce sexually

60
Protozoan Classification

• Difficult because of diversity
• Simple grouping is based on method of motility,
  reproduction, and life cycle

61
Protozoan Classification

• Mastigophora
• primarily flagellar motility
• sexual reproduction
• cyst and trophozoite

62
Protozoan Classification

• Sarcodina
• primarily ameba
• asexual by fission
• most are free-living

63
Protozoan Classification

• Ciliophora
• Cilia
• trophozoites and cysts
• most are free-living, harmless

64
Protozoan Classification

• Apicomplexa
• motility is absent except male gametes
• sexual and asexual reproduction
• complex life cycle all parasitic

65
Protozoan Classification

• Phyla grouping based on method of motility,
  reproduction, and life cycle

66
Hemoflagellates Vector-Borne Blood Parasites

• Obligate parasites that live in blood and tissues
  of human host
• Spread in specific tropical regions by
  blood-sucking insects that serve as intermediate
  hosts
• Categorized according to cellular and infective
  stages

67
Protozoal Diseases
68
An Intestinal Ciliate Balantidium coli

• An occupant of the intestines of domestic animals
  such as pigs and cattle
• Acquired by ingesting cyst-containing food or
  water
• Trophozoite erodes intestine and elicits
  intestinal symptoms
• Healthy humans resistant
• Rarely penetrates intestine or enters blood
• Treatment tetracycline, iodoquinol,
  nitrimidazine or metronidazole

69
(No Transcript)
70
Leishmania species

• Leishmaniasis
• Endemic to equatorial regions
• Promastigotes are injected with sand fly bite
• convert to amastigote and multiply
• if macrophage is fixed the infection is localized
• systemic if macrophage migrates
• L. major

71
Entamoeba histolytica

• Amebiasis
• Alternates between a large trophozoite
• Motile by means of pseudopods and a smaller
  nonmotile cyst
• Humans are the primary hosts
• Ingested
• Carried by 10 of world population

72
(No Transcript)
73
Entamoeba histolytica

• Cysts swallowed and travel to small intestine
• alkaline pH and digestive juices stimulate cysts
  to release 4 trophozoites
• Trophozoites attach, multiply, actively move
  about and feed
• Asymptomatic in 90 of patients
• Ameba may secrete enzymes that dissolve tissues
  and penetrate deeper layers of the mucosa
• Causing dysentery, abdominal pain, fever,
  diarrhea and weight loss

74
Entamoeba histolytica

• Life-threatening manifestations are
• Hemorrhage
• Perforation
• Appendicitis
• Amebomas
• Tumor-like growths
• May invade liver and lung
• Severe forms of disease result in 10 fatality
  rate
• Effective drugs are iodoquinol, metronidazole,
  and chloroquine

75
Giardia lamblia

• Giardiasis
• Pathogenic flagellate
• Cysts are small, compact, and multinucleate
• Reservoirs include beavers, cattle, coyotes,
  cats, and humans
• Cysts can survive for two months in environment
• Usually ingested with water and food
• 10 to 100 cysts

76
Giardia lamblia

• Cysts enter duodenum, germinate, travel to
  jejunum to feed and multiply
• Diagnosis difficult because organism is shed in
  feces intermittently
• Treatment quinacrine or metronidazole
• Agent is killed by boiling and iodine

77
Trichomonads Trichomonas species

• Small, pear-shaped
• 4 anterior flagella and an undulating membrane
• Exist only in trophozoite form
• 3 infect humans
• T. vaginalis
• T. tenax
• T. hominis

78
Trichomonas vaginalis

• Causes an STD called trichomoniasis
• Reservoir is human urogenital tract
• Strict parasite
• 3 million cases yearly
• Female symptoms
• foul-smelling, green-to-yellow discharge
  vulvitis cervicitis urinary frequency and pain
• Male symptoms
• urethritis, thin, milky discharge, occasionally
  prostate infection
• Metronidazole
• Ping-pong effect!

79
Protozoal Diseases of the Blood and Nervous System

• The Plasmodium Parasite Infects the Blood
• Malaria affects 300-500 million people
• Four species of Plasmodium cause malaria
• P. vivax
• P. ovale
• P. malariae
• P. falciparum

80
Plasmodium

• Malaria
• Dominant protozoan disease
• Obligate intracellular sporozoan
• Female Anopheles mosquito is the primary vector
• blood transfusions, mother to fetus
• 2 million deaths each year

81
Plasmodium

• Africans with sickle-cell anemia gene
• Resistant!!!

82
Trypanosoma species and Trypanosomiasis

• Distinguished by their infective stage
• trypomastigote
• elongate, spindle-shaped cell with tapered ends,
  eel-like motility
• 2 types of trypanosomiasis
• T. brucei
• African sleeping sickness
• T. cruzi
• Chagas disease

83
Trypanosoma brucei

• African Sleeping Sickness
• Spread by tsetse flies
• Biting of fly inoculates skin with
  trypomastigotes
• Multiplies in blood and damages spleen, lymph
  nodes and brain
• Harbored by reservoir mammals
• Two variants of disease caused by 2 subspecies
• T.b.gambiense Gambian strain West Africa
• T.b. rhodesiense Rhodesian strain East Africa

84
Trypanosoma brucei

• Chronic disease symptoms are sleep disturbances,
  tremors, paralysis and coma.
• Blood, spinal fluid or lymph nodes
• Treatment before neurological involvement with
  melarsoprol, eflornithine
• Control involves eliminating tsetse fly

85
Trypanosoma cruzi

• Chagas disease
• Endemic to Central and South America
• Reduviid bug (kissing bug) is the vector
• Bug feces is inoculated into a cutaneous portal
• Local lesion, fever, and swelling of lymph nodes,
  spleen, and liver
• Heart muscle and large intestine harbor masses of
  amastigotes
• Chronic inflammation occurs in the organs
  (especially heart and brain)
• Treatment nifurtimox and benzonidazole

86
Toxoplasma gondii

• Toxoplasmosis
• Intracelllular apicomplexan parasite with
  extensive distribution
• Lives naturally in cats
• harbor oocysts in the GI tract
• Acquired by ingesting raw meats or substances
  contaminated by cat feces
• Most cases go unnoticed
• Except in fetus and AIDS patients
• Can suffer brain and heart damage
• Treatment pyrimethamine and sulfadiazine

87
Parasitic Helminths
88
Parasitic Helminths

• Multicellular animals
• Parasitize host tissues
• Organs for reproduction, digestion, movement,
  protection
• Mouthparts
• Attachment
• Digestion of host tissues
• Well-developed sex organs that produce eggs and
  sperm
• Fertilized eggs go through larval period in or
  out of host body

89
Helminths

• Flatworms (Phylum Platyhelminthes)
• do not have respiratory or circulatory
  structures, or a digestive tract
• Cestodes (tapeworms)
• Trematodes or flukes
• Roundworms (Phylum Nematoda)

90
Flatworms

• Cestodes have a head region called a scolex
• Fertilized eggs are produced in proglottids which
  break off and spread eggs
• Tapeworms generally live in hosts intestine,
  absorbing nutrients
• They have limited host range, but usually at
  least 2 hosts

91
Flatworms

• Trematodes have complex life cycles and often 2
  hosts
• Eggs develop into larvae (miracidia) in water,
  which invade snails
• Trematodes evade the immune system by having a
  surface similar to host cells

92

• Roundworms (Phylum Nematoda)
• Damage to the host often occurs by large worms
  burdens in vessels or intestines

93

• Tapeworms
• Beef and pork tapeworm disease are caused by
  Taenia saginata and T. solium, respectively
• acquired by eating poorly cooked beef or pork
• scolex attached to the intestine, causing
  obstruction and mild diarrhea

94
Humans Host to at Least 50 Roundworm Diseases

• Pinworm disease is caused by Enterobius
  vermicularis
• Infection of the intestines leads to diarrhea and
  anal itching
• Reinfection can occur if contaminated hands
  contact food or the mouth
• Worms die in a few weeks, even without treatment

95
Trichinellosis

• caused by Trichinella spiralis
• T. spiralis lives in pig intestines and can
  encyst in skeletal muscles
• Transmission to humans occurs by eating raw or
  poorly cooked pork
• Symptoms include
• pain
• vomiting
• nausea
• constipation
• Larvae can migrate to the tongue, eyes, and ribs

96
Hookworms

• have a set of hooks or suckers to attach to the
  upper intestine
• Hookworms suck blood from intestinal capillaries
• This cause blood loss and anemia
• Humans are the only host
• Larvae in soil penetrate the skin of bare feet
  and enter the bloodstream