Travel Reference
In-Depth Information
Thisdrugmustnotbegiventopeoplewithknownheartdisease;ittendstoproducecar-
diac arrest.
ANTIMICROBIAL AGENTS
Antimicrobial agents are used to treat established infections; antiseptics such as povidone-
iodine kill microorganisms on contact.
Bacteriaareclassifiedasgrampositiveorgramnegativeaccordingtotheirreactionwith
the gram stain; as cocci (spheres), bacilli (rods), or spirochetes (spirals); and as aerobic if
they are able to grow in the presence of oxygen or anaerobic if they cannot.
The Penicillins
Penicillin, the first antibiotic to be discovered, is still widely used and is effective treat-
ment for many common infections. Chemical modifications to penicillin have produced
a family of compounds, the penicillins. Penicillins actively kill bacteria (are bactericid-
al); some antibiotics just keep them from multiplying (are bacteriostatic). Organisms usu-
ally susceptible to penicillins include streptococci (strep throat, cellulitis, and impetigo);
Streptococcus pneumoniae
(conjunctivitis, pneumonia);
Neisseria meningitidis
(meningit-
is); and the spirochete that causes syphilis.
As antibiotic use has increased over time, some organisms formerly sensitive to penicil-
linsarenowresistant.Inthedevelopedworld,forexample,staphylococci(boils,abscesses,
and wound infections) are frequently resistant. Penicillins, including ampicillin and amox-
icillin/clavulanate(Augmentin®),arenolongerpredictablyeffectiveagainsttheorganisms
likely to cause gastrointestinal infections such as traveler's diarrhea, dysentery, or typhoid
fever.
Penicillin V is the penicillin most suitable for oral administration because it is resistant
todestructionbyacidinthestomach.Aqueouscrystalline penicillin Gisusedforintraven-
ous administration.
Infections should be treated with penicillin only if the causative organism is known to
be susceptible. Some bacteria produce the enzyme penicillinase (or beta-lactamase), which
destroys penicillin, but some penicillin preparations are resistant to penicillinase. In recent
years staphylococci have developed resistance even to these penicillins. These organisms
are known as methicillin-resistant
Staphylococcus aureus
(MRSA) even though methicil-
lin is no longer produced and the bacteria are resistant to the large group of antibiotics
called the beta-lactams, which include the penicillins and the cephalosporins. Such bacter-
ia are susceptible to a limited number of other antimicrobial agents such as trimethoprim-
sulfamethoxazole (TMP-SMX), clindamycin, and vancomycin.
Precautions:
The penicillins are usually very safe, but allergic reactions occur in a sig-
nificant number of the individuals receiving them. Most of these reactions consist of skin
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