Pre Infectious Disease Exam 1

Bacterial chromosome

circular

Eukaryotic chromosome

linear in nucleus

Eukaryotic Ribosomes

40S, 60S, 80S

Bacterial ribosomes

30S, 50S, 70S

Cell wall

bacteria have this, most human cells do not

Bacterial DNA modifying enzymes

gyrase, topoisomerase IV

Folic acid synthesis

done by bacteria, not by human cells

Plasmid

loop of DNA separate from the chromosome in bacteria that replicate separately and give the bacteria extra genes

Capsule

bacterial covering made of polysaccharides that prevents phagocytosis and aids in attachment; responsible for differences in serotypes

Bactericidal agents

kill bacteria

Bacteriostatic agents

Inhibit bacterial growth

DNA gyrase

enzyme that allows bacteria to unwind their DNA for replication, lethal to bacteria if inhibited

topoisomerase IV

cuts DNA to relieve twisting forces during unwinding and replication, lethal to bacteria if inhibited

folic acid

humans acquire this from diet, cofactor in DNA precursor synthesis of thymidine, bacteria synthesize it using enzymes using dihydropteroate, PABA, and glutamic acid, inhibition of this synthesis pathway is lethal to bacteria

folic acid synthesis enzymes

dihydropteroate synthase and dihydrofolate reductase

Aminoglycosides

water-soluble, bactericidal, bind to 30S subunit, cause misreading mRNA, forms aberrant proteins that kill the cell

Tetracyclines

bacteriostatic, protein synthesis inhibitor, binds to 30S ribosome, prevents incoming tRNA from binding to the A site

Macrolides

bacteriostatic, protein synthesis inhibitor, bind to 50S subunit in the P-site, inhibit peptide transfer, shortened peptides are formed

Sulfamethoxazole

inhibits dihydropteroate synthase

Trimethoprim

inhibits dihydrofolate reductase

Nonsterile sites

mouth, sputum, GI tract, skin, outer parts of the female reproductive tract

Sterile sites

internal organs, blood, CSF, urine, lungs, biliary tract, liver, kidneys, spleen, pancreas

Colonization

presence of microorganisms that are not causing disease

Infection

presence of microorganisms that are causing disease

Empiric therapy

broad-spectrum agents to treat suspected pathogens

Definitive therapy

treating known pathogens when sensitivity results are available

Nose

colonized by Staphylococcus aureus

Mouth

colonized by Viridans streptococci and anaerobes

Upper respiratory tract

colonized by Streptococci, viridans streptococci, S. pyogenes, S. pneumonia, Haemophilus influenza, and Moxarella catarrhalis

Lower respiratory tract

colonized by Streptococcus pneumonia, Haemophilus influenza, and atypicals such as mycoplasma pneumoniae, chlamydia pneumoniae, and legionella sp.

Skin

colonized by Staphylococcus epidermidis, Staphylococcus aureus, and Streptococci, especially S. pyogenes

GI tract

colonized by enteric Gram-negative rods such as E. coli and Klebsiella, anaerobes such as B. fragilis, Enterococci, and Streptococci

Urinary tract

colonized by E. coli, S. saprophyticus, and group B streptococci

Staphylococcus aureus

gram positive coccus in clusters, catalase positive, coagulase positive

MSSA

nafcillin, oxacillin, cefazolin

MRSA

vancomycin IV, daptomycin, linezolid

Staphylococcus epidermidis

gram positive coccus in clusters, catalase positive, coagulase negative

MSSE

nafcillin, oxacillin, cefazolin

MRSE

vancomycin, daptomycin, linezolid with or without rifampin

Staphylococcus saprophyticus

gram positive coccus in clusters, catalase positive, coagulase negative, treated with Bactrim or nitrofurantoin

Viridans streptococci

gram positive cocci in chains and pairs, alpha-hemolytic, treated with penicillin or amoxicillin

Streptococcus pneumoniae

gram positive coccus in pairs, alpha-hemolytic, treated with penicillin, azithromycin, ceftriaxone, respiratory fluoroquinolones, or vancomycin

Streptococcus pyogenes

group A, gram positive coccus in chains and pairs, beta-hemolytic, treated with penicillin and amoxicillin

Streptococcus agalactiae

group B, gram positive coccus in chains and pairs, beta-hemolytic, lives in GI and female reproductive tracts, treated with penicillin and amoxicillin

Enterococcus faecalis/faecium

group D, gram positive coccus in chains and pairs, gamma-hemolytic, treated with ampicillin or vancomycin with or without an aminoglycoside

Vancomycin resistant enterococcus

treated with daptomycin or linezolid

mecA gene

causes S. aureus to be resistant to methicillin

Biofilms

glycocalyx-producing strains of S. epidermidis make these, allowing them to live on and cause infectious through prosthetic valves and indwelling catheters, infections with these can be more challenging to treat

Alpha hemolytic

partial lysis of RBCs forming a green zone

Beta hemolytic

complete lysis of RBCs, forming a clear zone

Gamma hemolytic

no lysis of RBCs

Amoxicillin

Amoxil

Amoxil therapeutic class

beta lactam, amino-penicillin

Amoxicillin/clavulanate

Augmentin

Augmentin therapeutic class

beta lactam, amino-penicillin/PO beta-lactamase inhibitor

Ampicillin/sulbactam

Unasyn

Unasyn therapeutic class

beta-lactam, amino-penicillin/IV beta-lactamase inhibitor

Piperacillin/tazobactam

Zosyn

Zosyn therapeutic class

beta lactam, penicillin/beta-lactamase inhibitor

cefazolin

Ancef

Ancef therapeutic class

beta lactamase, 1st generation cephalosporin

cephalexin

Keflex

Keflex therapeutic class

beta lactam, 1st generation cephalosporin

Cefuroxime

Ceftin

Ceftin therapeutic class

beta lactam, 2nd generation cephalosporin

ceftriaxone

Rocephin

Rocephin therapeutic class

beta lactam, 3rd generation cephalosporin

cefepime

Maxipime

Maxipime therapeutic class

beta lactam, 4th generation cephalosporin

meropenem

Merrem

Merrem therapeutic class

carbapenem

imipenem

Primaxin

Primaxin therapeutic class

carbapenem

vancomycin

Vancocin

Vancocin therapeutic class

glycopeptide

daptomycin

Cubicin

Cubicin therapeutic class

lipopeptide

linezolid

Zyvox

Zyvox therapeutic class

lipoglycopeptide

azithromycin

Zithromax

Zithromax therapeutic class

macrolide

ciprofloxacin

Cipro

Cipro therapeutic class

fluoroquinolone

levofloxacin

Levaquin

Levaquin therapeutic class

fluoroquinolone

sulfamethoxazole/trimethoprim

Bactrim

Bactrim therapeutic class

sulfonamide

Beta-lactam mechanism of action

inhibits bacterial cell-wall synthesis by binding to penicillin-biding proteins, which stop peptoglycan synthesis

carbapenem mechanism of action

inhibits bacterial cell-wall synthesis by binding to penicillin-biding proteins, which stop peptoglycan synthesis

Glycopeptide mechanism of action

prevents glycopeptide polymerization by binding to D-alanyl-D-alanine part of the cell wall precursor, inhibiting bacterial cell wall synthesis

Lipoglycopeptide mechanism of action

binds to bacterial 23S rRNA from the 50S subunit, preventing the formation of a whole ribosome, bacteriostatic against enterococci and staphylococci and bactericidal against most streptococci

Lipopeptide mechanism of action

binds to cell membrane components, causes depolarization which inhibits the synthesis of DNA, RNA, and proteins, bactericidal

fluoroquinolone mechanism of action

inhibits DNA gyrase