Microbiology Exam 3

What Gram+ organism(s) prouce spores?

Clostridium, Bacillus

Clostridium is an (aerobic/anaerobic) organism in a __________ shape.

anaerobic, bacilli

Which pathogen is responsible for cellulitis, fasciitis, and myonecrosis with gas formation in the soft tissue (gas gangrene)?

C. prefringens

How does Clostridial myonecrosis occur?

A deep penetrating wound or surgery.

What Gram+ infection is associated with extensive muscle necrosis, shock, renal

failure, and death, often within 2 days of initial onset?

Clostridial myonecrosis

Gas gangrene is casued by metabolic activity of the rapidly dividing bacteria which releases ___________ and __________

Hydrogen, CO2

Describe the appearance of C. perfringens when Gram stained:

• Rectangular Rods

• Gram +

• absence of inflammatory cells

Describe the treatment for C. perfringens myonecrosis:

1.) Debreidment

2.) High Dose Antibiotics

3.) Hyperbaric O2

4.) Possible Amputation

Why is hyperbaric O2 treatment effective in treating C. perfringens myonecrosis?

The pathogen is anaerobic and can only produce toxin in an anerobic condition. Oxygen prevents that.

True or False: A C. perfringens food poisoning infection causes abdominal

cramps, watery diarrhea, fever, nausea, and vomiting.

False (No fever, nausea, or vomiting)

Necotizing enteritis is caused by the pathogen __________.

C. perfringens

Necrotizing enteritis is a process taking place in the __________.

Jejunum

A rare necrotizing process in the jejunum characterized by acute abdominal pain, vomiting, bloody diarrhea, ulceration of the small intestine, and perforation of the intestinal wall, leading to peritonitis and shock

Necrotizing enteritis

C. tetani are ________ shaped.

Drumstick (due to the terminal spores)

The neurotoxin ___________ is released when the cell is lysed, and responsible for the clinical manifestations of tetanus.

Tetanospasmin

Tetanospasmin inhibits the release of neurotransmitters __________ and _________ causing spastic paralysis.

GABA, Glycine

Which condition is associated with the sardonic smile (lockjaw)?

Generalized Tetanus

Neonatal tetanus typically occurs from an infection of the __________.

Umbilical stump

What is the treatment for tetanus?

• Prevent violent, agonizing muscle spasms

• Patients are kept in dark, quiet rooms to minimize sensory triggers.

• They are given high doses of continuous sedatives and muscle relaxants

Which botulinum toxins are associated with human disease?

A, B, E, F

Which pathogen involves excitatory neurons and stimulates endocytosis of the

toxin molecule?

Clostridium Botulinium

Because acetylcholine is required for excitation of muscle, the resulting clinical presentation of ____________ is a flaccid paralysis (floppy limbs, muscle weakness, difficulty breathing and eating)

Botulism

How is foodborne botulism diagnosed?

If toxin activity is demonstrated in the implicated food or in the patient’s serum, feces, or gastric fluid

How is botulism treated?

Ventilatory support, antitoxin

C. difficile binds to the __________.

Intestinal epithelium

True or False: C. difficile is part of the normal intestinal flora

True (Infection is caused by overgrowth due to dysbiosis from antibiotic use)

How is C. difficile diagnosed?

Demonstration of the enterotoxin or cytotoxin in a stool specimen from a patient with compatible clinical symptoms

Pseudomembranous colitis is caused by what pathogen?

C. difficile

Which Gram+ bacillus is anaerobic and non-spore forming?

Listeria (L. monocytogenes)

True or False: L. monocytogenes can grow in high salt concentration

True

Which Gram+ pathogen is motile and exhibits a characteristic tumbling motion?

L. monocytogenes

What is the primary source of infection for L. monocytogenes?

Contaminated food and some human to human transmission (mostly mother to child)

True or False: L. monocytogenes is an intracellular pathogen

True

Explain the infectious process of L. monocytogenes:

1. Invade — internalins help enter the cell

2. Escape — listeriolysin O and phospholipases break the vacuole allowing L. monocytogenes to enter the cytoplasm

3. Replicate — multiply in the cytoplasm

4. Spread — ActA recruits actin to propel the bacterium into neighboring cells (Actin rockets)

Becuase _______________ gains entry into macrophages after passage
through the intestinal lining, bacteria can be carried to the carries the bacteria to the liver, spleen and brain, leading to disseminated disease (Trojan-horse phenomenon).

L. monocytogenes

Granulomatosis infantiseptica is a severe form of early-onset ___________ in neonates characterized by the formation of abscesses and granulomas in multiple organs and a high mortality rate unless treated promptly.

listeriosis

What is the treatment for L. monocytogenes?

Antibiotics

Bacillus is (anaerobic/aerobic)

aerobic (catalase +)

What are the three major virulence factors of B. anthracis?

Capsule, edema toxin, lethal toxin

True or False: There are no preventative measures that can be taken against B. anthracis

False (There is a toxoid vaccine)

95% of naturally acquired anthrax infections in humans result from inoculation of Bacillus spores through _________.

Exposed skin (contact with soil/infected animal products)

What are the signs and symptoms of cutaneous anthrax?

The development of a painless papule at the site of innoculation that progresses into a painful ulcer (can cause systemic infection)

What are the signs and symptoms of gastrointestinal anthrax in both the upper and lower intestinal tract?

Upper: ulcers in mouth/esophagus leading to regional lymphadenopathy, edema and sepsis

Lower: nausea, vomiting, malaise leading to a systemic infection

How does pulmonary anthrax develop?

Endospores reach the lower airway, then alveolar macrophages ingest these spores and transport them to the mediasteinal lymphnodes

What are the signs and symptoms of a second stage pulmonary anthrax infection?

Rapidly worsening cough/fever, edema, massive enlargement of mediasteinal lymph nodes, respiratory failure, sepsis

Which pathogen is responsible for the infection in which the mediastienal lymph nodes are massively enlarged?

B. anthracis (Pulmonary anthrax)

What is the treatment for pulmonary anthrax?

A lot of antibiotics, however most patients will die within 3 days of inital infection

Which pathogen is associated with gastroenteritis, ocular infections, and intravenous

catheter-related sepsis?

B. cereus

The (emetic/diarrheal) form of B. cereus food poisoning results from consumption of contaminated starch rich foods like pasta and rice. Most bacteria are killed during the initial cooking of the rice, but the heat-resistant spores survive.

emetic

The (eneteric/diarrheal) form of B. cereus food poisoning is a true infection resulting from ingestion

of the bacteria in contaminated meat, vegetables, or sauces.

diarrheal

How does an occular infection of B. cereus occur?

A traumatic, penetrating injury of the eye with a soil-contaminated object

What is the treatment for Bacillus panophthalmitis (occular B. cereus)?

Antibiotics and often the loss of the affected eye

Which Gram+ pathogen(s) are non-spore forming?

Corynebacterium, Listeria

Which Gram+ pathogen shows club-like rods (L/V shaped)?

Corynebacterium

True or False: Corynebacterium is a commensal bacteria

True

How is C. diphtheriae spread?

Respiratory droplets, direct contact

What is the major virulence factor of C. diphtheriae?

Diphtheria toxin

Explain the mechanism of diphtheria toxin:

1.) Toxin binds to host cell (through heparin-binding epidermal growth

factor receptor)

2.) Toxin enters cytoplasm

3.) Toxin inactivates EF-2

4.) Protein synthesis stops

5.) Cell death occurs

True or False: C. diphtheriae can result in asymptomatic colonization for fully immune people

True

C. diphtheriae causes localized damage to the ___________ as a result of exotoxin activity

pharynx

What are the systemic effects of C. diphtheriae?

Heart/nervous system damage

What are the signs and symptoms of C. diphtheriae?

Malaise, sore throat, exudative pharyngitis, low-grade fever

What is a unique feature of a C. diphtheriae infection?

The thick psuedomembrane made up of lymphocytes, plasma cells, fibrin, and dead cells can grow throughout the upper respiratory tract and cause bleeding when removed due to the adherence to the underlying tissue

Is there a vaccination for C. diphtheriae?

Yes (DPT)

True or False: Diphtheria only presents in the upper airway

False (Cutaneous diphtheria)

The genus of C. diphtheriae is _________.

Corynebacterium

GI tract immune cells and lymphatic tissue:

MALT

Most GI infections are caused by _______________.

Fecally contaminated food/water

What two enterobacteriaceae pathogens are short, straight, Gram-negative bacill?

Escherichia coli, Salmonella enterica

What is the resevoir (natural habitat) of Enterobacteriaceae?

intestinal tract of humans and animals

(E. coli/Salmonella) is a part of the normal intestinal microbiota of humans and animals

E.coli (the presence of Salmonella indicates infection)

E.coli is (motile/non-motile)

motile

Indicates mammalian fecal contamination of aquatic environments, soil and vegetation

Coliforms

The EXPEC classification of E. coli causes ____________.

UPEC (Urinary Tract Infections)

True or False: EXPEC causes opportunistic infections

True

What is the most prevalent strain of STEC?

O157:H7

What enterobacteriaceae is commonly associated with dysentary?

STEC

True or False: STEC is resistant to gastric acids

True

O157:H7 has a (high/low) ID50

low (highly virulent)

What are the signs and symptoms of O157:H7?

Abdominal pain, watery diarrhea, low grade fever or no fever common; may progress to severe bloody diarrhea and cramping

Are asymptomatic cases of O157:H7 still infectious?

Yes

Severe cases of _________ can cause UTIs, sepsis, hemorrhagic colitis, and/or Hemolytic Uremic Syndrome (HUS), a potentially fatal cause of kidney failure.

O157:H7

What is the treatment for an infection of O157:H7?

Fluid replacement (NO ANTIBIOTICS, NO ANTIDIARRHEALS)

True or False: Antibiotics can treat an O157:H7 infection

FALSE (they increase production of Shiga toxin which precipitate HUS development)

True or False: Antidiarrheals should not be used in treatment of O157:H7

True (it can prolong illness)

Which Gram- bacilli is flagellated and acid-sensitive?

B. salmonella enterica

(E. coli/Salmonella enterica) is an intracellular pathogen.

Salmonella enterica

How is Salmonella enterica acquired?

Ingestion of fecally contaminated food/water

Which salmonella enterica subspecies is invasive, systemic, & potentially fatal?

Typhi

Which salmonella enterica subspecies is localized and self-limited self-limited causing diarrhea?

gastroenteritis

True or False: S. Typhi only infects humans

True

A (high/low) infectious dose is necessary for S. Typhi to infect a host.

high (due to low acid tolerence)

S. Typhi colonizes the mucosa of the ____________, penetrates epithelium begins to spread systemically.

Small intestine

What is the key to the infection of S. Typhi?

Ability to enter/cross GI epithelium without inflammatory response

What are the signs and symptoms of S. Typhi?

• High, sustained fever (104F; toxin induced), condition progressively deteriorates with diarrhea, rashes, extreme fatigue, delirium

• May result in life-threatening hypovolemic shock, intestinal perforations/
  hemorrhage, endotoxic shock, myocarditis, meningitis

True or False: You can be both an asymptomatic carrier of S. Typhi and experience a relapse long after active infection

True

How is S. Typhi diagnosed?

Stool and blood cultures (H, K, O antigen presence)

How is S. Typhi treated?

Targeted antibiotics (Broad-spectrum can deplete gut microbiome and make infection worse)

How can S. Typhi be prevented?

Maintaining a healthy gut microbiome, vaccination, prevent fecal-oral contamination and spread

True or False: S. Enteritidis is always pathogenic

False (it’s a normal part of the intestinal microbiome of many animals)