Microbiology 2008 Flashcards
Organisms that utilize only the fermentative pathways in their metabolism are known as:
anaerobes
At which stage in the growth of a bacteria is there a slow loss of cells through death that is just balanced by the formation of new cells through growth and division.
lag phase
Bacteremic shock is triggered by
endotoxins
The toxic property of endotoxin lies in the
lipid A
Which of the following components of a bacterial cell wall is susceptible to lysozyme?
peptidoglycan
The primary difference between Gram positive and Gram negative bacteria lies in the
cell wall
Koch’s postulate states the following except
A. The organism must be isolated in pure culture. / B. It must produce the same disease when pure culture is inoculated into experimental animal. / C. The organism must be recovered in pure culture from the experimentally infected animals. / D. The disease must be reproduced in susceptible animals by inoculation of cell-free products of microbial growth.*
Answer: The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
The microorganism must be isolated from a diseased organism and grown in pure culture.
The cultured microorganism should cause disease when introduced into a healthy organism.
The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
One of the following is the appropriate sample for the isolation of Salmonella typhi during the first week of a suspected cases of typhoid fever
blood
Which of the following is not true for E. coli?
can cause meningitis in neonates
The most frequently isolated type of H. influenzae in cases of bacterial meningitis in children between 6 months to 2 years is
serotype b
Which is the incorrect statement concerning gonorrhea?
The definitive diagnosis can be made by detecting at least a 4-fold rise in antibody titer to N. gonorrheae.
The vaccine currently used for the prevention of S. pneumoniae is made from
capsular polysaccharides from 23 S. pneumoniae serotypes
Which of the following tests is more specific in the diagnosis of syphilis?
TPHA (Treponema Pallidum Hemagglutination Test)
The tubercle, a lesion in tuberculosis, is characterized by
bacilli surrounded by lymphocytes and fibroblasts
The following are some general characteristics of Mycobacterium leprae except
A. acid fast rods / B. humans are the only significant reservoir / C. can be grown readily in the laboratory using either artificial media or cell culture* / D. cell wall has high lipid content
The pathogenesis of Mycobacterium tuberculosis follows certain norms. Which of the following statements is not true?
A. Mycobacterium tuberculosis produces an exotoxin and contains an endotoxin in its cell wall.* / B. Reactivation is seen primarily in debilitated or immunocompromised patients. / C. The primary lesion usually appears in the lungs. / D. Dissemination may be by bloodstream or erosion of tubercle and spread to contagious areas.
The diagnosis of chickenpox can be done by
A. symptomatology, including characteristic appearance of lesions / B. Serology / C. Tzanck’s smear / D. All of the above*
A 21-year old female patient came to you complaining of profuse vaginal discharge with finshy odor and itching of the vulva. Examination of the discharge showed vaginal epithelial cells that contain tiny pleomorphic bacilli within the cytoplasm (clue cells). The pathogen involved is
Gardnerella vaginalis
A characteristic “rose spots” may appear in the second to the third week of this disease.
Typhoid fever
Which of the following would best describe disinfectants and antiseptics?
Disinfectants are used in inanimate objects while antiseptics are used for living forms like human tissues.
The essential antigen in pneumococcus that protects the organism from phagocytosis and is used to classify the organism into specific antigenic types is
capsular polysaccharide
The isolation and identification of Staphylococcus epidermidis from one bottle of a series of three blood cultures most likely indicates which of the following conditions?
staphylococcal contamination
Which specimen should not be refrigerated after collection even if it cannot be processed at once?
blood
Coagulase test is used to classify
Staphylococci
CSF is collected in three vials for laboratory examination. Which vial should not be used for bacteriology?
vial 1
The incubation period of influenza is commonly
2 – 4 days
The etiologic agent of about 90% of post-transfusion hepatitis is
Hepatitis C
The hepatitis profile done on a patient showed a HbsAg negative, IgM core antibody negative and Hbs antibody positive results. What would be the best interpretation for these results?
The patient is immune to Hepatitis B.
Which of the following is not a contraindication for administering a live attenuated viral vaccine?
administration of another live vaccine
Hepatitis C poses a big challenge in clinical practice because of the
A. presence of genetic subtypes that present with different pathogenic mechanisms. / B. difficulty in developing vaccines due to the genetic heterogeneity and possible antigenic variability. / C. problems in laboratory diagnosis due to possible antigenic variability among genetic types / D. all of the above*
Core window phase in HBV infection means
positive for anti-HBe and anti-Hbc antibodies
The presence of transient rashes among dengue patients has been observed to be a prognostic sign associated with
mild illness and recovery
The presence of antibodies against the primary cause of dengue infection means
protection against the infecting serotype for a long time
The cause of shock in dengue and other hemorrhagic fevers is
A. partly due to the virus / B. largely due to immune-mediated damage of virus-infected cells / C. both A and B are correct*
The problem of cross infection with different serotypes of dengue relates to
A. difficulties in developing a safe vaccine / B. difficulty in establishing diagnosis / C. both A and B are correct*
Mycobacterium tuberculosis is an acid fast organism and this is due to which of the following
mycolic acid
Acute bronchiolitis is common in the first 2 years of life and results from inflammatory obstruction of the small airways. The most common causative agent is
Respiratory syncytial virus
Blue green pus in wounds and burns is due to
Pseudomonas aeruginosa
A 23-year old pregnant woman decided to continue with her pregnancy even when she tested positive for anti-rubella IgM on the 8th week of gestation. Which of the following findings will indicate congenital rubella?
anti-rubella IgM in the baby
Which of the following statements on poliomyelitis is false?
A. Poliomyelitis may be transmitted via droplet or fecal-oral route. / B. Among the poliovirus strains, type 1 is the paralytogenic. / C. The oral polio vaccine is safe to give even to the immunocompromised.* / D. The Philippines, along with the other countries of the Western Pacific Region, was declared Polio-free in 2000.
Koplik’s spots are pathognomonic of
measles
A 30-year old woman undergoing chemotherapy for acute lymphocytic leukemia came to the OPD complaining of small vesicular eruptions across her left breast. The eruptions progressed to ulceration and crushed pustules. She has similar experience about a year a before. This person could be suffering from
shingles
A 22-year old male complained of sore throat with fever and lymphadenopathy. There is lymphocytosis with a typical cell agglutination. The probable diagnosis is
infectious mononucleosis
Infection from Mycobacterium avium intracellulare are often seen in AIDS patients. The following are attributes of pathogenicity for this except
Cell wall is entirely different from M. tuberculosis.
Which of the following appendages is involved in the transfer of DNA during bacterial conjugation?
fimbriae
The following are true of Group B streptococci except
A. They are precipitated with streptococcus agalactiae antisera. / B. They are an important causative organism of neonatal sepsis. / C. An effective vaccine against the organism incorporates proteinaceous capsular antigen.* / D. They are part of the vaginal flora.
A 30-year old man had knee surgery following a car accident. A few days after the surgery, the suture line was noted to be infected. Lab report showed Gram positive coccus, coagulase positive, catalase positive and beta hemolytic. The organism is
Staphylococcus aureus
The following are four important genera of Gram positive rods. Which one among them is anaerobic?
A. Corynebacterium / B. Clostridium* / C. Listeria / D. Bacillus
Which of the following statements is NOT true of typhoid fever/Salmonella typhi?
Salmonella typhi may be considered part of the normal flora of humans.
Bacterial capsules are protective walls that surround the cell membranes. Which of the following is NOT true about bacterial capsules?
A. produced by both Gram positive and Gram negative bacteria / B. usually composed of simple sugar residues except Bacillus anthracis whose capsule is of amino acid residues / C. capsule production is not influenced by environment and cultural conditions* / D. capsules maybe visualized by India ink stain
The following diseases are caused by exotoxins produced by the etiologic agent except
A. Tetanus / B. Gonorrhea* / C. Anthrax / D. gas gangrene
The following statements refer to endotoxin except
A. Endotoxin is also commonly referred to as lipopolysaccharide. / B. Endotoxin is produced exclusively by Gram negative bacteria.* / C. Listeria monocytogenes can produce endotoxin. / D. It is heat stable compared to the more heat labile exotoxins.
Which of the following characteristics is unique for HIV?
Presence of two molecules of the viral genome
Which among the following generalizations is NOT true?
A. All RNA viruses have linear genomes. / B. DNA viruses replicate in the cytoplasm except poxviruses.* / C. RNA viruses with helical symmetry are enveloped. / D. The nucleic acid of DNA viruses are double-stranded except parvoviruses.
The cell tropism of a virus is dictated by
host cell receptors
The viral replication step that constitutes the eclipse period in the viral one-step growth curve is
uncoating
The way virus enters and exits a host cell depends on the
type of outer covering
The large external domain of the viral envelope has the following functions except
A. contains binding sites for cell surface virus receptors for attachment / B. contains major antigenic determinants / C. often essential for viral assembly* / D. mediates fusion of viral with cellular membrane entry
Viruses are the smallest infectious agent. The following are distinctive characteristics of the viruses except
A. viruses are very sensitive to the usual antibiotics* / B. viruses replicate from their own genetic material / C. viruses are obligate intracellular parasites / D. viruses contain only a single type of nucleic acid as their genome
Viral nucleic acid may be
A. single stranded or double stranded / B. RNA or DNA but not both / C. linear or circular / D. all of the above*
Enveloped viruses are sensitive to substances that
dissolve the lipid membrane
The sequential steps in productive viral infection are
adsorption-entry-eclipse-assembly-release
Antiviral therapy is difficult to develop because
viruses use host cell systems to replicate
Which of the following viral architectures can lead to an abortive type of infection?
icosahedral symmetry
The release of progeny enveloped viruses usually involves
budding through cell membrane
An important characteristic of DNA viral infections is that they usually result in
latency
A method that can be used both in the detection of viral antigens directly in clinical specimens and as a confirmatory test for the viral isolates from cell culture
Immunofluorescence test
Interferons produced following viral infection include
A. alpha IFN / B. beta-IFN / C. gamma IFN / D. all of the above*
The virus plaque is analogous to the
virus titer
Some viruses cause cancer attributed to the presence of oncogenes. Which of the following is not an example of this?
A. Hepatitis B virus / B. Epstein Barr virus / C. Human papilloma virus / D. Hepatitis A virus*
A 7-year old girl consulted the OPD due to scaly inflammatory patches on the scalp. The condition started 3 weeks prior to consult and progressed to redness and local swelling. The hair fluoresced under Wood’s light and primary smears of skin and hair contained septate hyphae. On social history, it was reported that that the child is fond of playing with their pet dogs. Which of the following is the most probable etiologic agent?
A. Microsporum audouinii / B. M. canis* /C. Trichophyton rubrum / D. T. tonsurans
Trichophyton mentagrophytes produces this enzyme that is capable of perforating the hair shaft.
keratinase
A 27 year old gym instructor consulted the OPD due to white patches on his shoulder. He noticed these after coming back from a vacation in Boracay. He also complained of itchiness and scaling in the area. The most probable etiologic agent is
A. Malassezia furfur*/ B. Microsporon gypseum / C. Trichophyton rubrum / D. Exophiala wernickii
The following is/are characteristics of superficial mycoses
A. lacks immune response from the host / B. no invasion of living tissue / C. infection is innocuous / D. all of the above*
The following describes the causative agent of Pityriasis versicolor EXCEPT
A. lipophilic yeast / B. disease causation is associated with its overgrowth / C. not part of the skin flora* / D. none of the above
Which of the following cutaneous fungi causes dermatomycosis
A. Microsporon canis / B. Trichophyton rubrum / C. Candida albicans* / D. Malassezia furfur
Dermatophytes have the following characteristic/s
A. produces keratinases / B. limited to non living tissue / C. pathologic changes occur / D. A and C only / E. all of the above*
Enterobacteriaciae is composed of several bacteria having similar characteristics, which of the following best describes this group?
All are oxidase negative.
The enteric bacteria that can cause gastroenteritis and which is exclusively transmitted by humans is:
Shigella dysenteriae
The examination of stool may suggest the mechanism of disease caused by the different enteric microorganisms. The presence of pus cells and RBCs highly suggest:
invasion of the epithelium
All the following statements illustrate the difference between SARS and Influenza EXCEPT
A. SARS can be transmitted by fecal-oral route other than by close contact. / B. SARS cases are prevalent in older age group compared with influenza which can affect all ages. / C. The best time to collect a specimen for virus isolation of SARS-CoV is during the second week of illness instead of the first week which is the usual for influenza diagnosis. / D. A suspect case for both diseases is defined by the clinical characteristics and laboratory evidence.*
Which among the factors below limit the laboratory diagnosis of enteric viruses?
A. absence of antiviral agents / B. self-limiting nature of viral infections / C. short incubation period / D. all of the above*
RNA viruses are prone to mutation. This characteristic is augmented for some RNA viruses like influenza because of
genome segmentation
The most common human exposure unit in fungal exposures:
spores
The culture media for Neisseria is a chocolate agar Thayer Martin medium to which antibiotics are added to kill competing organisms and fungi except Neisseria. Which of the following antibiotics is not added?
A. Nystatin / B. Polymyxin / C. Vancomycin / D. Chloramphenicol*
Which of the following organisms has no cell wall?
A. Spirochetes / B. Mycobacteria / C. Chlamydia / D. Mycoplasma*
Among the opportunistic mycoses, the fungi that will change its morphology in tissue is:
A. Aspergillus fumigatus / B. Crytococcus neoformans / C. Histoplasma capsulatum*/ D. Sporothrix schenckii
The following are characteristics of systemic mycoses except
A. Primary infection is usually respiratory. / B. Host response involves mainly humoral immunity.*/ C. Most agents are dimorphic fungi. / D. Generally, infection requires large inoculom.
Microscopic morphology of T. mentagrophytes is characterized by:
A“en grappe” microconidia
All of the following fungal structures can be seen in tissues EXCEPT
A. broad-septated hyphae / B. cigar bodies / C. sclerotic bodies / D. Macroconidia*
The hallmark of mycetoma
granules
“Cauliflower” like lesions are seen in
Chromoblastomycosis
The presence of dichotomously branching hyphae in tissue:
Aspergillosis
The pulmonary symptoms caused by this agent mimics tuberculosis
Blastomyces dermatitidis
A 30-year old male has been receiving clindamycin for an anaerobic infection. He developed intractable diarrhea with abdominal pain. Colonoscopy showed yellow white pseudomembranes and an exotoxin was detected in the stool. We are probably dealing with
Clostridium difficile
This is a low virulent Gram negative bacteria that does not contain lipid A in its outer membrane but possesses a capsule
Bacteriodes fragilis
The “common cold” syndrome has been associated with several viral agents. Which of the following viruses is not associated with this syndrome?
A. Rhinovirus / B. Variola* / C. Coronavirus / D. Adenovirus
A 5-year old presents with acute pharyngitis with yellowish exudate, regional lymphadenopathy and often a high fever. Laboratory diagnosis reveals a beta-hemolytic organism which is inhibited by bacitracin. What is the etiologic agent fo this infection?
Streptococcus pyogenes
Viruses with this type of genome are generally infectious even when uncoated.
(+) single stranded RNA
