Pass the ASCP MLS certification test by using our 80 free multiple-choice questions (1911–1990) to identify Gram-positive cocci. Discover how to recognize staphylococcus, streptococcus, and enterococcus species using microbiology.
To prepare for the ASCP MLS certification exam, a solid understanding of bacterial identification is required, particularly of Gram-positive cocci, which are common in diagnostic microbiology. This section includes 80 multiple-choice questions (questions 1911-1990) covering the identification and differentiation of medically important Gram-positive cocci, such as Staphylococcus, Streptococcus, and Enterococcus.
Key Identification Methods Covered:
The multiple-choice questions covered basic microbiological concepts and laboratory techniques, such as:
- The catalase test distinguishes Staphylococcus (positive) from Streptococcus/Enterococcus (negative).
- The coagulase test differentiates Staphylococcus aureus from coagulase-negative staphylococci (CNS).
- Novobiocin resistance: Distinguishes resistant S. saprophyticus from susceptible S. epidermidis.
- Optochin sensitivity and bile solubility are indicators of Streptococcus pneumoniae.
- Bacitracin sensitivity: Detects Streptococcus pyogenes (group A).
- The CAMP test confirms the presence of Streptococcus agalactiae (group B).
- PYR test: Both S. pyogenes and Enterococcus are positive.
- Growth in 6.5% NaCl and bile esculin: Differentiation between group D enterococci and Streptococcus bovis.
- Staphylococcus aureus is identified by agglutination to latex, also known as protein A.
- Mannitol Salt Agar: Selective/differential medium for Staphylococcus aureus.
83 MCQs (1911-1990):
- Which of the following tests is used to differentiate Staphylococcus aureus from other staphylococci?
a) Oxidase
b) Coagulase
c) Catalase
d) Optochin susceptibility - A catalase-positive, gram-positive coccus in clusters that is coagulase-negative is most likely:
a) Staphylococcus aureus
b) Staphylococcus epidermidis
c) Streptococcus pyogenes
d) Enterococcus faecalis - Which organism is bacitracin-sensitive and beta-hemolytic?
a) Streptococcus agalactiae
b) Streptococcus pneumoniae
c) Streptococcus pyogenes
d) Enterococcus faecium - The CAMP test is used to identify:
a) Staphylococcus aureus
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecalis - Which of the following organisms is PYR-positive?
a) Streptococcus pyogenes
b) Staphylococcus epidermidis
c) Streptococcus pneumoniae
d) Micrococcus luteus - A gram-positive coccus that grows in 6.5% NaCl and hydrolyzes bile esculin is most likely:
a) Streptococcus bovis
b) Enterococcus faecalis
c) Streptococcus pneumoniae
d) Staphylococcus saprophyticus - Which test differentiates Streptococcus pneumoniae from other alpha-hemolytic streptococci?
a) Catalase
b) Bile solubility
c) Coagulase
d) Urease - A gram-positive coccus that is optochin-sensitive is:
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecalis - Which organism is associated with neonatal sepsis and is group B streptococcus?
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecalis - A gram-positive coccus that is catalase-negative and beta-hemolytic could be:
a) Staphylococcus aureus
b) Streptococcus pyogenes
c) Micrococcus luteus
d) Staphylococcus epidermidis - Which of the following is a characteristic of Enterococcus species?
a) Sensitive to penicillin
b) Does not grow in 6.5% NaCl
c) Hydrolyzes hippurate
d) Resistant to vancomycin - A gram-positive coccus that is bile esculin-positive but does not grow in 6.5% NaCl is likely:
a) Enterococcus faecalis
b) Streptococcus bovis
c) Streptococcus pyogenes
d) Staphylococcus aureus - Which of the following organisms is coagulase-positive?
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
c) Staphylococcus aureus
d) Streptococcus pyogenes - The latex agglutination test for protein A is used to identify:
a) Streptococcus pneumoniae
b) Staphylococcus aureus
c) Enterococcus faecalis
d) Streptococcus agalactiae - Which organism is associated with urinary tract infections in young women?
a) Staphylococcus aureus
b) Staphylococcus saprophyticus
c) Streptococcus pyogenes
d) Enterococcus faecium - A gram-positive coccus that is catalase-negative and alpha-hemolytic could be:
a) Streptococcus pyogenes
b) Streptococcus pneumoniae
c) Staphylococcus epidermidis
d) Enterococcus faecalis - Which organism is bile esculin-positive and PYR-positive?
a) Streptococcus bovis
b) Enterococcus faecalis
c) Streptococcus pneumoniae
d) Staphylococcus aureus - The reverse CAMP test is used to identify:
a) Staphylococcus aureus
b) Clostridium perfringens
c) Streptococcus agalactiae
d) Enterococcus faecalis - Which organism is associated with infective endocarditis and is part of the viridans group?
a) Streptococcus pyogenes
b) Streptococcus mutans
c) Staphylococcus aureus
d) Enterococcus faecalis - A gram-positive coccus that is catalase-positive and novobiocin-resistant is:
a) Staphylococcus aureus
b) Staphylococcus saprophyticus
c) Staphylococcus epidermidis
d) Micrococcus luteus - Which organism is DNase-positive and coagulase-positive?
a) Staphylococcus epidermidis
b) Staphylococcus aureus
c) Streptococcus pyogenes
d) Enterococcus faecalis - A gram-positive coccus that is catalase-negative and gamma-hemolytic is likely:
a) Streptococcus pneumoniae
b) Enterococcus faecalis
c) Streptococcus pyogenes
d) Staphylococcus aureus - Which organism is associated with toxic shock syndrome?
a) Streptococcus pyogenes
b) Staphylococcus aureus
c) Enterococcus faecalis
d) Streptococcus agalactiae - Which test differentiates Staphylococcus from Micrococcus?
a) Oxidase
b) Catalase
c) Coagulase
d) Bile solubility - A gram-positive coccus that is optochin-resistant and alpha-hemolytic is likely:
a) Streptococcus pneumoniae
b) Viridans streptococci
c) Streptococcus pyogenes
d) Enterococcus faecalis - Which organism is associated with post-streptococcal glomerulonephritis?
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecalis - A gram-positive coccus that is catalase-positive and novobiocin-sensitive is:
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
c) Staphylococcus aureus
d) Micrococcus luteus - Which organism is associated with dental caries?
a) Streptococcus mutans
b) Streptococcus pyogenes
c) Staphylococcus aureus
d) Enterococcus faecalis - A gram-positive coccus that is catalase-negative and beta-hemolytic but bacitracin-resistant is likely:
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecalis - Which organism is associated with food poisoning due to enterotoxin production?
a) Staphylococcus aureus
b) Streptococcus pyogenes
c) Enterococcus faecalis
d) Streptococcus pneumoniae - Which test differentiates Staphylococcus from Streptococcus?
a) Coagulase
b) Catalase
c) Optochin sensitivity
d) Bile solubility - Staphylococci are typically arranged in:
a) Chains
b) Pairs
c) Clusters
d) Tetrads - Which Staphylococcus species is coagulase-positive?
a) S. epidermidis
b) S. saprophyticus
c) S. aureus
d) S. lugdunensis - What test helps distinguish S. aureus from other staphylococci?
a) EMB agar fermentation
b) Coagulase test
c) Optochin
d) Hippurate hydrolysis - Which species is resistant to novobiocin?
a) S. epidermidis
b) S. saprophyticus
c) S. aureus
d) S. pneumoniae - Enterococci can be identified by their:
a) Catalase positivity
b) Bile esculin positivity and growth in 6.5% NaCl
c) Optochin sensitivity
d) Mannitol fermentation - Which test is used to differentiate S. pneumoniae from viridans streptococci?
a) Bile esculin
b) Hippurate hydrolysis
c) Optochin sensitivity
d) Coagulase - Alpha-hemolytic, bile-soluble diplococci most likely indicate:
a) S. pyogenes
b) S. agalactiae
c) S. pneumoniae
d) Enterococcus faecalis - Group A Streptococcus (S. pyogenes) can cause:
a) Endocarditis
b) Scarlet fever
c) Urinary tract infections
d) Dental caries - Viridans streptococci are characterized by:
a) Catalase positivity
b) Lancefield Group B antigen
c) Alpha-hemolysis and no Lancefield grouping
d) Resistance to optochin - The catalase test uses which reagent to produce bubbles?
a) Iodine
b) Hydrogen peroxide
c) Crystal violet
d) Bile salt - Which bacteria are coagulase-negative but novobiocin-sensitive?
a) S. aureus
b) S. saprophyticus
c) S. epidermidis
d) Enterococcus faecalis - A bacterium that hydrolyzes esculin in the presence of bile is likely:
a) S. pyogenes
b) S. pneumoniae
c) Enterococcus
d) S. aureus - Group B Streptococcus (S. agalactiae) shows which of the following?
a) Optochin sensitivity
b) CAMP positivity
c) Bile solubility
d) Coagulase positivity - The Lancefield grouping classifies streptococci based on:
a) Hemolysis type
b) Catalase reaction
c) Cell-wall carbohydrates
d) Coagulase productio - Which feature is characteristic of gram-positive bacteria in general?
a) Thin peptidoglycan layer
b) Outer membrane
c) Thick peptidoglycan layer retaining crystal violet stain
d) Lipopolysaccharide in cell wall - Which test indicates Group D Streptococci?
a) Hippurate hydrolysis negative
b) Bile esculin positive
c) Optochin positive
d) Coagulase positive - Which Staphylococcus species is part of normal skin flora but important in prosthetic device infections?
a) S. aureus
b) S. saprophyticus
c) S. epidermidis
d) S. pneumoniae - Which pathogen is commonly implicated in dental caries?
a) Enterococcus faecalis
b) S. mutans (Viridans)
c) S. agalactiae
d) S. aureus - Which streptococcus is encapsulated, alpha-hemolytic, and lancet-shaped?
a) S. pyogenes
b) S. agalactiae
c) S. pneumoniae
d) E. faecalis - The catalase test distinguishes which two genera?
a) Staphylococcus vs Enterococcus
b) Staphylococcus vs Streptococcus
c) Streptococcus vs Enterococcus
d) All of the above - S. aureus on Mannitol Salt Agar produces:
a) No growth
b) Red colonies
c) Yellow colonies due to mannitol fermentation
d) Black precipitate - Which genus is catalase-negative and forms chains?
a) Staphylococcus
b) Streptococcus
c) Micrococcus
d) Bacillus - Which group causes impetigo and pharyngitis?
a) Viridans streptococci
b) Enterococcus
c) Group A Streptococcus (S. pyogenes)
d) S. aureus - Growth in 6.5% NaCl indicates:
a) Viridans streptococci
b) Enterococcus
c) S. pneumoniae
d) S. agalactiae - Which test is not used to identify streptococci?
a) Optochin
b) Coagulase
c) Hippurate hydrolysis
d) Bile esculin - Diagnosis of S. pneumoniae includes which property?
a) Latex agglutination of coagulase
b) Bile solubility
c) Novobiocin resistance
d) Catalase positivity - Which species is a common cause of UTIs in young women?
a) S. aureus
b) S. epidermidis
c) S. saprophyticus
d) Enterococcus faecalis - Catalase-positive, coagulase-negative staphylococci are referred to as:
a) Group A Strep
b) Viridans streptococci
c) Coagulase-negative staphylococci (CoNS)
d) Micrococci - S. pyogenes virulence factors include all of the following except:
a) M protein
b) Streptokinase
c) Endotoxin
d) Streptolysin - Which biochemical test is most useful for differentiating Staphylococcus from Streptococcus?
a) Catalase
b) Oxidase
c) Coagulase
d) Bile solubility - A beta-hemolytic, catalase-negative, bacitracin-resistant gram-positive coccus is most likely:
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Enterococcus faecalis
d) Streptococcus pneumoniae - Which organism is PYR-positive and grows in 6.5% NaCl?
a) Streptococcus bovis
b) Enterococcus faecalis
c) Streptococcus pneumoniae
d) Staphylococcus epidermidis - The CAMP test demonstrates enhanced hemolysis due to:
a) Synergistic action with Staphylococcus aureus beta-lysin
b) Production of streptolysin O
c) Bile solubility
d) Optochin sensitivity - Which Staphylococcus species is coagulase-positive?
a) S. epidermidis
b) S. saprophyticus
c) S. aureus
d) S. lugdunensis - A gram-positive coccus that is optochin-sensitive and alpha-hemolytic is:
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecium - Which test differentiates Enterococcus from Streptococcus bovis?
a) Growth in 6.5% NaCl
b) Bile esculin hydrolysis
c) Catalase
d) PYR - A catalase-positive, coagulase-negative, novobiocin-resistant Staphylococcus is:
a) S. aureus
b) S. epidermidis
c) S. saprophyticus
d) S. haemolyticus - Which organism is associated with infective endocarditis in patients with colon cancer?
a) Streptococcus pyogenes
b) Streptococcus bovis
c) Staphylococcus aureus
d) Enterococcus faecalis - A gram-positive coccus that is bile esculin-positive but does not grow in 6.5% NaCl is:
a) Enterococcus faecalis
b) Streptococcus bovis
c) Streptococcus pneumoniae
d) Staphylococcus epidermidis - Which organism is DNase-positive and causes food poisoning?
a) Staphylococcus epidermidis
b) Staphylococcus aureus
c) Streptococcus pyogenes
d) Enterococcus faecalis - The latex agglutination test for protein A detects:
a) Streptococcus pneumoniae
b) Staphylococcus aureus
c) Enterococcus faecalis
d) Streptococcus agalactiae - Which Staphylococcus species is a common cause of UTIs in young women?
a) S. aureus
b) S. saprophyticus
c) S. epidermidis
d) S. haemolyticus - A gram-positive coccus that is catalase-negative and gamma-hemolytic could be:
a) Streptococcus pneumoniae
b) Enterococcus faecalis
c) Streptococcus pyogenes
d) Staphylococcus aureus - Which organism is associated with scarlet fever?
a) Streptococcus pyogenes
b) Streptococcus agalactiae
c) Streptococcus pneumoniae
d) Enterococcus faecalis - A urease-positive, catalase-positive, coagulase-negative, novobiocin-resistant gram-positive coccus is most likely:
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
c) Streptococcus bovis
d) Enterococcus faecalis - Which test is not useful for differentiating Streptococcus pneumoniae from Viridans streptococci?
a) Optochin sensitivity
b) Bile solubility
c) Novobiocin susceptibility
d) Alpha-hemolysis - Which biochemical test is commonly used to classify streptococci into Lancefield groups?
a) PYR test
b) Hippurate hydrolysis
c) Cell-wall carbohydrate serology
d) Catalase test - Which biochemical feature is specific to gram-positive bacteria in general?
a) Presence of teichoic acids in the cell wall
b) Outer membrane containing lipopolysaccharide
c) Thin peptidoglycan layer
d) Production of exotoxin - A gram-positive coccus that is oxidase-negative, urease-positive, and novobiocin-sensitive is likely:
a) Staphylococcus epidermidis
b) Staphylococcus saprophyticus
c) Enterococcus faecalis
d) Streptococcus pneumoniae
Answer Key
Answer Key:
- b) Coagulase
- b) Staphylococcus epidermidis
- c) Streptococcus pyogenes
- b) Streptococcus agalactiae
- a) Streptococcus pyogenes
- b) Enterococcus faecalis
- b) Bile solubility
- c) Streptococcus pneumoniae
- b) Streptococcus agalactiae
- b) Streptococcus pyogenes
- d) Resistant to vancomycin
- b) Streptococcus bovis
- c) Staphylococcus aureus
- b) Staphylococcus aureus
- b) Staphylococcus saprophyticus
- b) Streptococcus pneumoniae
- b) Enterococcus faecalis
- b) Clostridium perfringens
- b) Streptococcus mutans
- b) Staphylococcus saprophyticus
- b) Staphylococcus aureus
- b) Enterococcus faecalis
- b) Staphylococcus aureus
- a) Oxidase
- b) Viridans streptococci
- a) Streptococcus pyogenes
- a) Staphylococcus epidermidis
- a) Streptococcus mutans
- b) Streptococcus agalactiae
- a) Staphylococcus aureus
- b) Catalase
- c) Clusters
- c) S. aureus
- b) Coagulase test
- b) S. saprophyticus
- b) Bile esculin positivity and growth in 6.5% NaCl
- c) Optochin sensitivity
- c) S. pneumoniae
- b) Scarlet fever
- c) Alpha-hemolysis and no Lancefield grouping
- b) Hydrogen peroxide
- c) S. epidermidis
- c) Enterococcus
- b) CAMP positivity
- c) Cell-wall carbohydrates
- c) Thick peptidoglycan layer retaining crystal violet stain
- b) Bile esculin positive
- c) S. epidermidis
- b) S. mutans (Viridans)
- c) S. pneumoniae
- a) Catalase
- b) Streptococcus agalactiae
- b) Enterococcus faecalis
- a) Synergistic action with Staphylococcus aureus beta-lysin
- c) S. aureus
- c) Streptococcus pneumoniae
- a) Growth in 6.5% NaCl
- c) S. saprophyticus
- b) Streptococcus bovis
- b) Streptococcus bovis
- b) Staphylococcus vs Streptococcus
- c) Yellow colonies due to mannitol fermentation
- b) Streptococcus
- c) Group A Streptococcus (S. pyogenes)
- b) Enterococcus
- b) Coagulase
- b) Bile solubility
- c) S. saprophyticus
- c) Coagulase-negative staphylococci (CoNS)
- c) Endotoxin
- b) Staphylococcus aureus
- b) Staphylococcus aureus
- b) S. saprophyticus
- b) Enterococcus faecalis
- a) Streptococcus pyogenes
- b) Staphylococcus saprophyticus
- c) Novobiocin susceptibility
- c) Cell-wall carbohydrate serology
- a) Presence of teichoic acids in the cell wall
- a) Staphylococcus epidermidis
Top 8 Medical Laboratory Scientist (MLS) Exams:
Top 8 Medical Laboratory Scientist (MLS) Exams that are recognized globally and can help professionals validate their credentials and enhance their career opportunities:
1. ASCP – American Society for Clinical Pathology (USA)
- Exam Name: MLS(ASCP)
- Eligibility: Bachelor’s degree with clinical laboratory experience.
- Global Recognition: High
- Purpose: Certifies Medical Laboratory Scientists in the United States and internationally.
2. AMT – American Medical Technologists (USA)
- Exam Name: MLT(AMT) or MT(AMT)
- Eligibility: Academic and/or work experience in medical laboratory technology.
- Global Recognition: Moderate
- Purpose: Credentialing for medical technologists and technicians.
3. AIMS – Australian Institute of Medical and Clinical Scientists
- Exam Name: AIMS Certification Exam
- Eligibility: Assessment of qualifications and work experience.
- Recognition: Required for practice in Australia.
- Purpose: Certification and registration in Australia.
4. CSMLS – Canadian Society for Medical Laboratory Science
- Exam Name: CSMLS General or Subject-specific Exams
- Eligibility: Graduation from a CSMLS-accredited program or equivalent.
- Recognition: Canada
- Purpose: Entry-to-practice certification in Canada.
5. IBMS – Institute of Biomedical Science (UK)
- Exam Name: Registration and Specialist Portfolio Assessment
- Eligibility: Accredited degree and lab experience.
- Recognition: UK and some Commonwealth countries.
- Purpose: Biomedical Scientist registration with the HCPC (UK).
6. HAAD / DOH – Department of Health, Abu Dhabi (UAE)
- Exam Name: DOH/HAAD License Exam
- Eligibility: Degree in medical laboratory science and experience.
- Recognition: UAE (Abu Dhabi)
- Purpose: Licensure for medical laboratory practice in Abu Dhabi.
7. DHA – Dubai Health Authority (UAE)
- Exam Name: DHA License Exam for Medical Laboratory Technologists
- Eligibility: Relevant degree and experience.
- Recognition: Dubai, UAE
- Purpose: Professional license for clinical laboratory practice in Dubai.
8. MOH – Ministry of Health (Gulf Countries like UAE, Saudi Arabia, Kuwait)
- Exam Name: MOH License Exam
- Eligibility: BSc/Diploma in Medical Laboratory + experience.
- Recognition: Varies by country.
- Purpose: Required for practicing in public and private sector labs.
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