Ph 162A Lec 14: Etiology, Diagnosis, And Prevention Of Infectious

Front 1

what is etiology?

Back 1

the cause of a disease in general, i.e. the cause of all cases of a particular disease in a population

Front 2

what is diagnosis?

Back 2

refers to identification of the disease in an individual case of a disease

Front 3

How do we determine the etiology of an infectious disease?

Back 3

the standard criteria used is called the Henle-Koch postulates (standard generalized form)

Front 4

What are the 4 postulates use in order to prove that a particular microorganism causes a particular disease:

**then name the problems/complications that conflict with these postulates

Back 4

1. The microorganism must be present in every case of the disease
**problem: a microorganism may be present, but you made not be able to detect it---> the iceberg concept comes to play where some people may carry organism w/o disease.

2. The microorganism must be isolated from the diseased host and grown in pure culture
**problem: many organisms cannot be grown in culture at all e.g viruses, some bacterial infections

3. The specific disease must be reproduced when a pure culture of the microorganism is inoculate into a healthy susceptible host
**problem: difficult b/c you may not find an appropriate animal model, and people are not exactly stepping out to take an inoculating shot

4. The microorganism must be recoverable once again from the experimentally infected host
**we must have the first 3 b/f we can recover the organism

Front 5

[Other modes of identification]
there are some other criteria that we can use now in order to be able to link a microorganism w/ a disease. These are based primarily on _______

Back 5

immunological reactions of the host

Front 6

[immunological rxn of the host] Evidence that a particular disease is causing a disease occurs when: (3 evidence)

Back 6

1. there is an increase in either cell-mediated or humoral immune response to the organism, after onset of disease e.g infectious mononucleosis

2. persons w/ no antibody or cell-mediated immune response to the organism are susceptible to the disease, and persons w/ a high antibody level or strong cell-mediated immune response to the organism, are resistant to the disease e.g infectious mononucleosis

3. The disease can be prevented by vaccination w/ a preparation of the organism or one w/ similar antigenic specificity

Front 7

[How do we determine the diagnosis of an infectious disease]

There are the 4 diagnosis:

Back 7

1. clinical diagnosis
2. physical diagnosis
3. differential diagnosis
4. etiologic diagnosis

Front 8

[1. clinical diagnosis]

what is clinical diagnosis?

Back 8

diagnosis made on the basis of symptoms, signs, and medical history

Front 9

define symptoms

Back 9

subjective evidence of disease stated by the patient, but which cannot be verified by another person

Front 10

[symptoms]

define malaise

Back 10

"not feeling good;" a feeling of general discomfort

Front 11

define chill

Back 11

a sensation of cold; usually occurs at the initial stage of an infectious disease

Front 12

define nausea

Back 12

an unpleasant sensation ("sick to the stomach") often leading to vomiting

Front 13

[signs]

define signs

Back 13

objective evidence of disease recognizable by another person

Front 14

lymphadenopathy

Back 14

enlargement of the lymph nodes

Front 15

rigor

Back 15

visible shivering as opposed to a mere feeling of cold

Front 16

vomiting

Back 16

forcible expulsion of stomach contents through the mouth

Front 17

diarrhea

Back 17

abnormal (increased) frequency and liquidity of fecal discharges

Front 18

cutaneous manifestations

Back 18

abnormal appearance of the skin

Front 19

[Types of cutaneous manifestations]

jaundice

Back 19

yellowish appearance of the skin, e.g hepatitis

Front 20

erythema

Back 20

redness of the skin; e.g scarlet fever

Front 21

cyanosis

Back 21

bluish appearance of the skin; e.g pneumonia

Front 22

pallor

Back 22

paleness of the skin

Front 23

vesicle

Back 23

watery blister; serum-containing skin lesion; e.g. cold sore

Front 24

pustule

Back 24

a pus-containing skin lesion; e.g. boil, abscess

Front 25

ulcer

Back 25

a skin w/ superficial loss of tissue; e.g yeast infections

Front 26

nodule

Back 26

a raised, swollen, solid skin lesion; e.g leprosy

Front 27

medical history

Back 27

record of patient's medical experiences and characteristics throughout life e.g. age, race, diseases, medications, diseases of family members

important to know these:
a. occupation
b. exposure to pets
c. underlying disease-- that can predispose somebody to an infectious disease
c. geographical areas of resistance and travel
e. exposure to others known to have an infectious disease

note: all of these are important to diagnosis a disease

Front 28

[2. Physical diagnosis]

what is physical diagnosis?

Back 28

diagnosis made on the basis of objective physical measurements

**this is when the doctor measure your pulse-- a pulse rate might be increased or elevated if you have an infection

Front 29

palpation

Back 29

examination by touching with the hands

Front 30

define fever

Back 30

a body temperature above 98 degrees F (37C); fever patterns may be helpful in distinguishing among different infectious diseases

Front 31

describe the pattern of these fever associated with the infectious disease

1. fever w/ Psittacosis
2. fever w/ Drain Pyogenic Abcess
3. Fever w/ influenza
4. Fever w/ Brucellosis
3. Fever

Back 31

1. sustained or continuous fever over a number of days
2. intermittent-- where you are spiking one day, down the next, spike one day etc. --might be a response to toxins production
3. remittent fevers
4.relapsing or recurring fever, where it comes and goes for as long as the infection continues, e.g. malaria and brucellosis

note: there is also diurnal variation where you have more fever in the evening than during the daytime

Front 32

[3. differential diagnosis]

define

Back 32

diagnosis which distinguishes a disease from others with which it might be confuse

Front 33

4. etiologic diagnosis

what is it?

Back 33

identification of a disease in terms of its cause or etiology; in the case of infectious disease, this refers to the laboratory identification to the microorganism that is the etiologic agent

Front 34

Why is etiologic diagnosis so important for infectious disease? (4 reasons)

Back 34

1. aside from signs and symptoms, you need to know what it is that you are treating
2. may give a clue about an underlying disease
**e.g if you have a chronic fungal disease, it may mean that the person might be diabetic etc..
3. may be important in controlling epidemics
4. if it is highly communicable, it is necessary to identify it so that people can be alerted to the organism and be on the lookout for it. **REQUIRE FOR REPORTED OR NOTIFIABLE DISEASE

Front 35

What kind of disease are reportable/notifiable? (3)

Back 35

1. almost all are infectious; most of the time they communicable
2. are reasonably severe
3. most are diseases that have promise of being controlled by public health measures

Front 36

How are disease reported?

Back 36

1. physician will use the Confidential Morbidity Report form and send it to their local public health department/county
2. county will put info into a database, which is sent to the state
3. state sends that info to the centers for disease control

Front 37

[Methods of Diagnosis]

How do we make these etiologic diagnoses? what are the methods we use in clinical laboratory to diagnose diseases? (name all 6)

Back 37

1. base on morphology
2. base biochemical properties
3. their sensitivity to lethal or growth inhibiting agents
4. molecular and immunologic probes
5. animal testing
6. tests the measure the host's immune response

Front 38

1. How is diagnosis of Morphology made?
--this method is mostly use for?

Back 38

**Primary method of diagnosis for protozoans, helminths, and anthropods b/c we can see them easily and they have characteristics very specific to the organism
**We test this by:
--fecal smear
--blood sample
--Gram stains

Front 39

2. on the basis of Biochemical Properties

**this method is mostly use for?
**What can we detect from this method?

Back 39

**This is mostly used for bacteria and yeasts
**using biochemical probes, we can measure diff.
a. intracellular reactions--> that tell us about the microbe's
METABOLIC PATHWAY
**using gram stain we can look at CELL WALL

b. can use use extracellular products to detect enzymes
**tools/method: agar plate, blood plate for organism to grow.
--blood plate you can get alpha hemolysis = this is where you have a dark olive green color on the colony due to partial hemolysis (destruction of RBC)

**Beta hemolysis = this is when the red blood cell is completely destroy and you see a clear zone around where the colony is.

Front 40

3. test for Sensitivity or resistance to various inhibiting agents

What is antibiotic disc sensitivity testing?

Back 40

You take your isolate and make a lawn of bacteria. You make a suspension and you smear it on the plate with what we refer to as a hockey stick. And then you drop your antibiotic discs in. There is chart you go by and you measure the distance from the edge of the perforated filter paper to the edge of the colony. This can vary because even though you may see a great amount of sensitivity in a certain area, it may be that this antibiotic is good enough but can only diffuse so much into the agar. **It shows how far the antibiotic can diffuse into the agar. (help us detect which microorganism we have)

Front 41

What is phage sensitivity testing?

Back 41

you drop a phage on a lawn of bacteria along with other phages, and you see clear zones. This means that wherever you dropped your phage, it killed that bacterium. With this you will know what type of bacteriophage it is b/c by see that it only kills one species of bacteria

Front 42

4. molecular and immunologic probes

What is a molecular probe?

Back 42

--a nucleic acid sequence complementary to the sequence of a microorganism and labeled w/ a marker substance for detection
**You apply this to your slide and tissue culture, and you wash it away. Only where you have formed a complementary bond do you find the organism.

Front 43

what is immunologic probe?

Back 43

a reagent antibody (an antibody made in the laboratory) which reacts specifically w/ a microorganism. The antibody is labeled w/ a marker substance for detection
**very specific
**made w/ IgG antibody

Front 44

[utility of molecular and immunologic probes]

Why do we use these two probes and what is their main use?

Back 44

**these two tests (molecular and immunologic probes) are rapid and their main use is on a DIRECT SMEAR = material taken directly from the patient and smeared on a microscope slide--> and get the answer

---these are primarily viruses and slow-growing bacteria

Front 45

5. animal testing

animal testing is use primarily to test _______

Back 45

virulence in strains

**The animal can be injected and you can look for the different signs that the animal will give.

Front 46

6. test that measure the host immune system (usually skin test)

what is serologic test?

Back 46

utilize the host's serum (fluid part of the blood) and react it w/ a known laboratory antigen from a microorganism; measure a humoral immune response, i.e presence of antibodies

note (this is stated in lecture):
The serologic test actually uses the serum that we centrifuge out. After centrifugation, we end up with the red blood cells on the bottom, the white blood cells, and finally the serum at the top. You can take that serum when you look for antibodies because antibodies are just floating proteins. You can take that and mix it with a known antigen. If you do so, it will precipitate on a glass slide. You can do what is called a slide agglutination test. This is a very rapid test.

Front 47

What are the two type of serologic test?

Back 47

1. slide agglutination
2. ELISA

**where you are looking for reaction with an antigen. You can take an antigen and dilute it out to a certain level. You expose this to someone’s serum and measure the agglutination. The concentration you use will tell you the concentration of that antibody in that serum (a convalescent antibody level).

Front 48

What is Skin test?

Back 48

measures the reaction of the host to substances (antigens) injected b/w layers of skin; usually measures cell-mediated immunity

Front 49

What are the usefulness of serologic and skin tests to diagnose infectious disease? (5)

Back 49

1. use this test when you cannot culture the organism
2. or if it can be cultured, but it is too expensive (e.g viruses)
3. where the agent is dangerous to culture e.g rickettsia
4. where the agent is slow growing (these test are good at locating slow growing organism)
5. where the agent is difficult to sample

Front 50

______ is where you are starting to apply to work on populations and individuals. If you can intervene right from the ______, you are going to save a lot of energy and control these infectious disease

Back 50

Medicine
Reservoir

Front 51

What is does asymptomatic means?

Back 51

A term used to describe an individual who does not currently show symptoms of the disease being discussed. Asymptomatic individuals may develop symptoms of the disease at a later point in time if and when the disease onsets.

Front 52

what is Primary Prevention?

Back 52

prevention of the infection from ever occurring in the first place

Front 53

what is Secondary Prevention?

Back 53

prevention of a secondary, more severe disease occurring from an initial infection or disease caused by the same organism

Front 54

body hygiene

Back 54

cleanliness; frequent washing

Front 55

quarantine

Back 55

public health enforced restricted movement of a person or animal w/ an infectious disease or exposure to it

Front 56

isolation

Back 56

restricted movement of an exposed but not sick individual