Download Microorganisms Responsible for Wound Infection on Human Skin

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Asian J. Res. Pharm. Sci. 2013; Vol. 3: Issue 2, Pg 68-71
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ISSN- 2231–5659 (Online) 0974-3618
REVIEW ARTICLE
Microorganisms Responsible for Wound Infection on Human Skin
S.K.Purohit*, R. Solanki
Ex-Director, College of Veterinary and Animal Science, Rajasthan
*Corresponding Author E-mail: [email protected]
ABSTRACT:
Skin is the major organ of the human body which plays a vital role in maintaining health of human being. Certain
diseases defined as infectious or communicable or transmissible diseases are caused by pathogenic microorganisms.
Some of the most common causative microorganisms related with infections include Staphylococcus aureus,
Streptococcus pyogenes, Enterococci, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Most of
the diseases spread by the bacteria which invade inside the body through skin. Bacterial infections on skin are the
common ailment for generation of other diseases in the body. Bacterial diseases are type of infectious diseases caused
by pathogenic bacteria. Symptoms and complications related with bacterial infections such as chills, headache, wound,
vomiting and organ failure generally affects the patient’s life. Wound on skin can occur in all ages of persons and can
causes harm in number of ways. Wound and skin infections represent the invasion of tissues by one or more species of
microorganisms. These infections disturbs the body immune system and causes inflammation, tissue damage and thus
resulting in delayed wound healing process. This article throws light on three aspects first on various types of
microorganisms found responsible for causing wound infection on the skin, second on laboratory tests to diagnose the
responsible microorganisms for wound infections and on choice of treatment for wound healing.
KEYWORDS: Skin, symptoms, bacteria, types of wound infection, diagnostic test, antibiotics.
INTRODUCTION:
Skin is the major organ of the human body. It collects
sensory information from the environment and functions as
a protective barrier to the human body organs. It helps in
maintaining the proper body temperature. Bacterial
infections on skin are the common ailment for generation of
other diseases in the body. Specially, the wound on skin
caused by bacteria produces very chronic results, if it is not
properly treated on time. The wound on skin can occur in
all ages of persons and can causes harm in number of ways.
Therefore for correct antimicrobial therapy for the treatment
of wound, proper identification of microorganism is
necessary so that wound healing activity can be accelerated
in less period of time1, 2. Wound is a break in the integrity of
the skin and tissues. It may be a superficial cut, scrap or
scratch. It may also include puncture, burn or may be the
result of surgical or dental procedures. The microorganisms
which are likely to infect the skin and tissues depend on the
wound extent, its depth, the environment in which it occurs
and the types of microorganisms present on the person skin.
Received on 31.03.2013
Accepted on 28.04.2013
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Asian J. Res. Pharm. Sci. 2013; Vol. 3: Issue 2, Pg 68-71
The skin consists of three layers: the outer epidermis, the
dermis where many hair follicles and sweat glands are
found and the fatty subcutaneous layer. Below these layers
are membranes that protect connective tissues, muscles and
bones. Wound can penetrate any of these layers and can
cause skin infections3-5.Wound and skin infections represent
the invasion of tissues by one or more species of
microorganisms. This infection disturbs the body immune
system and causes inflammation, tissue damage thus
resulting in delayed wound healing process. Many
infections remain confined to a small area like an infected
scratch or hair follicle which usually heals on their own.
Others may persist and if kept untreated may increase in
severity and may become cause of other chronic diseases.
Wound healing itself is a complex process which involves
many related systems, chemicals and cells working together
so as to clean the wound, heal its edges and to produce new
tissues and blood vessels6-9.
Signs and symptoms:
Common signs and symptoms of wound infection include
redness, warmth, swelling, tenderness and pus drainage
from the skin. Sometimes the skin may also become harden
or tighten in that particular area and red streaks may radiate
from the wound. Wound infections may also cause fevers,
especially when spread to the blood. Skin infections may
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also cause pustules, pain, scaling, and itching in that person skin and the immune status of the infected person. A
particular wounded area10.
deep puncture wound occurs mostly by anaerobic bacteria
such as Clostridium tetani.
Types of wound infections and types of microorganisms
responsible for wound infection:
Wound infections through burns:
Wounds may be typed according to their cause, their extent, Burns are generally caused by flammable liquids, fires,
the environment in which they occur and whether they are chemicals and electricity. First-degree burns involve the
clean or contaminated. The microorganisms that infects epidermis. Second-degree burns involve the dermis. Thirdskin and wound generally depends on immune system of degree burns involve all the layers of the skin and thus
the person, depth of the wound and the conditions of the damages the tissues below it. Initial infections tend to
surrounding environment.
bacterial. Fungal infections due to Candida, Aspergillus,
Fusarium, and other species may arise later since they are
Bacteria, virus and fungi can cause wound infections on not inhibited by antibacterial treatment. Viral infections,
skin (table 1, 2). Bacteria can be classified as per the such as those caused by the herpes simplex virus, may also
environment in which they grow: aerobic (grow in air), occur14-15.
microaerophilic (grow in reduced oxygen environment) and
anaerobic (grow in little to no oxygen). Microaerophilic and Wound infections after surgery:
anaerobic bacterias are generally found in deeper wounds Surgical sites are most commonly infected by exposure to
and abscesses11- 13.
microorganisms in the hospital environment. Hospitalacquired bacteria like MRSA. Deep surgical wounds
become infected both superficially with aerobic
Wound infections on superficial skin areas:
Superficial infections occur in the outer layer of the skin but microorganisms and deep within the body by anaerobes.
may also extend deeper into the subcutaneous layer. They
are caused by aerobic microorganisms; deeper wounds may Table 1: Microorganisms related with wound infections and their
also be infected with anaerobic microbes. Bacterial frequency of occurrence on skin
Pathogens
Frequency (%)
infections are typically caused by bacteria like
Staphylococcus aureus
20
Staphylococcus (Staph) and Streptococcus (Strep). They
Coagulase-negative staphylococci
14
may also be caused by antibiotic resistant bacteria like
Enterococci
12
MRSA (Methicillin Resistant Staphylococcus aureus).
Escherichia coli
8
Pseudomonas aeruginosa
8
Brackish water wound infection occurs due to waterborne
Enterobacter species
7
Vibrio or Aeromonas species. Hot tub-associated infection
Klebsiella pneumoniae
3
occurs by Pseudomonas aeruginosa. When wounds are
Streptococci
3
deeper, the possible pathogens would be anaerobes like
Candida albicans
3
Bacteroides and Clostridium species. Necrotizing fasciitis a
Other gram-positive aerobes
2
serious but uncommon type of infection often involves
Group A Streptococci, which are sometimes called as Table 2: Some potential wound pathogens category responsible for
“flesh-eating bacteria. Other common skin infections such wound infection
Pathogen Category
Name of pathogen
as ringworm and athlete’s foot are not caused by bacteria
Gram-positive cocci
Beta Haemolytic Streptococci
but by fungi. Yeast infections occur by Candida species
(Streptococcus pyogenes)*
which is generally found in the mouth (thrush) or on other
Enterococci (Enterococcus faecalis)
moist areas of the skin.
Staphylococci (Staphylococcus aureus/
MRSA)*
Gram-negative aerobic
Pseudomonas aeruginosa*
Wound infections through bites:
A wound infection due to animal bites tends to reflect the rods
Enterobacter species
microorganisms which are generally present in oral cavity Gram-negative
facultative rods
Escherichia coli
of animal which created the bite wound. They may involve
Klebsiella species
aerobic, anaerobic and microaerophilic microorganisms.
Anaerobes
Bacteroides
The most of the animal bites are from dogs and cats. The
Fungi
Yeasts (Candida)
Aspergillus
common bacteria found in these animals oral cavity is
*Most common causative microorganisms related with wound
Pasteurella multocida.
infections
Wound infections through trauma:
Trauma is a type of injury which occurs by the physical Laboratory tests to diagnose the microorganisms
force applied on the skin. It includes injuries from motor responsible for wound infections:
vehicle accidents, cuts from knives or other sharp A clinical evaluation cannot definitively tell the doctor
instruments and gunshot wounds etc. The type of wound which microorganism is causing a wound infection or what
infections that trauma victims acquires depend basically on treatment it is likely to be susceptible to. For that,
the environment in which the injury occurred, the extent of laboratory testing is required. Laboratory testing is
the injury, the microorganisms present on the affected primarily used to diagnose bacterial wound infections, to
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identify the microorganism responsible, and to determine its
likely susceptibility to specific antimicrobial agents.
Sometimes testing is also performed to detect and identify
fungal infections. Sample collection may involve swabbing
the surface of a wound to collect cells or pus with a needle
and syringe or biopsy16-18. For fungal evaluation, scrapings
of the skin may be collected. Test includes bacterial wound
culture, gram staining, antimicrobial susceptibility test and
fungal as well as urine cultures.
infection which is located in difficult area for drug therapy
to penetrate (such as bone) may require treatment with
intravenous medications. The antimicrobial drugs may act
by destroying the bacteria (bactericidal) or by inhibiting the
growth of bacteria (bacteriostatic). The mechanism of
action of these drugs can be divided into four groups33-36.
Drugs interfering with cell wall synthesis:
Penicillin, cephalosporin, bacitracin, vancomycin and
cycloserine. All β-lactum antibiotics bind to receptors
(penicillin binding protein at the cell wall -cell membrane
interface). After attachment of the β-lactum drug to the
receptor there is interference with the synthesis of
peptidoglycan of cell wall. This makes the cell membrane
vulnerable to damage by solutes of the environment
(plasma). The cell walls of gram negative bacteria being
more complex, these drugs cannot penetrate the cell in
adequate concentration.
Bacterial wound culture:
It is a primary test which is used to diagnose the bacterial
infection. The sample is streaked onto nutrient media and is
then incubated at body temperature so as to grow and
identify bacteria if any present in the sample or not. Growth
and identification of bacterial wound cultures is usually
available within 24-48 hrs from the time the sample is
received in the lab while for slow growing microorganisms,
such as fungi it may take several weeks for growth and its
identification19-20.
Drugs affecting cytoplasmic membrane:
Polymxcin B and colistin bind selectively with outer
Gram stains:
membranes of gram negative bacteria that are rich in
After the growth of microorganism in the culture media, phoshatidylethanolamine and act as cationic detergents. The
staining allows bacteria to be evaluated under the inhibition of cell membrane function leads to escape of
microscope. It involves smearing individual colony types macro molecules and ions from the cell resulting in cell
onto glass slides and treating them with a special stain. damage or death. Polyenes are effective against fungus
Under the microscope, the bacteria can be classified into which contains sterol on cell membrane. Bacteria generally
gram-positive and gram-negative organisms, there they are do not contain sterol on cell membrane and hence polyene
distinguished by their shape such as cocci (spheres) or rods is ineffective in bacterial infection.
(bacilli) and are easily separated by color into gram positive
or gram-negative microorganisms. This test provides Drugs inhibiting protein synthesis and impairment of
preliminary information about the quality and potentiality function of the ribosomes:
of microorganisms that may be causing the infection 21-26.
Aminoglycosides, tetracyclines, chloramphenicol and
macrolide antibiotics lincomycin inhibit protein synthesis in
Antimicrobial susceptibility:
bacterial ribosomes (70 S) without any major effect on
When a pathogen is identified and isolated using the wound mammalian ribosomes (80 S).
culture, this test is used to determine the bacteria likely
susceptibility to certain drug treatments. This information Drugs inhibiting synthesis of nucleic acid:
helps in selecting appropriate antibiotics for the These drugs interfere with transcription of genetic
treatment27- 31. Other tests may includes
information on the ribosomes. Rifampin binds with DNAdependent RNA polymerase, actinomycin binds with
Fungal culture:
deoxyguanosine residues and quinolones block the DNA
It is performed when a fungal infection is suspected32.
gyrase and thus they inhibit DNA synthesis of bacteria.
Urine culture:
It is performed when a urinary tract infection is suspected.
Treatments:
The risk of wound infection can be minimized with prompt
and proper wound cleansing and treatment. Most wound
infections that do occur can be successfully resolved. Many
superficial bacterial and viral infections will resolve on their
own without any kind of treatment. Other bacterial
infections may require some type of topical antimicrobial
drugs treatment. Deeper infections typically require oral
antimicrobial therapy. The choice of which type
antimicrobials drug is to be used is based upon the data
results of wound culture and antimicrobial susceptibility
tests. Patients with antibiotic resistant bacteria or with an
Choice of treatment:
The choice of which antimicrobials drugs to be used is
generally based upon the results of wound culture and
antimicrobial susceptibility tests. Susceptibility testing is
used to determine which antibiotic or antibiotic
combinations will be most effective in treating the different
types of bacteria causing the wound infection 37, 38, 39. The
test include following three terms:
Susceptible: Likely, but not guaranteed to inhibit the
pathogenic microorganism; may be an appropriate choice
for treatment.
Intermediate: May be effective at a higher dosage or more
frequent dosage or effective only in specific body sites
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where the antibiotic penetrates to provide adequate 21.
concentrations but drugs may produce higher risk for
medication side effects.
22.
Resistant: Not effective at inhibiting the growth of the 23.
organism; may not be an appropriate choice for treatment.
A combination of antibiotics that work together to inhibit
24.
the bacteria when neither one alone will be effective.
25.
CONCLUSION:
Bacterial infections are one of the most prominent causes of
chronic diseases and physical disabilities around the world.
The most common causative microorganisms related with
wound infections include Staphylococcus aureus/MRSA,
Streptococcus pyogenes, Enterococci, Escherichia coli,
Klebsiella pneumoniae and Pseudomonas aeruginosa.
These pathogens can be easily detected and identified by
using designed laboratory testing procedures and methods.
Thus by the help of wound culture and antimicrobial
susceptibility tests, we can easily find out appropriate
antimicrobial therapy for the particular pathogen
responsible for causing wound infection on human skin.
26.
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