Bacteriology Flashcards
What three groups of molecules are found in cytoplasm?
- ) Macromolecules - proteins (enzymes), mRNA, tRNA
- ) Small molecues - energy sources, precursors of macromolecules, metabolites or vitamins
- ) inorganic ions - such as co-factors.
what is included in the protein component of the bacterial chromosome (nucleoid)?
- ) Transcription Factors - regulate bacterial genome.
2. ) Nucleoid-associated proteins (NAPs) - carry out the dynamic spatial organization of the nucleic acid.
All bacteria cytoplasmic membrane is composed of ___ & ____? What is the difference with regards to mycoplasmas?
Phospholipid bilayer and proteins. Sterols are only present in mycoplasmas
Where does bacterial respiration occur?
Across the cytoplasmic membrane.
What types of substances can pass a phospholipid bilayer via passive diffusion?
small lipid-soluble compounds
What is peptidoglycan and where is it found?
Peptidoglycan is a polymer of disaccharides cross-linked by short chains of amino acids (peptides). It is found in the cell envelope of bacteria.
What is unique about the cell wall of gram-positive bacteria?
Thick layer of murein (aka: peptidoglycan) and techoic acids.
What is the function of techoic acids found in the cell wall of ____ bacteria?
provides rigidity in gram positive bacteria.
What is unique about gram-negative bacteria cell envelope?
Composed of a thin layer of murein/peptidoglycan surrounded by an outer membrane.
What are the components of the outer membrane of gram-negative bacteria cell wall?
Lipopolysaccharides (LPS or endotoxins) and porins.
What are porins and where are they found?
Porins are proteins allowing diffusion of hydrophilic molecules into the periplasmic space of gram-negative bacteria. They are found in the cell envelope of gram-negative bacteria.
What is periplasmic space?
The space between the cell envelope and cytoplasmic membrane of bacteria.
What is the function of the capsule (AKA: glycocalyx) in bacteria?
Mediates attachment to particular surfaces and protects bacteria from engulfment.
Fimbriae
Shorter and stiffer than flagella and are usually involved in adherence to surfaces.
Monotrichous
Flagellar arrangement in which one flagella is present
Lophotrichous
Flagellar arrangement in which multiple flagella are present originating from one area of the cell wall
Peritrichous
Flagellar arrangement in which multiple flagella are arising from multiple areas around the periphery of the cell wall.
Amphitrichous
Flagellar arrangement in which one flagella arises from each pole.
Germination
The reverse of sporulation.
What are the main genera of spore-forming bacteria?
Bacillus and Clostridium
In what group relative to oxygen requirement for growth do most clinically relevant bacteria fit in?
Facultative anaerobes - they prefer to reside in areas with oxygen but can survive in anaerobic conditions also.
Define antibiotic.
An antimicrobial chemical substance that is produced by microorganisms
Define growth-promotion use of antimicrobials in animals.
When healthy animals are treated with low (sub-therapeutic) concentrations in feed to improve growth rate and efficiency of feed utilization and improve reproductive performance.
Drugs that end with -illin are ___.
Penicillins
Drugs that end in -cline are ___.
Tetracyclines
Drugs that end in -oxacin are __.
Quinolones (exception: oxolinic acid is also a quinolone).
Drugs that end in -enicol are ___.
Phenicols
Drugs that begin with cef- are ___.
Cephalosporins
What groups of drugs would be a good choice for gram-positive bacterial infections?
Penicillins, Aminopenicillins, Amoxicillin/clavulanate, Cephalosporins.
Which groups of drugs would be active against penicillase-producing staphylococci?
Amoxicillin/clavulanate, Cephalosporins, Fluoroquinolones
Which groups of drugs are active against gram-negative rods?
Amoxicillin/clavulanate, Cephalosporins (3/4 generation), Fluoroquinolones, Aminoglycosides
Which groups of drugs would be active against anaerobes?
Penicillins, Aminopenicillins, Lincosamides, Metronidazole, Amoxicillin/clavulanate
What three groups of antimicrobials are beta-lactams?
Penicillins, Cephalosporins, Carbapenems
Symbiotic mutualism
Both are necessary (host and bacteria) and the relation is positive for both.
Symbiotic commensalism
Good for one, no problem for the other (i.e. intestinal flora)
Symbiotic parasitism
One takes advantage of the other.
Balanced pathogenicity
Damage with recovery.
Which group of bacteria most often have flagella (gram positive or gram negative)?
Gram negative
What are exotoxins?
Bacterial metabolites released by bacteria that interfere with normal cell function in surrounding cells.
What are the characteristics of Type I endotoxins?
Binds with a cell receptor and leads to disturbances of cellular metabolism.
What are the characteristics of Type II endotoxins?
Causes cell wall damage
What are the characteristics of Type III endotoxins?
Intracellular toxins: one part binds to the membrane, the other part enters the cell.
Balanced pathogenicity
Damage with recovery.
Which group of bacteria most often have flagella (gram positive or gram negative)?
Gram negative
What are exotoxins?
Bacterial metabolites released by bacteria that interfere with normal cell function in surrounding cells.
What are endotoxins associated with gram negative bacteria?
Lipopolysaccharides (LPS) - lipid A is the pathogenic portion.
What are endodoxins?
Cell wall components composed of lipopolysaccharides or lipoteichoic acids that cause fever/general sickness, tissue damage, CV shock and death.
What are cell wall toxins of gram-positive bacteria?
Lipoteichoic acid (LTA).
What’s the role of membrane vesicles?
Pathogenesis Signaling Excretion of toxic products Killing of competitors Immunomodulation Excretion of bacterial toxic products Transformation
Blood can be used for:
culture, serology and molecular genetics
What types of bacteria are stained with acid fast stain?
Mycobacterium, nocardia, cryptosporidium
What types of stains can be used to determine cellular association and morphology of bacteria?
H&E, Romanowsky, Wright’s, Ciemsa, Diff-Quik, Gram stain
What are the steps of Gram stain and what is the purpose of each step?
Fixation - use heat or alcohol
Crystal Violet stain - adheres to the peptidoglycan layer of the gram + organisms. It cannot adhere to the peptidoglycan layer of gram - bacteria because it isn’t accessible
Iodine treatment - the “mordant”. It interacts with the crystal violet, adhering it to the peptidoglycan layer of the gram+ organisms
Decolorization - (alcohol wash) Removes crystal violet from the cell wall of the gram negative bacteria
Counter stains (most often safranin)
What is empirical treatment
treating what you believe is there without having a definitive diagnosis.
What two elements are required in large amounts by bacteria to survive?
Carbon and nitrogen
What do peptones provide for bacteria?
nitrogen, phosphate, sulfate, potassium, magnesium, calcium and iron
What is a mesophile?
Bacteria that grows in moderate temperatures (~37 C)
What is a psychotroph?
bacteria that can grow an reproduce in lower temperatures (10-15 C)
What is selective media?
Media that allows growth for some types of bacterial species, but excludes others.
Differential media
allows you to see some characteristic difference when grown on this media.
List (3) basic nutrient media.
Trypticase Soy Agar (TSA)
Luria Bertani (LB) Agar
Mueller-Hinton (MH) Agar
What is the difference between blood agar and chocolate agar?
Chocolate agar is lysed blood that’s been heated (vs. just lysed agar)
Which media is selective for gram positive bacteria?
Phenylethyl Alcohol Agar (PEA)
Which media is selective for fungi (low pH)?
Sabouraud Dextrose (SabDex) Agar
In what way is blood agar differential? Selective?
Easy to assess whether or not there is lysis and what kind of lysis occurs.
It allows all the things to grow. Not selective.
Describe the use of MacConkey Agar (MAC).
Selective for gram negative bacteria
Differentiates between strains capable of fermenting lactose
Describe the use of Mannitol Salt Agar (MSA).
Selective for gram positive bacteria
Differentiates between strains capable of fermenting mannitol
List three examples of ID test strips/plates used in identification of bacterial species.
Remel RapID, Sensititre, BD crystal
What is the gold standard in molecular diagnostics of bacterial species?
16S ribosomal RNA PCR - 16S is the conserved component of 30S small subunit in prokaryotic ribosomes.
What are nucleic acid multiplex or microarrays?
allow for detection of multiple bacterial species in a single sample. This is either PCR-based or uses tagged oligonucleotide probes in digested sample