antibioticsbooks

chapter 5 Adverse Consequences 43
from living on or in the body but do not cause
harm (within their ecologic niches). Colonization
with commensal organisms can be beneficial,
given that they compete with and crowd out
more pathogenic organisms. When administration
of antibiotics kills off the commensal flora,
pathogenic drug-resistant organisms can flourish
because of the absence of competition. This
is considered a superinfection (i.e., an infection
on top of another infection). For example,
administration of antibiotics can lead to the
overgrowth of the gastrointestinal (GI) pathogen
Clostridium difficile, which is clinically resistant
to most antibiotics. C. difficile can cause diarrhea
and life-threatening bowel inflammation.
Similarly, administration of broad-spectrum
antibacterial drugs can select for the overgrowth
of fungi, most commonly yeasts of the genus
Candida. Disseminated Candida infections carry
a high risk of mortality. To reduce the risk of the
impact of antibiotics on the commensal flora,
and thus the likelihood of superinfection, antibiotics
should be administered only to patients
with proven or probable infections, using the
most narrow-spectrum agents appropriate to
the infection for the shortest effective duration.
Antibiotic Resistance
Thousands of studies have documented the relationship
between antibiotic use and resistance,
both at a patient level (if you receive an antibiotic,
you are more likely to become infected with a
drug-resistant organism) and a society level (the
more antibiotics a hospital, region, or country