You can prepare for your ASCP MLS certification by taking Part 24 of our free microbiology practice course, which focuses on recognizing Gram-negative bacilli. Your knowledge of common illnesses, such as Salmonella, Escherichia coli, Klebsiella, Proteus, Pseudomonas, Shigella, Vibrio, Campylobacter, and many more, will be tested by the 80 multiple-choice questions (MCQs) in this series. By using these questions, you can improve your exam preparation and gain confidence in laboratory microbiology.
For your ASCP MLS test, master the identification of Gram-negative bacilli by using our free 80-MCQ microbiology practice course. To help you pass the test, it offers crucial illnesses, biochemical testing, and clinical correlations.
80 MCQs (1991-2070):
- Which of the following is a key characteristic of Escherichia coli?
a) Oxidase-positive
b) Indole-positive
c) Non-motile
d) H2S producer - Klebsiella pneumoniae is distinguished from Escherichia coli by being:
a) Lactose fermenter
b) Indole-negative
c) Oxidase-positive
d) Motile - Which organism is known for swarming motility on blood agar?
a) Proteus mirabilis
b) Pseudomonas aeruginosa
c) Salmonella typhi
d) Shigella sonnei - Salmonella species are typically:
a) Lactose fermenters
b) H2S producers
c) Indole-positive
d) Oxidase-positive - Which biochemical test is used to differentiate Proteus from Salmonella?
a) Urease
b) Citrate
c) Oxidase
d) Phenylalanine deaminase - Pseudomonas aeruginosa produces which pigment?
a) Red
b) Blue-green (pyocyanin)
c) Yellow
d) Black - Which of the following is oxidase-positive?
a) Escherichia coli
b) Klebsiella pneumoniae
c) Pseudomonas aeruginosa
d) Proteus mirabilis - Shigella species are:
a) Motile
b) Lactose fermenters
c) Non-motile
d) H2S producers - Which organism is associated with urinary tract infections and is indole-positive?
a) Proteus mirabilis
b) Klebsiella pneumoniae
c) Escherichia coli
d) Salmonella enterica - Vibrio cholerae grows best on which medium?
a) MacConkey agar
b) TCBS agar
c) Blood agar
d) Hektoen enteric agar - Which of the following is a non-fermenter?
a) Escherichia coli
b) Pseudomonas aeruginosa
c) Klebsiella pneumoniae
d) Proteus mirabilis - Campylobacter jejuni requires which special incubation condition?
a) Aerobic
b) Microaerophilic
c) Anaerobic
d) Capnophilic - Which organism is associated with gastritis and peptic ulcers?
a) Helicobacter pylori
b) Vibrio cholerae
c) Salmonella typhi
d) Shigella dysenteriae - Legionella pneumophila is best cultured on:
a) Blood agar
b) Chocolate agar
c) Buffered charcoal yeast extract (BCYE) agar
d) MacConkey agar - Which of the following is urease-positive?
a) Escherichia coli
b) Proteus mirabilis
c) Shigella flexneri
d) Salmonella typhi - Bordetella pertussis is cultured on:
a) Blood agar
b) Regan-Lowe agar
c) MacConkey agar
d) TCBS agar - Which organism is oxidase-positive and ferments glucose oxidatively?
a) Escherichia coli
b) Pseudomonas aeruginosa
c) Klebsiella pneumoniae
d) Proteus mirabilis - Yersinia pestis causes which disease?
a) Cholera
b) Plague
c) Typhoid fever
d) Dysentery - Which organism is associated with wound infections after exposure to seawater?
a) Vibrio vulnificus
b) Salmonella typhi
c) Shigella sonnei
d) Escherichia coli - Haemophilus influenzae requires which growth factors?
a) X and V factors
b) Hemin and NAD
c) Both “X and V factors” and “Hemin and NAD”
d) None of the above - Which organism is a common cause of nosocomial pneumonia in cystic fibrosis patients?
a) Pseudomonas aeruginosa
b) Escherichia coli
c) Klebsiella pneumoniae
d) Proteus mirabilis - Which test is used to differentiate Neisseria from Moraxella?
a) Oxidase
b) Carbohydrate utilization
c) Catalase
d) Indole - Which organism is associated with melioidosis?
a) Burkholderia pseudomallei
b) Pseudomonas aeruginosa
c) Acinetobacter baumannii
d) Stenotrophomonas maltophilia - Acinetobacter baumannii is:
a) Oxidase-positive
b) Motile
c) Oxidase-negative
d) Lactose fermenter - Which organism is commonly linked to foodborne outbreaks due to undercooked poultry?
a) Campylobacter jejuni
b) Salmonella typhi
c) Shigella dysenteriae
d) Vibrio cholerae - Which organism is associated with “rice-water stools”?
a) Vibrio cholerae
b) Escherichia coli
c) Shigella sonnei
d) Salmonella enterica - Which of the following is a rapid urease-positive organism?
a) Helicobacter pylori
b) Proteus mirabilis
c) Klebsiella pneumoniae
d) Escherichia coli - Serratia marcescens is known for producing:
a) Blue pigment
b) Red pigment
c) Green pigment
d) Yellow pigment - Which organism is commonly resistant to multiple antibiotics, including carbapenems?
a) Escherichia coli
b) Klebsiella pneumoniae
c) Pseudomonas aeruginosa
d) Proteus mirabilis - Which organism is associated with “bull’s-eye” colonies on CIN agar?
a) Yersinia enterocolitica
b) Salmonella typhi
c) Shigella flexneri
d) Vibrio parahaemolyticus - Which test differentiates Escherichia coli from Enterobacter cloacae?
a) Citrate utilization
b) Indole test
c) Oxidase test
d) Urease test - Which Gram-negative bacillus is commonly associated with pneumonia in alcoholics?
a) Pseudomonas aeruginosa
b) Klebsiella pneumoniae
c) Escherichia coli
d) Proteus mirabilis - Which organism is known for producing a fruity odor in culture?
a) Pseudomonas aeruginosa
b) Salmonella enterica
c) Shigella sonnei
d) Acinetobacter baumannii - Which organism produces black colonies on Hektoen enteric agar due to H2S production?
a) Escherichia coli
b) Salmonella enterica
c) Shigella flexneri
d) Klebsiella oxytoca - Which feature best distinguishes Shigella from Salmonella?
a) Lactose fermentation
b) Motility
c) Indole test
d) Oxidase reaction - Yersinia enterocolitica infections are most often associated with which food source?
a) Undercooked beef
b) Contaminated pork
c) Seafood
d) Dairy products - Which organism is often resistant to colistin and associated with hospital outbreaks?
a) Klebsiella pneumoniae
b) Pseudomonas aeruginosa
c) Acinetobacter baumannii
d) Serratia marcescens - Which Gram-negative bacillus produces a “safety-pin” appearance on bipolar staining?
a) Salmonella typhi
b) Yersinia pestis
c) Vibrio cholerae
d) Shigella sonnei - Which organism causes “red leg” infections in fish handlers?
a) Vibrio parahaemolyticus
b) Aeromonas hydrophila
c) Pseudomonas aeruginosa
d) Proteus vulgaris - Which test is most reliable for distinguishing Pseudomonas aeruginosa from Enterobacteriaceae?
a) Lactose fermentation
b) Oxidase test
c) Urease test
d) Indole test - Which non-lactose fermenter is associated with gastroenteritis after shellfish consumption?
a) Salmonella enterica
b) Shigella dysenteriae
c) Vibrio parahaemolyticus
d) Escherichia coli - Which Gram-negative bacillus is associated with neonatal meningitis due to K1 antigen?
a) Escherichia coli
b) Klebsiella pneumoniae
c) Serratia marcescens
d) Proteus mirabilis - Which organism produces DNase and lipase, and is often found in contaminated IV fluids?
a) Pseudomonas aeruginosa
b) Serratia marcescens
c) Enterobacter cloacae
d) Acinetobacter baumannii - Which test differentiates Proteus mirabilis from Proteus vulgaris?
a) Indole test
b) Citrate test
c) Urease test
d) Oxidase test - Which Gram-negative bacillus is commonly associated with “traveler’s diarrhea”?
a) Salmonella enterica
b) Escherichia coli (ETEC)
c) Shigella dysenteriae
d) Vibrio vulnificus - Which organism grows at 42°C and is a leading cause of bacterial gastroenteritis worldwide?
a) Campylobacter jejuni
b) Vibrio cholerae
c) Escherichia coli
d) Klebsiella pneumoniae - Which organism produces a mucoid colony due to a polysaccharide capsule?
a) Klebsiella pneumoniae
b) Escherichia coli
c) Salmonella paratyphi
d) Shigella flexneri - Which Gram-negative bacillus is linked with “rose spots” on the abdomen during infection?
a) Shigella dysenteriae
b) Salmonella typhi
c) Vibrio vulnificus
d) Escherichia coli - Which organism is often isolated from respiratory infections in cystic fibrosis patients alongside Pseudomonas?
a) Stenotrophomonas maltophilia
b) Proteus mirabilis
c) Serratia marcescens
d) Salmonella enterica - Which Gram-negative bacillus is most likely to show “triple sugar iron (TSI) slant with red slant/yellow butt and no gas or H2S”?
a) Shigella sonnei
b) Escherichia coli
c) Salmonella enterica
d) Proteus vulgaris - Which organism is indole-positive, oxidase-negative, and ferments lactose?
a) Pseudomonas aeruginosa
b) Klebsiella pneumoniae
c) Escherichia coli
d) Proteus mirabilis - A gram-negative bacillus that swarms on blood agar and is urease-positive is likely:
a) Salmonella enterica
b) Proteus mirabilis
c) Shigella flexneri
d) Acinetobacter baumannii - Which organism requires X and V factors for growth?
a) Neisseria meningitidis
b) Haemophilus influenzae
c) Bordetella pertussis
d) Legionella pneumophila - TCBS agar is selective for which pathogen?
a) Salmonella typhi
b) Vibrio cholerae
c) Campylobacter jejuni
d) Helicobacter pylori - A non-lactose fermenter that produces H₂S on TSI agar is:
a) Escherichia coli
b) Klebsiella pneumoniae
c) Salmonella enterica
d) Enterobacter cloacae - Which organism is oxidase-positive and produces pyocyanin?
a) Stenotrophomonas maltophilia
b) Pseudomonas aeruginosa
c) Acinetobacter baumannii
d) Serratia marcescens - Campylobacter jejuni grows optimally under:
a) Aerobic conditions at 37°C
b) Microaerophilic conditions at 42°C
c) Anaerobic conditions at 25°C
d) Capnophilic conditions at 30°C - The “string test” is used to identify:
a) Vibrio cholerae
b) Helicobacter pylori
c) Bacillus anthracis
d) Yersinia pestis - Which organism is associated with gastric ulcers and is urease-positive?
a) Salmonella typhi
b) Helicobacter pylori
c) Shigella dysenteriae
d) Proteus vulgaris - Legionella pneumophila is best isolated using:
a) MacConkey agar
b) Buffered charcoal yeast extract (BCYE) agar
c) Hektoen enteric agar
d) Chocolate agar - A gram-negative bacillus that oxidizes glucose, is non-motile, and causes nosocomial pneumonia is:
a) Escherichia coli
b) Acinetobacter baumannii
c) Klebsiella pneumoniae
d) Pseudomonas aeruginosa - Which organism produces red pigment at room temperature?
a) Pseudomonas aeruginosa
b) Serratia marcescens
c) Enterobacter aerogenes
d) Proteus mirabilis - CIN agar is used to isolate:
a) Yersinia enterocolitica
b) Vibrio parahaemolyticus
c) Campylobacter fetus
d) Salmonella typhi - A gram-negative bacillus that is oxidase-positive and ferments glucose in OF medium is:
a) Alcaligenes faecalis
b) Pseudomonas fluorescens
c) Aeromonas hydrophila
d) Stenotrophomonas maltophilia - Which organism causes whooping cough?
a) Bordetella pertussis
b) Haemophilus ducreyi
c) Mycoplasma pneumoniae
d) Legionella pneumophila - The satellite phenomenon is characteristic of:
a) Streptococcus pneumoniae
b) Haemophilus influenzae
c) Neisseria gonorrhoeae
d) Staphylococcus aureus - Burkholderia cepacia is associated with:
a) Urinary tract infections
b) Respiratory infections in cystic fibrosis patients
c) Foodborne gastroenteritis
d) Skin abscesses - Which organism is non-motile and non-lactose fermenting?
a) Escherichia coli
b) Shigella sonnei
c) Enterobacter cloacae
d) Proteus vulgaris - A gram-negative bacillus that grows on MacConkey agar and decarboxylates lysine is:
a) Salmonella enterica
b) Proteus mirabilis
c) Morganella morganii
d) Providencia stuartii - Vibrio vulnificus is transmitted through:
a) Contaminated water
b) Undercooked shellfish
c) Airborne droplets
d) Soil contact - Which organism is phenylalanine deaminase (PAD) positive?
a) Klebsiella oxytoca
b) Proteus vulgaris
c) Serratia marcescens
d) Citrobacter freundii - Stenotrophomonas maltophilia is intrinsically resistant to:
a) Penicillin
b) Carbapenems
c) Aminoglycosides
d) Vancomycin - Which gram-negative bacillus is indole-positive and motile?
a) Klebsiella pneumoniae
b) Shigella flexneri
c) Escherichia coli
d) Salmonella typhi - The “gull-wing” appearance in microscopy is characteristic of:
a) Vibrio cholerae
b) Campylobacter jejuni
c) Helicobacter pylori
d) Legionella pneumophila - Francisella tularensis requires which medium for growth?
a) Blood agar
b) Chocolate agar
c) Cysteine-enriched agar
d) MacConkey agar - Which organism causes melioidosis?
a) Burkholderia pseudomallei
b) Pseudomonas putida
c) Aeromonas caviae
d) Chromobacterium violaceum - A gram-negative bacillus that oxidizes lactose and produces a yellow pigment is:
a) Pseudomonas aeruginosa
b) Serratia marcescens
c) Elizabethkingia meningoseptica
d) Stenotrophomonas maltophilia - Yersinia pestis shows bipolar staining resembling:
a) “Safety pins”
b) “Curved rods”
c) “Chains”
d) “Clusters” - Which organism is urease-positive within minutes?
a) Proteus mirabilis
b) Helicobacter pylori
c) Klebsiella pneumoniae
d) Morganella morganii - Aeromonas hydrophila is differentiated from Vibrio by:
a) Oxidase reaction
b) Growth in 0% NaCl
c) Fermentation of sucrose
d) Motility
Answer Key
Answer Key:
- b) Indole-positive
- b) Indole-negative
- a) Proteus mirabilis
- b) H2S producers
- a) Urease
- b) Blue-green (pyocyanin)
- c) Pseudomonas aeruginosa
- c) Non-motile
- c) Escherichia coli
- b) TCBS agar
- a) Pseudomonas aeruginosa
- b) Carbohydrate utilization
- a) Burkholderia pseudomallei
- c) Oxidase-negative
- a) Campylobacter jejuni
- a) Vibrio cholerae
- a) Helicobacter pylori
- b) Red pigment
- b) Klebsiella pneumoniae
- a) Yersinia enterocolitica
- c) Vibrio parahaemolyticus
- a) Escherichia coli
- b) Serratia marcescens
- a) Indole test
- b) Escherichia coli (ETEC)
- a) Campylobacter jejuni
- a) Klebsiella pneumoniae
- b) Salmonella typhi
- a) Stenotrophomonas maltophilia
- a) Shigella sonnei
- b) Acinetobacter baumannii
- b) Serratia marcescens
- a) Yersinia enterocolitica
- c) Aeromonas hydrophila
- a) Bordetella pertussis
- b) Haemophilus influenzae
- b) Respiratory infections in cystic fibrosis patients
- b) Shigella sonnei
- a) Salmonella enterica
- b) Undercooked shellfish
- b) Pseudomonas aeruginosa
- b) Microaerophilic
- a) Helicobacter pylori
- c) Buffered charcoal yeast extract (BCYE) agar
- b) Proteus mirabilis
- b) Regan-Lowe agar
- b) Pseudomonas aeruginosa
- b) Plague
- a) Vibrio vulnificus
- c) Both “X and V factors” and “Hemin and NAD”
- b) Indole test
- b) Klebsiella pneumoniae
- a) Pseudomonas aeruginosa
- b) Salmonella enterica
- b) Motility
- b) Contaminated pork
- c) Acinetobacter baumannii
- b) Yersinia pestis
- b) Aeromonas hydrophila
- b) Oxidase test
- c) Escherichia coli
- b) Proteus mirabilis
- b) Haemophilus influenzae
- b) Vibrio cholerae
- c) Salmonella enterica
- b) Pseudomonas aeruginosa
- b) Microaerophilic conditions at 42°C
- a) Vibrio cholerae
- b) Helicobacter pylori
- b) Buffered charcoal yeast extract (BCYE) agar
- b) Proteus vulgaris
- b) Carbapenems
- c) Escherichia coli
- b) Campylobacter jejuni
- c) Cysteine-enriched agar
- a) Burkholderia pseudomallei
- c) Elizabethkingia meningoseptica
- a) “Safety pins”
- b) Helicobacter pylori
- b) Growth in 0% NaCl
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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