Bacteriology Practice Questions

Each of the following statements concerning the surface structures of bacteria is correct EXCEPT:

A) Pili mediate the interaction of bacteria with mucosal epithelium.

B) Polysaccharide capsules retard phagocytosis.

C) Both gram-negative rods and cocci have lipopolysaccharide (“endotoxin”) in their cell wall.

D) Bacterial flagella are nonantigenic in humans because they closely resemble human flagella in chemical composition.

D) Bacterial flagella are nonantigenic in humans because they closely resemble human flagella in chemical composition.

Each of the following statements concerning bacterial spores in correct EXCEPT:

A) Their survival ability is based on their enhanced metabolic activity.
B) They are formed by gram-positive rods.
C) They can be killed by being heated to 121ºC for 15 minutes.
D) They are formed primarily when nutrients are limited.

A) Their survival ability is based on their enhanced metabolic activity.

Each of the following statements concerning bacterial spores is correct EXCEPT:
A) Spores are formed under adverse environmental conditions such as the absence of a carbon source.
B) Spores are resistant to boiling.
C) Spores are metabolically inactive and contain dipicolinic acid, a calcium chelator.
D) Spores are formed primarily by organisms of the genus Neisseria

D) Spores are formed primarily by organisms of the genus Neisseria

An extra-chromosomal element associated with bacterial conjugation is called:

A) an A factor

B) an F factor

C). an R factor

D) a D factor

Name the process by which the following occur:

Transfer of DNA from a dead bacterium to a live one.

Transformation or Generalized Transduction

Name the process by which the following occur:

Transfer of DNA from a bacterium to another by a lysogenic phage.

Specialized transduction

Name the process by which the following occur:

An increase in production of virulence factors once a critical number of bacteria is reached.

Quorum sensing

Name the process by which the following occur:

Protection of DNA from digestion by restriction endonucleases.

Restriction/Modification

Operons have the following properties (select all that are true).

A) They allow the syntheses of a coordinated set of enzymes from a single mRNA

B) They have enhancers that can be thousands of nucleotides upstream of the start site

C) Operators typically bind proteins called repressors that block RNA polymerase action

D) In the case of the lac Operon, the presence of the sugar lactose represses the operon

A) They allow the syntheses of a coordinated set of enzymes from a single mRNA

C) Operators typically bind proteins called repressors that block RNA polymerase action

Two species of bacteria are designated as A and B. A is susceptible to Ampicillin (i.e. killed by) while B is resistant to Ampicillin. If the strains are mixed and cultured in the presence of Ampicillin, some sub-strains of A are recovered which are now resistant to the antibiotic. However, if the strains are cultured in the same medium under the same conditions but separated by a barrier (filter) with 0.1 micron -diameter pores, no resistant sub-strains of A are recovered. By what mechanism is the drug resistance transferred?

A) Restriction/Modification

B) Quorum Sensing

C) Conjugation

D) Transformation

C) Conjugation

True or False: A chemical compound that scores positive in an Ames test is therefore a carcinogen.

False

State a few major differences between an F factor and a lytic phage.

• The lytic phage kills the bacteria, while the F factor depends on the donor being alive.

• The F factor is simply DNA while the phage is a complex particle.

Give the correct genus and/or species name for the following bacteria:

• Gram-positive coccus, catalase-positive, coagulase-positive

Staphylococcus aureus

Give the correct genus and/or species name for the following bacteria:

• Gram-negative diplococcus, has pili

Neisseria

Give the correct genus and/or species name for the following bacteria:

• Gram-negative diplococcus, has capsule, ferments maltose

Neisseria meningitidis

Give the correct genus and/or species name for the following bacteria:

• Gram-positive coccus, grows in chains

Streptococcus

Give the correct genus and/or species name for the following bacteria:

• Gram-positive diplococcus, isolated from a patient with a cough

Streptococcus pneumoniae

Give the correct genus and/or species name for the following bacteria:

• coccus, catalase-negative, alpha-hemolytic, resistant to optochin

Streptococcus sanguis or S. mutans (viridians group)

Give the correct genus and/or species name for the following bacteria:

• coccus, catalase-negative, beta-hemolytic, isolated from a neonate at autopsy

Streptococcus agalactiae

Which of the following causes paralysis by blocking release of acetylcholine:

A) Diphtheria toxin

B) Tetanus toxin

C) Botulinum toxin

D) Toxic shock syndrome toxin

E) Cholera toxin

C) Botulinum toxin

Which of the following inhibits protein synthesis by blocking elongation factor 2:

A) Diphtheria toxin

B) Tetanus toxin

C) Botulinum toxin

D) Toxic shock syndrome toxin

E) Cholera toxin

A) Diphtheria toxin

Which of the following stimulates T cells to produce cytokines:

A) Diphtheria toxin

B) Tetanus toxin

C) Botulinum toxin

D) Toxic shock syndrome toxin

E) Cholera toxin

D) Toxic shock syndrome toxin

Which of the following stimulates the production of cyclic AMP by adding ADP-ribose to a G protein:

A) Diphtheria toxin

B) Tetanus toxin

C) Botulinum toxin

D) Toxic shock syndrome toxin

E) Cholera toxin

E) Cholera toxin

Which of the following inhibits the release of inhibitory neurotransmitters causing muscle spasms.:

A) Diphtheria toxin

B) Tetanus toxin

C) Botulinum toxin

D) Toxic shock syndrome toxin

E) Cholera toxin

B) Tetanus toxin

Each of the following agents is a recognized cause of diarrhea EXCEPT:

A) Clostridium perfringens

B) Enterococcus faecalis

C) Escherichia coli

D) Vibrio cholerae

B) Enterococcus faecalis

Your patient is a 30-year-old woman with nonbloody diarrhea for the past 14 hours. Which one of the following organisms is LEAST likely to cause this illness?

A) Clostridium difficile

B) Streptococcus pyogenes

C) Shigella dysenteriae

D) Salmonella enteritidis

B) Streptococcus pyogenes

Which one of the following bacteria has the LOWEST 50% infectious dose (ID50)?

A) Shigella sonnei

B) Vibrio cholerae

C) Salmonella typhi

D) Campylobacter jejuni

A) Shigella sonnei

For which one of the following enteric illnesses is a chronic carrier state MOST likely to develop?

A) Campylobacter enterocolitis

B) Shigella enterocolitis

C) Cholera

D) Typhoid fever

D) Typhoid fever

The pathogenesis of which one of the following organisms is MOST likely to involve invasion of the intestinal mucosa?

A) Vibrio cholerae

B) Shigella sonnei

C) Enterotoxigenic Escherichia coli

D) Clostridium botulinum

B) Shigella sonnei

Which one of the following gastrointestinal infections is the MOST likely to progress to bacteremia?

A) Shigella flexneri

B) Campylobacter jejuni

C) Vibrio cholerae

D) Salmonella typhi

D) Salmonella typhi

Which 3 common virulence factor activities are most important to the pathogenesis of Vibrio cholerae?

A) Survival in stomach acid

B) GI attachment pilus

C) Exotoxin expression

D) Enterotoxin expression

E) IgA protease

F) Capsule

G) Serum resistance

B) GI attachment pilus

C) Exotoxin expression

D) Enterotoxin expression

Each of the following is a typical property of obligate anaerobes EXCEPT:

A) They generate energy by using the cytochrome system.

B) They grow best in the absence of air.

C) They lack superoxide dismutase.

D) They lack catalase.

A) They generate energy by using the cytochrome system.

Each of the following statements concerning Clostridium tetani is correct EXCEPT:

A) It is a gram-positive, spore-forming rod.

B) Pathogenesis is due to the production of an exotoxin that blocks inhibitory neurotransmitters.

C) It is a facultative organism; it will grow on a blood agar plate in the presence of room air.

D) Its natural habitat is primarily the soil.

C) It is a facultative organism; it will grow on a blood agar plate in the presence of room air.

There are documented cases of C. difficile infections being passed between two hospital patients who were both examined by the same colonoscope. How could this happen?

C. difficile forms spores, and colonoscopes can’t be autoclaved.

What traits are shared by all the Enterobacteriaceae?

A) Gram(-) rods

B) Not strictly anaerobic

C) Problematic antibiotic resistances

D) All of the above

D) All of the above

Which enteric bacterial infection may lead to hemolytic-uremic syndrome (HUS)?

A) Shigella

B) Salmonella

C) Yersinia

D) Proteus

A) Shigella

Each of the following statements concerning Mycobacterium tuberculosis is correct EXCEPT:

A) After being stained with carbolfuchsin, M. tuberculosis resists decolorization with acid-alcohol.

B) M. tuberculosis has a large amount of mycolic acid in the cell wall.

C) M. tuberculosis appears as a red rod in Gram-stained specimens.

D) M. tuberculosis appears as a red rod in acid-fast stained specimens.

C) M. tuberculosis appears as a red rod in Gram-stained specimens.

Each of the following statements concerning Mycobacterium tuberculosis is correct EXCEPT:

A) Some strains of M. tuberculosis isolated from patients exhibit multiple drug resistance (i.e., they are resistant to both isoniazid and rifampin).

B) M. tuberculosis contains a small amount of lipid in its cell wall and therefore stains poorly with the Gram stain.

C) M. tuberculosis grows slowly, often requiring 3 to 6 weeks before colonies appear.

D) The antigen in the tuberculin skin test is a protein extracted from the organism.

B) M. tuberculosis contains a small amount of lipid in its cell wall and therefore stains poorly with the Gram stain.

Which of the following factors present challenges in diagnosing TB?

A) Many different possible sets of symptoms affecting different organs

B) Lack of a definitive single lab test like urine antigen ELISA

C) Inability to culture in vitro

D) A and B not C

E) A, B, and C

A) Many different possible sets of symptoms affecting different organs

Each of the following statements concerning peptidoglycan is correct EXCEPT:

A) It has a backbone composed of alternating units of muramic acid and acetylglucosamine.

B) Cross-links between the tetrapeptides involve D-alanine.

C) It is thinner in gram-positive than in gram-negative cells.

D) It can be degraded by lysozyme.

C) It is thinner in gram-positive than in gram-negative cells.

Which of the following statements is the MOST accurate comparison of human, bacterial, and fungal cells?

A) Human cells undergo mitosis, whereas neither bacteria nor fungi do.

B) Human and fungal cells have a similar cell wall, in contrast to bacteria, whose cell wall

contains peptidoglycan.

C) Human and bacterial cells have plasmids, whereas fungal cells do not.

D) Human and fungal cells have similar ribosomes, whereas bacterial ribosomes are significantly different.

D) Human and fungal cells have similar ribosomes, whereas bacterial ribosomes are significantly different.

Each of the following statements concerning the Gram stain is correct EXCEPT:

A) Escherichia coli stains pink because it has a thin peptidoglycan layer.

B) Streptococcus pyogenes stains blue because it has a thick peptidoglycan layer.

C) Mycobacterium tuberculosis stains blue because it has a thick lipid layer.

D) Mycoplasma pneumoniae is not visible in the Gram stain because it does not have a cell wall.

C) Mycobacterium tuberculosis stains blue because it has a thick lipid layer.

Each of the following statements concerning bacterial and human cells is correct EXCEPT:

A) Bacteria are prokaryotic (ie., they have one molecule of DNA, are haploid, and have no nuclear membrane), whereas human cells are eukaryotic (ie., they have multiple chromosomes, and diploid, and have a nuclear membrane).

B) Bacteria derive their energy by oxidative phosphorylation within mitochondria in a manner similar to human cells.

C) Bacterial and human ribosomes are of different sizes and chemical compositions.

D) Bacterial cells possess peptidoglycan, whereas human cells do not.

B) Bacteria derive their energy by oxidative phosphorylation within mitochondria in a manner similar to human cells.