Infectious Diseases and C.difficile Quiz

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Questions and Answers

What is the most common route of acquiring human disease in the cases mentioned?

Ingestion of spores from contaminated food

Inhalation of spores from biological weapons

Direct contact with infected animals

Inoculation of spores through exposed skin (correct)

Which of the following describes the hallmark of cutaneous anthrax?

A high fever and chills

Severe abdominal pain and diarrhea

A necrotic eschar with surrounding edema (correct)

A persistent dry cough

What are the first symptoms associated with gastrointestinal anthrax?

Persistent headache and dizziness

Loss of appetite and fatigue

Nausea and vomiting (correct)

Fever and rash

In the absence of treatment, what is the case-fatality rate for cutaneous anthrax?

20% Signup and view all the answers

What method is used to confirm clinical diagnosis for the diseases mentioned?

Detection of toxins in food or patient's serum Signup and view all the answers

What is the recommended treatment approach for mild disease caused by C.difficile?

Discontinuation of the implicated antibiotic Signup and view all the answers

Which toxin of C.difficile is described as a potent cytotoxin that inhibits protein synthesis?

Toxin B Signup and view all the answers

What condition is C.difficile primarily responsible for in patients who have undergone antibiotic therapy?

Pseudomembranous colitis Signup and view all the answers

Which of the following is NOT recommended for treating food poisoning?

Antibiotic therapy Signup and view all the answers

What diagnostic method confirms C.difficile disease in a patient with compatible clinical symptoms?

Toxin detection in stool Signup and view all the answers

What is a characteristic feature of C.difficile when grown in culture?

It is a large, anaerobic rod that forms spores. Signup and view all the answers

Which of the following antibiotics is commonly used for managing severe diarrhea and colitis caused by C.difficile?

Metronidazole Signup and view all the answers

What is the primary source of infection for Listeria monocytogenes?

Consumption of contaminated food Signup and view all the answers

What is a common symptom of antibiotic-associated diarrhea caused by C.difficile?

Mild watery diarrhea Signup and view all the answers

Which group of individuals is NOT considered at higher risk for listeriosis?

Healthy adults Signup and view all the answers

What mechanism does Listeria use to avoid detection by the immune system after entering host cells?

Moving cell-to-cell without exposure Signup and view all the answers

What symptom might pregnant women experience due to listeriosis?

Nonspecific influenza-like symptoms Signup and view all the answers

How does Listeria monocytogenes initially adhere to epithelial cells?

Using cell wall surface proteins Signup and view all the answers

What is a potential consequence of listeriosis in newborns if acquired during pregnancy?

Abortion or stillbirth Signup and view all the answers

What type of organism is Listeria monocytogenes classified as?

Facultatively anaerobic Gram positive rod Signup and view all the answers

What can occur if listeriosis is contracted shortly after birth?

Sepsis or meningitis Signup and view all the answers

What is the common presentation of Listeria infections in healthy adults?

Mild influenza-like illness Signup and view all the answers

What type of organism is Corynebacterium diphtheriae?

Aerobic, nonmotile, non-spore forming Signup and view all the answers

Which microbiological feature helps to identify Corynebacterium species under microscopy?

Metachromatic granules arrangement Signup and view all the answers

Which of the following is the major virulence factor of C. diphtheriae?

Diphtheria toxin Signup and view all the answers

What is the initial method of disease manifestation in diphtheria?

Localized damage in the pharynx Signup and view all the answers

Which treatment combination is recommended for serious Listeria infections?

Gentamicin with penicillin or ampicillin Signup and view all the answers

What structural characteristic is commonly associated with Corynebacterium cells?

Irregular clumps or short chains Signup and view all the answers

What is a common symptom associated with diphtheria as the disease progresses?

Thick pseudomembrane formation Signup and view all the answers

What is a primary virulence factor of Clostridium perfringens?

Production of α-toxin Signup and view all the answers

Which treatment method is effective for neutralizing unbound toxin of Clostridium perfringens?

Passive immunization with antitoxins Signup and view all the answers

Which of the following methods is not effective in preventing Clostridium perfringens infections?

Destroying spores in food Signup and view all the answers

What is a common symptom of soft-tissue infections caused by Clostridium perfringens?

Intense pain with skin discoloration Signup and view all the answers

How does the enterotoxin of Clostridium perfringens contribute to food poisoning?

By promoting spore germination in the intestine Signup and view all the answers

What laboratory technique is used for the diagnosis of Clostridium perfringens?

Gram staining of clinical specimens Signup and view all the answers

Which of the following statements about Clostridium perfringens is true?

It is capable of forming spores. Signup and view all the answers

What is the typical mortality range associated with myonecrosis caused by Clostridium perfringens?

40-100% Signup and view all the answers

Which of the following organisms is known for producing a prominent polypeptide capsule composed of poly-D-glutamic acid?

Bacillus anthracis Signup and view all the answers

Which Gram positive rods are non-sporulating?

Listeria Signup and view all the answers

What are the primary methods of transmission for anthrax in humans?

Contact with contaminated herbivores or animal products Signup and view all the answers

Which of the following factors is NOT associated with virulent strains of Bacillus anthracis?

Hemolysin production Signup and view all the answers

Bacillus species can be found in which of the following environments?

In soil, water, and vegetation worldwide Signup and view all the answers

Which type of Bacillus is known to be a common commensal of herbivores?

Bacillus cereus Signup and view all the answers

What is a distinguishing characteristic of the bacterial spores formed by members of the genus Bacillus?

They do not exceed the diameter of the bacterial cell Signup and view all the answers

Which of the following organisms is NOT classified as a Gram positive rod?

Escherichia coli Signup and view all the answers

Study Notes

Gram Positive Rods

Bacillus, Clostridia, Listeria, Corynebacterium are gram-positive rods.
Bacillus includes species like B. anthracis.
Clostridia species encompass C. tetani, C. botulinum, C. perfringens, and C. difficile.
Listeria includes L. monocytogenes.
Corynebacterium includes C. diphtheriae.

Bacillus

Gram-positive rods, large, arranged singly or in long chains.
Endospore-formers and toxin-producers.
Aerobic or facultative anaerobic, nonmotile or motile, nonhemolytic rods.
Ubiquitous in nature (vegetation, water, soil).
Involved in biological cycles of carbon/nitrogen.
The family Bacillaceae is diverse, including some strains commensal to herbivores, and some that infect humans.
Clinically relevant strains for humans include Bacillus anthracis and Bacillus cereus.
Spore diameter does not exceed the bacterial cell diameter in this genus.

Bacillus anthracis

Gram-positive rod, spore-forming.
Virulent strains have a polypeptide capsule (poly-D-glutamic acid) encoded by a plasmid (pXO2).
Virulent strains carry genes for three toxic protein components on a large plasmid (pXO1) : PA (protective antigen), EF (edema factor), and LF (lethal factor).

Anthrax (Charcoal)

Zoonotic disease affecting herbivores (cattle, sheep, goats, deer) primarily.
Humans are infected by ingesting contaminated vegetation, water, or soil or through exposure to contaminated animals or animal products (meat, wool).
Anthrax has three types: cutaneous, inhalational, and intestinal.
The disease is characterized by symptoms that depend on how anthrax spores enter the body.

Anthrax Transmission

Human disease acquired through one of three routes: inoculation of spores through exposed skin, ingestion of spores, inhalation of spores.
Inhalation is the most likely route for biological weapons.

Cutaneous Anthrax

Painless papule at site of inoculation.
Rapidly progresses to ulcer then necrotic eschar.
Extensive surrounding edema/inflammation is hallmark.
Case fatality: 20% without treatment; less than 2% with antimicrobial therapy.

Gastrointestinal Anthrax

Ulcers form at the site of invasion (mouth, esophagus, intestine).
First symptoms: nausea, vomiting, malaise, which progress to systemic disease.
Almost 100% fatal without treatment.

Inhalation Anthrax

Spores reach lower airways and mediastinal lymph nodes.
Initial symptoms nonspecific: fever, myalgia, nonproductive cough, malaise.
Second stage dramatic; rapidly worsening fever, edema, massive enlargement of mediastinal lymph nodes, respiratory failure, sepsis.
Almost all cases progress to shock and death within 3 days of initial symptoms, unless treatment is initiated immediately.
Virulence is very high in absence of treatment.

Laboratory Diagnosis

Microscopy: Gram stain with observation of rods arranged singly or in long chains in biological specimens (skin lesions, oropharyngeal ulcers, blood, respiratory secretions).
Culture: Colonies readily grow in blood agar plates, large, nonpigmented, with a dry "ground-glass" surface and irregular edges.
B. anthracis colonies have a characteristic "Medusa Head" appearance with irregular edges and comma projections.

Treatment of B. anthracis infection

Prior to 2001, penicillin was the first-line treatment.
Current recommendation: ciprofloxacin or doxycycline combined with other antibiotics (rifampin, vancomycin, penicillin, imipenem, clindamycin, clarithromycin).
Exposure to antibiotics should last the full 60 day course.

Clostridium

Anaerobic Gram-positive rods capable of forming endospores.
Ubiquitous in soil, water, and sewage.
Part of the normal microbial population in the gastrointestinal tracts of animals and humans.
Most are harmless saprophytes, some are recognized pathogens.

Clostridium tetani

Large, motile, spore-forming rod.
Vegetative form extremely susceptible to oxygen toxicity, but sporulates (forms spores) readily and survives in the environment for a long time.
Virulence factor: production of two toxins: tetanolysin (oxygen-labile hemolysin; unknown clinical significance); and tetanospasmin (plasmid-encoded, heat-labile neurotoxin→ tetanus).
The disease is characterized by muscle spasm and involvement of the autonomous nervous system.

Tetanospasmin

Neurotoxin produced during the stationary phase of growth, released when the cell is lysed.
Responsible for the clinical manifestations of tetanus.
A-B toxin cleaved by endogenous proteases.
The two parts remain together up to spinal cord transportation
A (zinc-endopeptidase) portion inactivates proteins that regulate the release of glycine and GABA.
This leads to unregulated excitatory synaptic activity in motor neurons → spastic paralysis.

Clostridium tetani Infection

Spores penetrate through skin wounds, burns, animal bites (splinter wounds are particularly dangerous).
Germination of spores and neurotoxin production occurs after 24-36 hours under anaerobic conditions.

Generalized Tetanus

Most common form.
Incubation period 3-21 days.
Symptoms include headache, mild fever, irritability, pain near the wound, trismus (lockjaw), difficulty opening the mouth due to spastic paralysis of the masseter muscle ("risus sardonicus").
In addition, painful contraction at level of cervical musculature and of the trunk with a hyperextension contracture and a typical postural attitude.
Other symptoms include thoracic and laryngeal spasms, respiratory failure, cardiac arrhythmias, potentially leading to death.
Mortality rate: 30% - 50%.

Neonatal Tetanus

Typically associated with initial infection of the umbilical stump (following nonsterile delivery).
Progresses to become generalized.
Develops 4-14 days after birth.
Mortality rate exceeding 90% in infants.

Clostridium botulinum

Heterogeneous collection of fastidious, spore-forming anaerobic rods.
C. botulinum includes various strains producing distinct botulinum toxins (at least 7).
Spores/neurotoxins can be present in home-made preserves, bad food refrigeration, and honey.
Spores are common in the environment and can contaminate foods.
Anaerobic conditions allow spores to germinate and produce botulinum neurotoxin.

Botulinum Neurotoxin (A-B toxin)

Present in contaminated food, absorbed in the intestine.
Complexed with nontoxin proteins; not inactivated by proteolytic enzymes through the digestive tract..
B subunit binds motor neurons; A subunit (zinc-endopeptidase) inactivates proteins that regulate the release of acetylcholine (ACh) in peripheral nervous system presynapses (neuromuscular junction) → flaccid paralysis.

Classic/Foodborne Botulism

Associated with consumption of home-canned food contaminated with toxins.
Symptoms begin 6–days after ingestion, depending on the dose of ingested toxin.
Clinical manifestations range from mild symptomotaology to severe cases (fatal ~5%).
Symptoms: diplopia, difficulty in speech and in swallowing; muscle weakness progressing from the shoulders to the trunk and lower limbs, respiratory paralysis.

Infant Botulism

Associated with consumption of foods (honey, infant milk powder) contaminated with spores.
Spores germinate and colonize the gastrointestinal tract; multiply and produce toxins in vivo.
Proliferation is achieved because of competitors absence.
Initial symptoms are nonspecific: constipation, weak cry.
Then flaccid paralysis and respiratory arrest followed by mortality rate less than 2%.

Wound Botulism

Rare disease with unknown incidence.
Toxin produced by bacteria in contaminated wounds.
Symptoms similar to foodborne botulism, but incubation period is longer (>4 days).

Inhalation Botulism

Major concern in the era of bioterrorism.
Aerosolization of the neurotoxin as a biological weapon.
Rapid onset and potentially high mortality.

Botulism Diagnosis, Treatment, and Prevention

Clinical diagnosis confirmed by toxin detection in implicated food or patient's serum/feces.
Cultures of heated specimens on enriched anaerobic media allow spore germination.
Treatment: adequate ventilatory support; elimination of the organism from the gastrointestinal tract.
Use of penicillin or metronidazole to kill bacteria and reduce toxin production; passive immunization with trivalent botulinum antitoxins (A, B, and E) to neutralize unbound toxin.
Prevention: Destroy spores in food (virtually impossible), prevent spore germination, destroy preformed toxin by heating food at 60–100°C for 10 min.

Listeria monocytogenes

Facultatively anaerobic Gram-positive rod with flagella.
Short rod (coccobacillus), sometimes in pairs or short chains.
Grows in wide range of temperatures, pH, and high salt concentration.
Facultative intracellular pathogen, ubiquitous in nature (soil, vegetation, water, and gastrointestinal tracts of animals).
Not found in humans.
Associated with diseases in: pregnant women/neonates, elderly, and patients with defective cellular immunity.
Foodborne pathogen (contaminated food).
Undercooked or processed meats, unpasteurized/contaminated milk or cheese, unwashed raw vegetables.

Listeria monocytogenes Infection

Enter gastrointestinal tract after contaminated food ingestion.
Adhere to epithelial cells via internalin A (cell wall surface protein).
Induce phagocytosis by epithelial cells.
Inside the infected cells, listeriolysin O and two phospholipases C enzymes are produced.
Release into the cytosol of infected cells.
Replicates by intracellular spread (cell-to-cell).
Enters macrophages.
Spreads via lymph nodes blood vessels to splean and liver.
Dissemination of disease.

Listeria monocytogenes: Life Cycle in Host Cells

Bacteria undergo phagocytosis.
Lysis of phagolysosome.
Proliferation.
Cell-to-cell spread via filopods.
Repeated cycles.

Listeria monocytogenes: High-Risk Groups

Pregnant women (nonspecific influenza-like symptoms), newborns (acquired during pregnancy; early or late onset disease) → abortion, stillbirth, premature birth, or formation of abscesses and granulomas in multiple organs.
Elderly and immunocompromised patients: sepsis, meningitis, meningoencephalitis.
Listeria infections in healthy adults are typically asymptomatic or mild influenza-like illness (self-limiting gastroenteritis, headache, myalgias, and arthralgias).

Listeria: Laboratory Diagnosis & Treatment

Microscopy: Gram stain reveals short rods (coccobacilli).
Culture: Grows on most conventional media; small colonies with beta-hemolysis on blood agar plates (distinguish from streptococci).
Cold enrichment for culture from food.
Treatment: Gentamicin with penicillin or ampicillin for serious infections (septicemia and meningitis).
Trimethoprim-sulfamethoxazole.

Corynebacterium spp.

Includes over 100 species.
Gram-positive bacteria, irregular shape, clumps or short chains.
Aerobic or facultatively anaerobic.
Motile, non-spore-forming, and club-shaped.
Commonly found in soil, water, human skin and respiratory tract.
Most important is C. diphtheriae (etiologic agent of diphtheria) in which humans are the only reservoir.
Corynebacteria often display metachromatic granules (containing phosphates, lipids, RNA) at the ends of the bacterial cell.
Microscopy shows appearance resembling "Chinese letters".

Corynebacterium diphtheriae

Major virulence factor: diphtheria toxin.
Tox gene introduced by a lysogenic bacteriophage (β-phage).
Diphtheria toxin inhibits protein synthesis.
Receptor is heparin-binding epidermal growth factor (present in many cell types, especially heart and nerve cells).

Diphtheria: Respiratory Infection

Bacteria enter through the respiratory tract, multiply locally on epithelial cells in the pharynx.
Causes damage, malaise, sore throat, exudative pharyngitis, and low-grade fever.
Exudate develops into thick pseudomembrane of bacteria, lymphocytes, plasma cells, fibrin and dead cells.
Toxin spreads through the blood and noncontiguous anatomical sites, leading to severe systemic disease, primarily involving the heart (myocarditis) and nervous system (neuropathy, dysphagia, paralysis).

Diphtheria: Cutaneous Infection

Involves invasion of organism from the patient's skin into subcutaneous tissue.
Develops a papule at the site of contact; later covered by a greyish membrane.
Similarly to respiratory diphtheria, a systemic response occurs, especially with fever.
Also affects the heart and nervous system.

Diphtheria: Laboratory Diagnosis, Therapy, & Prevention

Microscopy: Gram stain preparation on pseudomembrane, respiratory swabs, cutaneous lesions.
Culture: Bacteria cultured on Loffler medium and selective agar plates (e.g., cysteine-tellurite blood agar, colistin-nalidixic agar).
Treatment: Penicillin or erythromycin to eliminate C. diphtheriae, terminate toxin production.
Early administration of diphtheria antitoxin to specifically neutralize the exotoxin before it binds to the epithelial cells.
Prevention: Vaccination is the best way.

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Test your knowledge on infectious diseases, focusing specifically on anthrax and C.difficile infections. This quiz covers transmission routes, symptoms, diagnostic methods, and treatment options associated with these diseases. Perfect for students and professionals in the medical field.