Exam 1: Meningitis II (lecture checkpoint questions) Flashcards
Where is H. influenzae commonly found?
It is a major part of the normal flora in URT in humans
Which diseases does H. influenzae cause?
• otitis media, conjunctivitis, other URT disease
- chronic bronchitis (especially in smokers)
- a major cause of invasive disease* and meningitis in children
*invasive disease’s (rare) include: cellulitis, pneumonia, sepsis, meningitis
What is the shape of H. influenzae and the Gram staining pattern?
• H. influenzae is a gram (-) facultative anaerobic coccobacilli
(more rounded that normal bacilli)
• non-typeable (non-encapsulated) strains of H. influenzae are most common
• H. influenzae is also y-hemolytic (non-hemolytic).
• H. influenzae is a LOS (no O-antigen!)
Which agar is used to grow Haemophilus? Which other genus is commonly grown on this agar?
- grown on enriched chocolate agar (no growth on blood agar)
- Small, moist, transparent colonies
- Haemophilus will grow on any agar, as long as you add X and V-factor!
Does the Hib vaccine cover all serotypes of H. influenzae? If not, then which one does it cover?
- The _Hib vaccine*_ only targets the type B serotype
- however, H. influenzae type B is the most virulent (the most common** serotype isolated in invasive disease!)
- 6 serotypes of H. influenzae (a, b, c, d, e, f)
- capsule is the major VF for H. influenzae
*conjugate vaccine for bacterial polysaccharide capsules used for infants and children (< 2 yr old)
**The Non-typeable (non-encapsulated) strains are the most common (60-90% in children, 35% in adults) and is normal flora in the nasopharynx
What does “thermally dimorphic fungi” mean?
- The fungi exists as both a mold or yeast, depending on the temperature.
- For the ones in this lecture, they are found as mold in the soil (25º C) and yeast in the body (37º C)
Geographically, where do you find Histoplasma?
Histoplasma capsulatum:
- worldwide (particularly tropical areas) and throughout the U.S., but is endemic in Ohio and Mississippi River valleys (central U.S.)
- Grows in soil, especially in areas with bird and bat droppings
Geographically, where do you find Blastomyces?
Blastomyces dermatitidis:
- Endemic in Ohio, Mississippi, Missouri and Arkansas river valleys of U.S. (central U.S.), Microfoci in Central and South America and parts of Africa
- Grows in soil, especially in areas enriched with decomposing organic debris
- No association with birds or bats
Coccidioides:
Geographically, where do you find Coccidioides?
Coccidioides immitis:
- endemic in the hot, arid Sonora desert region of southwestern U.S. (CA, AZ, NM, TX) and parts of Mexico
- Found in isolated areas of South America
- Disease in wild & domestic animals
- Grows in soil, almost exclusively in areas with fine sand and silt.
Which form of these fungi are found in patient samples: mold or yeast?
grow as filamentous molds at room temperature, but convert to a yeast form which shifted to 37° C in the human body or 37° C in laboratory conditions
How do these fungi typically infect people?
Does person-to-person transmission occur?
No, person-to-person does not occur
The fungi are found as mold in soil → spores (conida) go airborn → inhalation of airborne → the fungi is converted to yeast inside the human body
Which diseases are commonly associated with Histoplasma?
Histoplasma: can appear Similar to primary TB (and can remain latent for long periods)
Chronic pulmonary
- Progressive form of disease in older patients, underlying diseases, such as COPD (smokers)
- Develop large cavities, upper lobes of lungs
- occurs when the host cannot clear nor contain (latent) the infection. Systemic spread is common under these conditions!
Disseminated
- Immunocompromised most common patient (>70%)
- AIDS at greatest risk
- Lymph nodes, heart, bone marrow, adrenal glands, CNS, skin, GI tract
- Untreated is fatal
Which diseases are commonly associated with Blastomycosis?
Blastomycosis: can appear Similar to primary TB (not latent)
Acute pulmonary
(More acute/purulent than histoplasmosis)
- Acute illness resembling bacterial pneumonia, 3-15 weeks after exposure to B. dermatitidis
- Productive cough with purulent or mucopurulent sputum
- Mixed granulomatous and purulent inflammatory reaction (rare cavities)
Chronic pulmonary
• More likely to have granulomatous lesions similar to TB
Disseminated
- Hematogenous spread and replication typically occurs in most cases of blastomycosis
- Skin is the most common site of extrapulmonary infection (20-25% of cases)
- Skin may be the primary presenting symptom
Which diseases are commonly associated with Coccidioidomycosis?
Coccidioidomycosis: can appear Similar to primary TB (Some evidence for latent infections)
Moderate respiratory
- Acute illness resembling bacterial pneumonia
- Productive cough with sputum
- small percentage of patient develop nodules or cavities in the lungs (TB-like)
Disseminated
- Most common site is skin
- Meningitis is the most serious and lethal complication of disseminated disease
Which fungal infection is shown?
Why? Be able to verbally distinguish as well as visually.
Blastomyces dermatitidis
25° C
Growth as a mold with asexual reproduction with production of typical conidia (microconidia)
37 ° C
Growth as big thick-walled yeasts with broad-based budding
Which fungal infection is shown?
Why? Be able to verbally distinguish as well as visually.
Histoplasma capsulatum
25° C
Growth as a mold with asexual reproduction and production of microconidia and large macroconidia*
37 ° C
Growth as small yeasts with budding
*The presence of macroconidia distinguishes Histoplasma from Blastomyces (no macroconidia)
Which fungal infection is shown?
Why? Be able to verbally distinguish as well as visually.
Coccidioides immitis
25° C
Growth as a mold with asexual reproduction and production of arthroconidia
37 ° C
Growth in the “yeast-like” phase with production of very large spherules with endospores
Buzzword: Sinus Trauma
Adults – non-typeable strains of H. influenzae from sinus trauma*
you should also consider S. aureus!
*Heavy damage to the sinus cavity increases the risk of invasive diseases by the colonizers of the nasopharynx
Massive skin trauma increases the risk of invasive diseases by S. epidermiditis
Buzzword: Thumb print sign
epiglottitis!
epiglottitis in children 3-5 years old is still caused primarily by H. influenzae type B
(uncommon, but still possible even after the HiB vaccine)
Epiglottis: Flap at the base of the tongue made of cartilage tissue that blocks food from entering the trachea.
What do these Buzzwords refer to?
Birds, Bats
“Caver’s disease,” “Spelunker’s Lung,” “Darling’s disease,“ “Ohio valley disease,“ “Reticuloendotheliosis“
Most common endemic fungal infection in the U.S.
Histoplasma capsulatum:
- Grows in soil, especially in areas with bird and bat droppings
- Birds - do not get disease or carry the fungus. Feces enrich the soil for enhanced growth
- Bats – can get the disease and transmit disease through feces, as well as enriching the soil
What do these Buzzwords refer to?
organic debris, firewood
Blastomycosis:
• Fungus likes organic debris- infects people collecting firewood, tearing down old buildings, farming, other similar outdoor activities
What do these Buzzwords refer to?
Valley Fever
California or Arizona, or deserts
archeologists, outdoor activities
Coccidioidomycosis:
- 95% of cases in California and Arizona
- Infects normal people – C. immitis considered to be one of the most virulent of the fungal pathogens
- Potential biological warfare agent
- Most severe disease is still in immunocompromised
What is a a common agar used to grow fungi?
Sabouraud agar is a common agar used to grow fungi
(Low pH 5.6) inhibits bacteria
3 bacteria with capsule as the major virulence factor
H. influenzae, S. pneumoniae, N. Meningitidis
3 bacteria that produce IgA protease
H. influenzae, S. pneumoniae, N. Meningitidis
• IgA protease prevents the opsonization* of the bacteria, thus protecting it from phagocytosis
*to prepare for eating
2 bacteria that optimally grow using chocolate agar
H. influenzae, N. Meningitidis
• Chocolate agar is used – RBC cooked (lysed) to release the hemin and NAD ( usually additional NAD supplementation required)
