85 terms

Aerobic Gram Positive Rods: Corynebacteria, Bacillus & Listeria

What Gram Positive Rods are "Spore Forming?"
1. Clostridium
2. Bacillus
What Gram Positive Rods are "Non-spore forming?"
1. Listeria
2. Corynebacterium
3. Erysipelothrix
4. Rhodoccus
Where in the world are Bacillus spores found?
What animals/species do Bacillus anthracis affect?
-Herbivorous ANIMALS (sheep, goats, cattle)
-HUMANS (contact with animals)
How do herbivores get Bacillus anthracis?
Herbivores come into contact with the SPORES or BACTERIA in the soil, which can last there for months/years
What are the forms of Anthrax?
1. Cutaneous (95%)
2. Respiratory
3. Gastrointestinal
What forms of Anthrax are found naturally?
All 3
Describe the pathogenesis of Anthrax
1. Spores are DEPOSITED in skin, respiratory or GI mucosa
2. Spores then GERMINATE in tissues
4. Toxins cause TISSUE NECROSIS
5. Anthrax toxins DISSEMINATE through bloodstream and lymphatics
6. Anthrax causes systemic toxicity and DEATH
What toxins are produced by anthrax?
1. Lethal toxin
2. Edema toxin

CAPSULE blocks phagocytosis and toxins inhibit neutrophil function (oxidative burst) & induce cytotoxic effects
How does Cutaneous Anthrax manifest clinically?
Pruritic papules on exposed skin
-Enlarges over several days, progressing to an ulcer with/without surround vesicles
-EDEMA surrounds the lesion
-Often painless, regional lymphadenopathy
After germination and transport via the lymphatics, where do the Respiratory anthrax spores go to?
Hilar/mediastinal lymph nodes
What do antrax toxins do to the mediastinum?
Cause necrosis and hemorrhage
What do Chest XRay and CT findings show with respiratory anthrax?
WIDENED mediastinum
What are the symptoms of respiratory anthrax?
Substernal pain and cough
Signs of stridor (noisy breathing) on exam
Neck and mediastinal edema
What does necrosis in the pleura from anthrax lead to?
Pleural effusions
How does respiratory anthrax spread?
How many phases are there to respiratory anthrax? What are they?
1. Initial phase (1-3 days)
Malaise, fever, dry cough, sub-sternal pain
2. Secondary Phase
Sudden onset, rapid progression to death in 1-2 DAYS!!
Dyspnea, stridor, high fever, diaphoresis
Mortality high, over 90% (difficult to diagnose!)
How is respiratory anthrax diagnosed?
Chest X-ray with Widened mediastinum!
-Bloody pleural tap
-Culture blood, pleural fluid or CSF for Gram Positive Rods
How does a human contract GI anthrax?
Human consumes meat from an infected animal
Where do INGESTED spores germinate?
Intestinal mucosa
How does Gastrointestinal Anthrax present?
One of TWO forms:
1. Oropharyngeal Anthrax (hard palate, postpharynx)
2. Abdominal Anthrax (Large bowel, cecal lesions)
How do you diagnose someone with Anthrax?
High Clinical Suspicion
-Must be able to recognize clinical syndromes
How do you treat anthrax?
IV Penicillin G, doxycycline, ciprofloxacin
What is used for prophylaxis measures for anthrax?
Doxycycline or quinolone (cipro), up to 6wk
How do you control antrax disease?
Must control the ANIMAL disease
What types of infections do Bacillus cereus cause?
-Food poisoning
-Traumatic ocular infections
Bacillus cereus pathogenesis
1. Enzymes destroy tissue
2. Toxins cause diarrhea/emesis
3. Anti-microbial agents produced by bacteria help the bacteria to compete
What are the two types of food poisoning?
1. Emetic form
vomiting predominate feature
2. Diarrhea form
cramps, nausea, watery stools
What is an example of a food that causes emesis?
Fried rice
What are examples of foods that cause the diarrheal form of food poisoning?
Contaminated MEATS (turkey) or VEGETABLES
How long does it take for Bacillus cereus to incubate in the emetic form?
<6 hours
How long does it take for Bacillus cereus to incubate in the diarrheal form?
10-12 hours, improved in 24
What is the virulence factor that is responsible for Bacillus cereus food poisoning?
Enterotoxin production
How do you diagnose Bacillus cereus?
Clinical syndrome
-Culture the FOOD
How do you treat food-poisoning?
Self-limited, so no antibiotic therapy is need
What bacillus species is responsible for ocular infections?
B. cereus
How are bacillus ocular infections usually caused?
-Trauma (soil exposure)
-Foreign body (particles of dust, soil or shrapnel)
-IV drug abuse
How do Bacillus ocular infections manifest?
-Ocular abscess
How long does it take for Bacillus cereus to cause damage to the eye
RAPID: 12-48 hours
-pain, redness, visual changes
What are important Corynebacterial Infections?
1. C. diphtheriae
2. C. jeikeium
3. Arcanobacterium haemolyticum
4. Rhodococcus equi
What organism causes diptheria?
Corynebacteria diptheriae
What does C. jeikeium cause?
How does C. diptheriae appear on a gram stain?
CLUB shaped
What is C. diptheriae's virulence factor?
What does C. diptheriae's virulence factor do?
-Inhibits protein synthesis
-Extremely potent
-Responsible fo tonsilar/pharyngeal exudate that characteristics of diptheri
What is a protective factor to diptheria?
Having antibodies to the diptheria exotoxin
What is the reservoir for diptheria?
What percentage of diptheria remains as an asymptomatic carrier state on the skin and pharynx?
How is diptheria transmitted?
Transmission through bacteria in AIRBORNE droplets or CONTACT with secretions/exudate
When is diptheria usually around?
COLDER months
What conditions make diptheria more prominent?
Crowded conditions
Who is at risk for diptheria today?
Children <15 yo if unvaccinated
Unimmunized or unboosted adolescents/adults (urban poor, those with no access to health care, IV drug users)
What does the diptheria exudate consist of?
Necrotic collection of cells, fibrin, dead respiratory epithelial cells, RBCs, WBCs and bacteria
What can the diptheria exudate cause?
-OBSTRUCTION of the airway
How can DEATH be caused by diphteria?
Aspiration of the membrane?
Besides the exudate, how does someone with diptheria usually present in the clinic?
-Fever, sore throat and membrane development (tonsils, posterior pharynx)
-Cervical lymph nodes common
-Systemic effects on tissues at distant sites
-Cardiac toxicity (myocarditis)
-Neurological toxicity
Paralysis of palate, hoarseness or stridor
What is special about Listeria Monocytogenes?
Is listeria pathogenesis extra or intracellular?
Intracellular pathogenesis
Listeria risk of disease?
Rare cause of disease but risk to select population
What kind of diseases is Listeria responsible for?
Food borne disease
What bacterium is zoonotic?
Listeria monocytogenes
How is Listeria moncytogenes transmitted among humans?
Vertical transmission ONLY
What general foods can harbor Listeria monocytogenes?
Raw vegetables, raw milk , raw fish, meants and poultry
What are specific examples of foods that can harbor Listeria monocytogenes?
-Unpasteurized soft cheeses
-Ready-to-eat products/meats
-Smoked fish
Who is most at risk for Listeria monocytogenes?
-Neonates and elderly
-Pregnant women
-Impaired cell-mediated immunity, immunosuppressed
How long is the incubation time for Listeria monocytogenes?
11-70 days
How does Listeria monocytogenes infection usually begin?
Ingestion of contaminated food
What promotes Listeria monocytogenes infection?
-Gastric surgery
-H2 blockers (stomach pH increased)
Where does Listeria monocytogenes like to stay in the body?
What is the pathogenesis of Listeria monocytogenes?
-Binds epithelial cells
-Escapes host's ability to kill the organism
-Survives intracellularly
What are the clinical diseases caused by Listeria?
1. Meningitis
2. Bacteremia
3. Gastroenteritis
4. Neonatal infection
5. Listeriosis
What parts of the CNS does Listeria meningitis affect?
Brain, brainstem, meninges
What is the mortality of Listeria meningitis like?
High mortality, ~20%
Who is at risk for Listeria meningitis?
>60 yo or neonates
-Patients on steroids or chemotherapy
What does Listeria meningitis cause in patients?
Seizures, 30% CSF samples have monocyte predominance
How can Listeria affect neonates?
1. Granulomatosis Infantiseptica
2. Meningitis 2 weeks after birth or immediate Sepsis after delivery
What happens to pregnant women when they get Listeria during prenancy?
Major decline in cell-mediated immunity
How do you treat Listeria meningitis?
Empiric therapy
Why do you want to treat maternal Listeria monocytogenes infections?
To prevent neonatal death
What is the major reservoir of Erysipelothrix rhusiopathiae?
How does a human become infected by Erysipelothrix rhusiopathiae?
DIRECT cutaneous contact
-Occupational exposures: fishermen, butchers, veterinarians
What are the 3 clinical syndromes associated with Erysipelothrix rhysiopathiae infection?
1. Erysipeloid skin lesion
2. Diffuse skin rash/systemic
3. Endocarditis
Describe an Erysipeloid skin lesion
Violaceous, raised and well defined lesion, usually associated with lymphadenopathy
How do you distinguish erysipeloid from routine cellulitis?
Exposure history