Microbiology: Bacteria & Respiratory Pathogens
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Microbiology: Bacteria & Respiratory Pathogens

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Which of the following is NOT a part of the natural defense mechanisms in the respiratory system?

  • Natural anti-microbial substances
  • Ciliated respiratory epithelium
  • Immunosuppressive therapy (correct)
  • Mucus-producing cells lining the bronchi

    • Which condition is a predisposing factor for serious infection or pneumonia?

  • High protein diet
  • Regular exercise
  • Diabetes (correct)
  • Hydration

    • What is the common name for Pneumocystis jiroveci, which affects immunocompromised patients?

  • Streptococcus pneumoniae
  • P. carinii (correct)
  • Haemophilus influenzae
  • Candida albicans

    • Which type of upper respiratory tract infection is life-threatening but now controlled due to vaccination?

    <p>Epiglottitis</p> Signup and view all the answers

    Which statement about the normal microbial flora in the lungs is true?

    <p>The lungs are considered to be sterile.</p> Signup and view all the answers

    Which of the following is a common type of virus that can cause respiratory diseases?

    <p>Influenza</p> Signup and view all the answers

    Which immune cells are important for defense against infections in the lungs?

    <p>Pulmonary macrophages</p> Signup and view all the answers

    Which of the following populations is at increased risk for respiratory infections?

    <p>Aged individuals</p> Signup and view all the answers

    Which of the following bacterial pathogens is most commonly associated with community-acquired pneumonia?

    <p>Mycoplasma pneumoniae</p> Signup and view all the answers

    Which of the following represents a less common cause of pneumonia due to animal or environmental exposure?

    <p>Coxiella burnetii</p> Signup and view all the answers

    What type of bacteria is often responsible for nosocomial pneumonia?

    <p>Gram-negative rods</p> Signup and view all the answers

    Which bacterial pathogen is known to cause tuberculosis?

    <p>Mycobacterium tuberculosis</p> Signup and view all the answers

    What is the primary cause of pneumonia from human-to-human transmission?

    <p>Chlamydophila pneumoniae</p> Signup and view all the answers

    Which of the following is NOT a common cause of pneumonia from environmental exposure?

    <p>Streptococcus pyogenes</p> Signup and view all the answers

    Which bacteria are considered potential agents of bioterrorism that can cause pneumonia?

    <p>Francisella tularensis and Yersinia pestis</p> Signup and view all the answers

    Identify the correct classification of pneumonia caused by Staphylococcus aureus.

    <p>Nosocomial Pneumonia</p> Signup and view all the answers

    What primarily fills the bronchioles and alveoli during pneumonia?

    <p>Pus consisting of dead microbes and inflammatory cells</p> Signup and view all the answers

    Which type of pneumonia is predominantly caused by Streptococcus pneumoniae?

    <p>Typical pneumonia</p> Signup and view all the answers

    What diagnostic method is used to identify pneumonia?

    <p>Chest x-ray</p> Signup and view all the answers

    Which of the following is a less common cause of pneumonia in older adults?

    <p>Coxsackievirus</p> Signup and view all the answers

    Which virulence factor is significant for Streptococcus pneumoniae?

    <p>Capsule</p> Signup and view all the answers

    How many cases of pneumonia occur approximately per year in the USA?

    <p>2 million</p> Signup and view all the answers

    What is a characteristic of typical pneumonia, distinctly differing it from atypical pneumonia?

    <p>Commonly associated with Streptococcus pneumoniae</p> Signup and view all the answers

    Which vaccines are primarily used against Streptococcus pneumoniae?

    <p>PNEUMOVAX and PREVNAR</p> Signup and view all the answers

    What is a common symptom of classic lobar pneumonia?

    <p>Thick sputum</p> Signup and view all the answers

    Which diagnostic test is NOT used in identifying pneumococcal pneumonia?

    <p>Blood glucose test</p> Signup and view all the answers

    What does the outer capsule of Haemophilus influenzae primarily consist of?

    <p>Polyribitol phosphate</p> Signup and view all the answers

    How is the diagnosis of pneumococcal pneumonia primarily confirmed?

    <p>Sputum gram stain and culture</p> Signup and view all the answers

    Which capsular serotype of Haemophilus influenzae is most commonly associated with infections?

    <p>Type b</p> Signup and view all the answers

    What describes the appearance of Haemophilus influenzae in a Gram stain?

    <p>Pleomorphic gram-negative rods</p> Signup and view all the answers

    In the pathogenesis of pneumococcal pneumonia, what follows after the alveoli become filled with edema fluid?

    <p>Massive infiltration of PMNs</p> Signup and view all the answers

    Which of the following is NOT a common disease caused by pneumococcus?

    <p>Gastroenteritis</p> Signup and view all the answers

    What color do gram-negative bacilli, such as Klebsiella pneumoniae, typically stain?

    <p>Pink</p> Signup and view all the answers

    Which characteristic makes Klebsiella pneumoniae difficult to treat with antibiotics?

    <p>Capsule formation</p> Signup and view all the answers

    Which patient groups are predominantly affected by pneumonia caused by Klebsiella pneumoniae?

    <p>Alcoholics and diabetics</p> Signup and view all the answers

    What color do colonies of Pseudomonas aeruginosa appear on MacConkey agar?

    <p>Colorless</p> Signup and view all the answers

    What significant symptom was observed in the patient with pneumonia in the clinical case?

    <p>Rust-colored sputum</p> Signup and view all the answers

    Which feature distinguishes Pseudomonas aeruginosa from Klebsiella pneumoniae?

    <p>It is oxidase-positive.</p> Signup and view all the answers

    Which condition is commonly associated with Pseudomonas aeruginosa infections?

    <p>Cystic fibrosis</p> Signup and view all the answers

    What does the presence of crackles and rhonchi in the pulmonary exam typically indicate?

    <p>Fluid or infection in the lungs</p> Signup and view all the answers

    Which group is most likely to experience pneumonia as a complication of flu infections?

    <p>Elderly individuals and those with pulmonary disease</p> Signup and view all the answers

    What is a key characteristic that differentiates Mycoplasma pneumoniae from other bacteria?

    <p>It has no cell wall</p> Signup and view all the answers

    What is the primary diagnostic method for Mycoplasma pneumoniae infections?

    <p>Clinical presentation and serology or molecular techniques</p> Signup and view all the answers

    Which complication is least likely associated with Mycoplasma pneumoniae?

    <p>Meningitis</p> Signup and view all the answers

    What is a significant characteristic of Bordetella pertussis?

    <p>It is a fragile gram-negative coccobacillus</p> Signup and view all the answers

    What is a major reason for the rarity of whooping cough today?

    <p>Widespread use of vaccinations</p> Signup and view all the answers

    During which stage of whooping cough is the patient most likely to experience severe coughing fits?

    <p>Paroxysmal stage</p> Signup and view all the answers

    What role do cold hemagglutinins play in diagnosing Mycoplasma pneumoniae?

    <p>They react with red blood cells in a laboratory test</p> Signup and view all the answers

    Study Notes

    Microbiology: Bacteria 1 – Respiratory Pathogens 1

    • Lecture objectives include differentiating and describing the roles of epidemiology, microbial virulence factors, and host-defense mechanisms in respiratory infections.
    • Objectives also include differentiating bacterial pathogens based on unique microbiologic features, with an emphasis on pneumonia-causing bacteria.
    • Objectives further include differentiating tests to identify disease-causing bacteria for clinical diagnosis.

    Classification of Pneumonia/Pneumonia-like Syndromes by Bacteria

    • Acute/Community-acquired: Bacteria causing person-to-person or autologous pneumonia include Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Streptococcus pyogenes, Staphylococcus aureus, Klebsiella pneumoniae, and Chlamydophila pneumoniae.
    • Animal/Environmental Exposure: Somewhat less common causes include Legionella pneumophila (from heating/cooling systems), Francisella tularensis (rabbits/ticks), Coxiella burnetii (farm animals), Chlamydophila psittaci (exotic birds), and Yersinia pestis (the plague – fleas/rats). 
    • Acute/Nosocomial: Enteric bacteria (e.g., Klebsiella), Pseudomonas, Acinetobacter, and Staphylococcus aureus are involved in hospital-acquired pneumonia.

    Subacute/Chronic Pneumonia

    • Atypical Mycobacteria and various fungi are associated with these types.
    • Immunocompromised patients may experience infection from atypical mycobacteria (including tuberculosis) and various fungi like Pneumocystis jiroveci (formerly P. carinii).

    Natural Defense Mechanisms

    • The respiratory tract has natural defenses: vibrissae (filter large particles), epiglottal/cough reflexes, ciliated respiratory epithelium, mucus-producing cells, and anti-microbial substances like lysozyme, lactoferrin, secretory IgA, and complement—along with pulmonary macrophages,

    Predisposing Factors to Serious Infection/Pneumonia

    • Previous viral respiratory infection
    • Allergies (dust, pollen)
    • Chronic lung diseases (emphysema)
    • Alcoholism and smoking
    • Diabetes, cancer, and other illnesses
    • Immunosuppression
    • Age extremes
    • Debility (from development/congenital anomalies, post-surgery, anaesthesia, stroke)

    Normal Microbial Flora

    • Mouth and Oropharynx: Various streptococcal bacteria (mostly viridans), Streptococcus mutans (viridans group), Streptococcus salivarius (viridans group), Streptococcus pneumoniae, Streptococcus pyogenes(Group A strept), and some yeasts (e.g., Candida albicans).
    • Lung: The lung is typically sterile; however, transient colonization with low microbial numbers is possible in healthy people, but this is not a problem until the immune system is compromised.

    Types of Upper Respiratory Tract Infections

    • Sinusitis (inflamed sinuses from infection)
    • Otitis media (inflamed middle ear)
    • Otitis externa (inflamed outer ear)
    • Pharyngitis (sore throat)
    • Epiglottitis (inflamed epiglottis, can be life-threatening, but controlled by vaccine)

    Pneumonia

    • A severe complication of bronchitis.
    • Bronchioles and alveoli fill with pus (dead microbes, inflammatory cells, fluid exudate)—leading to a “shadow” or opaque area visible on X-ray.
    • Most common causes are various bacteria; some fungi are especially life-threatening.

    Common & Less Common Causes of Bacterial Pneumonia by Age Group

    • Young adults: Streptococcus pneumoniae and Mycoplasma pneumoniae (common)
    • Adults: Streptococcus pneumoniae and Legionella (common)
    • Older adults: Streptococcus pneumoniae, Haemophilus influenzae, and Legionella (common); Tuberculosis and Mycoplasma (less common)

    Streptococcus pneumoniae

    • Gram-positive cocci in pairs or chains, have a unique lancet shape
    • Catalase-negative (all streptococcus bacteria are)
    • Capsule: Important virulence factor. 84 known serotypes (basis for pneumococcal vaccine). 
    • Also produces an IgA protease and a pneumolysin.
    • Grows readily on blood agar, causing alpha-hemolysis.

    Pneumococcal Pneumonia

    • Caused by Streptococcus pneumoniae in its lobar form.
    • Common in young to middle-aged adults, somewhat rare in infants and the elderly, but lethal in people with other conditions (e.g., cancer, alcoholism).
    • Symptoms include sudden onset with fever, chest pain, and thick sputum.

    Pneumococcal Pneumonia (Diagnosis)

    • Diagnosis involves Gram stain and culture of sputum samples to detect alpha-hemolysis and optochin disk sensitivity.
    • Additional tests are bile solubility test and urine antigen test.

    Pneumococcal Pneumonia (Pathogenesis)

    • Aerosolized or colonized bacteria are aspirated into the alveoli.
    • Inflammation ensues, filling the alveoli with edema fluid, leading to capillary congestion, massive infiltration of PMNs, and hemorrhage (red hepatization), followed by phagocytosis—leading to grey hepatization.
    • Bacteremia may occur, potentially resulting in life-threatening complications depending on the patient's condition.

    Other Pneumococcal Diseases

    • Common causes of meningitis, otitis media, and sinusitis involving Streptococcus pneumoniae.
    • Bacteremia can also lead to meningitis, endocarditis, and pneumonia (if not primary respiratory).

    Haemophilus influenzae

    • Gram-negative coccobacillus (or short rod).
    • Fastidious grower (needs chocolate agar for culturing).
    • IgA protease-producing bacteria that may facilitate colonization.
    • Outer capsule is a key virulence factor.

    Haemophilus influenzae (Continued)

    • Six capsular serotypes exist. Serotype b is the most common cause of infection and the basis for Hib vaccine
    • Other infections related to H. influenzae include pneumonia, meningitis, epiglottitis, otitis media, sinusitis, conjunctivitis, bacteremia, and cellulitis/arthritis

    Mycoplasma pneumoniae

    • The cause of "walking pneumonia" or "viral pneumonia."
    • Occurs mostly in older children and young adults.
    • Has a relatively long incubation period (10–14 days).
    • Unique characteristics: smallest free-living bacteria, lack a cell wall, cannot be gram-stained, difficult to grow on agar or in culture media.

    Mycoplasma pneumoniae (Continued)

    • Pneumonia often mild or asymptomatic to mild.
    • Treatment is typically readily treatable—with non-beta-lactam antibiotics.
    • Complications can include otitis media, erythema multiforme, hemolytic anemia, myocarditis, pericarditis, and neurological complications—like tracheobronchitis and pharyngitis.
    • Diagnosis is done through serological testing (ELISA, cold hemagglutinins)—or molecular techniques (PCR) for detection (e.g., of the presence of cold hemagglutinins).

    Bordetella pertussis

    • The causative agent of whooping cough.
    • A gram-negative, fragile coccobacillus.
    • Requires special media (Bordet-Gengou) for culturing.
    • Rare due to the DTP vaccine (though possible waning immunity and emerging genetic variants can occasionally cause outbreaks).
    • Disease has catarrhal, paroxysmal, and convalescent stages; complications can arise in each.

    Klebsiella pneumoniae

    • A gram-negative, non-motile bacillus, member of the enteric family.
    • Grows on various agars (blood, MacConkey).
    • Lactose fermenter
    • Possesses endotoxin (LPS) and a capsule, which hinders antibiotic treatment and is often life-threatening.
    • Common in pneumonia cases in people with chronic conditions (e.g., alcohol use disorder, diabetes, cancer).

    Pseudomonas aeruginosa

    • Gram-negative rod, found almost everywhere in moist environments.
    • Oxidase positive but lactose negative
    • Colonies are colorless on MacConkey agar but produce a bluish-green pigment (pyocyanin).
    • A significant pathogen for cystic fibrosis patients.

    Clinical Case Summary

    • A 59-year-old man with emphysema presents with symptoms such as fever, chills, chest pain, and a cough, with rust-colored sputum.
    • He has acute respiratory distress in the lower lobes of his left lung—which includes crackles, rhonchi, and expiratory wheezing.
    • Diagnosing his possible infection relies on lab tests and X-ray findings.

    Clinical Case Questions

    • What is the most likely cause of the patient's illness?
    • What would one expect to see in a sputum Gram stain?
    • What pathogen is most likely based on the patient's condition?
    • What are the unique characteristics of this organism?

    Summary

    • Microbes can cause various respiratory diseases
    • Pneumonia, a severe respiratory illness, is primarily caused by bacteria (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella pneumophila).
    • Tuberculosis caused by Mycobacterium tuberculosis is a chronic respiratory infection.
    • Key virulence factors include outer capsule, LPS, IgA protease, and mycolic acids (specific to certain bacteria or pathogens).

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    Description

    This quiz focuses on the differentiation and description of respiratory pathogens, emphasizing their roles in infections. It investigates bacterial pathogens, particularly those causing pneumonia, and explores tests for clinical diagnosis. Dive into the microbiologic features and epidemiology of significant bacteria in respiratory illnesses.

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