Chapter 17: Bacterial Infections Flashcards
Natural bacterial barriers include
skin
mucous membranes
lactic acid
long-chain fatty acids
lysozymes
reticuloendothelial system
bacterial barriers other than the body’s natural ones
overall health
age
nutritional status
comorbidities
blood supply near infection site
natural and acquired antibodies
most commonly used classes of antibiotics
PCNs
fluoroquinolones
cephalosporins
macrolides
tetracyclines
bacteriocidal antibiotics
kill the invading organism
bacteriostatic antibiotics
inhibit growth of invading organism so the body’s defenses can kill it
methods by which antimicrobial drugs effect the invading microbe
- inhibition of cell wall synthesis/repair
- inhibition of protein synthesis
- disruption of membrane permeability
- inhibition of nucleic acid synthesis
- inhibition of specific biochemical pathways
cell wall structure of gram- and gram+ bacteria
gram + tends to be a simpler structure and easier to damage
empricial prescribing
prescribing based on previous experience when treatment must be started prior to lab results
what are the 3 things used to classify all organisms
morphology (cocci, bacilli)
growth characteristics (anaerobic, aerobic)
other qualities (gram+, gram-)
patient education for antimicrobials
take as prescribed and finish entire course
do not take for viral infections
do not take someone else’s
patient’s should ask about potential for resistance
which 2 agents are most commonly asociated with clinically significant drug interactions
quinolones and macrolides
interactions between ABTs and other medications
coumadin interacts with many
birth control with PCN
classess of bacteriocidal ABTs that affect cell wall synthesis
Natural Penicillins
expanded-spectrum PCNs
extended spectrum PCNs
penicillinase resistant PCNs
4 groups of PCNs
natural PCNs
PCN G
PCN V
aminopenicillins (amoxicillin, ampicillin)
signs of superinfection to watch for when prescribing PCNs
abdomina cramps
fever
watery diarrhea
hypersensitivity reactions to PCN can include
angioedema
serum-sickness
anaphylaxis
severe local inflammaotory reaction at injection site
PCNs effect on Comb’s test
can cause false positive
IV administration of PCN G, K+, or Na_
administer slowly
other conscientious consideration with prescribing PCNs
renal impairment may require dosage adjustments
PCN patient education
- oral tabs 1hr before or 2hr after meals
- take all medication for 14 days
- alternate birth control
- doses should be dividied equally over 24 hour period
- notify clinicain if blood, pus, mucus in stool
important pieces to remeber about pharmacokinetics of PCNs
GI absorption is variable
widely distributed (crosses CSF and breast milk)
partial metabolism in liver but mostly excreted unchanged in urine
more page 316
which medications can inhibits PCN bacteriocidal activity
chloramphenicol
macrolide ABTs
methotrexate
tetracycline
what effect does probenecid have on PCNs and cephalosporins
potentates activity by raising their blood levels
contraindications for natural PCNs
infectious mononucleosis as it can cause extensive rash
cross sensitivity of PCN and cephalosporin sensitivity
about 10%
extended-spectrum PCNs
(cephalosporins)
semisynthetic agents
how are cephalosporins grouped
4 generations based on antimicrobial properties
things to remember in general about cephalosporins
low toxicity
broad spectrum of activity
not reliable against MRSA
action of cephalosporins
1st generation is more useful among gram+
as classification increases, so does spectrum, and ability to effect gram-
cephalosporin mechanism of action
interferes with bacterial cell wall synthesis
(Bacteriocidal)
some clinical uses of cephalosporins
respirtaory tract infections
pneumonia
otitis media
skin infections not caused by MRSA or MRSE
more page 319
cephalosporin patient education
evenly space dosages around the clock
take missed dose ASAP but do not double
do not share
report signs of superinfection
do NOT self-treat any diarrhea that develops
hematologic side effects of cephalosporins
anemia, leukopenia
cephalosporin interactions
aminoglycosides and LOOP diuretics can add to nephrotoxicity
anticoagulants can cause hypoprothrombinemia
cephalosporin contraindication
hypersensitivity
beta-lactamase resistant PCNs mechanism of action
resist the action of penicillinase and bind to the cell wall which causes cell death
what causes resistance to PCNs
invading microbe produces penicillinase which hydrolyzes the beta-lactam ring of the ABTs, rendering it ineffective
examples of penicillinase resistant PCNs
cabenicillin
geocillin
cloxacillin
dicloxacillin
methicillin
examples of first generation cephalosporins
cefadroxil (Duricef)
cephalexin (Keflex)
cefazolin (Ancef)
cephradine (Velosef)
examples of second generation cephalosporins
cefuroxime axetil (Ceftin)
cefprozil (Cefzil)
loracarbef (Lorabid)
cefotetan (Zinacef)
cefaclor (Cecor)
examples of third generation cephalosporins
ceftibuten (Cedax)
ceftriaxone (Rocephin)
cefotaxime (Claforan
cefixime (Suprax)
examples of fourth generation cephalosporins
cefdinir (Omnicef)
cefepime (Maxipime)
clinical uses of penicillinase resistant PCNs
soft tissue and bone infections
respiratory tract infections
sinusitis
UTIs
endocarditis
septicemia
meningitis
what decreases absorption of penicillinase resistant PCNs
gastric acids and acidic juices
extended spectrum PCNs mechanism of action
pass throught the pores in the outer membrane and can reach penicillin-binding proeins on inner cell’s cytoplasmic membranes
examples of extended spectrum PCNs
amoxicillin
ampicillin
amoxicillin/clavulanate (Augmentin)
ampicillin/sulbactam (Unasyn)
why is amoxicillin preferred over ampicillin
it is more completely absorbed and has a lower incidence of diarrhea
How do macrolides work
they inhibit protein synthesis at the 50S ribosome unit