Final Exam Flashcards
Pleomorphic
bacteria variable in shape
Cell envelope
cell wall, plasma membrane, outer membrane (gram neg only), Periplasm (gram neg only)
Cell wall
rigid part = peptidoglycan composed of N-acetylglucosamine and N-actylmuramic acid + tetra peptide
confers protection
takes part in cell division
responsible for shape of bacterial cell
posses target sites for antibiotics, lysozyme and bacteriophages
gram positive cell wall
many layers of peptidoglycan
lipoteichoic acid and wall techoic acid
major surface antigens of gram positive bacteria
gram negative cell wall
v few layers of peptidoglycan and an outer membrane
gram neg outer membrane
bilayered structure with lipopolysaccharide
porins allow passive diffusion of low MW hydrophilic molecules
large antibiotics penetrate the outer membrane slowly = high resistance in gram neg bacteria
lipopolysaccharide
- consists of lipid A = endotoxin of gram neg bacteria toxicity associated with the lipid portion and the O-polysaccharide is the major surface antigen
spheroblasts
cell wall removed in gram neg bacteria
protoblasts
cell wall removed in gram pos bacteria
L-forms
removal of cell wall results in wall-less non-viable bacteria BUT if they are able to grow and divide - L-forms
unstable: revert back to cell wall containing state when inducing stim is removed (penicillin)
stable: do not revert back to normal state
mycoplasma
naturally occurring bacteria which lack cell wall
cytoplasmic membrane functions
permeability and transport
biosynthetic functions
electron transport and ox phosphorylation
chemotactic systems
- deepest layer of the cell envelope
thin semi-permeable layer consisting of proteins and phospholipids
plasmids
extrachromosomal double stranded circular DNA molecules capable of replicating independently of the bacterial chromosomes - toxigenicity and drug resistance
glycocalyx functions
capsule or slime layer
role in adherence of bacteria to human tissues - infection
enhances virulence
role in biofilm formation
peritrichous flagella
numerous flagella all over the bacteria
monotrichous flagella
single polar flagellum
lophotrichous flagella
tuft of flagella at one end
amphitrichous flagella
flagella at both poles of the cell
pili
thin short filamentous appendages found mainly in gram neg bacteria - twitching and gliding motions, conjugation sex pili, adherence
fimbriae
thin short filamentous appendages found mainly in gram neg bacteria made of structural protein pilin
adherence
biofilm formation
endospores resistance
coat, low water content, low metabolic activity, high conc of Ca dipicolinic acid makes resistance to heat and drying
obligate aerobes
pseudomonas aeruginosa (gram neg), bacillus (gram pos)
obligate anaerobes
clostridium
facultative anaerobes
live with or without oxygen
staphylococci (gram pos) E. coli (gram neg)
aerotolerant anaerobes
don’t use aerobic metabolism but have some enzymes that detoxify ox poisonous forms - radicals
microaerophiles
require oxygen levels from 2-10% limited ability to detox H202and superoxide radicals - H pylori
hyaluronidase
splits hyaluronic acid - important component of connective tissue - aids in spreading infection for microbe
coagulase
works with blood factors to coagulate plasma and leads to formation of fibrin wall around the organism protects from phagocytosis
hemolysin and leukocidins
dissolve RBC and destroy leukocytes/macrophages
IgA1 protease
degrades IgA - allows organism to adhere to mucous membranes
quorum sensing
Bacteria communicate with each other
Cell-cell communications via signalling molecules that allow bacteria to share info on cell density and adjust gene expression accordingly
Reduce gene expression if favours survival
indirect ELISA
receptor antibodies bind to the bound autoantibodies from the sample forming complex with immobilized antigen, autoantibody, and labelled reporter antibody
direct ELISA
secondary antibody binds to the bound protein from the sample forming complex consisting of immobilized antibody, protein and labelled secondary antibody
specimen collection
- quantity of material must be adequate
- sample must be representative of the infectious process (sputum not saliva)
- contamination of the specimen must be avoided by only using sterile equipment and aseptic technique
- specimen must be taken directly to the lab and examined promptly - special transport media prevent drying and stabilize conditions
- before antimicrobials are admin
complex media
exact chem composition isn’t known
contains yeast extract
nutrient broth, trypticase soy agar, MacConkey agar
enriched: added blood for fastidious organisms
selective media
contains substances that favour or inhib the growth of specific organisms
eosin methylene blue and crystal violet dyes and bile salts - inhib growth of gram pos bacteria without adversely affecting most gram neg (not the fastidious ones)
differential media
presence of visible changes in the growth media or dif in the appearance of colonies help differentiate various kinds of bacteria growing on the medium
blood agar - enriched and differential - hemolytic properties and fastidious
MacConkey agar - selective and differential
MacConkey agar
selective + differential
crystal violet inhib growth of gram pos so allows for isolation of enteric gram neg incorporation of lactose and pH indicator neutral red permits differentiation of enteric bacilli on the basis of their ability to ferment lactose - produce enough acid by fermenting lactose to reduce the pH below 6.8 the neutral red colorless turns red
latose fermenting is red but nonlactose fermenting is colorless
Protein A
Staph aureus
inhibits IgG complement cascade allows bacteria to bind to immune cells and prevent clearance from site of infection
pathogenicity
structures/enzymes that evade phagocytosis
production of enzymes
production of toxins
staph aureus pathogenicity
protein A, coagulase, bacterial capsule
staphylococcus enzymes
coagulase, hyaluronidase, staphylokinase, beta-lactamase
staphylokinase
opposite of coagulase - activates plasminogen to form plasmin which digests fibrin clots
Staphylococcus exotoxins
hemolysins, exfoliative toxins, toxic shock syndrome toxin, enterotoxins
Group A strep
S. pyogenes virulence factors
Capsule, Protein M (antiphagocytic), pyrogenic exotoxins (erythrotoxigenictoxin)
streptokinase (fibrinolysin)
hemolyisn - beta hemolytic
hyaluronidase
anthrax toxin
protective antigen - mediates entry
edema factor
lethal factor - death
ideal antimicrobial
effective, broad spectrum, non toxic, doesnt result in drug resistance - no agent has all of these qualities
tetracycline
broad spectrum antibiotic (protein synthesis inhibitor) with activity against gram pos and gram neg mycoplasma chlymdia
forms complexes with Ca incorporated into bones and dev teeth–> malformation of skull and stained weakened tooth enamel
vancomycin
narrow spectrum antibiotic (inhibits cell wall synthesis) with activity against gram +
antibiotic side effects
toxicity - liver kidney nerves
disruption of normal microbiota - secondary infections