Microbiology Final 2 Tahani

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Questions and Answers

Which of the following bacteria is known to form filamentous forms or hyphae in clinical specimens?

Bifidobacterium

Mobiluncus

Eubacterium

Actinomyces (correct)

What characterizes the infections caused by Actinomyces organisms?

They produce chronic granulomatous lesions that form abscesses. (correct)

They are acute and easily transmissible between individuals.

They are exclusively found in respiratory tract infections.

They primarily affect the skin and are easily treatable.

Which of these statements about Actinomyces is true?

Actinomyces organisms can take over two weeks to grow in culture. (correct)

Actinomyces infections are primarily exogenous.

Actinomyces is a commonly present organism on the skin surface.

Actinomyces is classified under non-anaerobic bacteria.

What type of tracts are formed in actinomycosis infections?

Sinus tracts Signup and view all the answers

Which of the following genera is less likely to cause human disease despite being isolated in clinical specimens?

Lactobacillus Signup and view all the answers

What is the main effect of the toxin produced by Corynebacterium diphtheriae on host cells?

It ADP-ribosylates and inactivates eEF-2, disrupting protein synthesis. Signup and view all the answers

Which symptom is NOT associated with the respiratory diphtheria described?

Severe abdominal pain Signup and view all the answers

What characteristic of anaerobic gram-positive cocci is identified in the context of infections?

They thrive in normally sterile sites when they spread from colonized areas. Signup and view all the answers

What has contributed to the decline of diphtheria cases in the United States since 2003?

The establishment of a robust immunization program. Signup and view all the answers

Which of the following statements is true regarding Peptostreptococcus species infections?

They tend to occur more often in chronic infection scenarios. Signup and view all the answers

What type of bacteria is Propionibacterium acnes classified as?

Obligate anaerobic gram-positive rods Signup and view all the answers

Which characteristic is NOT associated with Mobiluncus?

Presence of endotoxin Signup and view all the answers

Which population is NOT primarily at risk for Listeria monocytogenes infection?

Healthy adults Signup and view all the answers

How does Listeria monocytogenes appear microscopically?

As single, short rods Signup and view all the answers

What is the primary habitat for Bifidobacterium and Eubacterium?

Oropharynx, large intestine, and vagina Signup and view all the answers

Which statement regarding Listeria monocytogenes is false?

It is motile only at 37°C. Signup and view all the answers

Which antibiotic is Listeria monocytogenes NOT resistant to?

Ampicillin Signup and view all the answers

What type of pathogens can non-spore forming aerobic gram-positive rods be categorized into?

Human and animal pathogens, plus opportunistic pathogens Signup and view all the answers

What role does internalin A play in the pathogenesis of Listeria monocytogenes?

It mediates the adherence of the bacteria to host cells. Signup and view all the answers

Which of the following best describes the mechanism by which Listeria monocytogenes avoids antibody-mediated clearance?

It can replicate in macrophages and evade immune detection. Signup and view all the answers

What is the main transmission route of Corynebacterium diphtheriae?

Airborne respiratory droplets. Signup and view all the answers

Which aspect of the immune system is particularly important in preventing severe infections from Listeria monocytogenes?

Cellular immunity. Signup and view all the answers

What are the primary clinical manifestations of early-onset neonatal disease caused by Listeria monocytogenes?

Abortion, stillbirth, or premature birth. Signup and view all the answers

What distinguishes the A-B exotoxin produced by Corynebacterium diphtheriae?

It has a receptor-binding region on the B subunit. Signup and view all the answers

What is the common characteristic of Corynebacterium diphtheriae in terms of its physical structure?

It is a pleomorphic rod. Signup and view all the answers

During which trimester are pregnant women most susceptible to Listeria monocytogenes infections?

Third trimester. Signup and view all the answers

What condition should prompt a physician to consider actinomycosis?

Tissue swelling with fibrosis and draining sinus tracts Signup and view all the answers

Which of the following sites is NOT a major site of actinomycosis?

Central nervous system Signup and view all the answers

What is the likely cause of abdominal and pelvic actinomycosis infections?

Intrauterine contraceptive devices and surgical procedures Signup and view all the answers

Which of the following statements about Nocardia is true?

Nocardia demonstrates weak acid-fastness Signup and view all the answers

What is the primary virulence factor of pathogenic strains of Nocardia?

Inhibition of phagocytic cell activity Signup and view all the answers

What are the initial symptoms of bronchopulmonary disease caused by Nocardia?

Colonization of the upper respiratory tract Signup and view all the answers

What combination of characteristics is unique to the genus Nocardia?

Presence of aerial hyphae and acid-fastness Signup and view all the answers

What is often required in the treatment of actinomycosis?

Surgical debridement and prolonged antibiotics Signup and view all the answers

What is the primary characteristic of Mycetoma caused by Nocardia?

A chronic suppurative disease characterized by a triad of tumor, fistulas, and grains Signup and view all the answers

Which scenario is NOT a common setting for Lactobacillus species to invade into the bloodstream?

Post-gastrointestinal surgery Signup and view all the answers

In which patients is a comprehensive immunologic workup indicated when diagnosed with pulmonary or disseminated Nocardia infections?

Patients without any underlying disease Signup and view all the answers

What is the primary clinical outcome associated with advanced Mycetoma infections in regions lacking adequate health care?

Amputation as the only treatment option Signup and view all the answers

Which of the following statements regarding Propionibacterium acnes is accurate?

It is responsible for acne vulgaris and opportunistic infections Signup and view all the answers

Which of the following is true about Lactobacillus species?

They are often dominant in the female genital tract Signup and view all the answers

What is a notable feature of Nocardia infections in terms of clinical progression?

They often disseminate to the brain causing abscesses Signup and view all the answers

What is the main reason for late presentation of Mycetoma in endemic areas?

Lack of health education and medical facilities Signup and view all the answers

Study Notes

Introduction to Microbiology

Lecture 20 covers pathogens like non-spore-forming Gram-positive rods (aerobic and anaerobic) and anaerobic gram-positive cocci.

Overview of Gram Positive Species

Gram-positive species are categorized into rods and cocci, with spore-formers and non-spore-formers.
Facultative anaerobes, as well as aerobic and anaerobic, are included.
Specific examples of bacteria are listed, including Corynebacterium, Actinomyces, Propionibacterium, Lactobacillus, Bacillus, Clostridium, Bifidobacterium, Eubacterium, Micrococcus, Staphylococcus, Streptococcus, Gemella, and Peptostreptococcus.
Important characteristics like catalase-positive/negative are noted for various species.

Overview of Bacteria

Charts and diagrams visually illustrate the taxonomy of Gram-positive bacteria.
Key characteristics such as motility, hemolysis, and antibiotic susceptibility are noted in the figures.
Staphylococcus, Streptococcus, Corynebacterium, Clostridium, Listeria, and Bacillus are all separately presented, highlighting their distinguishing features.

Actinomyces

Actinomyces are facultatively anaerobic or strictly anaerobic gram-positive rods.
They grow slowly in culture and often cause chronic, slowly developing infections.
Infections typically occur in the upper respiratory tract, gastrointestinal tract, and female genital tracts.
Infections are usually endogenous, rather than communicable.
They typically form filamentous forms or hyphae, resembling fungi in appearance.
Common locations of infection include cervicofacial areas following dental procedures or oral trauma.
Actinomycosis is the name given to the disease.
Diagnosis, symptoms (including sinus tracts), and treatment are discussed in the context of disease management.

Nocardia

Nocardia are strict aerobic rods that form branched filaments in tissues and culture.
Distinguishable by their weakly acid-fast properties.
Infections are generally exogenous, meaning caused by organisms that are not typically part of the normal human flora.
Nocardia infections are commonly found in individuals with weakened immune systems.
A key feature of Nocardia is a combination of aerial hyphae and acid-fastness, crucial for identification.
This organism can cause severe infections (e.g., bronchopulmonary disease) following inhalation and occurs almost exclusively in immunocompromised patients.
Nocardia is more commonly found in soil with high organic matter content, and more cases occur in the context of immunocompromised patients.

Lactobacillus

Lactobacillus species are facultatively anaerobic or strictly anaerobic rods.
They ferment to produce lactic acid.
Commonly part of the normal flora in the mouth, stomach, intestines, and genitourinary tract, especially in the female genital tract.
Rarely cause infections; indeed, some forms are used in probiotics and starter cultures for yogurt, cheese, sauerkraut, etc.
Lactobacillus species can sometimes cause bacteremia or more severe conditions such as endocarditis in immunocompromised patients.

Propionibacterium

Propionibacterium are small gram-positive rods.
Found on skin, conjunctiva, external ear, and oropharynx, and female genital tract.
The primary species is Propionibacterium acnes.
Plays a role in acne pathogenesis and opportunistic infections in patients with prosthetic devices or intravascular lines.
P. acnes colonization of the skin is necessary but not sufficient for the development of acne vulgaris, suggesting additional factors are critical for the expression of the disease.

Mobiluncus, Bifidobacterium, and Eubacterium

Mobiluncus, Bifidobacterium, and Eubacterium are commonly found in areas like the oropharynx, large intestine, and vagina.
Mobiluncus sometimes shows up in women with bacterial vaginosis, and is often an incidental finding.
Mobiluncus have a gram variable or gram negative profile.
Bifidobacterium and Eubacterium are commonly found in the oropharynx, intestine, and vagina.
They are normally considered relatively benign contaminants of human specimens.

Non-spore-forming Aerobic Gram-Positive Rods

This group includes Listeria monocytogenes, Corynebacterium diphtheriae, and others.
Some are significant human pathogens (e.g., Listeria). Others include pathogens that commonly infect animals and can sometimes cause disease in humans (e.g. Erysipelothrix rhusiopathiae).
Some are opportunistic pathogens (e.g., Corynebacterium jeikeium) and commonly affect people with weakened immune systems.

Listeria monocytogenes

Listeria monocytogenes are short, non-branching, and gram-positive bacteria.
Motile at room temperature but less motile at 37 degrees Celsius.
Produces beta-hemolysis on sheep blood agar.
A common cause of infection with a primary source being contaminated food leading to Foodborne Listeriosis.
Pathogen can be transmitted from mother to child in utero.
Most affected patient populations include neonates, the elderly, pregnant women, and others with weakened immune systems.
It is a facultative intracellular pathogen.
Key virulence mechanisms involve interacting with host cells via proteins, penetrating and multiplying within cells, and avoiding immune responses.

Corynebacterium diphtheriae

Corynebacterium diphtheriae are irregularly staining, pleomorphic rods which are aerobic or facultatively anaerobic.
They are ubiquitous in plants, animals, and humans.
The primary virulence factor is diphtheria toxin (an A-B exotoxin).
This toxin inhibits protein synthesis in host cells.
Human-to-human transmission is the only known reservoir for the organism, typically via respiratory droplets and skin contact, and disease presentation begins with malaise and sore throat.

Anaerobic Gram-Positive Cocci

Anaerobic gram-positive cocci are commonly found in the oral cavity, gastrointestinal tract, genitourinary tract, and skin.
Infections typically happen when the bacteria spread from these locations to normally sterile regions within the body.
Peptostreptococcus species are frequently found in subcutaneous abscesses, soft tissue infections, and diabetic foot ulcers, but also cause chronic infections with other pathogens.
Often, infections with many Peptostreptococcus species are synergistic with other organisms.

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Description

Test your knowledge about Actinomyces and related bacteria with this quiz. Explore key characteristics of infections they cause and identify true statements related to this genus. Perfect for microbiology students and professionals seeking to enhance their understanding of clinical specimens.