Block 9 Bacterial Genetic Xhange MCQ's

1. If your patient was infected with a Gram positive coccus that was catalase and coagulase positive, which organism would you expect to be the culprit?

Group A Strep

Staph. Aureus

Clostridium perfringens

Mycoplasma pneumonlae

Based on the information provided, the Gram positive coccus that is catalase and coagulase positive is most likely Staphylococcus aureus. Group A Streptococcus is usually catalase negative, and Clostridium perfringens is a Gram positive rod, not a coccus. Mycoplasma pneumoniae is a bacterium that lacks a cell wall and therefore would not be Gram positive. Staphylococcus aureus is a common cause of infections and is known to produce catalase and coagulase enzymes.

Explanation

Based on the information provided, the Gram positive coccus that is catalase and coagulase positive is most likely Staphylococcus aureus. Group A Streptococcus is usually catalase negative, and Clostridium perfringens is a Gram positive rod, not a coccus. Mycoplasma pneumoniae is a bacterium that lacks a cell wall and therefore would not be Gram positive. Staphylococcus aureus is a common cause of infections and is known to produce catalase and coagulase enzymes.

2. Your patient is a 19 year old student who presents with drowsiness, stiff neck and fever. Culture of the patient's blood reveals the presence of encapsulated Gram negative diplococci that can ferment glucose and maltose but not sucrose or lactose. Whch organism was most likely responsible for the patient's condition?

E. coil

Treponema pallidurn

Staph. aureus

Nelsseria meningitidis

Ecoli, is G- rod,
Treponema G- spirochaete,
SA is G+ coccus

Explanation

Ecoli, is G- rod,
Treponema G- spirochaete,
SA is G+ coccus

3. Cultures were collected from a patient. After 48 hours, the cultures were positive, and a Gram stain of the culture revealed large, spore-forming Gram-positive bacilli. To which of the following genera does this organism most likely belong?

Listeria spp

Corynebacterium spp.

Clostridium spp.

Actinomyces spp.

Nocardia spp.

The presence of large, spore-forming Gram-positive bacilli suggests that the organism belongs to the genus Clostridium. Clostridium species are known for their ability to form endospores, which are resistant structures that allow them to survive in harsh conditions. Additionally, Clostridium species are commonly found in clinical specimens and are associated with various infections, including botulism, tetanus, and gas gangrene. Therefore, based on the characteristics described, Clostridium spp. is the most likely genus for this organism.

Explanation

The presence of large, spore-forming Gram-positive bacilli suggests that the organism belongs to the genus Clostridium. Clostridium species are known for their ability to form endospores, which are resistant structures that allow them to survive in harsh conditions. Additionally, Clostridium species are commonly found in clinical specimens and are associated with various infections, including botulism, tetanus, and gas gangrene. Therefore, based on the characteristics described, Clostridium spp. is the most likely genus for this organism.

4. Cultures were collected from a patient. After 48 hours, the cultures were positive, and a Gram stain of the culture revealed large, spore-forming Gram-positive bacilli. which of the following statements best describes organisms that belong to this genus?

Saprophytic organisms found in the soil or intestinal tract of humans and animals

Facultative intracellular organisms

Infection occurs in immunocompromised individuals

Can be club-shaped or can resemble Chinese letters

Have a cell wall similar to that of mycobacteria

The given correct answer suggests that the organisms belonging to this genus are saprophytic, meaning they obtain their nutrients from dead organic matter, and can be found in the soil or the intestinal tract of humans and animals.

Explanation

The given correct answer suggests that the organisms belonging to this genus are saprophytic, meaning they obtain their nutrients from dead organic matter, and can be found in the soil or the intestinal tract of humans and animals.

5. Pseudomonas aeruginosa is a major problem in hospitals and can usually be found growing in the water used for flowers for patients. Which of the following characterizes P. aeruginosa?

Non motile Gram positive cocci

Motile Gram positive rods

Non motile Gram negative cocci

Motile Gram negative rods

Interesting factoid about P. aeruginosa.
It is found in tennis shoes under the insole. Therefore if pt steps on nail while wearing sneakers, there is a high likelyhood of P. aeruginosa infection.
Knowing this will make you seem like a genius to your future attending physician.

Explanation

Interesting factoid about P. aeruginosa.
It is found in tennis shoes under the insole. Therefore if pt steps on nail while wearing sneakers, there is a high likelyhood of P. aeruginosa infection.
Knowing this will make you seem like a genius to your future attending physician.

6. In May 2011, an outbreak of foodborne illness, complicated in many cases by hemolytic uremic syndrome, was seen in Germany. In thousands of patients, the causative agent was identified as a Shiga-toxin producing, Gram-negative, oxidase-negative rod that fermented lactose. A novel finding was that the isolates had the serotype O104:H4:K9, indicating that there was a common source for the infection and that it was a pathogen that had not previously been seen. What bacterial structures/components were useful in determining the serotype of this organism?

Flagella, lipid A, pili

Histones, peptidoglycan, teichoic acid

LPS, flagella, capsule

OMPs, haptens, kinetoplasts

Pili, transpeptidases, hemolysins

The serotype of the organism was determined by analyzing its bacterial structures/components, specifically LPS (lipopolysaccharide), flagella, and capsule. These structures are known to vary among different strains and serotypes of bacteria. By identifying the presence and characteristics of these structures, it was possible to determine that the causative agent in the outbreak had the serotype O104:H4:K9.

Explanation

The serotype of the organism was determined by analyzing its bacterial structures/components, specifically LPS (lipopolysaccharide), flagella, and capsule. These structures are known to vary among different strains and serotypes of bacteria. By identifying the presence and characteristics of these structures, it was possible to determine that the causative agent in the outbreak had the serotype O104:H4:K9.

7. Which of the following best describes the structural characteristics of spirochetes?

Spiral-shaped bacillus with typical Gram-negative cell wall; multiple polar flagella protruding from the cell

Bacillus with typical Gram-negative cell wall; multiple flagella that are distributed over the entire cell, protruding from the cell

Helical-shaped bacillus with typical Gram-negative cell wall; multiple flagella in space between inner and outer membranes

Curved bacillus with typical Gram-negative cell wall; single polar flagella

Bacillus with typical Gram-positive cell wall, non-motile

The correct answer describes spirochetes as helical-shaped bacilli with a typical Gram-negative cell wall. It also states that spirochetes have multiple flagella located in the space between the inner and outer membranes. This description accurately portrays the structural characteristics of spirochetes, which are spiral-shaped bacteria with a unique helical morphology. The presence of multiple flagella in the periplasmic space between the inner and outer membranes allows for their characteristic motility.

Explanation

The correct answer describes spirochetes as helical-shaped bacilli with a typical Gram-negative cell wall. It also states that spirochetes have multiple flagella located in the space between the inner and outer membranes. This description accurately portrays the structural characteristics of spirochetes, which are spiral-shaped bacteria with a unique helical morphology. The presence of multiple flagella in the periplasmic space between the inner and outer membranes allows for their characteristic motility.

8. An organism is isolated from urine collected from a patient with a urinary tract infection. This organism is gram-negative bacillus that grows at 37C in room air. It displays a swarming motility. The isolated organism most likely has which of the following biochemical profiles?

Ferments glucose, but does not ferment lactose

Ferments glucose and lactose

Does not ferment glucose or lactose

Does not ferment glucose but does ferment lactose

sounds like PROTEUS, "swarming motility"
Proteus causes UTI's, so think....there may be glucose in urine, but not lactose.

Explanation

sounds like PROTEUS, "swarming motility"
Proteus causes UTI's, so think....there may be glucose in urine, but not lactose.

9. Which of the following characteristics does Brucella spp., PasturelIa spp., and Francisella spp., have in common?

Facultative intracellular organisms

Fastidious and have special requirements for growth in culture

Infection is usually associated with contact with animals

Oxidase negative and ferment glucose

Pathogens of the human respiratory tract

Brucella spp., Pasturella spp., and Francisella spp. all have the characteristic of being usually associated with contact with animals. This means that these organisms are typically transmitted to humans through direct or indirect contact with infected animals.

Explanation

Brucella spp., Pasturella spp., and Francisella spp. all have the characteristic of being usually associated with contact with animals. This means that these organisms are typically transmitted to humans through direct or indirect contact with infected animals.

10. An outbreak of food poisoning occurs and dairy products are suspected as being contaminated with microorganisms. A sample of unpasteurized milk is sent to the laboratory and the following is discovered: slow growing, Gram-positive bacilli, which are able to grow in tissue culture cells. Which of the following organisms would you suspect?

E. coil

Corynebacterium

Listeria

Mycobacterium

"able to grow in tissue cultures" means it is an intracellular microbe.
the key with dairy is that it is refrigerated, so the microbe has to be able to grow at low temp.

Listeria can grow at 4 degrees C

Explanation

"able to grow in tissue cultures" means it is an intracellular microbe.
the key with dairy is that it is refrigerated, so the microbe has to be able to grow at low temp.

Listeria can grow at 4 degrees C

11. The virulence factor CagA encoded by a specific pathogen is associated with gastric adenocarcinoma. CagA is encoded within a pathogenicity island and transferred into host cells via a Type IV secretion system. Which of the following pathogens encodes CagA?

Candida albicans

Escherichia coil

Streptococcus lactis

MRSA - methicillin resistant Staphylococcus aureus

Helicobacter pylori

Helicobacter pylori is the correct answer because it is the only pathogen listed that is known to encode the virulence factor CagA. CagA is associated with gastric adenocarcinoma and is encoded within a pathogenicity island in H. pylori. It is transferred into host cells via a Type IV secretion system. Candida albicans, Escherichia coli, Streptococcus lactis, and MRSA (methicillin resistant Staphylococcus aureus) do not encode CagA and are not associated with gastric adenocarcinoma.

Explanation

Helicobacter pylori is the correct answer because it is the only pathogen listed that is known to encode the virulence factor CagA. CagA is associated with gastric adenocarcinoma and is encoded within a pathogenicity island in H. pylori. It is transferred into host cells via a Type IV secretion system. Candida albicans, Escherichia coli, Streptococcus lactis, and MRSA (methicillin resistant Staphylococcus aureus) do not encode CagA and are not associated with gastric adenocarcinoma.

12. A major cause of diarrhea is a bacterium with the following characteristics: Gram- negative, comma-shaped bacillus, motile with polar flagella and unable to ferment or oxidize carbohydrates, but is oxidase-positive. Isolation of this organism is improved by incubation of cultures at 42C. What is this bacterium?

Escherichia coil

Campylobacter jejuni

Vibrio cholera

Helicobacter pylori

remember that Campylobacter is 42C
and Listeria is 4C

Explanation

remember that Campylobacter is 42C
and Listeria is 4C

13. In bacterial cell walls, peptidoglycan (PG) as the major constituent has which of the following properties?

PG is present in Gram-positive bacteria as well as Gram-negative bacteria, including Chiamydia

Fragments of PG are toxic and induce cytokines

PG is comprised of lipid A and 0-polysaccharide

Vancomycin inhibits PG synthesis by binding to transglycosidase and transpeptidase

PG is recognized by immunes system and initiates immune response.

VANCOMYCIN -- is a glycopeptide antibiotic used in the treatment of infections by Gram-positive bacteria.
remember, 3 things, NAM/NAG, D-ala D-ala, & cross-linking

The large hydrophilic molecule is able to form hydrogen bond interactions with the terminal D-alanyl-D-alanine moieties of the NAM/NAG-peptides. Under normal circumstances, this is a five-point interaction. This binding of vancomycin to the D-Ala-D-Ala prevents cell wall synthesis in two ways. It prevents the synthesis of the long polymers of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) that form the backbone strands of the bacterial cell wall, and it prevents the backbone polymers that do manage to form from --CROSS-LINKING--- with each other

Explanation

PG is recognized by immunes system and initiates immune response.

VANCOMYCIN -- is a glycopeptide antibiotic used in the treatment of infections by Gram-positive bacteria.
remember, 3 things, NAM/NAG, D-ala D-ala, & cross-linking

The large hydrophilic molecule is able to form hydrogen bond interactions with the terminal D-alanyl-D-alanine moieties of the NAM/NAG-peptides. Under normal circumstances, this is a five-point interaction. This binding of vancomycin to the D-Ala-D-Ala prevents cell wall synthesis in two ways. It prevents the synthesis of the long polymers of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) that form the backbone strands of the bacterial cell wall, and it prevents the backbone polymers that do manage to form from --CROSS-LINKING--- with each other