Microbiology - Viruses
Lassa fever a) Has been known in north Nigeria for over a century b) Occurs in Africa only in epidemic form c) Is easy to diagnose clinically as it has such a sudden onset of coughing. d) Can only be brought to Europe by travellers from West Africa
Lassa fever virus was first seen in 1969 in the Nigerian town of that name. It causes a severe, often fatal hemorrhagic fever characterized by multiple-organ involvement. The disease begins slowly with fever, headache, vomiting, and diarrhea and progresses to involve the lungs, heart, kidneys, and brain. A petechial rash and gastrointestinal tract hemorrhage ensue, followed by death from vascular collapse. Lassa fever virus is a member of the Arenavirus family, which includes other infrequent human pathogens such as lymphocytic choriomeningitis virus and certain members of the Tacaribe group. Arenaviruses ("arena" means sand) are united by their unusual appearance in the electron microscope. Their most striking feature is the "sandlike" particles on their surface, which are ribosomes. The function, if any, of these ribosomes is unknown. Arenaviruses are enveloped viruses with surface spikes, a helical nucleocapsid, and single-stranded RNA with negative polarity. The natural host for Lassa fever virus is the small rodent ## Mastomys, which undergoes a chronic, lifelong infection. The virus is transmitted to humans by contamination of food or water with animal urine. Secondary transmission among hospital personnel occurs also. Asymptomatic infection is widespread in areas of endemic infection. The diagnosis is made either by isolating the virus or by detecting a rise in antibody titer. ## Ribavirin reduces the mortality rate if given early, and hyperimmune serum, obtained from persons who have recovered from the disease, has been beneficial in some cases. No vaccine is available, and prevention centers on proper infection control practices and rodent control.
Paul Bunnel Test is done in a) Malta fever b) Enteric fever c) Infectious monnonucleosis d) Typhus fever
The immune response to EBV infection consists first of IgM antibody to the VCA. IgG antibody to the VCA follows and persists for life. The IgM response is therefore useful for diagnosing acute infection, whereas the IgG response is best for revealing prior infection. Lifetime immunity against second episodes of infectious mononucleosis is based on antibody to the viral membrane antigen. In addition to the EBV-specific antibodies, nonspecific heterophil antibodies are found. The term "heterophil" refers to antibodies that are detected by tests using antigens different from the antigens that induced them. The heterophil antibodies formed in infectious mononucleosis agglutinate sheep or horse red blood cells in the laboratory. (Cross-reacting Forssman antibodies in human serum are removed by adsorption with guinea pig kidney extract prior to agglutination.) Note that these antibodies do not react with any component of EBV. It seems likely that EBV infection modifies a cell membrane constituent such that it becomes antigenic and induces the heterophil antibody. Heterophil antibodies usually disappear within 6 months after recovery. These antibodies are not specific for EBV infection and are also seen in individuals with hepatitis B and serum sickness. Detection of heterophile antibodies is the diagnostic test of choice. The Heterophil antibody test is useful for the early diagnosis of infectious mononucleosis because it is usually positive by week 2 of illness. However, because the antibody titer declines after recovery, it is not useful for detection of prior infection. The antibodies react to antigens from phylogenetically unrelated species and agglutinate sheep red cells (the Paul-Bunnell reaction) and horse red blood cells (the 'Monospot test'). The Monospot test is often used to detect the heterophil antibody; it is more sensitive, more specific, and less expensive than the tube agglutination test. Reference: Lange microbiology textbook Kumar and Clark essentials of medicine
Which infection is not common in HIV patients a) Cryptosporidiosis b) Atypical mycobacterial infection c) Aspergillosis d) Candidiasis
The late stage of HIV infection is AIDS, manifested by a decline in the number of CD4 cells to below 400/L and an increase in the frequency and severity of opportunistic infections. The two most characteristic manifestations of AIDS are Pneumocystis pneumonia and Kaposi's sarcoma. However, many other opportunistic infections occur with some frequency. These include Viral infections such as disseminated herpes simplex, herpes zoster, and cytomegalovirus infections and progressive multifocal leukoencephalopathy Fungal infections such as thrush (caused by Candida albicans), cryptococcal meningitis, and disseminated histoplasmosis Protozoal infections such as toxoplasmosis and cryptosporidiosis and Disseminated bacterial infections such as those caused by Mycobacterium avium-intracellulare and Mycobacterium tuberculosis. Many AIDS patients have severe neurologic problems, e.g., dementia and neuropathy, which can be caused by either HIV infection of the brain or by many of these opportunistic organisms.
Most Probable cause of food poisoning in a child who has eaten Ice Cream 16-18 hrs earlier is a) Staph aureus b) Clostridum perfringens c) Clostridium botulinum d) Salmonella typhimurium
There is a great deal of confusion over the naming of Salmonella strains (even the people who work on Salmonella are confused!) but in essence, the strains which we will deal with here are generally different serovars of Salmonella enterica. There are three methods for naming the salmonella. (1) Ewing divides the genus into three species: S. typhi, Salmonella choleraesuis, and Salmonella enteritidis. In this scheme there is 1 serotype in each of the first two species and 1500 serotypes in the third. (2) Kaufman and White assign different species names to each serotype; there are roughly 1500 different species, usually named for the city in which they were isolated. Salmonella dublin according to Kaufman and White would be S. enteritidis serotype dublin according to Ewing. *** (3) The third approach to naming the salmonellae is based on relatedness determined by DNA hybridization analysis. In this scheme, S. typhi is not a distinct species but is classified as Salmonella enterica serotype (or serovar) typhi. All three of these naming systems are in current use. As their name suggests Salmonella enterica are involved in causing diseases of the intestines (enteric means pertaining to the intestine). The three main serovars of Salmonella enterica are Typhimurium, Enteritidis, and Typhi. Clinically, the Salmonella species are often thought of in two distinct categories, namely, the typhoidal species, i.e., those that cause typhoid fever and the non-typhoidal species, i.e., those that cause diarrhea (enterocolitis) and metastatic infections, such as osteomyelitis. The typhoidal species are S. typhi and S. paratyphi. The non-typhoidal species are the many strains of S. enteritidis. S. choleraesuis is the species most often involved in metastatic infections. Salmonella typhimurium is the most common species of Salmonella to cause enterocolitis in the United States, but almost every species has been involved. Septicemia is most often caused by S. choleraesuis.
The chances of acquiring HIV infection following needle prick is a) 0.3% b) 3-0 % c) 0-30 % d) 0.003 % a) 0.3% b) 3 % c) 30 % d) 0.03 %
a) 0.3% Risk of HIV transmission after single exposure to an HIV-infected source: SEXUAL: Vaginal intercourse: Female to male 0.05% Vaginal intercourse: Male to female 0.1% Anal intercourse: Insertive 0.05% ## Anal intercourse: Receptive 0.5% Oral intercourse: Insertive 0.005% Oral intercourse: Receptive 0.01% BLOOD EXPOSURE: Blood transfusion 90% Intravenous drug users sharing needles 0.67% Percutaneous needle stick injury 0.3% Mucous membrane splash 0.09% Mother to child Vaginal delivery 15% Breastfeeding (per month) 0.5% IV drug use (0.67) > Gay (receptive) (0.5) > Percutaneous needle (0.3) > Vaginal sex (female) (0.1)
All the following are true about HIV except a) A DNA virus belonging to lentivirus b) Attacks CD4 lymphocytes c) CD4:CD8 ratio is reversed d) Mostly spread by heterosexual contact
a) A DNA virus belonging to lentivirus
Basophilic inclusion bodies are seen in a) Adeno virus b) Polio virus c) Measles virus d) Herpes virus
a) Adeno virus Cowdry type B in Polio and adenovirus Cowdry type A in Herpes simplex virus and Varicella zoster virus Intranuclear basophilic- Cowdry type B in Adenovirus "owl eyes" in cytomegalovirus
Pandemics caused by inflenza virus is due to a) Antigenic shift b) Antigenic drift c) Endemicity d) Virulence
a) Antigenic shift
Human papilloma virux is associated with this carcinoma a) Carcinoma cervix b) Burkett s lymphoma c) Kaposi sarcoma d) Malignant melanoma
a) Carcinoma cervix
AIDS virus is believed to have originated from a) Central Africa b) Britain c) Canada d) France (Paris)
a) Central Africa
True about Mycosis fungoides a) Cutaneous T. cell lymphoma b) Cutaneous B cell lymphoma c) A type of All d) A type of Hodgkin s lymphoma
a) Cutaneous T. cell lymphoma
Oral hairy leukoplakia caused by a) Ebstein barr virus b) CMV c) HIV d) HZV
a) Ebstein barr virus
Strain used for measles a) Edmonston b) ra 27/3 c) 17d d) none
a) Edmonston
Virion is defined as a) Extracellular infectious virus particle b) Smallest virus c) A smallest particle similar to virus d) None of the above
a) Extracellular infectious virus particle
Hepatitis E clinically resembles a) Hepatitis A b) Hepatitis B c) Hepatitis C d) Hepatitis D
a) Hepatitis A
Which of the following viruses is not a cause of congenital infection- a) Hepatitis A b) Hepatitis B c) Rubella virus d) Cytomegalovirus
a) Hepatitis A
Prophylactic vaccines are available for hepatitis a) Hepatitis A,B b) Hepatitis B, C c) Hepatitis C, D d) Hepatitis A, D
a) Hepatitis A,B Hepatitis A: Active immunization with a vaccine containing inactivated HAV is available. The virus is grown in human cell culture and inactivated with formalin. Two doses, an initial dose followed by a booster 6-12 months later, should be given. No subsequent booster dose is recommended. The vaccine is recommended for travelers to developing countries, for children ages 2-18 years, and for men who have sex with men. Because many adults have antibodies to HAV, it may be cost-effective to determine whether antibodies are present before giving the vaccine. It is also effective in post-exposure prophylaxis if given within 2 weeks of exposure. A combination vaccine that immunizes against both HAV and HBV called Twinrix is available. Twinrix contains the same immunogens as the individual HAV and HBV vaccines. Passive immunization with immune serum globulin prior to infection or within 14 days after exposure can prevent or mitigate the disease. Observation of proper hygiene, e.g., sewage disposal and hand washing after bowel movements, is of prime importance. Hepatitis B: Prevention involves the use of either the vaccine or hyperimmune globulin or both. The vaccine, e.g., Recombivax, contains HBsAg produced in yeasts by recombinant DNA techniques. The vaccine is highly effective in preventing hepatitis B and has few side effects. It is indicated for people who are frequently exposed to blood or blood products, such as certain health care personnel (e.g., medical students, surgeons, and dentists), patients receiving multiple transfusions or dialysis, patients with frequent sexually transmitted disease, and abusers of illicit intravenous drugs. Travelers who plan a long stay in areas of endemic infection, such as many countries in Asia and Africa, should receive the vaccine. The U.S. Public Health Service recommends that all newborns and adolescents receive the vaccine. ## At present, booster doses after the initial three-dose regimen are not recommended. Widespread immunization with the HBV vaccine in Taiwan has significantly reduced the incidence of hepatocellular carcinoma in children. A vaccine called Twinrix that contains both HBsAg and inactivated HAV provides protection against both hepatitis B and hepatitis A. Hepatitis B immune globulin (HBIG) contains a high titer of HBsAb because it is prepared from sera of patients who have recovered from hepatitis B. It is used to provide immediate, passive protection to individuals known to be exposed to HBsAg-positive blood, e.g., after an accidental needle stick. After the needle-stick injury from a patient with HBsAg-positive blood, the recommendation is that both the vaccine and HBIG be given (at separate sites). This is true even if the patient's blood is HBeAb positive. Both the vaccine and HBIG should also be given to a newborn whose mother is HBsAg-positive. These are good examples of passive-active immunization, in which both immediate and long-term protection are provided. All blood for transfusion should be screened for HBsAg. No one with a history of hepatitis (of any type) should donate blood, because non-A, non-B viruses may be present.
The most common presentation of congenital CMV infection is a) Hepatosplenomegaly b) Microcephaly c) Cerebral calcification d) Chorioretinitis
a) Hepatosplenomegaly Approximately 20% of infants infected with CMV during gestation show clinically apparent manifestations of cytomegalic inclusion disease such as microcephaly, seizures, deafness, jaundice, and purpura. Hepatosplenomegaly is very common. Cytomegalic inclusion disease is one of the leading causes of mental retardation in the United States. Infected infants can continue to excrete CMV, especially in the urine, for several years.
"Plaque test" is used routinely in virology labs for- a) Identification of viral disease b) To separate specific clone of virus c) To maintain certain viral culture d) To prepare vaccines
a) Identification of viral disease
Hepatitis A virus is best diagnosed by a) IgM antibodies in serum b) Isolation from stool c) Culture from blood d) Isolation from bile
a) IgM antibodies in serum
It is true regarding the normal microbial flora present on the skin and mucous membranes that a) It cannot be eradicated by antimicrobial agents b) It is absent in the stomach due to the acidic pH. c) It establishes in the body only after the neonatal period. d) The flora in the small bronchi is similar to that of the trachea.
a) It cannot be eradicated by antimicrobial agents Normal flora of the Skin: The predominant organism is Staphylococcus epidermidis, which is a nonpathogen on the skin but can cause disease when it reaches certain sites such as artificial heart valves and prosthetic joints. It is found on the skin much more frequently than its pathogenic relative Staphylococcus aureus. There are about 10³-10⁴ organisms/cm² of skin. Most of them are located superficially in the stratum corneum, but some are found in the hair follicles and act as a reservoir to replenish the superficial flora after hand washing. Anaerobic organisms, such as Propionibacterium and Peptococcus, are situated in the deeper follicles in the dermis where oxygen tension is low. Propionibacterium acnes is a common skin anaerobe that is implicated in the pathogenesis of acne. Normal Flora of the Intestinal Tract In normal fasting people, the stomach contains few organisms because of its low pH and its enzymes. The small intestine usually contains small numbers of streptococci, lactobacilli, and yeasts, particularly C. albicans. Larger numbers of these organisms are found in the terminal ileum. Although the normal flora extensively populates many areas of the body, the internal organs usually are sterile. Areas such as the central nervous system, blood, lower bronchi and alveoli, liver, spleen, kidneys, and bladder are free of all but the occasional transient organism.
Which one of the following is a characteristic of human immune deficiency virus a) It cannot cross blood brain barrier b) It is resistant to acetone c) It is easily killed by heat d) It is easily killed by T4 lymphocytes
a) It cannot cross blood brain barrier In general, the presence of an envelope confers instability on the virus. Enveloped viruses are more sensitive to heat, drying, detergents, and lipid solvents such as alcohol and ether than are nonenveloped (nucleocapsid) viruses, which are composed only of nucleic acid and capsid proteins.
Property of elution is found in a) Myxoviras b) Togavirus c) Panovirus d) Adenovirus
a) Myxoviras
Segmented double stranded RNA virus is seen in- a) Reovirus b) Myxovirus c) Rabies d) Parvo virus
a) Reovirus Reoviruses, including rotavirus, are composed of a segmented, double-stranded RNA genome surrounded by a double-layered icosahedral capsid without an envelope. Many domestic animals are infected with their own strains of rotaviruses, but these are not a source of human disease. There are at least six serotypes of human rotavirus. The outer surface protein (also known as the viral hemagglutinin) is the type-specific antigen and elicits protective antibody
Following is the marker of HIV infection in blood a) Reverse Transcriptase b) DNA polymerase c) RNA polymerase d) None
a) Reverse Transcriptase The HIV genome is the most complex of the known retroviruses. In addition to the three typical retroviral genes gag, pol, and env, which encode the structural proteins, the genome RNA has six regulatory genes. Two of these regulatory genes, tat and rev, are required for replication, and the other four - nef, vif, vpr, and vpu, are not required for replication and are termed "accessory" genes. The pol gene encodes several proteins, including the virion "reverse transcriptase," which synthesizes DNA by using the genome RNA as a template, an integrase that integrates the viral DNA into the cellular DNA, and a protease that cleaves the various viral precursor proteins. Three enzymes are located within the nucleocapsid of the virion: reverse transcriptase, integrase, and protease. Reverse transcriptase is the RNA-dependent DNA polymerase that is the source of the family name retroviruses. This enzyme transcribes the RNA genome into the proviral DNA. Reverse transcriptase is a bifunctional enzyme; it also has ribonuclease H activity. Ribonuclease H degrades RNA when it is in the form of an RNA-DNA hybrid molecule. The degradation of the viral RNA genome is an essential step in the synthesis of the double-stranded proviral DNA. Integrase, another important enzyme within the virion, mediates the integration of the proviral DNA into the host cell DNA. The viral protease cleaves the precursor polyproteins into functional viral polypeptides.
Parvovirus B19 does not cause a) Roseola infantum b) Aplastic anemia in sickle cell disease c) Fetal hydrops d) None of the above
a) Roseola infantum
Mad cow disease is caused by a) Slow virus b) Ebola virus c) Hantan virus d) West Nile virus
a) Slow virus
]Mad cow disease is due to a) Slow virus b) Mycoplasma c) Bacteria d) Fungus
a) Slow virus
Which is not oncogenic out of the following viruses a) Varicella b) EBV c) HILV d) All of the above
a) Varicella
Sero Conversion in HIV Infection takes place in a) 2 weeks b) 4 weeks c) 9 weeks d) 12 weeks
b) 4 weeks During the first month after infection, antibody tests may be negative. These false-negative tests are due to insufficient antibody being made early in infection to be detected in the ELISA test. The average time for seroconversion is 10 to 14 days and most, but not all, will have seroconverted by 4 weeks. In view of this, the diagnosis of acute HIV infection may not be able to be made using serologic tests. The presence of HIV can be detected best during acute infection by the plasma HIV RNA assay (viral load) as viremia is typically high at this early stage. The p24 antigen test or viral culture can also be used.
Hospital acquired organisms are all except a) Staphylococcus b) Accinobacter c) Streptococcus d) Pseudomonas
b) Accinobacter
A patient of immunocOmpromised due to transplantation is suffering from pyrexia and neutropenia. Most likely cause is a) HSV b) CMV c) Gram ye organism d) Gram + organism
b) CMV It also causes pneumonia and other diseases in immunocompromised patients and heterophil-negative mononucleosis in immunocompetent individuals. In immunocompetent adults, CMV can cause heterophil-negative mononucleosis, which is characterized by fever, lethargy, and the presence of abnormal lymphocytes in peripheral blood smears. Systemic CMV infections, especially pneumonitis and hepatitis, occur in a high proportion of immunosuppressed patients, e.g., those with renal and bone marrow transplants. In AIDS patients, CMV commonly infects the intestinal tract and causes intractable colitis. CMV also causes retinitis in AIDS patients, which can lead to blindness.
Mad Cow disease (Bovine Spongioform Encephalopathy) is similar in man to a) Alzeimeris Disease b) Creutzfeldt Jakob Disease c) Huntingtons Chorea d) Picks Disease
b) Creutzfeldt Jakob Disease
All of the following statements about Parvovirus B 19 are true, Except a) DNA virus b) Crosses placenta in only <10% of cases c) Can cause severe anemia d) Can cause aplastic crisis
b) Crosses placenta in only <10% of cases
The vector of Japaness B encepalitis virus is a) Anopheles mosquito b) Culex mosquito c) Aedes mosquito d) All of the above
b) Culex mosquito This virus is the most common cause of epidemic encephalitis. The disease is characterized by fever, headache, nuchal rigidity, altered states of consciousness, tremors, incoordination, and convulsions. The mortality rate is high, and neurologic sequelae are severe and can be detected in most survivors. The disease occurs throughout Asia but is most prevalent in Southeast Asia. The rare cases seen in the United States have occurred in travelers returning from that continent. American military personnel in Asia have been affected. Japanese encephalitis virus is a member of the flavivirus family. It is transmitted to humans by certain species of Culex mosquitoes endemic to Asian rice fields. There are two main reservoir hosts—birds and pigs. The diagnosis can be made by isolating the virus, by detecting IgM antibody in serum or spinal fluid, or by staining brain tissue with fluorescent antibody. There is no antiviral therapy. Prevention consists of an inactivated vaccine and pesticides to control the mosquito vector. Immunization is recommended for individuals living in areas of endemic infection for several months or longer.
Hepatitis B is caused by a) RNA virus b) DNA virus c) Mycoplasma d) Reckettsia
b) DNA virus
All are DNA virus except a) Varicella zoster virus b) Dengue virus c) HBV d) Pavovirus B19
b) Dengue virus 6 group of DNA viruses The three naked (i.e. nonenveloped) icosahedral virus families—the parvoviruses, papovaviruses, and adenoviruses—are presented in order of increasing particle size, as are the three enveloped families. The hepadnavirus family, which includes hepatitis B virus, and the herpesviruses are enveloped icosahedral viruses. The largest viruses, the poxviruses, have a complex internal symmetry. Flaviviruses are Enveloped viruses with an icosahedral capsid and single-stranded, linear, nonsegmented, ## positive-polarity RNA. The flaviviruses include hepatitis C virus, yellow fever virus, dengue virus, West Nile virus, and St. Louis and Japanese encephalitis viruses.
True regarding influenza virus is a) All types exhibit antigenic shift b) Drift is accumulation of point mutation c) Only type A shows antigenic drift d) None of the above
b) Drift is accumulation of point mutation Influenza virus is composed of a segmented single-stranded RNA genome, a helical nucleocapsid, and an outer lipoprotein envelope. The virion contains an RNA-dependent RNA polymerase, which transcribes the negative-polarity genome into mRNA. The genome is therefore not infectious. The envelope is covered with two different types of spikes, a hemagglutinin and a neuraminidase. Influenza A virus has 16 antigenically distinct types of hemagglutinin (HA) and 9 antigenically distinct types of neuraminidase (NA). The function of the hemagglutinin is to bind to the cell surface receptor (neuraminic acid, sialic acid) to initiate infection. In the clinical laboratory, the hemagglutinin agglutinates red blood cells, which is the basis of a diagnostic test called the hemagglutination inhibition test. The hemagglutinin is also the target of neutralizing antibody. The neuraminidase cleaves neuraminic acid (sialic acid) to release progeny virus from the infected cell. The hemagglutinin functions at the beginning of infection, whereas the neuraminidase functions at the end. Neuraminidase also degrades the protective layer of mucus in the respiratory tract. This enhances the ability of the virus to infect the respiratory epithelium. Influenza viruses, especially influenza A virus, show changes in the antigenicity of their hemagglutinin and neuraminidase proteins; this property contributes to their capacity to cause devastating worldwide epidemics. There are two types of antigenic changes: (1) antigenic shifts, which are major changes based on the reassortment of segments of the genome RNA and (2) antigenic drifts, which are minor changes based on mutations in the genome RNA. Note that in reassortment, entire segments of RNA are exchanged, each one of which codes for a single protein, e.g., the hemagglutinin. Reye's syndrome, characterized by encephalopathy and liver degeneration, is a rare, life-threatening complication in children following some viral infections, particularly influenza B and chickenpox.
Most common route of spread of Hepatitis E is a) Sex b) Feco-oral c) Blood transfusion d) IV injections
b) Feco-oral
The most common pathogens responsible for nosocomial pneumonias in the ICU are a) Gram positive organisms b) Gram negative organisms c) Mycoplasma d) Virus infections
b) Gram negative organisms Staphylococcal pneumonia can occur in postoperative patients or following viral respiratory infection, especially influenza. Staphylococcal pneumonia often leads to empyema or lung abscess. In many hospitals it is the most common cause of nosocomial pneumonia in general and especially of ventilator-associated pneumonia in intensive care units. CA-MRSA causes a severe necrotizing pneumonia.
EB virus belong to which group a) Retro virus b) Herpes virus c) RNA virus d) Pox virus
b) Herpes virus The herpesvirus family can be subdivided into three categories based on the type of cell most often infected and the site of latency. The alpha herpesviruses, consisting of herpes simplex viruses 1 and 2, and varicella-zoster virus infect epithelial cells primarily and cause latent infection in neurons. The beta herpesviruses, consisting of cytomegaloviruses and human herpesvirus 6, infect and become latent in a variety of tissues. The gamma herpesviruses, consisting of Epstein-Barr virus and human herpesvirus 8 (Kaposi's sarcoma-associated virus), infect and become latent primarily in lymphoid cells.
Regarding prion protein which of the following statment is true a) It is protein product coded in viral DNA b) It catalyses abnormal folding of other proteins c) It protect disulfide bonds from oxidation d) It cleaves normal proteins
b) It catalyses abnormal folding of other proteins Prions are protein-containing particles with no detectable nucleic acid that are highly resistant to inactivation by heat, formaldehyde, and ultraviolet light at doses that will inactivate viruses. Note that prions are resistant to the temperatures usually employed in cooking, a fact that may be important in their suspected ability to be transmitted by food (variant Creutzfeldt-Jakob disease [CJD]). Prions are, however, inactivated by protein- and lipid-disrupting agents such as phenol, ether, NaOH, and hypochlorite. The prion protein is encoded by a normal cellular gene and is thought to function in a signal transduction pathway in neurons. The normal prion protein (known as PrPC, or prion protein cellular) has a significant amount of alpha-helical conformation. When the alpha-helical conformation changes to a beta-pleated sheet (known as PrPSC, or prion protein scrapie), these abnormal forms aggregate into filaments, which disrupt neuron function and cause cell death. Prions, therefore, "reproduce" by the abnormal beta-pleated sheet form recruiting normal alpha-helical forms to change their conformation. Note that the normal alpha-helical form and the abnormal beta-pleated sheet form have the same amino acid sequence. It is only their conformation that differs. A specific cellular RNA enhances this conformational change.
Rabies is identified by a) Guarneri bodies b) Negri bodies c) Cowdry A bodies d) Cowdry B bodies
b) Negri bodies
Diagnostic of Rabies a) Guarneri bodies b) Negri bodies c) Cowdry A body d) Bollinger bodies
b) Negri bodies Rapid diagnosis of rabies infection in the animal is usually made by examination of brain tissue by using either fluorescent antibody to rabies virus or histologic staining of Negri bodies in the cytoplasm of hippocampal neurons. The virus can be isolated from the animal brain by growth in cell culture, but this takes too long to be useful in the decision of whether to give the vaccine. Rabies in humans can be diagnosed by fluorescent-antibody staining of a biopsy specimen, usually taken from the skin of the neck at the hairline; by isolation of the virus from sources such as saliva, spinal fluid, and brain tissue; or by a rise in titer of antibody to the virus. Negri bodies can be demonstrated in corneal scrapings and in autopsy specimens of the brain
Hepatitis B is not transmitted by a) Blood transfusion b) Pasteurised albumin c) Cryoprecipitate d) Sexual contact
b) Pasteurised albumin
All are oncogenic viruses except a) EB virus b) Reo virus c) Retrovirus d) Human papilloma virus
b) Reo virus At present, only two viruses, human T-cell lymphotropic virus and human papillomavirus, are considered to be human tumor viruses. However, several other candidate viruses are implicated by epidemiologic correlation, by serologic relationship, or by recovery of virus from tumor cells Other viruses a. EBV b. HBV c. HCV d. HHV-8
Reye s syndrome following influenza is most commonly associated with a) Type A b) Type B c) Type C d) All of the above
b) Type B
True about Rota virus is all except a) Type A is seen in animals b) Type B can be cultured c) Type C is seldom seen in children d) Vaccine given only for severe cases
b) Type B can be cultured
Number of doses of HDCV vaccine required for preexposure prophylaxis a) 7 b) 5 c) 3 d) 1
c) 3 Rabies virus is the only medically important member of the rhabdovirus family. It has a single-stranded RNA enclosed within a bullet-shaped capsid surrounded by a lipoprotein envelope. Because the genome RNA has negative polarity, the virion contains an RNA-dependent RNA polymerase. Rabies virus has a single antigenic type. The antigenicity resides in the envelope glycoprotein spikes. There are two approaches to prevention of rabies in humans: preexposure and postexposure. Preexposure immunization with rabies vaccine should be given to individuals in high-risk groups, such as veterinarians, zookeepers, and travelers to areas of hyperendemic infection, e.g., Peace Corps members. Preexposure immunization consists of three doses given on days 0, 7, and 21 or 28. Booster doses are given as needed to maintain an antibody titer of 1:5. The rabies vaccine is the only vaccine that is routinely used postexposure, i.e., after the person has been exposed to the virus via animal bite. The long incubation period of the disease allows the virus in the vaccine sufficient time to induce protective immunity. In the United States, the rabies vaccine contains inactivated virus grown in human diploid cells. (Vaccine grown in monkey lung cells or chick embryo cells is also available.) In other countries, the duck embryo vaccine or various nerve tissue vaccines are available as well. Duck embryo vaccine has low immunogenicity, and the nerve tissue vaccines can cause an allergic encephalomyelitis as a result of a cross-reaction with human myelin; for these reasons, the human diploid cell vaccine (HDCV) is preferred. Postexposure immunization involves the use of both the vaccine and human rabies immune globulin (RIG, obtained from hyperimmunized persons) plus immediate cleaning of the wound. This is an example of passive-active immunization. Tetanus immunization should also be considered. The decision to give post-exposure immunization depends on a variety of factors, such as (1) the type of animal (all wild-animal attacks demand immunization) (2) whether an attack by a domestic animal was provoked, whether the animal was immunized adequately, and whether the animal is available to be observed; and (3) whether rabies is endemic in the area. The advice of local public health officials should be sought. ## Hospital personnel exposed to a patient with rabies need not be immunized unless a significant exposure has occurred, e.g., a traumatic wound to the health care worker. If the decision is to immunize, both HDCV and RIG are recommended. Five doses of HDCV are given (on days 0, 3, 7, 14, and 28), but RIG is given only once with the first dose of HDCV (at a different site). HDCV and RIG are given at different sites to prevent neutralization of the virus in the vaccine by the antibody in the RIG. As much as possible of the RIG is given into the bite site, and the remainder is given intramuscularly. If the animal has been captured, it should be observed for 10 days and euthanized if symptoms develop. The brain of the animal should be examined by immunofluorescence. The vaccine for immunization of dogs and cats consists of inactivated rabies virus. The first immunization is usually given at 3 months of age, with booster doses given either annually or at 3-year intervals. In the United States, an alternative vaccine used in dogs and cats contains live canarypox virus genetically engineered to contain the gene for the envelope protein of rabies virus.
Latent infection is seen in a) Small pox b) Adeno virus c) Chicken pox d) Measles
c) Chicken pox
Pocks on chick embryo are formed by all except a) Variola b) Vaccinia c) Chickenpox d) Cowpox
c) Chickenpox Chickenpox is not a pox virus infection. It is a Herpes virus infection caused by varicella zoster. The pox viruses include Variola- Small pox Molluscum contagiosum Vaccinia Cow pox
The most common organism amongst the following that causes acute meningitis in an AIDS patients is- a) Streptococcus pneumoniae b) Steptococcus agalactiae c) Cryptococcus neoformans d) Listeria monocytogenes.
c) Cryptococcus neoformans
Japanese B encephalitis virus is transmitted by a) Aedes aegypti b) Culex fatigans c) Culex tritaeniorhynchus d) Hard tick
c) Culex tritaeniorhynchus
Hepatitis A is transmitted by a) Blood route b) Inhalation c) Feco-oral route d) All
c) Feco-oral route
Bollinger bodies are seen in a) Chickenpox b) Cowpox c) Fowlpox d) Smallpox
c) Fowlpox
All of the following methods are used for the diagnosis of HIV in a 2 month old child, except a) DNA PCR b) Viral culture c) HIV ELISA d) p24 antigen assay
c) HIV ELISA During the first month after infection, antibody tests may be negative. These false-negative tests are due to insufficient antibody being made early in infection to be detected in the ELISA test. The average time for seroconversion is 10 to 14 days and most, but not all, will have seroconverted by 4 weeks. In view of this, the diagnosis of acute HIV infection may not be able to be made using serologic tests. The presence of HIV can be detected best during acute infection by the plasma HIV RNA assay (viral load) as viremia is typically high at this early stage. The p24 antigen test or viral culture can also be used.
All viruses are oncogenic except- a) EBV b) HTLV-1 c) HSV-1 d) HPV
c) HSV-1
Epstein-Barr Virus has been associated with the following disorders, except a) Burkitt s lymphoma b) Nasopharyngeal carcinoma c) Hairy cell leukemia d) Oral hairy leukoplakia
c) Hairy cell leukemia EBV causes infectious mononucleosis. It is associated with Burkitt's lymphoma, other B-cell lymphomas, and nasopharyngeal carcinoma. EBV is also associated with hairy leukoplakia, a whitish, nonmalignant lesion on the tongue seen especially in AIDS patients.
HBV is associated with all of the following except a) Hepatic cancer b) Chronic hepatitis c) Hepatic adenoma d) Cirrhosis
c) Hepatic adenoma About 5% of patients with HBV infection become chronic carriers. HBV DNA exists primarily as an episome in the cytoplasm of persistently infected cells; a small number of copies of HBV DNA are integrated into cell DNA. A high rate of hepatocellular carcinoma occurs in chronic carriers. The HBV genome has no oncogene, and hepatocellular carcinoma appears to be the result of persistent cellular regeneration that attempts to replace the dead hepatocytes. Alternatively, malignant transformation could be the result of insertional mutagenesis, which could occur when the HBV genome integrates into the hepatocyte DNA. Integration of the HBV DNA could activate a cellular oncogene, leading to a loss of growth control.
Presence of HBe Ag in patients with hepatitis indicates a) Simple carriers b) Late convalescence c) High infectivity d) Carrier status
c) High infectivity
A recent Hepatitis B infection is confirmed by the demonstration of serum a) HBs Ag b) HBcAg c) IgM and Anti HBc Anti bodies and HBsAg d) Anti HBs Antibodies
c) IgM and Anti HBc Anti bodies and HBsAg
Antigenic drift is commonly seen in a) Cholera b) Diptheria c) Influenza virus d) Typhoid
c) Influenza virus
Best means of giving hepatitis B vaccine is a) Subcutaneous b) Intradermal c) Intramuscular deltoid d) Intramuscular gluteal
c) Intramuscular deltoid
Which of the following flavi virus is closely related to Russian spring summer encephalitis causing virus a) Dengue b) Chickengunya c) KFD d) West Nile fever
c) KFD
Which of the following statements is true regarding ARBO viruses a) Yellow fever is endemic in India b) Dengue virus has only one serotype c) Kyasanur Forest Disease (KFD) is transmitted by ticks d) Mosquito of culex vishnoi-complex is the vector of Dengue fever
c) Kyasanur Forest Disease (KFD) is transmitted by ticks
Which of the following is an emerging pathogen of food poisoning a) Pseudomonas aeruginosa b) Salmonella typhi c) Listeria monocytogenes d) Enterococcus faecalis
c) Listeria monocytogenes Site is saying: a) Pseudomonas aeruginosa Listeria is implicated in outbreaks of febrile gastroenteritis. The organism is distributed worldwide in animals, plants, and soil. From these reservoirs, it is transmitted to humans primarily by ingestion of unpasteurized milk products, undercooked meat, and raw vegetables. Contact with domestic farm animals and their feces is also an important source. In the United States, listeriosis is primarily a food-borne disease associated with eating unpasteurized cheese and delicatessen meats. Gastroenteritis caused by L. monocytogenes is characterized by watery diarrhea, fever, headache, myalgias, and abdominal cramps but little vomiting. Outbreaks are usually caused by contaminated dairy products, but undercooked meats such as chicken and hot dogs have also been involved. Listeria gastroenteritis typically does not require treatment. The appearance of gram-positive rods resembling diphtheroids and the formation of small, gray colonies with a narrow zone of beta-hemolysis on a blood agar plate suggest the presence of Listeria. The isolation of Listeria is confirmed by the presence of motile organisms, which differentiate them from the nonmotile corynebacteria. Identification of the organism as L. monocytogenes is made by sugar fermentation tests.
Lambda phage which of the following is true a) It causes mad cow disease b) Lysogenic to lytic conversion cannot occur c) Lysogenic inform incorporates in host DNA & remain dormant d) Lytic phase incorporates in host DNA, proliferate & causes rupture of cell
c) Lysogenic inform incorporates in host DNA & remain dormant
## Most sensitive diagnostic test for dengue is a) IgM ELISA b) Complement fixation test c) Neutralization test d) Electron microscopy
c) Neutralization test The diagnosis can be made in the laboratory either by isolation of the virus in cell culture or by serologic tests that demonstrate the presence of IgM antibody or a fourfold or greater rise in antibody titer in acute and convalescent sera.
Smallest DNA virus is a) Herpes virus b) Adeno virus c) Parvo virus d) Pox virus
c) Parvo virus Parvoviruses These are very small (22 nm in diameter), naked icosahedral viruses with single-stranded linear DNA. There are two types of parvoviruses: defective and nondefective. The defective parvoviruses, e.g., adeno-associated virus, require a helper virus for replication. The DNA of defective parvoviruses is unusual because plus-strand DNA and minus-strand DNA are carried in separate particles. The nondefective parvoviruses are best illustrated by B19 virus, which is associated with aplastic crises in sickle cell anemia patients and with erythema infectiosum, an innocuous childhood disease characterized by a "slapped-cheeks" rash.
Most common disease caused by CMV in a post renal transplant patients a) Pyelonephritis b) Meningitis c) Pneumonia d) GI ulceration
c) Pneumonia
Which one of the following statements is true about rabies virus a) It is double stranded RNA virus b) Contains a DNA -dependent RNA polymerase c) RNA has a negative polarity d) Affects motor neurons
c) RNA has a negative polarity
Virus cell culture is done in all except a) ECHO b) Coxsackie c) Rota d) Entero 70
c) Rota
All the statements are correct about hepatitis viruses, except- a) Maximum chance of chronic infection in HCV b) Pregnant woman with HEV has 10-20% chance of mortality c) Vaccine is available only against HBV d) HBV and HCV has oncogenic potential
c) Vaccine is available only against HBV
Zoster recurrence occur after infection with a) HSV.1 b) HSV.2 c) Varicella d) Small pox
c) Varicella
Best laboratory method to diagonse AIDS infection is a) RIA b) ELISA c) Western Blot test d) Oxford test When does the HIV RNA begin to rise after infection? When does the p24 antigen begin to rise after infection?
c) Western Blot test The presumptive diagnosis of HIV infection is made by the detection of antibodies by ELISA. Because there are some false-positive results with this test, the definitive diagnosis is made by Western blot analysis, in which the viral proteins are displayed by acrylamide gel electrophoresis, transferred to nitrocellulose paper (the blot), and reacted with the patient's serum. If antibodies are present, they will bind to the viral proteins (predominantly to the gp41 or p24 protein). Enzymatically labeled antibody to human IgG is then added. A color reaction reveals the presence of the HIV antibody in the infected patient's serum. OraQuick is a rapid screening immunoassay for HIV antibody that uses a blood sample obtained by fingerprick. Results are available in 20 minutes. Positive results require confirmation by a Western blot test. HIV can be grown in culture from clinical specimens, but this procedure is available only at a few medical centers. The polymerase chain reaction (PCR) is a very sensitive and specific technique that can be used to detect HIV DNA within infected cells. Some individuals who do not have detectable antibodies have been shown by this test to be infected. As already mentioned, the amount of viral RNA in the plasma (i.e., the viral load) can also be determined using PCR-based assays. During the ** first month after infection, antibody tests may be negative. In view of this, the diagnosis of acute HIV infection may not be able to be made using serologic tests. The presence of HIV can be detected during that period by either viral culture, p24 antigen test, or PCR assay. Approximately ## 10-20 days after infection, an increase in HIV RNA can be detected by PCR assay and by ## 30 days after infection, an increase in p24 antigen can be seen in patients whose antibody test results are negative.
Percentage of polio infections which are subclinical is a) 1% b) 10% c) 22% d) 90%
d) 90% The range of responses to poliovirus infection includes (1) inapparent, asymptomatic infection; (2) abortive poliomyelitis; (3) nonparalytic poliomyelitis; and (4) paralytic poliomyelitis. Asymptomatic infection is quite common. Roughly 1% of infections are clinically apparent. The incubation period is usually 10-14 days. The most common clinical form is abortive poliomyelitis, which is a mild, febrile illness characterized by headache, sore throat, nausea, and vomiting. Most patients recover spontaneously. Nonparalytic poliomyelitis manifests as aseptic meningitis with fever, headache, and a stiff neck. This also usually resolves spontaneously. In paralytic poliomyelitis, flaccid paralysis is the predominant finding, but brain stem involvement can lead to life-threatening respiratory paralysis. Painful muscle spasms also occur. The motor nerve damage is permanent, but some recovery of muscle function occurs as other nerve cells take over. In paralytic polio, both the meninges and the brain parenchyma (meningoencephalitis) are often involved. If the spinal cord is also involved, the term meningomyeloencephalitis is often used. A post-polio syndrome that occurs many years after the acute illness has been described. Marked deterioration of the residual function of the affected muscles occurs many years after the acute phase. The cause of this deterioration is unknown. No permanent carrier state occurs following infection by poliovirus, but virus excretion in the feces can occur for several months.
DNA virus is a) Polio type I b) Polio type II c) Echovirus d) Adenovirus
d) Adenovirus
Rabies virus inactivated by a) Phenol b) UV radiation c) BPL d) All
d) All
Coxsackie B virus causes all except a) Aseptic meningitis b) Herpangina c) Hand-foot syndrome d) Bornholm disease
d) Bornholm disease Coxsackie viruses cause a variety of diseases. Group A viruses cause, for example, herpangina, acute hemorrhagic conjunctivitis, and hand-foot-and-mouth disease, whereas group B viruses cause pleurodynia, myocarditis, and pericarditis. Both types cause nonspecific upper respiratory tract disease (common cold), febrile rashes, and aseptic meningitis. Coxsackie viruses and echoviruses (see next section) together cause approximately 90% of cases of viral (aseptic) meningitis.
Ebstein Barr virus causes all except a) Bukitt s lymphome b) Infectious mononucleosis c) Nasopharnygeal carcinoma d) Carcinoma cervix
d) Carcinoma cervix
Which of the following is not a pox virus- a) Cow pox b) Molluscum contagiosum c) Small pox d) Chicken pox
d) Chicken pox
Serological study for prevalence of Hepatitis B is best by a) Surface antigen b) Surface antibody c) Core antigen d) Core antibody
d) Core antibody
All of the following are components of Dane Particle except a) Surface antigen b) Core antigen c) C-antigen d) Delta antigen
d) Delta antigen
Hepatitis C virus resembles which of the following virus groups a) Picarno viruses b) Herpes viruses c) Hepadna viruses d) Flavi viruses
d) Flavi viruses
Which of the following does not go into chronic hepatitis stage a) HBV b) HCV c) HDV d) HEV
d) HEV
Enteroviruses are associated with all of the following, Except- a) Aseptic Meningitis b) Pleurodynia c) Herpangina d) Hemorrhagic fever
d) Hemorrhagic fever
Regarding Hepatitis E, it is true that a) Occurs with Hepatitis B b) Is single stranded DNA virus c) Occurs along with HIV d) Increases mortality in pregnancy
d) Increases mortality in pregnancy HEV is a nonenveloped, single-stranded RNA virus classified as a member of the hepevirus family. Clinically the disease resembles hepatitis A, with the exception of a high mortality rate in pregnant women. Chronic liver disease does not occur, and there is no prolonged carrier state. The test for HEV antibody is not readily available; the diagnosis is therefore typically made by excluding HAV and other causes. There is no antiviral treatment and no vaccine. In 2007, a recombinant vaccine against hepatitis E virus was shown to be safe and effective.
Which of the following is a killed vaccine? a) Hepatitis B b) Measles c) Yellow fever d) Japanese encephalitis
d) Japanese encephalitis Live viral vaccines MMR ; Yellow fever; Rota virus; Polio; Varicella; Influenza; adenovirus; small pox Polio - Both live and killed Influenza - Both live and Killed (purified subunits) Killed viral vaccines Hepatitis A; Rabies; Japanese encephalitis Subunit vaccine Hepatitis B There are two vaccines that contain live varicella-zoster virus: one that prevents varicella (Varivax) and another that prevents zoster (Zostavax)
HBV all true, except a) It is a DNA virus b) Spreads by blood transfusions c) HBs Ag marker of infection d) Least chance of chronicity
d) Least chance of chronicity
Which virus given below is not a teratogenic virus a) Rubella b) Cytomegalovirus c) Herpes simplex d) Measles
d) Measles
Regarding Hepatitis E true is a) Occurs with Hepatitis B b) Single stranded DNA virus c) Occurs along with HIV d) Mortality increased in pregnancy
d) Mortality increased in pregnancy
Infection with which of the following agents is particularly dangerous for anemic patients a) Adenovirus b) Cytomegalovirus c) Herpes simplex virus d) Parvovirus
d) Parvovirus
Rabies virus a) Can be isolated from the blood of infected patients b) Has multiple antigenic types c) Can be transmitted by a dog 4 weeks before the dog becomes noticeably ill d) Produce infection that is almost fatal to humans
d) Produce infection that is almost fatal to humans
Hepatitis D virus a) Transmitted by faecaoral route b) Is a DNA virus c) Has independent existence d) Resembles some plant viruses
d) Resembles some plant viruses
Choose the false statement regarding Hepatitis G virus a) Also called GB virus b) Blood born RNA virus c) Mostly infected with C virus d) Responds to Lamivudine
d) Responds to Lamivudine
All are prion diseases except a) Kuru b) Scrapie c) Crutz field Jakob disease d) SSPE
d) SSPE Subacute sclerosing panencephalitis (SSPE) is a rare, fatal disease of the central nervous system that occurs several years after measles.
All of the following diseases are mosquito borne except a) Japanese encephalitis b) Yellow fever c) Dengue fever d) Sleeping sickness
d) Sleeping sickness
Most common opportunistic infection in AIDS in India- a) Toxoplasmosis b) Crytococcosis c) Cryptosporidosis d) TB
d) TB
Von Magnus phenomenon a) Is a normal replicative cycle b) Virus yield has low hemagglutination c) VITUS has high infectivity d) Virus yields has high haemagglution titre but low infectivity
d) Virus yields has high haemagglution titre but low infectivity
Independent DNA replication occurs in all except: a) Bacteria b) Mitochondria c) Nuclei d) Viruses
d) Viruses
