Uncommon Bacterial Pathogens Flashcards
Bacillus Antracis –
Bacteriology
- what is the distinctive morphology?
- Where does it live? How is it transmitted ?
Gram positive rods – large “boxcars”
forms spores in the laboratory and in the field
Non motile; facultative anaerobic
Lives in the soil and in herbivores
Transmitted by coming into contact with spores or contaminated meat
-NOT TRANSMITTED PERSON TO PERSON
Describe the pathogenesis and virulence factors of Anthrax:
Two Plasmids:
1) Encodes Poly D Glutamic Acid Capsule– (unique bc its not an amino acid capsule, not a polysaccharide)
2) Tripartite Toxin Plasmid:
- Protective Antigen
- Edema Factor
- Lethal Factor
Describe the mechanism of Edema Factor and Lethal Factor?
what organism produces these?
Bacillus Antrhacis
- Edema factor (A subunit) – Adenylate Cyclase; raises cAMP; intereferes with phagocytosis and signaling of phagocytes
Lethal Factor (A subunit): metalloproteases; MAP kinase Kinase which paralyzes lymphocytes leading to death
What are the three disease types than can manifest from anthracis?
Briefly Describe the presentation of each
Cutaneous
Gastrointestinal –
Inhalation
Describe the cutaneous form of anthrax –
- presentation
- what is the mortality rate?
Cutaneous – Most common (95%)
Spores enter through breaks in the skin.
Presents as painless pruiritic pustule that quickly enlarges leave BLACK ESCHAR + EDEMA
No Fever or LAD
20% mortality rate
Describe GI anthrax:
How do you get it?
Presentation?
mortality rate
Gastro-intestinal:
spores ingested (eg from contaminated beef).
Can survive high temperatures, so cooking it doesn’t kill it.
Symp - fever, gastroenteritis, vomiting, hematemesis, bloody diarrhea… Toxemia –> Death
Symptoms are non specific
higher mortality rate (50+%) bc its hard to recognize
Describe Inhalation anthrax
- How do you get it?
- Initial presentation?
- terminal presentation?
- what is distinct about the CXR?
- Spores are inhaled
- gereminate in the lung macrophages
Symptoms (2-5 days) fever, malaise, cough, myalgia
CXR: Widened mediastinum (hemorrhagic adenitis of the hilum)
Late symptoms (1-2 days): hemorrhagic pleural effusions, hypoxia, cyanosis, dyspnea, shock and death
Treatment of Anthrax:
Prevention of Anthrax
Traditional : PCN + Doxycyclin
Animal studies: Cipro
2001 Survivors: FQ + clinda OR Rifampin
Vaccine: noncapsulated strain that has protective antigen but not the other toxins
Yersinia Pestis
- Bacteriology
- how are humans infected ?
- what is the reservoir in the environement
GN coccobaccilus
Humans infected from flea bite
Reservoirs: rats, squierrels, rabbits
Virlence factors of Yersina Pestis
- 2 plasmids which encode:
type 3 secertions
Fibrinolysis
(if no fibrinolysis, cannot become invasive; stays as local infection)
Disease forms of Yersinia Pestis?
- how does each present ?
Bubonic Plague:
Bubo = large infected LN
Sx: Bubo, HA, malaise, myalgia
Pap/Purpuric lesion at the site of the flea bite
Pneumonic Plague: Highly contagious;
HA, mailse, fever, cough, dyspnea, cyanosis, hemoptysis, respiratory failure
Septicemia: No Obvious Bubo or PNA; patient’s present with sepsis. Die from shock and DIC
Medical management of Yersinia
FQs (cipro)
Tetracycline
TMP/SMX
Genitmicin/streptomycin
Prophylaxis:
- bubonic contacts: TMP/SMX, tetracyclines,
Pneumonic contacts: cipro, tetracyclines
• Francisella tularensis - Epidemiology: what part of the world is it found? what animals harbor it? What is the ID? how is it transmitted?
- Found in the norther hemisphere
- Rabbits (Skinning)
and ticks
Very low ID: 1-10 CFU
no person to person trasmission
What are the important clinical forms of • Francisella tularensis
Ulceroglandular: ulcer with regional adenopathy at site of tick bite
Pneumonic: similar to pneumonic plague presentation
Abrupt onset fever, chills, HA, myalgia, non productive cough,
CXR: segmental, lobar infiltrates, hilar adenopathy
Treatment of • Francisella tularensis
is there a vaccine?
Tetracyclines or FQ
(Strepto and gentimicin in the past)
No Vaccine
• Listeria monocytogenes
bacteriology:
GPR, facultative anaerobe, motile
Beta Hemolytic
Listeria Monocytogenes
Epi:
how is it transmitted
what foods are implicated
where can it grow?
Foodborne pathogen — milk, cheese, meats, coleslaw, cantaloupe
undercooked chicken, microwaved hotdogs
Can grow at wide range of temperatures (1C - 45C); including your fridge
Pathogenesis of lysteria monocytogenes
what proteins are used to help it infect and spread
Internalin: bind to the tip of exposed E cadherins
Invades macrophages
Lysteriolysisn – escapes the phagsome within the macrophage
Act A – activates polymerization of actin; pushing towards neighboring cells to infect (act A is unevenly distributed on dividing lysteria, therefore will move uni-directionally)
Phospholipases
Risk Factors for Lysteria infection
-
Certain foods (unpastuerized diary, etc)
98% of cases have underlying disease/condition
Extremes of Age
Pregnancy
Immunocompromised (steroids, AIDS, cancer, transplant)
Describe the pregnancy associated form of listerosis
Pregnancy Associated:
Mothers won’t develop the disease outright
3rd Trimester - may present with fever, chills, myalgias, bacteremia
Septic Amnionitis: crosses the placenta and passed to the child leading to septic abortion/premature labor
The neonate: - acquires the disease in utero: overwhelemd with microabscesses: granulomatous infantiseptica dies in utero
- may present healthy for first month of life and develop meningitis later
what is the divide between the clinical presentations of listerosis?
Pregnancy associated
non pregnancy associated
Describe the non pregnancy associated form of listerosis ?
Leading cause of meningitis in immunocompromised patients
meningoenchephalitis, gasteroenteritis; some cases of enteric abscess
Presentation: fever, HA, altered sensorium; some have focal neurological signs (seizures, cranial nerves, hemiparesis)
Treatment of Listeria monocytogenes
What is it resistant to?
Treatment: penicillin or ampicillin
Amp + clavulonate
TMP-SMX
Resistant to ALL CEPHALOSPORINS and vancomycin
How do you treat a 70 yo male presenting with meningitis?
What causes meningitis?
Strep pnuemo – use ceftriaxone (has good csf coverage)
But ALSO listeria — use Ampicillin
Bartonella henselae
Bacteriology
what is this also known as ?
how is it transmitted
cat Scratch Fever
Transmitted by cats bit, scratch or fleas
GNR, Slow growing
Presentation of Bartonella Henselae in kids
Treatment:
unilateral adenopathy, but patient is mostly fine
happens mostly in kids
Treatment: abx would shorten the duration but not 100% indicated
Presentation of Bartonella Henselae in HIV patients
Treatment
Bacillary Angiomatosis -
Cutaneous or visceral disease that has proliferation of RBCs
Erythematous papules on the skin
Treat: macrolides and tetracyclines
• Brucella spp.
bacteriology:
how is it transmitted:
Presentation:
tiny, fastidious, gram negative cocco bacilli
direct contact or contaminated milk/milk products, esp unpasteurized milk/milk products
Presentation; Fever, malaise, without localizing symptoms
Can cause osteomyelitis, or infectious arthritis
Treatment of Brucella:
long course of tetracyclines, initially combined with aminogylcosides
