lecture 7 Flashcards

Question

VACCINES MADE BY GENETIC ENGINNERING

Answer 1

Recombinant vaccine: DNA that codes for the production of pathogen antigen is inserted into a bacteria or yeast -The bacteria or yeast make the antigen. This manufactured antigen is purified and used in a vaccine mRNA vaccine: Vaccine includes mRNA from the pathogenic organism that is put into a lipid membrane to help it get into the host cells Causes the host cell to make the pathogen antigen which elicits an immune response DNA vaccines: Vaccine includes a plasmid that has a portion of the pathogen’s DNA – causes the host to make the antigen & an immune response

Answer 2

-Resistance to the spread of an infectious disease in a population is based on the pre-existing immunity of a high proportion of individuals as a result of previous infection or vaccination. -The % of people who need to be immune to achieve herd immunity is based on the reproduction number (R0) – R0 varies with each disease -R0 = the average # of people that a single person with the virus can infect

Answer 3

-drugs or chemicals that act against microorganisms -kill the organism “cidal” at end of word -slow the growth of the organism “static” at the end of the word Disinfectant: kill wide range of organisms on non-living surfaces Antiseptic: kill organisms on living tissue Antibiotic/Antifungal/Antiparasitic: destroy bacteria, fungus or parasites within the body

Answer 4

-Naturally produced by plants, molds & bacteria. -Or synthetically by pharma -Act against bacteria -treat patients with active diseases -help the patient to recover from the illness -reduces the time during which the patient is infectious so limits spread - eliminate potentially harmful microorganisms from “carriers” = healthy individuals who harbor organisms Broad spectrum: Effective against a wide range of bacteria Narrow spectrum: Active against a selected group of bacterial types ribosome - inhibits protein syn DNA- inhibit NA syn Cell wall - inhibit cell wall syn Cell membrane - disruption of membrane function folic acid - block pathways and inhibit metabolism

Answer 5

-Age, whether they are pregnant or immunosuppressed. -The body site where the organism was isolated

Answer 6

-Natural even before antibiotics Natural resistance- way for antibiotic producing bacteria to protect themselves from own antibiotic -Recent resistance due to overuse of antibiotic agents -Bacteria acquire mechanisms to withstand toxic effects & can pass these on to other bacteria -Resistance passed on by physical movement of DNA & incorporation into recipient gene -Transduction, conjugation, transformation MDR = multidrug resistant organism

Answer 7

Vertical gene transfer: Spontaneously produced R gene is passed through normal bacterial replication Horizontal gene transfer: transposons, plasmids Conjugation-plasmid with R gene passes it to another bacteria through pili Transduction- bacteriophage incorporates bacterial R gene during repackaging of it’s own DNA & spreads it to other bacteria Transformation-bacteria with R gene dies and lysis. Bits of genetic material is picked up by other bacteria & incorporated

Answer 8

Constitutive gene expression: gene expressed continuously Induced gene expression - gene found on a plasmid-only produced after exposure to the antibiotic Homogenous resistance expression; resistance expressed uniformly in all bacteria Hetero-resistant expression: small bit of bacteria growing express resistant. Can be missed in lab Intrinsic Resistance: inherent characteristic in a bacteria that allow antibiotic to be tolerated Acquired Resistance: distinct from parent gene, horizontal transfer of pre existing gene

Answer 9

Impermeability -when bacteria decrease the ability of the antibiotic to enter the cell Mutations in the o-antigens of the LPS in gram negative bacteria change the shape or overall charge of the cell wall = decrease in some antibiotic binding Lack in #s of, or mutations in, antibiotic binding targets = a decrease in the ability of some antibiotics to bind to the cell wall Porins (outer membrane channels) allow for movement of nutrients and waste in and out of cell. Decrease production of porins or a change in their structure reduce the ability of an antibiotic to go through into the cell Efflux: Naturally occurring pumps in gram pos & gram neg bacteria Transport proteins remove toxic substances & antibiotics from inside cell and pump them out Enzymatic inactivation: Production of enzyme that inactivates the antibiotic before it reaches it target Example = Production of beta lactamase: Most common intrinsic mechanism for beta lactam drugs

Answer 10

Efflux: Acquire a gene for efflux mechanism Target site modification/acquisition of new targets: Chromosomal mutation that allows the bacteria to modify the antibiotic target site so antibiotic can’t bind Example: beta lactam drugs target penicillin binding protein (PBP) in cell wall. If gene causes a change in the PBP the antibiotic can’t bind. Mechanism used by MRSA - PBP altered to PBP 2a Production of enzymes to inactivate antibiotic: Acquire a gene that causes the production of enzyme – beta lactamase

Answer 11

-S. aureus – is the most common cause of skin infections -treated with oxacillin, methicillin or cloxacillin -resistance due to acquired mec A or mec C gene -These antibiotic target the PBP (penicillin binding protein) in bacterial cell wall If resistant to one of these drugs is considered resistant to the whole group – Any penicillins, cephalosporins or carbapenems

Answer 12

-Part of infection control in hospitals -Screening determines if person is a carrier of methicillin-resistant Staphylococcus aureus (MRSA) -Samples from at-risk patients even in the absence of signs or symptoms of infection -Usually done on patients who are transferred from another hospital or to patients being admitted to critical care units like: ICU, surgery, burn units or who have been on a lot of antibiotics -Nasal swab is taken and sent to the lab for MRSA and rectal for VRE -Put on special chromogenic media that helps to isolate MRSA Any Staphylococcus aureus isolated from a patient specimen is screened for methicillin resistance -broth microdilution testing (Vitek Susceptibility test) -S. aureus that is isolated is also put on MHA that contains 6 μg/ml of oxacillin & 4% NaCl -confirm with latex agglutination or immunochromatographic membrane test which tests for PBP2a. - test for the mec A gene

Answer 13

-Normal flora of the intestine but can cause skin, surgical wound, blood and urine infections -Intrinsically resistant to many antibiotics like penicillin & cephalosporins -Acquired resistance to erythromycin, tetracycline, and high level aminoglycosides and now vancomycin -Van A & Van B genes cause resistance -Enterococcus faecium & Enterococcus faecalis acquire Van A or Van B via transposons to become vancomycin resistant -Van C gives low level intrinsic resistance

Answer 14

-aids in confirming whether an isolate has intrinsic (Van C) or acquired resistance (Van A or Van B) -Van A and Van B genes are transferable -Van C genes are not transferable

Answer 15

-Vancomycin first used to treat staphylococcal infections -The VRE started spreading a plasmid-borne resistance genetic element to S. aureus -Resulting in emergence of vancomycin intermediate S. aureus (VISA) or vancomycin resistant S. aureus (VRSA) - reduced susceptibility of VISA, VRSA & VRE to vancomycin leaves few options for treatment