Introduction to Microbiology Lecture _II.ppt

Lecture notes

1. Microbiology
Denis D. Yar Ph.D

2. ENVIRONMENTAL MICROBIOLOGY
Environmental microbiology
This is the study of the composition and physiology
of microbial communities in the environment.
The environment in this case means the soil, water,
air, and sediments covering the planet and can also
include the animals and plants that inhabit these
areas.

3. Environmental microbiology also
involves
:
•Microbial interaction and interaction with
macroorganisims.
•Population biology of microorganisms.
•Microbial communities genetic and evolutionary
processes.
•Element cycles and biogeochemical processes.
•Microbial life in extreme and unusual environment

4. •Microbialhabitats: Microbesare found in just about every
kind of habitat.
•Microbes are incredibly diverse thriving in environments
from the very cold to the extremely hot.
•They are also tolerant of many other conditions such as
limited water availability high salt content and low oxygen
levels.
•Not every microbe can survive in all habitats.
Types of microbial habitats:
Terrestial(soil ) microbial habitats.
Aquatic(water) microbial habitats.
Microbial Habitats in Other Organisms.
air microbial habitat.

5. •SoilMicrobialHabitats
•Only one percent of microbes that live in soil have
been identified.
•These organisms take part in the formation of soil
and are essential components of their ecosystems.
•Bacteria and fungi that live in soil feed mostly on
organic matter such as other plants and animals.
•These microbes are very sensitive to their local
environment.
•Factors such as the levels of carbon dioxide and
oxygen the pH moisture and temperature all affect
the growth of microbes in the soil.

6. WaterMicrobialHabitat
•Microbes live in both fresh and salt water.
•These organisms include microscopic plants
and animals as well as bacteria fungi and
viruses.
•As with other microbes the ones that live in
water are adapted to the specific conditions of
their environment.
•Habitats range from ocean water with an
extremely high salt content to freshwater lakes
or rivers

7. MicrobialHabitatsinOtherOrganisms.
•Microbes also live on other organisms.
•As with the ones found on people these microbes can
be harmful or beneficial to the host.
•Example: Bacteria grow in nodules on the roots of pea
and bean plants.
•These microbes convert nitrogen from the air into a
form that the plants can use.
•In many ways animals and plants have evolved as
habitats for the millions of microbes that call them
home.

8. WATER AS MICROBIAL HABITAT
Waterisessentialtolife,butmanypeopledonothave
accesstocleanandsafedrinkingwaterandmanydieof
waterbornebacterialinfections.

9. Microbiological Water Analysis
•The most important bacterial gastrointestinal diseases
transmitted through water are cholera, salmonellosis and
shigellosis. These diseases are mainly transmitted through
water (and food) contaminated with feacesof patients.
•Drinking water can be contaminated with these pathogenic
bacteria, and this is an issue of great concern. However, the
presence of pathogenic bacteria in water is sporadic and
erratic, levels are low, and the isolation and culture of
these bacteria is not straight-forward.
•For these reasons, routine water microbiological analysis
does not include the detection of pathogenic bacteria.
However, safe water demands that water is free from
pathogenic bacteria.

10. Coliforms
•Coliformsare a broad class of bacteria found in our environment,
including the feaces of man and other warm-blooded animals
•The presence of coliformbacteria in drinking water may indicate a
possible presence of harmful, disease-causing organisms.
•Theyaredefinedasrod-shapedGram-negativenon-sporeformingand
motileornon-motilebacteriawhichcanfermentlactosewiththe
productionofacidandgaswhenincubatedat35–37°C.
•Coliformscanbefoundintheaquaticenvironment,insoilandon
vegetation;Whilecoliformsthemselvesarenotnormallycausesof
seriousillness,theyareeasytoculture,andtheirpresenceisusedto
indicatethatotherpathogenicorganismsoffeacaloriginmaybe
present.

11. A good bacterial indicator of fecal pollution should fulfill the
following criteria:
•(1) exist in high numbers in the human intestine and feaces
•(2) not be pathogenic to humans
•(3) easily, reliably and cheaply detectable in environmental
waters.
•(4) does not multiply outside the enteric environment
•(5) in environmental waters, the indicator should exist in
greater numbers than eventual pathogenic bacteria
•

12. Bacteria Disease/ infection Symptoms
Aeromonas Enteritis Very thin, blood-and
mucus-containing diarrhea
Campylobacter jejuniCampilobacteriose
Flue, diarrhea, head-and
stomachaches, fever, cramps
and nausea
Escherichia coli Urinary tract infections,
neonatal meningitis,
intestinal disease
Watery diarrhea, headaches,
fever, homiletic uremia, kidney
damage
Plesiomonas
shigelloides
Plesiomonas-infection
Nausea, stomachaches and
watery diarrhea, sometimes
fevers, headaches and vomiting
Typhus Typhoid fever
Fevers
Salmonella
Salmonellosis
Sickness, intestinal cramps,
vomiting, diarrhea and
sometimes light fevers
Streptococcus (Gastro) intestinal
disease
Stomach aches, diarrhea and
fevers, sometimes vomiting
Vibrio Cholera
Heavy diarrhea
Bacteria Found In Surface Water

13. Microorganisms Disease Symptoms
Amoeba Amoebic
dysentery
Severe diarrhea, headache,
abdominal pain, chills, fever; if not
treated can cause liver abscess,
bowel perforation and death
Cryptosporidi
um parvum
Cryptosporidiosis Feeling of sickness, watery diarrhea,
vomiting, lack of appetite
Giardia Giardiasis Diarrhea, abdominal cramps,
flatulence, belching, fatigue
Toxoplasm
gondii
Toxoplasmosis Flu, swelling of lymph glands
With pregnant women subtle abortion
and brain infections
Protozoa Found in Surface Water

14. Viral Sources of Waterborne Disease
Hepatitis A:inflammation and
necrosis of liver
Norwalk-type virus:acute
gastroenteritis
Rotaviruses:acute
gastroenteritis, especially in
children
Enteroviruses:many types
affect intestines and upper
respiratory tract
Reoviruses:infects intestines
and upper respiratory tract

15. SoilMicroorganismsAndTheirFunctions
BACTERIA
•Theyaredecomposers,eatingdeadplant
materialandorganisms'waste.
•Doyouknowwhatsoilsmellslike?

16. •Wellactinomycetes,auniquetypeof
bacteria,causethatsmell,anditisagoodsign
ofhealthysoil.
•Actually,peoplehavebeensmellingsoilfor
many,manyyearsasawaytojudgeiftheland
isgoodforplanting
•[Nitrogen-fixingbacteriaformsymbiotic
associationswiththerootsoflegumeslike
cloverandlupine,andtreessuchasalderand
locust.

17. FUNGI
Fungi are organisms. They are not plants, nor
are they animals. They group themselves into
strings called hyphae. The hyphae then form
groups called mycelium.
They are helpful but could also be harmful to
soil organisms.
Fungi are helpful because they have the ability
to break down nutrients that other organisms
cannot.

18. Fungi can attach themselves to plant roots.
This is a good relationship called mycorriza.
The fungi help the plant by giving it those
needed nutrients, and the fungi get food from
the plant, the same food that plants give to
humans.
On the other hand, fungi can get food by being
parasites, attaching themselves to plants or
other organisms, but for selfish reasons.

19. PROTOZOA
Areorganismsthathaveonlyonecell,andare
microscopic,butlargerthanbacteria.
Theyaregroupedbythewaystheymove:
amoebauseapsuedo(fake)foot,ciliateshave
cilia(shorthair)andmovethemveryfast,and
flagellateshaveoneormoreflagella(whips)
andmovethemveryfast.

20. Protozoaeatbacteriawhichactuallyhelpskeep
thebacteriapopulationgrowing.
Protozoahelpothersoilorganismsandplantsby
releasingausableformofnitrogenintothesoil.
Theyreleasetheexcessnitrogenintheformof
ammonium(NH4+).
Thisusuallyoccursneartherootsystemofa
plant.
Anotherrolethatprotozoaplayisinregulating
bacteriapopulations.
Predatorynematodesmayregulatepopulationsof
bacterial-andfungal-feedingnematodes,thus
preventingover-grazingbythosegroups.

21. MICROBIOLOGY OFAIR
•Ofallenvironments,airisthesimplestoneanditoccursinasingle
phasegas.
•Variouslayerscanberecognizedintheatmosphereuptoaheightof
about1000km.
•Thelayernearesttotheearthiscalledastroposphere.
•Thistroposphereischaracterizedbyaheavyloadofmicroorganisms.
•Theatmosphereasahabitatischaracterizedbyhighlightintensities,
extremetemperaturevariations,lowamountoforganicmatteranda
scarcityofavailablewatermakingitanonhospitableenvironmentfor
microorganismsandgenerallyunsuitablehabitatfortheirgrowth.
•Nevertheless,substantialnumbersofmicrobesarefoundinthelower
regionsoftheatmosphere.
•ThestudyofthesemicrobesinairiscalledasAeroMicrobiology.

22. Disease caused by air borne microbes:
BacterialDiseases
•Brucellosis:
Brucellasuisitismainlyanoccupationaldisease
amongveterinarian,butcherandslaughterhouseworkers.
•PulmonaryAnthrax:
Bacillusanthracisisthecausativeagent.Transmission
ismainlybyinhalingthedustcontaminatedbyanimal
products.
•DiseasesCausedbyStreptococcusPyogenes:
AnumberofdiseasesarecausedbyStreptococcus
pyogeneswhichismainly transmittedthroughair.
DiseasesCausedbyStreptococcuspyogenesoccurinthe
throat,skin,andsystemically.
•RheumaticFever:Thisisupperrespiratorytract
infectionbyS.pyogenesCharacterizedbyinflammation
anddegenerationofheartvalves.
·

23. •StreptococcalPneumonia:
Itisofmajoroccurrenceamongthebacterialpneumonia.Causativeagent
is
Streptococcuspneumonia
•Meningitis:
Haemophilusinfluenzaecausesmeningitisinchildrenbetween6weeks
and2yearsofage.
•Diptheria:
Diphtheriaismainlycontractedbychildren.Infectionofthetonsils,throat
andnoseandgeneralizedtoxemiaarethesymptoms.Thecausative
agentis
Corynebacteriumdiphtheria
•Tuberculosis:
Pulmonarytuberculosisisasevererespiratorydisease.Lossofappetite,
fatigue,weightloss,nightsweatsandpersistentcougharesomeofthe
symptoms.CausativeagentisMycobacteriumtuberculosis
•Legionellosis:
Itisatypeofbranchopneumonia.Legionellapneumophilaisthecausative
agent.Itoccursinnaturalwater.Attimesitentersandproliferatesin
coolingtower,aircoolerandshowerbath.Sprayingandsplashingof
watercontainingpathogenmayproduceaerosolswhicharedisseminated
inair.

24. AirBorneFungalDiseases:
Itconsistsofmanytypes.Theyarefollowing
•Cryptococcosis:
Leadstomildpneumonitis.CausativeagentistheyeastCryptococcus
neoformans.Itisasoilsaprophyte.Infectionisacquiredbyinhalationofsoil
particlescontainingthecausativeagent.
•Blastomycosis:
Formationofsuppurativeandgranulomatouslesionsinanypartofthebody.
Blastomycesdermatitisisthecausativeagent.Itisasoilbornefungusand
henceinhalationofsoilparticlescontainingthefungusproducestheinfection.
•Coccidiodomycosis:
Infectionmaynotbeapparentbutinseverecasesitisfatal.Usuallyinfection
leadstoself-limitedinfluenzafeverknownasvalleyfeverordesertrheumatism.
Causativeagentofthediseaseisasoilfungus,Coccidioidesimmitis.Inhalationof
dustcontainingarthrosporesofthefungusleadstoinfection.
•Aspergillosis:
Itisanopportunisticdiseaseofhuman.CausativeagentisAspergillus
fumigatus.Infectionoccursthroughinhalationofspores.

25. AirBorneViralDiseases:
Airborneviraldiseasesareofdifferenttypes.Theyarefollowing,
•CommonCold:
Itisthemostfrequentofallhumaninfections.Characteristicsymptomincludes
runningnoses.Rhinovirusisthecausativeagent.Dropletswithnoseandthroat
dischargesfrominfectedpersonsarethesource.
•Influenza:
Symptomsofinfluenzaarenasaldischarge,headache,musclepains,sorethroat
andgeneralweakness.Causativeagentsareorthomyxovirus.
•Measles:
Measlesisthemostcommoncommunicablehumandiseasemainlyaffecting
children.Symptomsarefever,cough,andcoldandred,blotchyskinrash.
Causativevirusismorbillivirus.Sourceofinfectionisrespiratorytractsecretionsin
theformofdroplets.
•Mumps:
Itisacommunicablediseaseandisacommonchildhooddisease.Itis
characterizedbypainfulswellingofparotidglandsandsalivaryglands.Droplets
containinginfectedsalivaarethemainsource.
•AdenoViralDiseases:
Adenovirusescauseacuteself-limitingrespiratoryandeyeinfections.
Adenovirusesaretransmittedbyairbornemode.Diseasesincludeacutefebrile
pharyngitis,acuterespiratorydiseaseandadenoviruspneumonia.

26. SOURCESOFMICROORGANISM INAIR:
•Quiteanumberofsourceshavebeenstudiedinthisconnectionand
almostallofthemhavebeenfoundtoberesponsiblefortheairmicro
flora.
•Oneofthemostcommonsourcesofairmicrofloraisthesoil.
•Soilmicroorganismswhendisturbedbythewindblow,liberatedintothe
airandremainsuspendedthereforalongperiodoftime.
•Manmadeactionslikediggingorploughingthesoilmayalsorelease
soilbornemicrobesintotheair.
•Similarlymicroorganismsfoundinwatermayalsobereleasedintothe
airintheformofwaterdropletsoraerosols.
•Splashingofwaterbywindactionortidalactionmayalsoproduce
dropletsoraerosols.
•Aircurrentsmaybringthemicroorganismsfromplantoranimalsurfaces
intoair.
•Themicroorganismsaredischargedoutinthreedifferentformswhich
aregroupedonthebasisoftheirrelativesizeandmoisturecontent.
•Theyaredroplets,dropletnucleiandinfectiousdust.
•ItwasWells,whodescribedtheformationofdropletnuclei.
•Thisinitiatedthestudiesonthesignificanceofairbornetransmission.

27. Droplet:
•Droplets are usually formed by sneezing, coughing or talking. Each
consists of saliva and mucus.
•Droplets may also contain hundreds of microorganisms which may be
pathogenic if discharged from diseased persons.
•Pathogens will be mostly of respiratory tract origin.
•The size of the droplet determines the time period during which they
can remain suspended.
•Most droplets are relatively large, and they tend to settle rapidly in
still air.
•When inhaled these droplets are trapped on the moist surfaces of the
respiratory tract.
•Thus, the droplets containing pathogenic microorganisms may be a
source of infectious disease.

28. •Droplet Nuclei:
Small droplets in a warm, dry atmosphere tend to evaporate rapidly and
become droplet nuclei.
Thus, the residue of solid material left after drying up of a droplet is known
as droplet nuclei.
These are small, 1-4µm, and light. They can remain suspended in air for
hours or days, traveling long distances.
They may serve as a continuing source of infection if the bacteria remain
viable when dry.
Viability is determined by a set of complex factors including, the atmospheric
conditions like humidity, sunlight and temperature, the size of the particles
bearing the organisms, and the degree of susceptibility or resistance of the
particular microbial species to the new physical environment.
If inhaled droplet nuclei tend to escape the mechanical traps of the upper
respiratory tract and enter the lungs.
Thus, droplet nuclei may act as more potential agents of infectious diseases
than droplets.
Small droplets in a warm, dry atmosphere are dry before they reach the floor
and thus quickly become droplet nuclei.

29. InfectiousDust:
Largeaerosoldropletssettleoutrapidlyfromairontovarious
surfacesandgetdried.
Nasalandthroatdischargesfromapatientcanalsocontaminate
surfacesandbecomedry.
Disturbanceofthisdriedmaterialbybedmaking,handlinga
handkerchiefhavingdriedsecretionsorsweepingfloorsinthe
patient'sroomcangeneratedustparticleswhichadd
microorganismstothecirculatingair.
Mostdustparticlesladenwithmicroorganismsarerelativelylarge
andtendtosettlerapidly.
Dropletsexpelledduringcoughing,sneezing,e.t.cconsistofsaliva
andmucus,andeachofthemmaycontainthousandsof
microorganisms.
Occursinawarm,dryclimate,andbeforetheyreachthefloor
quicklybecomedropletnuclei.
Thesearesmallandlight,andmayfloataboutforarelativelylong
period..

30. Prokaryote Characteristics
•0.2 to 2.0 μm in diameter and 2 to 8 μm in
length
•Shapes: coccus, bacillus, spiral

31. Arrangements of Cocci
Diplococci(remain in pairs)
Streptococci (remain in chain)
Tetra(divide in 2 planes,
remain in groups of four)
Sarcinae(divide in 3 planes,
remain in cube)
Staphylococci (divide in
multiple planes, remain in
grapelike clusters)

32. Arrangement of Bacilli
•Diplobacilli: appear in pairs
•Streptobacilli: appear in chains
•Coccobacilli: oval, look like cocci
•Palisades: picket fence

33. Arrangement of Spirilium
Vibrios: curved rods
Spirilla: helical shape, rigid bodies
Spirochetes: helical and fexible

34. External Structures
GLYCOCALYX (sugar coat):
•sticky, gelatinous polymer outside the
cell wall
•Composed of polysaccharide,
polypeptide or both
•If attached to cell wall, considered a
capsule
•If unorganized and loosely attached,
considered a slime layer
•Contributes to bacterial virulence
•Important component of biofims
•Help attach to various surfaces, protects,
facilitates communication
(Extracellular polymeric substance
EPS)
Cyanobacterium
Capsule in olive green

35. •Thick peptidoglycan
•Teichoic acids
Gram-positive
Cell Wall
Figure 4.13b–c
Thin peptidoglycan
Outer membrane
Periplasmic space
Gram-Negattive
Cell Wall

36. Mycoplasmaspecies:
•-smallest bacteria
•-no cell wall (Resistant to Penicillin
•-have sterols in membrane (resist osmotic
lysis)
•Many antimicrobial drugs target bacterial
cell walls
•Penicillin: prevents peptide crosslinking,
prevents formation of functional wall in
growing cells

37. Gram Positive Bacteria

38. Classification of Bacteria
•Gram -Spirochete Gram + bacilli

39. Gram Negative Bacteria

40. Miscellaneous/ Poor staining
Species

42. Bacterial Diversity:
Chlamydias
•Chlamydias
*All are intracellular parasites of animals
*Obtain ATP from host cells
*Some sexually transmitted diseases (C.
trachomatis)

43. Bacterial Diversity:
Spirochetes
•Spring-shaped
*Live on their own or in hosts
*Some are pathogens

44. Archaean Physiology
•Halophiles(salt lovers), extreme
thermophiles,andmethanogens(methane
makers)

45. Classification of Bacteria
Survey of Clinically Relevant Bacteria

46. 1 Gram Negative Spiral Bacteria
•Slender and flexible, come
in a lot of different shapes
•More rigid than
spirochetes
•Ex. –Campylobacter jejuni
Symptom –tenesmus: the
sensation of desire to
defecate, which is common
and occurs frequently , with
out the production of
significant amounts of feces
(often small amounts of
mucous or blood are alone
passed).

47. 2 Gram Negative Spirochetes
•pathogenic
•very flexible
•tightly coiled, helically coiled
•Example
*syphilis
Treponema pallidum

48. Gram Negative Spirochetes
•Most of pathogenic
•Very flexible
•Tightly coiled, helically
coiled
•Example
*Lyme disease
Borrelia burgdorferi
(organism gets lodged in
tissues)

49. 3 Gram Negative Aerobic Rods
*Legionella pneumophila
•Lower respiratory tract
infection
•Needs oxygen

50. Gram Negative Aerobic Rods
Bordetella pertussis–
whooping cough
•Needs oxygen

51. Gram Negative Aerobic Rods
•Pseudomonas
aeruginosa
(pigmented)
•Needs moisture
•Common in
hospitals
•Opportunistic
pathogen –causes
UTI, skin, and lung
infection

52. 4. Gram Negative Facultative
Rods
Vibrio
*V. cholerae
•Most well known of group
•Very severe dysentery. Can lose
10-15 liters of water/day. Leads
to hypovolemia –low water, hardly
any water in body
*V. vulnificus
•Very pathogenic
•Can cause flesh eating disease,
if it gets in a wound
*V. parahaemolyticus
•Found in shellfish –oysters
•Halophile –loves salt (will find in oceans, estuaries)
•Self limiting

53. Gram Negative Facultative Rods
•Enteric
*Salmonella
*Shigella
*E. coli (0157H7)

54. 5 Gram Negative Anaerobic Rods
•Fusobacterium
*Live in between teeth
and gums
*Cause tooth abscesses
and periodontal disease
*Teeth have nothing to
anchor –bone is
destroyed
•

55. 6. Gram Negative Cocci or Coccobaccilli (plump
rods)
Neisseria gonorrhoeae
–
Usually a diplococcus
Sexually Transmitted
Disease
very antibiotic resistant

56. Gram Negative Cocci or Coccobaccilli (plump
rods)
•Neisseria meningitidis
very infectious and
communicable.

57. Gram Negative Cocci or Coccobaccilli (plump
rods)
Acinetobacter baumanni iv.
lwoffi
opportunistic, UTI, skin,
and upper respiratory

58. 7 Chlamydia Gram Negative Rods (Transitional)
•Very short little rods
•Gram negative
•Transitional –doesn’t hold stain
well
•Do not have the ability to
synthesize own ATP, therefore and
obligate intracellular parasite of
other animals (humans)
•Can go asymptomatic for a long
time
•Ex.
*C. trachomatis–STD, causes
eye infection
*C. psittaci–parrot (associated
with birds)

59. 8 Rickettsia Gram Negative Rod (Transitional)
•Small gram negative rods
•Transitional –doesn’t hold
stain well
•Can’t synthesize it’s own
NAD, coenzyme A, therefore
an obligate intracellular
parasite
•Causative agent of Rocky
Mountain Spotted Fever
•Example
*R. Prowazekii

60. 9 Mycoplasma Gram Positive (Transitional )
•Gram positive –only because
they take in dye in cell
membrane but it washes away
•Transitional –doesn’t hold stain
well.
•Have no cell wall
•Can not treat with penicillin
•Ex.
*Mycoplasma pneumoniae–causes
LRTI
*Ureaplasma urealyticum–causes
UTI
*Both imbed themselves in the
tissue. The most cell damage is
done by the immune system
destroying the tissue.

61. 10 Gram Positive Cocci
Staphyloccocus aureus
MRSA
These bacteria can break
down all tissues of body.

62. Gram Positive Cocci
Streptococcus pyogenes–
no antibiotic resistance
right now
These bacteria can break
down all tissues of body.

63. 11 Gram positive Endospore Forming Rods
•Difficult to get rid of
because of endospores
•Example
*Clostridium tetani

64. Gram positive Endospore Forming Rods
•Difficult to get rid of
because of endospores
•Example
•C. perfringens–
gangrene

65. Gram positive Endospore Forming Rods
•Difficult to get rid of
because of endospores
•Common in hospitals
•Example
•C. difficile
antibiotic associated
pseudmembraneous
enterocolitis

66. Introduction to Parasitology
(Protozoa & Helminths)

67. 67
Why study Parasitology?
•Many of these parasites are causative agents of major
public health problems of the world.
•Recent estimates of prevalence of parasites in the world
are:
Ascaris 1.5 billion
Hookworms 1.3 billion
Whipworms 1 billion
Filarial worms 657 million
Malaria 500 million
Schistosomes 270 million
Amebiasis 50 million
Taenia tapeworms 50 million
Clonorchis 20 million
Chagas’ Disease 15 million
•These parasites cause untold suffering and death in the
world today.

68. 68

69. 69

70. 70

71. 71
Key definitions: What is ….?
•Medical parasitology:“the study and medical
implications of parasites that infect humans”
•A parasite:“a living organism that acquires some of
its basic nutritional requirements through its intimate
contact with another living organism”. Parasites may
be simple unicellular protozoa or complex
multicellular metazoa
•Eukaryote:a cell with a well-defined chromosome in
a membrane-bound nucleus. All parasitic organisms
are eukaryotes

72. 72
Key definitions: What is ….?
•Protozoa: unicellular organisms, e.g.
Plasmodium (malaria)
•Metazoa:multicellular organisms, e.g.
helminths (worms) and arthropods (ticks,
lice)
•An endoparasite:“a parasite that lives
within another living organism” –e.g.
malaria, Giardia
•An ectoparasite:“a parasite that lives on
the external surface of another living
organism” –e.g. lice, ticks

73. 73
Key definitions: What is ….?
•Host:“the organism in, or on, which the parasite lives and
causes harm”
•Definitive host:“the organism in which the adult or sexually
mature stage of the parasite lives”
•Intermediate host:“the organism in which the parasite lives
during a period of its development only”
•Zoonosis:“a parasitic disease in which an animal is normally
the host -but which also infects man”
•Vector:“a living carrier (e.g.an arthropod) that transports a
pathogenic organism from an infected to a non-infected host”. A
typical example is the femaleAnophelesmosquito that transmits
malaria

74. 74
Examples of important intestinal protozoa
Transmitted by the faecal-oral route and cause
diarrhoea
•Giardia lamblia: world-wide distribution,
lives in the small intestine and results in
malabsorption
•Entamoeba histolytica: may invade the colon
and cause bloody diarrhoea –amoebic
dysentery. Also causes ameobic liver abscess.
•Cryptosporidium parvum: more prevalent in
the immunocompromised
•Cyclospora cyatenensis -parasitises the small
intestinal mucosa and may cause diarrhoea for
several weeks
•Balantidium coli: alarge motile ciliated
parasite that lives in the colon of pigs, humans
and rodents and can lead to colonic ulceration
•Enterocytozoon bienusi: a microsporidian that
parasitises the small intestine. Also more
common in the immunocompromised.

75. 75
Examples of important systemic protozoa
Detected in the blood
•Plasmodium: the cause of malaria. There
are 4 species that infect man: P.
falciparum, P. vivax, P. ovale and P.
malariae
•Toxoplasma gondi: transmitted by the
ingestion of oocysts from cat faeces.
Infection can lead to ocular problems and is
also a cause of neonatal toxoplasmosis
•Leishmania: transmitted by sand flies, can
lead to visceral, cutaneous and
mucocutaneous leishmaniasis
•Trypanosoma: haemoflagellates which
cause
*In Africa -sleeping sickness
(transmitted by the Tsetse fly)
*In South America -Chagas
disease (transmitted by the
Reduviid bug)
Typical lesion of cutaneousleishmaniasis
Tsetse fly –the vector of African
trypanosomiasisIt has a painful bite!

76. 76
Examples of important metazoa–
intestinal nematodes
•Trichuris(whipworm)
*A soil transmitted helminth
*prevalent in warm, humid conditions
*Can cause diarrhoea, rectal prolapse and
anaemia in heavily-infected people
•Ancylostomaand Necator
(hookworms)
*A major cause of anaemia in the tropics
•Strongyloides
*inhabits the small bowel
*infection more severe in
immunospressed people (e.g.
HIV/AIDS, malnutrition, intercurrent
disease)
•Enterobius(pinworm or
threadworm)
*prevalent in cold and temperate climates
but rare in the tropics
*found mainly in children
•Ascaris(roundworm)
*Found world-wide in conditions of poor
hygiene, transmitted by the faecal-oral
route
*Adult worms lives in the small intestine
*Causes eosinophilia
Heavy intestinal infections may occur with Ascaris. Adult
worms can be several cmslong.

77. 77
Examples of important metazoa–
systemic nematodes
•Filaria including:
•Onchocerca volvulus–
Transmitted by the
simulium black fly, this
microfilarial parasite can
cause visual impairment,
blindness and severe
itching of the skin in those
infected
•Wuchereria bancrofti–The
major causative agent of
lymphatic filariasis
•Brugia malayi–Another
microfilarial parasite that
causes lymphatic filariasis
•Toxocara
*A world-wide infection
of dogs and cats
*Human infection
occurs when
embryonated eggs are
ingested from dog or
cat faeces
*It is common in
children and can cause
visceral larva migrans
(VLM)

78. 78
Examples of important flatworms -
cestodes
Intestinal -(“tapeworms”)
•Taenia saginata
*worldwide
*acquired by ingestion of
contaminated, uncooked beef
*a common infection but causes
minimal symptoms
•Taenia solium
*worldwide
*acquired by ingestion of
contaminated, uncooked pork
that contains cystercerci
*Less common, but causes
cystercicosis –a systemic
disease where cysticerci encyst
in muscles and in the brain –
may lead to epilepsy
Systemic
•Echinococcus granulosus (dog
tapeworm) and Echinicoccus
multilocularis(rodent tapeworm)
*Hydatid disease occurs when
the larval stages of these
organisms are ingested
*The larvae may develop in the
human host and cause space-
occupying lesions in several
organs, e.g. liver, brain

79. 79
Examples of important metazoa–trematodes
(flukes)
Intestinal
•Fasciolopsis buski -A common
parasite of humans and pigs in
South-east Asia. This parasite is one
of the largest trematodes to infect
man (8cm in length) and lives in the
upper intestine. Chronic infection
leads to inflammation, ulceration and
haemorrhage of the small intestine
•Fasciola hepatica(liver fluke)-Primarily, a
parasite of sheep, humans become infected
when they ingest metacercariae that have
encysted on watercress. The adult trematode
lives in the intra-hepatic bile ducts of the
liver. “Fascioliasis” can lead to severe
anaemia in humans
•Clonorchis sinensis(liver fluke)-Widespread
in China, Japan, Korea and Taiwan, this
parasite is acquired by ingestion of infective
metacercariae in raw or pickled fish
•Paragonimus westermani( lung fluke)-
Widespread in the Far East and South east
Asia, the parasite is acquired by ingestion of
infective metacercariae in raw or pickled
crustaceans
•Schistosoma haematobium, S. mansoni and S.
japonicum –see below

80. 80
Schistosomiasis (bilharzia)

81. 81
Laboratory Diagnosis of Parasitic
Infections
•Purpose –
*Confirmation of clinical suspicion
*Identification of unsuspected infection
•Methods same as used in Bacteriology &
Virology but significance of different
methods varies.
•Isolation least important, morphological
identification very important.
•Serology relatively less important

82. 82
Morphological identification
•Examination of faeces –
*Gross
*Microscopy
•Saline mount
•Iodine Mount
•Thick smears –not commonly used
•Permanent stained smears
–Iron hematoxylene
–Whearley’s trichrome stain
*Concentration methods
•Floatation techniques
•Sedimentation techniques

83. 83
Morphological identification
•Examination of Blood
*Thin Smear
*Thick smear
*Wet mount for microfilaria
*Stains used

84. 84
Cultivation of parasites
•Culture methods –
*Amoeba
*Leishmania & Trypanosoma
*Malarial parasite
•Animal inoculation –Not practical
•Xenodiagnosis –Vectors infected
experimentally
•Immunological diagnosis

85. 85
Immunological diagnosis
•Serology –All tests
available
*IHA
*ELISA
*CIEP
*IF
*CFT
•More useful in
*Amoebiasis
*Leishmaniasis
*Malaria
*Toxoplasmosis
*Trichinosis
*Filariasis
*Echinococcosis
•Skin Tests –Specificity
low, cross reactions
common
*Casoni’s test
*Leishmanin test

86. 86
Sources of information
•The Special Programme for Research and Training
in Tropical Diseases (TDR UNICEF, UNDP, World
Bank, WHO) website:
ww.who.int/tdr/media/image.html
•University of South Carolina School of Medicine:
http://pathmicro.med.sc.edu/book/parasit-sta.htm
•Lecture notes on Tropical Medicine, Dion R Bell,
Fourth edition, 1996, Blackwell Science.
•Parasites and human disease, W. Crewe and D.R.W.
Haddock, 1985, First edition, Edward Arnold