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Glossary of Pneumococcus

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Created by optom

what are the two strains of pneumococcus? which is the killer strain?

Describe the experiment that displayed TRANSFORMATION (DNA transfer)

(1) smooth - killers
(2) rough

Smooth colonies were heated so that they no longer could kill the mouse. Living R strains were mixted with the heat-killed S strain, and transformation lead to living S strains which killed the mouth (the living cells of the S strain were isolated from the dead mouse)


What does pneumococcus use quorun sensing to do?
express a competence-sensing protein and internalize DNA from other bacteria.

When bacteria in biofilm die, it can pick up virulence factors from them --> can aquire new traits, capsular variation, etc.

True or false:
The incidence of pneumococcal disease has dramatically decreased in Canada
FALSE.

still high... and these are deaths that can be completely prevented!

What are the 3 clinical cases that cause >25% of the deaths in children under 5 years
(1) Pneumonia
(2) Sepsis
(3) Memingitis

Streptococcus pneumoniae (or Pneumococcus) is the leading bacterial cause of these diseases (90% of these deaths are in developing countries)



What are the age risk factors for S. pneumoniae

What percentages of healthy children and adults have S. pneumococcus colonizing their nasopharynx

young age (65 years)

20-40% of healthy children and 5-10% of healthy adults have S. pneumonia colonizing their nasopharynx
In developed countries, at what age does pneumococcus colonize an infant?
6 months
In native Americans or disadvantaged members of developed societies, at what age does pneumococcus colonize infants?
the first few weeks of life

(recall it was 6 months for non-disadvantaged people in developed countries)

describe the physical structure of pneumococcus
- polysaccharide capsule (THICK capsule = more likely to be VIRULENT)
- gram-positive, lancet-shaped diplocci
- arranged in pairs

what are the functions of the outermost polysaccharide capsule?
(1) prevents entrapment of pneumococci in nasal mucosa and allows access to the lungs
(2) maximal expression of capsule is essential for systemic virulence (ie. thick capsule = greater virulence)
(3) capsule is antigenic (i.e. stimulates the production of specific antibody) and is strongly anti-phagocytic.

how many serotypes of capsular polysaccharides are present?
91 serotypes
What are some key pneumococcus virulence factors?
(1) Pneumolysin = cytolytic pore forming toxin released from cytoplasm during lysis.

(2) Cell surface proteins:
- choline binding proteins (Psp A and Psp C)
- LPXTG-anchored proteins (e.g. neuraminidase)
- lipoproteins




What is the mechanism of PNEUMOLYSIN (a pneumococcus virulence factor)?
Pneumolysin is a cytolytic pore-forming toxin released by lysis, and it may be involved in memingitis.

- activates complement and modulates host cell activity as it:
- inhibits ciliary movement of respiratory epithelium
- inhibits phagocyte respiratory burst
** can result in severe problems (dust, foreign antigens, etc. enter lungs)




Describe the structure of the choline binding proteins

What is the difference in function between the two types?

PSP (pneumococcal surface protein) A and C are found on top of the choline (they start in and sticks out of the capsule).

Psp-A = Anti-opsonization (inhibits complement)

Psp-C = Crosses respiratory epithelium



What are the mechanisms of virulence of the choline binding proteins PspA and PspC
PspA inhibits complement mediated opsonization

PspC binds to a receptor that normally transports IgA and this permits translocation across the respiratory epithelium.

LPXTG (a configuration present in almost all of the gram positive organisms) anchored proteins also have virulence mechanisms. Explain
- adhesion and colonization of nasopharyngeal cells
- pneumonia and bacteraemia
True or false:
Conjunctivitis is caused by both the capsulated and non-capsulated organisms
True
The two main diseases caused by pneumococcus are _________ and __________.

Name 3 other diseases it causes.

Pneumonia (lower lobes of lung) and Otitis media

Also causes:
- meningitis
- sinusitis
- bronchitis




At any given time, up to _____ % of people may carry pneumococci in the nasopharynx

This is important because pneumococcal disease begins with the establishment of the ________ state

60%

carrier state

What are the most common manifestations of pneumococcal disease?
(1) pneumonia - affects the terminal airways. Seen in extremes of age (65 years)
How does pneumococcus spread?
(1) direct contact with infected secretions
(2) droplet transmission
(3) daycare centers are common sites of spread

What is herd immunity?

(ON EXAM)

Vaccinated children improve herd immunity to pneumococcus. When the majority of a group gets vaccinated, it reduces the frequency of disease even in the non-vaccinated people (children).
Name 2 ways that pneumoccocal infection results:
pneumococci in nasopharynx are carried to anatomically contiguous areas (eg. eustachian tubes and nasal sinuses.

At the same time bacterial hindrance is cleared (eg. by mucosal edema)

What are some signs of pneumonia?
patient coughs yellow-green phlem that stains for pneumococci

X ray findings: white consolidated lobe on X-ray is seen in 80% of cases

Once pneumococcus has colonized the nasopharynx, where are the 3 main places it spreads to?
(1) middle ear
(2) lungs
(3) sinuses

What is the course of action once pneumococcus (that has colonized the nasopharynx) reaches the lungs?
(1) aspirated into bronchioles & alveoli & not cleared
(2) binds lung epithelium & endothelium
(3) activates complement & recruits leukocytes but prevents phagocytosis
(4) damaged lung tissue & leukocytes release inflammatory mediators allowing initiation of infection
(5) fibrinous edema fluid (with pneumococci) pours into alveoli
(6) consolidation of lungs
(7) mononuclear cells actively phagocytose the debris, and the liquid phase is gradually resorbed
(8) pneumococci are taken up by phagocytes & digested intracellularly leading to gradual resolution






What are the classic signs of lobar consolidation?

[clinical signs of pneumonia]

(1) rapid, distressed breathing [normal is 12-20 per min]
(2) nostrils dilate on inspiration
(3) cyanosis [bluish nailbeds, palate & extremities.. caused by abnormal circulation so give proper ventilation: oxygen mixed with air]
- chest movement is diminished on affected side
- auscultatory abnormalities such as crepitations



Streptococcus pneumoniae is the most common cause of ___________________________
community aquired pneumonia
what types of pneumonia usually affect adults?

..what about children?

Adults: types 1-8

Children: 6, 14, 19 and 23

In Canada, what are the two pneumoccocus vaccines?
7 serotypes were included in the conjugated PCV7 vaccine
- 4, 6B, 14, 18C, 19F, 23F
It accounts for >80% of invasive isolates in children

How is pneumococcus diagnosed?
(1) microscopic --> large #s of polymorphonuclear cells and slightly elongated gram-positive coccobacilli seen in pairs
(2) sputum culture is 90% specific
(3) Quellung Reaction
- sputum on slide --> add certain chemicals and capsulre appears to swell


How do you detect sinusitis caused by pneumococcus?

How do you detect Otitis media?

CT scan - fluid in maxillary sinuses

Middle ear is usually dull yellow grey. When inflamed (swollen eardrum) it is bulging, swollen and red.

Compare & contrast strep pneumoniae & strep viridans
Optochin is a chemical used to identify strep pneumonia (which is optochin sensitive) from other alpha hemolytic strep such as strep viridans

Test: place optochin disc on Agar plate.
- S. pneumoniae is inhibited
- S. viridans still grows



0.016 g/mL vs. 0.25 g/mL of penicillin. Which is more susceptible to the drug?
0.016 g/mL is fully susceptible to the drug and has LARGE growth area (ie. large zone of inhibition)

0.25 g/mL is partly resistant and has smaller zone of inhibition

What are the clinical signs of pneumonia in newborns/infants?

.. what is normal respiratory rate in newborns and infants

(1) Nasal flaring
(2) chest-wall indrawing
(3) raised respiratory rate (rapid breathing)

Normal respiratory rate:
newborns: avg 44 breaths per minute
infants: 20-40 breaths per minute





What are the WHO criteria for diagnosis of pneumonia in young children with cough or difficulty in breathing?
< 2 months: >60 breaths/min 2-11 month: >50/min 12-59 months: >40/min

severe pneumonia: chest-wall indrawing very severe: cyanosis or child has stopped feeding
What are some other possible causes of pneumonia? [differential diagnosis]
Viruses:
- Rhino & Corona Virus
- Influenze & Parainfluenza virus
- Adenovirus
- Epstein-Barr virus

Bacteria:
- Staphylococcus
- Streptococcus (group A, C or G)
- H. influenza
- Chlamydia pneumoniae
- Mycoplasma pneumoniae










How is pneumococcus treated?
Antibiotic-resistance is an issue (eg. to Penicillin) so some alternate drugs are:

- Erythromycin
- Sulpha drugs
- Chloramphenicol
- Vancomycin




Above what age is it safe to administer the 23-valent pneumococcal vaccine (with capsular polysaccharides from 23 serotypes)

What % of pneumococcal disease does it cover?

> 2 years

covers 85-90% of serotypes

[vaccine includes major serotypes which have developed antimicrobial resistance]



What is cross-protection and how does it benefit the pneumococcus vaccine?
antibody resistance to a certain serotype (eg. 6B) protects against another serotype (6B) even though it is not in the vaccine
What age group is the pneumococcal conjugate vaccine (PCV-7) licensed for?
< 9 years of age

13-valent vaccine has replaced PCV 7 and is given in ____ doses. When is each does given?

Which serotypes does PCV13 contain?

(1) 2 months
(2) 4 months
(3) 12 months

4, 6B, 9V, 14, 18C, 19F, 23F, 1, 5, 7F, 3, 6A, 19A



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