Non-Fermenting Bacilli Overview
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Which organism is the most commonly isolated non-fermenting bacilli in clinical specimens?

  • Pseudomonas aeruginosa (correct)
  • Escherichia coli
  • Stenotrophomonas maltophilia
  • Acinetobacter baumanii

    • What characteristic is true for all non-fermenting bacilli?

  • They are all Gram-positive.
  • They ferment glucose.
  • They grow on MacConkey agar. (correct)
  • They are all anaerobic.

    • Which of the following features is commonly associated with Pseudomonas aeruginosa?

  • It does not have flagella.
  • It is oxidase positive. (correct)
  • It is anaerobic.
  • It ferments lactose.

    • How is Pseudomonas aeruginosa mainly acquired in the environment?

    <p>It is found in aqueous environments.</p> Signup and view all the answers

    What is a common characteristic of Acinetobacter baumanii?

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

    What is the primary function of the repeating polymer of mannuronic and glucuronic acid in Pseudomonas aeruginosa?

    <p>To form the matrix of the biofilm</p> Signup and view all the answers

    Which characteristic is true about the motility of Pseudomonas aeruginosa?

    <p>It has a single polar flagellum.</p> Signup and view all the answers

    Which of the following antibiotics is Pseudomonas aeruginosa typically resistant to?

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

    What is an indicator of multi-drug resistant Pseudomonas aeruginosa (MDRP)?

    <p>Resistance to carbapenems</p> Signup and view all the answers

    In which of the following conditions is Pseudomonas aeruginosa most frequently isolated?

    <p>Lung tissue of cystic fibrosis patients</p> Signup and view all the answers

    What type of test results indicate that Pseudomonas aeruginosa does not ferment carbohydrates?

    <p>Oxidizer of Carbohydrates</p> Signup and view all the answers

    Which treatment approach is essential for managing severe infections caused by Pseudomonas aeruginosa?

    <p>Combination therapy with suitable agents</p> Signup and view all the answers

    Pseudomonas aeruginosa is particularly noted for its ability to:

    <p>Develop resistance during antibiotic treatment.</p> Signup and view all the answers

    Which populations are at high risk for infections caused by Pseudomonas aeruginosa?

    <p>Patients with severe immunodeficiencies</p> Signup and view all the answers

    What is the leading cause of nosocomial respiratory tract infections?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    Which virulence factor of Pseudomonas aeruginosa is associated with adhesion?

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

    Which of the following infections is NOT commonly associated with Pseudomonas aeruginosa?

    <p>HIV/AIDS</p> Signup and view all the answers

    What type of bacteria is Pseudomonas aeruginosa based on its cellular morphology?

    <p>Slender Gram Negative Bacilli</p> Signup and view all the answers

    What is a characteristic trait of Pseudomonas aeruginosa colonies on Blood Agar Plate (BAP)?

    <p>Colonies displaying a metallic sheen</p> Signup and view all the answers

    What is a common pigment produced by Pseudomonas aeruginosa?

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

    Which characteristic is associated with the mucoid strain of Pseudomonas aeruginosa?

    <p>Alginate production</p> Signup and view all the answers

    Which infections are commonly associated with Acinetobacter baumannii in immunocompromised patients?

    <p>Septicemia and eye infections</p> Signup and view all the answers

    What is a key characteristic of Acinetobacter baumannii's cellular morphology?

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

    Which of the following growth characteristics is true for Acinetobacter baumannii on MAC?

    <p>It exhibits non-lactose fermentation</p> Signup and view all the answers

    What is Acinetobacter baumannii's resistance to many antimicrobials attributed to?

    <p>The presence of carbapenemases</p> Signup and view all the answers

    What can cause false staining with Acinetobacter baumannii?

    <p>Crystal violet retention</p> Signup and view all the answers

    What is the typical catalase test result for Acinetobacter baumannii?

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

    Which of the following is true regarding the mortality rate associated with infections caused by Acinetobacter baumannii?

    <p>It has a mortality rate of 22% for ventilator-associated pneumonia and sepsis</p> Signup and view all the answers

    What is the lysine decarboxylase test result for Acinetobacter baumannii?

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

    What type of infections is Stenotrophomonas maltophilia primarily associated with in hospitalized patients?

    <p>Wound infections and bacteremia</p> Signup and view all the answers

    Which of the following treatments is inherently ineffective against Stenotrophomonas maltophilia?

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

    Which characteristic is true regarding the colonial morphology of Stenotrophomonas maltophilia on BAP?

    <p>Large, smooth glistening colonies with lavender-green pigment</p> Signup and view all the answers

    What is the cellular morphology of Stenotrophomonas maltophilia?

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

    Which test result would be expected for Stenotrophomonas maltophilia?

    <p>Gelatinase positive</p> Signup and view all the answers

    Why is susceptibility testing a must when treating Stenotrophomonas maltophilia?

    <p>It frequently shows variable resistance patterns</p> Signup and view all the answers

    What odor is commonly associated with Stenotrophomonas maltophilia colonies?

    <p>Strong ammonia smell</p> Signup and view all the answers

    Which test result would be negative for Stenotrophomonas maltophilia?

    <p>Oxidase test</p> Signup and view all the answers

    Study Notes

    Non-Fermenting Bacilli (NFB)

    • Common NFBs include Pseudomonas aeruginosa, Acinetobacter baumanii, and Stenotrophomonas maltophilia.
    • All are Gram-negative bacilli and grow on MacConkey agar.
    • All are oxidase and catalase positive.
    • All are resistant to a wide range of antimicrobials.

    Pseudomonas aeruginosa

    • Most common NFB.
    • Ubiquitous in the environment, including water, soil, and plants.
    • Opportunistic pathogen, often infecting immunocompromised patients, burn victims, and those with medical devices.
    • Commonly causes nosocomial (hospital-acquired) infections.
    • Can cause a variety of infections, including pneumonia, wound infections, bacteremia, and UTI's.
    • Produces pigments including pyocyanin, pyorubin, pyomelanin, and pyoverdin.
    • Mucoid strains, often associated with cystic fibrosis, produce alginate, which forms a biofilm.
    • Susceptibility testing is crucial due to the organism's inherent resistance to many antibiotics.

    Acinetobacter baumanii

    • Second most common NFB.
    • Ubiquitous in the environment and hospitals.
    • Opportunistic pathogen, often infecting immunocompromised patients.
    • Can cause a variety of infections, including pneumonia, bacteremia, meningitis, and UTI's.
    • Highly resistant to antibiotics, including carbapenems, with multi-drug resistant strains (MDRA) emerging.
    • Often appears coccobacillary.
    • Produces a purplish tinge on MacConkey agar.
    • Growth on blood agar is smooth, opaque, raised, and creamy.

    Stenotrophomonas maltophilia

    • Third most common NFB.
    • Not normal flora but a colonizer in hospitalized patients.
    • Opportunistic pathogen, often infecting immunocompromised patients.
    • Can cause a variety of infections, including endocarditis, wound infections, bacteremia, and meningitis.
    • Inherently resistant to many antibiotics, including cephalosporins, penicillins, carbapenems, and aminoglycosides.
    • Trimethoprim-sulfamethoxazole (SXT) is often the drug of choice for treatment.
    • Colonies produce a strong ammonia smell.
    • On MacConkey agar, colonies appear non-lactose fermenting with a bluish tinge.
    • On blood agar, colonies are large, smooth, glistening, with uneven edges and lavender-green to light purple pigment.

    Pseudomonas aeruginosa – Key Virulence Factors

    • Lipopolysaccharide: Antiphagocytic activity, cytotoxicity.
    • Pili: Adhesion.
    • Flagella: Motility, adhesion.
    • Type III secretion system: Cytotoxic activity.
    • Phospholipases: Cytotoxicity.
    • Proteases: Cytotoxicity, proteolytic activity.
    • Exotoxin A: Cytotoxicity.
    • Capsule: Antiphagocytic activity.
    • Deoxyribonuclease (DNase): Breaks down DNA.
    • Elastase: Cytotoxicity, proteolytic activity.
    • Lecithinase: Cytotoxicity, proteolytic activity
    • Hemolysins: Cytotoxicity.

    Pseudomonas aeruginosa – Identification

    • Motile with polar flagellum.
    • Oxidase positive.
    • Catalase positive.
    • Nitrate positive, usually beyond nitrite to nitrogen gas..
    • Arginine Dihydrolase (ADH) positive.
    • Citrate positive.
    • Oxidizer of carbohydrates on OF test, non-fermenter.
    • TSI Alk/Alk, or K/K.
    • Growth at 42°C positive.

    Acinetobacter baumanii – Identification

    • Oxidase negative.
    • Catalase positive.
    • Nonmotile.
    • TSI K/NC or NC/NC.
    • Glucose OF: +/-
    • Lysine Decarboxylase negative.

    Stenotrophomonas maltophilia – Identification

    • Oxidase negative.
    • Catalase positive.
    • Motility positive.
    • Dnase positive.
    • Esculin positive.
    • Gelatinase positive.
    • Lysine Decarboxylase positive.

    Comparison of NFB

    Organism Cellular Morphology Colonial Morphology (MAC) Colonial Morphology (BAP) Oxidase Motility TSI OF
    P. aeruginosa Slender GNB NLF (May have pigment) Metallic sheen, fruity odor Positive Positive K/K Oxidizer
    A. baumanii Small GNB (can be coccid) NLF (May have purplish tinge) NH, small, wet Negative Negative K/K Oxidizer
    S. maltophilia GNB NLF (May have bluish tinge) NH, small, wet, ammonia odor Negative Positive K/K Oxidizer

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    Lecture 12 – Non-fermenting Bacilli (NFB) PDF

    Description

    This quiz covers the characteristics, infections, and significance of non-fermenting bacilli (NFB), focusing on key species such as Pseudomonas aeruginosa, Acinetobacter baumanii, and Stenotrophomonas maltophilia. Assess your understanding of their biology, pathogenicity, and antibiotic resistance profiles.

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