24 - Bacterial Infections of the Upper Respiratory Tract I Flashcards
1
Q
What areas of the body are considered to be a part of the upper respiratory tract (URT)?
A
- Conjunctiva
- Nasolacrimal ducts
- Middle ear
- Nose pharynx
- Sinuses
- Nasal cavity
- Larynx
- Epiglottis
2
Q
What are the two main jobs of the URT?
A
1 - Inhalation
2 - Regulation of air
3
Q
What does the job of inhalation consist of?
A
- Inhalation of approx. 0.5 L with each breath we take
- Approx. 16 breaths per minute
4
Q
What parts of the air we inhale does the URT regulate?
A
1 - Temperature
2 - Water content
5
Q
What is unique about the URT?
A
- Its membranes are being constantly bombarded with particles
- It is the part of the body that is MOST exposed to pathogens
6
Q
What does the final destination of particles within the URT depend on?
A
The size of the particle
7
Q
Where will fairly large particles end up?
A
Trapped in the nasal turbinates and mucus
8
Q
Where will slightly smaller particles end up?
A
Trapped in the trachea
9
Q
Where will small particles end up?
A
They will settle in the terminal airways and alveoli
10
Q
Where will very small particles end up?
A
They will stay suspended in the air
11
Q
What is important to remember about the destination of particles in the URT?
A
- These are generalities, not strict rules
- There is overlap between ranges of particle size
- Example: A 7 micrometer particle could either get trapped in the nasal turbinates/mucus or trachea
12
Q
What type of epithelium will you find in the URT?
A
Ciliated epithelium
13
Q
What is the rate at which the ciliated epithelium beats?
A
1000 beats per minute
14
Q
What is a mucociliary escalator?
A
The process that consists of the cilia continually beating and pushing mucus up and out of the URT and into the throat
15
Q
What is the function of the mucociliary escalator?
A
MAJOR barrier against infection
16
Q
How does the mucociliary escalator prevent infection?
A
Microorganisms hoping to infect the respiratory tract are caught in the sticky mucus and moved up by the mucociliary escalator
17
Q
What is the overall process of the mucociliary escalator?
A
Pretty gross…
- All humans constantly have mucous propelled out of the mastoids middle ear, nasolacrimal ducts, sinuses and his lungs and then swallows it
- This is NORMAL human physiology
18
Q
What are four factors that can slow down or stop mucociliary?
A
- Viral infections
- Smoking
- Alcohol consumption
- Narcotics
19
Q
What is the goal of a pathogen related to the mucociliary escalator?
A
AVOID being caught in the mucociliary escalator and swallowed
20
Q
What parts of the respiratory system are considered to be sterile?
A
- Mastoid air cells
- Middle ear
- Sinuses
- Trachea
- Bronchi and bronchioles
- Alveoli
21
Q
What does this mean in terms of infection?
A
There is not any normal flora of the sterile areas - any bacteria found in these areas is considered to be pathogenic
22
Q
What can cause sterile places of the respiratory tract to become NOT sterile in some individuals?
A
Permanent damage to the tissues
23
Q
Is the conjunctiva sterile or not?
A
It is an interesting situation…
- It is supposed to be sterile
- Because of the location, you will often times find pathogens in the conjunctiva
24
Q
What is included in the normal flora of the nose?
A
1 - Staphylococcus epidermidis
2 - Staphylococcus aureus
3 - Corynebacterium spp.
25
What are staphylococcus aureus?
- Gram positive cocci clusters
| - Facultative anaerobes
26
What percentage of healthy adults carry staph. aureus in the nares?
20%
27
In the hospital setting, how does the percentage of healthy adults carrying staph aureus in the nares change?
It increases
- Health care workers will have a higher percentage
- Families of health care workers will have a higher percentage
28
What are corynebacterium spp.?
- Gram positive rods
- Pleomorphic
- Non-spore forming
29
What is pleomorphism again?
The ability of some bacteria to alter their shape or size in response to environmental conditions
30
Is the corynebacterium spp. the diphtheria pathogen?
NO - it is considered normal flora
31
What shape will staph. aureus take when they are pathogenic?
They will appear like a cluster of grapes
This is what you will see if you take a sample of an infection
32
What are the normal flora of the nasopharynx?
```
1 - Streptococcus mutans
2 - Streptococcus mitis
3 - Streptococcus milleri
4 - Streptococcus salivarius
5 - Moraxella catarrhalis
6 - Bacteriodes
```
33
What type of bacteria are the streptocuccus viridans group?
Gram positive cocci that will form chains
34
We know these bacteria are normal flora, but we also know that they can cause infection... What accounts for this phenomenon?
Normally they aren't pathogens unless you put them in the wrong spot - Any organism can be a pathogen if you put it where it shouldn't be
35
What are moraxella catarrhalis?
- Gram negative bacteria
- Diploid coccobaccilus
- Aerobic
36
What are bacteriodes?
- The only one of the URT normal flora that is an anaerobe
37
How does an anerobe survive in the URT?
If someone’s anatomy allows there to be pockets of deoxygenation, it can survive
38
What does streptococcus pneumonia look like in pleural exudate?
It is found in pairs
39
What is interesting about the normal flora of the nasopharynx?
All of the bacteria found in the normal flora of the nasopharynx increase during the winter months and can be pathogenic during that time
40
What accounts for this phenomenon?
- The normal flora of the nasopharynx is always present, even in vaccinated individuals
- If you put the normal flora in the right tissues and in an immunocompromised individual, you will see them become serious pathogens
- During the winter, many individuals experience bouts of compromised immunity
41
What are the four normal flora of the nasopharynx that have seasonal pathogenic associations?
1 - Streptococcus pneumoniae
2 - Haemophilus influenzae
3 - Neisseria meningitides
4 - Moraxella catarrhalis
42
What are streptococcus bacteria?
- Gram positive cocci in chains
- Catalase negative
- Consists of several groups of pathogens
43
What is the difference between staph and strep in terms of catalase?
- Streptococcus = catalase negative
| - Staphylococcus = catalase positive
44
What is catalase again?
A common enzyme found in nearly all living organisms exposed to oxygen (such as vegetables, fruit or animals). It catalyzes the decomposition of hydrogen peroxide to water and oxygen.
45
What does this mean in terms of the characteristics of streptococcus and staphylococcus?
- Streptococcus = catalaste negative = NOT able to break down hydrogen peroxide reactive oxygen species)
- Staphylococcus = catalase positive = able to break down hydrogen peroxide
46
There are several types of streptococcus. What are they?
- Group A
- Group B
- Group C
- Group D
- Alpha-hemolytic
47
What are Group A strep?
Streptococcus pyogenes (beta)
48
What are Group B strep?
Streptococcus agalactiae (beta)
49
What are Group C strep?
Streptococcus bovis
50
What are Group D strep?
They are actually no longer considered to be a straptococcus bacteria
- Enterococcus faecalis
51
Why are enterococcus fecalis bacteria of concern?
They are a major group of pathogens found in the hospital
52
What are alpha-hemolytic strep?
Streptococcus pneumoniae
*** If you see alpha-hemolytic on an exam, you should think strep, pneumoniae***
53
What is streptococal pharyngitis?
"Strep throat"
54
What characterizes streptococcal pharyngitis?
Characterized by...
- Redness of the throat
- Patches of adhering pus
- Scattered tiny hemorrhages
- Fever
55
What pathogen causes strep throat?
Streptococcus pyogenes
56
How do you differentiate strep pyogenes from different types of strep?
The type of hemolysis they demonstrate
57
What type of hemolysis does strep pyogenes have compared to the other types?
Strep pyogenes
- Beta-hemolytic
All others
- Alpha or gamma hemolysis
58
What does beta-hemolytic mean?
Sometimes called complete hemolysis
It is a complete lysis of red cells in the media around and under the colonies
The area appears lightened (yellow) and transparent
59
How do you test for strep throat?
Rapid strep test, which targets the cell wall antigen
60
If a rapid test comes back negative, can you trust it?
No
61
If a rapid test comes back positive, can you trust it?
No
62
How do you make a final decision whether or not your patient has strep?
Must look at other signs and symptoms to determine your diagnosis and how to treat them
63
How will strep throat test in a catalase test?
Catalase NEGATIVE
***
64
What is the M protein of strep pyogenes?
It is an antiphagocytic virulence factor in strep throat
65
How many serotypes of staph pyogenes are there?
Over 80
66
What is "cross protection"
When you are either vaccinated against or become infected and produce antibodies against one serotype of a bacteria and you are then protected from other serotypes within the same bacteria
67
Does strep pyogenes of strep throat exhibit cross protection?
NO
68
What does this mean in terms of a single patient?
You can get strep throat this week, get rid of it, and two weeks later get a different serotype of strep throat
69
Do all strains of strep pyogenes have a capsule around them?
No, not all, but some
70
What does a capsule around strep pyogenes do?
Inhibits phagocytosis
71
Does a capsule make a strain of strep pyogenes more or less severe?
MORE severe when you have a capsule
72
What does this mean for certain geographical areas and the spread of strep pyogenes?
If you have a capsulated strain moving around in a geographical area, that would explain why a lot of people are getting sick
73
What are streptococcal pyrogenic exotoxins?
Super antigens that are responsible for scarlet fever, toxic shock and necrotizing fasciitis
***Super antigens are important***
74
What do pyogenic exotoxins cause?
An upregulation or massive immune response which causes damage to the affected tissues
75
There are 9 proteins that are streptococcal pyrogenic exotoxins. What are they?
- SPE-A
- SPE-B
- SPE-C
- SPE-D
- SPE-E
- SPE-F
- SPE-G
- SPE-H
- SPE-I
76
What do these exotoxins cause?
- Fever
- Rash
- T-cell proliferation
77
What diseases do the exotoxins lead to?
- Scarlet fever
- Toxic shock
- Necrotizing fascitis
78
Which one of the diseases is the only one that is proceeded by strep throat symptoms?
Scarlet fever
***
79
Case study: A 10 year old female patient presents with redness of the throat, patches of adhering pus, scattered tiny hemorrhages, and temperature of 38.9C.
You do a throat culture. What would you expect to see?
Throat culture results
| - Blood auger plate with patches of clear areas
80
What do the clearings on the blood auger plate mean?
Where you see clear areas, you have lysis of the RBCs of the blood auger plate
This means the clear areas demonstrate hemolysis - the pathogen present is hemolytic
81
What is the diagnosis?
Streptococcus pyogenes - a hemolytic bacteria
82
Will strep pyogenes recover spontaneously?
Yes, most cases will recover spontaneously in about 7 to 10 days
83
Why do we treat strep pyogenes?
Because of the risk of scarlet fever, rheumatic fever, etc.
84
How do we treat strep pyogenes?
- 10 days of penicillin or erythromycin (these are good "go-to antimicrobials")
85
Why will some physicians avoid penicillin all together an only use erythromycin?
Allergies
86
Is there a vaccination to strep pyogenes?
No - it is not practical because there are 80 different serotypes and they are NOT cross protective
87
What are the serious diseases that can arise from untreated strep pyogenes?
- Scarlet fever
- Acute rheumatic fever
- Necrotizing faciitis
- Acute glomerulonephritis
88
What is scarlet fever?
A condition where SPE (an exotoxin) is released from the strep pyogenes and causes redness of the skin and a white coating on the tongue
89
The longer the bacteria is there the _________ the infection gets.
Worse
90
Why does the in infection worsen with time?
Because exotoxins continue to release toxins
91
How can you get rid of scarlet fever?
All you need is antibiotics - you will cure the disease and it will go away
92
What are the symptoms of acute rheumatic fever?
- Fever
- Joint pain
- Chest pain
- Rash
- Skin nodules
- Uncontrollable jerky movements
- Acute inflammatory process
93
What type of toxicity is observed in rheumatic fever?
Neurotoxicity
94
What is the basis of the severity of rheumatic fever?
The immune response
95
Describe why the immune response of rheumatic fever can be detrimental to the body
*** It is a cross reaction of our immune response to the strep pyogenes in our own tissues, so as soon as you mount a strong immune response to strep pyrogenes, it can start attacking our own tissues and cause all of these issues***
96
How severe does rheumatic fever get?
It can be fatal
97
There are two clues to you as a health care provider that you may have a patient with rheumatic fever. What are they?
- It is an immune response, so it will take 7-10 days for the response to form
- You find NO strep pyogenes in the patient upon culture
98
Why won't you find any strep pyogenes in the patient with rheumatic fever?
The organisms are gone because your immune system has killed them – now, you are just seeing an attack on the patient’s own tissues, causing pathology
99
Will you treat rheumatic fever with antibiotics?
NO
100
What can you treat rheumatic fever with?
Immunosuppression might work
101
What is necrotizing fasciitis?
SPE release that causes skin infections that can also arise from strep pyogenes
102
What causes necrotizing fasciitis?
- A strep pyogenes infection somewhere else in the body
- The release of exotoxins that reach the skin
- Results in a skin infection
103
What is an example of the presentation of necrotizing fasciitis?
A 5-year-old girl with cervical adenitis followed by desquamation of the hands after scarlet fever
(image on slides)
104
What is another example of the presentation of necrotizing fasciitis?
Desquamation of the hands after streptococcal pharyngitis and scarlet fever
(image on slides)
105
How do you predict which strains of strep pyogenes will resolve on its own and which will cause problems such as rheumatic fever?
It is just the luck of the draw – just what is circulating in the community
106
Can strep pyogenes leading to necrotizing fasciitis cause a sever infection?
Yes, you can get a very severe infection from necrotizing fasciitis
107
What is acute glomerulonephritis?
A disease caused by strep pyogenes that typically affects children and begins 1-4 weeks after strep throat or 3-6 weeks after a skin infection
108
What are the symptoms of acute glomerulonephritis?
- Edema
- Hypertension
- Hematuria
- Proteinuria
- ***Decreased serum complement levels***
109
What is the mechanism of the disease?
You will see an immune response that includes deposition of antigen-antibody complexes in the glomeruli (of the kidney)
110
What streptococcal group is strep pyogenes in?
Group A
111
Which of the following are caused by a TOXIN of streptococcus pyogenes?
- Rheumatic fever
- Acute glomerulonephritis
- Scarlet fever
Scarlet fever
112
What is the disease process of those three again?
- Scarlet Fever – erythrogenic toxin
- Rheumatic fever – inflammatory auto immune attack
- Acute glomerulonephritis – immune complex
