microbioloy and past papers

1. MEDICAL MICROBIOLOGY

2. History of microbiology
• Microbiology is the study of microorganisms /
microbes only visible with a microscope.
• The diverse group of organisms includes
algae, archae, bacteria, cyanobacteria, fungi,
protozoa, viruses.
• Most of the microorganisms are harmless,
about 99% of them are good. Eg: Cynobacteria
(blue green algae) 1% are bad. Eg: Pathogens .

3. DISCOVERY ERA:
• “Spontaneous generation” Aristotle (384-322) and
others believed that living organisms could develop
from non-living materials.
• In 13th century, Rogen Bacon described that the
disease caused by a minute “seed” or “germ”.
• Antony Van Leeuwenhoek (1632 – 1723) described
protozoa, basic types of bacteria, yeasts and algae.
He became father of Bacteriology and protozoology
“Animalcules” in 1676.  He invented the first
microscope (50 – 300x), and was the first to
accurately observe and describe microorganisms
• The term microbe was used by Sedillot in 1878.

4. TRANSITION ERA
• Francesco Redi (1626 - 1697) showed that
maggots would not arise from decaying
meat, when it is covered.
• Lazzaro Spallanzai (1729 – 1799)
demonstrated that air carried germs to the
culture medium.
• He showed that boiled broth would not give
rise to microscopicforms of life.

5. GOLDEN ERA
• Louis Pasteur became the father of Medical
Microbiology.
• Pasteur in 1897 suggested that mild heating at
62.8°C (145°F) for 30 minutes rather than
boiling was enough to destroy the undesirable
organisms without ruining the taste of the
product, the process was called Pasteurization.
• He invented the processes of pasteurization,
fermentation and the development of effective
vaccines ( rabies and anthrax).

6. • Pasteur demonstrated diseases of silkworm
was due to a protozoan parasite.
Contributions of Loius pasteur:
– He coined the term “microbiology”, aerobic,
anaerobic.
– He disproved the theory of spontaneous
germination.
– He demonstrated that anthrax was caused by
bacteria and
– He developed a live attenuated vaccine for
anthrax disease

7. • John Tyndall (1820 - 1893) discovered highly
resistant bacterial structure, later known as
endospore.
• Prolonged boiling or intermittent heating was
necessary to kill these spores, to make the
infusion completely sterilized, a process known
as Tyndallisation.
• Lord Joseph Lister (1827-1912) became the
father of antiseptic surgery.
• Lister concluded that wound infections too
were due to microorganisms.

8. • Lister also devised a method to destroy
microorganisms in the operation theatre by
spraying a fine mist of carbolic acid into the
air.
• Robert Koch (1893-1910) demonstrated the
role of bacteria in causing disease.
• He perfected the technique of isolating
bacteria in pure culture.

9. • Robert Koch used gelatin to prepare solid
media but it was not an ideal because :
(i) Since gelatin is a protein, it is digested
by many bacteria capable of producing
a proteolytic exo-enzyme gelatinase
that hydrolyses the protein to amino
acids.
(ii) It melts when the temperature rises
above 25°C.
(iii)Koch's postulates

11. • Fanne Eilshemius Hesse (1850 - 1934) One of
Koch's assistant, first proposed the use of
agar in culture media. It was not attacked by
most bacteria.
• Agar is better than gelatin because of its
higher melting pointing (96°c) and solidifying
(40 – 45°c)points.
• Richard Petri (1887) developed the Petri dish
(plate), a container used for solid culture
media.

12. • Edward Jenner (1749-1823) First to prevent small
pox.
• He discovered the technique of vaccination.
• Alexander Flemming discovered the penicillin
from penicillium notatum that destroys several
pathogenic bacteria.
• Paul Erlich (1920) discovered the treatment of
syphilis by using arsenic
• He Studied toxins and antitoxins in quantitative
terms & laid foundation of biological
standardization.

13. IMPORTANT DISCOVERIES
• Bacteria: Hansen (1874) – Leprosy bacllus
• Neisser (1879) – Gonococcus
• Ogston (1881) – Staphylococcus
• Loeffler (1884) – Diphtheria bacillus
• Roux and Yersin – Diphtheria toxin& Viruses:
• Beijerinck (1898) - Coined the term Virus for
filterable infectious agents.
• Pasteur developed Rabies vaccine.
• GoodPasteur - Cultivation of viruses on chick
embryos.

14. • Charles Chamberland, one of Pasteur’s
associates constructed a porcelain bacterial
filter.
• Twort and d’Herelle - Bacteriophages.
Edward Jenner - Vaccination for Smallpox.
• 

15. MODERN ERA
• Nobel Laureates Years Nobel laureates
Contribution 1901 Von behring - Dipth antitox
• 1902 Ronald Ross - Malaria
• 1905 Robert koch -Tb
• 1908 Metchnikoff - Phagocytosis
• 1945 Flemming - Penicillin
• 1962 Watson Crick - Structur DNA
• 1968 Holley,Khorana - Genetic code
• 1997 Pruisner Prions ,Brenner, Hervitz -Genetic
regulation of organ development &cell death

16. Scope of microbiology
• The importance of microbiology and
microorganisms can not be overemphasized. –
• Microorganisms are necessary for the
production of bread, cheese, beer, antibiotics,
vaccines, vitamins, enzymes, etc. –
• Modern biotechnology rests upon a
microbiological foundation.

17. • Microorganisms are everywhere; almost every
natural surface is colonized by microbes, from
body to ocean.
• Some microorganisms can live hot springs,
and others in frozen sea ice. –
• Most microorganisms are harmless to
humans; You swallow millions of microbes
every day with no ill effects.
• In fact, we are dependent on microbes to help
us digest our food.

18. • Microbes also keep the biosphere running by
carrying out essential functions such as
decomposition of dead animals and plants.
• They make possible the cycles of carbon,
oxygen, nitrogen and sulfur that take place in
terrestrial and aquatic systems. –
• Microorganisms have also harmed humans
and disrupted society over the millennia.

19. • They sometimes cause diseases in man, animals
and plants.
• They are involved in food spoilage. - Infectious
diseases have played major roles in shaping
human history (decline of Roman Empire &
conquest of the New World. –
• The Great Plague reduced population of
western Europe by 25%.

20. • Many microbiologists are primarily interested in
the biology of microorganisms, while others focus
on specific groups;
• Microbiology has an impact on medicine,
agriculture, food science, ecology, genetics,
biochemistry, immunology, and many other fields.
–Virologists - viruses
–Bacteriologists - bacteria
–Phycologists – algae
–Mycologist -fungi

21. • Protozoologists – protozoa
• Medical Microbiology: deals with diseases of
humans and animals; identify and plan
measures to eliminate agents causing
infectious diseases.
• Immunology: study of the immune system
that protects the body from pathogens. -
Agricultural Microbiology: impact of
microorganisms on agriculture; combat plant
diseases that attack important food crops.

22. • Food and Dairy Microbiology:
–prevent microbial spoilage of food &
transmission of food-borne diseases (e.g.
salmonellosis);
– use microorganisms to make food such as
cheeses, yogurts, pickles, beer, etc.
• Industrial Microbiology:
–using microorganisms to make products
such as antibiotics, vaccines, steroids,
alcohols & other solvents, vitamins, amino
acids, enzymes, etc.

23. • Genetic Engineering:
• Engineered microorganisms used to make
hormones, antibiotics, vaccines and other
products. –
• Since viruses are acellular and possess both
living and nonliving characteristics, they are
considered neither prokaryotic nor
eukaryotic.

24. Composition of the Microbial World :
• Procaryotes: relative simple morphology and
lack true membrane delimited nucleus –
• Eucaryotes: morphologically complex with a
true membrane enclosed nucleus
• Organisms divided into 5 Kingdoms:
–Monera – all procaryotes
–Plantae – multicellular
–Animalia - multicellular

25. –Protista – unicellular or colonial eucaryotic
cells lacking true tissues; includes algae,
protozoa & simpler fungi
–Fungi – eucaryoutic; includes molds, yeasts
and mushrooms

28. STRUCTURE OF PARASITES

30. Amoaba cell

31. Giardia lamblia

32. Trypanosome

35. Simplified Schistosoma life cycle.

36. Nomenclature & Taxonomy
• a).Nomenclature of parasites
• Each parasite possesses two names i.e. a
generic and a specific;
• the former begins with an initial capital and
the latter with an initial small letter, after
which comes the designator’s name, followed
by punctuation and finally the year, e.g.
• Ascaris lumbricoides Linnaeus, 1758.

37. • b). Classification of parasites
• The parasites which are of medical impotence
are divided into three main groups:
Phylum Protozoa- single-celled organism,
multiply in human host, Medical Protozoology
Phylum Platyhelminthes & Phylum
Nemathelminthes - multicellular worms, do
not normally multiply in human host.
Phylum Arthropoda – Medical Entomology

38. • Kingdom - Kenya
• Phylum - Police
• Class - Constable
• Order - Overcame
• Family - Foreign
• Genus - General
• species - Service

39. • Classification of Parasitic Helminths:
• Includes: parasitic worms, or helminths, of
human beings belonging to two phyla-
Platyhelminthes (flatworms) and
Nemathelminthes (Round worms).
• Cestode Trematode Nematode

40. Characteristics of Helminthes
• Nematodes
–Adult and larval roundworms are bisexual,
cylindrical worms.
–They inhabit intestinal and extra-intestinal
sites.
• Cestodes
–Adult tapeworms are elongated, segmented,
hermaphroditic flatworms that inhabit the
intestinal lumen.
–Larval forms, which are cystic or solid, inhabit
extra-intestinal tissues.

41. • Flukes (Trematodes)
–Adult flukes are leaf-shaped flatworms.
–Prominent oral and ventral suckers help
maintain position in situ.
–Flukes are hermaphroditic except for blood
flukes, which are bisexual.
–The life-cycle includes a snail intermediate
host.

42. Significance of Parasitology - 1
• Parasitology is the branch of Science which
mainly deals about all the Parasites and
infectious diseases they transmit.
• Intestinal worms, or soil-transmitted
helminths (STH), are the most common
neglected tropical diseases (NTDs) worldwide
(WHO,2014).

43. Significance of Parasitology - 2
• The World Health Organization (WHO,2014)
estimates that over 1.5 billion people are
infected with one or more STHs.
• Globally, there are 700 million people infected
with hookworm (including 44 million pregnant
women), 807 million people infected with
ascariasis, and 604 million people infected with
trichuriasis.
• Transmission mainly occurs in tropical climates
where sanitation and hygiene normally are poor.

44. Significance of Parasitology - 3
• Though the standard method of diagnosing STH
infection is by identifying the parasite eggs in
feces under a microscope, the WHO
recommends periodic deworming of all at-risk
individuals.
• At-risk individuals include pre-school children;
school-age children; women of childbearing age
including pregnant women in their second and
third trimesters, and breastfeeding women; and
adults in certain high-risk occupations.

45. Significance of Parasitology - 4
• Whole Parasitology covers mainly Parasites,
Host and its association between them.
• In order to have a very clear-cut knowledge
about Introduction and Classification of
Parasites some important terms should be
clear and those are:

46. Terms for association of Parasites:
• Host - an organism which harbors the
parasite.
• Commensalisms
• Symbiosis
• Parasitism
• Etc

47. • Terms used in the Cestode
• Strobila: body and trunk of the adult worm
• Scolex: commonly called head that carries the
organs of attachment or suckers
• Neck: the region of growth behind the head
• Proglottid: an individual segment comprising the
complete unit of a tapeworm.
• Cysticercus: it is the resting stage of the larva in
the intermediate host where it develops into a
bladder-worm. Itconsists f a hollow vesicle with
the invaginated scolex on its wall and a central
cavity containing a little fluid.
• Hydatid cyst: the larval stage of the genus
Echinococcus

48. • Parasite:

49. • A living organism which receives nourishment
and shelter from another organism where it
lives is called parasites.
• does not necessarily cause disease.
• parasitism is living in association with the
host.
• derives all benefits from the association and
the host may either not be harmed or may
suffer the consequences of this association, a
parasite disease.
• an organism that is entirely dependent on
another organism, referred to as its host, for
all or part of its life cycle and metabolic
requirements.

50. • Classes of parasites
• Parasite are mainly classified into following
two catagories; along with some other types
of Parasites;
Ecto-parasite (ectozoa): lives outside on the
surface of the body of the host.
• Endo-parasite (entozoa): lives inside the body
of the host: in the blood, tissues, body
cavities, digestive tract and other organs.
• Temporary parasite: visits its host for a short
period.
• Permanent parasite: leads a parasitic life
throughout the whole period of its life.

51. • Facultative parasite: lives a parasitic life when
opportunity arises.
• Obligatory parasite: cannot exist without the
parasitic life.
• Occasional or accidental parasite: attacks an
unusual host.
• Wandering or aberrant parasite: happens to
reach a place where it cannot live.

52. Classes of host:
• Definitive host: - either harbors the adult
stage of the parasite or where the parasite
utilizes the sexual method of reproduction.
In the majority of human parasitic infections,
man is the definitive host; in malaria and
hydatid disease, however, man acts as the
intermediate host.
• Intermediate host: - harbours the larval or
asexual stages of the parasite.
• Paratenic host (a carrier or transport host):
• a host where the parasite remains viable
without further development.

53. • Protozoa
• A) Sacromastigophora
• 1) Mastigophora
• All are tissue flagellates.
• Include the intestinal and genitourinary flagellates and
the blood and tissue flagellates.
• The intestinal and genitourinary flagellates are Giardia,
Trichomonas, Dientamoeba, Chilomastik, etc.
• The blood and tissue flagellates are Trypanosoma,
Leishmania, etc.
• They reproduce asexually by binary fission.

54. • 2) Sarcodina
• Typically amoeboid and include: Entamoeba,
Endolimax, Iodamoeba, Naegleria,
Acanthamoeba, etc.
• Amoebae consist of a shapeless mass of moving
cytoplasm .
• They move by pushing out the ectoplasm to form
pseudopodia (false feet).
• Amoebae reproduce asexually by simply dividing
into two (binary fission)

55. • B) Apicomplexa
• Sporozoa:
The members undergo complex life cycle with
alternating sexual and asexual reproductive
phases involving two different hosts.
• i)Coccidia - are intacellular parasites that
reproduce asexually by a process called
schizogony (merogony) and sexually by
sporogony.
- Class Coccidia includes Isospora and
Toxoplasma
• ii)Haematozoa – the class includes the malarial
parasites-Plasmodium species.

56. • C) Ciliophora - Microspora
• These are the complex protozoa bearing cilia
(short hairs) distributed in rows or patches by
which they move.
• They have two kinds of nuclei (macronucleus
and micronucleus) and a large contractile
vacoule.
• Balantidium coli, a giant intestinal ciliate of
humans and pigs, is the only human parasite

57. Morphology & Habitat of parasites of man-1
• 1)Cestodes:
• These are tape-like, segmented and
hermaphrodite organism.
• They have suckers in their head and in some
species also hooks that attach he tapewor to its
host.. It consists of a head (scolex) and many
proglottids.
• Alimentary canal and body cavity are absent.
Examples are Diphyllobothrium, Taenia,
Echinococcus, Hymenolepsis, etc.

58. Morphology & Habitat of parasites of man-2
• 2)Trematodes:
• They are leaf-like unsegmented organism. Sexes
are not separate except Schistosomes which are
diecious. They don’t have hooks and suckers in
their head.
• Alimentary canal is present but is not complete
(anus absent).
• The body cavity is absent.
• Examples are Schistosoma, Gastrodiscoides,
Fasciolopsis, Fasciola, Clonorchis, Heterophyes,
etc.

59. Morphology & Habitat of parasites of man-3
• 3) Nematodes:
• Have elongated, cylindrical and unsegmented
bodies.
• Sexes are separate (diecious). They also lack
hooks and suckers.
• They possess complete alimentary canal and
body cavity. Examples are:
• 1. Intestinal
• i. In small intestine: Ascaris lumbricoides,
Ancyclostoma duodenale (old world hook worm),
Necator americanus (American hookworm).

60. Morphology & Habitat of parasites of man-4
• ii. In caecum and vermiform appendix:
Enterobius vermicularis (Threadworm or pin
worm), Trichuris trichuria (Whipworm).
• 2. Somatic (inside the tissues and organs)
• i. Lymphatic system: Wuchereria bancrofti,
Brugia malayi
• ii. Subcutaneous tissue: Onchocerca volvulus,
Dracunculus medinensis
• iii. Lungs: Strongyloides stercoralis
• iv. Conjunctiva: Loa loa

61. Life cycle of protozoa & Helminths of man
• a) Protozoa
• multiply vigorously by asexual method for a long
time, and later undergoes encystation for a
change of its host.
• sexual method of reproduction often occurs in a
different host other than the one utilized for
asexual multiplication, as seen in Plasmodia.
• A protozoan parasite may pass its life cycle in one
or two hosts.

62. b)Helminths
Nematode cycle
egg - larvae (L1-L4) -
adult
Cestode cycle
egg - metacestode -
adult
Trematode cycle
egg -miracidium -sporocyst-
redia-cercaria-
(metacercaria)-adult

63. • References:
• Medical microbiology; Kaushal Mishra (2009)
• Classification of Human Parasites, Vectors, and Similar
Organisms. Clinical Infectious Diseases 16:614-615.) by
Lynne S. Garcia (1993).
• Genova Diagnostics; Innovative Testing for Optimal
Health (2008)
• Garcia LS, Bruckner DA. Taxonomy and classification of
human parasites. In: Murray PR, Baron EJ, Pfaller MA,
Tenover FC, Yolken RH, eds. Manual of
• Clinical Microbiology. 7th ed. Washington DC: ASM
Press; 1999; 1330.
• Ending Neglected Tropical Diseases: The End Fund; EIN
number 27-394-1186) © Copyright 2014

64. • World Health Organization: Weekly
epidemiological record, No. 13, 2014; 89: 133–
140 http://www.who.int/intestinal_worms/en/
• Global Atlas of Helminth Infections:
http://www.thiswormyworld.org
• Copyright © 2010-2014 Merck Sharp &
Dohme Corp., a subsidiary of Merck & Co., Inc.,
Whitehouse Station, N.J., U.S.A.