Download 25 Microbial ecology

Chair of Microbiology, Virology, and Immunology
MICROBIAL ECOLOGY
Lecturer Prof. S.I. Klymnyuk
Ecology (oicos – house, hold, logos - doctrine) - science about
legitimacies of creation and functioning of biological systems and
their mutual relation with an environment.
The microecology is the science about places of invading of
microorganisms and their ecological links.
At learning a microbial ecology use the same concepts, as well as in a
common ecology.
Main of them are the following: population -
an elementary
evolutional unit (structure) of a definite species;
biotope - site, habitation of a population, for parasites - place of their
localization in an organism;
microbiocenosis - microbial assemblage, association, that is collection
of populations of different species of microorganisms, which
dwell(live) in the defined biotope (for example, in an oral cavity,
reservoir);
ecosystem - system, in which enters a biotope and microbiocenosis
From old times it is known, that the microorganisms are
omnipresent, that is ubiquitous organisms. Huge
quantities of them meet in soil, water and air. The
environment of their habitation is plants, animal, man.
Everywhere bacteria are existed as microbiocenoses.
The modern microbial biocenoses were generated as a
result of durable evolution. Mutual relation
(cohabitation) of different species of microbes among
themselves and with other forms of life are called
symbiosis.
Types of symbioses
1.
Neutralism - the populations, existing in one
biotope do not stimulate and do not oppress each other.
2.
Mutalism - mutually advantageous cohabitation;
one population synthesizes materials (matter), which are the
basis of power supply for another (for example, legume
bacteria and bean plants, aerobic and anaerobic bacteria in
an organism of the man).
3.
Commensalism - such form of symbiosis, at which
one of jointly living populations extracts for herself
advantage(benefit), but does not put a harm of other
population. The commensalism is characteristic for many
inhabitants of human body.
Types of symbioses
4.
Antagonism - oppression of one population
another. The microbes – antagonists produce antibiotics,
bacteriocines, fatty acids, which cause destruction of
bacteria or delay their reproduction.
5.
Parasitism - such kind of symbiosis, at which one
population (parasite) brings harm to the host, and for itself
has a benefit. The causative agents of bacterial, virus and
fungic illnesses concern to microbes - parasites.
Microflora of the soil
The soil is the major environment for a habitation of microorganisms.
The first bacteria, as well as all alive ones, have appeared in water.
However in more later geological periods, when on a surface of globe
the soil was derived, it became main habitation of microorganisms and
main arena of their vital activity.
The amount of bacteria in one gram of soil can be very great - from
200 millions up to 10 billions. Manured and ploughing ground are
stocked with microorganisms most densely. The soil of woods, moor,
the sands of desert contain few microbes. The most surface sphere of
soil (crust by width of 2-3 mm) is very poor by microorganisms. A
desiccation and the solar rays perniciously influence them. The ground
mass of bacteria is on depth 10-20 cm. On depth of 1,5-2 m of
untouched ground the microbes do not meet almost.
The microflora of soil includes hundreds of species of bacteria, viruses,
protozoa, actinomyces and fungi. It is various species of putrefactiving,
nitrifying, denitrifying, nitrogen-fixing bacteria. The most often
inhabitants of soil are the representatives of genus Azotobacter,
Nocardia, and Clostridium. Many bacteria of genus Rhisobium,
Nitrosomonas, Nitrosospira, Nitrobacter, Pseudomonas are very often
found. Almost always there are denitrifying bacteria (B.denitrificans),
ammonifying microbes (Urobacillus pasteurii, Urobacillus leybii),
numerous iron bacteria and sulphur-bacteria. All of them play the great
role in a turnover of materials in a nature, improve productivity of our
fields, provide life on the Earth. The microorganisms of soil take an
active part in all processes of transformation of materials and energy:
synthesis of a biomass, biological nitrogen fixation, fermentation,
corruption, denitrification of the cycle sulfur, iron lactas, phosphorum,
carboneum and other elements.
Carbon cycle in nature
Nitrogen cycle in nature
Nitrogen fixing bacteria
With discharges of the sick people and animals into soil
can get and some time such microorganisms as C.tetani,
C.perfringens, C.novyi, C.botulinum, S.typhi, Shigella
spp. and others will be saved.
The important value soil microflora has during
wars. At mass wounds the danger of contamination of
wounds by ground is considerably enlarged. It contains
spores of anaerobic bacteria, which penetrating in a
wound can cause such serious wound fevers as a tetanus
and anaerobic gas infection. It always should be taken
into account in the system of prophylaxis of
communicable diseases.
Sanitary - indicative bacteria of soil are Escherichia coli,
Streptococcus faecalis, Clostridium perfringens and
termophilic bacteria. A degree of fecal contamination of
soil is determined on presence and quantity(amount) of
first three species. More exact rating is manufactured at
definition coli - index, that is amount of bacteria E.coli in
1 g of soil. Also general microbial number (GNM) quantity(amount) of all saprophytic bacteria in 1 g of soil
is examined.
The soil is considered pure, if its coli-index does not
exceed 2000, and the quantity of termophilic bacteria is in
limits 100 - 1000. Under the epidemic indications soil also
is inspected on presence in it pathogenic bacteria
(Salmonella,
Shigella,
C.tetani,
C.botulinum,
Cl.perfringens, B.anthracis and others).
Microflora of water
Water is a natural medium of a habitation of various
microorganisms. In sweet and salty waters representatives of
all groups of bacteria are found Protozoa, Fungi, Viruses,
Water - plant. The collection of all aqueous microorganisms
is named as a microbial plankton. The microflora of
reservoirs consists of two groups of microbes: autochtonal
(or aqueous) microorganisms and allochtonal (brought from
the outside). The autochtonal microflora are presented by
microorganisms, which permanently live and are multiplied
in water. It is more often such species: Micrococcus
candicans, M. roseus, Sarcina lutea, Bacterium aquatilis
communis, Pseudomonas fluorescens. The anaerobes
represent by species Clostridium, Bacillus cereus, B.
mycoides.
The microbial composition of water is in the large degree
mirrors a soil microflora. A major factor, which determines
quantity of microbes in water is presence in it of necessary
nutritious materials, that are various biological matters.
Main path of microbial contamination of water is
penetration of unpurified waste from sewage of the
populated area. Therefore, the more water is polluted with
similar organic matters, there are more in it of
microorganisms. It is distinguished polisaprogenic,
mesosaprogenic and oligosarpogenic zones of water.
Zones of water clearness
1.
Polisaprogenic zone is the zone of strong
contamination. It contains many organic matters and
almost there is no oxygen. The quantity of bacteria in 1
ml of water reaches one million and more.
2.
Mesosaprogenic zone is the zone of moderate
contamination(pollution)). In it the nitrifying and
aerobic bacteria prevails. The total number of
microorganisms compounds hundreds of thousand in
one ml.
3.
Oligosaprogenic a zone (zone of pure water).
The quantity of bacteria changes from 10 up to 1000 in
one ml.
Sometimes the pathogenic bacteria in water can get and
they will be saved for some time: S. typhi, V. cholerae,
S. dysentеriae. Often various viruses are found:
Polioviruses, Hepadnaviruses, Enteroviruses and others.
The pathogenic microorganism getting in reservoirs,
abundant in a zone of strong contamination, gradually die
in a zone of moderate contamination. They are almost not
found in oligosaprogenic zones.
Water plays very important role in epidemiology of many
contagious diseases (typhoid, dysentery, cholera,
poliomyelitis, virus hepatites and others). The causative
agents of these illnesses are discharged with feces of the
patients and carriers. Together with sewage they enter in
water of open reservoirs. In summer time some bacteria,
including Vibrio cholerae, can even multiply. To catch it is
possible through ice, in which the pathogenic bacteria can
be saved during several weeks and even of months.
The most important metrics of fecal contamination of
water all over the world is examination of bacteria of an
intestinal rod group. Under this common concept combine
bacteria of the family Enterobacteriaceae (Citrobacter,
Escherichia, Enterobacter, Klebsiella). It is gram-negative
rods fermenting lactose and a glucose up to an acid and
gas within 24 hours. These bacteria are discharges in an
environment only with feces of the man and
hematothermal animals. Among them are coliform rods,
which ferment lactose at 37 C to an acid and gas. From
this group fecal intestinal rods are selected, which ferment
lactose at 44,5C. These bacteria determine fresh fecal
contamination. The index of fecal contamination is
definded also by means of S. faecalis, C. perfringens,
Proteus and coliphages.
In many countries for a rating of quality of potable water
the normative documents or state standards are taken.
Microbiologic index of safety of potable water are the
following:
1. Common microbial number in one ml of water no more than 100.
2. Number of bacteria of intestinal rod group (coliindex) in 1000 ml of water - no more than 3.
3. Index of fresh fecal contamination,
that is
quantity(amount) E.coli in 1000 ml of water absence.
4. Quantity coli-phages (number of colony-forming
units) in 1000 ml of water - absence.
Besides in 25 litters of potable water pathogenic
Protozoa (cyst of lamblia, dysenteric amebas,
balantidia) and ovum of helmints there should be
absent.
Common microbial number of water is examined by
inoculation of 1 ml of water in melted and refrigerated up
to 50 C in agar in Petri dishes. Coli-index is determined
by a method of membrane filters or fermentation tests.
Microflora of air
Air for microorganisms is less favorable environment, than
soil and water. There are almost no the nutritious materials
necessary for reproduction of bacteria. Desiccation and the
ultraviolet rays operate perniciously on microorganisms.
Nevertheless, many microbes in air can be saved more or
less long time. The composition of a microflora of air is
very various. It depends on cleanness of air, deposits,
temperature, humidity, climate and geographical conditions.
Than it is more in air of a dust, smoke, soot, the more
microorganisms. Vice-versa, above mountains, seas, oceans
and woods, where air is pure, it is not enough of microbes.
Main sources of microbial air pollution is the soil, water
and man.
In natural conditions in air there are hundreds saprophytic
microorganisms. A microflora of air is divided on resident
(it is more often) and temporary, less resistant (it is found
out is sporadic). The greatest quantity of microbes stocky
layers of an atmosphere contains.
The constant microflora of air is shaped at the expense of
soil microorganisms. In its composition many species of
Actinomyces, Penicillinum, Aspergillus, Mucor and others
go into. There are many Micrococcous roseus,
M. candicans, M. luteus, Sarcina lutea, S. alba, S. rosea,
Bacillus subtilis, B. mycoides, B. mesentericus. In open air
spaces there are less of microbes, than in the closed rooms.
The contamination of air by the pathogenic microorganism
descends by a trickling way in composition of aerosol. It is
derived during talk, cough, sneeze. The microbes get in air
also with particles of an epithelium of dermal integuments.
They are durably saved in air and up to a sedimentation is
evaporated. The dust phase has large drops, which fast
settle and are evaporated. The bacteria in such phase can
are transferred on the large distances. This is very
dangerous. They can penetrating into lungs.
The patient may discharges pathogenic bacteria and viruses
together with a sputum, spit and salive. Even the healthy
man at one sneeze discharges in air 10000-20000 microbial
bodies, and the patient - in many times more.
The quantity of microbes in air varies in the large ranges from several bacteria up to tens and hundreds thousand in
1 м3. In one gram of a dust can be up to 1 million of
bacteria. Total number of bacteria in 1 м3 of air is accepted
for expressing by general microbial number. A sanitary hygienic rating of air is made not only according to general
microbial number. More important value has revealing
sanitary - indicative microorganisms. Such bacteria are the
representatives of a microflora of upper respiratory tract:
Streptococci haеmolyticus, S.viridans, Staphylococcus
aureus.
The large value there is a cleanness of air in operation
rooms, reanimation department, dressing rooms, maternity
halls and chambers for neonatal. Total number of microbes
in operation hall before the operation should not exceed
500 in 1 м3, and after operation - 1000 in 1 м3. The
quantity of haemolytic and viridans streptococci should
not be at all.
Examination of air microflora is made according to
Koch’s sedimentation method or Krotov’s aspiration
method.
Microflora of foodstuff
In foodstuff there is a specific microflora, which adds
them the defined gustatory qualities and consistence
(curdled milk, yogurt).
The microflora can penetrate into many products from the
outside - nonspecific microflora. The intensive
reproduction of separate species of bacteria makes products
unsuitable for the use. Often foodstuff contaminate with
bacteria of such genus as Salmonella, Shigella,
Staphylococcus, Escherichia, Clostridium botulinum,
C.perfringens, C. difficile. They can cause typhoid,
dysentery, cholera, gastroenteritis, botulism and other
illnesses.
Milk contaminate with
such microbial genus as
Staphylococcus,
Streptococcus,
Mycobacterium,
Salmonella, Brucella, Enterovirus. It happens at milking,
transportation and processing of milk and lactic products.
Meat is contaminated during disease of animals and
poultry, during their killing, cutting, incorrect storage and
transportation. Often in meat it is found the representatives
of
genus
Salmonella,
Proteus,
Staphylococcus,
Streptococcus, Clostridium.
The fish is contaminated by many species of
microorganisms. They get in it from water, flakes, intestine,
hands of staff, which handles fish production. The most
dangerous bacteria are C.botulinum, V.parahaemolyticus.
There may be also causative agents of a typhoid,
dysentery, cholera, hepatites.
Vegetables and fruit are contaminated by species of
Salmonella, Shigella, Vibrio, Enterovirus. They get from
hands of the people, which gather, transport and sell these
products. The incorrect preservation of vegetables
(tomatoes, mushrooms and others) can cause botulism.
Eggs often are infected by Salmonella, Fungi,
Actinomycetes, and egg powder by Staphylococcus.
Especially dangerous are the eggs of gooses and ducks.
Bread product are poorly favourable environment for
reproduction of the pathogenic microorganism. Only
products from the overwintered grain cause sometimes
toxic agranulocytosis. It is caused by the representatives of
species of Fusarium.
The bacteriological research of foodstuff is spent in the
scheduled order for a control, at doubt concerning quality
of products and at originating alimentary toxinfections. The
main task of microbiologic research of foodstuff is the
definition of total of bacteria and detection sanitary exponential species. For the majority of foodstuff such
bacteria is E.coli and other representatives of group of
intestinal rods. In some foodstuff the presence of anaerobic
microorganisms and their toxins, and also representatives
of genus Salmonella and Proteus are examined.
The prophylaxis of diseases, which are transferred
through foodstuff, consists in keeping sanitary - hygienic
rules of their manufacture, saving, transportation and
implementation. Very important also is keeping the
correct technology of preparation of foodstuff, especially
canning production. Especially dangerous are the canned
food of domestic manufacture. The large value has
sanitary knowing of the workers of public catering.
Rhizopys, common bread mold
Molds
Normal microflora of humans
The microflora of the human is a complex of
microbiocenoses, which meet in an organism of the healthy
people. They were generated during evolution, and are
characterized by surprising persistence. The quantity and
species composition of a normal microflora are influenced
age, sex, climate, feeding habits, bacteria of an environment,
individual sanitary and hygienic habits etc. Special role in
change of a microflora play antibiotics, chemotherapeutic
and immunological drugs. They render the large selective
influence on a population of some bacteria. These medicines
delay sensitive individuals and promote development of
resistance species. The struggle with these resistant bacteria
is one of difficult and urgent problems of practical medicine.
The organism of the man is occupied more than 500
species of bacteria, about 50 species of viruses, more than
20 species of protozoa. It is a huge zoological garden. The
total number of microorganisms on a skin and in cavities
of the man makes 1014. It is in 10 times more, than all
cells of the macroorganism. However internal
environment (blood, lymph, tissues and organs, which are
not connected with an external environment) are sterile.
The normal microflora of the man is compounded with two
groups of bacteria: 1. A resident or constant microflora. It
is often named indigenous or autochthonous microflora.
2. Transitory, Temporary, facultative or allochthonous
microflora.
Normal microflora is represented mainly by anaerobic
microorganisms. It consists mainly of representatives of
three genus: Bifidobacterium, Bacteroides, Clostridium. On
their part there is 95-97 % of all microflora. This
legitimacy is characteristic for a skin, mucous, in cavities
and in an intestinal path. Namely it makes a resident
microflora. The aerobic bacteria compound 3-5 % of all
microorganisms and fall into transitional part of a
microflora. However, its separate representatives can be the
evident residents (Staphylococcus, Corynebacterium,
Escherichia and others).
The very important feature of a normal microflora of the
man is that it is strictly individual and anatomically is
stable. How many people exist so many individual
microbial assemblages are. The bacteria from the neighbour
to the neighbour can be transferred, but the transmit
bacteria, as a rule, do not get accustomed.
The individual stability of a microflora is so expressed, that
in America the patent for definition of a criminal on his
microflora detected on a place of a crime is registered. The
anatomical stability means, that the microflora of an oral
cavity and nose does not get accustomed on a skin and
other. Any time the microflora, which has got on the given
biotope, can be, but permanently is not saved.
The fetus during pregnancy is sterile. During genus the child is
contaminated by a microflora of patrimonial paths of the mother. It is
representatives of genus Lactobacterium, Streptococcus, Escherichia
more often. Further in an organism the neonatal microbes enter from
hands, mammas both respiratory paths of the mother and serving staff.
They also enter from an environment.
The constant (stationary) microflora starts to form since the tenth day.
On mucous in the beginning there are filamentous microorganisms. They
will form a continuous grid, which covers a surface. On these
filamentous bacteria start to be adsorbed microorganisms, which will
derivate solid layer or biofilm. Since 20-25 days after birth a skin and
mucous become covered by a most thin biofilm, which consists of a
mucin and polysaccharides of a microbial origin. In thickness of this
biofilm there is a plenty of microorganisms. They are allocated not
single, and as original colonies. The thickness of a biofilm in different
places (biotopes) is various. It is very thin on a skin and mucous of nose,
but reaches the large thickness on a mucous colon.
Microflora of a skin
The quantity of microorganisms on a skin can vary in the large
limits: from 100 microbial bodies on 1 см2 in the field of a
forearm up to 2,5 million/см2 in axillary fosses. From a
surface of a skin of the man is washed off about 1,5 billion of
bacteria. Density of microbial populations on a skin is
subjected daily, monthly and seasonal fluctuations. It also
depends on a status of health, trade, age, sex etc.
Most typical the representatives of the inhabitants of a skin are
Propionibacteria,
Corynebacterium
species
(C.acnes,
C.xerosis,
C.pseudodiphtheriticum,
C.minutissimum,
C.lipоphylicum) and species Staphylococcus (S. epidermidis,
S.saprophyticus, S.hominis, S.haemolyticus, S.capitis – total
29 species) are. Approximately for 10 % of the people on a
skin as found S.aureus.
Skin bacteria
There are representatives of a species Micrococcus
(M.luteus, M.varians, M.roseus, M.sedentarius and others),
fungi of genus Pityrosporum (P.ovale, P.orbiculare) less
often. Find species of Mycobacterium (M.fortuitum) and
Clostridium (C.perfringens, C.cereus), Bacillus and
C.albicans are less often.
Each anatomical isolated zone (biotope) has the specific
features concerning quantity and species composition.
American microbiologists Bibel and Lovel have made skin
flora maps.
From the epidemiological point of view important biotopes
are the perineum, skin in a place of operational cuts,
mammas of the puerperas and feeding mothers skin of the
face, axillary recesses. Very often microflora of mammas
can cause purulent - septic diseases for the mother and
child.
The surgeons have offered many ways of processing of
hands before the operation. However not any of them does
yields an absolute sterility. Durable washing of hands (3-5
minutes) water with soap and brush results in decrease of
bacteria in 10 times. In 10 minutes of continuous washing
the quantity of bacteria is again enlarged, and in 15 minutes
their quantity becomes more, than before washing. It
happens because the microbes begin to come out of depths
of a skin (bag of hair, ducts of sweat glands). The surgeons
began to handle hands by alcohol, by iodine or to dress
gloves.
The healthy pure skin has well-marked bactericidal
properties. It is stipulated by presence on a skin of
unsaturated fatty acids, immunoglobulins of sweat etc.
However, at violation sanitary - hygienic mode, standard
conditions of work and life, at operation of various
chemical materials (colour, varnishes, the oils) can arise
purulent disease of a skin and its appendages.
Microflora of an oral cavity
In an oral cavity there is a plenty of microorganisms. More
than 100 species of aerobic and anaerobic bacteria are
described. In 1 ml of a spit can be found about 100 million
of microbial cells. Constant(stationary) temperature (37
0С), humidity, the oddments of food, alkaline reaction of a
spit and wide aeration promote reproduction of microbes.
The basic group of bacteria of an oral cavity is
compounded by streptococci (S.salivarius, S.mitis,
S.mutans, S.haemolyticus, S.viridans). Here permanently
dwell
Lactobacterium,
Veilonella,
Neisseria,
Corynebacterium, Bacteroides. Besides in an oral cavity we
meet H.influenzae, T.oralis, T.denticola, T.pseudopallida,
C.albicans, Leptospira, Actinimycetes, Mycoplasma,
Protozoa.
Among the transitional inhabitants of an oral cavity are
described Enterobacteriaceae (Escherichia, Enterobacter,
Citrobacter, Klebsiella, Proteus). We meet P.aeruginosa,
Bacillus, Clostridium less often. The presence E.coli in
composition of a stomatic microflora (especially at presence
of tooth prostheses) testifies to a unsuccessful status of an
oral cavity.
The main mass of microbes (70 %) is in a debris. In 1 mg
of dry mass of scurf can be about 250 million of bacteria.
The main part in maintenance of constant(stationary)
quantitative and quality composition play lysozim
(muramidase), lactoferrin, peroxidase, nuclease, secretory
IgA.
The opportunistic pathogenic bacteria of an oral cavity can
cause an endogenic infection. This is promoted by traumas,
change of pH spit, application of antibiotics. The large
value there is also sensibilization of an organism to
microbial allergens. Main causative agents of a caries are
S.mutans and S.sanguis.
Microflora of a stomach and intestine
At birth a gastrointestinal path and feces of the child are
sterile. In three - four days there is an intensive invading
them by bacteria of genus Escherichia, Proteus, Veilonella,
Lactobacterium, Enterococcus, Staphylococcus. However,
by the end of the first week putrefacient bacteria are
superseded by a lactate microflora. It mainly
Bifidobacterium bifidum, B. longum, B. infantis,
Lactobacillus acidophilus are. They are a main microflora of
the child at nursing. At artificial feeding or at transition to
the mixed feeding there is an increase of the putrifactive
microorganisms. Bifidobacterium and Lactobacterium play
the large role in decomposition of mammary milk, help the
process of digestion.
This microflora has strong antagonistic properties. It is
very useful to the child, oppresses development of
putrefacient bacteria, depresses and removes from an
organism pathogenic and conditional - pathogenic
microorganism.
After the ending of nursing in the child constant biozenose
of an intestinal path is gradually formed. The quality and
quantitative composition of a microflora of different
departments of an intestine becomes unequal. But a
prevailing
position
in
a
gastrointestinal
path
Bifidobacterium, Bacteroides, Clostridium occupy.
Stomach of the adult people contains few microbes. The
bactericidal action of an acidic gastric juice of the healthy
man (pH=2.0) is very strongly expressed. It is a very
strong barrier on paths of infiltration pathogenic and
opportunistic pathogenic bacteria in an intestine. In
connection with acidic response of the environment in a
stomach the specific microflora has got accustomed:
Yeast, Sarcina, Fungi, Lactobacterium, Staphylococcus,
Campylobacter (all up to 30 species). However,
putrefacient bacteria are absent. The total number of
bacteria does not exceed 103 cells in 1 ml. The change of
composition of a microflora, in particular appearance of
putrefacient microbes testifies to violation of the normal
function of a stomach secretion.
In a small bowel, especially in its upper department, are
even less bacteria (102 - 103 cells/1 ml). The microflora
here is not abundant and rather uniform: Lactobacterium,
Bifidobacterium, Enterococcus, E.coli and others. The
reproduction of bacteria delays action of bile, secret
mucous, immunoglobulins of the class IgA. In a number of
cases (lowering of a stomach secretion, disease of a liver,
radiative
irradiating,
the
development
of
an
immunodeficiency) in people a syndrome of exuberant
colonization of a small intestine reduce. The number of
bacterial populations similarly to a microflora of a large
intestine is sharply enlarged. It can result in various
violations of the function of a small intestine. The enteral
insufficiency can develop.
Bifidobacterium
The microflora of a large intestine is most abundant and
is diverse. Here there are most favourable conditions for
reproduction
of
many
microorganisms.
Now
microbiologists have detected and have described more
than 270 species of bacteria. Their common biomass
compounds about 1,5 kg. During day the man with feces
discharges of 17-18 billions microbes.
Microflora of a large intestine is divided into 4 groups:
1.
The main mass is compounded by strict asporous
anaerobes: Bifidobacterium and Bacteroides. On a part of
these bacteria it is necessary 96-99 % of all microflora of a
large intestine.
2.
Facultative anaerobes are: E.coli, Enterococcus,
Lactobacillus. On their part it is necessary 1-4 % of all
microflora.
3.
The third group is compounded by a residual
microflora (0,01-0,001 %). To it belong Staphylococcus,
Proteus, Candida, Pseudomonas, Clostridium.
4.
Representatives of the family Enterobacteriaceae,
which can temporarily or permanently be found out in an
intestine and cause intestinal infection (Enterobacter,
Salmonella, Shigella and others).
Normal Flora of the Respiratory Tract.
The nares (nostrils) are always heavily colonized, predominantly
with S. epidermidis and corynebacteria, and often (about 20% of
the general population) with S/ aureus, this being the main carrier
site of this important pathogen. The healthy sinuses, in contrast
are sterile. A large number of bacterial species colonize the upper
respiratory tract (nasopharynx) and includes predominantly nonhemolytic and alpha-hemolytic streptococci and Neisseria
species and sometimes pathogens such as S. pneumoniae,
Haemophilus influenzae, and Neisseria meningitidis.
Constantly, but in smaller quantity here we find nonpathogenic
representatives: Corynebacterium, Neisseria, Staphylococcus,
Bacteroides, Branhamella, Veilonella, Actinomyces. On tonsils
there are: Streptococcus, Staphylococcus, Pseudomonas,
Treponema, Klebsiella. In a larynx, the trachea and large
bronchuses there are few of microbes.
The lower respiratory tract (trachea, bronchi, and
pulmonary tissues) is virtually free of microorganisms,
mainly because of the efficient cleansing action of the
ciliated epithelium which lines the tract. Any bacteria
reaching the lower respiratory tract are swept upward by the
action of the mucociliary blanket that lines the bronchi, to
be removed subsequently by coughing, sneezing,
swallowing, etc. If the respiratory tract epithelium becomes
damaged, as in bronchitis or viral pneumonia, the individual
may become susceptible to infection by pathogens
descending from the nasopharynx (e.g. H. influenzae or S.
pneumoniae).
Microflora of an eye
The tears perniciously affect on microbes. In 47 % of
people the microflora here is completely absent. Only few
species have adapted to existence on a conjunctiva:
Corynebacterium, Neisseria, Staphylococcus, Mycoplasma,
Adenovirus, Herpervirus. About 5 % of people are carries
of S.aureus.
Microflora of genitourinary organs
In the healthy man the nephros, the ureters and urine in
urinary bladder are sterile. In an outside part of a urethra
Peptococcus,
Corynebacterium,
Mycobacterium
smaegme, Fusobacterium. Staphylococcus, Mycoplasma
are found.
Is more abundant and important is the microflora
of female generative organs for medical practice, and
especially vaginas. It characteristicly varies depending on
stages of a puberty. The first microorganisms of a vagina
come up in the girls in 24 hours after birth. During the
first month Lactobacterium (L. acidophilum, L.casei,
L.fermentum) prevail.
In the subsequent 10 years the bacteria in a vagina of the
girls practically are not found out. The cavity of the uterus
in them, as well as in the adult women, also is sterile. The
period of a menses contents of a vagina becomes alkaline. It
favours to development of a coccal microflora. During
sexual life in a vagina there are many microbes which have
been brought in from the outside. A microflora of a vagina
strongly varies at ginecological diseases and after abortions.
In a vagina of the puberal women Lactobacterium
acidophilum prevail, designated as Doderlein bacillus.
Thus, S.aureus, S. epidermidis, viridans streptococci,
enterococci, peptostreptococci, neisseriae, corynebacteria,
some
actinomycetes,
members
of
the
family
Enterobacteriaceae, chlamydae, occasionally clostridia and
other anaerobic rods, mycoplasmata, C.albicans, T.vaginalis
may be isolated.
On content Doderlein bacillus and Comma variable, and also epithelial
cells we distinguish 4 degrees of cleanness of vagina secret:
The first degree - there are Doderlein bacilli, single cells of a plane
epithelium, a lot of a glycogen, little protein, alkaline reaction, there
are no leukocytes.
The second degree - there are Doderlein bacilli, Comma variable,
epithelial cells, there are no leukocytes, it is a lot of a glycogen, and no
protein, less alkaline reaction of a secret.
The third degree - Doderlein bacilli are absent, leukocytes and cocci
microflora appear there is not enough of glycogen, the protein is more.
The fourth degree - Doderlein bacillus and Comma variable are
absent, leukocytes, protein and cocci microflora are much. The first
and second degree are norm, third and fourth degree - pathology.
Before labors of the women with the third and fourth degree of
cleanness vaginal secret it is necessary to treat. During labors on
wound surface of a uterus coccal microflora can get and cause
endometrytis, and even a sepsis. Many parturient women perished
from labour sepsis before using antibiotics.
I
II
III
IV
Vaginal flora
Thus, skin and the mucosas are densely stocked with various species of
microorganisms. They form with an organism of the man the uniform
ecological system. The composition and status of a microflora depends on
a human organism. A microflora, especially large intestine, also
essentially influence on the man. Effect of a microflora on
macroorganism appear as follows:
1.
The microflora is the important factor of a natural resistance of
an organism. It displays antagonism on others, including the pathogenic
bacteria and interferes to their reproduction in an organism. Metchnikov
has put forward idea of the use of lactate products with the purpose of
suppression putrefacient of bacteria in an intestine and prolongation of
life of the man.
2.
The normal microflora stimulates development of an lymphoid
tissue and promotes development nonspecific and immune
responsiveness of the man.
3.
The microflora, especially large intestine, participates in
digestion, including a metabolism of cholesterol and cholic acids.
4.
The normal microflora provides the man with various
vitamins (В1, В2, В6, В12, Е, K, nicotinic, pantothenic and folacin
acid etc.). These vitamins provide the most part of need in them of an
organism.
5.
The microbes – antagonists provide colonizational resistance
of the defined biotopes of an organism. It does not admit the
development of stranger(extraneous) microbes, including pathogenic
and conditional-pathogenic.
However normal microflora brings not only advantage. Under certain
conditions, at lowering nonspecific and immune responsiveness, action
of ionizing radiation practically all its species, except for
Bifidobacterium, can become causative agents of various endogenic
infection. More often they cause purulent - inflammatory diseases:
angina, pharyngitis, meningitis, cystitis, cholecystitis, otitis, nephritis,
appendicitis, abscess, phlegmon, and even a sepsis.
After the intestinal diseases and especially after durable and
nonrational application of antibiotics dysbacterioses appear.
The dysbacteriosis is change of a quantitative relation and
composition of a normal microflora of an organism, mainly of it
intestine. Thus there is a decrease or disappearance of some
bacteria and sharp increase others, especially infrequent or not
characteristic for the given biotope of microorganisms. As a rule,
the quantity of an facultative- anaerobic microflora is enlarged. It
can be the Gram-negative rods, staphylococci, Candida albicans
and species Clostridium. More often resistant representatives are
the genus of Staphylococcus, Escherichia, Proteus are,
Pseudomonas and especially Candida albicans. It leads to
development of dysbacteriosis. The staphylococcal pneumonias,
sepsises, candidoses, colitises especially caused by Clostridium
difficile, are the most often and serious forms of dysbacterioses. To
treat dysbacterioses of an intestine and colitises we apply special
bacteritic preparatrions: colibacterin, bifidobacterin, lactobacterin,
bificol, bactisubtil. They contain the dried up clouds of alive
bacteria having strong antagonistic properties. These eubiotics
reduce a normal microflora of an intestine.
Dental caries for a long time is connected with the defect
of a normal microflora. In England the complex vaccine is
generated which passes approbation. It consists of antigens
Streptococcus mutans. However some strains of these
bacteria have antigens similar to antigens of heart and
nephroses. The application of such vaccines can cause
serious autoimmune disorders in an organism. It is
necessary to select for creation of a vaccine such antigens,
which would have maximal immunifacient properties and
are innoxious to the man.
The normal microflora under certain conditions can lead to
the development of urolithiasis, ulcer of stomach, and
duodenum
(Campylobacter),
rheumatic
disease,
dermatitises, allergy and even to malignant neoplasms.
Thus, the normal microflora at the defined situations may
become potentially pathogenic.
Whether the life of the man and animal without microbes is
possible? For a long time it is known, that in birds and
animals Arctic districts the microorganisms are very
seldom found. There were cases, when in an organism of
birds completely there was no microflora. In due time
Pasteur tried to output animal without microbes, but the
technical possibilities of that time did not allowed to decide
this problem. Now it can be made. During last decades new
special branch of biology successfully develops which
studies life of animals without microbes. This branch is
named gnotobiology (gnotobiotics). In experimental
laboratories the pigs, chickens, rats, mouse, guinea pigs
completely deprived of bacteria are obtained.
The animals without microbes (gnotobiotes) are
divided into some groups:
1.
Monobiotes - completely deprived of microbes;
2.
Dibiotes - animals infected by one species of
bacteria;
3.
Polybiotes – having two and more microbial
species in organism.
Raising laboratory animal
Gnotobiotes have involved attention of the scientists in
connection with necessity of more penetrating learning of a
role of a normal microflora in mechanisms of an infection
and immunodefence. It is found, that in gnotobiotes the
caecum enlarged, the lymphoid (immunocompetent)
system is weakly advanced. Such animals have smaller size
of blood, smaller volume of an internals organs reduced
water content in tissues.
The gnotobiotes allows more precisely to study a role of a
normal microflora in synthesis of vitamins and amino
acids, in creation inherent and artificial immunity. The
large value has gnotobiology in learning space, conditions
of life of the man and animals in space, in conditions of
durable flight of missiles on other planets.