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Principles of Disease and Epidemiology

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Title: Principles of Disease and Epidemiology


1
Principles of Disease and Epidemiology
  • Ch 14

2
Diseases and US
  • Pathogen a disease causing microbial growth or
    toxin.
  • Disease an abnormality in which the body or part
    is not properly adjusted. The body part is
    overcome by the microbe
  • Change in the state of health
  • Infection is the invasion and growth of a
    pathogen in the body

3
More words
  • Host Is an organism that shelters and supports
    the growth of pathogens.
  • Pathology scientific study of disease
  • Etiology cause of a disease
  • Pathogenesis development of disease
  • Is this a type of symbiosis?

4
Normal Microbiota
  • In some cases it is normal for microbes to be
    growing.

5
  • Most mammals germ free in utero, are colonized
    after birth.
  • Microbes that establish permanent colonies inside
    or on outside of the body without causing disease
    are called normal microbiota.
  • Transient microbiota are microbes that are stable
    for a time then disappear.

6
Symbiosis
  • With normal microbiota, usually both species
    benefit from this arrangement.
  • Normal microbiota can prevent infections, may
    make necessary vitamins in return for nutrients
    form the host. (is called..
  • Opportunistic microbes may cause disease under
    certain instances.
  • Probiotics are live microbes applied to or
    ingested into the body, intended to exert a
    beneficial effect.

7
Normal Microbiota on the Human Body
Table 14.1
8
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9
Skin
  • Propionibacterium acnes
  • Staphylococcus epidermidis
  • Staphylococcus aureus
  • Candida spp
  • Most microbes are transient on skin.
  • Why?

10
Eyes
  • Basically the same as that found on the skin.
  • Eyes have lysozyme, few nutrients, washing by
    tears.

11
Nose and throat
  • S. aureus
  • S. epidermides
  • Streptoccoccus pneumoniae
  • Haemophilus
  • Neisseria

12
Mouth
  • Streptoccoccus
  • Lactobacillus
  • Actinomyces
  • Bacteroides
  • Fusobacterium
  • Treponema
  • Cornebacterium
  • Candida
  • Over 200 species
  • Idea environment
  • Is a diverse environment.
  • How do we know what lives in the mouth?

13
Large intestine
  • Bacteroides
  • Fusobacterium
  • Lactobacillus
  • Enterococcus
  • Escherichia
  • Enterobacter
  • Proteus
  • Klebsiella
  • Shigella
  • Candida
  • Is essentially a chemostat
  • Has a large resident microbiota

14
Urogenital system
  • Staphylococcus epidermidis
  • Enterococcus
  • Lactobacillus
  • Pseudomonas
  • Klebsiella
  • Proteius
  • In urethra
  • Lactobacilli
  • Streptococcus
  • Staphylococcus
  • Bacteroides
  • Clostridium
  • Candida albicans
  • Trichomonas vaginalis
  • in vagina is acidic

15
Kochs postulates
  • Same pathogen must be present in every case of
    the disease
  • Pathogen must be isolated in pure culture
  • Pathogen isolated from pure culture must cause
    the same disease in a healthy, susceptible
    laboratory animal.
  • Pathogen must be isolated from this animal

16
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17
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18
Exceptions to Kochs postulates
  • Are modified to establish etiologies of diseases
    caused by viruses and fastidious bacteria, which
    cannot be grown on defined media.
  • Some diseases are caused by a variety of
    microbes.
  • Some diseases such as S. pyogenes can cause
    several different diseases.

19
  • Some diseases can only occur in one organism so
    we cannot run the full Kochs postulates.
  • Why?

20
Disease classification and codification
  • Vocab
  • Measurements
  • Recognition and patterns

21
  • Symptoms- change in body function
  • Diagnosis- identification
  • Sign- a measurable change
  • Syndrome- a specific group of symptoms or signs
    that always accompanies a specific disease.
  • Communicable diseases- transmitted directly or
    indirectly from one host to another.

22
  • Contagious disease- is easily spread from one
    person to another
  • No communicable diseases- are caused by microbes
    that normally grow outside the body and are not
    transmitted from one host to another
  • Clostridium tetani

23
Where, how bad and how much. Words to describe ID
  • Incidence- number of people contracting the
    disease
  • Prevalence- number of cases at a particular time
  • Frequency- is in terms of sporadic, endemic,
    epidemic and pandemic
  • Acute, chronic, subacute and latent
  • Herd immunity- is the presence of immunity in
    most of the population

24
  • Local infection- affects a small area of the body
  • Systemic infection- spread throughout the body
  • Bacteremia- bacteria in the blood
  • Septicemia- bacteria multiply in blood
  • Secondary infections- occur after a host is
    weakened from a primary infection
  • Subclinical- cannot be measured

25
Severity or Duration of a Disease
  • Acute disease Symptoms develop rapidly
  • Chronic disease Disease develops slowly
  • Subacute disease Symptoms between acute and
    chronic
  • Latent disease Disease with a period of no
    symptoms when the patient is inactive

26
Recognition and patterns of disease
  • Predisposing factors make the body more
    susceptible to disease they include
  • Gender
  • Climate
  • Age
  • Fatigue
  • Nutrition
  • Lifestyle
  • Drug treatments

27
What happens when a disease does occur?
  • Incubation period- is the time between the
    initial infection and the first appearance of
    signs and symptoms
  • Prodromal- period is the first mild signs and
    symptoms
  • Illness- is when the disease is at its height
  • Decline- signs and symptoms decline
  • Convalescence- time until the body returns to
    predisease state

28
The Stages of a Disease
Figure 14.5
29
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30
Spreading of Infection
  • Reservoir of infection provides pathogen with
    conditions for survival
  • Human carriers, asymptomatic or latent
  • Animal- zoonoses various routes
  • Nonliving Reservoirs water, fertilizer ect

31
Transmission of Disease
  • Contact transmission
  • Direct person to person transmission
  • Indirect contact transmission
  • Fomite a nonliving transfer (1 meter, soiled
    goods)
  • Droplet transmission over short distances
  • Vehicle transmission (water, food, air)
  • Vectors (mechanical or biological)

Transmission of Disease
32
Transmission of Disease
Figure 14.6a 8
33
Portals of entry and Exit
  • Pathogens have preferred portals of entry and
    exit.
  • Most common portals
  • Respiratory tract
  • Gastrointestinal tract
  • Urogenital tract
  • Blood to blood

34
Transmission of Disease
  • Vehicle Transmission by an inanimate
    reservoir (food, water)
  • Vectors Arthropods, especially fleas, ticks,
    and mosquitoes
  • Mechanical Arthropod carries pathogen on feet
  • Biological Pathogen reproduces in vector

35
Nosocomial (Hospital-acquired) infections
  • 5-15 get infections while in the hospital.
  • Microbes in hospital
  • Chain of transmission
  • Compromised host
  • Is a hospital the best place to be if you are
    sick?

36
Nosocomial (Hospital-Acquired) Infections
  • Are acquired as a result of a hospital stay
  • 5-15 of all hospital patients acquire nosocomial
    infections

Figure 14.7, 9
37
Nosocomial Infections
ANIMATION Nosocomial Infections Overview
Table 14.5
38
Common Causes of Nosocomial Infections
Percentage of Total Infections Percentage Resistant to Antibiotics
Coagulase-negative staphylococci 25 89
S. aureus 16 80
Enterococcus 10 29
Gram-negative rods 23 5-32
C. difficile 13 None
39
MRSA
  • USA100 92 of health care strains
  • USA300 89 of community-acquired strains

Clinical Focus, p. 422
40
Which Procedure Increases the Likelihood of
Infection Most?
ANIMATION Nosocomial Infections Prevention
Clinical Focus, p. 422
41
Control of Nosocomial
  • Aseptic techniques
  • Hand washing (40 compliance)
  • Infection control staff

42
Emerging Infectious diseases
  • Ones that are new or changing
  • Global warming
  • Global transportation
  • Antibiotics
  • Breakdown in social order
  • Governance problems
  • Pesticides
  • Lack of vaccination
  • Lack of reporting

43
Epidemiology
  • Study of transmission incidence and frequency of
    disease.
  • Data are collected and analyzed in descriptive
    epidemiology
  • Analytical epidemiology- infected comp to
    uninfected
  • Controlled experiments
  • Case reporting
  • CDC reporting

44
  • CDC (Centers for Disease Control and Prevention)
    main source of epidemiologic info in US
  • Publishes Morbidity and Mortality Weekly Report,
    reports incidence and deaths.

45
Centers for Disease Control and Prevention (CDC)
  • Collects and analyzes epidemiological information
    in the U.S.
  • Publishes Morbidity and Mortality Weekly Report
    (MMWR) www.cdc.gov
  • Morbidity incidence of a specific notifiable
    disease
  • Mortality deaths from notifiable diseases
  • Morbidity rate number of people affected/total
    population in a given time period
  • Mortality rate - number of deaths from a
    disease/total population in a given time

46
Epidemiology
  • The study of where and when diseases occur

Figure 14.11
47
New fields of Biological study
  • Biological crimes? ASM paper

48
Nosocomial outbreak (page 445)
  • 7 year period 361 patients developed bacteremia
  • Burkholderia cepacia identified (same strain)
  • Infection within 36hr of IV
  • Disappears hrs after IV removed
  • Cleaning insertion site
  • Iodine is negative

49
Continued
  • Not found in povidone-iodine
  • In alcohol
  • Alcohol purchase as 90 and diluted in pharmacy.
  • Used the same 100l container
  • Used the same tap water
  • Tap water contaminated

50
  • How do you prevent this from happening?
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