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Respiratory Pathogens II- Streptococcus pneumoniae, Klebsiella pneumoniae, Legionella pneumophila

Respiratory Pathogens II- Streptococcus pneumoniae, Klebsiella pneumoniae, Legionella pneumophila Professor: Dr. Barrett TSOM- Term 4, Unifed Exam 1
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what are microbiological features of Streptococcus pneumoniae?
1. Encapsulated
2. Lancet shaped
3. Gram positive Streptococcus
4. not Lancefield typed
5. antigenic capsular polysaccharide
6. alpha hemolytic on BAP
7. viridans streptococcus
8. fails to grow on simple media
9. colonies mucoid and glisten
10. self autolysis and dissolution over time
11. soluble in bile, other detergents
12. sensitive to optochin
is Streptococcus pneumoniae encapsulated?
yes
what shape is Streptococcus pneumoniae?
lancet shaped
is Streptococcus pneumoniae Gram positive or negative
Gram positive
is Streptococcus pneumoniae typed by lancefield classification?
no
what are the functions of the capsular polysaccharide of Streptococcus pneumoniae?
antigenic
antiphagocytic
used in typing
what is the hemolytic activity of Streptococcus pneumoniae on BAP?
alpha hemolytic
what are the features of streptococcus colonies?
-alpha hemolytic
- viridans
- fails to grow on simple media
- colonies mucoid and glisten due to capsule
- self autolysis and dissolution over time
to what disk test is Streptococcus pneumoniae sensitive?
optochin (P disc)
what are the features of Streptococcs pneumoniae under a microscope?
diplococci with unstained capsules
cells are elongate or lancet shaped
what is serologic typing Streptococcus pneumoniae based on?
differences in its polysaccharide capsule (90 serologic types)
which serologic types of Streptococcus pneumoniae are most frequently isolated from pneumococcal pneumoniae?
lower numbered types
what is the basis of useful vaccines for Streptococcus pneumoniae?
capsular polysaccharides
is Streptococcus pneumoniae found in healthy individuals?
Upper respiratory carriage in normal health in 5-10% of adults, 30-40% in children
-serotype varies
what typically comes before Streptococcuse pneumoniae infection?
Often antecedent viral respiratory disease, COP, asthma, SMOKING, alcoholism
how much CAP is caused by Streptococcus pneumoniae?
cause of about 35% of community acquired pneumonias (CAP) as opposed to hospital acquired pneumonia
how is Streptococcus pneumoniae acquired?
aerosols
aspiration
to lungs via blood from distant sites
what type of disease is Pneumococcal pneumonia?
lobar disease
what are the clinical features of Streptococcus pneumoniae?
Abrupt onset
fever
chills
rigors
cough
chest pain
rusty blood tinged sputum
what are the most virulent and most common serotypes of Streptococcus pneumoniae?
capsular serotype 3 most virulent and lower numbered most common
what conditions result in poor clearance of the pneumococcus by the spleen with greater susceptibility and more severe S. pneumoniae disease?
splenectomy
HIV
sickle cell disease
asplenia
other conditions
what other diseases are caused by Streptococcus pneumoniae?
meningitis
bacteremia
leading cause of otitis media
sinusitis
what fraction of otitis media is caused by Streptococcus pneumoniae?
38%
what are the Virulence factors of Streptococcus pneumoniae?
1. Surface protein adhesins
2. Antiphagocytic capsule
3. Secretory IgA protease
4. Teichoic acid and peptidoglycan fragments
5. Pneumolysin
6. Phosphocholine binding proteins
7. Capsule of S/R form
how do surface protein adhesins act as virulence factors for S. pneumoniae?
aid colonization
what is the most important virulence factor of S. pneumoniae?
antiphagocytic capsule
how does Secretory IgA protease act as a virulence factor for S. pneumoniae?
binds to Fc site of sIgA and digests it, aiding bacterial escape from mucosal antibody
how do Teichoic acid and peptidoglycan fragments act as virulence factors for S. pneumoniae?
they activate C5 and C5a, increase inflammatory response of phagocytic cells, are anti-virulence
what type of toxin is Pneumolysin and how does it act as a virulence factor for S. pneumoniae?
CDC (cholesterol dependent cytotoxin):
- activates classic complement pathway and
- attracts WBC's that release TNFα, IL1, other inflammatory interleukins,
- may be toxic to ciliated cells
how do phosphocholine binding proteins act as virulence factors for S. pneumoniae?
attach bacteria to platelets and endothelial cells and bacteria 'hide' inside these non-professional phagocytes
how doe the smooth and rough forms of capsule for S. pneumoniae act as virulence factors?
- S form resistant to phagocytosis
- R form unable to cause disease
what is involved in laboratory diagnosis of S. pneumoniae?
1. sputum collection--> gram stain, tendency for diplococcus arragnement--> specimens to BAP/broth then BAP.
2. small colonies on BAP--> alpha hemolytic in 24h, mucoid, glisten, dimple due to autolysis
3. Optochin (P disc) on plates inhibits growth
4. bile solubility test applied to suspensions
5. Quellung capsular swellng test in presence of antisera
6. identification of cell wall carbohydrate common to all serologic groups in urine
what are the limitations of the Quellung capsular swelling test?
not in frequent use
expensive
low observer reliability
what is a very reliable test for S. pneumoniae?
identification of cell wall carbohydrate (not capsule) common to all serologic groups in urine by rapid immunodiffusion test
is nucleic acid testing need for S. pneumoniae?
rarely
what are the features of optochin test for S. pneumoniae?
nice zone of growth inhibition around the P disc
- is a simple test for identifying Gram positive Streptococci as the pneumococcus
how is a bile solubility test for pneumococcus interpreted?
clearance of turbid broth growth of pneumococcus by bile:
- Streptococcus mitis not lysed by bile
- Streptococcus pneumoniae lysed by bile
what are the features of the 23 valent S. pneumoniae vaccine?
PPVSV-23 covers 88% of most frequent isolates-->
advised for adults over 65 and children 2 or older at high risk
- contains only T cell independent polysaccharide antigens
what are the features of the 13 valent S. pneumoniae vaccine?
PCV-13 replaces eariler 7 valent vaccine
- conjugated to protein
-advised for children and adults
- T dependent antigen
what are the features of S. pneumoniae resistance?
-increasing resistance to penicillins and other antibiotics
- multi drug resistant pneumococci increasing in importance
-**sensitivity testing advised
what are the microbiological features of Klebsiella pneumoniae?
- Gram negative
- encapsulated
- gamma hemolytic bacillus
- pili
- LPS
- member of Enterobacteriaceae has capsular and somatic antigens (K and O)
- grows well on ordinary media and produces mucoid, glistening colonies
- colonies on lactose and dye containing media develop pink color
- urease positive
is Klebsiella pneumoniae Gram negative or Gram positive?
Gram negative
is Klebsiella pneumoniae encapsulated?
yes
what is the hemolytic activity of Klebsiella pneumoniae?
gamma hemolytic bacillus
does Klebsiella pneumoniae have pili?
yes
does Klebsiella pneumoniae have LPS?
yes
to what family does Klebsiella pneumoniae belong?
Enterobacteriaceae
what type of antigens does Klebsiella pneumoniae have?
capsular and somatic antigens (K and O)
on what type of media does Klebsiella pneumoniae grow?
grows well on ordinary media
what types of colonies does Klebsiella pneumoniae produce?
mucoid, glistening colonies due to capsule
what happens to colonies of Klebsiella pneumoniae on lactose and dye containing media?
develop pink color due to lactose fermentation and dye uptake
is Klebsiella pneumoniae urease positive or negative?
Urease positive, can use citrate as sole carbon source
where is Klebsiella pneumoniae found?
- normal flora of the mouth, intestine, and skin
- disease in alcoholics, diabetics, and elderly
what are the features of the pathogenesis of Klebsiella pneumoniae?
1. Hospital and community acquired bronchopneumonia- upper lobes, 50% mortality
2. Blood tinged or currant jelly sputum
3. the old man's friend, quiet death
4. nosocomial- indwelling catheters, respirator equipment can lead to septicemia
what causes nosocomial Klebsiella pneumoniae infection?
indwelling catheters
respirator equipment
can lead to septicemia
what are the virulence properties of Klebsiella pneumoniae?
1. Antiphagocytic capsule
2. LPS toxicity
3. Pili for attachment
what is involved in laboratory diagnosis of Klebsiella pneumoniae?
1. Sputum to BAP (non-hemolytic) and enteric media with dyes (pink colonies), mucoid due to capsule, Gram stains
2. Biochemical tests- urease and citrate utilization
how is Klebsiella pneumoniae prevented?
prevention in intensive care departments is difficult, respirator sterility
what is the treatment for Klebsiella pneumoniae?
aminoglycosides
quinolones
cephalopsporins
others
does Klebsiella pneumoniae carry a risk of resistance?
yes
what does a K. pneumoniae culture look like?
mucoid, gelatinous, pink colored colonies on EMB agar are typical
what is the history of Legionella pneumophila?
- First of the emerging pathogens, 1976 American Legion Conference in Philadelphia
- Blind passage method for recovery of unknown pathogens led to identification of previously unknown bacterial pathogen
what is the most important member of the Legionella genus?
L. pneumophila
what are the microbiological features of Legionella pneumophila?
- Slender, small Gram negative bacilli
- very hard to stain
- best to use silver impregnation or other stains (FAB)
- pleomorphic
- high nutritional demands- cysteine, Fe--> special medium BCYE
- Reside in protozoa in open ground waters
How many members in the Legionella genus?
50 members in the genus, several pathogens
L. pneumophila is the most important
what type of organism is Legionella pneumophila?
slender, small Gram negative bacillus
is Legionella pneumophila easy to stain?
no:
very hard to stain
best to use silver impregnation or other stains (FAB)
pleiomorphic
what are the nutritional demands of Legionella pneumophila?
cysteine
Fe
what type of medium was developed for the culture of Legionella pneumophila?
buffered cysteine yeast extract established for isolation because BAP is inadequate
where does Legionella pneumophila reside in ground waters?
in protozoa
what are the epidemiological features of Legionella pneumophila?
1. World wide, natural water sources and soil
2. Aerosols from cooling towers, showers, water misters, hot tubs, fairly resistant to chlorine in water. can grow at 45F
3. survives inside amoebae in natural waters
4. 10K-20K/USA/year, mostly over age 40, unreported
does chlorine in water kill Legionella pneumophila?
Legionella pneumophila is fairly resistant to chlorine in water
what are the pathogenic and clinical features of Legionella pneumophila?
1. Necrotizing focal pneumonia called legionnaire's disease, multilobar attack, non comunicable dry cough, little sputum
2. Influenza like disease called pontiac fever, 1968, no pneumonia
3. elderyly and compromised are the victims, can be mild in young
What are the virulence factors associated with legionnaire's disease?
1. Outer membrane porin protein (OMP)
2. Mip (macrophage invasion potentiator)
3. coiling phagocytosis
4. prevents typical phagolysosome formation
5. non-obligate intracellular pathogen in amoebae
how does the OMP of Legionella pneumophila act as a virulence factor?
- binds to C3b, promotes phagocytosis, MφCR3 binds C3b, an anti-virulence factor
how does Mip ct as a virulence factor in Legionnaire's disease?
aids in cell entry
how does coiling phagocytosis act as a virulence factor in legionnaire's disease?
coiling phagocytosis by thin pseudopods, bacteria survive since no acidifcation in such phagosomes
what does prevention of typical phagolysosome formation act as a virulence factor in legionnaire's disease?
blocks ROS, survives inside of cells
how does Legionella being a non-obligate intracellular pathogen act as a virulence factor in legionnaire's disease?
non-obligate intracellular pathogen in amoebae and man, facultative, can grow outside cells too
what type of secretion is associated with Legionella infection?
type IV secretion
what is involved in the laboratory diagnosis of Legionella pneumophila?
1. direct fluorescent antibody staining of specimen
2. Culture on BCYE medium
3. Nucleic acid amplification tests
4. Ag detection tests for Ag in urine
5. Ab detection by enzyme or FAB tests
what is the sensitivity of direct fluorescent antibody staining of L. pneumophila?
25-75%
how does BCYE work for culture of L. pneumophila?
contains all needed nutrients and charcoal neutralizes toxic fatty acids in media, CO2 useful, growth after 3-5 days
how often are nucleic acid amplification tests for L. pneumophila used?
not used often
what is the limitation of antigen detection urine tests for L. pneumophila?
good but not applicable to all antigenic varieties
what is the titer diference in Ab detection of L. pneumophila by enzyme or FAB tests?
four fold titer increase between acute and convalescent titers
what is involved in the prevention of Legionella pneumophila?
1. minimize exposure of elderly by control of possible water and soil sources
2. identify and eliminate sources:
- hyperchlorination
- superheating water supplies
- replace shower heads
- stop water mists of vegetables in grocery stores
what is the treatment of Legionella pneumophila?
erythromycin originally used and newer macrolides currently preferred