Chapter 9: Bacteriology
1. A 22-year-old woman who works in a plant nursery presents with a history of fever and
cough for 2 months. Over this period of time she has lost 5 kg. Chest radiography shows
bilateral upper lobe infiltrates with cavities. A stain of her sputum shows acid-fast bacilli. The
likely means by which the patient acquired
her infection is
(A) Sexual activity
(B) Ingesting the microorganisms in her food
(C) Holding onto contaminated hand rails when she takes public transportation
(D) Handling potting soil
(E) Breathing aerosolized droplets containing the microorganism
The woman seems to show signs of Tuberculosis, which include signs of lung disease
lasting more than 2 weeks, Loss of weight and a positive x-ray result. Tuberculosis is caused by
different strains of Mycobacterium, an acid fast bacilli. Since Tb can only be transmitted
through aerosol droplets containing the organism, the answer can only be choice E.
2. During a pandemic of a well-characterized disease, a group of 175 airline passengers flew
from Lima, Peru, to Los Angeles. Lunch on the plane included crab salad, which was eaten by
about two-thirds of the passengers. After landing in Los Angeles, many of the passengers
transferred to other flights with destinations in other parts of California and other Western
states. Two of the passengers who stayed in Los Angeles developed severe watery diarrhea. The
status of the other passengers was unknown. The likely cause of the diarrhea in the two
passengers is
(A) Escherichia coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7)
(B) Vibrio cholerae type O139 (lipopolysaccharide O antigen 139)
(C) Shigella dysenteriae type 1
(D) Campylobacter jejuni
(E) Entamoeba histolytica
The likely cause of diarrhea of the two passengers is Vibrio cholera type 0139. This vibrio
causes classic cholera which yields to sudden onset of vomiting and nausea and profuse watery
diarrhea. The most important sign is that the passengers experienced the signs after a day
which coincides with the bacteria’s incubation period of 12 hours to 3 days. The situation also
happened during a pandemic and only cholera is known to cause pandemics among them.
3. A 65-year-old woman has a long-term central venous catheter for intravenous therapy. She
develops fever and subsequently has multiple blood cultures positive for Staphylococcus
epidermidis. All of the S epidermidis isolates have the same colony
morphology and antimicrobial susceptibility pattern, suggesting that they are the same strain.
A S epidermidis biofilm is thought to be present on the catheter. Which one of the following
statements about such an infection is correct?
(A) The biofilm containing the S epidermidis is likely to wash off the catheter.
(B) Production of an extracellular polysaccharide inhibits growth of the S epidermidis, limiting
, antimicrobial therapy, and it is likely the catheter will have to be removed to cure the
infection.
The correct answer is letter E, as a matter of fact organisms in the biofilm are more
resistant than those that are free living. Letter A is incorrect as these organisms have strong
attachment to the surface while choices C and D are incorrect because the quorum sensing
ability of S. epidermidis is supposed to increase the metabolic activity of the bacteria
4. The first microorganism to satisfy Koch’s postulates (in the late 19th century) was
(A) Treponema pallidum
(B) Stenotrophomonas maltophilia
(C) Mycobacterium leprae
(D) Bacillus anthracis
(E) Neisseria gonorrhoeae
The first microorganism to satisfy Koch’s postulates was Bacillus anthracis it was in
1876.
5. Which of the following statements about lipopolysaccharide is correct?
(A) It interacts with macrophages and monocytes yielding release of cytokines.
(B) The toxic component is the O side chain.
(C) It forms holes in red blood cell membranes yielding hemolysis.
(D) It causes hypothermia.
(E) It causes paralysis.
Lipopolysaccharides general function is to contribute to the structural integrity of the
bacteria, and protecting the membrane from certain kinds of chemical attack, which best fits Choice
A. The other choices are incorrect as the toxic component of LPS is Lipid A, Hemolysin destroys
RBC cell membrane leading to cell lysis and LPS simply does not cause hypothermia nor paralysis
6. A 27-year-old man had a rhinoplasty. A nasal tampon was placed to control the bleeding.
Approximately 8 hours later, he developed headache, muscle aches, and abdominal cramps
with diarrhea. He then developed an erythematous rash (resembling sunburn) over much of his
body, including the palms and soles. His blood pressure is 80/50 mm Hg. The nasal tampon
remained in place. His liver enzyme tests were elevated, and there was evidence of moderate
renal failure. This patient’s illness was likely to be caused by which of the following?
(A) Lipopolysaccharide
(B) Peptidoglycan
(C) A toxin that is a superantigen
(D) A toxin that has A and B subunits
(E) Lecithinase (alpha toxin)
The cause of the patient's illness was a Superantigen toxin. Since it is associated
with tampon and the patient developed different characteristics of Toxic Shock
1. A 22-year-old woman who works in a plant nursery presents with a history of fever and
cough for 2 months. Over this period of time she has lost 5 kg. Chest radiography shows
bilateral upper lobe infiltrates with cavities. A stain of her sputum shows acid-fast bacilli. The
likely means by which the patient acquired
her infection is
(A) Sexual activity
(B) Ingesting the microorganisms in her food
(C) Holding onto contaminated hand rails when she takes public transportation
(D) Handling potting soil
(E) Breathing aerosolized droplets containing the microorganism
The woman seems to show signs of Tuberculosis, which include signs of lung disease
lasting more than 2 weeks, Loss of weight and a positive x-ray result. Tuberculosis is caused by
different strains of Mycobacterium, an acid fast bacilli. Since Tb can only be transmitted
through aerosol droplets containing the organism, the answer can only be choice E.
2. During a pandemic of a well-characterized disease, a group of 175 airline passengers flew
from Lima, Peru, to Los Angeles. Lunch on the plane included crab salad, which was eaten by
about two-thirds of the passengers. After landing in Los Angeles, many of the passengers
transferred to other flights with destinations in other parts of California and other Western
states. Two of the passengers who stayed in Los Angeles developed severe watery diarrhea. The
status of the other passengers was unknown. The likely cause of the diarrhea in the two
passengers is
(A) Escherichia coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7)
(B) Vibrio cholerae type O139 (lipopolysaccharide O antigen 139)
(C) Shigella dysenteriae type 1
(D) Campylobacter jejuni
(E) Entamoeba histolytica
The likely cause of diarrhea of the two passengers is Vibrio cholera type 0139. This vibrio
causes classic cholera which yields to sudden onset of vomiting and nausea and profuse watery
diarrhea. The most important sign is that the passengers experienced the signs after a day
which coincides with the bacteria’s incubation period of 12 hours to 3 days. The situation also
happened during a pandemic and only cholera is known to cause pandemics among them.
3. A 65-year-old woman has a long-term central venous catheter for intravenous therapy. She
develops fever and subsequently has multiple blood cultures positive for Staphylococcus
epidermidis. All of the S epidermidis isolates have the same colony
morphology and antimicrobial susceptibility pattern, suggesting that they are the same strain.
A S epidermidis biofilm is thought to be present on the catheter. Which one of the following
statements about such an infection is correct?
(A) The biofilm containing the S epidermidis is likely to wash off the catheter.
(B) Production of an extracellular polysaccharide inhibits growth of the S epidermidis, limiting
, antimicrobial therapy, and it is likely the catheter will have to be removed to cure the
infection.
The correct answer is letter E, as a matter of fact organisms in the biofilm are more
resistant than those that are free living. Letter A is incorrect as these organisms have strong
attachment to the surface while choices C and D are incorrect because the quorum sensing
ability of S. epidermidis is supposed to increase the metabolic activity of the bacteria
4. The first microorganism to satisfy Koch’s postulates (in the late 19th century) was
(A) Treponema pallidum
(B) Stenotrophomonas maltophilia
(C) Mycobacterium leprae
(D) Bacillus anthracis
(E) Neisseria gonorrhoeae
The first microorganism to satisfy Koch’s postulates was Bacillus anthracis it was in
1876.
5. Which of the following statements about lipopolysaccharide is correct?
(A) It interacts with macrophages and monocytes yielding release of cytokines.
(B) The toxic component is the O side chain.
(C) It forms holes in red blood cell membranes yielding hemolysis.
(D) It causes hypothermia.
(E) It causes paralysis.
Lipopolysaccharides general function is to contribute to the structural integrity of the
bacteria, and protecting the membrane from certain kinds of chemical attack, which best fits Choice
A. The other choices are incorrect as the toxic component of LPS is Lipid A, Hemolysin destroys
RBC cell membrane leading to cell lysis and LPS simply does not cause hypothermia nor paralysis
6. A 27-year-old man had a rhinoplasty. A nasal tampon was placed to control the bleeding.
Approximately 8 hours later, he developed headache, muscle aches, and abdominal cramps
with diarrhea. He then developed an erythematous rash (resembling sunburn) over much of his
body, including the palms and soles. His blood pressure is 80/50 mm Hg. The nasal tampon
remained in place. His liver enzyme tests were elevated, and there was evidence of moderate
renal failure. This patient’s illness was likely to be caused by which of the following?
(A) Lipopolysaccharide
(B) Peptidoglycan
(C) A toxin that is a superantigen
(D) A toxin that has A and B subunits
(E) Lecithinase (alpha toxin)
The cause of the patient's illness was a Superantigen toxin. Since it is associated
with tampon and the patient developed different characteristics of Toxic Shock
