Question 1

Which component of the Gram-negative bacterial cell wall is primarily responsible for triggering fever, vasodilation, inflammation, and disseminated intravascular coagulation (DIC) in humans?

Accepted Answer

Lipid A (endotoxin)

Question 2

A patient presents with a painful, pus-filled discharge and reports painful urination. Gram-negative diplococci are observed in a sample from the inflamed area. Which organism is most likely responsible for this infection?

Accepted Answer

Neisseria gonorrhoeae

Question 3

Which of the following is a distinguishing feature of Neisseria species compared to other Gram-negative pathogens?

Accepted Answer

They are oxidase positive

Question 4

A newborn develops an eye infection shortly after birth. Which preventative measure is most effective in reducing the risk of this infection?

Accepted Answer

Application of antimicrobial agents to the eyes

Question 5

Which of the following best explains why Neisseria gonorrhoeae can evade the human immune system?

Accepted Answer

It secretes a protease that cleaves secretory IgA

Question 6

A college student living in a dormitory develops sudden fever, headache, and a petechial rash. Gram-negative diplococci are found in cerebrospinal fluid. Which pathogen is most likely responsible?

Accepted Answer

Neisseria meningitidis

Question 7

Which test is commonly used to distinguish between Enterobacteriaceae and Pasteurellaceae families?

Accepted Answer

Oxidase test

Question 8

Which of the following is a characteristic of coliforms within the Enterobacteriaceae family?

Accepted Answer

They rapidly ferment lactose

Question 9

A patient develops hemolytic uremic syndrome after eating undercooked ground beef. Which strain of Escherichia coli is most likely responsible?

Accepted Answer

E. coli O157:H7

Question 10

Which virulence factor is shared by Salmonella, Shigella, and Yersinia and is responsible for injecting proteins into host cells to inhibit phagocytosis?

Accepted Answer

Type III secretion system

Question 11

A patient presents with severe dysentery. Laboratory tests identify a nonmotile, oxidase-negative Gram-negative bacillus. Which organism is most likely responsible?

Accepted Answer

Shigella dysenteriae

Question 12

Which toxin produced by Shigella dysenteriae is responsible for stopping protein synthesis in host cells, leading to more severe disease?

Accepted Answer

Shiga toxin

Question 13

A patient develops bubonic plague after being bitten by a flea from a wild rodent. Which species is responsible for this disease?

Accepted Answer

Yersinia pestis

Question 14

Which of the following is a common source of human Salmonella infection?

Accepted Answer

Consumption of poultry and eggs

Question 15

Which Gram-negative bacillus is known for producing a red pigment when grown at room temperature and can cause life-threatening infections in immunocompromised patients?

Accepted Answer

Serratia marcescens

Question 16

A patient with cystic fibrosis develops a chronic lung infection with a Gram-negative bacillus that forms biofilms and is highly resistant to antibiotics. Which organism is most likely responsible?

Accepted Answer

Pseudomonas aeruginosa

Question 17

Which Gram-negative coccobacillus is an intracellular parasite, highly infectious, and causes tularemia, a zoonotic disease often misdiagnosed due to its similarity to other illnesses?

Accepted Answer

Francisella tularensis

Question 18

A patient develops pneumonia after inhaling aerosols from a contaminated water source. Which organism is most likely responsible for Legionnaires’ disease?

Accepted Answer

Legionella pneumophila

Question 19

Which Gram-negative bacillus is an obligate intracellular parasite, causes Q fever, and is mainly transmitted by inhalation of infective bodies from farm animals?

Accepted Answer

Coxiella burnetii

Question 20

Which anaerobic Gram-negative bacillus is a dominant member of the intestinal microbiota and is most commonly associated with abdominal infections treatable by metronidazole?

Accepted Answer

Bacteroides fragilis

Pathogenic Gram-Negative Cocci and Bacilli: Structure, Physiology, and Clinical Significance

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