Staphylococcus and Micrococcus Quiz
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Questions and Answers

What characteristics distinguish rare strains of aureus that require specific growth conditions?

They are fastidious, requiring CO2, hemin, or menadione for growth and form small colonies with 1/10 the size of wild type strains after 48 hours.

Describe the microscopic appearance of aureus in terms of cell arrangement.

Aureus appears as spherical cells that can be found singly, in pairs, or in clusters.

What are the cultural characteristics of aureus colonies on BAP agar plates?

Aureus colonies appear creamy, white, or light gold, typically measuring 4mm-8mm, with a buttery texture.

How does aureus react to lysostaphin compared to other staphylococci species?

<p>Aureus is not lysed by lysostaphin, while S. saprophyticus is sensitive and lysed by it.</p> Signup and view all the answers

Explain the significance of aureus being B-hemolytic and its implications on antibiotic resistance.

<p>B-hemolytic aureus strains can exhibit antibiotic resistance, complicating treatment and requiring susceptibility testing.</p> Signup and view all the answers

What are the newly suggested strains of Staphylococci mentioned in the content?

<p>Staph lutrae and Staph agnetis.</p> Signup and view all the answers

Describe the morphological characteristics of Staphylococcus aureus.

<p>It is Gram-positive, spherical, and mostly arranged in irregular grape-like clusters.</p> Signup and view all the answers

What role does the peptidoglycan layer play in Staphylococcus cell structure?

<p>It is the major structural component of the cell wall and is important for pathogenesis.</p> Signup and view all the answers

What type of hemolysis is observed with Staphylococcus schleiferi on sheep blood agar?

<p>Marked hemolysis.</p> Signup and view all the answers

Which selective media can be used to identify lactose fermentation in Staphylococcus species?

<p>Mac Conkey agar.</p> Signup and view all the answers

What metabolic conditions are preferred for the growth of some Staphylococcus strains?

<p>20-25% CO2 concentration.</p> Signup and view all the answers

What is the major protein component of the Staphylococcus cell wall?

<p>Protein A.</p> Signup and view all the answers

What type of colonies appear on Mac Conkey agar when lactose is fermented?

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

What is the optimum temperature range for extensive exfoliative dermatitis?

<p>The optimum temperature is 37°C.</p> Signup and view all the answers

Which demographic is primarily affected by extensive exfoliative dermatitis?

<p>It occurs primarily in newborns and previously healthy children.</p> Signup and view all the answers

Describe the appearance of colonies observed on nutrient agar for the relevant condition.

<p>The colonies are large, circular, smooth, shiny, opaque, and easily emulsifiable.</p> Signup and view all the answers

What is the significance of the pH range 7.4-7.6 in relation to exfoliative dermatitis?

<p>This pH range is optimal for the growth of the bacteria responsible for the condition.</p> Signup and view all the answers

What is toxic shock syndrome (TSS) associated with, particularly among women?

<p>TSS is associated with women who use tampons.</p> Signup and view all the answers

What is the role of the epidermolytic toxin in the condition discussed?

<p>The epidermolytic toxin contributes to the symptoms of extensive exfoliative dermatitis.</p> Signup and view all the answers

What characteristic appearance is noted on nutrient slope media?

<p>The nutrient slope has an oil paint appearance.</p> Signup and view all the answers

What pigment is produced by the bacteria in this context, and what is its characteristic?

<p>The bacteria produce a yellow pigment that does not diffuse into the medium.</p> Signup and view all the answers

What is the purpose of the slide method in detecting coagulase positive colonies?

<p>The slide method screens for catalase positive colonies and detects cell-bound coagulase.</p> Signup and view all the answers

Describe the role of hemolysin as a cytotoxin.

<p>Hemolysin causes anemia by destroying red blood cells and making iron available for microbial growth.</p> Signup and view all the answers

What are the types of hemolysins and their primary actions?

<p>The four types are alpha-hemolysin (destroys RBCs), beta-hemolysin (destroys sphingomyelin), and gamma-hemolysin (less toxic).</p> Signup and view all the answers

How does beta-hemolysin exhibit enhanced hemolytic activity?

<p>Beta-hemolysin shows enhanced activity on incubation at 35°C, destroying RBCs around nerves.</p> Signup and view all the answers

What is the procedure for the tube coagulase test, and what does a positive result indicate?

<p>Inoculate a tube with plasma and incubate it at 35°C; a positive result indicates clot or coagulum formation.</p> Signup and view all the answers

What should be done if no clot appears in the tube coagulase test after 4 hours?

<p>The tube should be left at room temperature for an additional 20 hours of incubation.</p> Signup and view all the answers

What is the significance of coagulase production in necrotizing skin infections?

<p>Coagulase production helps to suppress phagocytosis and increases bacterial virulence in infections.</p> Signup and view all the answers

Which organisms are noted as other slide coagulase positive species?

<p>Staphylococcus lugdunensis and Staphylococcus schleiferi are other slide coagulase positive organisms.</p> Signup and view all the answers

What is the significance of mannitol salt agar in identifying MRSA?

<p>Mannitol salt agar is used as a selective and differential medium to identify MRSA by facilitating the fermentation of mannitol, resulting in yellow-colored colonies.</p> Signup and view all the answers

What genetic element is responsible for MRSA's resistance to penicillinase-resistant penicillin?

<p>The mecA gene encodes for the altered penicillin binding protein PBP2a or PBP2’, which gives MRSA its resistance.</p> Signup and view all the answers

What is a significant risk factor for acquiring infections from Staphylococcus epidermidis?

<p>Prolonged hospital stays and close contact with infected individuals.</p> Signup and view all the answers

What gene is associated with methicillin resistance in Staphylococcus epidermidis?

<p>The mecA gene.</p> Signup and view all the answers

How does a positive Chromogenic test indicate the presence of MRSA?

<p>A positive Chromogenic test shows a color change in MRSA colonies on CHROM agar, distinguishing them from non-MRSA colonies.</p> Signup and view all the answers

What morphological feature distinguishes MRSA from species like S.saprophyticus on MSA?

<p>MRSA typically produces yellow colonies on mannitol salt agar, whereas some strains of S.saprophyticus may also ferment mannitol but do not show a color change.</p> Signup and view all the answers

Name two common infections caused by Staphylococcus epidermidis.

<p>Infective endocarditis and nosocomial bacteremia.</p> Signup and view all the answers

What is the primary mechanism through which Staphylococcus epidermidis adheres to medical devices?

<p>Secretion of poly-gamma-DL-glutamic acid.</p> Signup and view all the answers

What role does the Durham tube play in the identification of staphylococci?

<p>The Durham tube is used to detect gas production by microorganisms, which can indicate fermentation activity.</p> Signup and view all the answers

How does Staphylococcus saprophyticus differ from other coagulase-negative staphylococci regarding novobiocin resistance?

<p>Staphylococcus saprophyticus is novobiocin resistant.</p> Signup and view all the answers

Why do isolates of oxacillin-resistant S.aureus get classified as MRSA?

<p>They are classified as MRSA due to their resistance to oxacillin, indicating an altered cell wall structure.</p> Signup and view all the answers

How does the high percentage of resistance among coagulase-negative staphylococci affect treatment options?

<p>The resistance of up to 80% of coagulase-negative staphylococci to penicillinase-resistant penicillin limits effective treatment options.</p> Signup and view all the answers

What type of bacteria are coagulase-negative staphylococci (CoNS), and how are they typically identified?

<p>They are non-hemolytic bacteria identified by biochemical tests like MSA (-) and coagulase tests.</p> Signup and view all the answers

What is indicated by the jet black colonies formed on tellurite glycine agar?

<p>Jet black colonies on tellurite glycine agar indicate the growth of S.aureus due to its ability to reduce tellurite.</p> Signup and view all the answers

In what clinical scenarios might Staphylococcus epidermidis be particularly virulent?

<p>In cases mimicking Staphylococcus aureus infections or in patients with compromised immune systems.</p> Signup and view all the answers

What type of colonies does Staphylococcus epidermidis produce on Blood Agar Plates (BAP)?

<p>Small to medium-sized, non-hemolytic, white opaque colonies.</p> Signup and view all the answers

Flashcards

Staphylococcus aureus

A bacterium often causing infections, sometimes with rare strains requiring specific growth conditions.

Growth requirements

Some strains of Staphylococcus aureus need carbon dioxide, hemin, or menadione to grow.

Colony morphology

Staphylococcus aureus colonies on agar plates appear creamy, white, or light gold, and have a buttery-looking texture.

S. saprophyticus

A species of Staphylococcus that causes urinary tract infections (cystitis).

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Lysostaphin sensitivity

Staphylococcus aureus is not lysed by lysostaphin, unlike some other species.

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Furazolidone sensitivity

Staphylococcus aureus is resistant to furazolidone (a type of antibiotic).

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Small-colony variants

Rare strains of Staphylococcus aureus that are much smaller than wild-type strains.

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Staphylococci Phylum

Staphylococci belong to the Firmicutes phylum.

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Staphylococcus aureus

A type of staphylococcus that is commensal, meaning typically harmless, part of the normal flora.

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Staphylococcus Morphology

Gram-positive, spherical cells clustered in irregular, grape-like shapes.

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Staphylococcus Cell Wall

Peptidoglycan and teichoic acid are important structural components of their cell walls.

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Staphylococcus Protein A

A major protein component of the staphylococcus cell wall, important to its infections.

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Staphylococci Growth Medium

Various media can be used to cultivate staphylococci, including some selective medias.

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Blood Agar

A type of growth media that can be used to observe the hemolytic properties of Staphylococci and is sometimes used to grow Staphylococci.

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MacConkey Agar

MacConkey agar can be used for some types of Staphylococci.

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Selective Media

Media that encourages the growth of some types of bacteria while inhibiting others.

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Commensal Flora

Microorganisms that reside in or on the body without causing harm.

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Exfoliative Dermatitis in Newborns

A skin condition primarily affecting newborns and healthy children, characterized by extensive skin peeling.

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Optimum Temperature for Bacteria Growth

Bacteria grow best at 37°C (body temperature).

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Bacterial pH Range

Bacteria thrive in the pH range of 7.4-7.6 (slightly alkaline).

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Bacterial Types

Bacteria involved can be aerobes, facultative anaerobes.

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Colony Characteristics (Nutrient Agar)

Large, circular, smooth, shiny, opaque colonies; easily emulsified, yellow pigment not diffusing; carotene-like lipoprotein.

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Toxic Shock Syndrome (TSS)

Sudden, severe multi-system disease, associated with tampon use, causing fever, chills, vomiting.

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Best Pigment Production Temperature

Pigment production is optimal at 22°C; enhanced by glycerol monoacetate/milk.

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Nutrient Slope Appearance

Bacteria grown on a nutrient slope have an oil-paint appearance.

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Catalase Slide Method

A method used to screen for catalase activity in bacterial colonies, which helps differentiate organisms

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Coagulase (Slide Method)

A test to detect the presence of coagulase enzyme in bacterial colonies that causes clotting of plasma

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Coagulase (Tube Method)

A more sensitive method for detecting coagulase activity by looking for a clot formation in a tube with special plasma.

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Hemolysin

A cytotoxin that damages red blood cells (RBCs) and other cells which causes anemia, making iron available for microbial growth

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Alpha-Hemolysin

A type of hemolysin that destroys RBCs, platelets, and macrophages; causing severe tissue damage

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Beta-Hemolysin

A type of hemolysin that damages sphingomyelin and RBCs around nerves.

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Gamma-Hemolysin

A type of hemolysin that is less toxic than alpha and beta-hemolysins.

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Hospital-acquired infections

Infections acquired during a hospital stay.

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Nosocomial bacteremia

Bloodstream infection acquired in a hospital setting.

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Staphylococcus epidermidis

A common cause of prosthetic heart valve endocarditis and other hospital-acquired infections.

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Methicillin resistance

The ability of bacteria to resist the effects of methicillin, a type of antibiotic.

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Infective endocarditis

Infection of the inner lining of the heart chambers and valves.

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Sepsis

A life-threatening condition arising from the body's overwhelming response to infection.

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HA MRSA

Hospital-acquired methicillin-resistant Staphylococcus aureus.

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CA MRSA

Community-acquired methicillin-resistant Staphylococcus aureus.

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HACO MRSA

Health care-associated community-onset methicillin-resistant Staphylococcus aureus.

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Mannitol Salt Agar (MSA)

A selective and differential medium for Staphylococcus species, using mannitol and salt.

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MSA positive

S.aureus colonies turn yellow on MSA due to mannitol fermentation.

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MRSA identification by chromogenic test

Changes color within 24-48 hours using CHROM agar, showing contrast with non-MRSA for identification.

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methicillin resistance

Resistance to methicillin due to an altered penicillin-binding protein (PBP) called PBP2a.

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PBP2a

An altered penicillin-binding protein in MRSA, having low affinity for penicillin.

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mecA gene

Gene encoding the altered penicillin-binding protein PBP2a in MRSA.

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Oxacillin resistance

MRSA isolates are resistant to oxacillin, a penicillin.

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Tellurite glycine agar

Media producing jet black colonies of S.aureus.

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Study Notes

Staphylococcus

  • Derived from Greek words: "staphle" (bunches of grapes) and "kokkos" (berry)
  • Gram-positive cocci in grape-like clusters
  • Belong to the family Micrococcaceae
  • Normal inhabitants of skin, mucous membranes, and intestines
  • Common cause of suppurative infections
  • Catalase-producing, facultatively anaerobic (except S. saccharolyticus)

Differences between Staphylococcus and Micrococcus

  • Morphology: Staphylococci form clusters; Micrococci form tetrads or pairs
  • Clinical Significance: Staphylococci are more important clinically than Micrococci
  • Lysostaphin Sensitivity: Staphylococci are lysed by lysostaphin; Micrococci are resistant
  • Furazolidone Sensitivity: Staphylococci are susceptible; Micrococci are resistant
  • Bacitracin Sensitivity: Staphylococci are resistant to higher concentrations; Micrococci susceptible
  • Microdase Test: Staphylococci are negative; Micrococci are positive
  • Oxygen Requirements: Staphylococci are facultative anaerobes; Micrococci are obligate aerobes
  • Carbohydrate Utilization: Staphylococci fermentatively; Micrococci oxidatively or not at all

Current Classification of Staphylococci

  • ~32 species
  • Coagulase-positive: S. aureus, S. intermedius, S. pseudintermedius, S. hyicus, S. delphini, S. lutrae, S. agnetis
  • Coagulase-negative: S. epidermidis, S.hemolyticus, S. saprophyticus, S. hominis, S. capitis

Staphylococcus aureus

  • Morphology: Gram-positive cocci in clusters, often pairs or short chains
  • Virulence Factors: Enterotoxins, toxic shock syndrome toxin 1 (TSST-1), exfoliative toxins, cytolytic toxins, enzymes, and Protein A
  • Clinical Significance: Important pathogen responsible for many types of infections
  • Culture Characteristics: Grows at 10-42°C (optimum 37°C), pH 7.4-7.6. Creates large, circular, smooth, shiny, opaque, and easily emulsifiable colonies. Yellow-pigmented colonies which do not diffuse into the medium, the pigment is carotene-like lipoprotein. Optimally, this pigment production occurs at 22C or when specific substances are added.
  • Biochemical Reactions: Catalase +, Indole -, VP +, MR +, Urease +, Nitrate reduction +, Phosphatase +, Mannitol fermentation +

Additional Staphylococcus aureus Information

  • Most virulent species. Coagulase (+)
  • Colonies appear golden yellow
  • B-hemolytic on blood agar
  • Can be cultivated in media with 7.5-10% NaCl
  • Predominantly responsible for skin, wound, and deep tissue infections
  • Food Poisoning: Associated with enterotoxins (A, B, and D)
  • Scalded Skin Syndrome (SSS): Epidermolytic toxins A and B cause exfoliation of the epidermis
  • Toxic Shock Syndrome (TSS): TSST-1 induces an extensive, potentially fatal, systemic reaction.
  • Deep Infections: Osteomyelitis, septic arthritis
  • Cutaneous infections: Folliculitis, furuncles (boils), carbuncles, impetigo, abscess

Additional Staphylococcal Information (from other pages)

  • Deoxyribonuclease (DNase) & Phosphatase: Lowers exudate viscosity; destroys DNA
  • B-Lactamase: Breaks down penicillin; common in clinical isolates
  • Enterotoxin (Heat-stable): Vomiting stimulator caused by vagus nerve stimulation
  • Leukocidin / Panton-Valentine Leukocidin (PVL): Lethal to neutrophils; pore-forming exotoxin
  • Hemolysin (Cytotoxin): Causes anemia; involved in iron acquisition, including types alpha, beta, and gamma
  • Exfoliatin Serotypes A & B: Disrupt epidermal cell junctions
  • Tests for Identification: Coagulase, mannitol fermentation, catalase, novobiocin susceptibility, and more.
  • Methicillin-Resistant Staphylococcus aureus (MRSA) : Resistant to common antibiotics, commonly hospital-acquired
  • Coagulase-negative Staphylococcus (CONS): Do not produce exotoxins causing TSS

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Description

Test your knowledge on Staphylococcus and Micrococcus! This quiz covers their morphological differences, clinical significance, and sensitivity to various agents. Explore the vital role these bacteria play in human health and disease.

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