Treatment for a wide range of bacteria
A colored electron microscopy image of methicillin-resistant staphylococcus aureus (
MRSA
), a bacterium commonly targeted by broad-spectrum antibiotics
A
broad-
spectrum
antibiotic
is an
antibiotic
that acts on the two major bacterial groups,
Gram-positive
and
Gram-negative
,
[1]
or any antibiotic that acts against a wide range of disease-causing
bacteria
.
[2]
These medications are used when a bacterial infection is suspected but the group of bacteria is unknown (also called
empiric therapy
) or when infection with multiple groups of bacteria is suspected. This is in contrast to a
narrow-spectrum antibiotic
, which is effective against only a specific group of
bacteria
.
[3]
Although powerful, broad-spectrum antibiotics pose specific risks, particularly the disruption of native, normal bacteria and the development of
antimicrobial resistance
. An example of a commonly used broad-spectrum antibiotic is
ampicillin
.
[3]
Bacterial targets
[
edit
]
Antibiotics are often grouped by their ability to act on different bacterial groups. Although bacteria are biologically classified using
taxonomy
, disease-causing bacteria have historically been classified by their microscopic appearance and chemical function. The morphology of the organism may be classified as
cocci
,
diplococci
,
bacilli
(also known as "rods"), spiral-shaped or pleomorphic. Additional classification occurs through the organism's ability to take up the
Gram stain and counter-stain
; bacteria that take up the crystal violet dye stain are referred to as "gram-positive," those that take up the counterstain only are "gram-negative," and those that remain unstained are referred to as "atypical." Further classification includes their requirement for oxygen (i.e., aerobic or anaerobic),
patterns of hemolysis
, or other chemical properties. The most commonly encountered groupings of bacteria include gram-positive cocci, gram-negative bacilli, atypical bacteria, and anaerobic bacteria.
[4]
Antibiotics are often grouped by their ability to act on different bacterial groups. For example, 1st-generation
cephalosporins
are primarily effective against gram-positive bacteria, while 4th-generation cephalosporin s are generally effective against gram-negative bacteria.
[
citation needed
]
Empiric antibiotic therapy
[
edit
]
Simplified diagram showing common disease-causing bacteria and the antibiotics which act against them.
Empiric antibiotic therapy refers to the use of antibiotics to treat a suspected bacterial infection despite lack of a specific bacterial diagnosis. Definitive diagnosis of the species of bacteria often occurs through
culture
of blood, sputum, or urine, and can be delayed by 24 to 72 hours.
[5]
Antibiotics are generally given
after
the culture specimen has been taken from the patient in order to preserve the bacteria in the specimen and ensure accurate diagnosis.
[4]
Alternatively, some species may be identified through a urine or stool test.
[4]
Risks
[
edit
]
Disruption of normal microbiome
[
edit
]
There are an estimated 38 trillion microorganisms that colonize the human body.
[6]
As a side-effect of therapy, antibiotics can change the body's normal
microbial content
by attacking indiscriminately both the pathological and naturally occurring, beneficial or harmless bacteria found in the intestines, lungs and bladder.
[7]
The destruction of the body's normal bacterial
flora
is thought to disrupt immunity, nutrition, and lead to a relative overgrowth in some bacteria or fungi.
[8]
An overgrowth of drug-resistant microorganisms can lead to a secondary infection such as
Clostridioides difficile
("C. diff") or
candidiasis
("thrush").
[3]
This side-effect is more likely with the use of broad-spectrum antibiotics, given their greater potential to disrupt a larger variety of normal human flora.
[7]
The use of
doxycycline
in
acne vulgaris
has been associated with increased risk of
Crohn's disease
,
[9]
although a later study indicated a link between
acne vulgaris
and
IBS
irrespective of the use of antibiotics.
[10]
Likewise, the use of
minocycline
in acne vulgaris has been associated with skin and gut dysbiosis.
[11]
Examples of broad-spectrum antibiotics
[
edit
]
In
humans
:
[
citation needed
]
In
veterinary medicine
,
co-amoxiclav
, (in small animals);
penicillin
&
streptomycin
and
oxytetracycline
(in farm animals);
penicillin
and
potentiated sulfonamides
(in horses).
References
[
edit
]
- ^
Ory EM, Yow EM (July 1963). "The use and abuse of the broad spectrum antibiotics".
JAMA
.
185
(4): 273?9.
doi
:
10.1001/jama.1963.03060040057022
.
PMID
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- ^
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Taber's Cyclopedic Medical Dictionary
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ISBN
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.
- ^
a
b
c
Hopkins SJ (1997).
Drugs and Pharmacology for Nurses
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ISBN
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.
- ^
a
b
c
Kasper DL, Larry Jameson J, Hauser SL, Loscalzo J, Fauci AS, Longo DL (2015-04-08).
Harrison's principles of internal medicine
(19th ed.). New York.
ISBN
9780071802154
.
OCLC
893557976
.
{{
cite book
}}
: CS1 maint: location missing publisher (
link
)
- ^
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"General principles of antimicrobial therapy"
.
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.
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- ^
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.
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ISBN
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.
- ^
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.
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.
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- ^
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"Potential association between the oral tetracycline class of antimicrobials used to treat acne and inflammatory bowel disease"
.
The American Journal of Gastroenterology
.
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doi
:
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.
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- ^
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.
Journal of the American Academy of Dermatology
.
88
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doi
:
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.
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.
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- ^
Thompson, Katherine G.; Rainer, Barbara M.; Antonescu, Corina; Florea, Liliana; Mongodin, Emmanuel F.; Kang, Sewon; Chien, Anna L. (2020-02-01).
"Minocycline and Its Impact on Microbial Dysbiosis in the Skin and Gastrointestinal Tract of Acne Patients"
.
Annals of Dermatology
.
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(1): 21?30.
doi
:
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.
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.
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- ^
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.
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.
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.
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.
- ^
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.
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.
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:
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.
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.
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.