|
AIDS
Antibiotic
Antibiotic
susceptibility
testing
Bacterium
Cancer
In
vitro diagnostics
Molecular
diagnostics
DNA
DNA chips
Epizootic
Food safety
Gene
Gene therapy
Generation
time
Health
Hepatitis
Hygiene
Infectious
disease
Influenza
Microbes
Molecular
biology
Reservoir
SARS
STD
Transmission
Viral load
Virus
WHO
Zoonosis
|
A
AIDS
AIDS is a viral disease caused by HIV (human immunodeficiency
virus). This virus belongs to the retrovirus family and particularly
infects certain immune system cells giving rise to the clinical
signs of AIDS observed. |
Antibiotic
An antibiotic is a substance which is either produced by microorganisms
(bacterium, yeast-streptomyces) or synthetically (chemical molecule)
which is capable of stopping bacterial proliferation. Antibiotics
have no effect on viruses. They are classified into antibiotic
categories according to their composition, mode of action or
their antibacterial spectrum. An antibiotic is selected with
accurate knowledge of the microorganisms responsible (identification),
the infection site and the patient's condition. Laboratory assistance
may be obtained to determine this choice.
|
Antibiotic
susceptibility testing
A test intended to demonstrate the susceptibility of a microbe
(generally a bacterium) to various antibiotics, with a view
to selecting the most effective antibiotic to combat the microorganism.
With the result of this test, physicians can prescribe the
most suitable medicinal product for the patient, the disease
and the bacterium responsible for the infection.
|
B
Bacterium
Microbe or microorganism consisting of a single cell (with
a single nucleus and a single chromosome) and responsible
for so-called bacterial infection. Bacteria are small structural
living units; they are not visible to the naked eye but remain
larger than the largest viruses (approximately 100 times);
they can proliferate very rapidly (Escherischia coli
doubles its population every 20 minutes) and are responsible
for bacterial infections that can be combated using antibiotics.
Sometimes, they have a beneficial role in the human body by
contributing to its homeostatic balance (skin, intestine).
| |
Bacterium |
Virus |
| Size |
~1µm |
~1nm |
| Antibiotics |
Effective |
Ineffective |
| Visible with |
Optical microscope |
Electron microscope |
| Can survive |
Outside cells |
Obligately intracellularly |
| |
|
|
| |
|
|
Examples of bacterial diseases: tuberculosis, tetanus, furuncles,
whooping cough.
Examples of viral diseases: AIDS, Chickenpox, Shingles, Influenza,
Mononucleosis (Glandular fever), Sore throat.
|
C
Cancer
Derived from the Greek word karkinos meaning crab or pincers,
the Latin word cancer, meaning crab or crayfish, was adopted
at the end of the 15th Century to mean a malignant tumor (the
terms canker and chancre are also found). The majority of
cancer cases have environmental causes, i.e. they are triggered
by external factors. 7 million people died of cancer worldwide
in 2002 (WHO).
Cancer is not – other than in rare exceptions –
a disease caused by a virus or bacteria; therefore it is rarely
an infectious disease. Cancer originates in the genes of cell
which deviates from normal behavior; it grows very quickly
and does not fulfill the usual functions of a normal cell.
In many cases, biology (analytical laboratory) offers tests
which detect these anomalies by detecting a molecule released
by the abnormal cell in the blood (tumor markers).
The most common forms of cancer include cancer of the lungs
(frequently caused by smoking), blood (leukemia, lymphoma)
and breast. |
D
In
vitro diagnostics
An in vitro diagnostic test is performed by means of chemical
analysis (e.g. glucose, cholesterol or sodium measurement)
or biological analysis of a specimen, in order to identify
microorganisms and determine their characteristics. In vitro
diagnostics are used to assay, identify and quantify bacteria
(exogenous agents) and viruses, and other endogenous agents
(or "markers"), i.e. substances generated by the
body in the presence, for example, of an infectious disease,
cancer or a heart irregularity. The markers may take the form
of proteins or genetic sequences, or other biological molecules.
In traditional Chinese medicine, diagnosis is based on observation
(body, mind, behavior), the senses (hearing, smell), the interview
with the patient (shivering, sweats, fever, stools, urine,
sleep), palpation (pulse). This method may be sufficient in
some cases but must be increasingly completed by more modern
methods making use of biological liquid specimens. In both
approaches, clinical and biological, medicine finds a complementarity
now necessary for an accurate and reliable diagnosis.
|
Molecular
Diagnostics
New approach to diagnostics consisting, for example, in studying
a human cell, virus, bacterium or parasite, by analyzing its
genetic inheritance (DNA or RNA) directly.
|
DNA
Deoxyribonucleic Acid
DNA is a template containing all the instructions the body
requires to build and maintain itself: only 4 variables (called
bases) are combined together to code protein production; they
are represented by the letters ATGC (Adenine, Tyrosine, Guanine
and Cytosine). DNA forms the basis for all genetic information.
It is often represented by a "double helix"; it
was discovered by Watson and Crick in 1953. Many attempts
are currently underway to study it or to try to correct its
errors. A large number of laboratories throughout the world
are working on its decryption.
|
DNA
chips
DNA "chips" consist ofa substrate on which several
thousand to several tens of thousands of probes are grafted.
Each probe will be able to specifically recognize a substance
such as a given mRNA sequence. Therefore, DNA chips make it
possible to perform several tens of thousands of tests simultaneously
on a very small surface. The logic follows that of mass data
production, as for sequencing. |
E
Epizootic
This term defines an "epidemic affecting, in a more or
less vast region, one kind of animal (particularly domestic)
species" (Hachette dictionary). An example of an epizootic
disease is foot and mouth disease; the livestock population
is frequently too large to be able to carry out immunization;
slaughter is sometimes the only eradication solution (as in
the case of bird flu); in this case compensation was awarded.
|
F
Food
safety
Monitoring our food by checking its sources, composition and
detecting sources of bacterial contamination. Bacteria and
viruses may be transmitted from animals used in human foodstuffs
at any time in the food production and processing chain. Monitoring
is performed at all stages of product production; however,
one final stage remains subject to little or no monitoring:
household refrigerators. Considerable contamination or bacterial
growth appears to occur in this final storage stage immediately
prior to consumption; simple measures such as regular disinfectant
cleaning of the inside walls of the refrigerator may suffice
to prevent the dangers of food poisoning.
|
G
Gene
The gene is the basic unit of genetic information (or hereditary
message) contained in chromosome DNA; it is the smallest nucleotide
sequence which contains all the information required for the
synthesis of a protein (a precisely ordered set of amino acids).
The gene stores and transmits the hereditary properties of
living beings. The genome is the set of hereditary characteristics
carried by the DNA. It is present in its complete form in
all the organism's cells.
The human genome consists of over 25,000 genes (it was thought
that there were 4 times more!); the complete human genome
sequence was established in April 2003; this field has been
marked by an intense battle over the notion of public or private
ownership of the discovery. Patent registration has taken
on major importance. The average bacterial genome consists
of several thousand genes.
|
Gene
therapy
This is defined as the deliberate introduction of genetic
material into human somatic cells with a view to correcting
a genetic defect (functional gene defect) or make up for a
protein deficiency by providing the gene responsible for its
synthesis. This hypothesis dates back around forty years and
was initially intended to treat rare diseases or diseases
in which a single gene was involved (haemophilia, myopathy).The
nucleic acid in the gene (DNA) becomes the medicinal product
supposed to cure the disease by attacking it at source. |
Generation
time
Microorganisms like heat, humidity and sugar, but not too
much. Their population grows according to a rate specific
to each species: the generation time. For example, bacteria
such as Escherichia coli multiply by 2 every 20 minutes:
| If we have at time=0 |
2 bacteria |
| after 1 hour |
16 bacteria |
| after 2 hours |
128 bacteria |
| after 4 hours |
8,192 bacteria |
| after 6 hours |
524,288 bacteria |
| after 8 hours |
33,554,432 bacteria |
| after 12 hours |
137,438,953,472 bacteria |
Therefore, in order to delay or treat an infectious disease,
it is necessary to stop the microorganisms from proliferating
or even kill them. If, for example, the number of microorganisms
are reduced from 1,000,000 to 10, the few microorganisms present
are not sufficient in number to trigger disease.
|
H
Health
WHO definition of health
According to the World Health Organisation, health is a state
of complete physical, mental and social well-being and not
merely the absence of disease or infirmity.
The correct bibliographic citation for the definition is:
Preamble to the Constitution of the World Health Organization,
this definition has not been amended since 1946. |
Hepatitis
Hepatitis is an inflammation of the liver, inducing varying
levels of destruction of hepatocytes, the main liver cells.
Therefore, it is the consequence of an attack by viruses or
toxic substances (medicinal products, venoms, etc.) and not
the direct cause. Cases caused by viruses are referred to
as viral hepatitis.
There are several types of viral hepatitis; some were discovered
recently:
| Hepatitis type |
A |
B |
C |
E |
| Year discovered |
1973 |
1964 |
1989 |
1990 |
| Number of cases in the world (millions) |
|
1,000 |
170 |
|
| Number of deaths per year
(millions) |
|
2 |
|
|
| Number of chronic carriers (millions) |
|
300 |
|
|
| Existence of vaccine |
Yes (1994) |
Yes |
No |
No |
| Severity |
+ |
+++ (cancer) |
+++ (chronic) |
+ |
| Prevention |
Hygiene rules |
Condom use
Transfusion testing |
Transfusion and syringe
testing, endoscope disinfection |
Hygeine rules |
Hepatitis D is a very similar to hepatitis B and is not described
in this table.
Comparative risk of HIV and Hepatitis B
| Number of milliliters
of blood sufficient for contamination |
| Viral hepatitis B |
0.0004 |
| Human immunodeficiency virus |
0.1 |
A subject encountering the virus for the first time is at
a much higher risk of contracting disease from hepatitis B
than with the AIDS virus.
|
Hygiene(Simple
and universal rules)
Wash hands before and after treating a victim
Wear disposable gloves
Wear clean clothing
Good technical procedure practices reducing the infectious
risk as much as possible, in view of the conditions of the
emergency
Disinfect transport vehicles regularly (ambulance, transport
vehicle, mobile hospital unit, etc.)
Decontaminate equipment after use
These few principles can be summarized by the Hygiene Triangle
with these 3 components:
Healthcare professionals (first-aid workers, fire department,
ambulance workers, nursing staff or doctors)
The victim
The equipment, vehicle (ambulance, transport vehicle, mobile
hospital unit, etc.) with the main carriers in disease transmission
being:
Hands
Biological fluids |
I
Infectious
disease
The most deadly diseases
Six groups of diseases alone represent 90% of deaths due to
infection worldwide:
| Acute respiratory diseases, bacterial
(pneumococci) and viral (influenza, syncitial respiratory
virus) |
3 million deaths each year |
| AIDS/HIV (virus) |
3 million deaths in 2001 |
| Diarrheic diseases (rotavirus, shigellosis,
pathogenic Escherichia coli, cholera, typhoid fever) |
2.5 million deaths each year |
| Tuberculosis (bacterium) |
Almost 2 million deaths each year
and 8 to 80% of cases, depending on the country, associated
with the AIDS epidemic. |
| Malaria (parasite) |
Over 1 million deaths each year and
300 to 500 million annual clinical cases |
| Measles (virus) |
900,000 deaths each year, even though
there is a vaccine which could prevent this mortality…
|
Infectious disease is responsible for 43% of deaths in developing
countries as opposed to 1% in industrialized countries.
In addition, it is important to include the mortality attributed
to some forms of cancer, which is not generally known: at
least 16% of cancer is of infectious origin.
|
Influenza
Influenza (or the 'flu) is a term used to describe a clinical
condition: influenzal condition; therefore, it is a "syndrome"
combining several characteristics: fever, tiredness, more
or less combined with coughing. This symptom is the main sign
of Influenza which can occur in sometimes massive epidemics,
during the wintertime. In addition, an effective vaccine (influenza
vaccine) is available for this disease which is renewed each
year. Therefore, chicken influenza is a disease found in chickens
which resembles human influenza. As the virus responsible
is similar to the human virus, it can be transmitted to humans
after a slight adaptation. |
M
Microbes
General term to describe a very small cell, invisible to the
naked eye: virus, bacterium, fungus, parasite responsible
for infectious disease.
Bacteria form (with the presence of water) the basis for all
life on Earth; the majority of bacteria are beneficial to
life and are present in or on our body (skin, intestine) without
causing any harm; sometimes, bacteria can be responsible for
infections that must be treated using antibiotics. Viruses
obligately need to colonize a cell to develop: they use the
internal machinery of the cell to produce what they are lacking:
proteins.
Viruses are not capable of proliferating alone; they need
to invade a cell to survive using its internal resources to
proliferate. Like bacteria, viruses can be responsible for
a large number of infections in humans, plants and animals:
influenza, chickenpox, AIDS, viral hepatitis. Antibiotics
are not effective in combating viruses, only antivirals are
capable of being effective. One of the best ways of combating
viruses is to be immunized when the vaccine is available (influenza,
viral hepatitis B, viral hepatitis A).
Microscopic fungi are also responsible for infections known
as mycoses (from the Greek mukês = fungus). They have
an affinity for keratin, the main constituent of superficial
body growth particularly inducing frequent infections on the
skin, hair and nails. The medicinal products used to combat
mycoses are antifungals frequently, in the form of ointments.
A large number of diseases are induced by parasites: amoeba,
malaria, oxyuris (ringworm), etc. These diseases are treated
with medicinal products known as antiparasitics. However,
in some cases, it is difficult to obtain protection: either
because the medicinal product is inaccessible (poor countries)
or because it does not exist. The major parasitic disease
in the world is malaria which still kills almost 1 million
people each year.
|
Molecular
biology
Science devoted to the living world through the knowledge
of its specific molecules. These molecules are fundamental
constituents of living organisms. DNA consists of genes giving
the signal to cells to produce all the constituent parts of
the organisms required for it to function (hormones, enzymes,
growth factors). By studying these factors using molecular
biology techniques, it is possible, for example, to understand
how a cancerous cell functions by specifically identifying
oncogenes (Genes which induce cancer). Similarly, molecular
biology can now be used to anticipate bacterial and viral
resistances to treatments.
By isolating and then multiplying the genetic information
for bacteria and viruses, it is possible to identify them
very accurately, rapidly and reliably. |
R
Reservoir
A reservoir is a place where microorganisms are able to proliferate.
For this, they have certain needs for their development. The
medium (or host) must be a favorable site for this development.
For example, rats are a reservoir for fleas capable of causing
plague.
Humans can be a reservoir of virus without being ill; these
are known as healthy carriers: for example, a patient or victim
may be a carrier of the HIV (AIDS) virus and not be ill. His/her
body is said to be a "reservoir" for the virus.
The same applies for certain diseases transmitted by a lack
of hygiene (dirty hands diseases) where it is possible to
host bacteria without being ill but transmit the bacteria
to someone else and trigger symptoms in the other subject.
|
S
SARS
This is a severe febrile (fever > 38°) pneumopathy
(lung infection) that can progress toward respiratory failure.
The agent responsible is a virus (coronavirus). The disease
is transmitted from human to human due to close contact with
an infected subject. The vast majority of cases concern healthcare
professionals. The cases reported to date in South-East Asia
were directly linked with another case (patient-medical staff
relationship or close family). There is no patent argument
to date that the disease is transmitted by a single or remote
contact with an affected subject. Transmission via oropharyngeal
or respiratory secretions and possibly also biological fluids
is suspected. In the event of fever above 38°C associated
with respiratory signs (coughing, shortness of breath, discomfort)
in a subject from a country experiencing active transmission,
this disease must be considered. Current identification techniques
(molecular biology) make it possible to obtain a response
in 3 days following sampling. |
STD
(or STI)
Sexually transmitted or transmissible diseases (or STI Sexually
Transmitted Infections).
Sexually transmitted or transmissible diseases or STDs are
infectious diseases transmitted during sexual intercourse.
They are frequent and highly contagious. They denote at-risk
behavior meaning that several STDs are frequently associated.
Some are particularly severe; they are caused by bacteria
(chlamydia, mycoplasmas, gonococcus, treponema), viruses (HIV,
Hepatitis) or parasites (trichomonas).
The frequency of STIs is linked with sexual practices and
includes an important social aspect; prevention can be obtained
by educating populations and providing information on the
risks involved (for mother, unborn children or partners).
AIDS is a sexually transmitted disease and should above all
be treated through the use of condoms.
|
T
V
Viral
load
Evaluation of the number of viruses in a biological medium.
Most frequently, using a blood sample, the viral load is measured
in the plasma. It is representative of the extent of the presence
of the virus in the body. This analysis has seen considerable
development with monitoring of the AIDS epidemic by assaying
the number of viral particles (HIV human immunodeficiency
virus) in the blood of treated patients to monitor their progression.
This test is very informative on the therapy to be implemented
as it may differ from one patient to another.
|
Virus
Viruses are small infectious agents with genomes consisting
either of DNA or RNA (never both), without their own metabolism
and incapable of proliferating outside living cells. The Virus
is an intracellular parasite responsible for infection. When
it enters a body, it diverts the infected cell's reproductive
systems for its own proliferation. They are smaller than bacteria
and remain invisible under an optical microscope. They can
sometimes be destroyed by antiviral substances.
Example of diseases of viral origin
| Disease |
Virus responsible |
| Measles |
Measles virus |
| Influenza |
Influenza virus (Myxovirus) |
| Hepatitis |
Hep A, B, C, D, E viruses |
| AIDS |
HIV virus |
| Warts |
Papillomavirus |
| Mononucleosis (Glandular fever) |
EBV (Epstein-Barr Virus) |
| Some forms of bronchitis |
Adenovirus |
| SARS |
Coronavirus |
|
W
WHO
World Health Organization
"The World Health Organization is the United Nations'
specialized agency for health. It was established on 7 April
1948. WHO's objective, as set out in its Constitution, is
the attainment by all peoples of the highest possible level
of health. Health is defined in WHO's Constitution as a state
of complete physical, mental and social well-being and not
merely the absence of disease or infirmity. WHO is governed
by 191 Member States through the World Health Assembly. The
Health Assembly is composed of representatives from WHO's
Member States. The main tasks of the World Health Assembly
are to approve the WHO programme and the budget for the following
biennium and to decide major policy questions."
|
Z
Zoonosis
Term derived from the Greek zôon: animal, and nosos:
disease.
Pathology (disease) essentially affecting animals. This term
is generally used for diseases which are transmitted from
animals to humans and vice versa. The term anthropozoonosis
refers to diseases which are exclusively transmitted from
animals to humans.
It is also interesting to note that some diseases can be transmitted
from humans to animals.
Example of zoonosis
Cats are liable to successively transmit:
Toxoplasmosis via ingestion of food containing excrement (stools)
Mycosis (fungi) via skin contact
Pasteurellosis via bites
Cat-scratch disease
Rabies via bites
Dogs
Via ingestion of parasite eggs: toxocarosis
Via ingestion of parasite eggs: hydatidosis
Via skin contact: mycosis
Via Phlebotomus bites: leishmaniosis
Via bites: pasteurellosis or rabies
Birds
Via ingestion of contaminated water or food: salmonellosis
By inhalation: mycobacteriosis or ornithosis
Via bites: pasteurellosis
By inhalation: psittacosis
Horses
Via mosquito bites: equine encephalitis
Via skin contact or by inhalation (absorption via respiratory
tract): glanders
Via bites: rabies
Via ingestion of insufficiently cooked meat: trichinosis
Cattle
Via ingestion of insufficiently cooked meat: listeriosis or
beef worm
Via ingestion of dairy products: bovine tuberculosis
Via skin contact or ingestion of dairy products: brucellosis
Via skin contact or by inhalation: anthrax
By inhalation or via tick bites: Q fever.
Via bites: rabies
By milking cows: vaccinia
Sheep
Via skin contact or ingestion of cheese among other things:
brucellosis
Via skin contact and by inhalation: anthrax
Via ingestion of fluke contained in insufficiently washed
watercress: liver fluke
Following shearing or milking: orf
Via bites: rabies
Via ingestion of insufficiently cooked meat: toxoplasmosis
Monkeys
Via bites: herpes B virus encephalitis
Via mosquito bites (Aedes Aaemagogus): yellow fever
Via bites: rabies
Pigs
Via skin contact: brucellosis
Via injury with bone from contaminated animal: swine erysipelas
Via ingestion of insufficiently cooked meat: pork worm or
trichinosis
Tortoises
Via ingestion of contaminated water: mycobacteriosis
Via ingestion of contaminated water or food: salmonellosis
Rats
Via contact with skin or mucosa and urine via water: leptospirosis
Via flea bites: plague
Via bites: rabies
Via arthropoda bites: rickettsiosis
Via bites: sodoku
Foxes
Via bites: rabies
Via ingestion of berries contaminated with fox excrement:
echinococcosis |
|
Read others articles from BioMérieux