Exam 1 Questions Flashcards
Are staphylococcus bacitracin susceptible or resistant?
Bacitracin resistant
What test differentiates between S. saprophyticus and S. epidermidis?
Novobiocin
S.sapro = resistant
S. epi = susceptible
Streptococcus spp. are catalase ___
Catalase negative
Group A Streptococcus is which species?
S. pyogenes
Which species of staph is coagulase positive?
S. aureus
Group B Streptococcus is which species?
S. agalactiae
Staphylococcus spp. are oxidase ___ and catalase __?
Oxidase negative
Catalase positive
Group D Streptococcus is which species?
S. bovis
Group D Non-Enterococcus is which species?
E. faecalis
Which Streptococcus species are beta hemolytic?
S. pyogenes (wide zone)
S. agalactiae (narrow zone)
Enterococcus spp.
Which Streptococcus species are alpha hemolytic?
S. pneumoniae
Viridans strep
Enterococcus
What is the gram stain morphology of Staphylococcus?
Gram positive (purple) cocci in clusters (grapelike)
What is the gram stain morphology of Streptococcus?
Gram positive (purple) cocci in chains
What is the next step if you have a negative slide coagulase test?
Coagulase Tube test to make sure its a true negative.
Explain the coagulase tube test and how it is performed
Tube coag. test tests for the free coagulase which is an extracellular enzyme. You add rabbit plasma and 2-4 colonies (1 loopful) of bacteria to clean tube. Incubate at 37 for 4 hours checking every hour. Positive = clumping
The slide coag. test tests for what?
Bound coagulase or clumping factor in the organisms cell wall
Which Streptococcus species is Bacitracin susceptible?
S. pyogenes (group A)
Beta-lactamase is a rapid screen for what organisms?
Staph spp. Enterococcus spp. and N. gonorrhoeae are all positive
What are the factors that influence effectiveness for a disinfectant?
Surface type, biofilm formation, number of organism, type of organism, pH, temperature
S. lugedunesis has what type of coagulase pattern?
Slide test positive
Tube test negative
What kind of nucleus does a Prokaryote have?
No nuclear membrane, no organelles
What is the reagent in the Beta-lactamase test and what does a positive reaction look like?
Cefinase disk, positive is a pink color
What kind of nucleus does a Eukaryote have?
Membrane-bound nucleus, has organelles
What kind of cell division does a eukaryote exhibit?
Mitosis
What does the plasma membrane of a Prokaryote have in it?
No carbohydrates, no sterols
What does the plasma membrane of a Eukaryote have in it?
Carbohydrates and sterols
How does a eukaryote sexually reproduce?
Meiosis
How does a prokaryote sexually reproduce?
conjugation
What kind of cell division does a prokaryote exhibit?
Binary fission
What kind of genetic material does a eukaryote have?
multiple, linear chromosomes
How do you sterilize glass pipettes?
Dry heat or autoclave
How do you sterilize mineral oil?
Dry heat
How do you sterilize empty petri plates?
UV radiation
How do you sterilize water?
Filtration or autoclaving
Which Streptococcus groups are PYR positive?
Group A (S. pyogenes) and Group D Enterococcus (E. faecalis)
What kind of genetic material does a prokaryote have?
single, circular chromosomes
Which Streptococcus groups are Bile Escuin positive?
Group D (S. bovis) and Group D Enterococcus (E. faecalis)
Is Micrococcus spp. bacitracin resistant or susceptible?
Susceptible
What is the purpose of Chocolate Agar?
Enriched, non-selective medium to isolate fastidious organisms like Neisseria and Haemophilus
What is the purpose of CNA agar?
Isolation of Gram positive bacteria. Colistin disrupts the cell membrane of gram negative bacteria inhibiting them, and also has antibiotics to inhibit the swarming of Proteus spp.
What is the CAMP test used for?
To identify if you have S. agalactiae. It tests for the CAMP factor which is a protein-like compound only produced by Group B strep. A characteristic arrow-head pattern appears when Group B is streaked perpendicularly to beta-hemolytic S. aureus.
What is the purpose of MAC agar?
A differential and selective media used to isolate gram negative bacteria and differentiate between lactose fermenters and non-lactose fermenters. Crystal violet and bile salts inhibit gram positive bacteria.
What is streptolysin?
Two toxins released by S. pyogenes, Streptolysin S and Streptolysin O. S is oxygen Stable, and O is destroyed by oxygen. The attribute to the virulence factor of S. pyogenes b/c they cause lysis of the rbc’s and they kill phagocytes.
What are the characteristics of autoclaving?
15 psi, 121 C, for 15 minutes
Which Streptococcus group is CAMP positive?
S. agalactiae (Group B)
What is the purpose of MTM agar?
To isolate N. memingitidis, and N. gonorrhoeae. It has vancomycin to inhibit gram pos. bacteria, Colistin to inhibit gram neg. bacteria other than those two specifically, Nystatin inhibits yeast and mold, and Trimethoprim lactate inhibits the swarming of Proteus.
Which carbohydrates are utilized by N. gonorrhoeae?
Glucose
Which carbohydrates are utilized by N. menigitidis?
Glucose and Maltose
Which carbohydrates are utilized by M. catarrahlis?
no sugars, DNAse positive
Which carbohydrates are utilized by N. lactamica?
Glucose, Maltose, and Lactose
Should you refrigerate Neisseria spp?
NEVER, they are fastidious and they need to be kept at room temperature and incubated in a capnophilic environment.
What is the gram stain appearance and morphology of Neisseria spp?
Gram negative (pink) diplococci
What is different about the Neisseria spp. that are pathogens versus the non-pathogen morphology
They are both diplococci but the pathogens are slightly elongated, almost kidney bean shaped while the non-pathogens are more rounded like true cocci
What is the sodium hippurate test used for?
Used to identify Group B strep, C jejuni and G. vaginalis. Hippurate is hydrolyzed by hippicurase to glycine and benzoate. Ninhydrin causes deamination of glycine to hydrantin, CO2 and ammonia. Condensation occurs with ninhydrin to form a purple comple.
What is transformation?
Cell dies and releases DNA into environment. This is followed by the DIRECT uptake of DNA fragments by the recipient cell.
Which diseases are caused by Moraxella spp?
Upper respiratory infections, otitis media (middle ear infections), sinusitis, pneumonia.
How does the Bile Esculin test work?
Esculin gets hydrolyzed to esculetin and dextrose. Esculetin reacts with iron from ferric citrate to form a black complex.
What is tetramethyl-p-phenylene-diamine-dihydrochloride?
Reagent in modified oxidase test. It acts an an electron donor for cytochrome C which is what is being tested for in the modified oxidase test. This reagent speeds up the reaction.
What is a plasmid?
Extrachromosomal small, circular, covalently bonded, double stranded DNA that is seperate from the nucleus. It carries the gene for enzyme production, pili, and exotoxin production.
What does the R plasmid code for?
Resistance to antibiotics
What is the selective media for N. gonorrhoea and N. meningitidis?
MTM (Modified Thayer Martin)
What does the F plasmid code for?
The production of the sex pilus
What is conjugation?
Involves two living cells with the sex pilus originating in the donor cell. A bridge is established as a way for DNA to transfer and a complementary strand is produced.
What test does the Bile Solubility test correlate with?
The optochin test
How does pasteurization work?
Keep the liquid at 63 C for 30 minutes. It achieves disinfection without sterilization.
The main function is to assist in bacterial attachment to host cells and/or mucosal surfaces.
Flagella or Fimbriae?
Fimbriae
The bacterial growth curve has 4 phases, what are they?
Lag phase, Log phase, Stationary phase, Death or decline phase
What extends from the cell membrane into the external environment?
Fimbriae
The main function is to rotate and cause motility. They are hollow, helical, proteinaceous tubes.
Flagella
What does halophilic mean?
capable of growing in high concentrations of salt
What originates in the cytoplasm and extends through the cell membrane and cell wall?
Flagella
True or False
Freezing inhibits growth but does not kill the bacteria
True
What is sodium desoxycholate?
The reagent in the Bile Solubility test. S. pneumonieae produces an autolytic enzyme that cleaves the bonds in the cell wall resulting in the dissolution of the cells.
What are examples of prokaryotes?
Bacteria- Eubacteria and archaebacteria
Psychrophiles like what temperature for optimal growth?
-10 to 20 C
Which organism typically has a site of 7-100 um diameter?
Prokaryote or Eukaryote?
Eukaryote
What is the capsule made out of and how does it help the virulence factor?
Composed of polysaccharides or polypeptides.
It inhibits phagocytosis from neutrophils and protects the cell from toxins and antibiotics
Mesophiles like what temperature for optimal growth?
10 to 50 C
Anaerobes lack which enzyme that makes oxygen toxic to them?
superoxide dismutase
The chemical method that uses halogens uses which halogens mostly?
Chlorine, in the form of 10% bleach solution
How do surfactants work?
Disrupts cell membranes, used on non-critical surfaces, does not kill spores, common in hospitals
What are the two enzymes that break down the end products of respiration?
Superoxide dismutase and catalase
Respiration gives rise to 2 toxic end products. What are they?
Superoxide anion O2- and hydrogen peroxide
How do phenolics work?
They precipitate proteins and disrupt cell walls, broad spectrum, biodegradable, household and hospital use, germicidal soaps
What is the thermal death time?
The minimum length of time in which all bacteria in liquid culture will be killed at a given temperature.
What is the thermal death temperature?
The lowest temperature at which all microorganisms die in a liquid suspension within 10 minutes
What is biosafety level 2?
Suitable for handling agetns of moderate potential hazard to personnel
Thermophiles like what temperature for optimal growth?
50-70 C
What is bacteriocidal mean?
The irreversible process by which an agent kills all bacteria and spores
What does bacteriostatic mean?
The reversible process that prevents growth but does not kill the bacteria
What does sterilization refer to?
The removal of all forms of life including spores
What is an antiseptic?
Essentially a disinfectant for living tissue
Why do cotton swabs interfere with certain tests?
The cotton swabs contain residual fatty acids that interfere
What does disinfection mean?
The killing of live organisms
What is biosafety level 3?
Suitable for handling potentially lethal pathogens that are spread through respiratory routes and can be inhaled, known cures exist.
What does microaerophilic mean?
The organism requires reduced levels of oxygen in order to grow.
What does capnophilic mean?
They grow better in atmosphere enriched with extra CO2 (5-10%)
What is a facultative anaerobe mean?
It can grow under aerobic or anaerobic conditons
What are aerotolerant anaerobes?
They are anaerobes but are not killed by exposure to oxygen
What does obligate anaerobe mean?
Cannot grow in the presence of oxygen
What does obligate aerobe mean?
Absolute requirement for oxygen
How does oxidation differ from fermentation?
The final hydrogen receptor for fermentation is an organic compound, not oxygen.
What is biosafety level 4?
Suitable for exotic or extraordinary diseases spread by aerosol or bloodborne routes with no known cure
What are the 3 glycolytic pathways?
Embden-Meyerhof-Parnas (EMP)
Pentose phosphate shunt
Entner-Douderoff
What are heterotrophs?
require complex substances for growth, organic carbon source required, energy from oxidation or fermentation
What are the 3 major nutritional needs for growth?
Carbon for making cellular compounds
Nitrogen for making proteins
Energy (ATP) for carrying out cellular functions
What is transduction?
DNA is introduced by a non-lethal virus. The bacteriophage infects bacteria and integrates DNA into the bacterial chromosome. When host bacteria dies its released. The newly infected cell recieves donor DNA
What does endogenote refer to?
cells original chromosome
What does exogenote refer to?
foreign DNA molecule
Genetic exchange in bacteria is accomplished by 3 basic mechanisms
Transformation, Transduction, Conjugation
What are autotrophs and the two subgroups?
They require CO2, H2O, and inorganic salts.
Phototrophs- derive energy from photosynthesis
Chemolithotrophs- derive energy form oxidation of inorganic compounds
Replication of ___ parent cells results in ___ daughter cells.
One parent, two daughter
What is biosaftey level 1?
Suitable for working with organisms that have no potential to cause human disease
0.01 mL loop uses factor of ___ to determine the number of organisms per mL
factor of 100
What does death phase mean?
Number of non-viable cells exceed the number of viable cells.
What kind of bacteria produce endospores?
Gram negative bacilli
What does the stationary phase mean?
Nutrients become limiting and toxic products accumulate
True or False
Endospores are a reproductive structure
False
What does the log phase mean?
Bacterial numbers increase logarithmically
What does lag phase mean?
Bacteria are preparing to divide
What are small, dehydrated, metabolically dormant forms of bacteria?
Endospores
What are the 3 vital functions of the cell wall
- Protects form osmotic pressure changes and lysis
- Serves as a barrier against toxic chemical and biological agents
- Rigid form gives cell shape
0.001 mL loop uses factor of ___ to determine the number of organisms per mL.
factor of 1000
What ar the 4 major functions of the cell membrane?
- Selective permeability and transport of solutes
- Electron transport and oxidative phosphoylation
- Excretion of exoenzymes
- Site of DNA synthesis
What does mesosome refer to?
Convoluted in-folding of cytoplasmic membrane
What are fimbriae of gram negative bacteria called?
Pili
What is ethylhydrocupreine hydrochloride?
An ingredient in the optochin test. Colonies of S. pneumoniae are selectively lysed. Lysis is indicated by a zone of inhibition after incubation under increased CO2.
How are the SXT test and Bacitracin tests used?
Group A strep are susceptible to bacitracin and resistant to SXT. Group B is resistant to both the bacitracin and SXT.
How is the modified oxidase/ furazolidone used?
It is used to differentiate between Staphylococcus and Micrococcus. This test is performed as a disk susceptibility procedure. Tests for cytochrome C. Staph are susceptible and Micrococcus are resistant.
What is the modified oxidase reagent?
DMSO Dimethylsulfoxide
What is L-pyrrolinodonyl-B-naphthylamide?
PYR. PYR tests for the ability of the organism to hydrolyze the substrate. After the inoculation of the disk hydrolysis of the substrate occurs forming beta-naphthylamide which produces a red color with the addition of the color developer p-dimethylcinnamaldehyde.
What does the PYR test differentiate between?
Enterococcus and Group A are PYR positive
S. bovis is negative
What is the optochin test used to differentiate between?
S. pneumoniae and other alpha-hemolytic Streptococci.
S. pneumoniae = positive or sensitive
All other alpha-hemolytic Strep are resistant
Enterotoxins cause what?
Food poisoning
What do exotoxins cause?
Scalded skin syndrome
What is the MSA agar used for?
Selective and differential media. Used for isolation and differentiation of Staph spp. MSA contains high levels of sodium chloride (7.5%) Most gram negatives and other gram pos spp cannot survive. S. aureus grows and ferments mannitol producing yellow colonies. Most coag-neg staph do not fement and grow as red colonies.
