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
Antibiotics that inhibit protein synthesis
macrolides
tetracyclines
aminoglycoside
examples of macrolides
azithromycin (Z-pak)
erythromycin (E-mycin)
clarithromycin (Biaxin)
clindamycin
lincomycin (Linocin)
macrolide clinical uses
mild-mod bacterial exacerbations of COPD
mild-mod pharyngitis/tonsilitis caused by strep
PID
community-acquired pneumonia caused by strep or flu
conscientious considerations for macrolides
C&S is important
watch for nonadherance, anaphylaxis, drowsiness, superinfection
can take without regard to food
may cause photosensitivity
Azithromycin is a derivative of what
erythromycin
why is azithromycin one of the most popular ABT for respiratory, skin, and sexually transmitted infections
effective against so many gram+ and some gram- bacteria
how is azithromycin different from older macrolides
longer half-life
what decreases peak serum levels of azithromycin
aluminum and magnesium containing antacids
what increases peak serum levels of azithromycin
digoxin, theophylline, and phenytoin triazolam
azithromycin contraindications
pregnancy/breastfeeding
liver impairment
sensitivity
absorption of erythromycin (Biaxin)
high but erratic
clinical uses for erythromycin (Biaxin)
legionnaire’s disease
syphylis
diptheria
atypical pneumonia
topically for acne
what is often used as an alternative when a patient is allergic to PCN
Biaxin
erythromycin interactions
ALOT
ethanol reduces plasma concentrations
decreases activity of PCN if co-administered
erithromycin contraindications
hepatic disease or macrolide sensitivity
why is erythromycin preferred over tetracyclines in young people being treated for acne
does not discolor teeth or bind to bone
clinical uses of clindamycin
serious infections
most infections with gram- staph and strep
clindamycin mechanism of action
bacteriostatic or bacteriocidal
inhibits protein synthesis at the ribosome 50S unit
clindamycin interactions
kaolin/pectin preparations decrease absorption
clindamycin contraindications
previous pseudomembranous colitis
severe liver impairment
diarrhea
alcohol tolerance
pregnancy/lactation
why are tetracyclines contraindicated in children and pregnancy
binds to calcium where it stains teeth and affects long bone development
examples of tetracyclines
doxycycline
tetracycline
minocycline
oxytetracycline
tetracycline mechanism of action
broad spectrum bacteriostatic agents that inhibit protein synthesis by binding to the 30S ribosome unit
clinical uses of tetracyclines
syphilis in PCN allergic patients
lyme disease. anthrax
adjunct to therapy for H. pylori ulcers
mycoplasma pneumoniae
(more page 325)
tetracycline interactions
increase effect of warfarin
decrease effect of sucralfate and barbituates
aminoglycoside mechanism of action
bind to ribosomal 30S and 50S subunits to inhibit protein synthesis which causes a defective cell membrane that cannot sustain the bacteria
makeup of aminoglycosides
contain at least one sugar
aminoglycosides clinical uses
serious bacteremia
respiratory/urinary tact infections
infected wounds
infected bone/soft tissues
perotinitis
burns complicated by sepsis
treatment of serious infections with pseudomonas aeruginosa
may require combined therapy with aminoglycosides and ticarcillin, carbenicillin, pipercillin, or ceftazidime
side effects to watch for with aminoglycosides
vestibular and cochlear disturbances, nephrotoxicity, hypersensitivities
aminoglycoside interactions
long list
most result in nephrotoxicity or ototoxicity
clinical considerations with aminoglycosides
poor oral absorption (most are IV)
therapy exceeding 7 days can cause kidney damage
resistance varies widely
sulfonamides mechanism of action
inhibits bacterial folic acid synthesis producing a bacteriostatic effect
examples of sulfonamides
sulfamethoxazole (Gantanol)
sulfamethoxazole/trimethoprim (Bactrim)
clinical uses of sulfonamides
infection with toxoplasma, pneumocystitis jiroveci pneumonia, shigella enteritis, and UTIs
sulfonamides as prophylaxis
against pneumocystitis in HIV and immucompromised patients
sulfonamide interactions
increases the hypoprothrominemia effect of arfarin by inhibiting its metabolism
sulfonamide patient education
notify if rash, sore throat, mouth sores, unusual bleeding
avoid driving until response is known
stay hydrated to prevent crystalluria
sulfonamide conscientious considerations
watch for stevens-johnson syndrome
G6PD deficiency can lead to anemia
hypersensitivities can occur up to 12 days after exposure
fluroquinolones mechanism of action
inhibits bacterial DNA synthesis to prevent replication
fluroquinolones are effective against
most aerobi gram- bacteria and some gram+
examples of fluroquinolones
ciprofloxacin (Cipro)
gatifloxacin (Tequin)
gemifloxacin (Factive)
levofloxacin (Levoquin)
moxifloxacin (Avelox)
ofloxacin (Floxin, Ocuflox)
respiratory quinolones
gemifloxacin, levofloxacin, and moxifloxacin
all have good activity against PCN-resistant strains of pneumonia
cipro is used widely for
enteric infections (bacterial enteritis and diverticulitis)
UTIs (including prostatitis)
bone/joint infections
what drugs have approval to treat uncomplicated gonorhhea
oxyfloxacin, norfloxacin, gatifloxacin, and ciprofloxacin
minimum of 7 day treatment
what are special use ABTs used for
parasitic and bacterial infections
examples of special use ABTs
metronidazole (Flagyl)
daptomycin (Cubicin)
tigecycline (Tygacil)
Linezolid (Zyvox)
Quinupristin/dalfopristin (Synercid)
metronidazole (Flagyl)
mechanism of action
causes metabolites to accumulate in the susceptible organism which disrupts DNA and protein synthesis
clinical uses of flagyl
anaerobic bacteria and some protozoa
intestinal parasite Giardia
vaginitis
amebic dysentery
trichomoniasis
tx of c-diff
more page 332
flagyl interactions
cimetidine can reduce metabolism
phenobarbital can increase metabolism
alcohol causes disulfiram-like reaction
symptoms of disulfiram-like reaction
headache, dizziness, flushing, nausea, sweating, hyperventilation, disorientation
flagyl contraindications
hypersensitivities
first trimester of pregnancy
flagyl conscientious considerations
use with caution in CNS diseases (potential for neurotoxicity)
flagyl patient education
severe interaction with alcohol
possible furry tongue and metallic taste
may darken urine
may take with food if GI upset occurs
daptomycin (Cubicin)
mechanism of action
cyclic lipopeptide with rapid bacteriocidal activity against wide variety of gram+ and bacteria resistant to vancomycin and methicillin
(binds to bacterial cell membrane)
clinical uses of daptomycin
complicated skin and skin structure infections
s. aureua bacteremia
right sided endocarditis
daptomycin interactions
none clinically significant
manufacturer warns against statin drugs d/t risk of myopathy
what can be done to minimize the risk of daptomycin resistance
always drain any abcesses
tigecycline (Tygacil)
mechanism of action
inhibits bacterial protein synthesis by binding to 30S ribosomes
chemically similar to tetracyclines
administration of Tygacil
IV only
clinical uses of Tygacil
severe skin and soft tissue infections
complicated intra0abdominal infections with resistant pathogens (VRE, MRSA)
Tygacil interactions
oral contraceptives
tygacil contraindications
<18
pregnant/breastfeeding
linezolid (Zyvox)
mechanism of action
inhibits protein synthesis by binding to 50S ribosomal unit
treats nearly all gram+ resistant bacteria
major drawback of Zyvox
reversible thrombocytopenia
clinical uses of Zyvox
bacteriocidial: gram+ (sterptococci)
bacteriostatic: resistant enterococci and staphylococci
Zyvox interactions
dopaminergic, vasopressors, sympathomimetics should be reduced
(mild MAOI)
OTC cold medicines can increase BP
contraindications for Zyvox
not determined for pregnancy
caution with antiplatelets
quinupristin/dalfopristin
(Synercid)
mechanism of action
bacteriostatic
quinupristin inhibits late phase of protein synthesis
dalfopristin inhibits early phase of protein synthesis
Synercid clinical uses
treatment of infections with antibiotic resistant gram+ organisms
(VRE, MRSA, VREF)
Synercid interactions usually result in
increased risk of toxicity
listed page 335
pregnancy,geriatric, pediatric
page 336
