Microbiologists (1) | Examples of questions help you solve the Saudi Commission for Health Specialties (SCFHS) questions

 Health Specialists

Microbiology Technologist

 References

Medical Microbiology, with STUDENT CONSULT. Murray, P. R., Rosenthal, K. S., and Pfaller, M. A..

Exam Blueprint

Evaluation Item	Content	Relative Percentage	Passing Score
(100 MCQs, 2 ½ hours)	Topics:
	1.     Lab Safety	7%	55%
	2.     Quality Control	5%
	3.     Ethics	3%
	4.     Bacteriology	30%
	5.     Virology	10%
	6.     Mycology	10%
	7.     Immunology	8%
	8.     Parasitology	10%
	9.     Mycobacteria	7%
Total		10%

Last Updated: Tuesday 21 February 2017

Medical Microbiology (1)

  Choose the most appropriate single answer.

    1.      All are Prokaryotic cells except:

a.      Fungi

b.      Bacteria

c.      Chlamydia

d.      Mycoplasma

(a) A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds. Bacteria constitute a large domain of prokaryotic microorganisms. Chlamydia is a genus of pathogenic bacteria that are obligate intracellular Gram-negative bacterium. Chlamydia is incorrectly called the PLT viruses, Bedsonia, or basophilic viruses. Mycoplasma is a genus of bacteria that are lacking a rigid cell wall during their entire life cycle, although they are also much smaller than bacteria.

    2.     Viruses:

a.      Contain only DNA or RNA

b.      They Contain ribosome

c.      Did not affected by antibiotics

d.      a&c

(d) Viruses are obligate intracellular parasite composed of:either DNA or RNA and Protein coat, The most effective medical approaches to viral diseases are vaccinations to provide immunity to infection, and antiviral drugs that selectively interfere with viral replication.

    3.     All of these are essential structure except:

a.      Nuclear body

b.      Spores

c.      Cell wall

d.      Plasma Membrane

(b) The basic cell structures such as nucleus, cell membrane, nucleolus, nuclear envelope, cytoplasm, mitochondria, vacuole, chloroplast, lysosomes, Golgi apparatus and ribosomes.

   4.     …………..is giving the shape to the bacteria

a.      Cytoplasmic Membrane

b.      Capsule

c.      Cell Wall

d.      All of the above

(c) The cell wall is the rigid, semi-permeable protective layer in some cell types. It found in most plant cells, fungi, bacteria, algae, and some archaea. Animal cells do not have a cell wall. It provides the cell with both structural support and protection, and acts as a filtering mechanism.

5.     One of its functions is selective permeability

a.      Cell wall

b.      Plasma membrane

c.      Capsule

d.      Spores

(b) The plasma membrane is thin, flexible barrier around a cell; regulates what enters and leaves the cell. It is present in both eukaryotic and prokaryotic cell. It is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.

6.     They are responsible for Haemagglutination Phenomenon

a.      Flagella

b.      Fimbria

c.      Capsule

d.      Cell wall

(b) Fimbria is an appendage that can be found on many Gram-negative and some Gram-positive bacteria that is thinner and shorter than a flagellum. Fimbriae are used by bacteria to adhere to one another and to adhere to animal cells and some inanimate objects. Haemagglutination is mediated by fimbriae.

7.     Clostridium Tetani is:

a.      Atrichous bacteria

b.      Mono-trichous bacteria

c.      Amphi-trichous bacteria

d.      Peri-trichous bacteria

(d) Clostridium tetani is a bacillus, or rod-shaped, bacterium. It is Gram positive, obligate anaerobe and commonly appears to be shaped like a drumstick or tennis racket when stained. C. tetani are motile bacteria and move around by the use of rotary peritrichous flagella.

8.     Short curved or straight rods, motile by single polar flagellum

a.      spirochaeta

b.      Vibrio

c.      Escherichia

d.      Lactobacillus

(b) Vibrio is a genus of Gram-negative bacteria, possessing a curved-rod shape (comma shape), facultative anaerobes, oxidase positive. The "typical", early-discovered Vibrio species, such as V. cholerae, have a single polar flagellum (monotrichous) with sheath. Some species, such as V. parahaemolyticus and V. alginolyticus, have both a single polar flagellum with sheath and thin flagella projecting in all directions (peritrichous), and the other species, such as V. fischeri, have tufts of polar flagella with sheath (lophotrichous)

9.     Small gram negative cocci, occur in pairs

a.      staphylococcus

b.      streptococcus

c.      neisseria

d.      Non of the above

(c) Neisseria species are Gram-negative bacteria and diplococci resemble coffee beans. Staphylococcus is a genus of Gram-positive bacteria. Under the microscope, they appear round (cocci), and form in grape-like clusters. Streptococcus is a genus of coccus Gram-positive nonmotile bacteria. The bacteria are grouped in chains that resemble a string of beads.

10.       Transfer of genetic information from one bacterium to another by bacteriophages is:

a.      Transformation

b.      Transduction

c.      Conjugation

d.      Mutation

(b) Transduction is the process by which DNA is transferred from one bacterium to another by a virus. It also the process whereby foreign DNA is introduced into another cell via a viral bacteriophage vector. Transformation is the modification of a cell or bacterium by the uptake and incorporation of extracellular DNA. In bacteria, conjugation is the direct transfer of DNA between two cells that are temporarily joined. Mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.

11.       Salmonella are:

a.      Obligatory Aerobic bacteria

b.      Obligatory Anaerobic bacteria

c.      Facultative Anaerobic bacteria

d.      Micro-aerophilic bacteria

(c) Salmonella is a genus of rod-shaped (bacillus) gram-negative, nonspore-forming, motile and facultative anaerobes bacteria of the Enterobacteriaceae family.

12.       According to pH, vibrio cholera is

a.      Osmophilic bacteria

b.      Alkalophilic bacteria

c.      Acidophilic bacteria

d.      Neutrophilic bacteria

(b) Alkaliphiles: “Alkali loving”. Grow at alkaline or high pH (7 to 12 or higher). Osmophile: Any organism that is a adapted to living in environments that have a high osmotic pressure. Acidophiles: “Acid loving”. Grow at very low pH (0.1 to 5.4). Neutrophiles:Grow at pH 5.4 to 8.5 which, including most human pathogens.

13.       Staphylococci are:

a.      Atrichous bacteria

b.      Mono-trichous bacteria

c.      Amphi-trichous bacteria

d.      Peri-trichous bacteria

(a) Atrichous: bacteria without flagella. Monotrichous: Single polar flagellum e.g. Vibrio cholerae, Campylobacter spp. Amphitrichous: Single flagellum at both ends e.g. Alcaligenes faecalis Lophotrichous: Tuft of flagella at one or both ends e.g. Spirilla spp. Peritrichous: Flagella surrounding the bacterial cell. e.g. Salmonella typhi and Escherichia coli.

14.       During replication of DNA, copying errors may occur and this is called

a.      Conjugation

b.      Transduction

c.      Transformation

d.      Mutation

(d) See the answer of question no. 10

15.       Obligatory Anaerobic bacteria

a.      Grow only in presence of oxygen

b.      Grow only in absence of oxygen

c.      Grow either in presence or absence of oxygen

d.      Grow in presence of oxygen traces and 5 – 10% CO₂

(b) Obligate Aerobes: Require oxygen to grow. Obligate Anaerobes: No growth in the presence of oxygen. Facultative Anaerobes: Bacterial growth with or without oxygen. Microaerophiles: Grow best in low concentrations of oxygen (as compared with the normal 21%).

16.       Neutrophilic bacteria grow well at

a.      pH 8.5 – 9.0

b.      pH 7.2 – 7.4

c.      pH 5.0 – 5.5

d.      pH 2.5 – 3.0

(b) See the answer of question no. 10

17.       The rate of cell death increase and bacterial growth stopped, this is

a.      Adaptation phase

b.      Exponential phase.

c.      Stationary phase.

d.      Decline Phase

(d) lag phase: The period of time the organisms need to adapt to the new environment, no growth but very active synthetic phase. Exponential phase: the cells have adjusted to their new environment and multiply rapidly (exponentially), the period of optimal population growth. Stationary Phase: The growth rate equals the death rate. There is no net growth in the organism population. Death Phase: The living organism population decreases with time, number of deaths exceeds the number of new cells formed.

18.       Beta-hemolytic

a.      Cause complete hemolysis of RBC’s

b.      Cause chemical change of Hemoglobin in RBC’s

c.      Do not cause hemolysis

d.      None of them

(a) Beta-hemolysis: is associated with complete lysis of red cells surrounding the colony, eg: Streptococcus pyogenes. Alpha-hemolysis: is a partial or “green” hemolysis associated with reduction of red cell hemoglobin, eg: Streptococcus pneumoniae.. Gamma hemolysis: is a lack of hemolysis in the area around a bacterial colony, eg: Enterococcus faecalis.

19.       Mesophilic bacteria grow at:

a.      37  °C

b.      14  °C

c.      60   °C

d.      120 °C

(a) Psychrophile: cold loving. Range 0C-20C. Mesophile: moderate temperature loving• Range 20C-40C•. Thermophile heat loving• Range 40C-100C.

20.       Circulation of Bacteria and its toxins in blood

a.      Pyaemia

b.      Toxemia

c.      Bacteremia - without toxins

d.     Septicemia

(d) Septicemia: The presence and multiplication of highly virulent bacteria accompanied by their toxins in the bloodstream. Pyaemia: is a form of septicaemia that leads to widespread abscesses, in which multiple small abscesses (pyemic abscesses) form in various organs as a result of impaction of septic emboli. Toxemia: The presence of microbial toxin (s) without the microbes themselves in the bloodstream Bacteraemia: The presence of bacteria in the blood stream without multiplication.

21.     Disinfections that applied on living or injured tissues:

a.      Sterilization

b.      Antiseptic

c.      Sanitation

d.      Decontamination

(b) Antisepsis: Reduce the number of microorganisms on the skin surface, it refers to chemical disinfection of the skin, mucous membranes, or other living tissues. Sterilization:is the process of destroying or removing all forms of microbial life on an object or in a material, including the destruction of endospores. Decontamination: the use of physical or chemical means to remove, inactivate, or destroy blood borne pathogens from a surface. Sanitation: is the hygienic means of promoting health through prevention of human contact with the hazards of wastes as well as the treatment and proper disposal of sewage or wastewater.

   22.      Hot air oven is used for sterilization of

a.      Glass

b.      Rubber Gloves

c.      Plastic Syringes

d.     Catheters

(a) Hot Air Oven: used to sterilize glass materials forceps, scalpels, etc… Autoclaving is most suitable for culture media, aqueous solutions, decontamination of discarded cultures and specimens, rubber items such as gloves, stoppers with rubber liner, glass ware with attached rubber tubings such as transfusion sets, glass metal syringes, etc.

   23.      Disinfectant for superficial fungal infection

a.      Phenol

b.      Potassium permanganate

c.      Chlorine

d.      Hypochlorite compounds

(a) Potassium permanganate: Antiseptic for superficial skin fungus infections. Phenol (5%):Disinfectant for external surfaces, non-living, Chlorine: is one of the most commonly used disinfectants for water disinfection. Hypochlorites (0.5%) (Chlorox): Disinfectant for external surfaces, non-living

24.       Rifampin

a.      inhibit cell wall synthesis

b.      inhibit protein synthesis

c.      inhibit folic acid pathway

d.      inhibit mRNA synthesis

(d) Rifampin :Example: Rifadin. Prevents the synthesis of bacteria messenger RNA, broad spectrum and used in tuberculosis therapy and also to treat the contacts of bacterial meningitis.

25.       Transacetylase inactivate

a.      aminoglycosides

b.      chloramphenicol

c.      penicillin

d.      cephalosporins

(b) Transacetylase (or Acetyltransferase) is a type of transferase enzyme that transfers an acetyl group. For example: Chloramphenicol acetyltransferase, this enzyme is a bacterial enzyme that detoxifies the antibiotic chloramphenicol and is responsible for chloramphenicol resistance in bacteria.

26.       The color of gram positive bacteria is

a.      Yellow

b.      Black.

c.      Pink

d.     Violet

(d) Gram Staining is the common, important, and most used differential staining techniques in microbiology. The Gram stain based on the differences in the chemical and physical properties of the cell wall. Gram positive: Stain dark purple or violet, eg: Staphylococcus aureus. Gram negative: Stain red or pink, eg: E. coli.

27.       Selective media for fungi

a.      blood agar

b.      Mac Conkey agar

c.      Nutrient agar

d.      Sabourand’s dextrose agar

(d) Sabouraud agar is a type of agar growth media containing peptones. It is used to cultivate dermatophytes and other types of fungi, and can also grow filamentous bacteria such as Nocardia. It is sufficient for the recovery of dermatophytes from cutaneous samples and yeasts from vaginal cultures.

28.       Histoplasma is a :

a.      Systemic mycosis

b.      Sub – Cutaneous mycosis

c.      Cutaneous mycosis

d.      Superficial mycosis

(a) Mycosis: Any fungal disease. Systemic mycoses: Fungal infections deep within the body. Can affect a number of tissues and organs. Usually caused by fungi that live in the soil and are inhaled. Not contagious. Example: Histoplasmosis (Histoplasma capsulatum): Initial infection in lungs. Later spreads through blood to most organs.

29.       All are asexual spores produced by mould except

a.      Conidiospores

b.      Sporangiospores

c.      Endospores

d.      Arthrospores

(c) Endospore found in gram-positive bacteria Bacillus and Clostridium highly durable dehydrated cells with thick walls.The two most common types of asexual reproductive spores produced by molds are conidiospores and sporangiospores. Arthrospores (arthroconidia) – Formed by fragmentation of septate hyphae into single cells.

30.       They reproduce only by Asexual reproduction

a.      Blastomyces

b.      Deuteromycetes

c.      Ascomycetes

d.     Zygomycetes

(b) A large number of fungi reproduce sexually. However, the members of Fungi Imperfecti, or ‘Deuteromycetes’ lack sexual reproduction. Blastomyces dermatitidis itself is a sexual organism, occurring in nature as both a + mating type and a − mating type. Ascomycetes: They can reproduce either asexually by budding ( or sexually forming ascospores). Zygomycetes: They can reproduce either asexually or sexually.

31.       The functions of cell wall is all of the following except:

a.      Giving the shape to the bacteria

b.      Carrying somatic antigen

c.      Selective permeability& transport of solutes = plasma membrane

d.      Protect the bacteria from plasmolysis

(c) The cell membrane (not cell wall) is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.

32.       Atrichous Bacteria are:

a.      Bacteria contain one flagellum

b.      Bacteria contain 2 flagella

c.      Bacteria without flagella

d.      Bacteria with a tuft of flagella

(c) See the answer of question no. 13

33.       ……………. are essential for host cell attachment:

a.      Flagella

b.      Fimbria

c.      Spores

d.      Capsules

(b) See the answer of question no. 6

34.       Irregular clusters of spherical cells:

a.      Streptococcus

b.      Staphylococcus

c.      Lactobacillus

d.      Escherichia

(b) See the answer of question no. 9

35.       Clostridium Botulinum is:

a.      Obligatory Aerobic Bacteria

b.      Facultative Anaerobic Bacteria

c.      Obligatory Anaerobic Bacteria

d.      Micro- aerophilic Bacteria

(c) See the answer of question no. 15

36.       Basophilic Bacteria grow well at:

a.      pH 8.5 – 9.0

b.      pH 7.2 – 7.4

c.      pH 5.0 – 5.5

d.      None of the above

(a) See the answer of question no. 12

37.       Cells are divided at high & constant rate:

a.      Decline Phase

b.      Stationary Phase

c.      Log Exponential Phase

d.      Adaptation Phase

(c) See the answer of question no. 17

38.       The dominant bacterial species in dental plaque are:

a.      Coagulase Negative Staphylococci

b.      Lactobacillus

c.      Bacteroides

d.      Streptococcus Sanguis

(d) Dental plaque is a biofilm or mass of bacteria that grows on surfaces within the mouth. It is a sticky colorless deposit at first, but when it forms tartar, it is often brown or pale yellow. It is commonly found between the teeth. The dominant bacterial species in dental plaque are Streptococcus sanguis and Streptococcus mutans, both of which are considered responsible for plaque.

39.       The spread of Pyogenic Bacteria in blood stream to different organs & produce multiple abscess is:

a.      Septicemia

b.      Bacteremia

c.      Toxemia

d.      Pyaemia

(d) See the answer of question no. 20

40.       Inhibit the growth of micro organisms

a.      Bacteriostatic

b.      Bactericidal

c.      Fungicidal

d.      Germicidal

(a) Bacteriostatic: inhibits bacterial growth. Bactericidal is a substance that kills bacteria. Fungicides are biocidal chemical compounds or biological organisms used to kill fungi or fungal spores. Germicidal: A substance or agent that kills germs, especially pathogenic microorganisms.

41.       To sterilize fluid damaged by heat:

a.      Gaseous Sterilization

b.      Heat Sterilization

c.      Filtration

d.      Ionizing Radiation

(c) Sterilization referring to any process that eliminates, removes, kills, or deactivates all forms of life and other biological agents (such as fungi, bacteria, viruses, spore forms, prions, unicellular eukaryotic organisms such as Plasmodium, etc. Fluids that would be damaged by heat, irradiation or chemical sterilization, such as drug products, can be sterilized by microfiltration or nanofiltraton using membrane filters.

42.       For water disinfection we use:

a.      Hydrogen peroxide

b.      Formaldehyde

c.      Chlorine

d.      Hypochlorite compounds

(c) Water disinfection can be performed with various disinfants. Chemical disinfectants are chemical substances, which are used to kill or deactivate pathogenic microorganisms. Examples are:Chlorine, Sodium hypochlorite, Chlorine dioxide, Chloramines, Hydrogen peroxide and Bromine. Chlorine is one of the most commonly used disinfectants for water disinfection. Chlorine can be applied for the deactivation of most microorganisms and it is relatively cheap.

43.       Mechanism of action of penicillin:

a.      Block peptidoglycan synthesis

b.      Inhibit peptidoglycan cross – linking

c.      inhibit folic acid pathway

d.      inhibit protein synthesis

(b) Penicillin is a group of antibiotics which include penicillin G (intravenous use), penicillin V (use by mouth), procaine penicillin, and benzathine penicillin (intramuscular use). Penicillin antibiotics are effective against many bacterial infections caused by staphylococci and streptococci. Penicillins and other antibiotics in the beta-lactam family contain beta-lactam ring. Penicillin kills bacteria through binding of the beta-lactam ring to DD-transpeptidase, inhibiting its cross-linking activity and preventing new cell wall formation. Penicillins, and other beta-lactam antibiotics, work by interfering with interpeptide linking of peptidoglycan. Cell walls without intact peptidoglycan cross-links are structurally weak.

44.       Sulfonamides:

a.      inhibit cell wall synthesis

b.      inhibit protein synthesis

c.      inhibit DNA synthesis

d.      inhibit folic acid pathway

(d) The original antibacterial sulfonamides are synthetic antimicrobial agents that contain the sulfonamide group. Antibacterial sulfonamides act as competitive inhibitors of the enzyme dihydropteroate synthase (DHPS), an enzyme involved in folate synthesis. Sulfonamides are therefore bacteriostatic and inhibit growth and multiplication of bacteria not bactericidal.

45.       Which of the following have characteristic intracellular inclusion bodies?

a.      Candida

b.      Chlamydia

c.      Escherichia

d.      Mycoplasma

e.      Rickettsia

(c) Inclusion bodies, are nuclear or cytoplasmic aggregates of stainable substances, usually proteins. Inclusion bodies are dense electron-refractile particles of aggregated protein found in both the cytoplasmic and periplasmic spaces of E. coli during high-level expression of heterologous protein.

46.       Ringworm disease is caused by

a.      Zygomycetes

b.      Ascomycetes

c.      Blastomycosis

d.      None of the above

(b) Ringworm, also known as dermatophytosis, is a fungal infection of the skin. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affected. Dermatophytes are a common label for a group of three types of fungus that commonly causes skin disease in animals and humans. These anamorphic genera are: Microsporum, Epidermophyton and Trichophyton. There are about 40 species in these three genera. Species capable of reproducing sexually belong in the teleomorphic genus Arthroderma, of the Ascomycota.

    47.  ………… preparation is used for the rapid detection of fungal elements in clinical specimen

a.      NaOH

b.      K OH

c.      H₂ O₂

d.      All of the above

(b) The KOH Test, or potassium hydroxide preparation is a quick, inexpensive fungal test to differentiate dermatophytes and Candida albicans symptoms from other skin disorders like psoriasis and eczema. it clears the specimen making fungal elements more visible, so that the hyphae and conidia (spores) of fungi can be seen during direct microscopic examination.

48.       In the past they were listed as large viruses

a.      Richettsia

b.      Mycoplasma

c.      Chlamydia

d.      None of the above

(c) The chlamydia, which are incorrectly called the PLT viruses or Bedsonia or basophilic viruses, are bacteria which are obligate intracellular parasites of higher animals. They are not transmitted by arthropods. The rickettsia are bacteria which are obligate intracellular parasites. They are considered a separate group of bacteria because they have the common feature of being spread by arthropod vectors (lice, fleas, mites and ticks). The cells are extremely small rod-shaped, coccoid and often pleomorphic which have typical bacterial cell walls, no flagella, are gram-negative and multiply via binary fission only inside host cells. The mycoplasma are extremely small free-living bacteria which lack a cell wall and cytochromes. Mycoplasma can be cultured on agar media but colonies take up to three weeks to develop. Mycoplasma pneumoniae is transmitted (spread) from person-to-person.

49.       They are transmitted by arthropods

a.      Chlamydia

b.      Spirochetes

c.      Mycoplasma

d.      All of the above

(b) Spirochetes are a group comprised of six genera of bacteria. They are named because of their spiral shape. Under the light or electron microscope , the tight coiling that is characteristic of spirochetes is readily visible. Spirochetes are a significant health threat to humans. Both syphilis and Lyme disease are caused by spirochetes. Blood-feeding arthropods transmit numerous types of infectious agent and parasite. These vector-borne pathogens transmitted by ticks, mites, and hematophagous insects. These ticks are the respective vectors of the Lyme disease spirochete Borrelia sp. See also anewer of question no. 48

50.       Bacteria multiply by:
                 a.      Replication cycle
                 b.      Simple binary fission
                 c.      Sexual reproduction
                 d.      All of the above

(b) Bacteria multiply through binary fission. This process involves the division of a single cell into two identical daughter cells, and it starts when the DNA of a bacterium divides into two replicates. The bacterial cell splits into two daughter cells that have identical DNA to the parent cell.

Continued