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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

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