Antimicrobials Flashcards by Mackenzie Hopkins

Describe antiseptics and germicides

•chemicals that kill/inhibit microbial growth
•non toxic - applied to tissue

How well did you know this?

Not at all

Perfectly

Are antiseptics and germicides toxic?

•no
•can be applied to living tissue

How well did you know this?

Not at all

Perfectly

Targets for antibiotics

*cell wall synthesis
*DNA/RNA replication
*antimetabolites
*protein synthesis 30S + 50S ribosome subunit

How well did you know this?

Not at all

Perfectly

What does 50S and 30S mean in terms of ribosomes

•50S is the larger sub unit (on top)
•30S is the smaller unit (bottom)

How well did you know this?

Not at all

Perfectly

3 effects anti microbials can have

Bacterio, fungi, viri;
*static
*cidal
*lytic

How well did you know this?

Not at all

Perfectly

What does bacteriostatic, fungistatic, viristatic

*inhibits further growth

How well did you know this?

Not at all

Perfectly

Mechanism for static function

•inhibits protein and RNA synthesis
•helps host take over

How well did you know this?

Not at all

Perfectly

What does bactericidal, fungicidal and viricidal mean

*disrupts synthesis - kills microorganisms (suicide)

How well did you know this?

Not at all

Perfectly

Mechanism for cidal antimicrobes

•disrupts cell wall synthesis
•faster than static
•less reliant on host ability

How well did you know this?

Not at all

Perfectly

Bacteriolytic meaning

*lyse cell wall - kills microorganisms

How well did you know this?

Not at all

Perfectly

Bacteriolytic mechanism

•lyse cell wall
•cytoplasmic content released

How well did you know this?

Not at all

Perfectly

Susceptibility meaning

•level of vulnerability of microorganisms to antimicrobial

How well did you know this?

Not at all

Perfectly

Beta lactam antibiotics

•penicillins
•cephalosporins
•carbapenems

How well did you know this?

Not at all

Perfectly

Antibiotic groups that inhibit cell wall synthesis

•beta lactams
•glycopeptides
•lipopeptides
•polypeptides

How well did you know this?

Not at all

Perfectly

What type of antibiotics are ones that target cell wall synthesis

•bactericidal
•Bacteriolytic

How well did you know this?

Not at all

Perfectly

How do beta lactam antibiotics target cell wall synthesis

•bind and inhibit penicillin binding proteins of bacteria

How well did you know this?

Not at all

Perfectly

What is the function of penicillin binding proteins for the bacteria

•function in cell wall synthesis
•catalyzes cross bridge formation in peptidoglycan

How well did you know this?

Not at all

Perfectly

Is the effect of beta lactams on bacteria always the same?

•no
•morphological effect depends on the PBP bound to the type of beta lactam
•can be rapid swell + burst or no visible change + die

How well did you know this?

Not at all

Perfectly

What does the beta lactam-PBP complex stimulate

•releases autolysins
•digest the existing cell wall

How well did you know this?

Not at all

Perfectly

What mechanisms are used to resist against beta lactams

•modify target site
•modification of antibiotic
•decrease uptake of antibiotic

How well did you know this?

Not at all

Perfectly

How to bacteria modify beta lactam target (penicillin binding proteins)

*acquire new PBP
*modify existing PBP
*overproduction PBP

How well did you know this?

Not at all

Perfectly

What is a rare modification that bacteria make to stop beta lactams

•overproduction of PBPs

How well did you know this?

Not at all

Perfectly

How do staphylococcus aureus acquire a new PBP

•insertion of SCCmec gene
•alters PBP2 -> PBP2a

How well did you know this?

Not at all

Perfectly

What is the function of SCCmec gene

•use by staphylococcus aureus to alter their PBP2
•methicillin resistance

How well did you know this?

Not at all

Perfectly

What does the SCCmec gene allow resistance to

•methicillin

How do bacteria modify an existing PBP

•recombination •point mutation

What is an example of recombination causing beta lactam resistance

•streptococcus pneumonia resist penicillin

What is an example of point mutation causing beta lactam resistance

•enterococcus faecium resist penicillin

Resistance meaning

ability of organism to avoid harmful effects of antimicrobial

Resistance based on genetic changes

1. mutation of existing gene 2. acquired resistance determinants due to horizontal gene transfer

Resistance mechanisms of bacteria

1) Alter target site 2) Inactivation of antibiotic 3) Alter metabolic pathway 4) Reduced drug accumulation - efflux or decreased uptake

what is SCCmecA

staphylococcus chromosomal cassette - mobile element of resistance

what is the SCCmecA complex made of

J1-ccr-J2-mec-J3-orfX

Function of ccr gene

responsible for mobility

Function of mec gene

-housekeeping -virulence factors

Function of J regions in SCCmecA

-additional resistance -virulence genes -non-coding -plasmids -insertion sequences

How many types mec genes

2 - A or C

How many types of crr genes

3 - A, B or C

How many types of SCCmec complex

14 types - several subtypes

How is PBP2a more beneficial than PBP2

PBP2a has lower affinity for beta-lactams - cell wall synthesis can proceed

what gene encodes for PBP2a protein

mecA

when is staphylococcus classed as MRSA

oxacillin MIC > or = 4 mg/ml

what are beta-lactamases

enzymes that inactivate the beta-lactam antibiotics

what types of bacteria can produces beta-lactamases

Both gram +ve and -ve

Gram +ve mechanism for beta-lactamases

excreted into surrounding environment

Gram -ve mechanism for beta-lactamases

remain intracellular in periplasmic space

How many types of beta-lactamases

over 200 (penicillinases, cephalosporinases etc)

how does beta-lactamases inactivate antibiotics

Hydrolyses *inactivates the beta-lactam ring

what is released when beta-lactamases hydrolyse

CO2

What is the mechanism of pinching

large amount of lactamase binds antibiotic quickly and firmly EXTRACELLULAR

Benefits of pinching mechanism

-prevent antibiotic INTRACELLULAR -antibiotic can't reach target site

What type of bacteria decrease the uptake of beta-lactam antibiotics

ONLY gram -ve

decreased uptake mechanism

*transit required through pore -change in number or size

Gram -ve beta-lactam resistance mechanisms

1) Decreased uptake (porins) 2) beta-lactamases 3) Alter PBP target

Gram +ve beta-lactam resistance mechanisms

1) beta-lactamases 2) Alter PBP target

Antibiotics that inhibit protein synthesis

-aminoglycosides -tetracyclines -macrolides -oxazolidinone -lincosamide

what antibiotics bind 50s subunit

Oxazolidinone Macrolides Lincosamides

Mechanism of antibiotic that bind 50s subunit

-prevent peptide bond formation -stop protein synthesis

which antibiotics bind 30s subunit

Aminoglycosides Tetracyclines

Mechanism of aminoglycosides

impair proofreading - faulty proteins made

mechanism of tetracyclines

block binding of tRNAs - inhibit protein synthesis

Resistance mechanisms to aminoglycosides

-modification of antibiotic -mutation ribosomal target site -efflux

extra resistance mechanism of gram -ve to aminoglycosides

-mutations in gene encoding porin protein - OmpF -lower level resistance

Inhibitors of nucleic acid synthesis

Quinolones Rifampin Metronidazole

Inhibitors of nucleic acid description

-broad-spectrum -bactericidal

Mechanism of Quinolones

-inhibits topoisomerase II and IV enzymes -required for DNA replication, recombination and repair DEATH

Resistance mechanisms to Quinolones

-Mutations to topoisomerase II + IV -Efflux via NorA,B,C and SdrM proteins

Antimetabolite antibiotics

Sulfonamides Trimethoprim

Antimetabolites description

-Bacteriostatic -broad-spectrum -target folic pathway

what pathway do antimetabolites target

Folic acid

Resistance mechanisms to antimetabolites

-Altered enzymatic targets (folic acid pathway) -No longer bind antibiotic

Antimicrobials Flashcards

(71 cards)