Respiratory Pathogens Flashcards
Three respiratory bugs (focused in this packet)
Mycobacteria
Mycoplasma
Corynebacteria
Mycobacteria shape and growth
Acid Fast Rods
SLOW growth (from one pole only)
Mycobacterium cell wall contains…
Mycolic acids
arabinogalactan
PG
3 characteristics of mycolic acids
- acid fastness
- protect from lysozyme + complement
- anchored to PG directly or by arabinogalactan
What is cord factor?
Trehalose Dymycolate + something else
Mycobacterium product that stimulates cytokine production?
What cytokines?
Lipoarabinomannan (LAM)
TNF and IL-6 (which stimulate replication of HIV long terminal repeats)
Mycobacterium Tuberculosis major symptoms
fatigue, unexplained weight loss, hemoptysis
Clinical pathway for TB infection
- primary infection = exudative lesion
- either Heals, Necrotizes lung, or makes granuloma.
- Granuloma is either encased or spreads via lymph and blood
What is miliary TB?
a widely-disseminated TB infection
Also hits lungs
- Cells in center of granuloma include…
- What eventually forms upon tissue death?
- MQ, BC’s + DC’s
- Caseum forms from necrotic tissue that is damaged by inflammatory response and lack of blood supply
How many new TB cases per year?
10 million
(results in 1.5 million deaths)
High TB risk populations? (5)
- Minorities, Immigrants
- HIV patients
- Homeless
- Young/old
- Travelers
TB is always spread….
person to person via respiratory droplets
Tb attaches to _______ to invade.
What 3 cellular consequences does this have
Alveolar MQ
- Prevents phagolysosome fusion
- cytotoxicity from cord factor
- Cytokine mediated inflammation
Long term TB latency establishes in…
granulomas and bone marrow cells
Detection of TB is dependent on…
presence of T memory cells
Two ways to detect TB? Explain them?
Mantoux test
QuantiFERON-Gold assay (IGRA): tests for release of IFN-g when peripheral lymphocytes are stimulated by TB antigen
(more IGN-gamma is made when effector Tmem cells are present)
TB control?
Culture takes too long (6-8 weeks) and acid fast sputum stain needs a massive infection to be able to detect.
PCR is best! Use Tb-specific primers
–98% detection
–takes 90 minutes
Qualifications for latent TB? Treat or let it resolve?
IGRA+ or PPD+ without symptoms, and with normal Xray
ALWAYS treat (Isoniazid, Rifampin, or combination of both)
Treatment regimens for TB
Chemotherapy = long term with 4 drugs (INH, P, R, E) = (4HREZ)
DOTS important!! (observe them taking medicine)
BCG vaccine is used where? What is a pertinent fact regarding its use?
Everywhere but here
It will cause PPD+
Treatment for XDR-TB
NO = Beta lactams or carbapenems
YES =
- Meropenem+clavulanate
- Linezolid (but adverse reaction… neuropathy)
Other:
- Delaminid (inhibits MA synthesis)
- Bedaquiline (inhibits ATP synthase)
M. leprae initial presentation
whitened, anaesthetized skin area
progresses to either Tuberculoid (paucibacillary) or Lepromatous (multibacillary)
tuberculoid leprosy Sx
macular lesions
(usually) unilateral nerve involvement (sometimes bilateral)
Lepromatous leprosy Sx
Progressive nodular lesions
bilateral nerve death >> bone resorption and loss of extremities
M. Leprae tranmission and reservoirs?
transmitted by long-term contact
Humans and armidillos
M. leprae pathogenesis
inflammatory reaction damages nerve endings
hyposensitivity = soft tissue damage
M. Leprae treatment
Dapsone (sulfone) and Rifampin …(6-9 months)
Double treatment reduces sulfone resistance
Other Mycobacteria?
M. avium
- Most common nosocomial infctn in AIDS
- disseminated bacteremia
- Treat with clarithromycin and ethambutol for life
M. Kansasii
- TB like symptoms, noncommunicable
Mycoplasma types?
Mycoplasma pneumoniae
Mycoplasma genitalium
Ureaplasma urealyticum
Mycoplasma organism
really, really smalll. 380 genes.
like really small.
Mycoplasma cell wall
No cell wall!
Only a membrane, which has sterols that it steals from host
Mycoplasma appearance on agar?
fried-egg appearance
Mycoplasma presentation
(Walking) Atypical PNA (20%)
Tracheobronchitis (70%)
insidious onset, mild fever, lasts about 4 weeks
Mycoplasma can trigger…
Autoimmune encephalomyelitis
(due to immune mimicry)
Difference in breath sounds between typical and atypical PNA
Typical = bronchial breathing
Atypical = Wheeze (musical, high pitched, fine crackle)
Mycoplasma is transmitted via
respiratory droplets
Mycoplasma is common among…
school kids
highest in winter
Mycoplasma major pathogenic factors?
Proline-rich adhesion protein = forms elongated tip to adhere to epithelial cells
Protein M covers Fab region of antibody to block it
Cytotoxic effects = H2O2, O2 radical, competition for nutrients
Mycoplasma treatment
Can treat with Tetracycline or Erythromycin (macrolides)
(Azith is more common for treating lung infections right now, but resistance may become a problem)
**often do NOT treat if mild
Other Mycoplasmas typically present as ____. What are the three we covered?
STD’s
- M. genitalium (normal flora, NGU)
- M. hominis (salpingitis and post-partum)
- Ureaplasma urealyticum: Produces urease because it requires 10% urea for growth. Cause of nongonococcal urethritis in males (bladder stone)
Corynebacterium diptheriae shape / structure
(hint: what is weird about this organism’s structure?)
- Club shaped, pleomorphic
- Gram +
- Aerobic
- *contains outer membrane with mycolic acid
Corynebacterium culturing medium? (related to cell metabolism)
It will show up as black colonies on tellurite blood agar
b/c it reduces potassium tellurite to tellurium metal
Corynebacterium clinical presentation
- Throat infection
- Fever
- Swollen lymph nodes –> Bull neck
- PSEUDOMEMBRANE
How are toxigenic strains of Corynebacterium ID’d?
Elek immunodiffusion test
- filter paper with antitoxin placed at right angles to streaks of bacteria
- toxin and antitoxin form a precipitate
Corynebacterium spread via…
aerosolized droplets
Corynebacterium pathogenicity
AB toxin from beta phage conversion
- B binds to EGF-like receptor
- Partially denatures toxin in vesicle, hydrolysis occurs
- A binds to NAD–> ADP Ribosylates EF-2 transcription factor (STOPS protein synthesis)
How are Corynebacterium pathogenic factors controlled by the cell?
“tox” genes are controlled by the DtxR repressor
- Iron is a co-repressor
- The ToxAB operon gets shut off at iron concentrations above 10uM
- (Iron is normally kept low in the body by lactoferrin/transferrin
Clinically, why is the Corynebacterium toxin bad?
It causes cardiac damage, often resulting in heart failure and death
Do infants have passive immunity to Corynebacterium?
Yes!
Lasts for about two months
Corynebacterium vaccine type/dosing
Formalin-treated toxoid vaccine (DTaP)
Booster given every 10 years
***important for travelers to areas of high prevalence
Post infection control of Corynebacterium?
Quarantine
equine anti-toxin
PEN / **ERYTH ** (despite intoxication, not infection… it’s to keep the number of bacteria low)
