Эпидемический процесс – это процесс возникновения и распространения специфических инфекционных состояний (от бессимптомного носительства до манифестных заболеваний) на видовом и популяционном уровнях, то есть процесс взаимодействия двух популяций – популяции паразита и популяции хозяина (популяции людей). На эпидемический процесс большое влияние оказывают социальные условия жизни населения и природные факторы. Наука, изучающая закономерности возникновения и распространения заболеваний различной этиологии среди населения с целью разработки профилактических мероприятий, называется эпидемиологией. Эпидемический процесс имеет разное проявление: - спорадическая заболеваемость – это низкий уровень заболеваемости данной инфекцией на данной территории в данный период (сезон) времени (единичные случаи заболеваний или групповые вспышки, не связанные между собой); - эпидемия – это такой уровень заболеваемости данной инфекцией на данной территории в конкретный отрезок времени, который в несколько раз превышает уровень спорадической заболеваемости, прогрессирует по времени и имеет тенденцию к пространственному распространению; - пандемия – это такой уровень заболеваемости данной инфекцией в конкретный отрезок времени, который не только резко превышает уровень обычных эпидемий, но и распространяется на территорию всей страны, территорию сопредельных государств, а иногда и многих стран. В эпидемическом процессе выделяют следующие элементы: источник инфекции, резервуар возбудителя инфекции, механизмы, пути и факторы передачи инфекции, восприимчивый организм. Источник инфекции – это организм человека или животного, в котором происходит размножение возбудителя, и от которого в дальнейшем заражается здоровый человек. От источника инфекции возбудитель проникает в организм здорового человека либо при непосредственном контакте, минуя фазу нахождения микроба во внешней среде, либо через объекты внешней среды и окружающие предметы. Основными источниками инфекции являются больной человек, больное животное, бактерионосители (люди, животные). Резервуар возбудителя инфекции – это объекты внешней среды, которые являются естественной средой обитания некоторых возбудителей заболеваний человека (возбудители столбняка, легионеллеза) и в которых возбудитель находит благоприятные условия для своего роста и размножения (накопления). Основными резервуарами инфекции являются почва и вода. При некоторых заболеваниях природным резервуаром возбудителя инфекции называют источник инфекции, обеспечивающий сохранение в природе возбудителя как вида. Например, для чумы суслики, сурки, песчанки являются не только источником инфекции, но и природным резервуаром возбудителя.

1. The normal
microflora of
various biotopes of
the human body.
Dysbacteriosis.
Statement and
analysis of results
on dysbacteriosis

2. What is Normal Flora?
•Normal flora are microorganisms, mostly bacteria
that continuously inhibited the human body. Under
normal conditions in a healthy human they are
harmless and may even be beneficial.
•Also called commensals i.e. organisms that dine
together.
• They can be either:
• Resident microflora - inhabit body sites for extended periods.
• Transient microflora - only temporary fond in a body site.

3. Normal Flora Definition
• Normal flora is the
mixture of
microorganisms
(bacteria and fungi)
that are regularly
found at any
anatomical site of
human body.

4. Relationships between Organisms
• Symbiosis - Permanent association between two different organisms.
• Neutralism - Two organisms living together, and neither is affected by that.
• Mutualism - Two organisms living together, and both benefit from that.
• Commensalism: Two organisms living together, one is benefited and the other is
not been affected.
• Parasitism: Two organisms living together, one is benefited ‘’called parasite’’ and
the other is harmed ‘’called host’’.
• Synergism: Sometimes, two (or more) microorganism may work together “team
up” to produce a disease that neither could cause by itself

6. Stuff about
Normal Flora
• New born baby born sterile
,they acquire the organisms
after born from environment.
Our internal organs are sterile
like the spleen, liver,
pancreas, bladder, CNS, blood
unless during infection.
Normal flora differ from one
human to another depending
on age, diet, and geographic
habitat.

7. Why Should We Know About Normal Flora?
We all should know about the types and
distribution of normal flora in our bodies because:
It gives us better understanding of the possible
infections that result from injury to a specific
body site. As well as the possible sources and
significance of microorganisms isolated from the
site of an infection.

8. In a healthy human, the internal tissues, e.g. blood, brain,
muscle, etc., are normally free of microorganisms. However, the
surface tissues, i.e., skin and mucous membranes, are constantly
in contact with environmental organisms and become readily
colonized by various microbial species. The mixture of
organisms regularly found at any anatomical site is referred to as
the normal flora. The normal flora of humans consists of a few
eucaryotic fungi and protists, but bacteria are the most numerous
and obvious microbial components of the normal flora. A
healthy foetus in utero is free from microorganisms. During
birth the infant in exposed to vaginal flora. Within a few hours
of birth oral and nasopharyngeal flora develops and in a day or
two resident flora of the lower intestine appears

9. Effects of breastfeeding vs. bottle-feeding on
indigenous microflora
• Large effect seen - breastfed infants develop primarily
Bifidobacterium populations, bottle-fed get a mixture of
various species of coliforms, Clostridium, Staphylococcus,
Streptococcus, Lactobacillus, etc. Breastfed infants have
lower pH and less buffering capacity in large intestine. This
disfavors enterobacteria and favors Bifidobacteria.
Bifidobacterium seem to compete with potential pathogens
like Clostridium difficile and some enterobacteria One study
demonstrated that bottle-fed infants were 4X as likely as
breastfed ones to harbor C. difficile.

10. Normal flora of specific regions
• Skin
• Oral cavity
• Gastrointestinal tract
• Other areas
• Upper respiratory tract
• Lower respiratory tract
• Urogenital tract
• Microorganisms are normally not found in the organs, blood, or
lymph. (if they are, you’re in trouble!)

11. Normal flora of the skin
• Skin surface is unfavorable habitat.
• Usually only populated by transient microbes
• Exceptions are moister areas: scalp, face, ears, underarms,
genitourinary, palms, toes.
• Most resident skin microorganisms inhabit deeper layers of the
epidermis, sweat glands, and follicles.
• Most of the residents are Gram-positives, especially Staphylococcus
and Propionibacterium

12. Normal flora of the mouth
A great place to live! (in contrast to the skin)
The only negatives: salivary enzymes (lysozyme and
lactoperoxidase), and constant need to re-attach
Initially (i.e. at birth), there are only a limited number of
bacterial types (aerotolerant anaerobes like
Lactobacillus and Streptococcus), then as teeth erupt
there are more anaerobes and bacteria adapted to living
in crevices and on smooth surfaces.

13. Microflora of the EYES
The conjunctiva of the eye has
primarily S. epidermidis, followed by S.
aureus, C. diphtheroids, and S. pneumoniae.
Some skin normal flora are also present but at
fewer amounts.
Tears (Lysozyme enzyme), mucus, and oil
will protect the conjunctiva of the eye from
colonization by more bacteria.

14. Microflora of the EARS
• The middle ear and inner ear:
are usually sterile.The outer
ear and the auditory canal:
contain the same normal flora
of the skin. When the person
coughs, sneezes, or blows his
nose, these microbes may
move into the middle ear
where they cause infection.

15. Gastrointestinal Tract
• Stomach: Only few bacteria are present in the stomach
due to gastric enzymes and acidic pH.
• Intestines: large intestine has more bacteria than the
small intestine. 99% of normal flora in the large
intestine are anaerobic Bacteroides spp.
• Most common Gram negatives: E.coli, Klebsiella spp.,
Proteus spp., Pseudomonas spp., and Enterobacter spp.

16. Urogenital Tract
•Vagina: Lactobacillus spp. keeps the pH acidic to
protect us from fungal infections caused by
Candida albicans which is a minor resident.
•Kidney and Bladder: are sterile.
•Lower Urethra: has the same normal flora
present in the skin outer layer.

18. Bismuth Sulfite Agar: Composition, Uses,
Colony Morphology
Bismuth Sulfite Agar (BS) is a selective as well as differential medium for
isolation and presumptive identification of Salmonella spp especially
Salmonella Typhi. Salmonella spp are the causative agent of various diseases
like gastroenteritis, sepsis, enteric fever. Salmonella can be isolated from
wide range of clinical, food, sewage and other environmental samples.
Bismuth sulfite agar is a modification of original Wilson and Blair Medium.
Ferrous sulfate is an indicator for hydrogen sulfide production, which occurs
when the H2S (hydrogen sulfide) produced by Salmonella reacts with the iron
salt. This reaction causes a black or green metallic colony and brown or black
precipitate whilst the reduction of bismuth ions to metallic bismuth produces
a metallic luster around of the colonies. Agar is the solidifying agent.

19. Result and interpretation:
The colony morphology of certain bacteria are illustrated as follows
Organism Appearance
Salmonella Typhi
Black `rabbit-eye’ colonies with a black zone and
metallic sheen surrounding the colony after 18 hours.
Uniformly black after 48 hours incubation Note: When
a heavy inoculum is used, S. Typhi appears light green
and could be misinterpreted as negative growth.
Salmonella Paratyphi A and Other Salmonella spp
Variable colony appearance after 18 hours, they may be
black, green or clear and mucoid. Uniformly black
colonies are seen after 48 hours, often with widespread
staining of the medium and a pronounced metallic
sheen
Other organisms like Coliform bacteria, Serratia,
Proteus
Usually inhibited but occasional strains give dull green
or brown colonies with no metallic sheen or staining of
the surrounding medium.

20. Phenylethyl Alcohol Agar: Composition,
Preparation, Uses
Phenylethyl alcohol agar (PEA) is a selective medium used to cultivate
Gram-positive organisms, particularly cocci, from a sample containing a
mixture of pathogens. The active ingredient, phenylethyl alcohol,
inhibits or markedly reduces the growth of Gram-negative organisms by
interfering with DNA synthesis. Staphylococcus aureus, a Gram-
positive organism, grows on PEA while Serratia marcescens, a Gram-
negative organism, does not.
Phenylethyl alcohol agar (PEA) may be prepared with and without 5%
sheep blood supplement. Five percent sheep blood is added to the base
medium to enhance the growth of anaerobic bacteria.

22. Colony Shape, Size of the bacterial
colony, Appearance of the colony
surface, Consistency/Texture, Color of
the colonies (pigmentation)
Elevation of the bacterial colony: It gives
information about, how much does the
colony rise above the agar. This describes
the “side view” of a colony. These are the
most common elevations; e.g. flat, raised,
umbonate (having a knobby protuberance),
crateriform, convex, pulvinate (cushion-
shaped).
Margin of bacterial colony: The margin or
edge of a colony may be an important
characteristic in identifying organisms.
Common examples are entire (smooth),
irregular, undulate (wavy), lobate, curled,
filiform, etc.

23. Opacity of the bacterial colony
Is the colony transparent (clear), opaque (not transparent or
clear), translucent (almost clear, but distorted vision–like
looking through frosted glass), or iridescent (changing colors in
reflected light)?

24. Coliforms are good indicator organisms. They are not generally pathogenic, their presence shows that faecal
contamination of water has occurred. Coliforms in the hygienic practice are defined as those facultative
anaerobic, Gram-negative, non–endospore-forming, rod-shaped bacteria that ferment lactose, produce acid and
gas within 48 hours at 37°C. Coliforms are
members of the family Enterobacteriaceae (e.g. E. coli, Enterobacter aerogenes, Klebsiella pneumoniae). The
values of coli-count and the coli-titer are used for the quantitative characterization of coliform organisms in a
sample.
Coli-titer is the smallest amount of water, from which coliform organisms can still be cultivated.
Coli-count (Coli-index) is the number of coliform bacteria that can be cultivated from 100 ml of water sample.
Streptococcus faecalis dies in water quickly, however its evaluation is important, since, as opposed to E. coli
(which can be found almost anywhere), S. faecalis does not reproduce in the nonfecal environment. Thus its
presence underlines the results of E. coli testing and indicates the fresh fecal contamination of water. Anaerobic
spore forming Clostridium welchii
stays viable in water for a long period of time, thus its presence in water indicates heavy and long-lasting
fecalcontamination of water.

25. B. MICROBIOLOGICAL EXAMINATION OF SURFACE
WATER; HYGIENIC CONTROL
B/1. COLI-COUNT DETERMINATION BY MEMBRANE
FILTER TECHNIQUE
A membrane filter with a 0.45μm pore-size is generally used to remove
bacteria from
solutions.
Exercise: Filter 100 ml of a water sample through a 150μm thick and
0.45μm pore-sized
sterile membrane filter. Remove the membrane filter and place it facing
up onto the surface of differential media (endo- or eosin-methylene blue
agar plates). Incubate the plates at 37°C for
24 hours and count the number of colonies formed. Knowing the
volume of water that has
been filtered, we can estimate the Coli-count of 100 ml water sample.
Sample: water sample (river water, well water)
Materials: graduated cylinder (to measure a 100 ml of water), 0,45μm
pore-size
membrane filter (for filtering tap water or natural water samples), sterile
filtering unit, Endo
agar Petri plates (LES Endo Agar) or Eosin-Methylene Blue agar plates
(EMB Agar), metal
forceps (use alcohol for flaming)

26. SOIL
sanitary indicative microorganisms:
- E.coli
- Str. Faecalis
- Cl. Perfringens
Sanitary indexes:
- TMN
- Perfringens – titer
- Coli index

27. WATER
sanitary indicative microorganisms:
- E.coli
Sanitary indexes:
- TMN
- Coli – titer
- Coli index

28. AIR
sanitary indicative microorganisms:
- S. aureus
- Hemolytical streptococci
Sanitary indexes:
- TMN