1.
Substances that are naturally produced by certain microorganisms that can inhibit or destroy other microorganisms are called
Correct Answer
A. Antibiotics
Explanation
Antibiotics are substances that are naturally produced by certain microorganisms and have the ability to inhibit or destroy other microorganisms. They are specifically designed to target and kill bacteria, fungi, or parasites. Antibiotics play a crucial role in treating bacterial infections and have been a significant advancement in medical science. They are different from other drugs such as narrow-spectrum drugs, semisynthetic drugs, and synthetic drugs, which may have different mechanisms of action or target a broader range of microorganisms.
2.
Antimicrobics effective against a wide variety of microbial types are termed
Correct Answer
E. Broad-spectrum drugs
Explanation
Broad-spectrum drugs are antimicrobics that are effective against a wide variety of microbial types. This means that they can target and kill a broad range of bacteria, viruses, fungi, and other microorganisms. Unlike narrow-spectrum drugs, which are only effective against specific types of microorganisms, broad-spectrum drugs have a wider range of activity. This makes them useful in treating infections when the specific type of microorganism causing the infection is unknown or when multiple types of microorganisms are involved.
3.
Important characteristics of antimicrobic drugs include
Correct Answer
E. All of the choices are correct
Explanation
This answer is correct because all of the listed characteristics are important for antimicrobial drugs. Low toxicity for human tissues is important to ensure that the drug does not harm the patient while treating the infection. High toxicity against microbial cells is important to effectively eliminate the microorganisms causing the infection. Not causing serious side effects in humans is important for the overall well-being of the patient. Finally, being stable and soluble in body tissues and fluids is important for the drug to be effectively distributed and exert its antimicrobial effects. Therefore, all of these characteristics are important for antimicrobial drugs.
4.
Aminoglycosides
Correct Answer
C. Attach to the 30S ribosomal subunit and disrupt protein synthesis
Explanation
Aminoglycosides are a class of antibiotics that attach to the 30S ribosomal subunit in bacteria. This binding interferes with the process of protein synthesis, disrupting the production of essential proteins needed for bacterial growth and survival. As a result, the bacteria are unable to function properly and eventually die. This mechanism of action makes aminoglycosides effective against a wide range of bacterial infections.
5.
A chemical that inhibits beta-lactamase enzymes is
Correct Answer
D. Clavulanic acid
Explanation
Clavulanic acid is a chemical that inhibits beta-lactamase enzymes. Beta-lactamase enzymes are responsible for breaking down and inactivating beta-lactam antibiotics, such as penicillin. By inhibiting these enzymes, clavulanic acid helps to extend the effectiveness of beta-lactam antibiotics, allowing them to effectively kill bacteria. Synercid, penicillinase, aztreonam, and imipenem are not known for their ability to inhibit beta-lactamase enzymes.
6.
Antibiotics are derived from all the following except
Correct Answer
C. Staphylococcus
Explanation
Staphylococcus is a genus of bacteria and is not a source of antibiotics. Antibiotics are commonly derived from microorganisms such as Penicillium, Bacillus, Streptomyces, and Cephalosporium. These microorganisms produce substances that have the ability to inhibit the growth of or kill other microorganisms, making them valuable in the treatment of bacterial infections.
7.
Penicillins and cephalosporins
Correct Answer
E. Block the peptidases that cross-link glycan molecules
Explanation
Penicillins and cephalosporins block the peptidases that cross-link glycan molecules. This means that they inhibit the enzymes responsible for linking the glycan chains in the bacterial cell wall. By blocking this process, these antibiotics weaken the cell wall structure, making it easier for the immune system or other antibiotics to destroy the bacteria. This mechanism of action is specific to these types of antibiotics and is one of the reasons why they are effective against certain bacterial infections.
8.
Sulfonamides
Correct Answer
B. Are metabolic analogs of PABA and block folic acid synthesis
Explanation
Sulfonamides are metabolic analogs of PABA (para-aminobenzoic acid) and they block folic acid synthesis. Folic acid is essential for the synthesis of DNA, RNA, and proteins in bacteria. Sulfonamides inhibit the enzyme dihydropteroate synthase, which is involved in the production of folic acid. By blocking this enzyme, sulfonamides prevent the bacteria from synthesizing folic acid, leading to the inhibition of DNA, RNA, and protein production. This ultimately disrupts the growth and multiplication of bacteria, making sulfonamides effective in treating bacterial infections.
9.
Ampicillin, amoxicillin, mezlocillin, and penicillin G all have
Correct Answer
A. A beta-lactam ring
Explanation
All of the given options are correct. Ampicillin, amoxicillin, mezlocillin, and penicillin G all have a beta-lactam ring, which is a key structural feature of the penicillin class of antibiotics. This ring is responsible for the antibacterial activity of these drugs. Additionally, these antibiotics have resistance to the action of penicillinase, an enzyme produced by some bacteria that can inactivate penicillin. They also have a semisynthetic nature, meaning they are derived from natural penicillin but have been chemically modified to improve their properties. Finally, these antibiotics have an expanded spectrum of activity, meaning they are effective against a wider range of bacteria compared to natural penicillin.
10.
The drug used against intestinal anaerobic bacteria, that can also alter normal flora causing antibiotic-associated colitis is
Correct Answer
B. Clindamycin
Explanation
Clindamycin is the correct answer because it is a drug commonly used to treat infections caused by anaerobic bacteria in the intestines. However, it can also disrupt the normal balance of bacteria in the gut, leading to antibiotic-associated colitis. Chloramphenicol, ciprofloxacin, bacitracin, and gentamicin are not typically associated with causing antibiotic-associated colitis.
11.
The antifungal drug that can be used to treat serious systemic fungal infections is
Correct Answer
C. Amphotericin B
Explanation
Amphotericin B is an antifungal drug that is commonly used to treat serious systemic fungal infections. It is effective against a wide range of fungal pathogens and is particularly useful for treating infections that have spread throughout the body. Amphotericin B works by binding to the fungal cell membrane, causing it to become leaky and ultimately leading to the death of the fungus. It is considered a first-line treatment for severe fungal infections and is often used when other antifungal medications have failed or are not effective.
12.
The drug used for several protozoan infections is
Correct Answer
E. Metronidazole
Explanation
Metronidazole is a drug commonly used to treat several protozoan infections such as trichomoniasis, giardiasis, and amebiasis. It works by disrupting the DNA of the protozoa, leading to their death. Nystatin is primarily used to treat fungal infections, while griseofulvin is specifically used for fungal infections of the skin and nails. Amphotericin B is an antifungal medication used for serious systemic fungal infections. Sulfa drugs, on the other hand, are antibiotics used to treat bacterial infections. Therefore, among the given options, metronidazole is the correct drug choice for several protozoan infections.
13.
Mebendazole, niclosamide, and ivermectin are drugs used to treat __________ infections.
Correct Answer
D. Helminthic
Explanation
Mebendazole, niclosamide, and ivermectin are all drugs that are commonly used to treat helminthic infections. Helminthic infections are caused by parasitic worms, such as tapeworms, roundworms, and hookworms. These drugs work by targeting and killing the worms, helping to eliminate the infection. They are not effective against bacterial, fungal, protozoan, or viral infections, which are caused by different types of microorganisms. Therefore, the correct answer is helminthic.
14.
Which of the following is not a mode of action of antivirals?
Correct Answer
E. Bond to ergosterol in the cell membrane
Explanation
Antivirals are medications used to treat viral infections by targeting specific steps in the viral replication cycle. The modes of action of antivirals include blocking penetration of the virus into host cells, blocking transcription and translation of viral genetic material, inhibiting DNA synthesis, and blocking viral maturation. However, bonding to ergosterol in the cell membrane is not a mode of action of antivirals. Ergosterol is a component of fungal cell membranes, not viral cell membranes, and therefore this action would not be effective against viruses.
15.
Antivirals that target reverse transcriptase would be used to treat
Correct Answer
B. HIV
Explanation
Antivirals that target reverse transcriptase would be used to treat HIV. Reverse transcriptase is an enzyme that is essential for the replication of HIV, as it converts the viral RNA into DNA. By targeting reverse transcriptase, antiviral drugs can inhibit the replication of the virus and help control the progression of HIV infection. This approach is specific to HIV and not applicable to other viruses such as influenza A, herpes zoster, respiratory syncytial, or hepatitis C.
16.
The cellular basis for bacterial resistance to antimicrobics include
Correct Answer
E. All of the choices are correct
Explanation
The cellular basis for bacterial resistance to antimicrobics includes several mechanisms. Bacterial chromosomal mutations can lead to changes in the bacteria's genetic material, allowing them to develop resistance to antimicrobics. Synthesis of enzymes that alter drug structure can also occur, rendering the antimicrobics ineffective. Prevention of drug entry into the cell is another mechanism, where the bacteria can develop barriers to block the entry of antimicrobics. Lastly, alteration of drug receptors on cell targets can occur, making the antimicrobics unable to bind and exert their effects. Therefore, all of the choices mentioned in the question are correct explanations for bacterial resistance to antimicrobics.
17.
A superinfection results from
Correct Answer
D. Decrease in most normal flora with overgrowth of an unaffected species
Explanation
A superinfection occurs when there is a decrease in the normal flora (beneficial bacteria) in the body, allowing an unaffected species of bacteria or fungi to overgrow and cause an infection. This can happen due to various factors such as the use of antibiotics that kill off the normal flora, allowing opportunistic pathogens to thrive. It can also occur when the immune system is weakened, making it easier for harmful microorganisms to establish an infection. In summary, a superinfection is the result of a decrease in normal flora and the subsequent overgrowth of a different species.
18.
Drug susceptibility testing
Correct Answer
B. Determines the pathogen's response to various antimicrobics
Explanation
Drug susceptibility testing is a laboratory technique used to determine the effectiveness of different antimicrobial drugs against a specific pathogen. It helps in identifying which drugs are most likely to inhibit the growth of the pathogen and therefore guide the selection of appropriate treatment. By testing the pathogen's response to various antimicrobics, healthcare professionals can choose the most effective drug and avoid the use of ineffective or potentially harmful medications. This testing is crucial in preventing the development of drug resistance and improving patient outcomes.
19.
A "shotgun" approach to antimicrobial therapy involves
Correct Answer
D. Using a broad spectrum drug so that the chance of killing the pathogen is greater
Explanation
The correct answer is using a broad spectrum drug so that the chance of killing the pathogen is greater. A "shotgun" approach to antimicrobial therapy refers to using a broad spectrum drug that targets a wide range of pathogens. This approach is used when the specific pathogen causing the infection is unknown or when there is a high likelihood of multiple pathogens being involved. By using a broad spectrum drug, there is a greater chance of killing the pathogen responsible for the infection, regardless of its identity.
20.
All of the following could be reasons why antimicrobic treatment fails except
Correct Answer
D. A disk diffusion test showing pathogen sensitivity to the antimicrobic
21.
All infectious diseases
Correct Answer
C. Are caused by microorganisms or their products
Explanation
Infectious diseases are caused by microorganisms or their products. This includes bacteria, viruses, fungi, and parasites. These microorganisms can enter the body through various means such as inhalation, ingestion, or direct contact with an infected individual or contaminated surfaces. They then multiply and spread within the body, causing illness and symptoms. Examples of infectious diseases caused by microorganisms include influenza, tuberculosis, and malaria. Understanding the cause of infectious diseases is crucial in developing effective prevention and treatment strategies.
22.
Endogenous infectious agents arise from microbes that are
Correct Answer
B. The patient's own normal flora
Explanation
Endogenous infectious agents arise from microbes that are part of the patient's own normal flora. This means that the microbes causing the infection are already present in the patient's body, typically in a balanced state without causing harm. However, certain factors such as a weakened immune system or disruption of the normal flora can lead to these microbes overgrowing and causing an infection. In such cases, the infection is considered endogenous as it originates from within the patient's own body.
23.
The human body typically begins to be colonized by its normal flora
Correct Answer
B. During, and immediately after birth
Explanation
During and immediately after birth, the human body begins to be colonized by its normal flora. This is because during the birthing process, the baby comes into contact with the mother's vaginal and fecal flora, which establishes the initial colonization. Additionally, after birth, the baby is exposed to various microorganisms in the environment, such as those present on the skin, in the air, and in breast milk. These microorganisms further contribute to the colonization of the body by the normal flora.
24.
All of the following genera are considered resident flora of skin sites except
Correct Answer
A. Escherichia
Explanation
Escherichia is not considered a resident flora of skin sites because it is a Gram-negative bacterium commonly found in the intestinal tract of humans and animals. It is not typically found on the skin surface. Staphylococcus, Corynebacterium, Micrococcus, and Mycobacterium are all examples of bacteria that are commonly found on the skin and are considered part of the resident flora.
25.
Resident flora of the intestines include
Correct Answer
B. Bacteroides
Explanation
The correct answer is Bacteroides. Bacteroides is a type of bacteria that is part of the normal flora in the intestines. It is a gram-negative anaerobe and plays a role in the breakdown of complex carbohydrates in the gut. Bacteroides also helps to maintain the balance of the intestinal microbiota and contributes to overall gut health.
26.
STORCH is an acronym that represents the most common
Correct Answer
E. Infections of the fetus and neonate
Explanation
STORCH is an acronym used in medicine to represent the most common infections that can affect the fetus and neonate. Each letter in the acronym stands for a specific infection: S for syphilis, T for toxoplasmosis, O for other infections (such as hepatitis B, HIV, or varicella-zoster virus), R for rubella, C for cytomegalovirus, and H for herpes simplex virus. These infections can be transmitted from the mother to the baby during pregnancy or childbirth and can lead to serious health issues for the newborn.
27.
The time from when pathogen first enters the body and begins to multiply, until symptoms first appear is the
Correct Answer
C. Incubation period
Explanation
The incubation period refers to the time between when a pathogen enters the body and starts multiplying, until the first symptoms of the infection appear. During this stage, the pathogen is replicating and spreading throughout the body, but the individual may not experience any noticeable symptoms. It is an important period as it allows the pathogen to establish itself and reach a sufficient level of infection before symptoms arise. This period can vary depending on the specific pathogen and the individual's immune response.
28.
The subjective evidence of disease sensed by the patient is termed
Correct Answer
B. Symptom
Explanation
A symptom refers to the subjective evidence of a disease that is sensed by the patient. It is something that the patient experiences and reports, such as pain, fatigue, or nausea. Unlike signs, which are objective and can be observed by others, symptoms are unique to the individual experiencing them. Therefore, the correct answer is symptom.
29.
The objective, measurable evidence of disease evaluated by an observer is termed
Correct Answer
C. Sign
Explanation
The given question is asking for the term used to describe the objective, measurable evidence of a disease that is evaluated by an observer. This term is called a sign. Unlike symptoms, which are subjective experiences reported by the patient, signs can be observed and measured by a healthcare professional. Pathology refers to the study of diseases, while inflammation is a specific response of the body to injury or infection. Therefore, the correct answer is sign.
30.
The study of the frequency and distribution of a disease in a defined population is
Correct Answer
E. Epidemiology
Explanation
Epidemiology is the study of the frequency and distribution of diseases in a defined population. It focuses on understanding the patterns and causes of diseases, as well as developing strategies for prevention and control. This field involves collecting and analyzing data to identify risk factors, determine the impact of diseases on different populations, and evaluate the effectiveness of interventions. Epidemiologists play a crucial role in public health by helping to inform policies and practices aimed at improving the health of communities.
31.
Someone who inconspicuously harbors a pathogen and spreads it to others is a
Correct Answer
B. Carrier
Explanation
A carrier is someone who inconspicuously harbors a pathogen and spreads it to others. They may not show any symptoms of the disease themselves but can still transmit it to others. Carriers play a significant role in the spread of infectious diseases as they can unknowingly infect a large number of people.
32.
An animal, such as an arthropod, that transmits a pathogen from one host to another is a
Correct Answer
C. Vector
Explanation
A vector is an animal, such as an arthropod, that transmits a pathogen from one host to another. Unlike a carrier, which may harbor the pathogen without transmitting it, a vector actively transfers the pathogen. A fomite refers to an inanimate object that can carry and transmit the pathogen. A reservoir is a host that carries the pathogen without showing symptoms, while a source is the origin of the pathogen.
33.
An inanimate object that harbors and transmits a pathogen is a
Correct Answer
A. Fomite
Explanation
A fomite is an inanimate object that can harbor and transmit a pathogen. It serves as a surface on which the pathogen can survive and be transferred to others. Unlike a carrier, which refers to a living organism that can carry and transmit a pathogen, a fomite does not have the ability to reproduce or sustain the pathogen within itself. Similarly, a vector refers to a living organism that can transmit a pathogen to other organisms. A reservoir refers to a natural habitat or host where the pathogen can persist and reproduce. Therefore, the correct answer is fomite.
34.
Nosocomial infections involve all the following except
Correct Answer
A. They are only transmitted by medical personnel
Explanation
Nosocomial infections are infections that are acquired in a hospital or healthcare setting. These infections can be transmitted through various means, including contact with contaminated surfaces, equipment, or healthcare personnel. The given answer states that nosocomial infections are only transmitted by medical personnel, which is incorrect. Nosocomial infections can be transmitted through multiple routes, and healthcare personnel are just one potential source of transmission. Other factors, such as the patient's resident flora and contaminated environments, can also contribute to the occurrence of nosocomial infections. Medical and surgical asepsis practices are important in preventing and reducing the occurrence of these infections.
35.
If the ID for gonorrhea is 1,000 cells and the ID for tuberculosis is 10 cells, which organism is more virulent?
Correct Answer
B. Mycobacterium tuberculosis
Explanation
Mycobacterium tuberculosis is more virulent because it has a lower infectious dose (ID) of 10 cells compared to Neisseria gonorrhea's ID of 1,000 cells. A lower ID indicates that fewer cells of the organism are required to cause infection, making it more virulent.
36.
Nonspecific chemical defenses include
Correct Answer
E. All of the choices are correct
Explanation
All of the choices are correct because they all represent nonspecific chemical defenses in the body. Lysozyme is an enzyme that can break down the cell walls of certain bacteria, lactic acid and electrolytes of sweat create an acidic environment on the skin that inhibits the growth of bacteria, the skin's acidic pH and fatty acids also help to prevent the growth of harmful bacteria, and stomach hydrochloric acid helps to kill ingested pathogens. Therefore, all of these choices contribute to the body's nonspecific chemical defenses.
37.
The chemical found in tears and saliva that hydrolyzes the peptidoglycan in certain bacterial cell walls is
Correct Answer
C. Lysozyme.
Explanation
Lysozyme is an enzyme found in tears and saliva that breaks down the peptidoglycan layer in certain bacterial cell walls. This process is known as hydrolysis. Lactic acid, hydrochloric acid, histamine, and bile are not involved in this specific function of breaking down bacterial cell walls. Therefore, the correct answer is lysozyme.
38.
The body region where a ciliary escalator helps to sweep microbes trapped in mucus away from that body site is the
Correct Answer
B. Respiratory tract.
Explanation
The ciliary escalator is a mechanism in the respiratory tract that helps to move mucus and trapped microbes away from the lungs. Cilia, tiny hair-like structures, line the respiratory tract and beat in coordinated motions to create a wave-like movement. This movement helps to propel the mucus and any trapped particles, including microbes, out of the respiratory tract and prevent them from reaching the lungs. Therefore, the correct answer is the respiratory tract.
39.
Plasma
Correct Answer
E. All of the choices are correct.
Explanation
The correct answer is that all of the choices are correct. Plasma is indeed the liquid portion of blood in which blood cells are suspended. It is mostly water and contains albumin and globulins. Additionally, plasma also contains fibrinogen. Thus, all the given statements accurately describe the composition and characteristics of plasma.
40.
The blood cells that function in allergic reactions and inflammation, contain peroxidase and lysozyme, and particularly target parasitic worms and fungi are
Correct Answer
B. Eosinophils.
Explanation
Eosinophils are blood cells that contain peroxidase and lysozyme, which are enzymes that help in allergic reactions and inflammation. They are particularly effective in targeting and eliminating parasitic worms and fungi. Basophils, neutrophils, monocytes, and lymphocytes do not possess these specific enzymes and functions, making eosinophils the correct answer.
41.
The most numerous WBC's, that have multilobed nuclei and are very phagocytic are
Correct Answer
C. Neutrophils.
Explanation
Neutrophils are the most numerous white blood cells (WBCs) and have multilobed nuclei, making them easily identifiable. They are highly phagocytic, meaning they can engulf and destroy pathogens and debris. Basophils are involved in allergic reactions and release histamine. Eosinophils are responsible for combating parasitic infections. Monocytes are large phagocytic cells that differentiate into macrophages. Lymphocytes play a crucial role in the immune response. However, none of these cells have the combination of multilobed nuclei and high phagocytic activity like neutrophils do.
42.
All of the following pertain to platelets except
Correct Answer
A. They contain hemoglobin to transport oxygen and carbon dioxide.
Explanation
Platelets are small, irregularly-shaped cell fragments that are involved in blood clotting and inflammation. They are not whole cells but are pieces of cells. Platelets are also called thrombocytes, and they originate from giant multinucleate cells called megakaryocytes. However, platelets do not contain hemoglobin, which is responsible for transporting oxygen and carbon dioxide in red blood cells. Therefore, the statement "they contain hemoglobin to transport oxygen and carbon dioxide" is incorrect.
43.
Hemopoiesis is the
Correct Answer
C. Production of white blood cells, red blood cells, and platelets.
Explanation
Hemopoiesis refers to the process of producing blood cells. It involves the production of white blood cells, red blood cells, and platelets. This process takes place in the bone marrow, where stem cells differentiate into different types of blood cells. The correct answer states that hemopoiesis is the production of white blood cells, red blood cells, and platelets, which accurately describes the process.
44.
Diapedesis is the
Correct Answer
E. Migration of white blood cells from the blood out to the tissues.
Explanation
Diapedesis refers to the migration of white blood cells from the blood out to the tissues. This process is an important part of the immune response, as it allows white blood cells to leave the bloodstream and enter the tissues to target and eliminate pathogens or foreign substances. It is a crucial mechanism for the body's defense against infections and plays a role in inflammation and wound healing.
45.
The reticuloendothelial system
Correct Answer
E. All of the choices are correct.
Explanation
The reticuloendothelial system is a support network of connective tissue fibers that originates in the cellular basal lamina. It provides a passageway within and between tissues and organs. Additionally, it is heavily populated with macrophages. Therefore, all of the choices provided are correct.
46.
These structures are found along lymphatic vessels but are heavily clustered in the armpit, groin, and neck:
Correct Answer
A. Lymph nodes
Explanation
Lymph nodes are small, bean-shaped structures that are found along the lymphatic vessels. They act as filters for the lymphatic system, trapping and destroying harmful substances such as bacteria and viruses. Lymph nodes are heavily clustered in certain areas of the body, including the armpit, groin, and neck. This clustering allows them to effectively monitor and respond to infections or diseases in these regions. Therefore, lymph nodes are the correct answer to the question.
47.
The four classic signs and symptoms of inflammation include all the following except
Correct Answer
E. Chills.
Explanation
The four classic signs and symptoms of inflammation are redness, warmth, swelling, and pain. These symptoms are typically caused by increased blood flow and immune response to an injury or infection. Chills, on the other hand, are not typically associated with inflammation. Chills are more commonly associated with fever or a systemic infection. Therefore, chills do not fit into the category of classic signs and symptoms of inflammation.
48.
The circulating substances that affect the hypothalamus and initiate fever are
Correct Answer
D. Pyrogens.
Explanation
Pyrogens are substances that can cause fever by affecting the hypothalamus. They can be either endogenous or exogenous. Endogenous pyrogens are produced by the body itself, such as cytokines released by immune cells in response to infection or inflammation. Exogenous pyrogens are external substances, such as bacterial toxins or certain medications, that can also trigger fever. These pyrogens act on the hypothalamus, which is the body's temperature-regulating center, causing it to raise the body's temperature set point and initiate the fever response. Therefore, pyrogens are the circulating substances that affect the hypothalamus and initiate fever.
49.
Which is incorrect about complement?
Correct Answer
B. Only appear in the blood during a response to a pathogen
Explanation
Complement is a group of at least 26 blood proteins that act in a cascade reaction. It is not limited to only appearing in the blood during a response to a pathogen. Complement can also be activated by other factors such as immune complexes or tissue damage, and it plays a role in various immune responses including inflammation and clearance of cellular debris. Therefore, the statement "only appear in the blood during a response to a pathogen" is incorrect.
50.
Specificity and memory are associated with which body defense mechanism?
Correct Answer
D. T cell and B cell responses
Explanation
T cell and B cell responses are associated with specificity and memory in the body's defense mechanism. T cells and B cells are components of the adaptive immune system, which is responsible for recognizing and targeting specific pathogens. These cells have the ability to remember specific pathogens they have encountered before, allowing for a quicker and more effective response upon subsequent exposure. This specificity and memory are crucial in mounting an effective immune response against pathogens.