1. Chapter 14 202 Infection, Infectious Diseases and Epidemiology
Infectious dose (ID) is the minimum number of pathogen that can initiate an infection.

2. ID Diseases 1 Rickettsia, rabies 10 Tuberculosis 1,000 Gonorrhea 10,000 Typhoid fever 1 billion Cholera

3. 202 Symbiosis Commensalism and satellitism Mutualism Parasitism
Synergism:
Antagonism:

4. 203
Normal microbiota (normal flora, indigenous flora, normal microflora or commensals):
Benefits of Normal Flora:
They serve as antigens to stimulate our immune system to produce antibodies.
They produce B vitamins and vitamin K.
They prevent the establishment of pathogens by competition for food and space.
They may produce metabolites or antibiotics that kill or inhibit the growth of pathogens.

5. 203 Microbiota of the Mouth:
The oral cavity contains Streptococcus sanguis and S. mutans. They break down sucrose into glucose and fructose. The glucose molecules are linked together to form glucan. This sticky substance attracts other bacteria. The bacteria produce acids which corrode the teeth, causing dental caries. Colonization of anaerobes in the crevice leads to periodontal infections.

6. The normal flora found in human anatomic sites.

7. 203-204 Opportunists: Resident population: Transient population:
Reservoir:
living and non-living
Zoonoses:

8. 204 Asymptomatic carriers: Incubatory carriers: Convalescent carriers:
Chronic carriers:
Passive carriers:

9. 205 Portal of Entry: Skin: Mucus membranes: Placenta:
Parenteral route:

10. 205 The Roles of Adhesion in Infection:
Adhesion is a process of attachment.
Ligands:
adhesins: bacteria
attachment proteins: viruses
Some bacteria form a sticky web of bacteria and polysaccharides called a biofilm to adhere to the host surface. Example: plaque

11. The adhesion of pathogens to host cells
Figure 14.5

12. Dental Plaque
Figure 14.6

13. 206 Signs are observable evidence of a disease.
Symptoms are abnormalities of a disease which can be observed and measured.
Syndrome is a group of signs and symptoms that occur together and characterize a particular abnormality.
Etiology:

15. 206 Edema: Abscesses: Lymphadenitis: swollen lymph nodes Macule:
Papule:
Nodule: thicker papule
Vesicle:
Bulla: large-fluid filled blister
Pustule:

16. 206 Crust: dried exudate Erosion or ulceration: Ulcer: deep open sore
Chancre: erosive lesion in syphilis
Eschar: erosive lesion in anthrax
Erythema: confluent reddening of skin
Purpura: brown to purple discoloration
Leukocytosis:
Leukopenia:

17. 206 Septicemia: Bacteremia: Viremia:
Asymptomatic or inapparent infection:
Subclinical infection:

18. 207 Virulence: degree of pathogenicity
Pathogenicity: ability to cause disease
Class 1: non-pathogenic:
Sarcina lutea,
Bacillus thuringiensis
Class 2: moderately pathogenic:
Staphylococcus aureus

19. 207 Class 3: highly pathogenic: Mycobacterium tuberculosis
Class 4: extremely pathogenic:
rabies and Ebola
True pathogen:
Opportunistic pathogens

20. 208 Extracellular Enzymes:
Mucinase: digests the protective coating on mucous membranes.
Keratinase: digests skin and hair
Collagenase: digests the connective tissue
Hyaluronidase: digests hyaluronic acid which is the ground substance that cements animal cells together. It is also known as the spreading factor.

21. 208 Coagulase: causes coagulation
Bacterial kinases: digests fibrin clots
Streptokinase is produced by Streptococcus. Streptase is used to dissolve blood clots in patients with thrombi and emboli.
Staphylokinase is produced by Staphylococcus.

22. 208 Bacterial Toxins: Toxigenicity: the power to produce toxins.
Toxinoses: diseases caused by toxins.
Toxemia: presence of toxin in the blood.
Intoxication: poisoning caused by ingestion
of toxins.
Neurotoxins:
Enterotoxins:
Hemotoxins:
Nephrotoxins:

23. 208 Exotoxins Endotoxins Toxins are secreted; 1. not secreted;
can be found in the cannot be found in
medium the medium
Highly toxic weakly toxic
Highly antigenic 3. weakly antigenic
Protein in nature 4. lipopolysaccharides

24. 208 Exotoxins Endotoxins Heat labile 5. heat stable
Can form toxoid No
Cause minimal cause pronounced febrile reaction febrile reaction
Show specific No
tissue affinity
Secreted by G secreted by G-
& G- bacteria bacteria

25. 209 Bacteria that produce exotoxins:
Shigella dysenteriae (bacillary dysentery)
Vibrio cholerae (cholera)
Corynebacterium diphtheriae
(diphtheria)
Clostridium perfringens (gas gangrene )
Clostridium tetani (tetanus)
Staphylococcus aureus (food poisoning)

26. 209 Bacteria that produce endotoxins: Brucella abortus (brucellosis)
Salmonella (salmonellosis)
Incubation period:

27. 209 Hemolysins: Streptolysins: Antiphagocytic Factors: Capsules
M proteins on cell walls
Fimbriae
Leukocidins

28. 209 Stages of Infectious Diseases: Incubation period Prodromal stage
Period of invasion
Decline
Convalescent period or Terminal

29. Portal of Exit:
Respiratory and Salivary Portals
Skin Scales
Fecal Exit
Urogenital Tract
Blood

30. 210 Contact Transmission: Direct contact Indirect contact Droplet
Vehicle
Airborne transmission
Waterborne transmission
Foodborne transmisstion

31. 210 Horizontal transmission: Vertical transmission: Vector:
Biological vector
Mechanical vector

32. Fig

33. 210-211 Acute disease: Subacute disease: Latent disease:
Localized infection:
Systemic infection:
Focal infection:
Toxemia:

34. 211 Mixed infection: Primary infection: Secondary infection:
Communicable disease
Contagious disease:
Non-communicable disease

35. 211 Epidemiology: Surveillance: Reportable diseases:
Prevalence: total number
Incidence: new cases compared to a healthy population
Morbidity:
Mortality rate:

37. 212
Endemic disease: Sporadic disease: Epidemic disease: Pandemic disease:

38. Epidemiology of Infectious Diseases
Epidemiological Studies
1. Descriptive epidemiology
Careful tabulation of data concerning a disease
Record location and time of the cases of disease
Collect patient information
Try to identify the index case (or first case) of the disease

39. A map showing cholera deaths in a section of London
Figure 14.19

40. 212 2. Analytical epidemiology
Seeks to determine the probable cause, mode of transmission, and methods of prevention
Useful in situations when Koch’s postulates can’t be applied
Often retrospective
Investigation occurs after an outbreak has occurred

41. 213 3. Experimental epidemiology
Involves testing a hypothesis concerning the cause of a disease
Application of Koch’s postulates is experimental epidemiology

42. 213 Hospital Epidemiology: Nosocomial Infections
1. Appearance of antibiotic-resistant strains
because of prolonged use of broad-spectrum
antibiotics.
Increased use of immunosuppressive drugs
such as steroids, anti-cancer drugs and
irradiation.
3. Negligence of aseptic techniques.

43. The interplay of factors that result in nosocomial infections
Figure 14.20

44. 213
4. Tendency toward longer and more complicated surgical procedure resulting in longer exposure time of tissue during surgery.
5. Overcrowding and staff shortages in hospitals.

46. 213 Control of Nosocomial Infections: Surgical asepsis:
Medical asepsis:
Reverse isolation:

47. 214 Epidemiology and Public Health:
1. Sharing of data among public health
organizations
2. The role of public health agencies in
interrupting disease transmission:
monitoring water and food safety
3. Public health education: healthy choices
to limit diseases