Bacteria Practice Questions

Question 1

A 42-year-old woman comes to her primary care physician with 2 days of fever and malaise. She also says that she has a painful red lesion on her left hand that she noticed after shucking oysters at a recent family reunion. Physical exam reveals a well-demarcated swollen, tender, warm, red lesion on her left hand. Pressing the lesion causes a small amount of purulent drainage. The material is cultured and the causative organism is identified. Which of the following characteristics describes the organism that is most associated with this patient's mechanism of infection?

Accepted Answer

Gram-negative facultative anaerobe

Answer

Gram-negative aerobe

Answer

Gram-positive clusters

Answer

Gram-positive chains

Answer

Gram-negative anaerobe

Question 2

A 42-year-old woman with a history of multiple sclerosis and recurrent urinary tract infections comes to the emergency department because of flank pain and fever. Her temperature is 38.8°C (101.8°F). Examination shows left-sided costovertebral angle tenderness. She is admitted to the hospital and started on intravenous vancomycin. Three days later, her symptoms have not improved. Urine culture shows growth of Enterococcus faecalis. Which of the following best describes the most likely mechanism of antibiotic resistance in this patient?

Accepted Answer

Alteration of peptidoglycan synthesis

Answer

Increased efflux across bacterial cell membranes

Answer

Production of beta-lactamase

Answer

Alteration of penicillin-binding proteins

Answer

Alteration of ribosomal targets

Question 3

An investigator is studying the chemical structure of antibiotics and its effect on bacterial growth. He has synthesized a simple beta-lactam antibiotic and has added a bulky side chain to the molecule that inhibits the access of bacterial enzymes to the beta-lactam ring. The synthesized drug will most likely be appropriate for the treatment of which of the following conditions?

Accepted Answer

Folliculitis

Answer

Nocardiosis

Answer

Atypical pneumonia

Answer

Erythema migrans

Answer

Otitis media

Question 4

A 59-year-old man presents to the emergency room for a fever that has persisted for over 4 days. In addition, he has been experiencing weakness and malaise. His past medical history is significant for a bicuspid aortic valve that was replaced 2 years ago. Physical exam reveals nailbed splinter hemorrhages, tender nodules on his fingers, and retinal hemorrhages. An echocardiogram shows aortic valve vegetations and culture reveals a gram-positive alpha-hemolytic organism that grows as cocci in chains. The organism is then exposed to optochin and found to be resistant. Finally, they are seen to ferment sorbitol. The most likely cause of this patient's symptoms is associated with which of the following?

Accepted Answer

Dental procedures

Answer

Pneumonia

Answer

Colon cancer

Answer

IV drug use

Answer

Sexual activity

Question 5

A 71-year-old woman presents with high-grade fever and chills, difficulty breathing, and a productive cough with rust-colored sputum. She complains of a sharp left-sided chest pain. Physical examination reveals increased fremitus, dullness to percussion, and bronchial breath sounds on the lower left side. A chest X-ray shows left lower lobe consolidation. The offending organism that was cultured from the sputum was catalase-negative and had a positive Quellung reaction. The organism will show which gram stain results?

Accepted Answer

Gram-positive diplococci

Answer

Gram-negative diplococci

Answer

Cannot be seen with gram staining since the organism lacks a cell wall

Answer

Gram-positive cocci in clusters

Answer

Gram-negative rod

Question 6

A 35-year-old female presents to the emergency room complaining of diarrhea and dehydration. She has been experiencing severe watery diarrhea for the past 3 days. She reports that she has been unable to leave the bathroom for more than a few minutes at a time. The diarrhea is profuse and watery without visible blood or mucus. She recently returned from a volunteer trip to Yemen where she worked at an orphanage. Her past medical history is notable for psoriasis for which she takes sulfasalazine. The patient drinks socially and does not smoke. Her temperature is 99°F (37.2°C), blood pressure is 100/55 mmHg, pulse is 130/min, and respirations are 20/min. Mucous membranes are dry. Her eyes appear sunken. Capillary refill is 4 seconds. The patient is started on intravenous fluid resuscitation. Which of the following processes is capable of transmitting the genetic material for the toxin responsible for this patient's condition?

Accepted Answer

Transduction

Answer

Transposition

Answer

Conjugation

Answer

Endospore formation

Answer

Transformation

Question 7

A 62-year-old man is brought to the emergency department from a senior-care facility after he was found with a decreased level of consciousness and fever. His personal history is relevant for colorectal cancer that was managed with surgical excision of the tumor. Upon admission, he is found to have a blood pressure of 130/80 mm Hg, a pulse of 102/min, a respiratory rate of 20/min, and a body temperature 38.8°C (101.8°F). There is no rash on physical examination; he is found to have neck rigidity, confusion, and photophobia. There are no focal neurological deficits. A head CT is normal without mass or hydrocephalus. A lumbar puncture was performed and cerebrospinal fluid (CSF) is sent to analysis while ceftriaxone and vancomycin are started. Which of the following additional antimicrobials should be added in the management of this patient?

Accepted Answer

Ampicillin

Answer

Trimethoprim-sulfamethoxazole (TMP-SMX)

Answer

Amphotericin

Answer

Meropenem

Answer

Clindamycin

Question 8

A 27-year-old man presents to the emergency department with weakness and a fever for the past week. The patient is homeless and has a past medical history of alcohol and IV drug abuse. His temperature is 102°F (38.9°C), blood pressure is 107/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for a tremulous patient with antecubital scars and a murmur over the left lower sternal border. Blood cultures are drawn and the patient is started on vancomycin and ceftriaxone and is admitted to the ICU. The patient's fever and symptoms do not improve despite antibiotic therapy for which the initial identified organism is susceptible. Cultures currently reveal MRSA as one of the infective organisms. Which of the following is the best next step in management?

Accepted Answer

Transesophageal echocardiography

Answer

Obtain new blood cultures

Answer

CT scan of the chest

Answer

Nafcillin and piperacillin-tazobactam

Answer

Vancomycin and gentamicin

Question 9

A group of microbiological investigators is studying bacterial DNA replication in E. coli colonies. While the cells are actively proliferating, the investigators stop the bacterial cell cycle during S phase and isolate an enzyme involved in DNA replication. An assay of the enzyme's exonuclease activity determines that it is active on both intact and demethylated thymine nucleotides. Which of the following enzymes have the investigators most likely isolated?

Accepted Answer

DNA polymerase I

Answer

DNA ligase

Answer

Telomerase

Answer

Primase

Answer

DNA topoisomerase

Question 10

A 32-year-old woman comes to the emergency department with a 2-day history of abdominal pain and diarrhea. She has had about 8 voluminous stools per day, some of which were bloody. She visited an international food festival three days ago. She takes no medications. Her temperature is 39.5°C (103.1°F), pulse is 90/min, and blood pressure is 110/65 mm Hg. Examination shows a tender abdomen, increased bowel sounds, and dry mucous membranes. Microscopic examination of the stool shows polymorphonuclear leukocytes. Stool culture results are pending. Which of the following most likely caused the patient's symptoms?

Accepted Answer

Omelette

Answer

Home-canned vegetables

Answer

Yogurt dip

Answer

Reheated rice

Answer

Toxic mushrooms

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