Micro Final
Which of the following is of growing concern due to increasing resistance to vancomycin?
Enterococci
Please select the INCORRECT statement regarding the anatomy and physiology of the genitourinary system.
The role of bacteria detected in urine by DNA studies and standard culture methods has been well characterized.
Memory B cells are formed during the primary response so that upon secondary antigen exposure, a faster and more vigorous antibody response ensues
True
A person who frequently takes a particular antibiotic may become resistant to that medication.
False
Methicillin is an antibiotic related to Amphotericin B.
False
The calf most likely became infected through contact with veterinarians.
False
If a cell did not express any of the pattern recognition receptors (PRRs), to which of the following would it still respond?
cytokines
If a Salmonella strain developed the ability to better resist low pH, the infectious dose (ID) of the organism would
decrease
Moist heat primarily destroys microbes by
denaturing their proteins
Which of the following pairs is INCORRECT?
Memory cells-IgM
Primary amebic meningoencephalitis (PAM) is caused by Naegleria fowleri, a free-living amoeba commonly found in warm fresh water and soils. It grows best at temperatures of up to 115° F and is found all over the world. Typically, fewer than five people per year contract PAM in the United States, making it a rare event; however, it is one that is usually fatal. PAM is contracted when N. fowleri is breathed into the nasal cavity during swimming, or by practices such as nasal irrigation, but it is not contracted by drinking contaminated water. Initial signs and symptoms of the disease resemble those of meningitis, and include headache, fever, stiff neck, and vomiting. After attaching to nasal mucus membranes, N. fowleri migrates to the brain along the olfactory nerves. There it multiplies, destroying nervous tissue, especially in the frontal lobes. This leads to swelling, seizures, coma, and altered mental status; death occurs within a week. Several medications have been used to treat PAM, but until recently, with little success. In 2013, however, the CDC authorized the investigational use of an anti-parasitic drug called miltefosine that, in combination with existing treatments, has been effective in curing certain cases of PAM. In June 2014, an 11-year old boy in Florida experienced headache, a slight fever, stiff neck, and vomiting. He was diagnosed with viral meningitis and was hospitalized. A sample of his cerebrospinal fluid (CSF) tested negative for motile ameba; other routine tests were also negative. The child's condition deteriorated over the next few days, and he exhibited confusion and slurred speech; he also suffered seizures. Within 4 days, the patient had to be intubated for breathing assistance. At this time, a second CSF sample was tested for motile ameba, and this time ameba were detected. The physicians at the hospital immediately contacted the CDC via the Florida Department of Health (FDH) to access miltefosine to treat the patient but before the medication arrived, the patient died. The FDH interviewed the patient's parents and learned that they had just returned from a vacation in Costa Rica where the family had zip-lined, swum, and used a water slide at some hot springs in the resort where they were staying. The patient had first become ill 4 days after these activities. The parents could not remember any other times in either Costa Rica or Florida in which the child might have inhaled water. Water from the hot spring was tested and N. fowleri was detected. The CDC confirmed the PAM diagnosis in the patient by real-time polymerase chain reaction, amplifying N. fowleri nucleic acid from the patient's CSF. The child's parents were aware of the risks of N. fowleri in Florida, but did not know that the organism occurs worldwide. PAM should be considered if a patient has meningitis-like signs and symptoms and also a history of swimming in fresh water within 1-9 days of becoming ill. Early diagnosis and rapid treatment are considered essential in this disease because it is so frequently fatal. Miltefosine, in combination with existing treatments, has been effective in curing three children with PAM (the first survivors of PAM in the U.S. in 35 years). Two of the children were diagnosed quickly (within 36 hours of becoming ill), and were given the recommended treatment in combination with miltefosine. The children were also cooled to reduce brain swelling (a procedure called therapeutic hypothermia). Both children recovered fully and without lasting neurological damage. The third child recovered but has suffered neurological damage that is likely permanent. This child was also given miltefosine, but only several days after illness onset. He did not receive cooling treatment. Update*: Originally, miltefosine had to be obtained from the CDC, but it is now commercially available. Nonetheless, if a clinician suspects PAM, the CDC must be alerted. The causative organism of PAM is a ______.
Protozoan
Please select the pair that is incorrectly matched, regarding establishing an infection.
Siderophores - injecting toxins
Which of the following microbes have strains (called MRSA) that are highly resistant to many (beta)-lactam medications?
Staphylococcus aureus
Which of the following invade(s) intestinal cells? 1. Shigella species 2. Vibrio cholerae 3. Helicobacter pylori 4. Giardia lamblia
1
Which of the following produce functionally similar/identical toxins? 1. Shigella dysenteriae 2. E. coli O157:H7 3. Vibrio cholerae 4. Giardia
1 and 2
Which of the following statements about T cells and dendritic cells are TRUE? 1. Dendritic cells activate naïve helper T cells 2. Dendritic cells activate naïve B cells 3. Dendritic cells activate naïve cytotoxic T cells 4. Effector TH cells activate naïve cytotoxic T cells 5. Effector TH cells activate naïve B cells
1; 3; 5
Carbon has an atomic number of 6. Carbon has 4 valence electrons. Based on this, calculate how many more electrons a single carbon atom needs in order to fill its outer electron shell.
4
Calculate the total amount of vancomycin received by the patient in this case, given that standard antibiotic treatment for C. difficile infections is 125 mg of vancomycin four times daily.
5 g
Forty people attended the lunch party. Of these, 35 were interviewed by CDC personnel. The remaining 5 people were not available for the interview. What percentage of people were questioned?
87.5%
Which of the following is an example of microbial evolution leading to the emergence of a disease?
A bacterial cell acquiring the ability to produce a protective capsule
What type of epidemic does the figure show?
A common-source epidemic: many people became infected simultaneously
Which of the following statements about a commensal organism is FALSE?
Commensal organisms cannot be opportunistic.
From which of the following would you be most likely to obtain a pure culture?
A single colony on a streak plate.
What is apoptosis?
A type of programmed cell death.
On which of the following DNA strands will UV light have the most effect?
ACTTGCTTAC
Identify the differential staining method that is most important in the diagnosis of tuberculosis.
Acid-fast stain
How could this type of scenario be avoided in the future?
All equipment/ supply carts in healthcare facilities should be disinfected between procedures
If another antigen, antigen Y, was also present and bound to B cell Y, what would the outcome be?
B cell X would produce anti-X antibodies and B cell Y would produce anti-Y antibodies.
The clonal selection theory states that
B cells that recognize a given epitope multiply to form a family of identical cells.
Which of the following would NOT be experienced by a person with symptomatic dengue fever?
Bloody sputum production
A patient has meningococcal meningitis, an acute life-threatening disease caused by the bacterium Neisseria meningitidis. Which type of antibiotic would be the most appropriate to prescribe?
Broad-spectrum, high therapeutic index
Which of the following dyes is used first in an acid-fast stain?
Carbol fuchsin
Select the INCORRECT statement regarding cat scratch disease.
Cat scratch disease is not serious; it is never associated with any complications.
Which of the following pairs regarding the central nervous system (CNS) and peripheral nervous system (PNS) is mismatched?
CNS - brain and peripheral nerves
Scientists isolated a new species of bacteria growing in sediments collected from a 63 meter deep site at the bottom of Lake Washington in Seattle This species, named Labrys methylaminiphilus, is capable of obtaining its carbon and energy needs from methylamine (CH3NH2), a derivative of ammonia (NH3) in which one H atom is replaced by a methyl (CH3) group. L. methylaminiphilus grows at a temperature range of 10-35°C, with optimal growth at 28-30°C, and a pH range of 4.0-9.5, with optimal growth at 5.0-7.0. Because methylamine is a single carbon compound resulting from the breakdown of decaying organic matter, methylotrophic ("methyl-feeding") bacteria like L. methylaminiphilus play an important role in carbon cycling in lake sediments and other environments. Consider the growth of L. methylaminiphilus on methylamine. How would you classify this species based on its metabolism?
Chemoorganoheterotroph
Which of the following describes the function of toll-like receptors (TLRs)?
Detect pathogen-associated molecular patterns
How did the CDC confirm the PAM diagnosis?
Detection of N. fowleri nucleic acid in the patient's CSF.
Which of the following is NOT an outcome of fever?
Direct destruction of microbes.
The calf in the case was most like infected through which mode of transmission?
Direct skin-to-skin contact
Which of the following statements about normal microbiota is FALSE?
Disruption of the normal microbiota has little effect on the host.
Which of the following do you think means "blood clots within vessels throughout the body"?
Disseminated intravascular coagulopathy
Which of the following statements about Vibrio cholerae and the disease it causes is FALSE?
Drinking several liters of pure water is effective for treatment
A treatment given to counteract the effect of shiga toxin would also decrease the severity of infections caused by
E. coli O157:H7
n April 2015, the Ohio Department of Health was contacted regarding a suspected case of botulism, a serious and potentially fatal neuroparalytic illness. The signs and symptoms of this disease are caused by botulinum toxin, a neurotoxin released by the bacterium Clostridium botulinum. Within 2 hours of the first case, an additional 4 people with possible signs and symptoms of botulism also showed up at the local emergency room. It was quickly discovered that all of the patients had eaten at the same church potluck that day. The CDC responded immediately by confirming the diagnosis of botulism, identifying and treating other possible patients, and determining which food was contaminated with botulinum toxin. It was found that all of the ill people had eaten potato salad which had been made with home-canned potatoes. The person who made the salad had canned the potatoes using a boiling water canner. When making the salad, the person had used the potatoes directly from the cans, without first heating them. CDC personnel confirmed that 29 people contracted botulism from the potato salad. One patient died. The remaining patients were treated and recovered. Clostridium botulinum, the bacterium that causes botulism, is a rod-shaped, endospore-forming, toxin-producing organism. Which is true about endospores?
Endospores allow bacteria to withstand adverse conditions
Which of these infections is NOT transmitted by mosquitoes?
Ebola disease
The potatoes used in the salad were home-canned using a boiling water approach. Why was this method insufficient to prevent botulism?
Endospores can survive several hours of boiling.
After it was cooked, the perlo was left at room temperature overnight. On the day of the party, the food was heated for an hour at a high setting in a slow cooker. Even though the perlo was effectively heated, people who ate it still got ill. What can you conclude from this information?
Enterotoxin A is heat stable (not destroyed by heat).
. The calf in this case died as a direct result of the MRSA infection.
False
All of the following are matching pairs EXCEPT
Fomite - droplet transmission
Which of the following scientists first challenged spontaneous generation?
Francesco Redi
A pharmaceutical company is developing a new antibacterial medication that is safe for use in humans. Which two of the following would NOT be good targets for the medication?
Glycolytic pathway enzyme activity; 80S ribosome functioning
How did John Tyndall's work help to explain why some scientists had difficulty reproducing Pasteur's work proving that life comes from pre-existing life?
He demonstrated that some broths require greater boiling times because they contain heat-resistant bacterial forms.
Which of the steps shown is unique to the endospore stain? Counterstain, Alcohol decolorizer, Primary stain, Heat
Heat
Which of the following statements indicates the significance of Koch's work?
His postulates are used to show that specific microorganisms can cause specific diseases.
Select the FALSE statement about animal virus entry into host cells.
Human immunodeficiency virus can enter cytotoxic T cells.
Under what circumstance could the number of cases from a common-source outbreak remain high over a much longer period of time and not decrease to zero?
If the source continued to infect new people e.g. if a restaurant continues to serve contaminated food.
In an effort to get rid of the woman's CDI in this case, the doctor prescribed the antibiotic vancomycin. The patient took the antibiotic daily for 10 days. Her stool was collected every five days and checked for C. difficile. The results were recorded as colony forming units (CFUs) per gram of feces. Evaluate the hypothetical data on the chart below and select the correct statement.
Initially the amount of C. difficile decreased, but after the antibiotic course was completed, the number of bacteria began to increase again.
Thirteen people visited an emergency department at a military hospital for treatment of gastrointestinal signs and symptoms including nausea, vomiting, abdominal pain and diarrhea. All of the patients had attended a work lunch party 2-3 hours before becoming ill. Initial investigation by CDC personnel into the cause of the illnesses suggested bacterial contamination of one of the main dishes served at the lunch. Indeed, subsequent CDC laboratory analysis revealed the presence of bacterial toxin in one of the dishes, supporting the initial findings. Improper food handing and preparation were identified as the cause of the bacterial contamination. People who attended the lunch party and who developed signs and symptoms of gastrointestinal illness within 24 hours after the party were interviewed by CDC personnel. Forty people attended the lunch party. Of these, 35 were interviewed by CDC personnel. The remaining 5 people were not available for the interview. Samples of the 4 main dishes were tested for bacterial toxins. The dishes were perlo (chicken/sausage/rice dish), chicken wings, pulled pork and green beans with potatoes. Storage, preparation and handling of the dishes are summarized in the table. Laboratory testing identified Staphylococcus aureus as the source of the toxin; the toxin was staphylococcal enterotoxin type A. Bacillus cereus and Clostridium perfringens were eliminated as possible sources of toxins in the tested foods. What part of the body would you expect to be affected by enterotoxin?
Intestines
S. enterica can switch to anaerobic respiration in tetrathionate broth. What does this tell us about the organism?
It is a facultative anaerobe
What is the disadvantage of an antibiotic with a short half-life?
It must be given multiple times daily.
Rocky Mountain spotted fever was first noticed in the Rocky Mountain area of the U.S.A., which is how it got its name. However, this disease actually occurs throughout the U.S.A. The disease is caused by a Gram-negative bacterium called Rickettsia rickettsii, which is transmitted by the bite of infected ticks, including various dog and wood tick species. Signs and symptoms of RMSF include fever, nausea, vomiting, loss of appetite, stomach pain, and a macular (flat, red) or papular/maculopapular (red, bumpy) rash that appears after a few days. The rash is noticeable in that it is found everywhere on the body, including the palms of the hands and the soles of the feet, which is not typical of most rashes. The rash may progress to petechiae, which are small purplish spots caused by bleeding in small blood vessels under the skin. RMSF can be successfully treated; however, untreated RSMF is serious and may result in pneumonia, hepatitis, myocarditis, renal failure, encephalitis, and gangrene, any of which may be fatal. Patient A, a 7-year old female, was taken to an emergency department (ED) in Oklahoma with fever (39.3°C), malaise, nausea, vomiting, and abdominal pain. The child was diagnosed with viral gastroenteritis and sent home. Four days later the patient was taken to a different ED with the same symptoms as well as irritability, photophobia, and various myalgias. In addition, the patient had hepatosplenomegaly and a papular rash (red, bumpy spots) with scattered petechiae on her arms, legs, palms, and soles. Her blood test results are summarized in the table below. At this point, RMSF was suspected. The patient was transferred to a pediatric ICU and given intravenous (IV) doxycycline, but she died of respiratory failure 6 days after first coming to the ED. Anti-R. rickettsii IgG antibodies as well as rickettsia bacteria were detected on autopsy of the child. Shortly thereafter, patient A's 3-year old sister developed fever, headache, vomiting, muscle aches, and a rash, including on her palms and soles. She was treated with doxycycline and recovered. Neither child had history of a tick bite but the family had a dog that often had ticks, and patient A and her sister also frequently played in grassy areas near their home. Patient B, a 24-month old male, was taken to a pediatrician in Kentucky after experiencing a fever of 38.3°C for a day along with a papular rash. The child was diagnosed with a viral infection and given non-steroidal anti-inflammatory drugs. The patient continued to have fevers and a rash over the next two days, and was taken to an ED, where he was again diagnosed with a viral infection, and sent home. Four days after the initial treatment, the child was evaluated again by a pediatrician because he was lethargic and reluctant to walk. At this point, blood tests were taken, the results of which are summarized in the table. The next day the patient was admitted to the ICU and given IV antibiotics. Two days later the child was transferred to another hospital where examination revealed that he had a petechial rash on the groin, trunk, wrists, and palms. He was given IV vancomycin, doxycycline and cefotaxime, but he continued to deteriorate and died of multiple system failure after 8 days. Anti-R. rickettsii IgM antibodies as well as rickettsia bacteria were detected on autopsy of the child. The patient's parents did not recall a tick bite; the family had not traveled, and had not participated in outdoor activities but they did live near some woods. However, two days before patient B died, his mother was hospitalized with fever, diplopia (double vision), headache, and dizziness. She also had anti-Rickettsia antibodies. She was given oral doxycycline and IV ceftriaxone and recovered. Patient C, a 14-month old male, was taken to a community clinic with a fever (39.8°C) and a maculopapular (red, bumpy) rash. He also had thick white discharge on his tongue, a sign of possible thrush (fungal infection). A chest x-ray showed possible infiltrate (substance denser than air in the lung lobe) in his right lung. He was given two intramuscular antibiotics and an antifungal medication. The next day his fever had risen to 41°C, and he was experiencing nausea, vomiting, lack of appetite and dehydration, and he was transferred to a different hospital for treatment of thrush, pneumonia and roseola infantum (characterized by high fever and a rash). After three days he was transferred to a third hospital, having been diagnosed with sepsis and disseminated intravascular coagulopathy (DIC). The patient was given IV vancomycin and ceftazimidine but died of pulmonary hemorrhage six days after he was brought to the initial clinic. No autopsy was performed. There was no evidence of a tick bite but the patient lived in an area with grass and woods, and also played frequently with dogs known to have ticks. Serum taken subsequently from the patient's brother showed IgG and IgM antibodies to R. rickettsii, indicating recent exposure to this pathogen. Identify the unusual characteristic of the RMSF rash.
It occurs on the palms and soles
Select the statement that does NOT apply to a fluorescence microscope.
It uses electrons to produce an image of the specimen.
Please choose the method of antimicrobial susceptibility testing that involves measuring and evaluating zones of inhibition around antibiotic discs placed on a culture of bacteria prior to incubation.
Kirby-Bauer test
An 80-year-old woman in a nursing home develops fever and chills, a productive cough with bloody, gelatinous sputum (resembling red currant jelly), and chest pain. She is given a combination of antibiotics, including a carbapenem, but fails to respond to the treatment. Within a few days, she dies. Given this information, you can conclude that the woman likely died from
Klebsiella pneumonia
Which of the following diseases is a zoonosis?
Leptospirosis
Leptospirosis is a disease that can be contracted by swimming in lakes contaminated with urine of infected rodents. Signs and symptoms develop 2 to 4 weeks after exposure and include fever, headache, chills, and muscle aches. Based on this information, which of the following can you conclude?
Leptospirosis is a zoonotic disease.
Patient A underwent a uterine dilation and curettage (D&C) procedure at the healthcare facility where she worked. Approximately a month later, she returned to the same facility complaining of jaundice, lack of appetite, and abdominal distress. Laboratory test results indicated that the patient had developed hepatitis C, which is caused by hepatitis C virus (HCV), a blood-borne pathogen. The possibility that the patient had contracted the virus by accidental occupational exposure was investigated and eliminated. A review of all patient records at the healthcare facility for the day of patient A's surgery revealed one other person (patient B) who had a procedure earlier on the same day as patient A. Patient B had a previously reported hepatitis C infection. Blood samples from both patients were sent to the clinical laboratory for molecular analysis, and results showed that patient A had likely contracted the HCV from patient B. Patients A and B underwent different procedures in different operating rooms with different equipment, and had different surgeons, but they had the same anesthesiologist. The anesthesiologist was assigned a cart for his/her equipment and medication, and moved the cart from room to room during the day. In this case, the anesthesiologist had treated patient B immediately before treating patient A. The anesthesiologist did not use the same needles on the two patients but did put potentially contaminated items such as used needles onto the cart. There were no protocols or procedures in place for cleaning and disinfecting the cart. It was not possible to identify the exact way that patient A contracted HCV from patient B, but as the anesthesiologist had transported the cart from one procedure room to another without cleaning it between, it was concluded that most likely patient A had contracted HCV from patient B from contaminated equipment or supplies on the anesthesiologist's cart. This is an example of a nosocomial infection—an infection acquired by a patient in a hospital or other healthcare facility. What part of the body is affected with hepatitis?
Liver
A new disease is discovered that is often fatal to humans. Its natural cycle involves baboons and mice, and the causative agent is transmitted between those hosts by mosquitoes. Humans acquire the disease after being bitten by a mosquito that has previously fed on an infected baboon. What is the vector of the disease?
Mosquito
Which of the following best describes how Mycobacterium leprae infection can lead to peripheral nerve damage in Hansen's disease?
M. leprae invades peripheral nerve cells, which are then targeted and destroyed by immune cells, leading to disabling deformities.
Which molecule is responsible for displaying fragments of proteins made within the cell and would therefore be useful in detecting a virally infected cell?
MHC
Identify the difference between the use of depth filters and membrane filters in sterilizing fluids.
Membrane filters have smaller pores than depth filters, but depth filters have complex passages that retain microbes while letting the fluid through. Both methods are efficient.
In which patient(s) was the liver affected?
Not enough data to answer this question.
Why did CDC personnel interview people who became ill within 24 hours after party, and not only people who became ill within 2-3 hours of the party?
Not everyone who ate the contaminated food would necessarily develop illness or go to the hospital within 2-3 hours. Factors such as how much food they ate must be taken into account.
Which of the following pathogen-reservoir pairs is INCORRECT?
Shigella species - chicken
Which of the following best describes how papillomavirus infection leads to the development of warts?
Papillomaviruses replicate within the nucleus of infected cells, some of which grow abnormally, producing a "wart."
Which patient had a white blood cell count within the normal range?
Patient B
Why were patients A and B not given antibiotics immediately?
Patients A and B were initially diagnosed with viral infections
Why is PAM sometimes misdiagnosed as meningitis?
People with either of these diseases develop fever, headache, stiff neck, and vomiting.
Samples of the 4 main dishes were tested for bacterial toxins. The dishes were perlo (chicken/sausage/rice dish), chicken wings, pulled pork, and green beans with potatoes. Storage, preparation and handling of the dishes is summarized in the table. Which food do you think is likely to have caused the reported illness, and why?
Perlo, because it was stored at room temperature for 8 hours, giving plenty of time for bacterial contamination and toxin production.
Which of the following pairs about protozoan and helminth pathogenesis is mismatched?
Plasmodium vivax—attaches to Duffy antigen on white blood cells.
You are a pregnant woman in your last trimester. Which viral disease is potential the most serious, and why?
Primary genital herpes infection; the baby may acquire HSV-2 during birth and this virus may prove fatal to the neonate.
In which way does cytomegalovirus avoid the cellular immune response?
Producing fake MHC class I molecules that NK and Tc cells do not recognize
Which of the following is NOT a method used by pathogens for penetrating skin or mucous membranes?
Production of endotoxin
What type of programmed cell death also triggers an inflammatory response, recruiting various components of the immune system to the region?
Pyroptosis
A man complains of headache, muscle and joint pain, and fever. He develops a rash characterized by faint, pink spots that starts on the palms of his hands, wrists, and the soles of his feet, and then spreads to his body. He recalls a recent tick bite but there does not appear to be any inflammation at that site. He is given doxycycline and recovers fully. Based on this information, you can conclude that he likely has ______.
Rocky Mountain spotted fever
The signs and symptoms of botulism are a result of nerve damage caused by botulinum toxin. Given this information, select which of the following you think would be a treatment for affected people.
Respiratory support and antitoxin (neutralizes toxin)
Your elderly patient has a wound infection. The causative organism is cultured and identified as Staphylococcus epidermidis. Your patient had a hip replacement two years prior to developing this infection. Which of the following would you NOT tell your patient?
S. epidermidis is resistant to methicillin and can only be treated with the antibiotic vancomycin
Which of the following types of repair does not require the standard DNA polymerase with proofreading capability?
SOS repair
The atomic number of carbon is 6, and the atomic number of silicon is 14. Knowing that carbon forms 4 covalent bonds with 4 hydrogen atoms to form methane, predict how silicon bonds with hydrogen atoms to form the compound silane.
Silicon will form 4 covalent bonds with 4 hydrogen atoms
Over the past several years, methicillin-resistant Staphylococcus aureus (MRSA) has become infamous as the cause of skin infections among football players, wrestlers, fencers, and other athletes who share equipment or engage in contact sports. MRSA strains are resistant to many drugs, including methicillin, a penicillin derivative commonly used to treat staphylococcal infections. Spread of the bacterium from the initial infection site can lead to serious (often fatal) involvement of the heart, lungs, and bones. Clinicians now distinguish between HA (hospital-acquired) MRSA and CA (community-acquired) MRSA. Humans are not the only victims of MRSA, as the San Diego Zoo reported a MRSA outbreak involving a newborn African elephant and three of its human caretakers. The caretakers exhibited cutaneous pustules that were laboratory confirmed as MRSA infection, and an investigation was initiated to determine the course and scope of the outbreak. After the elephant calf was born at the zoo, its mother was unable to provide enough milk. The calf was separated from the mother, and a variety of zoo caretakers bottle-fed the calf and played with it daily. These activities undoubtedly helped spread the bacterium, since S. aureus is most commonly spread through contact with skin lesions. Because the calf was still not receiving sufficient nutrients through bottle feeding, surgeons inserted a central feeding line into a vein on the calf's neck. Three days later, cellulitis developed at the surgical site, and shortly thereafter pustules appeared on the calf's leg and elbow. Samples from all three locations were laboratory confirmed as MRSA, and although treatment with antibiotics successfully resolved the infection the calf failed to thrive and was euthanized. To determine the scope of this community-acquired MRSA outbreak, investigators obtained rectal and trunk cultures from the other 11 African elephants at the zoo and nasal cultures from 53 of 55 elephant caretakers. While no other elephants tested positive for MRSA, epidemiological investigation identified two caretakers as carriers and revealed a total of 20 suspected (based on signs and symptoms alone) or confirmed (through laboratory testing) MRSA infections among the caretakers. The strain was identified as MRSA USA 300, the most common strain implicated in CA-MRSA infection. This strain was identical to that isolated from the elephant calf and from the wounds on three of the caretakers. Investigators surmised that the calf had become infected with MRSA after being exposed to caretakers carrying the same strain, and transmission then occurred from the calf to other human caretakers. It was also noted that veterinary staff workers were more likely to wear personal protective equipment and were thus less likely to be infected than were the nursery staff or the elephant keepers. MRSA is most commonly associated with infections of the
Skin
What is the name of the organism causing the illness in the people who attended the lunch party?
Staphylococcus aureus
During which stage of growth does cell division equal the rate of cell death?
Stationary phase
Which of the following are bacterial diseases of the upper respiratory tract?
Streptococcal pharyngitis and diphtheria
A student complains to her lab partner that she has a runny nose and is feeling unwell. Thinking she may be developing a cold, the student goes home from school. Over the next three days, she develops a cough, fever, and chest pain. Her cough becomes productive and she is alarmed to notice that her sputum is pinkish in color. The student's chest pain becomes worse, and she is unable to breathe deeply. After a week, she starts to sweat profusely; her temperature returns to normal and she recovers. Given this information, you can conclude that the cause of the student's signs and symptoms was likely
Streptococcus pneumoniae
Please choose the microorganism that is the most common cause of bacterial meningitis in adults
Streptococcus pneumoniae
Which of the following pattern recognition receptors is/are anchored in the host cell membrane?
TLRs and CLRs
The initial case was a 2 year old girl who was brought to the doctor's office after experiencing three days of diarrhea and fever. A sample of the child's stool was sent to the lab, and S. enterica Typhimurium, which is usually contracted from undercooked poultry and eggs, was isolated. On subsequent investigation into the source of the child's infection, it was determined that the family had recently bought two small pet turtles from a street vendor. Turtles and other reptiles are well known to be sources of human Salmonella infections, and in fact, the sale of small turtles (those with carapace lengths of less than 4 inches) has been prevented in the United States since 1975. Eventually, 135 patients in 25 states were identified in the outbreak. Seventy patients were identified with primary infections. They were questioned about contact with turtles, and 37% of them reported that they had owned or handled turtles; 81% of those turtles were from street vendors. Although some of the patients in this outbreak required hospitalization, all of them recovered fully and nobody died. One of the methods used to identify S. enterica in the lab is growth in tetrathionate broth, a selective enrichment medium for this organism. What does this mean?
Tetrathionate broth inhibits the growth of non-Salmonella bacteria and encourages the growth of Salmonella.
DNA takes the form of a double helix in which two antiparallel strands of nucleotides are held together by hydrogen bonds that form between the nucleobases. There are two hydrogen bonds between each A-T pair, and three hydrogen bonds between each G-C pair. Imagine you extract DNA from two different species of bacteria, heat it, and measure the temperature at which the DNA strands separate. If the DNA from species 1 separates at a lower temperature than that of species 2, what can you conclude about their DNA?
The DNA of species 2 has more G-C base pairs than the DNA of species 1.
A 24-year-old woman experienced repeated episodes of watery diarrhea, abdominal pain, and fever, and was diagnosed as having Clostridium difficile infection (CDI). Shortly before she developed the CDI, the woman had been taking an oral antibiotic for a tooth infection. Initially, her doctor advised her to stop taking the antibiotic, hoping that her intestinal normal microbiota, which had been negatively impacted by the antibiotic, would recover and outcompete the C. difficile, aiding the woman's recovery. However that approach failed, so the doctor then prescribed a different antibiotic for the woman: a 10-day course of vancomycin. At first it seemed that the second antibiotic had resolved the CDI, but as soon as the patient completed the course of antibiotics, her signs and symptoms returned. Eventually the woman was given a fecal transplant, which involved inserting fecal bacteria taken from a healthy person into her intestinal tract. The donor in this case was the patient's sister. The transplant was a success and the patient recovered. Which of the following explains why the woman in this case developed the signs and symptoms of CDI, an intestinal infection?
The antibiotic harmed her intestinal normal microbiota, allowing C. difficile to flourish (thrive).
In a capsule stain
The background stains dark, so that the capsule is visible
A bacterium is resistant to penicillin. Which of the following are possible causes of resistance?
The bacterium has altered outer membrane porin proteins; the bacterium lacks a cell wall, the bacterium produces penicillinase; the bacterium's PBPs do not bind penicillin
Treatment of leptospirosis with penicillin or other bactericidal antibiotic sometimes results in a Jarisch-Herxheimer reaction, characterized by fever, chills, headache, malaise, tachycardia and rarely, death. What might be the cause of this reaction?
The causative organism of leptospirosis is a Gram-negative bacterium; when the bacterium is killed by antibiotic, endotoxin is released into the bloodstream, causing the observed reaction.
Inactivation of a cell's interferon genes would likely have which outcome?
The cell would no longer alert neighboring cells to the presence of double-stranded RNA
A typhoid fever (bacterial disease) outbreak that originated at a ski resort in Switzerland eventually resulted in more than 430 cases of the disease appeared in at least six countries. Which is the most likely reason for this outcome?
The disease has a long incubation period, so infected people had flown home before becoming ill, spreading it in their own countries
In this case, which of the following actions most likely allowed S. aureus to disseminate (spread internally) from the initial site of infection in the calf?
The insertion of a central feeding line into a vein on the calf's neck
When bacteria such as S. enterica infect the intestinal tract, inflammation results. This is one of the body's immune defenses. Researchers have recently discovered that tetrathionate is produced in the intestinal tract as a result of inflammation. Why is this important?
The presence of tetrathionate gives the Salmonella a competitive advantage over the normal microbiota such as E. coli.
Select the CORRECT statement regarding mumps and oral herpes.
There is an effective vaccine that protects against mumps
Please choose the statement that best describes the normal microbiota of the nervous system.
There is no normal microbiota present.
DNA takes the form of a double helix in which two antiparallel strands of nucleotides are held together by hydrogen bonds that form between the nucleobases. There are two hydrogen bonds between each A-T pair and three hydrogen bonds between each G-C pair. You can extract DNA from bacteria and measure the temperature at which the DNA strands separate as they are heated. From this, you can calculate the percent GC content of their DNA. Although research has since refuted the idea (L.D. Hurst and A.R. Merchant, Proc Biol Sci. Mar 7, 2001; 268(1466): 493—497), the "thermal adaptation hypothesis" proposed that high GC content might be an adaptive response to high temperature. If this hypothesis were true, which of the following bacteria do you predict would have the highest number of G-C pairs in their chromosome?
Thermophiles living in a hot spring.
Which of the following is NOT a potential reservoir of infectious agents in healthcare settings?
These are all potential reservoirs of infection
Flagella are typically difficult to see using a light microscope because
They are too thin to be seen, and require a special type of staining
How do dermatophytes cause disease in humans?
They infect keratinized regions of the body.
Which of the following best describes why AIDS patients respond poorly to medications used to treat Cryptococcus neoformans infections?
They lack T cells normally assist the activity of these antifungal medications.
A patient, a 27-year old man, has severe vomiting and copious diarrhea—he is producing large volumes of watery diarrheal discharge that is milky-white in color, resembling water that has had rice cooked in it. He lives 30 minutes from the nearest hospital. Based on this information, what would be the correct course of action?
Transport him to the hospital immediately for intravenous rehydration.
An example of microbial evolution is the development of antimicrobial drug resistance in microbes as a result of overuse/misuse of medications by humans.
True
Which of the following immune responses is best suited to prevent a virus from infecting a cell?
Virus-specific antibodies
Negative staining is commonly used to determine if bacterial cells have
a capsule
Following the Exxon Valdez oil spill, beaches in Prince William Sound were treated with nitrogen compounds in order to enhance the bioremediation of the oil. What does this tell you about the ecosystem of these beaches?
With the arrival of large quantities of hydrocarbons, nitrogen was a limiting nutrient for microbial growth.
All of the following about the Kirby-Bauer test are true EXCEPT
a large zone of inhibition indicates extreme sensitivity to a drug.
Which of the following is the only completely effective method of preventing sexually transmitted infections?
abstaining from sexual intercourse
A child is sent home from class after complaining of feeling unwell. His symptoms include a severe sore throat with pus on his tonsils, swollen lymph nodes, and a mild cough. He also has conjunctivitis and diarrhea. His parents take him to the doctor, who prescribes a course of penicillin. Three days later the child has shown little improvement, and his parents bring him back to the doctor who tells them to give the child analgesics for his pain. Within a week, the child begins to recover and after three weeks he is completely well. Based on this information, it is likely that the child had
adenoviral respiratory tract infection
The rate of growth in flask 3 is substantially faster than that in flask 1 and somewhat faster than that in flask 2. The E. coli in this tube can be most accurately described as undergoing ______.
aerobic respiration
The rate of growth in flask 2 is substantially faster than that in flask 1, but somewhat slower than that in flask 3. You detect the production of nitrite. The E. coli in this tube can be most accurately described as undergoing _____
anaerobic respiration
As bacteria grow in broth, oxygen becomes depleted. At that point, most bacteria switch to fermentation to continue growing. In tetrathionate broth however, S. enterica can switch to anaerobic respiration. This gives the organism a growth advantage because
anaerobic respiration yields more ATP per glucose molecule than fermentation.
Choose the term that describes the method of Tc cell-mediated killing of a target cell
apoptosis
A culture of bacteria is breaking down sugars to yield energy. This is best described as ______.
catabolism
Negative selection in B and T lymphocytes occurs when
cells bind to self antigens too strongly.
In which of the following does the donor cell direct the process?
conjugation
There are three different gene segments that come together to encode the variable region of an antibody heavy chain molecule. When encoding the light chain, only two different gene segments are joined. The gene segment that is used in encoding the heavy chain but not the light chain is the ______ segment.
diversity
Depending on the environment they are in, E. coli cells are capable of using either fermentation, anaerobic respiration, or aerobic respiration to obtain energy. In order to compare the growth patterns of E. coli under different conditions, you set up an experiment where you inoculate E. coli into 3 different flasks with minimal (glucose plus salts) medium. Flask 2 also contains nitrate. Flasks 1 and 2 are sealed shut and do not contain any oxygen. Flask 3 is covered to prevent contamination but still allow for gas exchange. You measure the growth rate of the cultures by measuring turbidity using a spectrophotometer. You also have equipment available to detect and measure metabolic byproducts. The rate of growth in flask 1 is slower than that in flasks 2 and 3, and you detect the production of lactic acid. The E. coli in this tube can be most accurately described as undergoing
fermentation
Which of the following is experienced with adenoviral respiratory infections but NOT with the common cold?
fever
All of the following are true of genital herpes and its causative agent EXCEPT
genital herpes can always be effectively prevented by condom use.
Spread of S. aureus from the site of infection can lead to involvement (disease) of the
heart, lungs, and bones
From reading this case, you know that
hepatitis C is caused by a virus.
Diversity of antibodies is increased by ______, which leads to deletions/insertions of nucleotides between joined gene segments.
imprecise joining
Gram staining of samples taken from the cutaneous pustules of the caretakers and the calf in this case would have revealed the presence of
irregular clusters of Gram-positive cocci
Boiling is not a reliable method for sterilization because
it does not destroy heat-resistant endospores
Trichomonas vaginalis, a motile protozoan that causes trichomoniasis, can be identified by
its characteristic jerky movements and its size.
Which of the following is NOT an antimicrobial substance?
keratin
Spontaneous generation can be explained as
life arising from dead matter
Consider the figure of a virus infected cell. By directing the host cell to synthesize fake MHC class I molecules, the virus is
making sure its host is not destroyed by TC cells or NK cells.
The MMRV vaccine is used to protect against
measles, mumps, German measles, chickenpox.
How does the pH of a solution change as the hydrogen ion concentration increases?
pH will decrease
Consider the figure. If the purple liquid was distilled water, the researcher would expect the number of colonies on plate A to be _____ as the number on plate B.
more or less the same
The process of antibody-dependent cellular cytotoxicity (ADCC) allows ______ cells to bind to antibody-coated host cells that may have viral proteins in their plasma membrane in order to kill them, inducing apoptosis and limiting viral spread.
natural killer
Your patient is a three-year old child. She is crying, tugging at her left ear and coughing. She also has a low grade fever. You tell the parents she has _______, likely caused by _______.
otitis media; S. pneumoniae or H. influenzae.
Much work is currently being done toward global eradication of which of the following diseases?
polio
Toll-like receptors (TLRs) bind molecules on pathogens. This is helpful to the immune response because TLRs
recognize broad categories of molecules that should not be in our system, as we don't have these molecules on our own cells.
Most initial cases of dengue fever are very mild or even asymptomatic. When a second infection with a different serotype of the five known dengue viruses occurs,
severe dengue may develop, due to antibody-dependent enhancement that facilitates viral entry into macrophages.
All of the following are components of the upper digestive tract EXCEPT
stomach
Some strains of Staphylococcus aureus produce ______ that can cause toxic shock.
superantigens
Alexander Fleming was working with the bacterium S. aureus when he discovered penicillin. He had cultured the bacteria on agar plates, one of which then became contaminated with a mold. He noticed that the S. aureus did not grow immediately next to the mold. After analyzing this observation, he went on to show that
the mold was synthesizing and secreting a bacteria-inhibiting compound.
All of the following are mechanisms for protecting the bladder from bacterial infection EXCEPT
the relatively long urethra in females that is distant from the anus, preventing bacteria from entering the bladder.
Antibiotics prevent the transmission of diphtheria, but are insufficient for treating the disease. Which of the following statements explains this?
the signs and symptoms of diphtheria are toxin-mediated, antibiotics have no effect on the toxin
Which of the following requires that cells be competent?
transformation
Vaccination to protect against rubella is essential because
viral infection can lead to development of significant fetal defects/abnormalities.