Set 2 Flashcards
1
Q
A
2
Q
What is Listeria monocytogenes, and where is it commonly found?
A
- Gram-positive, facultative anaerobic bacillus.
- Motile at 22-25°C with “rocket-like” tumbling motility.
- Commonly found in soil, water, vegetables, and animal products.
- Can survive and grow in refrigerated conditions.
3
Q
What diseases are primarily caused by Listeria monocytogenes?
A
- Listeriosis: Can manifest as:
- Septicemia: Bloodstream infection.
- Meningitis: Inflammation of the membranes surrounding the brain and spinal cord.
- Fetal Infections: Including miscarriage, stillbirth, or neonatal sepsis.
- Gastroenteritis: Mild infection with diarrhea and vomiting, mainly in immunocompromised individuals.
4
Q
How is Listeria monocytogenes transmitted?
A
- Foodborne Route: Consumption of contaminated foods such as:
- Unpasteurized dairy products.
- Soft cheeses.
- Raw vegetables.
- Processed meats (e.g., deli meats, hot dogs).
- Vertical Transmission: From mother to fetus during pregnancy.
- Person-to-Person: Rare, primarily via direct contact with infected individuals.
5
Q
What are the clinical features of listeriosis?
A
- Septicemia and Meningitis:
- Fever, muscle aches, confusion.
- Neck stiffness, headache, loss of balance.
- Fetal Infections:
- Miscarriage, stillbirth, or neonatal sepsis.
- Gastroenteritis:
- Diarrhea, abdominal pain, vomiting.
6
Q
What are the risk factors for developing Listeria monocytogenes infection?
A
- Pregnancy: Increased susceptibility; can affect the fetus.
- Elderly Individuals: Weakened immune systems.
- Immunocompromised Persons: Including those with HIV/AIDS, cancer, or on immunosuppressive therapy.
- Newborns: Particularly premature or low birth weight infants.
- Consumption of High-Risk Foods: Such as unpasteurized dairy products and processed meats.
7
Q
How is Listeria monocytogenes infection diagnosed?
A
- Clinical Evaluation: Based on symptoms and risk factors.
- Laboratory Tests:
- Blood Cultures: Positive in cases of septicemia.
- Cerebrospinal Fluid (CSF) Analysis: For meningitis diagnosis.
- Stool Culture: In cases of gastroenteritis.
- Molecular Methods: PCR for rapid and specific identification.
8
Q
What treatments are effective against Listeria monocytogenes infections?
A
- Antibiotic Therapy:
- Ampicillin: First-line treatment.
- Gentamicin: Often combined with ampicillin for synergistic effect.
- Vancomycin: Alternative for those allergic to beta-lactams.
- Supportive Care: Includes hydration and management of symptoms.
- Antibiotic Duration: Typically 2-3 weeks for invasive infections.
9
Q
What are the prevention measures for Listeria monocytogenes infections?
A
- Food Safety Practices:
- Proper Cooking: Thoroughly cook meat and poultry.
- Pasteurization: Use pasteurized dairy products.
- Refrigeration: Maintain adequate cold storage to inhibit bacterial growth.
- Avoid High-Risk Foods: Especially for pregnant women and immunocompromised individuals.
- Hygiene:
- Handwashing: After handling raw foods.
- Cross-Contamination Prevention: Use separate utensils and surfaces for raw and cooked foods.
- Public Health Measures:
- Surveillance and Monitoring: To detect and control outbreaks.
- Education: Informing high-risk populations about safe food practices.
10
Q
What are the key virulence factors of Listeria monocytogenes?
A
- Internalin Proteins (InlA and InlB): Facilitate entry into host cells.
- ActA Protein: Promotes actin-based motility for cell-to-cell spread.
- Listeriolysin O (LLO): Pore-forming toxin that allows escape from phagosomes.
- Phospholipases: Aid in membrane disruption and spread within tissues.
- Capsular Polysaccharides: Enhance immune evasion.
11
Q
What are the public health implications of Listeria monocytogenes?
A
- High-Risk Populations: Pregnant women, elderly, and immunocompromised individuals require special attention.
- Food Industry Impact: Contaminated products can lead to recalls and economic losses.
- Antibiotic Resistance Concerns: Although generally susceptible, monitoring for resistant strains is essential.
- Bioterrorism Potential: Due to its ability to cause severe disease, though less common than other pathogens.
- Surveillance Systems: Importance of monitoring and rapid response to outbreaks to minimize impact.
12
Q
What is Corynebacterium diphtheriae, and where is it commonly found?
A
- Gram-positive, non-spore-forming, club-shaped bacillus.
- Facultative anaerobe.
- Commonly found in the human respiratory tract as a colonizer.
- Can survive on dry surfaces for weeks, facilitating transmission.
13
Q
What disease is primarily caused by Corynebacterium diphtheriae?
A
- Diphtheria: A respiratory and cutaneous disease characterized by the production of diphtheria toxin.
14
Q
How is Corynebacterium diphtheriae transmitted?
A
- Person-to-Person Contact: Through respiratory droplets from coughing or sneezing.
- Contaminated Objects: Sharing personal items like towels or utensils.
- Skin Lesions: Through direct contact with infected wounds in cutaneous diphtheria.
15
Q
What are the clinical features of diphtheria?
A
- Respiratory Diphtheria:
- Pseudomembrane Formation: Greyish membrane on the tonsils, pharynx, or nasopharynx.
- Sore Throat, Fever, Swollen Glands, Difficulty Breathing.
- Systemic Effects: Myocarditis, neuropathy due to diphtheria toxin.
- Cutaneous Diphtheria:
- Ulcerative Lesions with gray membranes on the skin.
- Common in tropical regions and among immunocompromised individuals.
16
Q
What are the key virulence factors of Corynebacterium diphtheriae?
A
- Diphtheria Toxin:
- Exotoxin that inhibits protein synthesis in host cells by ADP-ribosylating EF-2, leading to cell death.
- Responsible for systemic complications like myocarditis and neuropathy.
- Pili and Adhesins: Facilitate attachment to host epithelial cells.
- Cell Wall Components: Dimorphic properties aiding in immune evasion.
17
Q
How is Corynebacterium diphtheriae infection diagnosed?
A
- Clinical Evaluation: Presence of pseudomembrane, symptoms of diphtheria.
- Laboratory Tests:
- Culture: Grows on Loeffler’s medium or Tellurite agar (gray colonies).
- PCR: Detection of tox gene encoding diphtheria toxin.
- Elek’s Test: Immunodiffusion assay to confirm toxin production.
- Serological Tests: Measurement of antitoxin antibodies.
18
Q
What treatments are effective against Corynebacterium diphtheriae infections?
A
- Antitoxin Administration:
- Diphtheria antitoxin: Neutralizes free toxin; must be given early.
- Antibiotic Therapy:
- Penicillin G or Erythromycin: To eliminate bacterial carriage and prevent toxin production.
- Supportive Care:
- Airway Management: In cases of airway obstruction.
- Cardiac Monitoring: For myocarditis.
- Isolation: To prevent transmission to others.
19
Q
What are the prevention measures for Corynebacterium diphtheriae infections?
A
- Vaccination:
- Diphtheria Vaccine: Part of the DTaP and Td vaccines; induces antitoxin antibodies.
- Hygiene Practices:
- Handwashing and respiratory etiquette to reduce spread.
- Surveillance and Control:
- Contact Tracing and prophylactic antibiotics for exposed individuals.
- Public Health Measures:
- Rapid Identification and isolation of cases to prevent outbreaks.
20
Q
What are the risk factors for developing diphtheria?
A
- Lack of Vaccination: Unvaccinated or incompletely vaccinated individuals.
- Close Contact with Infected Persons: Living in crowded conditions.
- Travel to Endemic Areas: Regions with low vaccination coverage.
- Weakened Immune System: Immunocompromised individuals are more susceptible.
- Poor Hygiene: Increases transmission likelihood.
21
Q
What are the public health implications of Corynebacterium diphtheriae?
A
- Outbreak Potential: Highly contagious with rapid spread in susceptible populations.
- Vaccination Programs: Essential for prevention; resurgence possible if vaccination rates decline.
- Bioterrorism Concern: Diphtheria toxin can be used as a biological weapon, necessitating preparedness.
- Healthcare Burden: Requires prompt treatment and isolation measures to control transmission.
- Global Health Disparities: Higher incidence in developing countries with limited vaccination infrastructure.
22
Q
What is Mycobacterium tuberculosis, and where is it commonly found?
A
- Gram-positive, acid-fast, slow-growing bacillus.
- Obligate Aerobe: Requires oxygen for growth.
- Environmental Presence: Primarily found in the human respiratory tract.
- Transmission: Spread through airborne droplets from infected individuals.
23
Q
What disease is primarily caused by Mycobacterium tuberculosis?
A
- Tuberculosis (TB): A chronic infectious disease affecting primarily the lungs (pulmonary TB) but can also affect other body parts (extrapulmonary TB).
24
Q
What are the key virulence factors of Mycobacterium tuberculosis?
A
- Mycolic Acids: Long-chain fatty acids in the cell wall that provide resistance to desiccation, chemicals, and immune responses.
- Cord Factor (Trehalose Dimycolate): Facilitates intracellular survival and tissue necrosis.
- ESAT-6 and CFP-10 Proteins: Involved in macrophage lysis and immune evasion.
- Phthiocerol Dimycocerosate (PDIM): Affects membrane permeability and immune modulation.
