Medical microbiology

MEDICAL MICROBIOLOGY
Sunday, 22 October 2017 1

1. INTRODUCTION TO MEDICAL MICROBIOLOGY
2. HISTORY OF MEDICAL MICROBIOLOGY
3. FIELDS IN MEDICAL MICROBIOLOGY
4. FUNGAL INFECTIOUS DISEASE
5. PARASITIC DISEASE
6. VIRAL INFECTIOUS DISEASE
7. BACTERIAL INFECTIOUS DISEASE
8. DIAGNOSIS IN MEDICAL MICROBIOLOGY AND TREATMENT
Sunday, 22 October 2017 MEDICAL MICROBIOLOGY 2

MEDICAL MICROBIOLOGY
Medical microbiology is a branch of medicine
concerned with the prevention, diagnosis and treatment of
infectious diseases. In addition, this field of science studies
various clinical applications of microbes for the improvement of
health. There are four kinds of microorganisms that cause
infectious disease: bacteria, fungi, parasites and viruses.
Sunday, 22 October 2017 3MEDICAL MICROBIOLOGY

Medical microbiology, also known as ‘’’clinical
microbiology’’’, is the study of microbes, such
as bacteria, viruses, fungi and parasites, which cause a
human illness and their role in the disease.
Medical microbiologist is also involved in teaching at all levels,
and in research. It provided the development of vaccines against
invading organisms.

 Deadly and debilitating diseases such as small pox, polio,
and tuberculosis have been either eradicated or become more
treatable. There are claims that consuming probiotics (bacteria
potentially beneficial to the digestive system)
and/or prebiotics (substances consumed to promote the
growth of probiotic microorganisms) contributes to human
health.
 Microorganisms could be useful in the treatment of cancer.
Strains of non-pathogenic clostridia can infiltrate and replicate
within solid tumours, deliver therapeutic proteins.

HISTORY OF MEDICAL MICROBIOLOGY
 In 1546, Girolamo Fracastoro proposed that epidemic diseases were caused by
transferable seed like entities through direct, indirect contact and contact over
long distances with an infection.
 Louis Pasteur and Robert Koch are the founders of medical microbiology. Louis
Pasteur is famous for his experiments when he disproved the theory of
spontaneous generation. He offered method for food preservation (pasteurization)
and vaccines against anthrax, fowl cholera and rabies.
 Robert Koch contributed to the germ theory of disease, provided that
specific diseases were caused by specific microbes. He developed criteria known
as the Koch's postulates and was among first to isolate bacteria in pure
culture resulting in his description of several bacteria including Mycobacterium
tuberculosis, the causative agent of tuberculosis

medical microbiologist studies the
characteristics of pathogens, their modes of
transmission, mechanisms of infection and
growth.

 medical microbiology primarily focuses on
the presence and growth of microbial
infections in individuals, their effects on
the human body and the methods of
treating those infections.

In 1676, Anton van
Leeuwenhoek obser
ved bacteria and
other
microorganisms,
using a single-
lens microscope of
his own design

Smallpox is a deadly disease caused by the variola virus. It causes painful lesions that leave
disfiguring scars on the skin of people who survive, and can also cause blindness. However,
many infected people do not survive. Smallpox had a fatality rate ranging from 20-60% in
adults and even higher in infants.

In 1796, Jenner decided to test whether you could transmit
cowpox to healthy people on purpose in order to immunize
them against smallpox. He called this
procedure vaccination from the Latin wordvacca, which
means cow. Jenner tested vaccination on an 8-year old boy
and it worked! The boy didn't get smallpox when
experimentally infected with it a couple months late

In 1857 Louis
Pasteur also designed
vaccines against
several diseases such
as anthrax,fowl choler
a and rabies as well
as pasteurization for
food preservation.

1867 Joseph Lister is
considered to be the
father
of antiseptic surgery. By
sterilizing the
instruments with
diluted carbolic
acid and using it to
clean wounds, post-
operative infections
were reduced making
surgery safer for
patients.

Robert Koch contributed to
the germ theory of disease,
provided that
specific diseases were
caused by
specific microbes. He
developed criteria known as
the Koch's postulates and
was among first to isolate
bacteria in pure
culture resulting in his
description of
several bacteria including M
ycobacterium tuberculosis,
the causative agent
of tuberculosis.

Fields in medical microbiology
Microbial physiology is the study of microbial growth,
microbial metabolism and microbial cell structure.
Microbial genetics is the study of how genes are organized and regulated
in microbes in relation to their cellular functions.
Parasitology investigates parasites. The specimen here
is feces, blood, urine, sputum, and other samples.
Virology identifies viruses in specimens of blood, urine, and cerebrospinal fluid.
Immunology/Serology uses antigen-antibody interaction as a diagnostic tool,
determines compatibility of transplanted organs.
A medical microbiologist is a specialist in medical (clinical) microbiology.

Fungal infectious diseases
The diseases that are caused by the pathogenic fungi species
such as candida,histoplasmia etc.fungal infectous diseases
include histoplasmosis and many others.

Transmission of infectious diseases:-
There are various ways in which disease can be
transmitted between individuals. These include
Direct contact - Touching an infected host.
Indirect contact - Touching a contaminated surface
Droplet contact - Coughing or sneezing
Fecal–oral route - Ingesting contaminated food or
water sources

Airborne transmission - Pathogen carrying spores
Vector transmission - An organism that does not
cause disease itself but transmits infection by
conveying pathogens from one host to another
Fomite transmission - An inanimate object or
substance capable of carrying infectious germs or
parasites
Environmental - Nosocomial infections

Histoplasmosis:-
Alternative Names:-
Ohio River Valley fever; Fibrosing mediastinitis
Causes of histoplasmosis:-
Histoplasmosis is an infection caused by a fungus
called Histoplasma.
fungus lives in the environment, particularly in soil that
contains large amounts of bird or bat droppings.
People can get histoplasmosis after breathing in the
microscopic fungal spores from the air,or often after
participating in activities that disturb the soil.

4-The spores are extremely light and float into the air when dirt
or other contaminated material is disturbed.
5- Even if you've had histoplasmosis in the past, you can still get
the infection again.
Symptoms of histoplasmosis:-
•Fever
•cough
•Fatigue (extreme tiredness)
•Chills

Symptoms:-
•Headache
•Chest pain
•Body aches
•histoplasmosis can also produce joint pain
•chronic form of histoplasmosis that can additionally feature weight loss and a cough
that brings up blood.
•long-term (chronic). Symptoms include:
•1- Chest pain and shortness of breath
•2- Cough, possibly coughing up blood
•3- Fever and sweating

Life cycle of histoplasma:-
. When people breathe in the spores, they are at risk for developing
histoplasmosis. After the spores enter the lungs, the person’s body
temperature allows the spores to transform into yeast. The yeast can
then travel to lymph nodes and can spread to other parts of the
body through the bloodstream.

Life cycle of histoplasma:-

Complications of histoplasmosis:-
Histoplasmosis can cause a number of serious complications,
Complications can include:
Acute respiratory distress syndrome (ARDS).Histoplasmosis can
damage lungs to the point that the air sacs begin filling with fluid.
This prevents efficient air exchange and can deplete oxygen levels in
the blood.
Heart problems. Inflammation of the pericardium, the sac that
surrounds your heart, is called pericarditis. When the fluid in this sac
increases, it can interfere with the heart's ability to pump blood
efficiently.

Adrenal insufficiency. Histoplasmosis can harm your adrenal glands,
which produce hormones that give instructions to virtually every
organ and tissue in your body.
Meningitis. In some cases, histoplasmosis can cause meningitis, an
infection and inflammation of the membranes surrounding your
brain and spinal cord.

Exams and test:-
Histoplasmosis is diagnosed by:
Biopsy of the lung, skin, liver, or bone marrow
Blood or other tests to detect histoplasmosis proteins or antibodies
Cultures of the blood, and other things (this test provides the
clearest diagnosis of histoplasmosis, but results can take 6 weeks)

Treatment:-
The main treatment for histoplasmosis is antifungal drugs.
Amphotericin B, itraconazole, and ketoconazole are the usual
treatments.
Antifungals may need to be given through a vein, depending on the
form or stage of disease.
Prevention:-
Histoplasmosis may be prevented by reducing exposure to dust in
chicken coops, bat caves, and other high-risk locations. Wear masks
and other protective equipment if you work in these environments.

-:Histoplasmosis in lungs:-

Definition:
A parasitic disease is an infectious disease caused or transmitted by
a parasite.
 Many parasites do not cause diseases.
 Parasitic diseases can affect practically all living organisms,
including plants and mammals.
The study of parasitic diseases is called parasitology.

Symptoms:
•Abdominal pain.
•Weight loss.
•Increased appetite.
•Sleeping problems.
•Vomiting.
•Fatigue.
•Dehydration.

Cause
Mammals can get parasites from contaminated food or water
andbug bites.
Other risks are walking barefeet, inadequate disposal of faeces and
eating undercooked or exotic food.
Parasites can also be transferred to their host by the bite of an
insect vector, i.e. mosquitos.

E. Histolytica
Geographical distribution :
E. histolytica is more common in tropical and sub-tropical
countries. In India it occasionally takes an epidemic form. It is estimated that about seven to
eleven per cent of the population in India suffers from its infection.

Entamoeba histolytic Parasitic Protozoans
cause Amoebiasis
Infective stage Tetra nucleated cyst
Host Human
Portal of entry Mouth
Mode of reproduction Binary fission
Habitat Colon and caecum
Mode of transmission Ingestion of mature cyst through
contaminated food or water

Life cycle:
 E. histolytica is a monogenetic parasite as its life cycle is completed in a single host i.e.,
man.
 Infection by Entamoeba histolytica occurs by ingestion of mature cysts in fecal
contaminated food, water, or hands.
 Excystation occurs in the small intestine and trophozoites are released, which migrate to the
large intestine.
 The trophozoites multiply by binary fission and produce cysts , which are passed in the
feces.
 Because of the protection conferred by their walls, the cysts can survive days to weeks
in the external environment and are responsible for transmission.

Viral infections
A viral infection occurs when an organism's body is invaded
by pathogenic viruses.
Structural characteristics, such as genome type, virion shape and
replication site, generally have the same features among virus
species within the same family.
There are currently 21 families of viruses known to cause disease in
humans.
Study of viral infection is also known as virology.

Diagnosis & treatment
 Viral disease can be detected by severe muscle and joint pains
before fever and also by skin rash and lymph gland swelling.
 Viruses commonly have self-limited life, so treatment is usually
reduce the symptoms only.
Antipyretic and Analgesic drugs are commonly be used.

1.Measles:
Measles is an infectious disease caused by a measle virus.
It is a single-stranded, negative-sense, enveloped RNA virus of the
genus Morbillivirus within the family Paramyxoviridae.
Virus lives in the mucous of nose and throat of infected person .
 It spreads easily from person to person by coughing and sneezing
into the air.
Infected droplets of mucous can remain active and contagious for
around two hours.
Means ,virus live outside the body.e.g on surfaces and door handles.

Symptoms: Fever &
cough
Runny nose
meningitis
Ichy rash
skin
conjuctivitis

Conjunctivitis (pink
eye)
Measle virus

Treatment:
Measles can be diagnosed by symptoms like,rash and
small spots on body. But,a simple blood or saliva test can
also be diagnosed.
No specific medicine that kills measles virus.
Treatment with vitamin A offered to infected people.

2.Diarrhea
It is caused by Rotavirus among infants and young children.
Name comes from its characteristic wheel-like appearance of
virus when viewed by electron microscopy.
It is a genus of non-enveloped, double-stranded RNA virus in
the family Reoviridae.
Virion shape: icosahedral
Replication site: cytoplasm
It infects & damages the cells of small intestine causes
gastroenteritis.

Rotavirus
20 sided body
65-75nm
Nucleus : 45-50 nm
Shape : wheel like
Life : 7m

Symptoms:
• Vomiting
• Low fever
• dizziness while standing
• decrease in urination
• dry mouth and throat.

Transmission:
Rotavirus infection is highly contagious.
The primary mode of transmission of rotavirus is the passage
of the virus in stool to the mouth of another child. This is known
as a fecal-oral route of transmission.
Virus is stable (remains infective) in the environment,
transmission can occur through ingestion of contaminated water
or food and contact with contaminated surfaces.
Rotavirus can survive for days on hard and dry surfaces, and it
can live for hours on human hands.

Diagnosis & treatment:
Infection can be diagnosed by gastroenteristics as the cause of
severe diarrhoea.
Also by finding in the child’s stool by enzyme immunoassay.
Treatment is non-specific .
involves management of symptoms and, most importantly,
maintenance of hydration.
If untreated, children can die from the resulting severe
dehydration.

ORS (oral rehydration solution) also given to child in which
small amounts of salt and sugar containing extra water, for
treatment depending on severity of diarrhoea.
In some cases, fluids are given by intravenous ( within vein)
drip.

BACTERIAL INFECTIOUS DISEASE

Tuberculosis
Tuberculosis, commonly known as TB, is a bacterial
infection that can spread through the lymph nodes
and bloodstream to any organ in your body.
It is most often found in the lungs.

Symptoms
Although your body may harbor the bacteria that cause
tuberculosis, your immune system usually can prevent you from
becoming sick. For this reason, doctors make a distinction between:
Latent TB. In this condition, you have a TB infection, but the
bacteria remain in your body in an inactive state and cause no
symptoms. Latent TB, also called inactive TB or TB infection, isn't
contagious. It can turn into active TB, so treatment is important for
the person with latent TB and to help control the spread of TB in
general.

An estimated 2 billion people have latent TB.
Active TB. This condition makes you sick and can spread to others. It
can occur in the first few weeks after infection with the TB bacteria, or
it might occur years later.

Signs and symptoms
• Coughing that lasts three or more weeks
• Coughing up blood
• Chest pain, or pain with breathing or coughing
• Unintentional weight loss
• Fatigue
• Fever
• Chills
• Loss of appetite

Causes
Tuberculosis is caused by bacteria that spread from person to
person through microscopic droplets released into the air.
 This can happen when someone with the untreated, active form of
tuberculosis coughs, speaks, sneezes, spits, laughs or sings.

Prevention
Follow these tips to help keep others from getting sick
• Stay home
• Ventilate the room
• Cover your mouth
• Wear a mask

DIAGONOSIS IN MEDICAL
MICROBIOLOGY

Diagnosis types

1-Microbial culture
The primary method used for isolating infectious disease
for study in the laboratory. Tissue or fluid samples are
tested for the presence of a specific pathogen, which is
determined by growth in a selective or differential medium.
Culture is microbial growth on or in a nutritional solid or
liquid medium; increased numbers of organisms simplify
identification.

Types of Culture
Solid culture Liquid culture Cell culture
 Solid state containing
salt and agar.
 Microbial growth is
determined by the
time taken for the
liquid to form a
colloidal suspension.
 Human or animal cell
cultures are infected
with the microbe of
interest.
 Used to culture
bacteria and fungi.
 Used for diagnosing
parasites and detecting
mycobacteria.
 Identifying viruses.

2-Microscopy
Microscopic examination can provide a preliminary, tentative
identification of certain infectious agents by revealing their size,
shape, and cellular structure.
It includes the staining technique for identification of infectious
agent.
Staining includes
a) Gram stain test.
b) Acid fast stain test.
c) Fluorescent stains.

c) Trichrome stain
d)Warthin -Starry stain and Dieterle stain
a)Gram stain test
in which a sample is smeared on a microscopic slide and stained with a special
dye—is used to classify all bacteria as either gram positive (blue staining) or
gram negative (red staining)
b)Acid-fast and moderate (modified) acid-fast stains
used to identify acid-fast organisms (Mycobacterium sp) and moderately
acid-fast organisms (primarily Nocardia sp).

These stains are also useful for staining Rhodococcus and related genera, as well
as oocysts of some parasites (e.g. Cryptosporidium).
c)Fluorescent stains:
These stains allow detection at lower concentrations
Examples
acridine orange (bacteria and fungi)
auramine-rhodamine and auramine O (mycobacteria)
 calcofluor white (fungi, especially dermatophytes)

d) Warthin-Starry stain and Dieterle stain
These silver stains are used to visualize bacteria such as
spirochetes, Helicobacter pylori, microsporidia, and
Bartonella henselae (the cause of cat-scratch disease).

3-Biochemical test
Enzymatic activities are widely used to differentiate bacteria. Even
closely related bacteria can usually be separated into distinct species by
subjecting them to biochemical tests.
Example
Enteric, gram-negative bacteria are a large heterogeneous group of
microbes whose natural habitat is the intestinal tract of humans and
other animals.
All members of the family Enterobacteriaceae are oxidase-negative

Rapid identification method
An unknown enteric bacterium is inoculated into a tube designed
to perform 15 biochemical tests. After incubation, results in each
compartment are recorded.
Each test is assigned a value; the number derived from scoring all
the tests is called the ID value.
Fermentation of glucose is important, and a positive reaction is
valued at 2, compared with the production of acetoin (V-P test,
or the Voges-Proskauer test) which has no value.

Agglutination test
Slide agglutination test, samples of an unknown bacterium are placed in a drop of saline on each of
several slide
Different known antiserum is added to each sample.
The bacteria agglutinate (clump) when mixed with antibodies that were produced in response to that
species or strain of bacterium; a positive test is indicated by the presence of agglutination.

TREATMENT
Some infections can be dealt with by the body’s own immune
system, but more serious infections are treated with antimicrobial
drugs. Bacterial infections are treated with antibacterial (often called
antibiotics) whereas fungal and viral infections are treated with
antifungals and antivirals respectively. A broad class of drugs known
as antiparasitics are used to treat parasitic diseases.

THANK YOU

Medical microbiology

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