Staphylococcus aureus Quiz
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Questions and Answers

What is a common infection caused by Staphylococcus aureus in surgical wounds?

  • Bacteremia
  • Furuncles (correct)
  • Pneumonia
  • Skin ulcers

Staphylococcus aureus can only be found in hospitals.

False (B)

What are the characteristic colors and sizes of Staphylococcus aureus colonies on blood agar?

Medium to large colonies, cream to golden color

Staphylococcus aureus can cause ______ which is characterized by a toxic shock.

<p>staphylococcal toxic shock</p> Signup and view all the answers

Match the following infections with their corresponding characteristics:

<p>Furuncles = Skin/hair follicle infections Pneumonia = Respiratory infection Bacteremia = Presence of bacteria in the bloodstream Scalded skin syndrome = Toxin-producing skin condition</p> Signup and view all the answers

Which of the following is NOT a notable characteristic of Staphylococcus aureus on blood agar?

<p>Small colonies (B)</p> Signup and view all the answers

Staphylococcus aureus infections can lead to sepsis.

<p>True (A)</p> Signup and view all the answers

What percentage of people are likely to carry Staphylococcus aureus in their nose or on their skin?

<p>10 - 40%</p> Signup and view all the answers

Which of the following is associated with catalase-negative bacteria?

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

All strains of Staphylococcus are catalase-positive.

<p>False (B)</p> Signup and view all the answers

What is the primary identifying feature of Enterococcus species?

<p>They are catalase-negative and often found in chains.</p> Signup and view all the answers

The ______ are known for their role in causing pneumonia.

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

Which group is associated with enterococcus species?

<p>Gamma-hemolytic (C)</p> Signup and view all the answers

Match the following bacteria with their characteristics:

<p>Streptococcus pyogenes = Beta-hemolytic Staphylococcus aureus = Catalase positive Streptococcus viridans = Alpha-hemolytic Enterococcus = Gamma-hemolytic</p> Signup and view all the answers

Staphylococcus saprophyticus is commonly found in urine infections.

<p>True (A)</p> Signup and view all the answers

What characterizes the group D streptococci?

<p>They are often associated with enterococcus species.</p> Signup and view all the answers

What type of stain is used to differentiate between Gram-positive and Gram-negative bacteria?

<p>Gram stain (C)</p> Signup and view all the answers

Gram-positive bacteria will appear pink after the Gram staining process.

<p>False (B)</p> Signup and view all the answers

What is the purpose of a wet mount in microscopic examination?

<p>To observe motility.</p> Signup and view all the answers

The ___ stain is used to detect Mycobacterium species.

<p>Acid fast</p> Signup and view all the answers

Match the following types of bacteria with their characteristics:

<p>Cocci = Spherical shape Bacillus = Rod shape Coccobacillus = Short, rounded rod Pleomorphic = Variable shape</p> Signup and view all the answers

What is the role of the iodine in the Gram staining process?

<p>Crystal violet fixative (A)</p> Signup and view all the answers

Colony morphology is usually definitive for bacterial identification.

<p>False (B)</p> Signup and view all the answers

What are the two main groups of bacteria determined by Gram staining?

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

What is the dilution ratio used in the serial dilutions starting from the tube labeled '8 μg/ml'?

<p>2-fold (D)</p> Signup and view all the answers

The Minimum Bactericidal Concentration (MBC) is defined as the lowest concentration of antimicrobial that inhibits 99.9% of bacteria.

<p>False (B)</p> Signup and view all the answers

What is the optimal inoculum concentration needed for testing bacterial susceptibility?

<p>10^5 to 10^6 cells/ml</p> Signup and view all the answers

The breakpoint is the cutoff MIC that determines if bacteria are ____, ____, or ____.

<p>susceptible, intermediate, resistant</p> Signup and view all the answers

Match the following terms with their definitions:

<p>S = Susceptible I = Intermediate R = Resistant MIC = Minimum Inhibitory Concentration</p> Signup and view all the answers

Which of the following concentrations represents the highest dilution in the prepared series?

<p>0.06 μg/ml (B)</p> Signup and view all the answers

Adding 1 ml of bacterial suspension to each tube prepared is necessary for determining the Minimum Inhibitory Concentration (MIC).

<p>True (A)</p> Signup and view all the answers

What concentration is defined as 5 x 10^9 cells/ml in the dilution process?

<p>5 x 10^7 cells/ml and then 5 x 10^5 cells/ml</p> Signup and view all the answers

Which of the following statements accurately describes Listeria monocytogenes?

<p>Hippurate positive and bile-esculin positive (A)</p> Signup and view all the answers

Haemophilus influenzae is a motile organism.

<p>False (B)</p> Signup and view all the answers

What are the two main types of Listeria monocytogenes strains based on encapsulation?

<p>Typeable strains and non-typeable strains</p> Signup and view all the answers

Listeria monocytogenes exhibits _____ motility.

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

Match the following Haemophilus species with their characteristics:

<p>H. influenzae = Causes respiratory infections in children H. parainfluenzae = Normal resident of the upper respiratory tract Haemophilus = Blood-loving organism H. ducreyi = Causes chancroid</p> Signup and view all the answers

Which of the following is a major virulence factor for strains of H. influenzae causing invasive disease?

<p>Polysaccharide capsule (D)</p> Signup and view all the answers

Bacitracin is a reliable test to distinguish Listeria from Streptococcus.

<p>True (A)</p> Signup and view all the answers

What is the primary mode of transmission for H. influenzae infections?

<p>Inhalation of aerosolized respiratory droplets</p> Signup and view all the answers

Which bacterium is associated with causing diphtheria?

<p>Corynebacterium diphtheriae (C)</p> Signup and view all the answers

Moraxella catarrhalis can grow on Nutrient agar.

<p>True (A)</p> Signup and view all the answers

What is the primary virulence factor of Corynebacterium diphtheriae?

<p>AB exotoxin</p> Signup and view all the answers

Neisseria lactamica can grow on CA and BA but not on _____ agar.

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

Match the following bacterial species with their characteristics:

<p>Neisseria lactamica = Tends to be non-pathogenic, can ferment glucose and lactose Corynebacterium diphtheriae = Causes diphtheria, produces exotoxin Moraxella catarrhalis = Grows on various agars, distinct 'hockey puck' appearance Listeria = Facultative anaerobic, can cause foodborne illness</p> Signup and view all the answers

Which statement is true regarding the characteristics of Corynebacterium species?

<p>They form club-shaped structures and can show palisade arrangements. (A)</p> Signup and view all the answers

Neisseria lactamica and Corynebacterium diphtheriae are both motile bacteria.

<p>False (B)</p> Signup and view all the answers

What kind of oxygen requirement do Corynebacterium and Listeria species have?

<p>Facultative anaerobes</p> Signup and view all the answers

Corynebacterium diphtheriae can result in the formation of a _____ in the throat.

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

Which of the following may be used to differentiate between Corynebacterium species?

<p>Sugar fermentation patterns (C)</p> Signup and view all the answers

Flashcards

Gram Stain

A differential stain used to distinguish between Gram-positive and Gram-negative bacteria based on their cell wall structure.

Gram-positive bacteria

Bacteria with a thick peptidoglycan layer in their cell wall that retain the crystal violet stain.

Gram-negative bacteria

Bacteria with a thin peptidoglycan layer surrounded by an outer membrane in their cell wall. They appear pink/red after staining.

Bacterial Morphology

The shape and arrangement of bacterial cells.

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Microscopic Examination

Looking at bacteria under a microscope to view shape, size, grouping, and other features.

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Wet Mount

A simple microscopic technique to observe bacteria's motility.

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Bacterial Culture

Growing bacteria in a controlled environment to study or identify them better.

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Colony Morphology

The appearance of bacterial colonies on a growth medium; a clue, but not definitive for identification.

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Staphylococcus aureus - Skin Infections

S. aureus can cause skin and hair follicle infections, including boils (furuncles) and carbuncles.

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Staphylococcus aureus - Wound Infections

S. aureus is a major cause of wound infections, especially surgical wounds, which are a type of nosocomial infection (acquired in a healthcare setting).

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Staphylococcus aureus - Pneumonia

S. aureus can cause pneumonia, which is an inflammation of the lungs.

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Staphylococcus aureus - Bacteremia and Sepsis

S. aureus can infect the bloodstream, leading to bacteremia. If this infection spreads widely and triggers an overwhelming immune response, it's called sepsis.

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Staphylococcus aureus - Food Poisoning

Some strains of S. aureus produce toxins that can cause food poisoning.

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Staphylococcus aureus - Toxic Shock Syndrome

Certain strains of S. aureus can produce toxins that cause toxic shock syndrome, a serious condition with widespread organ dysfunction.

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Staphylococcus aureus - Scalded Skin Syndrome

Some S. aureus strains produce toxins that cause scalded skin syndrome, a blistering skin condition, mostly in infants.

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Staphylococcus aureus - Colony Morphology on Blood Agar

On blood agar, S. aureus colonies are medium to large, cream to golden in color, and usually show beta-hemolysis (clear zone around the colony).

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MIC

Minimum Inhibitory Concentration. The lowest concentration of an antimicrobial drug that inhibits the visible growth of a bacterium.

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Serial Dilution

A technique used in microbiology to create a series of solutions with decreasing concentrations of a substance, usually a drug. Each step is a dilution of the previous one, often by half (2-fold dilution).

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What is the purpose of a 2-fold serial dilution?

It's used to test a wide range of antimicrobial concentrations and determine the MIC. The serial dilution helps us identify the minimum concentration needed to stop the growth of a specific bacteria.

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Breakpoint

A specific MIC value (concentration of antimicrobial drug) that defines whether a bacterial strain is considered susceptible, intermediate, or resistant to that drug.

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Susceptible

A bacterial strain is considered susceptible to an antimicrobial drug when its growth is inhibited by concentrations that can be achieved in the body.

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Resistant

A bacterial strain is resistant to an antimicrobial drug when its growth is not inhibited by concentrations achievable in the body.

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MBC

Minimum Bactericidal Concentration. The lowest concentration of an antimicrobial drug that kills 99.9% of a bacterial population.

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Bacteriostatic vs Bactericidal

Bacteriostatic agents inhibit bacterial growth (but don't kill them) while Bactericidal agents kill bacteria.

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Catalase Test

A test that determines if a bacteria produces the enzyme catalase, which breaks down hydrogen peroxide into water and oxygen. A positive result shows bubbles, indicating the presence of catalase.

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Enterococcus

A genus of Gram-positive bacteria commonly found in the intestines of animals (including humans) and the environment. Known for its ability to survive in harsh conditions.

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Streptococcus

A genus of Gram-positive bacteria that are often found in pairs or chains. Some species are harmless, while others can cause infections.

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Staphylococcus

A genus of Gram-positive bacteria that are often found in clusters. Some species can cause infections, including skin infections, food poisoning, and pneumonia.

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Group D Streptococci

A group of Streptococcus bacteria that are identified through biochemical testing. Some are normal flora, while others are opportunistic pathogens.

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Alpha Hemolysis

A type of hemolysis where bacteria partially break down red blood cells, resulting in a greenish halo around the colonies on blood agar.

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Beta Hemolysis

A type of hemolysis where bacteria completely lyse red blood cells, leading to a clear zone around bacterial colonies on blood agar.

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Gamma Hemolysis

No hemolysis, bacteria don't affect red blood cells, leaving no change in the blood agar.

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Listeria Culture

Listeria monocytogenes grows as small, translucent colonies with a narrow zone of hemolysis on blood agar. It's motile and exhibits 'tumbling' motility.

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Differentiating Listeria

Listeria is differentiated from Streptococcus and Enterococcus by being catalase positive and gram-positive. Its motility is also distinctive.

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Haemophilus Characteristics

Haemophilus species are Gram-negative, pleiomorphic rods. They are non-motile, facultative anaerobes and are catalase and oxidase positive.

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Haemophilus Habitat

Most Haemophilus species are normal residents of the upper respiratory tract in humans or animals.

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H. influenzae Clinical Significance

Haemophilus influenzae causes respiratory infections, bacteremia, and meningitis, primarily in infants and young children.

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H. influenzae Virulence Factor

The major virulence factor of H. influenzae strains causing invasive disease is the polysaccharide capsule.

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Typeable vs Non-Typeable Strains

Encapsulated strains are called 'typeable' (a-f), while unencapsulated strains are 'non-typeable'.

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H. parainfluenzae

H. parainfluenzae is a normal part of the human upper respiratory tract microbiota and usually only causes infection occasionally.

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Neisseria gonorrhoeae Growth

Neisseria gonorrhoeae is a fastidious bacterium that can grow on chocolate agar (CA) and blood agar (BA) but not on nutrient agar (NA).

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Neisseria lactamica Growth

Neisseria lactamica can grow on chocolate agar (CA) and blood agar (BA) but not nutrient agar (NA).

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Moraxella catarrhalis Growth

Moraxella catarrhalis can grow on chocolate agar (CA), blood agar (BA), and nutrient agar (NA).

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Corynebacterium

Corynebacterium are a genus of non-sporeforming, Gram-positive rods with unique morphology. They are often pleiomorphic (varied in shape) with club-shaped ends, forming V-formations and palisades.

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Corynebacterium Characteristics

Corynebacterium are facultative anaerobes, catalase-positive, and are distinguished by features such as sugar fermentation patterns, motility, nitrate reduction, and urease activity.

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Corynebacterium diphtheriae

Corynebacterium diphtheriae is a pathogenic bacterium that causes diphtheria, a serious respiratory infection.

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Diphtheria Toxin

Corynebacterium diphtheriae produces a potent AB exotoxin that inhibits protein synthesis in host cells, leading to cell death and the formation of a pseudomembrane in the upper respiratory tract.

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Pseudomembrane

A thick, grayish-white membrane that forms in the throat during diphtheria due to cell death caused by the toxin.

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Corynebacterium diphtheriae: System Effects

The toxin from C. diphtheriae can spread through the bloodstream, causing damage to other organs, particularly the heart and nerves.

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Corynebacterium pseudodiphtheriticum

Corynebacterium pseudodiphtheriticum is a non-pathogenic species that resembles C. diphtheriae but doesn't cause diphtheria.

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Study Notes

Course Information

  • Course name: Microm 443
  • Instructors: Kendall M. Gray, Ph.D., Rebecca Rashid Achterman, Ph.D., and Mira Beins, Ph.D.
  • Department: Microbiology
  • Course components: Lectures and Lab
  • Schedule available in lab manual; required
  • Course website: schedule, lecture outlines, announcements, grading system, videos (required), and optional resources.
  • Required textbook: Sherris' Medical Microbiology (online, Canvas link)
  • Additional resources: Photographic Atlas for the Microbiology Lab, and Gram Stain Tutor (Canvas)

Course Purpose

  • Learn to identify causative agents of bacterial infections
  • Understand treatment approaches and surveillance methods for bacteria
  • Understand importance of microbial identification

Lab Information

  • Lab sessions are held.
  • If no lecture, lab is still mandatory.
  • Lab safety procedures are essential and outlined in lab manual

General Course Information

  • Course meets at 11:30 am.
  • Lab work occurs on specific days
  • Lab schedule includes specific procedures for different weeks and specific pages in manual
  • Quizzes occur every week, with best 6/7 used for grade (20-25% of final grade)
  • Quizzes are cumulative
  • Unknowns (7 + differentiation scheme, 2-3 pts each; ~10-15% of final grade)
  • Lots of help for early unknowns.
  • Midterm (~20-25% of final grade)
  • Final (~40-50% of final grade).

Safety

  • Working with pathogens (BSL-2)
  • Standard lab safety procedures required and included in the lab manual
  • Proper aseptic techniques are essential.
  • Infectious dose (ID50) of Shigella species: 10-100 cells
  • Avoid aerosols
  • Safety quiz due week 2 (Monday) on-line with questions on last page of the lab manual.
  • Alcohol swabs.

Microbiology Information Overview

  • Identifying Bacteria, What is a clinical specimen?, and Basic Microscopy
  • Microscopic exam of clinical specimens involves identifying host cells (WBC, epithelial) and bacterial cells (size, shape, grouping).
  • Identification follows with culture methods..
  • Culture → identification: cultivating bacteria, microscopic exam of pure culture, and identification.
  • Colony morphology for a clue.
  • Microscopic examinations: wet mount - simple, for motility, dark field - enhances light field, and Gram stain - differential stain
  • Gram-positive cells stain purple.
  • Gram-negative cells become colorless.
  • Cyto. membrane, Peptidoglycan, Over-decolonized, Outer Membrane..
  • Gram- positive cocci (GPC), Gram-negative cocci (GNDC). shape diagrams are provided
  • Gram-positive and gram-negative rods
  • Types of rods include pleomophic, curved rods, and coccobacilli.

Microbial Techniques

  • Dark field (earlier described)
  • Methylene blue staining for observation of metachromatic granules
  • Capsule staining using negative staining
  • Acid fast staining detects Mycobacterium spp. (pathogens like M. tuberculosis)
  • Fluorescence tagging: antibody and/or nucleic acid probes

Media Identification

  • Routine media (TSY, Nutrient agar, and Mueller-Hinton): support many bacterial types
  • Blood agar: 5% sheep blood for increased growth.
  • Chocolate agar: lysed blood cells to support growth
  • MacConkey (selective): inhibits all except intestinal GNR
  • Differential media: ex. blood agar
  • hemolysis
  • MacConkey: lactose fermentation
  • Other Media for specific organisms

Bacterial Identification

  • Genus and species identification from phenotypic (observable) characteristics
  • Examples: Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus saprophyticus, MRSA ,E. coli.
  • Various characteristic of each listed above, including testing methods.

Antimicrobial drugs

  • Determining the susceptibility of an organism to different drugs
  • Minimum inhibitory concentration (MIC) method: broth dilution
  • Kirby-Bauer disk diffusion

Additional Notes

  • Student evaluations support the excellent structure of the course, emphasizing the repeated use of the skills learned in the first half of the quarter.
  • Various aspects of procedures, specimens, and testing methods

Additional Microbial Procedures

  • Cultivating bacteria, including proper technique -Different environments for incubation -Incubation time (35°C, increased CO2) and materials, such as candle jars, and anaerobic pouches or boxes for specific oxygen requirements. -various media options such as blood agar and MacConkey media.
  • Methods of culturing bacteria such as the streak plate technique
  • Various testing methods - Gram strains, methods on plates for various organisms.

Additional Bacterial Specifics and Identification

  • Different bacterial species and identification methods
  • examples included: Corynebacterium diphtheriae, Listeria monocytogenes, Haemophilus influenzae, Neisseria gonorrhoeae, Neisseria meningitidis, and various others
  • Specific tests and characteristics for each bacterium are given

Other Notes

  • Various aspects of procedures, specimens, and testing methods are presented in the provided notes to aid students with study and lab endeavors

Lab Information to include

  • Using pipettes (1ml and 5ml varieties)
  • Using lab racks, as needed.

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Micro 443 Combined PDF

Description

Test your knowledge on Staphylococcus aureus and its role in infections. This quiz covers various aspects such as characteristics, infections, and identification of this bacterium. Ideal for students studying microbiology or healthcare professionals.

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