introduction to microbiology

1. Introduction to
Microbiology
INSHA JAN

2. O Microbiology is the study of living organisms of
microscopic size.
O Medical microbiology is the subdivision concerned
with the causative agents of infectious disease of
man, the response of the host to infection and various
methods of diagnosis, treatment and prevention.
What is Microbiology?

3. Branches of Microbiology

4.  General microbiology: Study of general properties of
microorganisms, such as bacterial morphology,
sterilization and disinfection, culture identification
methods, bacterial genetics, etc.
 Immunology: study of the immune system
 Bacteriology: study of bacteria
 virology: study of viruses
 Mycology: study of fungi
 Parasitology: study of parasites; it has two arms
 Protozoology: study of protozoa ,
 Helminthology: study of helminths.
Branches of Microbiology

5. O Antoine Philips van
Leeuwenhoek (1676)
O First scientist who
observed bacteria and other
microorganisms, using a
single-lens microscope
constructed by him and he
named those small
organisms as' Little
animalcules.
History

6. O Edward Jenner 1796
O Developed the first vaccine of
the world, the smallpox
vaccine. He used the cowpox
virus (Variolae vaccinae) to
immunize children against
smallpox from which the term
‘vaccine' has been derived.
History

7. O Louis Pasteur
O Microbiology developed as a scientific discipline from
the era of Louis Pasteur (1822-1895).He is also
known as father of microbiology.
O Principles of fermentation for preservation of food.
O He introduced the sterilization techniques and
developed steam sterilizer, hot air oven and autoclave.
O He described the method of pasteurization of milk.
History

8. O Contributed for the vaccine
development against several diseases,
such as anthrax, fowl cholera and
rabies.
O Disproved the Theory of spontaneous
generation of disease and postulated
the 'germ theory of disease: He stated
that disease cannot be caused by bad
air or vapor, but it is produced by the
microorganisms present in air
O Liquid media concept: He used
nutrient broth to grow
microorganisms.
History

9. O Joseph Lister (1867)
O Father of antiseptic surgery.
O He had observed that
postoperative infections were
greatly reduced by using
disinfectants such as diluted
carbolic acid during surgery
to sterilize the instruments
and to clean the wounds.
History

10. O Robert Koch
O He introduced solid media
for culture of bacteria,
O He also introduced methods
for isolation of bacteria in
pure culture.
O He described hanging drop
method for testing motility.
O He discovered bacteria such
as the anthrax bacilli,
tubercle bacilli and cholera
bacilli.
History

11. O Paul Ehrlich (1854- 1915)
O Father of chemotherapy.
O Report the acid-fast nature of
tubercle bacillus.
O Developed techniques to stain
tissues and blood cells.
O Proposed a toxin-antitoxin
interaction called Ehrlich
phenomenon and also introduced
methods of standardizing toxin
and antitoxin
History

12. Classification of microorganisms
microorganisms
Prokaryotes Eukaryotes

13. Characteristics Prokaryotes Eukaryotes
Major groups Bacteria ,blue green
algae
Fungi, parasites, plants
animals
Nucleus Diffuse Well defined
Nuclear membrane Absent Present
Nucleolus Absent Present
Ribionucleoprotein Absent present
Cell division Binary fission Mitosis ,meiosis
Chromosome One, circular Many, linear
Extra chromosomal DNA Found in plasmid Found in mitochondria
Cell membrane Does not control sterols Contain sterols
Cellular organelles Absent Present
Site of respiration Mesosome Mitochondria
Ribosome 70S 80S

14. O Shape of bacteria
O Depending on their shape, bacteria are classification
into:
O Cocci (singular coccus, from; kokkos, meaning
berry) - oval or spherical cells
O Bacilli or rods (singular bacillus, meaning rod
shaped).
Morphology of bacteria

15. O Cocci are arranged in groups (clusters), pair or
chains.
O Similarly, bacilli can be arranged in chain, pair, and
some bacilli are curved, comma shaped, or
cuneiform shaped
Morphology of bacteria

16. O Both cocci and bacilli are further classified based on
Gram staining property into
O Gram-positive cocci
O Gram-negative cocci
O Gram-positive bacilli
O Gram- negative bacilli
Morphology of bacteria

17. O Gram stained and hence need special stains for their
demonstration, such as:
O Spirochetes (Trepnonema and Leptospira)-thin
spirally coiled bacilli.
O Mycoplasm as (cell wall deficient free living
bacteria)
O Rickettsiae and chlamydiae are obligate intracellular
bacteria.
Morphology of bacteria

18. Bacteria Examples
Gram positive cocci arranged in
Cluster Staphylococcus
Chain Streptococcus
Pair, lanceolates shaped Pneumococcus
Pair or in short chain, spectacle
shaped
Enterococcus
Octate
Tetrads
Sarcina
Micrococcus

19. Gram negative cocci arranged
in
Pairs, lens shaped Meningococcus
Pairs , kidney shaped Gonococcus
Gram positive bacilli arranged in
Chain (bamboo stick appearance) Bacillus anthracis
Chinese letter or cuneiform pattern Corynebacterium diphtheria
Branched and filamentous form Actinomycosis and nocardia
Palisade pattern Diphtheroids

20. Bacteria Example
Gram negative bacilli arranged in
Pleomorphic Haemophilus , proteus
Thumb print appearance Bordetella pertussis
Comma shaped ( fish in stream
appearance)
Vibrio cholerae
Curved Campylobacter( gull – wing shaped)
and helicobacter
Chain Streptobacillus
Spirally coiled, flexible Spirochetes
Bacteria that lacks cell wall Mycoplasma

21. O Medical mycology is the branch of medical science
that deals with the study of medically important
fungi.
O The name 'fungus' is derived from Greek' mykes'
meaning mushroom (a type of edible fungus).
Mycology

22. O Fungi differ from bacteria and other eukaryotes in many
ways.
O Fungi are eukaryotic and they possess all the eukaryotic
cell organelles such as mitochondria.
O They possess a rigid cell wall, composed of chitin,
glucans and other polysaccharides.
O Fungal cell membrane contains ergosterol instead of
cholesterol.
O Fungi may be unicellular or multicellular.
O They lack chlorophyll and divide by asexual and/or
sexual means by producing spores.
Mycology

23. O Morphological Classification
O 1. Yeast: They grow as round to oval cells.
O that reproduce by an asexual process called budding
in which cells form protuberances which enlarge and
eventually separate from the parent cells.
O Examples include:
O Cryptococcus neoformans (pathogenic)
O Saccharomyces cerevisiae (non-pathogenic)
Classification of fungi

24. O Morphological classification
O Yeast-like: In some yeasts (e.g. Candida), the bud
remains attached to the mother cell, elongates and
undergoes repeated budding to form chains of
elongated cells known as pseudo hyphae.
O They can be differentiated from true hyphae as they
have constrictions at the septa
Classification of fungi

25. O Molds: They grow as long branching filaments of 2-
10 µm width called hyphae.
O Hyphae are either septate (i.e. form transverse
walls) or nonseptate ( there are no transverse walls
and they are multinucleated, i.e. coenocytic)
O Hyphae grow continuously and form a branching
tangled mass of growth called mycelium
Classification of fungi

26. O Based on the growth pattern in culture medium, the
mycelia may be categorized into two types:
O Aerial mycelium: It is the part of the mycelium
which projects above the surface of culture medium.
O Vegetative mycelium: It is the part of the mycelium
that grows on the surface of the culture medium.
O Molds reproduce by formation of different types of
sexual and asexual spores
O Examples of true molds include-Dermatophytes,
Aspergillus, Penicillium, Rhizopus, Mucor, etc.
Classification of fungi

27. O Dimorphic fungi: They exist as molds (hyphal form) in the
environment at ambient temperature (25°C) and as yeasts
in human tissues at body temperature (37°C).
O Several medically important fungi are thermally dimorphic
such as:
 Histoplasma capsulatum
 Blastomyces dermatitidis
 Coccidioides immitis
 Paracoccidioides brasiliensis
 Penicillium marnejfei
 Sporothrix schenckii.
Classification of fungi

28. Classification of fungi

29. O Taxonomical Classification
O Based on the production of sexual spores, the Kingdom
Fungi has been divided into four medically important
phyla. They are as follows:
O Phylum zygomycota: They are lower fungi, produce
sexual spores known as zygospores and possess aseptate
hyphae, e.g. Rhizopus and Mucor.
O Phylum ascomycota: They produce sexual spores known
as ascospores and possess septate hyphae, e.g.
Aspergillus.
Classification of fungi

30. O Phylum basidiomycota: They produce sexual spores
known as basidiospore e.g. Cryptococcus.
O Phylum deuteromycota (Fungi imperfecti): In
majority of the medically important fungi, the sexual
state is either absent or unidentified yet. Hence, they
are traditionally grouped as fungi imperfecti.
Classification of fungi

31. O Medical Parasitology deals with the study of animal
parasites, which infect and produce diseases in
human beings.
Parasitology

32. O All parasites are classified under the following
taxonomic units—the kingdom, subkingdom,
phylum, subphylum, super class, class, subclass,
order, suborder, super family, family, genus and
species.
O The generic name of the parasite always begins
with an initial capital letter and species name with
an initial small letter, e.g., Entamoeba histolytica.
Parasitology

33. O Parasite is a living organism, which lives in or
upon another organism (host) and derives
nutrients directly from it, without giving any
benefit to the host.
Parasite

34. O Parasites may be classified as:
O Ectoparasite: They inhabit the surface of the body of
the host without penetrating into the tissues.
O They are important vectors transmitting the
pathogenic microbes.
O The infection by these parasites is called as
infestation, e.g ., fleas or ticks
O Endoparasite: They live within the body of the host
(e.g., Leishmania). Invasion by the endoparasite is
called as infection.
Parasite

35. O The endoparasites are of following types:
O Obligate parasite: They cannot exist without a parasitic
life in the host (e.g., Plasmodium species)
O Facultative parasite: They can live a parasitic life or free-
living life, when the opportunity arises (e.g.,
Acanthamoeba)
O Accidental parasite: They infect an unusual host (e.g.,
Echinococcus granulosus infect humans accidentally)
O Aberrant parasite or wandering parasite: They infect a host
where they cannot live or develop further (e.g., Toxocara
in humans).
Parasite

36. O Host is defined as an organism, which harbors the
parasite and provides nourishment and shelter.
O Hosts may be of the following types:
O Definitive host: The host in which the adult parasites
replicate sexually (e.g., anopheles species), is called as
definitive host. The definitive hosts may be human or
nonhuman living things
Host

37. O Intermediate host: The host in which the parasite under
goes asexual multiplication is called as intermediate host.
O (e.g., in malaria parasite life cycle, humans are the
intermediate hosts)
O Intermediate hosts are essential for the completion of the
life cycle for some parasites
O Some parasites require two intermediate hosts to complete
their different larval stages.
O These are known as the first and second intermediate
hosts respectively (e.g., Amphibian snails are the first
intermediate host and aquatic plants are the second inter
mediate host for Fasciola hepatica)
Host

38. O Reservoir host: It is a host, which harbours the parasites and
serves as an important source of infection to other susceptible
hosts. (e.g., dog is the reservoir host for cystic
echinococcosis)
O Paratenic host: It is the host, in which the parasite lives but it
cannot develop further and not essential for its life cycle is
known as paratenic host (e.g., fresh water prawn for
Angiostrongylus cantonensis, big suitable fish for
plerocercoid larva of Diphyllobothrium latum and freshwater
fishes for Gnathostoma spinigerum).
O It functions as a transport or carrier host
O Amplifier host: It is the host, in which the parasite lives and
multiplies exponentially.
Host

39. O The relationship between the parasite and the host,
may be divided into the following types:
O Symbiosis: It is the close association between the
host and the parasite.
O Both are interdependent upon each other that one
cannot live without the help of the other.
O None of them suffer any harm from each other
Host parasite relationship

40. O Commensalism: It is an association in which the
parasite only derives the benefit without causing any
injury to the host.
O A commensal is capable of living an independent life
O Parasitism: It is an association in which the parasite
derives benefit from the host and always causes some
injury to the host. The host gets no benefit in return.
Host parasite relationship

41. O It depends upon:
O Source or reservoir of infection
O Mode of transmission.
O Sources of Infection
O Man: Man is the source or reservoir for a majority of
parasitic infections (e.g., amoebiasis, enterobiasis,
etc.) The infection transmitted from one infected man
to another man is called as anthroponoses
Transmission of parasite

42. O Animal: The infection which is transmitted from
infected animals to humans is called as zoonoses.
O The infection can be transmitted to humans either
directly or indirectly via vectors. (e.g., cystic
echinococcosis from dogs and toxoplasmosis from
cats)
O Vectors: Vector is an agent, usually an arthropod that
transmits the infection from one infected human
being to another.
O Vector can be biological or mechanical.
Source of infection

43. O Contaminated soil and water:
O Soil polluted with human excreta containing
eggs of the parasites can act as an important
source of infection, e.g., hookworm, Ascaris
species, Strongyloides species and Trichuris
species. Water contaminated with human
excreta containing cysts of E. histolytica or
Giardia lamblia, can act as source of infection
Source of infection

44. O Raw or under cooked meat: Raw beef containing
the larvae of Cysticercus bovis and pork containing
Cysticercus cellulosae are some of the examples
where undercooked meat acts as source of infection
O Other sources of infection: Fish, crab or aquatic
plants, etc.
Source of infection

45. O The infective stages of various parasites may be
transmitted from one host to another in the following
ways:
O Oral or feco-oral route:
O Penetration of the skin and mucous membranes:
O Sexual contact:
O Bite of vectors:
O Vertical transmission:
O Blood transfusion:
Mode of transmission

46. O The life cycle of the parasite may be direct (simple) or
indirect (complex).
O Direct/simple life cycle: When a parasite requires only one
host to complete its development, it is referred as
direct/simple life cycle
O Indirect/complex life cycle: When a parasite requires two
hosts (one definitive host and another intermediate host) to
complete its development, it is referred as indirect/complex
life cycle .
O Some of the helminths require three hosts (one definitive
host and two intermediate
Life cycle of Parasite

47. Classification of protozoa

48. Classification of helminths