MLSC 4341 Exam 3 Questions & Answers 2024/2025
What are some ways to inhibit cell wall synthesis? - ANSWERS-Inhibit cell wall directly (peptidoglycan synthesis)
-Inhibit enzymes (bind to enzymes involved in the synthesis)
-Inhibit cofactors for cell wall synthesis
-Bacitracin
What are pe...
What are some ways to inhibit cell wall synthesis? - ANSWERS-Inhibit cell wall directly (peptidoglycan
synthesis)
-Inhibit enzymes (bind to enzymes involved in the synthesis)
-Inhibit cofactors for cell wall synthesis
-Bacitracin
What are penicillin binding proteins? - ANSWERS-Enzyme groups in bacteria responsible for producing
and maintaining peptidoglycan layer
-Structure varies among organisms
What are beta lactam agents? - ANSWERS-Contain a beta lactam ring which binds to penicillin binding
proteins (responsible for producing and maintaining peptidoglycan/cell wall)
What is the structure of penicillin? - ANSWERS-Beta-lactam ring
-Beta lactam nucleus attached to thiazolidine ring
How does penicillin interfere with peptidoglycan synthesis? - ANSWERS-Interferes with the
transpeptidation process of peptidoglycan synthesis
What happens when the ring in penicillin is changed? - ANSWERS-Changes action of drug and its
resistance
What are natural penicillins active against? - ANSWERS-Group A strep and Neisseria meningitidis
What are semisynthetic penicillins used for? - ANSWERS-Penicillin resistant staphylococci
,What are extended spectrum penicillins (amino penicillins) used for? - ANSWERS-Good activity against E.
coli, Proteus app, and Haemophilus influenzae
How can extended spectrum penicillins (amino penicillins) be inactivated? - ANSWERS-By beta
lactamase, an enzyme which destroys the beta lactam ring making the drug ineffective
What are anti-pseudomonas penicillins used for? - ANSWERS-Good activity against P. aeruginosa
How can anti-pseudomonas penicillins be inactivated? - ANSWERS-By beta lactamase, an enzyme which
destroys the beta lactam ring making the drug ineffective
How do anti-pseudomonas penicillins differ from other penicillins? - ANSWERS-No advantage over other
penicillins for non-pseudomonal species
-Always treated in combination with aminoglycosides (it is synergistic)
What is the structure of cephalosporins? - ANSWERS-Semi synthetic beta lactams
-Their main nucleus consists of a beta-lactam ring and a second ring. they have two sites for placement
of R groups.
How are cephalosporins grouped? - ANSWERS-In generations, based on their spectrum of activity
How is resistance to cephalosporins formed? - ANSWERS-Through beta lactamase enzyme
What are first generation cephalosporins used for? - ANSWERS-Good activity against gram positives
-Poor activity against gram negatives
What are second generation cephalosporins used for? - ANSWERS-More activity against gram negatives
-Less activity against gram positives
-Good against fastidious organisms
,What are third generation cephalosporins used for? - ANSWERS-Good activity against gram negatives,
especially for identified beta lactamase producers like H. influenzae, M. catarrhalis, N. gonorrhoeae, and
N. meningitidis
-Less activity against gram positives
When is resistance seen with third generation cephalosporins? - ANSWERS-Seen with extended
spectrum beta lactamase producers (ESBLs)
What specific drug is the best of all beta lactams against Pseudomonas? - ANSWERS-Ceftazidime (fortaz)
What are fourth generation cephalosporins used for? - ANSWERS-Good activity against beta lactamase
producing organisms
-Some activity against enterics
What are carbepenems used for? - ANSWERS-Better activity against gram positives than the
cephalosporins
-Broad spectrum drug
-Used to treat multi-drug resistant Gram negative rods (drug of choice for ESBLs)
What organisms do carbepenems have no activity against? - ANSWERS-MRSA or C. difficile
What are monobactams? - ANSWERS-Monocyclic beta lactam
-Resistant to some beta lactamases, but inactivated by ESBLs (extended spectrum beta lactamases)
What are monobactams used to treat? - ANSWERS-Used to treat anaerobes or gram positives
-Always administered intravenously (by IV)
What are glycopeptides? - ANSWERS-Non-beta lactam drug that inhibits cell wall synthesis
-Do not bind PBPs, but bind other precursors of cell wall synthesis
-Not affected by beta lactamases
, What are glycopeptides used for? - ANSWERS-Most effective against gram positives and MRSA
What is bacitracin? - ANSWERS-Inhibits metabolites necessary for peptidoglycan synthesis
-Highly toxic
-Used only as a topical ointment
What are the 4 genera in the Micrococcaceae family? - ANSWERS-Staphylococcus
-Micrococcus
-Rothia
-Planococcus
What are the characteristics of the micrococcaceae family? - ANSWERS-Gram positive cocci in clusters
-Aerobic or facultatively anaerobic
-Non-motile
-Catalase positive
Where is staphylococcus normally found? - ANSWERS-More than 30 species found on skin and mucus
membranes
What does staphylococcus look like on a gram stain? - ANSWERS-Gram positive cocci in clusters (divide in
multiple planes)
What is the colonial morphology of staphylococcus? - ANSWERS-Circular, opaque, smooth, yellow or
white
Where is Staph aureus (STA) normal flora? - ANSWERS-Upper respiratory tract, especially in healthcare
workers
-20-40% are carriers in nasopharyngeal tract
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