Drugs for Bacterial Infections AntibioticsAntimicrobials Antinfectives

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Drugs for Bacterial Infections(Antibiotics/Antimi
crobials/Antinfectives)

• Chapter 22

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Pathogens (disease-causing organisms)

• May be viruses, bacteria, fungi, unicellular or
  multicellular animals
• May be ingested, inhaled, or enter through break
  in the skin
• Pathogenicity- a pathogens ability to
  bypass/overcome the immune system. Only a few
  dozen pathogens commonly cause human disease
  (Table 22.1)
• Virulence- ability to produce disease when
  present in very small numbers

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Bacteria Classification

• Shapes
• Rod (bacilli)
• Spherical (cocci)
• Spiral (spirilla)
• Gram stain
• Gram () -- retains stain, thick cell wall
• Gram (-) loses stain, thin cell wall
• Oxygen use
• Aerobic- thrives in oxygen
• Anaerobic- grows in oxygen absence

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Antiinfectives

• Generally target cellular structures or enzymes
  of the microbe that humans do not have (this
  helps avoid toxicity in humans)
• Bacteriocidal- kill bacteria
• Bacteriostatic- slow bacterial growth so immune
  system can dispose of organism

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Acquired Resistance

• Mutations- errors that occur in DNA as cell
  divides
• Usually harmful to a bacteria but can lead to its
  advantage (such as leading to drug resistance)
• After bacterial mutation, antibiotics may kill
  off all bacteria except those that are resistant.
  These bacteria are now free to replicate with
  abandon
• Unwarranted antibiotic use has led to numerous
  resistant strains the longer/more often an
  antibiotic is used in a population, the greater
  the percentage of resistant strains
• Fig 22.3

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Choosing an Antibiotic

• Broad spectrum antibiotic- effective against a
  wide range of types of bacteria
• Narrow spectrum antibiotic- effective only
  against specific families of bacteria
• Ideally, an organism should be identified
  (culture and sensitivity testing, CS testing)
  before administration of abx and a broad spectrum
  antibiotic is given until results return
• After identification, client is changed to a
  narrow-spectrum antibiotic

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Choosing an Antibiotic

• CS testing is not always feasible, so often,
  clients are treated with empiric therapy, in
  which an antibiotic is chosen based on the most
  likely organism
• Superinfection- occurs when normal, healthy
  bacteria are destroyed along with the pathogen.
  This is more common with broad spectrum
  antibiotic use
• Read Interventions and Rationales on pg 411-412

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Penicillins (Penicillin G)

• Old and very safe
• Have a beta-lactam ring which attacks bacterial
  cell wall
• Many bacteria have developed beta-lactamase
  (a.k.a. penicillinase) which splits the ring and
  provides resistance to the drug
• Uses- streptococci, pneumococci, gonorrhea,
  syphillis
• SE allergy

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Cephalosporins (cephotaxime)

• Also have beta-lactam ring attacks cell wall
• Classified according to generation- each
  successive generation is less susceptible to beta
  lactamase
• Uses- best for Gm (-) infections
• SE PCN-allergic patients may exhibit cros
  allergy to cephalosporins (10)

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Tetracyclines (tetracycline hcl)

• Very broad spectrum
• Overuse has led to significant resistance
• Avoid dosing with milk (binds to calcium)
• Uses Chlamydia, Lyme disease, Rocky Mountain
  Spotted fever
• SE tooth discoloration in children (avoid in
  pregnancy or breastfeeding) photosensitivity

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Tetracyclines (tetracycline hcl)Tooth staining
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Macrolides (erythromycin)

• Inhibit bacterial protein synthesis
• Short duration of therapy
• Uses Mycoplasma pneumoniae, chlamydia, PCN-
  allergy
• SE GI upset (administer with food)

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Aminoglycosides (gentamycin and vancomycin)

• Inhibit protein synthesis
• Highly toxic
• Uses severe aerobic Gm (-) infections (E.coli,
  Klebsiella, others)
• SE flushing, red man syndrome ototoxicity and
  nephrotoxicity may be permanent (check hearing
  and renal function), levels must be drawn

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Fluoroquinolones (ciprofloxacin)

• Broad spectrum, bacteriocidal
• Effective for respiratory, gastrointestinal, and
  gynecologic tracts, also some skin and
  soft-tissue infections
• Well absorbed orally administered 1-2x/d
• SE mild GI smptoms, take with food

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Sulfonamides (trimethoprim-sulfamethoxazole)

• Inhibit folic acid metabolism of bacterium
• Old many bacteria are now resistant
• Commonly used for UTIs
• Many patients are allergic to sulfur

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Tuberculosis

• Caused by Mycobacterium Tuberculosis, present
  since antiquity
• transmitted by the airborne spread of droplets
  containing the bacteria
• 14,000 cases in 2003 AIDS clients particularly
  susceptible
• typically affects the lungs, but may also occur
  in other organs
• When inhaled, a healthy immune system isolates
  the bacteria in a tubercle, after which the
  bacteria are either destroyed or go into a
  dormant state
• Most infections are asymptomatic/latent and not
  contagious, but can become active (symptomatic)
  if the immune system becomes depressed
• Symptoms persistent cough, weight loss, coughing
  up blood, fever, night sweats
• M. tuberculosis has an cell wall highly resistant
  to drugs, so therapy must continue for at least 6
  months many patients are not compliant, leading
  to resistant strains
• Most patients are treated with 2-4 drugs
  simultaneously to prevent further development of
  drug-resistant strains
• Directly Observed Therapy (DOT) combined with
  incentives such as food coupons can enhance
  compliance

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Antitubercular agents (isoniazid)

• Used alone in latent infections or in combination
  with other drugs for active infections
• Therapy generally lasts at least 6 months
• SE Liver damage, monitor liver function