sample Questions for Exam 1

The skeletal structure of which type of antibiotic is depicted in the image?

Penicillin

A 30-year-old woman who has been paraplegic for the past two years, has developed a urinary tract infection, followed by gram-negative sepsis, which of the following has contributed most to the pathogenesis of her condition

Lipid A (LPS)

A 15-year-old high school student is diagnosed with chronic acne. The dermatologist prescribed tetracycline to help manage the condition adverse effects of tetracycline include which of the following.

All of the above

Synthesis of which of the following molecules/structures is inhibited by tetracycline?

Proteins

Beta-lactam antibiotics would be ineffective for treatment of pneumonia caused by Mycoplasma pnueumoniae because the bacterium:

Has no cell wall

Many clinical isolates of Streptococcus pnuemoniae- leading cause of community acquired pneumonia and bacterial meningitis in the US - are resistant to penicillin. Which of the following is the most likely mechanism of resistance?

Production of beta-lactamase

The mechanism of action of which of the following bactericidal antibiotics involves competitive inhibition of the transpeptidase enzyme family?

Keflex (cephalosporin)

Shortly after arriving to Central Asia for a humanitarian mission a 24-year-old student has developed bloody diarrhea. Stool culture reveals Shigella organisms, and she is treated with Bactrim. Due to the highly infectious nature of the Shigellae, she is advised to follow proper hygiene and thoroughly wash her hands. Which of the following is true regarding the ID 50 of Shigella?

Low

Vancomycin is effective against gram-positive cocci That have developed resistance to beta-lactam antibiotics. Vancomycin inhibits

Peptidoglycan synthesis by binding to D-alanyl-D-alanine moieties

The Worldwide spread of AIDS is best described as

Pandemic

Scientists recently discovered a novel antibiotic, Teixobactin, that displays excellent activity again Gram positive pathogens. The MIC (minimum inhibitory concentration) of it against S. aureus is 0.125 mg/ml. The maximum safely achievable level of the antibiotic in the body fluids is >125 mg/ml. Thus, Teixobactin has

A High therapeutic index

A six-year-old boy is diagnosed with pneumonia caused by Mycoplasma pneumoniae. His pediatrician prescribes erythromycin, which inhibits:

Protein synthesis

A 34-year-old with AIDS has developed disseminated histoplasmosis, a systemic fungal disease for which she receives intravenous amphotericin B what is the mechanism of action of amphotericin B?

Disruption of the cytoplasmic membrane

Barry Marshal and J. Robin Warren discovered Helicobacter pylori and elucidated its role in pathogenesis of gastritis and peptic ulcer disease con order to prove their hypothesis, Barry Marshall self-induced historically confirmed gastritis by drinking large smoking of H. pylori organisms isolated from another patient suffering from gastritis. Which of the following was satisfied by this experiment?

Koch’s postulate 3

Meningitis causing bacteria, such as Haemophilus influenzae, Streptococcus pnuemoniae and Neisseria meningitidis, have an important structure that helps them to evade phagocytosis by components of the host immune system. What is the structure?

Polysaccharide capsule

A 70 year-old patient who is recovering post surgery and received clindamycin has developed diarrhea. Which of the following should be suspected

Pseudomembranous colitis caused by C. difficile

The distal gut microbiota is dominated (>90%) by which two bacterial phyla?

Firmicutes and Bacteroidetes

Members of normal gastrointestinal, microbiota are beneficial in many ways, Including production of vitamin K that plays a role in the clotting cascade. Which of the following G.I. organisms is known to produce vitamin K?

Escherichia coli

A 70-year-old is diagnosed with chronic prostates and a urinary tract infection caused by E. coli. The physician prescribes Ciprofloxacin (2nd gen. Fluoroquinolone). The mechanism of action of ciprofloxacin involves inhibition of which of the following?

DNA gyrase

During which stage of infection disease do patients first display any clinical sign and/or symptom of an infection

Prodromal

A 15-year-old girl with a recent history of tick bites was admitted to the hospital with fever, headache, muscle and joint pains and low blood cell counts. PCR confirmed the diagnosis of ehrlichiosis. In spite of appropriate management, she died on hospital day 2. Ehrlichiosis is an example Of which of the following?

Vector-borne disease

A 23-year-old pregnant woman presents at her local clinic complaining of mild flu like symptoms. Patient history revealed she had consumed raw dairy products at her grandparents farm several days earlier leading the physician to suspect the patient had listeriosis. A major complication of infection with listeria monocytogenes is the potential of the pathogen to be passed directly from the mother to the developing fetus. This is an example of ____ transmission.

Vertical

The investigation of typhoid fever cases in Kolkata, India, that had occurred between 1991 through 2001 lead to the discovery of multidrug resistant (MDR) strains of Salmonella Typhi, the cause of typhoid fever. Laboratory Conjugation experiments resulted in isolation of plasma, DNA conferring resistance to ampicillin, chloramphenicol, cotrimoxazole and tetracycline. The antibiotic-sensitive S. Typhi isolates did not contain the MDR-plasmid. The study concluded that antibiotic-resistant S. Typhi strains most likely acquired the MDR-plasmid from other enteric bacteria by a mechanism that involves:

Sex pili

colonization

The ability of a microbe to adhere to a body surface and replicate without causing disease (MRSA is common ex.)

Latent infection

Infection that persists after initial colonization; organisms are present, but disease is not (like tuberculosis)

Nosocomial infections

Infections acquired while in a health care associated facility. (Aka HAIs)

Exogenous (nosocomial)

Pathogen acquired within health care environment (bedding, clothing, staff, other patients)

Iatrogenic (nosocomial)

Consequence of direct medical intervention

• administration of drugs (ex. Antibiotic-associated diarrhea)

• Insertion of contaminated medical devices

Median Infectious Dose (ID 50)

number of microorganisms required to cause an infection in half the members of a tested population

Median lethal dose (LD 50)

The number of microorganisms required to kill half the members of a tested population

The infectious dose is ____ than the lethal dose

ALWAYS equal to/lower

Indirect transmission

Microbes can be transmitted indirectly by inanimate objects (fomites), by vehicle transmission or by a biological vector

Vehicle transmission (indirect)

Microbes transmitted indirectly through fomites, food, water, etc

Direct transmission

By direct contact or aerosols

Vector transmission

Transmitted both directly and indirectly from animal reservoirs

Accidental (vector)

Ex. West Nile virus through insect or animal

Vertical transmission

From mother to baby either during development or shortly after birth

Zoonoses from animal reservoirs

Disease that are naturally spread from their primary animal host to humans

Ex. Bubonic plague humans are accidental hosts

Endotoxin

LPS ONLY IN GRAM NEGATIVE BACTERIA

Sporadic disease

One where only a few scattered cases occur within a given area or population

(Diphtheria)

Endemic

Occurs at relatively stable frequency within a given population or area

(Human plague)

Epidemic

Occurs when a disease exceeds its normal frequency

(Flu) big fluctuations

Pandemic

Epidemic outbreak spreads across continental barriers

(ZIKA virus)