Staphylococcus aureus is the most dangerous of all staphylococci, of which there are many types.
These bacteria are spread by direct contact with an infected person, by using a contaminated object or by inhaling infected droplets that are dispersed by sneezing or coughing.
Skin infections are common, but bacteria can spread through the bloodstream and infect distant organs.
Skin infections can cause blisters, abscesses, and redness and swelling of the infected area.
The diagnosis is based on the appearance of the skin or the identification of the bacteria in a sample of the infected material.
Thorough washing of the hands helps prevent the spread of the infection.
Antibiotics are chosen based on their likely efficacy against the strain causing the infection.
The bacteria Staphylococcus aureus is present in the nose (usually temporarily) of about 30% of healthy adults and in the skin of about 20% of these. The percentages are higher in patients who are hospitalized or in those working in a hospital.
People who have the bacteria but do not have any symptoms caused by it are called carriers. People most likely to be carriers include those whose skin is repeatedly pierced or broken, such as:
Those who have diabetes mellitus and have to inject insulin regularly
Those who inject drugs or other similar substances
Persons being treated with hemodialysis or chronic ambulatory peritoneal dialysis
Affected by skin infections, AIDS or previous infections of the bloodstream by staphylococci
People can move bacteria from the nose to other parts of the body with their hands, which can sometimes lead to infection.
Patients can develop infection if they undergo surgery, are treated with hemodialysis or chronic ambulatory peritoneal dialysis or have AIDS.
The bacteria can spread from person to person through direct contact through contaminated objects (such as gymnastics equipment, telephones, door knobs, remote controls on the television or lift buttons), or less frequently by inhalation of Infected droplets dispersed by sneezing or coughing.
Infections by Staphylococcus aureus range from mild to life threatening. Bacteria tend to infect the skin (see Introduction to Bacterial Skin Infections ), often causing abscesses. However, bacteria can travel through the bloodstream (called bacteremia ) and infect virtually any part of the body, especially heart valves ( endocarditis ) and bones ( osteomyelitis ). Bacteria also tend to accumulate in the sanitary material implanted in the body, such as artificial heart valves or joint prostheses, pacemakers and catheters inserted into the blood vessels through the skin.
Some staphylococcal infections are more likely in certain situations:
Endocarditis: When people inject drugs, have a catheter in the blood vessels infected or have an artificial heart valve installed
Osteomyelitis: If Staphylococcus aureus spreads to bone from an infection of the bloodstream or from an adjacent soft tissue infection, such as may occur in people suffering from deep pressure ulcers or foot ulcers due to diabetes
Pulmonary(pneumonia) infection : When flu (especially) or sepsis has occurred, when corticosteroids or other immunosuppressive drugs (immunosuppressants) are taken, or when those affected have been hospitalized for tracheal intubation and mechanical ventilation (see Intrahospital pneumonia and pneumonia associated with health care ).
There are many strains of Staphylococcus aureus. Some strains produce toxins that can cause symptoms of food poisoning staphylococcus, toxic shock syndrome and scalded skin syndrome.
Risk factors for the development of staphylococcal infections
Certain circumstances increase the risk of staphylococcal infection:
Chronic lung disorders (such as emphysema due to cystic fibrosis)
A transplanted organ, an implanted medical device, or a catheter inserted into a blood vessel over a long period of time
Chronic skin disorders
Drugs, such as corticosteroids, immune-suppressing drugs (immunosuppressants), cancer chemotherapy, or injected illegal drugs
Resistance to antibiotics
Many strains have developed resistance to the effects of antibiotics; If carriers take antibiotics, they kill strains that are not resistant and survive mostly resistant strains. These bacteria can proliferate and, if they cause infection, it will be more difficult to treat.
Whether or not bacteria are resistant and to what antibiotics they are depends on where the infection has been acquired: in a hospital or other health care facility or outside such facilities (in the community).
Because antibiotics are widely used in hospitals, hospital staff often carry resistant strains. When people are infected in a health center, bacteria are often resistant to several types of antibiotics, including all antibiotics that are related to penicillin (antibiotics called beta-lactams). Strains of bacteria that are resistant to beta-lactam antibiotics are known as methicillin – resistant Staphylococcus aureus (MRSA).
MRSA strains are common if the infection is acquired in a health care facility, and there are increasing community-acquired infections, including abscesses and mild skin infections, which are methicillin-resistant strains of Staphylococcus aureus.
Did You Know…?
Staphylococcal infections can be difficult to treat because many of the bacteria have developed resistance to antibiotics.
Symptoms of Staph Infections
The skin infections by Staphylococcus aureus include:
The folliculitis is the least serious. The root of the hair (follicle) is infected, causing a small, painless pimple at the base of the hair.
The impetigo is shallow and fluid – filled blisters that break, leaving honey-colored crusts. Impetigo may itch or hurt.
The abscesses (boils) are hot and painful accumulation of pus just beneath the skin.
The cellulitis is an infection of the skin and tissue that lies just beneath it. Cellulite spreads and causes pain and redness.
The toxic epidermal necrolysis and in the newborn, the scalded skin syndrome, are serious infections. Both cause detachment of large amounts of skin.
All staphylococcal infections of the skin are very contagious.
The breast infections ( mastitis ), which may include cellulitis and abscesses, usually appear between 1 and 4 weeks after delivery. The area around the nipple is red and sore. Abscesses usually release a large amount of bacteria in the mother’s milk, which can infect the nursing baby.
The pneumonia staphylococcal usually causes high fever, shortness of breath and cough with sputum production which may be bloodstained. It causes lung abscesses, which spread and affect the membranes that surround the lungs (causing pleuritis) or sometimes causing accumulations of pus (empyema). These problems make breathing even more difficult.
The blood stream infection is a frequent cause of death in people with severe burns. Generally, high and persistent fever occurs, and in some cases, shock.
The endocarditis damages quickly heart valves, to the point of causing heart failure (breathing difficulties) and possibly death.
The osteomyelitis staphylococcal causes chills, fever and bone pain. Swelling and redness appear on the skin and soft tissues above the infected bone and fluid accumulates in the joints near this area.
Diagnosis of Staphylococcal Infections
In case of skin infections, a medical evaluation.
For other infections, blood culture and infected body fluids.
Staphylococcal skin infections are usually diagnosed by appearance. More serious staphylococcal infections require blood or infected liquid samples to make a culture of bacteria. The analytics establish the diagnosis and determine which antibiotics can eliminate staphylococci (sensitivity test ).
If the doctor suspects osteomyelitis, he / she performs x-rays, computed tomography (CT), nuclear magnetic resonance imaging (MRI), bone scans or a combination of them. These tests show the location of the damage and help determine its severity.
Prevention of Staphylococcal Infections
It helps to prevent the spread of these bacteria by always washing their hands thoroughly with soap and water or with antibacterial disinfectant gel for hands.
The bacteria are removed from the nose by applying the antibiotic mupirocin to the inside of the nostrils. However, since overuse of mupirocin causes resistance, this antibiotic is used only when people are prone to infection. For example, it will be administered to those who will undergo certain operations or people living in a house where there is a source of spread of infection of the skin.
People with a staph infection should not handle food.
In some health centers, people entering are routinely screened for MRSA. In some health centers only those persons who are at increased risk for an MRSA infection, such as those undergoing surgical procedures, are examined. Systematic examinations consist of the analysis of a sample taken from the nose with a swab. If SARM is detected, the person is isolated to prevent the spread of the bacteria.
Treatment of Staphylococcal Infections
Sometimes, surgical removal of infected bone and foreign material
Infections with Staphylococcus aureus are treated with antibiotics. The doctor tries to determine if the bacteria are resistant to antibiotics and, if so, to what antibiotics.
The infection that is acquired in a hospital is treated with antibiotics that are effective against MRSA: vancomycin, linezolide, tedizolida, quinupristina plus dalfopristina, ceftarolina, telavancina or daptomycin. If subsequent test results indicate that the strain is sensitive to methicillin and the person is not allergic to penicillin, a methicillin-related drug such as nafcillin is used. Depending on the severity of the infection, antibiotics may be given for weeks.
Methicillin-resistant Staphylococcus aureus (MRSA) infection can be acquired outside a healthcare facility. Community-acquired MRSA strains are often sensitive to other antibiotics such as trimethoprim-sulfamethoxazole, clindamycin, minocycline, or doxycycline, as well as antibiotics used to treat MRSA infections acquired in the hospital.
Mild skin infections due to MRSA, such as folliculitis, are usually treated with bacitracin, neomycin and polymyxin B (available over the counter) or mupirocin (available only on prescription) ointments. If more than an ointment is needed, effective antibiotics against MRSA are given orally or intravenously. The antibiotic used depends on the severity of the infection and the results of the sensitivity tests.
If an infection affects bone or materials implanted in the body (such as pacemakers, artificial heart valves, joint prostheses and blood vessel grafts), rifampicin is sometimes added to the antibiotic regimen. In general, infected bones and implanted material must be surgically removed to cure the infection.
If there are abscesses, it is usually convenient to drain them.
OTHER STAPHYLOCOCCAL INFECTIONS
Staphylococcus aureus produces an enzyme called coagulase; Other species of staphylococci do not produce it and are therefore called coagulase negative staphylococci. These bacteria usually reside in the skin of all healthy people.
These bacteria, although less dangerous than Staphylococcus aureus, cause serious infections, usually when acquired in a hospital. Bacteria can infect catheters introduced into a blood vessel through the skin, or implanted medical devices (such as pacemakers, artificial heart valves, and joint prostheses).
These bacteria are often resistant to many antibiotics. Vancomycin is used, which is effective against many resistant bacteria, sometimes associated with rifampicin. In case of infection, medical devices are likely to be removed.