Microbiology Review Flashcards
(239 cards)
1
Q
What diverse group of unicellular eukaryotic microorganisms have motility and can be free-living or parasitic?
A
Protozoa
2
Q
Which pair of organisms consists of 2 endospore-forming bacteria?
A
Clostridium and Bacillus
3
Q
In the bacteria name “Staphylococcus aureus,” what does the word “aureus” represent?
A
Species
4
Q
Which type of microorganism is associated with the rancidity of spoiled foods?
A
Lipolytic organisms
5
Q
There are different ways to classify microorganisms. What microorganism can be classified based on the peptidoglycans in its cell wall?
A
Bacteria
6
Q
What parasitic infection is responsible for most deaths globally?
A
Malaria
7
Q
Wiskott-Aldrich syndrome is an X-linked hereditary condition. When can a doctor first diagnose the appearance of signs in a patient?
A
In the first year of life
8
Q
How is the virulence of an organism defined?
A
Ability to cause disease
9
Q
One factor associated with the transmission of infectious disease is the time of survivability of a microorganism on a hard inanimate surface; e.g., E.coli bacteria can survive on hard inanimate surfaces for up to 16 months. This represents a risk for exposure to infectious disease by what type of contact?
A
Indirect vehicle contact
10
Q
Which infectious disease is most likely to be associated with the pathogen S. pneumoniae and H. influenzae?
A
Community-acquired pneumonia
11
Q
The pathology of Candida albicans depends on the area of colonization; for example, colonizing the genitals can cause a yeast infection. What is an additional manifestation of a C. albicans infection likely to occur within an immunocompetent host?
A
Oral thrush
12
Q
The pathology of Escherichia coli depends on the area of colonization; for example, as the source of gastrointestinal illness, it can cause diarrhea. What is an additional manifestation of an E. coli infection?
A
Urinary tract infection
13
Q
A siderophore is a compound produced by bacteria. What is the function of this chemical compound?
A
Obtain iron for growth
14
Q
Which of the following structures is responsible for the motility of bacteria?
A
Flagella
15
Q
Flagella can be in various arrangements in a typical bacterium. What type of bacterium has a single flagellum at opposite poles in the organism?
A
Amphitrichous
16
Q
A bacteria has flagella throughout its surface. What type of arrangement of flagella is this?
A
Peritrichous
17
Q
Clostridium botulinum is an example of an organism that releases an exotoxin. How are exotoxins classified?
A
Soluble protein
18
Q
What structure only aids in surface adherence and has no other purpose?
A
Fimbriae
19
Q
What aspect of Gram-positive bacteria allows species like Clostridium and Bacillus to form endospores?
A
Thick peptidoglycan layer
20
Q
Porin is a structural molecule in bacteriology. Which one of the following is called porin?
A
A protein forming a channel for transport
21
Q
Peptidoglycan is the major component of the prokaryotic cell wall. Its arrangement is one determining factor in the results of a Gram stain. What peptidoglycan structural feature is only found in Gram-positive bacteria?
A
Pentaglycine cross-bridges
22
Q
What is the purpose of the cell wall in bacteria?
A
To prevent osmotic lysis of the cell
23
Q
What structure is observed for the identification of different Gram-negative bacterial species and strains?
A
O antigen
24
Q
What structures lack a cell wall?
A
Mycoplasmas
25
```
Which of the following structures are found in ALL bacteria? Select all that apply.
A. Cell membrane
B. Cytoplasm
C. Flagella
D. Peptidoglycan
E. Ribosomes
```
A. Cell membrane
B. Cytoplasm
E. Ribosomes
26
The Gram-negative prokaryotic bacterial cell wall is multilayered. What is the inner layer of the cell wall made of?
Peptidoglycans
27
In Gram-negative bacteria, the peptidoglycans in the cell wall are connected to an outer cell membrane. What connects these two layers?
Lipoproteins
28
Gram-negative bacteria can release endotoxins during severe systemic infections. What component of the bacteria cell wall is released as part of an endotoxin?
Lipid A
29
In response to nutrient limitations or a harsh environment, some bacteria are able to create a small dehydrated metabolically inactive structure within their cells. The production of this structure allows certain bacteria to survive desiccation, radiation, and exposure to chemicals. What are these called?
Endospores
30
What proteins are able to wrap DNA around them to condense the structure of DNA?
Histones
31
How many histone proteins make up a nucleosome in the making of eukaryotic chromosomes?
8
32
When adenine is the nitrogenous base on a segment of DNA, what is the other nitrogenous base it binds to on the opposite DNA strand through hydrogen bonding?
Thymine
33
What is the term for a strand of nucleic acids and associated proteins that carries the genetic information of an organism?
Chromosome
34
Certain bacteria are capable of generating bioluminescent chemicals under specific conditions. Which of the following refers to the ability of bacteria to share cell density information and regulate patterns of gene expression?
Quorum sensing
35
What is an operon in terms of the regulation of bacterial genes?
Genes that participate in the same metabolic activity
36
What is the primary metabolic activity controlled by the lac operon in bacterial species?
Lactose catabolism
37
Which molecule acts specifically by binding to the promotor site of the lac operon so that the genes can be effectively transcribed?
Catabolite activator protein
38
What type of mutation changes the original codon into another codon that codes for the same amino acid?
Silent
39
Site-specific DNA inversion is made possible by inherent flexibility of enzyme and double-stranded DNA molecules. DNA inversion at secondary crossover sites is a proposed mechanism for control of gene expression, but the stochastic nature of this mechanism has also led to proposals highlighting the adaptive nature of this event. What is a potential adaptive advantage of DNA inversion within bacterial populations?
Generation of variation
40
The process of nucleotide substitution (replication infidelity) occurs during DNA replication. Base pairing depends on electron distribution within nucleotides of parental and newly synthesized DNA. Short-lived physical forms (tautomers) arise and can result in mispairing of bases due to intrinsic pliability rather than a replicative misstep. What is a plausible mechanism for the process of nucleotide substitution?
Structural flexibility of enzyme and DNA molecules
41
Bacteria have characteristics amenable to the study of spontaneous mutation, including haploidy, a highly studied and characterized genome, and what other feature?
Short generation time
42
What characteristic of microbes causes mutation to display a large influence within bacterial populations?
Low generation time
43
What type of mutation is a single nucleotide substitution that causes a change in the codon, resulting in production of a different amino acid?
Missense
44
What type of mutation is a change in codon specifying a premature termination codon?
Nonsense
45
Which of the following terms refers to bacteria's ability to take up DNA from the environment?
Transformation
46
What is the term for the transfer of genetic information from a donor cell to a recipient within close proximity that may use a plasmid?
Conjugation
47
Transposition of mobile genetic elements includes insertion sequences (IS), transposons, and specific bacterial viruses. Each involves unique mechanisms for transposition. DNA rearrangements, such as inversion, deletion, fusion, and amplification, are potential outcomes of transposition. Transposases are enzymes encoded by the mobile elements that mediate what action?
Change in location of genetic material
48
What is the term for the transmission of genetic material between organisms by means of bacteriophage gene vectors?
Transduction
49
Restriction modification systems are traditionally considered a barrier to gene acquisition through their function of screening and cleaving fragments of foreign DNA. Why might this system contrarily promote gene acquisition?
Recombinogenic capability of fragmented DNA before degradation
50
Transposable elements have the ability to embed genetic traits of a donor genome onto a natural vector and the ability to impose a stable association between the recipient genome and the transferred genes. This capacity for horizontal transmission of spontaneously acquired genes has led to what biomedical issue?
Antibiotic resistance
51
What is the process by which bacteriophage DNA is integrated into a host chromosome and potentially encodes toxins and other virulence factors?
Transduction
52
Plasmids that encode for machinery employed in transfer by means of sex pilus use what to transfer genetic information?
Conjugation
53
What is involved in genes conferring resistance to antimicrobial agents?
R plasmid
54
Mannitol salt agar is used to culture which of the following microorganisms?
Streptococcus agalactiae
55
Which of the following antibiotics is used to treat methicillin-resistant Staphylococcus aureus (MRSA)?
Vancomycin
56
What species of staphylococcus commonly causes surgical wound infections of the skin?
Aureus
57
Scalded skin syndrome is caused by Staphylococcus aureus. What is the mechanism of the disease progression?
Release of protease
58
What is the most critical factor in the spread of nosocomial infections involving Staphylococcus aureus?
Patients in a hospital setting have compromised biological defenses, either immunosuppressed or with new portals of entry
59
Rheumatic fever is a post-streptococcal disease caused by an immunologic response to the initial infection. It may lead to migratory polyarthritis and carditis. How long after an initial infection do the symptoms of rheumatic fever appear?
2-3 weeks
60
What is the standard recommended treatment in the United States for a patient undergoing secondary prevention for rheumatic fever once group A streptococcal pharyngitis is confirmed?
Benzathine penicillin once a month for several years
61
Which of the following microbes is the most common cause of subacute endocarditis in individuals?
Viridans group streptococcus
62
What is the site of action of beta-lactam antibiotics against Gram-positive organisms?
Bacterial cell wall
63
A 5-year-old girl presents with sore throat, runny nose, and itchy eyes. Patient has no fever, but a rapid strep test is negative. A throat culture is sent into the lab. The patient is sent home and advised to return if there is fever or worsening symptoms. Gram stain shows a Gram-positive coccus in chains. In the following days, the culture shows alpha hemolysis, is green in color, and has small gray colonies.
What is the most likely organism?
Streptococcus viridans
64
How does Streptococcus viridans appear on a Gram stain?
Gram-positive cocci in chains
65
What is the name of the manifestation where a patient's immune response during infection with Streptococcus pyogenes produces antibodies that react with host sarcolemma, myosin, and synovium?
Acute rheumatic fever
66
What basic bacterial shape is the bacterium Bacillus anthracis?
Rod
67
Which of the following bacteria is the first microorganism linked to a specific disease?
Bacillus anthracis
68
Which of the following microorganisms is considered an obligate anaerobe?
Clostridium tetani
69
What does the slow progression of healing of cutaneous anthrax generally lead to?
Limited systemic symptoms
70
A patient presenting with cyanosis, hemorrhagic mediastinitis, and meningitis is proposed to have been exposed to Bacillus anthracis endospores (anthrax). What is the most likely route of transmission?
Inhalation of aerosolized endospores
71
What is a likely route of transmission of anthrax to humans?
Contact with contaminated bone meal fertilizer
72
What is a likely cause of death due to presence of bubonic plague?
Endotoxic shock
73
What has a similar pathology to Pseudomonas aeruginosa and generally causes infections of burns, wounds, and lungs?
Burkholderia cepacia
74
Neisseria gonorrhoeae manifestations include genital gonorrhoeae and what other local infection?
Pharyngeal infection
75
What is the final step of initial Y. pestis infection for humans?
Flea bites, then it regurgitates Y. pestis into new host
76
What basic shape is the Gram-negative bacterium Vibrio cholerae?
Comma
77
Bordetella pertussis is a Gram-negative bacteria that causes whooping cough, also called 100-day cough. What is the most sensitive diagnostic test for the confirmation of whooping cough?
Polymerase chain reaction (PCR)
78
Which of the following is the most common causative agent of urinary tract infection (UTI) in women?
Escherichia coli
79
Diabetes is a known metabolic disease that causes a chronic decrease in the number of neutrophils. Which of the following bacteria causes a classic green-colored infection on the skin of an amputated part in people with diabetes?
Pseudomonas aeruginosa
80
What reservoir is associated with the majority of cases of opportunistic Escherichia coli infection where infection may progress from cystitis to pyelonephritis?
Host intestinal microbiota
81
What manifestation of Neisseria gonorrhea can cause infertility and ectopic pregnancy?
Pelvic inflammatory disease
82
Between levofloxacin and doxycycline, which antibiotic would be most effective against Legionella and why?
Levofloxacin because it is a fluoroquinolone
83
What is the most likely route of transmission of bubonic plague?
Flea bite
84
Bloody diarrhea and hemolytic uremic syndrome (HUS) are manifestations of what type of Escherichia coli infection?
Enterohemorrhagic
85
Due to antimicrobial resistance, what does treatment of Neisseria gonorrhoeae often involve?
Third-generation cephalosporins
86
A high number of HIV-associated pneumonia patients in Colombia were found to be co-infected with Legionella bacteria, and these patients suffered a high mortality rate. Patients were often underdiagnosed because their cultures were negative, but quantitative polymerase chain reactions (PCR) showed that they were infected. What explains these findings?
Legionella is notoriously difficult to culture and is often diagnosed with PCR
87
The bacterium Treponema pallidum appears in a helical corkscrew shape. How is it classified?
Spirochete
88
Tuberculosis is a disease prevalent in the poor socioeconomic bracket of India and Pakistan, mostly due to dense population, poor healthcare, and malnutrition. The microorganism that causes TB is Mycobacterium tuberculosis (MTB). Why is this pathogen difficult to treat?
It has a thick, waxy lipid coating, which surrounds the entire bacterial cell and hides it from the human immune system
89
Which of the following STD-causing bacteria cannot grow in culture media but are easily identified with the help of dark-field microscopy?
Treponema pallidum
90
Following a camping trip, a patient exhibits symptoms of Lyme disease, contracted through a deer tick bite. What type of disease transmission is this?
Biological vector
91
Chlamydia trachomatis is generally associated with infection of what tissue?
Conjunctiva and genital
92
A 22-year-old woman presents with a maculopapular rash on her palms and soles. Physical examination reveals several enlarged non-tender lymph nodes and slight fever. She has a history of multiple sexual partners and unprotected sex.
What is the most likely diagnosis?
Secondary syphilis
93
A 60-year-old man presents with coughing, sweating, fever, fatigue, and weight loss. He reports previous diagnoses of diabetes and addiction to alcohol and nicotine. A chest X-ray indicates cavity formation within the lungs. What infection is likely to be responsible for these findings?
Reactivation tuberculosis
94
Which manifestation of Chlamydia trachomatis can be described by chronic inflammation of the eyelids and increased vascularization of the cornea with potential to cause severe corneal scarring and conjunctival deformities?
Trachoma
95
A 38-year-old man presents with difficulties walking correctly and visual disturbances. Physical examination reveals a broad-based ataxic gait and a positive Romberg sign, which is indicative of neuropathy affecting proprioception.
What is the most likely diagnosis?
Tertiary syphilis
96
A patient presents with large flattened plaques on the face and trunk with raised red edges and dry pale hairless centers. What condition is the most likely cause of infection?
Tuberculoid leprosy
97
Which manifestation of Chlamydia trachomatis infection is commonly associated with potentially permanent fertility dysfunction?
Pelvic inflammatory disease
98
Chlamydia trachomatis is categorized as an obligate intracellular bacteria due to which function of its reticulate body form?
Replication
99
A 19-year-old man presents with a firm painless ulcer on the shaft of his penis. When asked about his sexual history, the patient reports having occasional unprotected sex with his new girlfriend.
Primary syphilis
100
What term describes the transovarial spread within ticks that allows the cycle of R. rickettsii infection to perpetuate without a host?
Arthropod-sustained
101
A diagnostic test result shows a granuloma within alveoli composed of lymphocytes, macrophages, multinucleated giant cells, and other immune cells. The patient is asymptomatic. What species most likely caused the infection?
Mycobacterium tuberculosis
102
Acquired Immunodeficiency Syndrome (AIDS) is caused by which of the following types of microorganisms?
Retrovirus
103
Viruses are microorganisms that contain what?
Proteins and genetic material
104
An 8-year-old girl presents with symptoms of fever for 3 days. Her mother reports that her daughter has been tired and complaining of muscle aches. Diagnostic testing confirms the diagnosis. The mother is counseled that this sickness might have been prevented by receiving a yearly vaccine. The pathogen responsible uses what mechanism to cause disease?
Appropriation of host enzymes
105
Symptoms associated with which disease would you most expect Epstein-Barr virus (EBV) or cytomegalovirus (CMV) infection to cause in an otherwise healthy adult?
Rheumatoid arthritis
106
How is rhinovirus most frequently spread?
Hand-to-hand contact
107
An 8-year-old boy with a history of fever and non-specific symptoms presents with bright red cheeks and a macular lacy rash over his body. What virus is the most likely cause of this condition?
Parvovirus B19
108
A 9-year-old girl has had a slight fever and a sore throat for the past 2 days. She also has 5 ulcerative lesions in her mouth and 3 vesicular lesions on her left hand and right foot. What virus is most likely causing the illness?
Single-stranded (+) RNA virus Picornaviridae
109
Antiviral agents are a class of drugs used specifically for treating viral infections rather than bacterial ones. Most antivirals are used for specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Even with the development of numerous antiviral medications, viruses are often difficult to treat because of their high mutation rates and containment within the host cell for most of their lives.
A 60-year-old man with a known history of Parkinson's disease is to receive treatment for the Influenza A virus. He is given a drug that is useful against Parkinson's disease as well as for prophylaxis against influenza.
The drug given most likely has which of the following mechanisms of action?
It prevents uncoating of the virus
110
What kind of drug blocks the processing of viral proteins and prevents viral maturation?
Protease inhibitors
111
How do protease inhibitors prevent human immunodeficiency virus replication?
Preventing enzymatic cleavage of viral protein precursors into final forms
112
A 4-year-old child presents to urgent care with fever and sore throat. Physical exam reveals painful vesicular lesions around the lips and mouth. The mother first noticed the lesions yesterday when she picked the child up from daycare. The patient is treated with oral acyclovir, and the lesions ulcerate and resolve.
What describes the most likely viral pathogen?
Double-stranded DNA: enveloped
113
There is an outbreak of disease caused by a virus in Liberia, West Africa. Patients present with symptoms including vomiting of blood and bleeding from the eyes, skin, and gastrointestinal tract. The mortality rate of this disease is more than 70%, and it is transmitted by contact with blood and body fluids. What virus is the most likely cause of this disease?
Ebola virus
114
An otherwise healthy 65-year-old man was in a car accident and broke several ribs on the left side. Approximately 12 days later, he developed a painful well-circumscribed vesicular rash over the left rib cage that persisted for several weeks. What most likely caused the rash?
Reactivation of latent varicella zoster virus
115
Poliovirus and rhinovirus can be characterized as what shape?
Polyhedral
116
Rare complications of human herpesvirus 6 include encephalitis, central nervous system disorders, and what else?
Bone marrow failure
117
What agent would cause a presentation of runny nose and a "scratchy throat," with a physical examination that reveals conjunctival injection, nasal mucosal swelling, nasal congestion, and pharyngeal erythema?
Rhinovirus
118
Clinical symptoms of human immunodeficiency virus (HIV) are suppressed by what type of medication?
Antiretroviral therapy
119
A neonate is born to an HIV-positive mother who did not receive antiretroviral therapy during her pregnancy. Both mother and neonate tested positive for HIV antibodies by rapid testing. Since this infant is at risk of vertical transmission of HIV from the mother, the pediatrician decided to treat prophylactically with a reverse transcriptase inhibitor.
What is the most appropriate choice for prophylaxis?
Zidovudine
120
How is human immunodeficiency virus (HIV) diagnosis confirmed after a positive screening test?
Western blot
121
What manifestation is associated with hepatitis B infection in addition to fatigue, loss of appetite, nausea, pain, and fullness in the right upper quadrant?
Cholestasis
122
A 4-year-old boy presents with profuse watery diarrhea and signs of dehydration. What is the pathogenesis of the most likely causative agent?
Increasing fluid secretion
123
What action is associated with the highest risk of transmission of human immunodeficiency virus (HIV)?
Unprotected intercourse among males
124
Why are influenza vaccines less effective in neutralizing the virus every year even though the circulating strains are the same type as that from the previous year?
Antigenic drift
125
Bread mold (Rhizopus stolonifer) are saprobes that rapidly propagate on the surface of bread, fruits, and vegetables, living off of decaying organic material. What is the classification of this fungus?
Zygomycota
126
Aspergillus niger is a common food contaminant and is considered an imperfect fungus that does not have a sexual phase of reproduction. What type of fungus is it?
Deuteromycota
127
Club fungi, such as mushrooms and shelf fungi on tree trunks, are characterized by their club-shaped fruiting bodies. What is their classification?
Basidiomycota
128
Arbuscular mycorrhizas help plants capture nutrients (phosphorus, sulfur, nitrogen) and micronutrients from the soil. These fungi do not reproduce sexually and cannot survive without a symbiotic association with plant roots. What type of fungus are these?
Glomeromycota
129
What population is most susceptible to fungal infections?
Organ transplant recipients
130
What fungus can cause respiratory disease and is associated with birds and bats in the Mississippi and Ohio River Valleys?
Histoplasma capsulatum
131
What characteristic explains how Blastomyces dermatitidis can exist as a yeast in human tissue and a mold in the environment?
Thermally dimorphic
132
What is the primary portal of entry for Blastomyces dermatitidis?
Lungs
133
Which Candida species occur most commonly as a culprit of fungal infection?
C. glabrata
134
A 26-year-old man presents with fever of 101°F, dry cough, night sweats, fatigue, muscles aches, and decreased appetite for the past 4 days. He has a history of chronic hepatitis B. He does not take any medications, does not recall any sick contacts, and has not been to the hospital for 3 years. He traveled to the Great Lakes last month and participated in various outdoor activities. Potassium hydroxide preparation of sputum showed a round organism with a doubly refractile wall and a single broad-based bud.
What organism is the most likely cause of infection?
Blastomyces dermatitidis
135
Which of the following is the type of host wherein the virus or parasite has already attained sexual or reproductive maturity?
Primary host
136
Which of the following refers to a type of infection that is caused by pathogenic microorganisms that took advantage of the present vulnerable condition of the person?
Opportunistic infection
137
Which of the following refers to an animal that has been introduced with new genetic information acquired from foreign DNA?
Transgenic
138
Which of the following terms refers to the capacity of the pathogenic microbe to enter and spread into the tissues of the host?
Invasion
139
What is the most common portal of entry for microbes into humans?
Mucosal membranes
140
What portal of entry is part of the parenteral route of getting a disease?
Broken skin
141
What portal of entry is an external mucosal membrane?
Conjunctiva
142
What pathogen has a portal of entry through the placenta, making it a TORCH disease?
Toxoplasma gondii
143
Mosquito bites as a portal of entry are capable of transmitting some viruses, such as dengue. A mosquito that bites a dengue-infected person becomes a viral reservoir and can then transmit the virus by biting another person. What mode of transmission is at work?
Vector transmission
144
Typhi, a Salmonella enterica serovar, invades epithelial cells and subsequently secretes the A2B5 toxin. What mechanism of pathogenicity involves this release of toxin?
Injury
145
A 26-year-old female counselor presents with 2 days of profuse diarrhea and fever. She reports she recently completed a week-long course of antibiotics for an upper respiratory tract infection but takes no other medications. Stool antigen testing for Clostridium difficile toxin A/B is positive. What contributed most to her diarrheal infection?
Eradication of native gastrointestinal bacteria
146
A 30-year-old male patient on the fourth day of a course of oral antibiotics for pneumonia comes to your clinic due to diarrhea. The diarrhea is non-bloody and watery, happening 3-4 times a day. On examination, his mucous membranes are dry. Clostridioides difficile PCR laboratory examination returns positive.
What is the most likely underlying pathophysiology of this patient's diarrhea?
Disruption of normal colonic microbiome
147
What organism is commonly found in the stomach?
Streptococcus spp
148
What observation appropriately applies Koch's postulates for identifying Legionella pneumophila as the causative agent of Legionnaires' disease?
Immunosuppressed patients that are exposed to pure cultures of L. pneumophila contract an atypical pneumonia
149
According to Koch's first postulate, what defines a healthy host organism?
No presence of infectious organism
150
What approach to expressing disease prognosis identifies deaths in intervals in order to show how many patients died over a given period?
Kaplan-Meier
151
What is the transfer of genetic material from one cell to another through cell-to-cell connection?
Conjugation
152
A 51-year-old man with a history of chronic hypertension and type 2 diabetes mellitus poorly controlled with medications presents for a routine checkup. He has had no problems since his last medical checkup. His BMI is 40, and he smoked previously from age 16 to 26. You recommend he receive the pneumococcal polysaccharide vaccine.
What risk factor for severe pneumococcal infection warrants receiving the vaccine?
Diabetes mellitus
153
An 8-month-old child presents after a visit to the emergency department due to pneumonia caused by Staphylococcus aureus. This is the second episode of Staphylococcal pneumonia in this child in 2 months. You suspect a biochemical disturbance and administer antibiotics as appropriate.
What cell group is responsible for the increased Staphylococcal infections in this child?
Neutrophils
154
What virulence factor in Streptococcus pneumoniae makes the disease more severe in the host?
Encapsulation
155
Emerging infectious diseases like influenza are infections that have recently appeared within a population or have incidences that are rapidly increasing or threaten to increase in the near future. What factor contributes to the risk for an emerging outbreak related to the influenza virus?
Ability to change genetic information
156
A patient presents with loss of appetite, nausea, and persistent mucoidal liquid stools. The patient states they have recently been treated for a bacterial infection using multiple antibiotics. It can be assumed the patient is suffering from an infection from the over-colonization of what bacterial species?
Clostridium difficile
157
A 52-year-old man is diagnosed with bacterial meningitis. Cerebrospinal fluid grows out Gram-positive cocci in short chains and diplococci. You suspect Streptococcus pneumoniae meningitis. Which of the following virulence factors contributes to this organism's ability to evade host defenses?
Thick polysaccharide capsule that protects against phagocytosis
158
How does the capsule in Streptococcus pneumoniae help the organism attain increased virulence?
It prevents adhesion of the immune cell to the pathogen
159
An 8-year-old boy presents for evaluation of a sore throat and fever that he has had for 3 days. His parents report that they "do not believe in vaccines." Inspection of the pharynx reveals a thick gray membrane coating the tonsil. Gram stain reveals Gram-positive club-shaped bacilli. Toxin production by the responsible bacteria depends on the presence of what nutrient?
Iron
160
A siderophore is a molecule produced by bacteria that chelates (binds) to and facilitates uptake of iron. The iron-bound siderophore binds to transport receptors on the surface of the bacteria for transport into the cell. Iron is also essential for the host, where it is often bound to a carrier protein (such as hemoglobin or transferrin). Bacterial siderophores compete with the host for soluble iron. How can this host-pathogen tug-of-war for iron be used against the invading bacteria?
Antibiotic-siderophore conjugate
161
What pathogenic organism expresses siderophores that assist in its ability to survive in wounds?
Pseudomonas aeruginosa
162
What type of cellular transport do siderophores employ?
Secondary active transport
163
During an infection, pathogens acquire iron by the secretion of siderophores, molecules that bind with ferric iron. What siderophore-binding protein is secreted by host immune cells in response to block the reuptake of iron-loaded siderophores by the pathogen?
Lipocalin 2
164
An 8-year-old boy presents with runny nose, fever, and muscle aches. His mother reports that he has had these symptoms for the past week and they have become more severe. Rapid influenza testing is positive. After instructing the mother to provide the child with supportive care, the mother asks if the child is in danger of catching the exact same flu virus again if she sends him back to school. What is the most appropriate response?
IgM antibodies will protect him until IgG antibodies peak at 1 month
165
Which of the following is a T-dependent antigen?
Protein
166
What antibody class can be found on the membrane of a B cell?
IgM
167
Vaccines act as an artificial means of activating the immune system to protect against infection. Immunization induces B lymphocytes to produce which class of antibodies?
IgG
168
What type of antibody penetrates easily into tissue spaces and is the only antibody that can cross the placental barrier, offering passive immunity to the developing fetus?
IgG
169
Antibodies present in the mucosa of the respiratory, genitourinary, and gastrointestinal tracts are a crucial first line of defense against infection by triggering inflammation. What isotype are these antibodies?
IgA
170
The word antigen comes from a combination of the words "antibody" and "generator." An antigen is anything that activates the adaptive immune response. The part of the antigen that the immune system recognizes is called the epitope, a small fragment of the total antigen. How else do epitopes relate to antigens?
Antigens can have epitopes for B cells and T cells
171
What type of antibody is secreted and binds to the antigen to prevent it from attaching to mucosal epithelial cells?
IgA
172
What part of the antibody binds specifically to the antigen when it participates in the antigen-antibody interaction?
Variable region
173
What antigen-antibody interaction involves binding pathogens together, making the pathogens easier to phagocytize?
Agglutination
174
Antibodies have a structure of two heavy chains and two light chains joined to form a Y-shaped protein. How can the heavy and light chains of an antibody be separated chemically?
Reducing agent
175
B cells constitute humoral immunity and mature in the bone marrow. What is their role?
Produce antibodies to defend against pathogens in an extracellular environment
176
Adaptive immunity consists of humoral immunity and cell-mediated immunity. Which attribute is specifically characteristic of humoral immunity?
Acts against extracellular microbes and related toxins
177
Defensins and bacteriocins are types of what?
Antimicrobial peptides
178
Antigen-presenting cells present foreign protein fragments (peptides) to the T cells of the adaptive immune system. This antigen presentation activates T cells to take action against the foreign molecule. The macrophage is one type of antigen-presenting cell that phagocytoses pathogens and presents the peptides bound to MHC I molecules. What is a part of the mechanism for macrophage antigen presentation?
The macrophage engulfs a pathogen, then degrades it into fragments that are presented
179
Where is IgA primarily located in the human body?
Mucous membranes
180
What extracellular serum substances work with complement to break down red blood cells?
Hemolysins
181
There are two categories of antigen-presenting cells (APC): professional and nonprofessional cells. What type of professional cells has the broadest range of antigen presentation, presenting to both helper and cytotoxic T cells?
Dendritic cells
182
What is the purpose of antigen presentation in professional antigen-presenting cells?
Activate T cells
183
What kind of vaccine exposes an individual to a weakened strain of a pathogen to establish a subclinical infection to activate the adaptive immune system?
Live attenuated vaccines
184
The human immune system consists of 2 major subsets: the innate immune system and the adaptive immune system. Which of the following applies to adaptive immunity but not innate immunity?
Consists of both humoral and cell-mediated immunity
185
Both branches of adaptive immunity (humoral and cellular response) involve specialized cells with a diverse array of specified receptors. What is exclusive to B-cell mediated humoral immunity?
Secreted receptors that recognize pathogenic epitopes
186
Humoral immunity is mediated by B cells. Cellular immunity is mediated by T cells. The two branches of adaptive immunity have much in common. What quality is unique to T cells?
Major histocompatibility complexes required for antigen presentation
187
What type of T cell releases lymphokines and stimulates the production of antibodies against a pathogen?
Helper T cells
188
What type of T cell exerts an immunosuppressive effect, slowing down the body's defenses?
Regulatory T cells
189
Which cell in the adaptive immune system is most associated with killing large numbers of infected cells or cancerous cells?
Cytotoxic T cells
190
What activated T helper cell stimulates neutrophils and is central to the destruction of extracellular bacteria and fungal pathogens?
Th17
191
Why is it difficult to develop vaccines against rhinovirus (common cold)?
There are too many viral subtypes, making design of vaccines difficult
192
Antiviral agents are a class of drugs used specifically for treating viral infections rather than bacterial ones. Most antivirals are used for specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Even with the development of numerous antiviral medications, viruses are often difficult to treat because of their high mutation rates and containment within the host cell for most of their lives. A 60-year-old man with a known history of Parkinson's disease is to receive treatment for the Influenza A virus. He is given a drug that is useful against Parkinson's disease as well as for prophylaxis against influenza. The drug given most likely has which of the following mechanisms of action?
It prevents uncoating of the virus
193
A siderophore is a molecule produced by bacteria that chelates (binds) to and facilitates uptake of iron. The iron-bound siderophore binds to transport receptors on the surface of the bacteria for transport into the cell. Iron is also essential for the host, where it is often bound to a carrier protein (such as hemoglobin or transferrin). Bacterial siderophores compete with the host for soluble iron. How can this host-pathogen tug-of-war for iron be used against the invading bacteria?
Antibiotic-siderophore conjugate
194
What has a similar pathology to Pseudomonas aeruginosa and generally causes infections of burns, wounds, and lungs?
Burkholderia cepacia
195
Which of the following microorganisms is associated with the ingestion of inappropriately cooked pork?
Trichinella spiralis
196
An unknown bacteria was inoculated onto Mannitol salt agar. After a 24-hour incubation period, growth occurred and the red media turned yellow. To what species does this sample most likely belong?
Staphylococcus aureus
197
Parasites (organisms that live on or in a host) gain nutrients at the expense of the host, and certain species can cause a significant burden of disease in tropic/subtropic regions and temperate climates. What parasitic disease causes the most deaths globally?
Malaria
198
A 4-year-old child presents to urgent care with fever and sore throat. Physical exam revels painful vesicular lesions around the lips and mouth. The mother first noticed the lesions yesterday when she picked the child up from daycare. The patient is treated with oral acyclovir, and the lesions ulcerate and resolve. What describes the most likely viral pathogen?
Double-stranded DNA: enveloped
199
Through which route does tapeworm infection occur?
Ingestion of contaminated food
200
A 13-year-old boy presents in the ED with fever, tender joints, and rapid heartbeat. His mother says he has been sick with a sore throat, which she thought was a cold; now she is concerned it may actually be the flu. Rapid strep test and flu test in the ED are both negative. The physician assistant finds a rash with pink rings and a clear center, orders an Antistreptolysin O antibody test and EKG, and gives the patient penicillin and a round of steroids. The lab test shows a high level of antibodies against Streptococcus. What organism is the most likely pathogen?
Streptococcus pyogenes
201
What is an FDA-approved medical application of a product derived from Clostridium botulinum?
Paralytic to improve muscle spasm associated with neurological condition
202
A 38-year-old man presents with difficulties walking correctly and visual disturbances. Physical examination reveals a broad-based ataxic gait and a positive Romberg sign, which is indicative of neuropathy affecting proprioception. What is the most likely diagnosis?
Tertiary syphilis
203
A 4-year-old boy presents with profuse watery diarrhea and signs of dehydration. What is the pathogenesis of the most likely causative agent?
Increasing fluid secretion
204
A 26-year-old man presents with fever of 101, dry cough, night sweats, fatigue, muscle aches, and decreased appetite for the past 4 days. He has a history of chronic hepatitis B. He does not take any medications, does not recall any sick contacts, and has not been to the hospital for 3 years. He traveled to the Great Lakes last month and participated in various outdoor activities. Potassium hydroxide preparation of sputum showed a round organism with a doubly refractile wall and a single broad-based bud. What organism is the most likely cause of infection?
Blastomyces dermatitidis
205
A non-compliant HIV-positive male patient has been reporting a stiff neck and a severe headache. The headache has initially lessened by analgesics, but the analgesics are no longer effective. His current CD4+ count is 180/mm^3. He is not on any prophylactic drugs. What is the most likely causative agent?
Cryptococcus neoformans
206
A patient presents with loss of appetite, nausea, and persistent mucoidal liquid stools. The patient states they have recently been treated for a bacterial infection using multiple antibiotics. It can be assumed the patient is suffering from an infection from the over-colonization of what bacterial species?
Clostridioides difficile
207
A 29-year-old woman in her second trimester of pregnancy presents to the clinic with vaginal discharge. She reports 2 days of gray-white discharge and a fishy odor. She denies vaginal pruritus or dysuria, but exam reveals mild vulvar irritation. What would be the most appropriate treatment for this patient?
Metronidazole
208
A 26-year-old female counselor presents with 2 days of profuse diarrhea and fever. She reports she recently completed a week-long course of antibiotics for an upper respiratory tract infection but takes no other medications. Stool antigen testing for Clostridioides difficile toxin A/B is positive. What contributed most to her diarrheal infection?
Eradication of native gastrointestinal bacteria
209
What type of progression of human immunodeficiency virus (HIV) is the most rapid and is seen in untreated patients?
Expedient
210
Which of the below pathogens appear to share virulence characteristics with enteroinvasive Escherichia coli suggestive of a shared intermediate between the organism and E. coli?
Shigella
211
"During the domestication of soybean, the size and weight of seeds have been enhanced by human selection...although an increased photosynthetic capacity could have provided more carbon, we hypothesize that the capacity of Biological Nitrogen Fixation (which occurs in a special organ within the seed) was also enhanced during the domestication of soybean." According to the statement, what effect has human selection had on the internal stores of carbon and nitrogen within soybean seeds?
Stores of carbon did not increase and nitrogen did not increase
212
Why might a patient with Capnocytophaga infection need urgent cardiac surgery?
Endocarditis
213
Pseudomonas aeruginosa is a difficulty nosocomial infection to control due to the nature of the bacteria's glycocalyx. Which type of glycocalyx does this Pseudomonas have?
Capsule
214
A 6-month-old male infant who has suffered from frequent infections caused by Neisseria meningitidis is found to have a deficiency in complement components C6 and C7. What component of innate immunity depends on the presence of C6 and C7?
Forming the complement membrane attack complex
215
What is the most likely source of infection with hepatitis B virus?
Asymptomatic carrier
216
What is the most critical factor in the spread of nosocomial infections involving Staphylococcus aureus?
Patients may be immuno-suppressed or have new portals of entry
217
What agent would show efficacy against methicillin-resistant Staphylococcus aureus (MRSA)?
Vancomycin (Vancocin)
218
What is the transfer of genetic material from one cell to another through cell-to-cell connections?
Conjugation
219
What is the most suitable habitat for the dermatophytes that cause dermatophytosis?
A burgeoning tropical city
220
Which of the following examples of gene editing is prohibited in the United States?
Gene for Tay-Sachs disease in the pluripotent stem cells of an embryo
221
There is an outbreak of disease caused by a virus in Liberia, West Africa. Patients present with symptoms including vomiting of blood and bleeding from the eyes, skin, and gastrointestinal tract. The mortality rate of this disease is more than 70% and it is transmitted by contact with blood and body fluids. What virus is the most likely cause of this disease?
Ebola virus
222
A 17-year-old boy presents to urgent care with 2 days of dysuria and urethral discharge. What organism is most likely responsible for this patient's symptoms?
Neisseria gonorrhoeae
223
Symptoms associated with scalded skin syndrome are primarily caused by which of the following?
Bacterial release of toxin
224
Some bacteria have evolved mechanisms to transverse the mucus layer of the intestines to reach epithelial cells. Which of the following is an expected adaptation for this mechanism of infection?
Resistance to antimicrobial compounds
225
The Gram-negative bacterium Neisseria gonorrhoeae, often arranged in pairs, has a round shape. How is it classified?
Coccus
226
A 65-year-old man presents to the emergency department after 1 day of fevers and chills. He has been in his usual state of health apart from a cough for the last 2 weeks. Bronchial breath sounds and dullness to percussion in the right lower lung field are noted on exam. Chest radiograph reveals lobar consolidation.
What would be shown by a Gram stain of the organism most likely responsible for this patient's presentation?
Gram-positive diplococci
227
A 51-year-old man with a history of chronic hypertension and type 2 diabetes mellitus poorly controlled with medications presents with nasal discharge, sinus congestion, and headaches. His BMI is 40, and he smoked previously from age 16 to 26. During physical examination, you note mild ptosis, proptosis, and necrotic black lesions on his nasal turbinates. Treatment is initiated immediately.
What fungal species do you expect to see on culture?
Rhizopus
228
An otherwise healthy 65-year-old man was in a car accident and broke several ribs on the left side. Approximately 12 days later, he developed a painful well-circumscribed vesicular rash over the left rib cage that persisted for several weeks. What most likely caused the rash?
Reactivation of latent varicella zoster virus
229
A patient presents with large flattened plaques on the face and trunk with raised red edges and dry pale hairless centers. What condition is the most likely cause of infection?
Tuberculoid leprosy
230
Aerodigestive trematodiasis is contracted through which mechanism?
Consumption of freshwater plants contaminated with infected feces
231
A 32-year-old man presents with fever, headache, dry cough, and myalgias for the past 2 days. The patient denies having his seasonal vaccine this year.
What virus type is probably causative of the patient's symptoms?
Enveloped single-stranded RNA virus
232
Viruses are microorganisms that contain what?
Proteins and genetic material
233
A 51-year-old man with a history of chronic hypertension and type 2 diabetes mellitus poorly controlled with medications presents for a routine checkup. He has had no problems since his last medical checkup. His BMI is 40, and he smoked previously from age 16 to 26. You recommend he receive the pneumococcal polysaccharide vaccine.
What risk factor for severe pneumococcal infection warrants receiving the vaccine?
Diabetes mellitus
234
Arbuscular mycorrhizas help plants capture nutrients (phosphorus, sulfur, nitrogen) and micronutrients from the soil. These fungi do not reproduce sexually and cannot survive without a symbiotic association with plant roots. What type of fungus are these?
Glomeromycota
235
What is the most compelling presentation to administer treatment for R. ricketsii infection?
History of tick bite
236
A 40-year-old man presents to the emergency department after being rescued from an apartment fire. The patient is currently sedated and intubated. Oxygen saturation is 96% at room air. He exhibits burns on 70% of his body surface. 3 days later, he develops green film over the burn wounds on his arms. The nurse notes a smell in the room and asks you about the possibility of diabetic ketoacidosis. You decide to take a sample of the green film to the laboratory for culture, sensitivity, and microbial examination and start the patient on empiric antibiotic therapy.
What antibiotic is the best option?
Aztreonam + gentamicin
237
Histoplasma capsulatum, the causative agent of histoplasmosis, can be contracted in specific environments, including caves. Why are caves considered at-risk areas for this fungus?
This fungus is transmitted by bat droppings
238
What cellular structure is considered as the "powerhouse of the cell"?
Mitochondrion
239
Protein A, made by Staphylococcus aureus, has high affinity to the heavy chain of the constant region of most IgG molecules. Which part of IgG molecules does Protein A bind with the highest affinity?
Fc
