Microbiology 11- Lecture: Medical Microbiology

1st Semester 22'-23'

scope of Medical micriobiology

1. sudiscipline of mcb
2. branch of medicine
3. clinical MCB

Neisseriae gonorrhoeae

gonococcus

➔ is the causative agent of gonorrhea
➔ one of the sexually transmitted diseases or STD

Acinetobacter baumannii

➔ an opportunistic pathogen
➔ (affecting immunocompromised individuals) that is
more and more associated with some hospitalacquired
infections (or nosocomial infections)

Methicillin-resistant Staphylococcus aureus (MRSA)

➔ responsible for some difficult-to-treat infections
because of its acquired resistance to a number of
antibiotics.

Burkholderia cepacia

➔ can cause pneumonia and other diseases in
immunocompromised individual with an underlying
lung disease (e.g. cystic fibrosis)

Pseudomonas aeruginosa

➔ is the most commonly isolated opportunistic
pathogen in patients hospitalized for more than 1
week.
➔ It can cause nosocomial infections like pneumonia,
bacteremia and urinary tract infections (UTI).

Sars-cov-2

➔ Severe Acute Respiratory Syndrome-Corona virus-2
➔ Causative agent of the COVID-19 (Coronavirus
Disease-19) pandemic.
➔ is a new type or variant of coronavirus which can
infect the upper and lower respiratory tracts.
➔ Many of the severe complications (septic shock, heart
and liver problems, and death) have been associated
with the flooding of the bloodstream with
inflammatory proteins called cytokines (―

Ebola virus

➔ Can cause a type of a rare but deadly hemorrhagic
fever (mortality rate can be as high as 90%)
➔ can damage the immune system and other organs,
and eventually cause a reduction in the level of blood
clotting cells

candida albicans

yeast-like fungus which is responsible
for many cases of candidiasis or thrush

Dermatophytes

three genera of molds

Microsporum
spp., Epidermophyton spp. and Trichophyton spp

Dermatophytes

superficial infections called

dermatophytoses

not debilitating or life-threatening

most prevalent and
persistent infections in the world

Entamoeba histolytica

amoebic
dysentery or amoebiasis.

Trypanosoma brucei

African trypanosomiasis or African sleeping
sickness

Trypanosoma brucei

a flagellated, tsetse fly-borne protozoan

Leishmania donovani

human blood
parasite and is the agent of leishmaniasis

Trichomonas vaginalis

agent of trichomoniasis, a
sexually transmitted infection.

Giardia (lamblia) intestinalis,

giardiasis

Plasmodium vivax

malaria.

Toxoplasma gondii

toxoplasmosis

Balantidium coli

only ciliated protozoan parasite of humans

Balantidium coli

(or balantidiosis)
which affects the large intestine

Pseudomonas aeruginosa

most commonly isolated opportunistic
pathogen

concern of medical micriobiology

1. pathogenesis
2. epidemiology
3. diagnistic procedures from assay
4. treatment

pathogenesis

process of disease development

1. epidemiology

indicence distribution, effect on the population

allied fields of MCB

epidemiology

Public health

Immunology

epidemiology

―population medicine‖.

independent form others, stand alone science

why is epidemiology the corner stone of pub health

serves as the cornerstone of public health because it provides data and information for the making of evidence-based policy decisions and for the development of interventions in the interest of public health and preventive medicine

Public health

➔ refers to the health of a population as a whole or to the activities of public health authorities in the control of disease
➔ ms to promote, protect and improve the health of communities and populations, whether big or small.
➔ made possible by promoting healthy lifestyles, conducting research on the disease, and

immunology

defined as a broad branch of biomedical science (an intermarriage of biology and medicine) which deals with the immune system, immunity (or the body‘s response to infection and its way of preventing and recovering from disease), and the various immunologic techniques or assays used

pathogen

its broadest sense, a pathogen is any biological agent that can produce disease in its host.

another term for pathogen

microbial parasite or an infectious agent.

disease

➔ This is a state in which a part or all of the body is not properly adjusted or is not capable of carrying out its normal function.
➔ It may be brought about by a microbial pathogen or not.

infection

➔ should not be confused with ―disease
➔ Actually the presence or growth and multiplication of a microorganism in or on the body
➔ does not, however, necessarily imply the production of disease. Our body is not sterile; we are normally infected and colonized by trillions or more of microbes in some parts of the body and yet we do not become ill, except under certain cases such as when we are immunocompromised.

infectious diseases

are contagious or transmissible are called communicable diseases. Those which are not, like tetanus, are non-communicable.

spordaic

when the disease occurs only occasionally (not frequently nor regularly) in a particular area or population.
➔ Examples of diseases which occur sporadically are plague and tetanus

endemic

constantly present in a specified population or geographical area
➔ endemic level is also the usual prevalence of that disease or its agent in the same population
➔ Examples of diseases which are endemic in the Philippines are dengue and leptospirosis

epidemic

however, does not necessarily apply only to infectious diseases
➔ also refer to noninfectious diseases such as diabetes and obesity.
➔ epidemic‖ proportion when the amount of the
➔ disease in a region or area rises, often suddenly and affecting a large number of people, above what is normally expected to occur. Examples of diseases which often become epidemics in certain areas, especially in the Philippines, are measles, cholera and dengue.

outbreak

➔ though similar to an epidemic, is when the cases of the disease are confined to only a smaller area.

pandemic

➔ if it has spread through multiple countries or continents such as our experience with COVID-19 which is due to infection with SARS-CoV-2.

infectios diseases can be classified according to time scale

acute

chronic

subacute

\

subacute

It is one which is of longer duration than an acute disease and is with less rapid change

chronic

It develops slowly, lasts much longer or may even have an indefinite duration.
➔ It is also one where there is virtually no observable change

acute

it develops suddenly, progresses rapidly and
➔ lasts only for a short while. It also usually requires immediate management.

zoonotic disease

Some diseases in humans are due to infectious agents which have infected animals first but which have been

transmitted to man. Such are called ―zoonotic‖ diseases or zoonoses.

ability of an organism to inflict damage on its host and cause disease

virulence

is often associated with the ability of the pathogen to multiply in the host, produce toxins or some other factors.

virulence

measure of the degree of pathogenicity

interaction of host and pathogen

complex and dynamic

3 factors that affects interaction of host and pathogen

1. virulence/ pathogenicity
2. susceptibility/ resistibility
3. environmental factors

virulence factors

1. attatching to host
2. avoid immune system
3. get nutrients

colonize

\
helps maintain disease in host

Microbial virulence factors

Microbial toxins

Adhesins

capsule

enzymes

siderophores

Microbial toxins

INHIBIT PROTEIN SYNTHESIS

leads to necrosis and cell damagae

2 types of Microbial toxins

endo and exotoxin

Adhesins

attachment to the host

capsule

resistance to phagocytosis

enzymes

degrade host components like collagenase and phospholipase

siderophores

scavenge iron from the iron-containing proteins of the host

salmonella sp

typhoid

salmonelliosis

H antigen salmonella sp

in its flagellum

for attachment but also for phagocyte killing

endotoxin or the LPS layer of salmonella sp

fever

enterotoxins of salmonella sp

diarrhea

Vi capsule antigen

of salmonella sp

inhibits another host defense : complement binding and activation

pathogenesis

refers to the biological mechanism that leads to a
diseased state or the manner by which disease
develops.

pathogenesis

pathogen produces disease in
the host is referred to as

5 general stages of pathogenesis

I. Exposure of the host to the pathogen
II. Entry of the pathogen/Adherence to Host Skin or
Muucoso
III. Invasion
IV. Colonization and Growth
V. Tissue Damage/Disease

reservoir

The natural habitat in which a pathogen normally
grows and multiplies is called its reservoir

Stage 1: exposure to pathogen

modes of transmission

Direct transmission and inDirect transmission

Direct transmission

1. direct contact
2. droplet transmission
3. contact with the soil (etc.),
4. inoculation into skin or mucosa (or via the
parenteral route)
5. transplacental (vertical) transmission

indirect transmission

➔ may occur through vehicles (contaminated
food or water, etc.)
➔ vectors (biological or mechanical),

➔ the airborne route,
➔ contact with fomites (inanimate objects
contaminated with the infectious agent),
➔ through unclean hands and fingers.

Airborne transmission (INDIRECT)

liberation of droplet nuclei (aerosols) that remain
infectious when suspended in air for long
distances and period of time

Parenteral route eg by injection

inoculation into skin or mucosa

➔ achieved through injection, cuts, bites, punctures,
surgery, etc
➔ intramuscular, subcutaneous, intravenous
intradermal.
➔ Unclean/non-sterile injection materials can
transmit pathogens through the parenteral route

\

Stage 2: entry of the pathogen

have different preferred entry point

pathogen attaches or adheres (via its molecules
called adhesins or ligands) to receptor molecules
on the surface of the host cell.

invasion

process where pathogen penetrates through the host’s epithelium and initiates pathogenicity through virulence factors like degenerative enyzmes and capsules

how does capsule promote invasion

resist phagocytosis

phagocyte cannot attach to the capsule

immune system

responsible for immune responses and protection against foreign agents including microbial pathogens, is the immune system
➔ a complex network of special cells, proteins, lymphoid tissues and organs, lymphatic vessels and fluids lymph and blood) which protects the body from infectious agents and other harmful substances

main components

immune system

1. thymus gland
2. bone marrow,
3. spleen,
4. tonsils
5. white blood cells,
6. lymph nodes and
7. the lymphatic system

1. thymus gland
2. bone marrow,

production and differentiation of T and B lymphocytes and thee rest captures and processes antigens

lymph

other type of fluid circulating in the body which is similar to blood plasma but does not contain red blood cells

lymphatic vessels

Lymph bathes tissues and carries with it bacteria and other antigens found in such tissues, for eventual capture in the spleen, lymph nodes, etc.

degrative enzymes

it breaks down hyaluronan or hyaluronic acid, a
polysaccharide which acts like a cementing‘
substance between cells, thus, facilitating the
invasive spread of the microorganism

Our body‘s main defenses consist of two types

Innate Immunity and Acquired Immunity.

Stage 4 colonization and growth

multiplies and may further spread (through the
blood and lymph) to other sites in the body
through invasion

Stage 4 colonization and growth

in this stage the presence of appropriate nutrients and environment in the host are critical in this stage.

kinds of damagae to host cells

direct damage, toxicity or
hypersensitivity

immune system

responsible for immune responses and protection against foreign agents including microbial pathogens, is the immune system
➔ a complex network of special cells, proteins, lymphoid tissues and organs, lymphatic vessels and fluids lymph and blood) which protects the body from infectious agents and other harmful substances

innate immunity

nonspecific defense mechanisms

acquired immunity

specific defense mechanisms (immune system)

First line of defense in innate

1. skin
2. mucous memrbanes
3. secretion of skin and mucous m

second line of defense in innate

inflammatory reposnse

WBC

anitmicrobial proteins

immunologic resposnes such as phagocytosis

fever

third line of defense in acquired

lymphocytes (ba nd t cells) and antibodies

Innate immunity

natural or non-adaptive immunity or

general resistance

\
because anything identified as foreign or non-self is a target of the innate immune response

Acquired or adaptive immunity

it targets specific microorganisms or antigens
➔ acquired after exposure to a specific infectious agent.

recogniation of teh adaptive immunity

seld, non self and tolerance to self antigens

acquired or adaptive immunity

type of immunity which retains a ―memory‖ (immunologic memory,

The body’s normal microflora

Part of the human body‘s innate defenses is the collection of microorganisms

harmless in their regular location and in the absence of coincident abnormalities such as immunodeficiency.

Normal microflora’s beneficial functions

1. Act as a protective barrier against infection with
invading pathogens by interfering with pathogen
adherence and colonization, by competing for
space and receptor sites on the host, and by the
production of inhibitory substances
2. Aid in the metabolism of food and absorption of
nutrients
3. Synthesis of essential vitamins (Vitamin K,
thiamine, pyridoxine, etc.) and other growth
factors

Process of phagocytosis

1. Chemotaxis of a phagocytic cell to the site of infection
and adherence of the microorganism to the
phagocyte
2. Ingestion of the microbe by the phagocyte
3. Formation of a phagocytic vacuole called phagosome
4. Fusion of the phagosome with a lysosome (contains
hydrolytic enzymes, etc.) forming a digestive vacuole
called phagolysosome
5. Digestion of the ingested microbe by enzymes
6. Formation of a residual body containing indigestible
material
7. Egestion or discharge of most of the digested cell and
other waste materials from the phagocyte

Inflammation

one of the body‘s fundamental responses to
injury and infection

characterized by pain (―dolor‖), heat (―calor‖),
redness (―rubor‖) and swelling (―tumor‖).

purpose of infalmmation

limit/contain the site of infection, damage or
injury
2\. localize the immune response
3\. restore tissue function