Bacterial Etiologic Agents Of CAP Flashcards
2 are the most common causes of CAP
- Streptococcus pneumoniae
- Haemophilus influenzae
Requires enriched media → blood containing
HAEMOPHILUS INFLUENZAE
- Found on the mucous membranes of the upper respiratory tract of humans
- Become opportunistic once the immune system of the host is compromised
HAEMOPHILUS INFLUENZAE
At 6-8 hours in rich medium, H. Influenzae becomes _______
small, coccobacillary forms
Later, H. influenzae becomes ________
longer rods, very pleomorphic
virulence factor of H. Influenzae
Capsule
o flat, grayish brown colonies
o Require the X (acts as Hemin) and V (NAD: Nicotinamide-Adenine-Dinucleotide) factors in blood
IsoVitaleX-enriched Chocolate Agar
Exposed in ______ for the brown color to appear
80 degree celsius
Does IsoVitaleX-enriched Chocolate Agar causes hemolysis.
No
Require both X & V factors to grow.
Haemophilus influenzae
requires V factor only for growth.
Haemophilus parainfluenza
requires only factor X without need of factor V.
Haemophilus ducreyi
In culture of H. Influenzae, it is a flat, grayish brown colonies after 24 hours incubation
Chocolate agar
In culture of H. Influenzae, it does not grow on sheep blood agar except around colonies of Staphylococci
satellite phenomenon
What are the antigenic structure of H. Influenzae?
- Capsular polysaccharides (a-f)
2. Outer membrane proteins
Causes meningitis in children (prior to the introduction of vaccine (HIB vaccine)
H. influenzae Type B (HIB)
it is the main cause of meningitis in young children between the age 5 months to 5 years
H. influenzae Type B (HIB)
Sx of H. Influenzae where most common cause in infants
Septic arthritis
Causes bronchitis or pneumonia in adults
H. influenzae Type B (HIB)
- Chronic
- Associated with cardiopulmonary disease
- Follows upper respiratory tract infections
PNEUMONIA
Treatment for Pneumonia
- Ampicillin + Sulbactam (Beta-lactamase inhibitor)
- 3rd generation cephalosporins
– Cefotaxime - Given IV – for meningitis
How to prevent patient with Pnuemonia?
- Hib conjugate vaccine (H. influenzae type B)
At what doses should be the vaccine given for px having Pneumonia?
3 doses (2,4,6 months) or - 2 doses (2 and 4 months);
Booster dose (between 12 & 15 months)
Mollicutes (cell wall-free bacteria)
MYCOPLASMA SP.
▪ closely related to M. pneumoniae
▪ has been associated with urethral and other urogenital infections
M. genitalium
▪ sometimes causes postpartum fever
▪ has been found with other bacteria in uterine tube infections
M. hominis
It is the cause of non-gonococcal urethritis in men and is associated with lung disease in premature infants of low birth weight
Ureaplasma urealyticum
- Smallest organisms that can be free in nature
- Highly pleomorphic (don’t have cell wall which makes them change shape)
- Bounded by a three-layered cytoplasmic membrane that contains sterol
Mycoplasma sp.
inhibits the cell wall bacteria and Mycoplasma is cell-wall-less
Penicillin
Inhibitories of Mycoplasma sp.
tetracycline or erythromycin (macrolides)
Grown on cell-free media that contain lipoprotein and sterol
Mycoplasma sp.
Form minute colonies → round, with granular surface and a dark center typically buried in the agar
o “Fried egg appearance”
o Requires lipoprotein and sterol
Mycoplasma sp.
Mycoplasma requires ____ ______ ____ and ____ in the culture medium
serum, glucose, or urea and yeast extract
Most important in Mycoplasma sp.
MYCOPLASMA PNEUMONIAE
Prominent cause of community-acquired pneumonia esp. in persons ________
5-20 years of age
MOT of Mycoplasma Pneumoniae
person to person by means of infected respiratory secretion
Initiated by attachment of the tip _______ of the organism to the receptor on the surface of respiratory epithelial cells
P1 Adhesin
Adherence factor of Mycoplasma Pneumoniae
P1 Pili
Reside extracellularly in the respiratory & urogenital tracts
Mycoplasma pneumoniae
Toxic metabolic products of Mycoplasma pneumonia
peroxide & superoxide
Immunopathogenesis of Mycoplasma pneumoniae
activate macrophages, stimulate cytokine production
IP of Mycoplasma Penumoniae
1-3 weeks (time of exposure to the time of onset of symptoms)
Its symptoms are: Malaise, fever, sore throat and cough (initially nonproductive, later with blood streaked-sputum and chest pain)
Mycoplasma pneumoniae
Other organisms that can cause atypical pneumonia
Mycoplasma, Chlamydia, Legionella
Resolution of pulmonary infiltrates in Mycoplasma pneumoniae
1-4 weeks
- Interstitial with peribronchial pneumonitis
- Necrotizing bronchiolitis
Pathogenesis of Mycoplasma pneumoniae
Complication of Mycoplasma pneumoniae
- Uncommon - Hemolytic anemia
How to diagnose Px with Mycoplasma pneumoniae
Largely based on clinical diagnosis
In Lab test of px w/ M. Pneumoniae, what is the result?
Slightly elevated WBC count
What can be found in the Sputum Gram stain of Px with M. pneumoniae?
PMNs and monocytes, no bacterial pathogens
What is the signifincance of using Sputum Gram stain?
To rule out other bacterial causes (S. pneumoniae)
Used for for group O human erythrocytes (50% of untreated patients) in M. Pneumoniae
Cold hemagglutinin:
Used to detect detect IgM and IgG antibodies in M. Pneumoniae
Enzyme Immunoassay (EIA)
Treatment of M. Pneumoniae
Tetracycline, Macrolides, Fluoroquinolone
o Produce improvement but do not eradicate M. pneumoniae
Obligate intracellular parasites with a tropism for the columnar epithelial cells
CHLAMYDIA (CHLAMYDOPHILA ) PNEUMONIAE
o Lack the mechanism for energy production so they cannot synthesize ATP, they need the mechanism from the host cell
CHLAMYDIA (CHLAMYDOPHILA ) PNEUMONIAE
Produce round, dense, intracytoplasmic inclusions that lack glycogen
CHLAMYDIA (CHLAMYDOPHILA ) PNEUMONIAE
Resistant to sulphonamides
CHLAMYDIA (CHLAMYDOPHILA ) PNEUMONIAE
Small, dense, pear-shaped body
The infectious form
Attaches and enters into target cells
Contains equal amounts of DNA and RNA
Stains purple with Giemsa
Elementary body
Larger, osmotically fragile
Metabolically active form
Form that divides by binary fission
Contains about 4 times RNA than DNA
Stains blue with Giemsa
Reticulate Body
immunodominant component of the antigen of the Chlamydia pneumoniae
2-ket0-3-deoxyoctanoic acid
Needs a cell for growth because they are obligate parasites
HL or Hep-2 cells (McCoy cells)
Clinically similar to M. pneumoniae but prodromal symptoms last longer up to 2 weeks
Atypical pneumonia
Usually affected by the atypical pneumonia of Chlamydia
Teenagers and young adults
What is found in the chest radiograph in Px with Chlamydia?
subsegmental infiltrate
▪ Less prominent than the infiltrate in M. pneumonia
- Pharyngitis
- Sinusitis
- Otitis media
Chlamydia
inhibits metabolism of eukaryotic cells
HL of Hep-2 cells with cycloheximide
Culture for chlamydia needs to be incubated at ______
35˚C for 3 days
Most sensitive method for the diagnosis of C. pneumoniae infection
Microimmunofluorescence test
Treatment for C. pneumoniae infection
- Tetracycline - Macrolides - Fluoroquinolone
- Fastidious (complex growth requirements)
- aerobic (require oxygen for growth, killed by the absence of oxygen)
- Gram (-) pleomorphic bacteria, but stain poorly by Gram’s method
LEGIONELLA PNEUMOPHILA
should be used as the counterstain by Legionella Pneumophila
Basic fuchsin (0.1%)
Colonies are: colorless to iridescent pink or blue and are translucent and speckled
Legionella P.
Its culture is BCYE media (buffered charcoal yeast extract) with alpha-ketoglutarate and iron
Legionella P.
Culture of Legionella P.
pH 6.9, T = 35°C, and 90% humidity
- Catalase (+), Oxidase (+)
- Hydrolyzes Hippurate
- Produces gelatinase and beta-lactamase
Legionella P.
cause of outbreak of Legionnaire’s disease
o Can also cause Pontiac fever
Serogroup 1
(+) cross-reactive antigenicity among different species
Legionella ap.
Produces proteases, phosphatase, lipase, DNase, RNase, metalloprotease
Legionella P.
Aquatic setting of Legionella that promotes bacterial growth (stagnant water)
Found in warm, moist environments, lakes, streams
Infection follows inhalation of bacterial from aerosols generated from contaminated air-conditioning systems and shower heads
Antigenic structure of Legionella P.
- Readily enters & grows within human alveolar macrophages and monocytes
- Do not require opsonization by C3b / antibody to enter macrophage
Pathogenesis of Legionella P.
virulence factor of Legionella P.
Mip protein
Mostly affected by Legionella P.
Disease is highest in men > 55 years old
Factors associated with high risk of Legionella P.
o Smoking
o Chronic bronchitis
o Emphysema
o Steroid and other immunosuppressive agents
o Cancer therapy
▪ Biologic agents as target, eg. Anti-TNF
o Diabetes mellitus
Symptoms: High fever, chills, malaise, non-productive (prominent) cough, hypoxia, diarrhea, and delirium (due to high fever)
Legionnaire’s Disease
Chest X ray findings in Px with Legionella P.
Reveal patchy, multilobular consolidation
- Milder form (flu-like manifestation)
- Fever and chills, myalgia, malaise, and headache that develop over 6-12 hours, dizziness, photophobia, confusion
Pontiac Fever
- Mild cough and sore throat
- Self-limited
- You may not give antibiotics
Pontiac Fever
Specimens used for Lab test in Legionella P.
o Bronchial washings
o Pleural fluid
o Lung biopsy specimens
o Blood
May be used early in the course (specific for serogroup 1) for the Dx of Legionella P.
Legionella urinary antigen test
Treatment for Legionella P.
- Tetracycline, Macrolides, Quinolones
- Prolonged therapy (may be up to 3 weeks)
- Small gram (-) bacilli, coccobacilli, or cocci in pairs
- Oxidase (+)
- Non-motile, non-fermentative
- Produce DNase
MORAXELLA CATARRHALIS
Basis for rapid fluorometric tests for identification
butyrate esterase
- Members of the normal microbiota of the upper respiratory tract
- Often produce beta-lactamase
MORAXELLA CATARRHALIS
Result of chest radiograph in Px with Moraxella Catarrhalis
Patchy infiltrates; occasional lobar consolidation
Treatment for Moraxella Catarrhalis
- Trimethoprim-sulfamethoxazole (Cotrimoxazole) or
- Amoxicillin-clavulanate or
- 2nd or 3rd generation cephalosporin
o 1st generation – Gram (+)
o 2nd generation – Gram (+) and (-)
o 3rd generation – Gram (-)
- Member of Enterobacteriaceae
- Gram (-) rods, non-motile
- With capsules – produce mucoid colonies
- Lactose fermenters
KLEBSIELLA PNEUMONIAE
Only lactose fermenter that produces urease
KLEBSIELLA PNEUMONIAE
CHARACTERISTIC ON CULTURE on Blood Agar
Slimy appearance of the colonies
CHARACTERISTIC ON CULTURE on MacConkey Agar (Mac)
Red/pink colonies
Culture characterisctic of Klebsiella P. On EMB
Produces large, mucoid, pink to purple colonies with no metallic green sheen
Klebsiella P. causes Pneumonia in _______
o Persons on alcohol abuse
o Those with diabetes mellitus
- Can be nosocomial (hospital-acquired)
- “Currant jelly” sputum (reddish jelly-like)
Klebsiella P.
Chest radiograph result in patients with Klebsiella P.
Lobar consolidation (like S. pneumoniae and H. influenzae)
Cavitation and empyema/pus (like S. aureus [#1 cause of empyema] and L. pneumophila pneumonia)
Complications of Klebsiella P.
- Severe form of CAP caused by K. pneumoniae with a predilection for upper lobes of the lungs
- Liable to suppurate and form abscess
- Seen in patients with chronic debilitating illnesses or alcoholism
- Alcoholic + currant jelly + infiltrates in upper lobe
Friedlander’s Pneumonia
Treatment for Px with Klebsiella P.
- 3rd or 4th generation cephalosporin
- For severe infection: add Gentamicin or Tobramycin
