Pathogens in GIT infections Flashcards
AJ, a 7 year old healthy boy, was brought to the OPD due to bloody stools. The condition
started 3 days ago when he developed watery stools occurring 5-6 times/day. This was
associated with abdominal pain and low grade fever. A few hours prior to consult, there was note
of passage of bloody stools. Work-up of his stool revealed a gram-negative rod with fermentation
of lactose and glucose. What is the most probable organism?
A. Helicobacter pylori
B. Shigella
C. E. coli
D. Salmonella
C
A 30 year old tourist returned from a trip to the Philippines and abruptly began having cramps
and diarrhea. There was frequent watery bowel movements that contained particles of grayish
white stool. The man was sweaty and nauseated. Upon admission to the hospital, 2 L of fluid was
administered IV, which was supplemented by oral fluid. The patient was discharged 48 hours
after admission. Clinically, the patient was diagnosed to have cholera. Which of the following is
TRUE for the organism?
A. Skirrow’s agar improves the isolation of the organism
B. It is a gram (-) oxidase positive rod.
C. It survives well in acidic environment
D. The most important biotypes are Ogawa and Inaba
B
Toxins play an important role in the pathogenesis of bacterial gastroenteritis. Which of the
following is CORRECT?
A. The cholera toxin is similar to the heat stable toxin of ETC in terms of the stimulation of cAMP
B. All Shigella dysenteraie produce a potent enterotoxin called shiga toxin
C. The EPEC exotoxin is a verotoxin that produces copious, bloody diarrhea
D. The Salmonella enterotoxin bears a limited relatedness to cholera toxin both structurally and
antigenically
A
Some bacterial pathogens of the digestive tract need specific oxygen requirements for their
growth. Which of the following organisms is microaerophilic?
A. Salmonella typhi
B. Helicobacter pylori
C. Bacillus cereus
D. Shigella flexneri
B
The TSI contains various reagents to demonstrate fermentation of specific sugars and
subsequent decarboxylation of proteins. What are the sugar components of this test?
A. Glucose, lactose, mannitol
B. Glucose, lactose, sucrose
C. Glucose, citrate, mannose
D. Glucose, indole, iron
B
What is the group of organisms associated with fecal contamination of water? A. Coliforms B. Bacteroides C. Enteric pathogens D. Bacillus group
A
Rotavirus belongs to the family Reoviridae. Members of this group usually develop respiratory
symptoms. What is the typical clinical syndrome associated with rotavirus infection?
A. Systemic viral infection of young adults
B. Bloody diarrhea and bronchiolitis of infants
C. Crampy abdominal pain, watery diarrhea and colds in infants
D. Nausea, vomiting, and diarrhea in young children
C
Which of the following is TRUE about rotavirus infection?
A. The different strains are designated by the G and P serotypes
B. Diagnosis is routinely made by electron microscopy of suitably treated stool samples
C. The uncoating of the first layer or capsid leads to the infectious particle
D. Rotavirus causes infection exclusively in man
A
Some evidence suggests that a Rotavirus protein may behave as an enterotoxin in a manner
similar to the heat-labile toxin of E. coli. What is this protein?
A. Protease sensitive VP4
B. NSP6
C. Glycoprotein VP7
D. NSP4
D
Which of the following associations is CORRECT? A. Rotavirus: single stranded RNA B. Norovirus: single stranded RNA C. E. coli: gram (+) bacilli D. Helicobacter pylori: gram (-) cocci
B
Enterobacteriaceae have a complex antigenic structure. Which of the following is the
CORRECT relationship between antigen and cell structure?
A. Flagella: F antigen
B. Cell wall: K antigen
C. LPS: O antigen
D. Capsule: H antigen
C
The different antigens of enteric pathogens are used for identification of the strain. What
antibody agglutinates the somatic or O antigen?
A. IgG
B. IgM
C. IgE
D. IgD
B
E coli indicates fecal contamination. It is the most abundant bacteria found in the gut. Which
of the following describes this bacterial gut infection?
A. The EHEC infection is commonly seen in resource-limited countries
B. Patients with E coli gut infection usually present with watery, bloody diarrhea
C. It contains a specific O antigen that differentiates it from other members of the
Enterobacteriaceae
D. There is no reliable specific test to identify pathogenic from non-pathogenic E. coli
D
Shigella closely resembles E. coli. Which of the following characteristics differentiates
Shigella?
A. The organism is non-motile and lacks the H antigen
B. The O antigen defines the different species
C. The organism is a glucose fermenter
D. The presence of toxins contribute to their virulence
A
S. enterica gastroenteritis is predominantly a disease of industrialized societies and improper
food handling which allows the transmission from the animal reservoir to humans. What is the
species that infects strictly humans?
A. Salmonella enteritidis
B. Salmonella typhi
C. Salmonella typhimurium
D. Salmonella cholerasuis
B
