The Quizzes about Bacteriology – Part 1

1. A 65-year-old man presents to an emergency room in the United States. He complains of a 6-month history of night sweats, fever, and cough with the production of sputum. He also states that he has lost about 30 pounds in the last year. He denies illegal drug use, but admits to having sex with men. He demonstrated positive immunodeficiency virus serology and a low CD4+ lymphocyte count. Gram stain of his sputum demonstrated thin rods that did not stain. When these organisms were stained with the acid fast stain, they took up the stain. He is most likely to be infected with which of the following organisms?

An 85-year-old homeless man is brought to the emergency room. He says that he has been living on the street for the past 10 years. There is a strong smell of alcohol on his clothing and you suspect he is an alcoholic. He says he has constant headaches, and a fever that comes and goes about every 5 days. He also complains of great pains in his legs. The nurses say that when they cut off his clothes, they found lice. You suspect that he has trench fever caused by which organism?

A 45-year-old man goes to his family doctor complaining of a constant, non-productive cough. The man also has severe chest pains which he says have bothered him for the past week. The man also says that this is unusual for him because it is summer and he usually gets his “colds” in the winter and not in July. When the physician examines the man’s chest, he hears an abnormal or pathological sound upon auscultation. The man had pneumonia with consolidation in both lobes. No organism was isolated from his sputum on blood agar, but the physician gave him a shot of penicillin “just in case”. As it turned out, the penicillin shot did nothing to relieve the man’s distress. After 96 hours, a Gram-negative bacterium from the man’s sputum did grow on buffered charcoal yeast extract. What disease did this man have?

At a state dinner, the menu included steak or fried chicken, baked potato or homemade potato salad, green beans, and a “green” salad. The salad dressing was either Italian or Russian. Dessert included either chocolate cake or apple pie. The beverage was water, iced tea, or coffee. After 3 hours, only the diners who had eaten the potato salad, became violently ill with vomiting, stomach cramps, and/or diarrhea. It became immediately obvious that the source of the food poisoning was the potato salad. When the potato salad was sent to a clinical microbiology lab, which of the following bacteria was isolated in large numbers?

A young boy, 9 years of age, is outside playing in the summer in Texas and steps on a board with a rusty nail in it. The nail goes right through his gym shoe and enters his right foot. He does not tell his parents about it because he is sure his mother will yell at him because she is always telling him not to do what he just did. He is also afraid she will curtail his playing outside privileges. Besides, it did not bleed much and the bleeding stopped before he went in for supper. Besides, the boy’s family did not believe in going to the doctor for every little thing. In fact, the boy cannot remember the last time he saw a doctor. About a week later, the boy developed a sore throat and then 4 days later his parents did take him to the hospital (reluctantly) with difficulty in swallowing, talking, and breathing. Also, the boy began to experience muscle spasms.

The hospital doctor recognized the signs of tetanus and immediately administered tetanus immune globulin. The doctor asked the parents when the last time the boy had received a tetanus shot and they replied that they did not know. After being in the hospital for a week, the boy unfortunately died of respiratory failure. This unfortunate incident occurred because which of the following facts represents the best answer?

A 6-year-old girl in Russia developed a sore throat and was taken to the doctor by her parents. The doctor diagnosed a “strep throat” and gave her a shot of penicillin. The penicillin shot did not help, and the child’s health worsened and she was brought back to the doctor. Now the child complained of more than a sore throat. Now she refused to eat and was very lethargic. She also had a fever of 40°C. When the doctor reexamined the child, he observed a normal chest sound, a productive pharyngitis, and inflamed cervical lymph nodes. A throat culture did not reveal any Group A streptococci, and the child was becoming increasingly lethargic. The doctor then noticed a structure in the back of the child’s throat that looked like a leather membrane. The parents told the doctor when he asked that the girl had received no vaccinations. The doctor then knew what disease he was observing. The organism most likely to be the causative agent of this infection was which of the following?

A patient with a burning epigastric pain is admitted to the hospital, and a gastric biopsy is performed. The tissue is cultured on chocolate agar incubated in a microaerophilic environment at 98.6°F (37°C) for 5 to 7 days. On fifth day of incubation, colonies appear on the plate and curved, gram-negative, oxidase-positive rods are observed. Which of the following is the most likely identity of this organism?

A 2-year-old boy who missed several scheduled immunizations presents to the emergency room with a high fever, irritability, and a stiff neck. Fluid from a spinal tap reveals 20,000 white blood cells per milliliter with 85% polymorphonuclear cells. Gram stain evaluation of the fluid reveals small pleomorphic gram-negative rods that grow on chocolate agar. If an inhibitor is designed to block its major virulence, which of the following would be the most likely major virulence factor?

A local community is in distress due to a natural disaster. After consuming contaminated water, many individuals experience nausea, vomiting, and diarrhea that produce stools resembling rice water. An experimental compound is discovered that prevents the activation of adenylate cyclase and the resulting increase in cyclic adenosine monophosphate (AMP). The toxic effects of which of the following bacteria would most likely be prevented with the use of this experimental compound?

A single, 30-year-old woman presents to her physician with vaginitis. She complains of a slightly increased, malodorous discharge that is gray-white in color, thin, and homogenous. Clue cells are discovered when the discharge is examined microscopically. Which of the following organisms is the most likely cause of her infection?

A 12-year-old girl begins to limp while playing soccer. She has pain in her right leg and upper right thigh. Her temperature is 102°F. X-ray of the femur reveals that the periosteum is eroded. Assuming that this case is managed as an infectious disease, which of the following is the most likely etiologic agent?

A scraping from a painful, inflamed wound is found to contain numerous gram-negative bacteria. Upon questioning, the feverish patient states that he was bitten by a cat while trying to rescue it from a storm drain earlier in the day. Given these observations, which of the following organisms is the most likely cause of infection?

A 40-year-old male, who was in good health earlier, begins experiencing a chronic cough. Over the following 6 weeks, the cough gradually worsens and becomes productive. He is also coughing up blood, and notes weight loss, fever, and night sweats. A sputum sample is positive for acid-fast bacilli. Which of the following pathogenic mechanisms can be primarily attributed to the etiologic agent involved in this disease?

A person living on streets is infected with an invasive salmonella organism that is resistant to most of the antibiotics that could be considered for treatment. It did show sensitivity to quinolones that are bacteriocidal. Which of the following is the best explanation of their mode of action on growing bacteria?

A high school student with a natural immunodeficiency is treated aggressively with a variety of potent antibiotics to overcome several bacterial infections. The most recent problem is caused by S. aureus, which is reported to be vancomycin-indeterminate (VISA). Which of the following statements concerning VISA is correct?

A 3-year-old girl, who has missed several scheduled immunizations, presents to the emergency room with a fever and troubled breathing. A sputum sample is brought to the laboratory for analysis. Gram stain reveals the following: rare epithelial cells, 8 to 10 polymorphonuclear leukocytes per high-power field, and pleomorphic gram-negative rods. As a laboratory consultant, which of the following interpretations is correct?

A 25-year-old medical student presents with a ruptured appendix. A peritoneal infection develops, despite prompt removal of the organ and extensive flushing of the peritoneal cavity. An isolate from a pus culture reveals a gram-negative rod identified as Bacteroides fragilis. Anaerobic infection with B. fragilis is best characterized by which of the following?

Several days after an unprotected sexual encounter, a healthy 21-year-old male develops pain and pus on urination. A Gram stain reveals gram-negative diplococci. Which of the following structures is responsible for adherence of the offending microbe to the urethral mucosa?

A 1-week-old newborn develops meningitis. Short, gram-positive rods are isolated. History reveals that the mother had eaten unpasteurized cheese from Mexico during pregnancy, and she recalled having a flu-like illness. Which of the following is the most likely etiologic microorganism?

A 30-year-old male patient is seen by the emergency service and reports a 2-week history of a penile ulcer. He notes that this ulcer did not hurt. Which of the following conclusions/actions is most valid?