This book opens the world of microbes and parasites around us, so that
we are able to treat the diseases caused by them. This is the only book
which comprises of both microbiology and parasitology under one bind.
Dr. Amit Arora, BHMS from Nehru Homoeopathic Medical College and
Hospital, New Delhi. He is presently working as a Senior Medical Officer
in Dpt. of AYUSH, GNCT of Delhi. He is also been teaching in Dr. B.R.
Sur Homoeopathic Medical College Hospital and Research Centre,
Bacterial, Viral and Parasitic diseases play a considerable role in causing diseases and immunology
helps us in understanding that how the body reacts to these foreign agents affecting on it. This book is
a compilation of Immunology, bacteriology, virology, parasitology and mycology. I have tried to make
this book simple in reading for the students so that they could easily understand the concepts. To make
the learning easier, well labelled diagrams and tables have been furnished at appropriate places. Newly
emerging virus, ebola virus has been included in the book. At the end of the book, frequently asked
questions from various BHMS, nursing and MBBS exams have been included.
I have tried to make the book complete in its whole extent but I do not claim any perfection. Suggestions and new ideas for further improvement of this book shall always be appreciated.
The book is divided in into different sections:
1. Immunology: In this section I have tried to explain every aspect of immunology in a simple manner
which is easy to understand. This section covers the defence mechanism of body, various agents
that affect the body and cause diseases, various reactions that take place between affecting agents
and immune system of body and immunological tests that help us to diagnose the bacterial, viral
and parasitic diseases.
2. Bacteriology and virology: This part covers the general features of bacteria and viruses, how they
can be grown in laboratories. There the chapters on specific bacteria and virus, their culture methods,
lab investigations, diseases caused by them and their treatment.
3. Parasitology: This section covers the various parasites, how they enter and grow in body and cause
diseases, lab investigations to diagnose and their treatment.
4. Mycology: This section consists of various fungi that cause infections in humans.
Microbiology: The study of micro-organisms is known as microbiology.
Micro-organisms: These are small living forms of life which can only be seen by a microscope.
Most micro-organisms are single celled and hence called as unicellular.
There are numerous microorganisms present around us in our environment. They are invisibly playing
a great role in our day to day life. Microbiology unlocks that invisible world around us and tells us about
their role in our day to day life.
1. Lucretius, a Roman philosopher (98-55 B.C.), Varo and Columella (first century BC) believed that
invisible creatures were responsible for diseases called "animalia minuta".
2. Girolamo Fracastoro, a physician (1478-1553), proposed that living germs are responsible for
3. Kircher (1659) found minute worms in the blood of plague patient.
4. Antony van Leeuwenhoek (1632-1723) is considered as the "Father of bacteriology and
i. He designed a single lens microscope and made various observations through his microscope.
ii. With his microscope, in 1674, he viewed rain and pond water, scrapings from his teeth and made
first observation of microorganisms and was the first person to observe, accurately describe and
measure bacteria and protozoa. He termed them as "animalcules" which he thought were tiny
iii. In 1677, he became the first person to describe spermatozoa.
iv. He was one of the earliest to describe red blood corpuscles.
5. In 1546, an Italian scientist Girolamo Fracastoro proposed that "contagion is an infection that passes
from one thing to another". He recognized three forms of passage, namely contact, lifeless objects,
6. Robert Hooke, an English scientist was the first person to describe micro-organisms. The study of
micro-organisms, or microbiology began when Robert Hooke in 1665 viewed many small objects
and structures using a simple lens that magnified approximately 30 times. His specimens included
the eye of a fly, a bee stinger, and the shell of a protozoan. He also examined thin slices of cork,
which was the bark of a particular type of oak tree. He found that cork was made of tiny boxes that
he referred to as ‘cells’. He published his work in a book Micrographie. In 1678, he developed the
7. Carolus Linnaeus (1707-1778), developed taxonomic system for naming plants and animals,
grouped similar organisms together. He grouped Lecuwenhoek’s micro-organisms into six categories:
Fungi, Protozoa, Algae, Bacteria, Archaea, small multicellular animals. His book, Systema naturae,
was first published in 1735.
Theory of Spontaneous generation
This theory proposed that life could originate from non-living or decomposing matter.
1. This theory was proved by:
i. Aristotle (384-322 BC) — proposed that animals sometimes arise in soil, sometimes in plant or
sometimes in other animals. This theory of specific origin is known as spontaneous generation.
This theory states that simple invertebrates could arise by spontaneous generation.
ii. John Needham (1713-1781) — in 1748 boiled mutton broth, then sealed and still observed
growth after a period of time.
2. This theory was disproved by:
i. Francesco Redi (1626-1697) ~ in 1670, he demonstrated that maggots are unable to grow on
meat if meat was covered with gauze. He suggested that flies land on pieces of exposed meat
and lay their eggs, which then hatch to maggots.
ii. Italian scientist Abbe Lazzaro Spallanzani (1 729-99) criticized Needham’s work. In 1767, he
boiled meat and vegetable broths for a long period of time and then sealed the necks of the glass.
As control experiments, he left some flasks opened, and boiled some briefly, as Needham had
done. After two days, he found that the control flasks were swarming with organisms, but the
sealed flasks had no organisms. Needham countered that Spallanzani had destroyed the "vital
force" of life with excessive amounts of heat.
Following demonstrated that micro-organisms cause disease
I. Agostino Bassi (1835) showed that a muscardine disease of silkworm was caused by a fungus.
2. Oliver Wendell Holmes (1840) and Ignaz Semmelweis (1846) had concluded that puerperal sepsis
was transmitted by contaminated hands of nurses, medical students and this could be prevented by
washing hands with antiseptic solution.
3. Edward Jenner (1749-1823):
i. In 1798, he used a vaccination procedure to protect individuals from smallpox. Jenner discovered
that a less pathogenic agent could give protection against a more pathogenic one. He accidently
came to know that milk maids who suffered from cowpox were immune to smallpox.
ii. The modern era of vaccines and vaccination, thus began in 1798 with Edward Jenner’s use of
cowpox as a vaccine against smallpox.
4. John Snow, a British physician, traced the source of cholera to the municipal water supply of London
during an 1854 outbreak. So, he stated that by avoiding the contaminated water source, people could
avoid the disease. He drew attention to the fact that a poison or unseen object in the environment
was responsible for the disease, but the proof was still lacking.
The classical golden age of microbiology (1854-1914)
During this period, numerous branches of microbiology were laid for the maturing process that has led
to modern microbiology.
1. Louis Pasteur (1822-1895) is known as "father of microbiology". Role of Louis Pasteur:
i. Developed methods and techniques of bacteriology.
ii. He used various forms of nutrient media to grow micro-organisms and thus showed that one
media may be suitable for one organism but not for other.
iii. First to report the role of micro-organisms in fermentation.
iv. Clarified the role of yeasts in fermentation of fruits and grains resulting in the production of
alcohol. He also found that bacteria were responsible for spoilage of wine.
v. In 1860-61, disproved the spontaneous generation doctrine by his Swan-Neck Flask experiment.
vi. Proposed germ theory of disease, which states that microorganisms are the causative agents of
vii. Discovered the existence of life in the absence of free oxygen (anaerobic growth) in 1857.
viii. Showed that mild heating could be used to kill microorganisms in broth, so developed a process
of destroying bacteria known as pasteurization.
ix. Introduced sterilization techniques and development of steam sterilizer, autoclave and hot air
oven. For sterlisation of fluids, he advocated heating to 120°C under pressure and for glass
items, dry heat at 170°C.
x. Suggested methods to control pebrine disease in silkworm.
xi. Isolated the causative agent of chicken cholera (1880), anthrax (1877) and rabies.
xii. Introduced attenuate live vaccine for prophylactic use. He developed chicken cholera, anti rabies
and anthrax vaccines. He coined the term "vaccine"
xiii. In 1880, first cultured staphylococci in liquid media and produced abscesses by inoculating the
bacteria into rabbits.
**Contents and Sample Pages**
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