3.  Mutualism: Both members of the association
living together benefit from the relationship
 Parasitism: One organism, the parasite, benefits
from the relationship, whereas the other
organism, the host, is harmed by it (e.g. bacteria,
viruses, protozoa, fungi, helminths)
 Commensalism: Two species live together in a
relationship such that one benefits and the other
one neither benefits nor is harmed

4. Contamination: presence of microorganism
Infection: refers to the multiplication of any
parasitic organism within or on the host’s body
- a condition in which pathogenic microbes
penetrate host defenses, enter tissues & multiply

5. Disease: any deviation from health, disruption
of a tissue or organ caused by microbes or their
products
- A disturbance in the state of health
wherein the body cannot carry out all its
normal functions
Pathogenicity: the capacity of the organism
to produce disease
Virulence: refers to the intensity of the
disease produced by pathogens, and it varies
among different microbial species

6. Two categories of organisms can be distinguished:
f Resident microflora: comprise microbes that are
always present on or in the human body
 includes bacteria, fungi, protozoa, viruses and arthropods
 most areas of the body in contact with the outside
environment harbor resident microbes; large intestine has
the highest numbers of bacteria
 internal organs & tissues & fluids are microbe-free
 bacterial flora benefit host by preventing overgrowth of
harmful microbes

7. B. Transient microflora: microbes that can be
present under certain conditions in any of the
locations where resident microflora are found
- Acquired from mother’s womb
- Flora of the human skin
- Flora of the gastro-intestinal tract
- Flora of the respiratory tract
- Flora of the Genito-urinary tract

9. - aerobic and anaerobic diphtheroid bacilli
(Corynebacterium, Propionebacterium)
- nonhemolytic aerobic and anaerobic staphylococci (S.
epidermidis and other coagulase –negative staphylococci,
occasionally S. aureus and Peptostreptococcus species)
- Gram positive , aerobic sporeforming bacilli
- α-hemolytic strptococci (S. viridans)
- enterococci (Enterococcus species)
- gram negative coliform bacilli and Acinetobacter
- Fungi, yeasts in skin folds
- nonpathogenic mycobacteria in sebaceous secretions
(genetalia, external ear)
* AEROBES AND ANAEROBIC bacteria often join tor form
synergistic infections (gangrene, necrotizing fasciitis,
cellulitis)

10.  lactic acid streptococci and lactobacilli
Bifidobacterium species
 Enterobacteriaceae (Klebsiella, Citrobacter,
Enterobacter)
 Anaerobes: - Bacteriodes species (Bacteroides
fragilis, Fusobsacterium species
 Anaerobic lactobacilli – bifidobacteria, clostridia
(Clostridium perfringens)
 Anaerobic gram positive cocci – (Peptostreptococcus
species)
 Facultative aerobes – gram negative coliform
bacteria, enterococci, small number of protei,
psuedomonads, lactobacilli, candidae)

11. ( Protection - inhibit potential pathogens
indirectly by competing for nutrients and
receptors of production of antimicrobial factros
(bacteriocins, lactic acid)
a Development of mucosal immune system (induce
secretion of IgA, helps develop intestinal humoral
immune system, modulate local T-cell repsonses)
o Metabolic functions – produces short chain fatty
acid that control intestinal epithelial cell
differentiation, Synthesize Vit K, biotin, folate
and enhance absorption

12. - same microorganism as found in the skin and
perinium
- Group B streptococci – women and childbearing
stage
- α-hemolytic streptococci, anaerobic streptococci,
Prevotella species, clostridia, Gardnerella vaginalis,
Ureaplasma urealyticum)
- diphtheroids, S epidermidis, nonhemolytic
strptococci
- Neisseria and gram negative bacilli – checked by
flow of tears which contain antimicrobial lysozymes

14.  Microbial Antagonism: Normal flora inhibits
overgrowth of harmful microbes.
Mechanisms include competition for nutrients and
affecting environmental factors such as pH, toxic
substances, and oxygen availability.
 Vaginal flora maintains pH of 3.5-4.5 which inhibits
overgrowth of Candida albicans.
 In mouth streptococci produce compounds that inhibit
growth of many other cocci.
 In intestine E. coli produce bacteriocins, which inhibit
growth of closely related bacteria.
 C. dificile is inhibited by normal intestinal flora.

15. Opportunistic Pathogens: Organisms that
normally do not cause disease in their natural
habitat in a healthy person but may cause
disease if the host is weakened or if they
enter a different part of the body.
3. Failure of the host’s normal defenses
(immunocompromised)
4. Introduction of the organisms into unusual
body sites
5. Disturbances in the normal microflora
(microbial antagonism)

16.  Pneumocystis carinii pneumonia in AIDS patients.
 Tooth decay and gum disease caused by mouth
flora.
 Neisseria meningitidis is usually harmless in
respiratory tract, but can cause meningitis.
 E. coli can cause urinary tract infections,
meningitis, pneumonia, and abscesses.
True pathogens – capable of causing
disease in healthy persons with normal
immune defenses
 Influenza virus, plague bacillus, malarial protozoan

17. The effect of two microbes acting together, is greater
than the effect of either acting alone.
 AIDS and mycoplasma infection: Cells infected with
mycoplasma and HIV die more readily than those
infected with mycoplasma alone.
 AIDS and Oncogenic Viruses:
 Women with HIV infections develop very aggressive cervical
cancers which are caused by papillomavirus.
 Individuals with HIV and Human Herpes Virus 8 infections,
are more likely to develop Kaposi’s sarcoma.
 Oral streptococci and pathogens that cause
gingivitis and periodontal disease, the oathogens
bind to streptococci instead of host tissue.

18.  Primary Infection: Acute infection that causes
initial illness.
Example: Common cold
 Secondary Infection: Caused by opportunistic
pathogen after primary infection has weakened
host immune system.
Example: Pneumonia or bronchitis may develop
after the common cold.
 Subclinical Infection: Does not cause any
noticeable illness in host.
Example: Over 90% of polio infections are
asymptomatic.

19. Reservoirs of Infection
 Human Reservoirs: Infected individuals who may or
may not present disease. Carriers are infected
individuals without any signs or symptoms of disease
(AIDS, polio, gonorrhea).
 Animal Reservoirs: Zoonoses are diseases that occur
primarily in wild and domestic animals. About 150
different zoonoses are known (rabies, anthrax, and
Lyme disease).
 Nonliving Reservoirs: Two major sources are soil and
water.
 Soil: Clostridium tetani and botulinum.
 Water: Vibrio cholerae and Salmonella typhi.

21.  skin
 gastrointestinal tract
 respiratory tract
 urogenital tract
. Respiratory trace
. Urogenital tract
Pathogens during pregnancy and birth

22. I. Contact Transmission: Spread by direct contact,
indirect contact, or droplet transmission.
f Direct Contact Transmission: Person-to-person
transmission. No intermediate object is involved.
Examples: Touching, kissing, sexual intercourse.
B. Indirect Contact Transmission: Agent is transferred via a
nonliving object (fomite).
Examples: Towels, eating utensils, thermometers,
stethoscopes, bedding, clothes, money, and syringes.
C. Droplet Transmission: Microbes are spread in mucus
droplets that travel short distances (less than 1 meter).
Examples: Sneezing, coughing, talking, and laughing.

23. II. Vehicle Transmission: Transmission of disease via
medium such as water, food, air, blood, body fluids,
and intravenous fluids.
 Waterborne Transmission: Usually caused by water
contaminated with sewage.
 Airborne Transmission: Spread of agents by droplets in dust
that travel more than 1 m to host.
III. Vectors: Animals that carry disease from one host
to another. Arthropods (insects) are most important
animal vectors.
 Mechanical Transmission: Passive transport of pathogens on
insect’s body.
 Biological Transmission: Pathogen spends part of its life
cycle in the vector.

24. Portals of Exit
Site at which microbes leave body. Most common
exit portals are respiratory and gastrointestinal
tracts.
 Respiratory Tract: Exit in discharges (mucus
droplets) from nose and mouth. Transmission by
coughing, sneezing, spitting, etc.
 Examples: Tuberculosis, influenza, pneumonia, common
cold, measles, mumps, scarlet fever, and meningococcal
meningitis.
 Gastrointestinal Tract: Exit in feces or saliva.
 Feces: Amoebas, poliovirus, cholera, typhoid fever,
salmonella, shigella, and many helminths.
 Saliva: Rabies virus, herpes simplex 1.

25.  Urogenital Tract: Exit in secretions or urine.
 Penis and vagina: Sexually transmitted diseases.
Chlamydia, herpes simplex 2, HIV, gonorrhea, and
syphilis.
 Urine: Brucellosis and typhoid fever.
 Skin and Wound Infections: Spread through direct
contact or through fomites.
 Example: S. aureus, P. aeruginosa, scabies, ringworm.
 Blood: Transmission through insects, needles, and
syringes.
 Insects: Malaria, yellow fever, and Lyme disease.
 Needles: AIDS and hepatitis B.