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Staphylococcal infections are different type of infections which are caused by different types of Staphylococcal aureus (S. aureus) which are gram positive cocci and are responsible for most of the infections. S.aureus is present on the epithelial surface and often found in the inner part of nose and buttocks. S.aureus is considered to be pathogenic organism which is present in the skin and almost 20% of population host the organism on the nasal mucosa without any pathogenic event. S. aureus develop antimicrobial resistance against the number of antibiotics which is ever increasing challenge in the treatment of Staphylococcal infection. S.aureus may cause infection in any age and is irrespective of any form may be epidemic or sporadic. The common cause of staphylococcal infection includes pyogenic exudates. Infection can be classified as: Localised infection Localised infection with the production of toxins Systemic or invasive infections Staphylococci were not considered as lab contaminated but in the 1960s the bacteria was considered to be potent for infection in number of patients. Infection caused by the organisms is nosocominal. Staphylococci are also responsible for the urinary tract infection in females. In most cases infection can be found in premature infants and patients suffering from pneumonia. Infection may also be caused by foreign bodies such as medical equipments e.g. catheters etc.
Children, teenagers and young adults are more susceptible to the staphylococcal infection because of the underdevelopment of immune system.
For example, 10% of the reported skin diseases in young children are impetigo. Invasive staphylococcal infections are observed less than skin infections but the outcome of invasive infection are very serious. Invasive staphylococcal infections are more harmful than skin infections because once they enter into the blood stream they can cause multiple organ failure and decrease in blood pressure due to the multiplication and release of toxins. This stage of infection is known as sepsis. Endocarditis form of invasive infection can lead to heart failure and is quite common in England. There are 32 species of staphylococci are known out of which
29 are coagulose negative. S.aureus is positive coagulose species. The cell culture of staphylococci composed of outermost cell wall which is composed of peptidoglycon comprising of teichoic acid and a number of proteins. S.aureus consists of a unique protein which binds to an immunoglobin. S.aureus is acquired by the host human after the birth and is colonized on the skin and gastrointestinal tract. The negative coagulose species become the normal flora of the skin. The nasal mucosa covers about 32% of the bacteria.
The various virulence factors expressed by s. aureus include surface proteins and wall teichoic acid (TA) which facilitate the adhesion of the organism to the damaged tissue moreover it is responsible for the malfunctioning of neutrophil and reduce the anitibody and immune response. Various enzymes and exotoxins are secreted by the organism which results in causing variety of disorders related to skin and systemic infection, eg., Staphylococcal Scaldoed Skin Syndrome (S.S.S.S.), Neonatal Toxic Shock Syndrome (NTED), Toxic Shock Syndrome
S. aureus, in the first stage of invasion adhere to the skin resulting in the disruption of epithelial barriers namely desmosomes and junctions of adhesion. The invaded organism which is present in the human epithelium tends to use various strategies to survive and persist in the host.
S. aureus use various strategies such as invasion, evasion and formation of toxins for the production of infections.
The various steps are discussed below:
1) Epithelial barrier disruption: Addition of S. aureus to epithelial cell is cilitated by the surface protein and TA (wall teichoic acid) and results in the secretion of α-hemolysin which results in the formation of pores over the membrane of the cells. The various cellular activities of the particular epithelial cell as well as the neighbouring cells inhabited by the diffusion of toxins. The initial results system malfunctions of cells resulting induced systemic inflammatory response syndrome (S.I.R.S.). S. aureus results in the tissue dysfunction which facilitates the organism to infect the epithelium.
2) Stophylococcol scalded skin syndrome (SSSS): This syndrome affects most children and newborns and nearly adults because of underdeveloped immunity in young people. Other reason for high incidence of SSSS in children is the lower level of toxin clearance by the renal system. In this particular case the action of S. aureus is at the localised area and not through the blood
3) Inhibition of chemotoxins: S.aureus secretes inhibitory protein for chemotoxins which results in the binding of receptor for formyl peptide. It results in the inhibitory action on the surface of the neutrophil.
4) Biofilm formation: Bacteria tends to adhere to damaged tissues and the medical implanted in form of glycocolyx which is a polysacride produced by the bacteria. The polysaccrharide is in a form of slim layer and bacteria are enclosed in the hydrated matrix. Biofilms are produced by the bacteria on the damaged cells hence the activity of antimicrobial agent does not work because of lack of neutrophils. Hence glycocolyx has import role in the bacteria adhesion to the damaged
5) It is the formation of cascade in response to the increased cell density. S.aureus produces quoron sensing to target the cells which are protected by biofilm.
Types of infections Staphylococcal was first found to be resistant against penicillin G in 1942 later in 1960s β-lactumase resistance penicillin including methicillin were used for staphylococcal infection, but soon the organism was found to be resistant to methicillin.
Staphylococcal infections can be classified in different groups:
Infection causing skin disorders: These infections occurs when the bacteria enters into the host's skin.
Boils: In this infection red watery bumps formed due to the infected hair follicles.
Impetigo: These are of 2 types:
Non-Bollous Impetigo: It this infection the formation of sores which later when ruptured develops yellowish brown crush.
Bollous Impetigo: Large watery blisters formation takes place in bollus impetigo.
Cellulitis: Cellulitis occurs in the deep layer of the skin and subcutaneous tissue. This infection results in the rashes on the skin and other symptoms include shivering and high body temperature.
Systemic infections: Skin infections caused by staphylococcal aureus may develop other systemic complications due to lack of immunity. Use of medical equipment such as catheters, prosthetic joints etc., may also develops the infection.
Food poisoning: Staphylococcal aureus sometimes leads to the contamination of food which may cause food poisoning.
Sepsis: This infection of staphylococcal aureus includes elevated body temperature, diarrhea, fast breathing, tachycardia and hypotension.
Toxic Shock Syndrome: Toxic shock syndrome is caused by staphylococcal aureus and occurs when the strains enter the blood stream and start releasing toxins. This can be characterized by decrease in the blood pressure of individuals.
Arthritis: Arthritis is an infection takes place in joints by staphylococcal aureus. The symptoms include swelling of joints, tenderness around the joints.
Diagnosis Staphylococcal skin infections:
Diagnosis of Staphylococcal skin infection can be made by the visual examination of the affected area of skin. Tissue can be removed from the affected area using a swab and can be tested for the presence of S.aureus bacteria. Once the presence of the bacteria is confirmed after laboratory examination, the can be treated Food poisoning caused by Staphylococcal bacteria Samples of stool are examined for the presence of bacteria in case of food poisoning caused by Staphylococcal bacteria.
Invasive infections of Staphylococcal bacteria Diagnosis of invasive infection involve four main objectives:
Confirmation of whether the infection has been caused by S. aureus bacteria the find out whether strain of bacteria has developed a resistance against any antibiotic source of the infection determination of other body functions, whether affected and how badly. Various tests such as blood, urine, stool sample, blood pressure and wound culture are done in order to achieve the above objectives. blood tests, urine tests, stool sample tests, blood pressure tests, a wound culture test - where a small sample of tissue, skin, or fluid, is taken from the affected area for testing, respiratory secretion testing - which involves testing a sample of saliva, phlegm, or mucus, imaging studies, such as an X-Rays or CT scans, echocardiogram - where sound waves are used to scan the valves and chambers of the heart, kidney and liver function tests, and a spinal tap - where a sample of cerebrospinal fluid is extracted from your back for testing (cerebrospinal fluid is the fluid that surrounds and protects the brain and spinal column).
There are various factors which define the treatment of the patient for staphylococcal infections such as: immune status of the patient, laboratory test data and hospital epidemiology. Lack of clinical response is only observed due to the microbial resistance. Drug concentration in the biochemical milue and anatomical physiological space are the other factors to be considered in the treatment. The use of antibiotics like amoxicillin, piperacillin, ampicillin and ticarcillin is limited due to production of β-lactumase by staphylococci. However, use of antibiotics like penicillin V or penicillin G is acceptable in methicillin susceptible isolates and nonpenicillinase producing staphylococci. In the treatment of β-lactumase producing methicillin susceptible staphylococci penicillinase-resistant antibiotics including nafcillin, cloxacillin, oxacillin, dicloxacillin and methicillin are better choices. First generation cephalosporins are also good choices in the treatment methicillin susceptible staphylococci.
β-lactumase susceptible penicillins and β-lactumase inhibitors in a fixed combination are observed good in the treatment. Antibiotics like imipenem and fluoroquinoles are active but resistance development is observed (Christian, 1996). Another antibiotic vancomycin showed poor clinical response in patients with endocarditis, but observed good against methicillin resistant organisms. Careless use of vancomycin can also lead to the increased resistance towards antibiotics. Fluoroquinoles are active against methicillin-resistant staphylococci isolates but they resistance is observed very rapidly. One study proved that trimethoprim-sulfamethoxazole is active but not as efficient as vancomycin. In case of methicillin resistance vancomycin is the antibiotic of choice against staphylococcal infections. Various ideas are proposed for the eradication of methicillin-resistant S.aureus. The best candidate for the eradication of methicillin-resistant S.aureus is mupirocin because of its ability to inhibit protein synthesis and bacterial RNA. Continuous application of mupirocin for 5 to 7 days intranasally helps in the eradication of S.aureus nasal carriage. However, later after 1 or 3 months recolonization of S.aureus is observed and resistance to mupirocin is gained. There is a continuous need for the search of new antibiotics which are resistant to S.aureus.
There are three different mechanisms of resistance to β-lactum antibiotics: β-lactumase mediated resistance: This mechanism is initiated by the extracellular enzyme which in activate the β lactum ring of penicillin by hydrolysis. There is inhibition of β-lactumase production by staphylococci. Three different processes can be used in lab to check the β-lactumase production can be checked in laboratory mainly by chromogenic cephalosporin method, acidometric method and iodometric method. Methicillin resistance: This resistance is due to the alteration of the membrane bound protein known as penicillin binding proteins. These proteins are required for the cross linking of the peptidoglycon and moreover are the target site of the β-lactum antibiotics. Heteroresistance is the phenomenon in which culture population having two
different species in which one is resistance to Methicillin where as the
other is susceptible. This is applicable to S.aureus and coagulose negative
staphylococci. Tolerance: The mechanism of tolerance results in the inhibition of β-lactum antibiotics to activate the autolytic enzyme
is present in the cell wall of the S.aureus. Clinically the importance
tolerance is not clear but tolerance contributes a major role in the
chronic infection. Other antimicrobial factors: Staphylococci is found
be resistant to various antibiotics like rifampin, quinolons,
glycopeptides, trimethoprim-sulfamethaxazole, tetracycline and
The resistance to these antibiotics is observed in
and Methicillin-susceptible isolates. Prevention and control
skin infections You can reduce your chances of developing a
skin infection by washing your hands regularly, keeping your skin clean
having a bath every day, and keeping any cuts clean and covered. If you
come into contact with someone with a staphylococcal skin infection,
should wash your hands thoroughly using warm water and soap if you
the infected site, or the pus that it produces. If you have a
staphylococcal skin infection, you should remove any pus that appears
the infected area immediately in order to prevent the infection from
spreading from one part of your body to another. You should then clean
area with antiseptic, or an antibacterial soap. As S. aureus bacteria
easily transmitted from one person to another, towels, washcloths, and
linen that are used by someone with a staphylococcal infection should
be used by anyone else. They should be changed daily until the symptoms
disappear and washed separately in hot water with bleach.
food poisoning The best way to prevent staphylococcal food poisoning is
ensure that food is both properly cooked and properly chilled. Cooking
properly Make sure that the food is cooked right the way through and is
piping hot in the middle. With meat, you can do this by inserting a
and if the juices that come out are clear, and there is no pink or red
left, the meat is fully cooked. Some meat, such as steaks and joints of
beef, or lamb, can be served rare (cooked for a short time in order to
retain the juices of the meat) as long as the outside has been cooked
properly. If you reheat food, make sure that it is piping hot all the
through, and never reheat food more than once. Chilling food properly
important to keep certain foods at the correct temperature in order to
prevent harmful bacteria from growing and multiplying. Always check the
label on the packaging for the correct storage instructions. Food that
needs to be refrigerated should always be stored in the fridge. If food
that needs to be chilled is left standing at room temperature, bacteria
grow and multiply to dangerous levels. You should set your fridge to a
temperature of between 0-5C (32-41F). Cooked leftovers should be cooled
quickly, ideally within 1-2 hours, before being put in the fridge or
freezer. Putting food in shallow containers and dividing it into
amounts will speed up the cooling process. Invasive staphylococcal
infections If you have an increased risk of developing a staphylococcal
infection because you have a weakened immune system, you will need to
extra precautions to safeguard you against infection. These are listed
Avoid smoking - smoking will weaken your immune system.
Do not use illegal drugs - illegal drugs will also weaken your immune
Eat a healthy diet - this will boost your immune system.
Take regular exercise - this will boost your immune system.
Wash your hands regularly - particularly after going to the toilet,
and after preparing food, and after spending time in crowded places.
Discussion Staphylococcal infections are responsible for wide range of
infections ranging from impetigo, subcutaneous abscess, toxic shock
syndrome (TSS), blood poisoning, endocarditis, furuncle and
scaled skin syndrome (SSSS). Staphylococcal infections are also
with microbial virulence factors. Staphylococcal aureus shows wide
virulence factors with different properties such as antibody and
optimization inhibition, neutrophils cytolysis, epithelial barrier
disruption, interference with neutrophil chemotaxis and also the
antimicrobial peptides inactivation. Acantholytic infection of S.aureus
responsible for the spread of pathogenic organisms within the
Exotoxins expressed by S.aureus have biological properties of
which lead to the activation of T-cell. In healthy adults
leukocidin (PVL) is responsible for the development of multiple
Antibiotic resistance to staphylococcal is a major problem and is
from a long time ago. There are basically three resistance mechanisms
play a important role. Staphylococcal is found to be resistant to new
more potent antibiotics. Immunological strategies based on vaccine
production can be a good solution for the problem. Most of the
immunological strategies are based against the staphylococcal surface
factors like teichoic acid and soluble virulence determinants. To avoid
staphylococcal infections there is a need of proper control measures in
hospitals in homes also.