Coagulase-negative staphylococcus:Description, Causes and Risk Factors:
Staph bacteria are noted as coagulase negative, if they do not coagulate during coagulase enzyme test. All staphylococci causing disease in human, (except Staphylococcus aureus) are coagulase negative and include:
Staphylococcus epidermidis (S. epidermidis).
- S. saprophyticus.
- S. lugdunensis.
- S. haemolyticus.
- S. hominis.
- S. cohnii.
- S. warneri.
Coagulase-negative staphylococcus is a common cause of nosocomial infections and the most common cause of bloodstream infections in the intensive care setting. Coagulase-negative staphylococcus is frequently reported in patients who are very-low-birth weight (VLBW) neonates, are immunocompromised (lymphoma, leukemia, post bone marrow transplantation), have signi?cant burns, or have indwelling intravascular devices, ventricular shunts, peritoneal catheters, or other implanted medical devices.
Epidemiological studies of Coagulase-negative staphylococcus infection is complicated by the fact that this organism is a normal commensal on the skin, and differentiating infection from colonization and contamination may be difficult. A very high proportion of clinical CONS isolates have the mecA gene associated with beta-lactam antibiotic resistance, which has implications for the choice of antibiotics administered. Coagulase-negative staphylococcus infections are associated with a signi?cant mortality and morbidity, including an increase in the duration of hospital stay and health care costs in adults and VLBW infants.
Thirty-eight species of CONS have been recognized, and 13 of them are known to colonize humans. Novobiocin susceptibility is useful in differentiating Coagulase-negative staphylococcus species into two groups. The novobiocin-resistant strains include Staphylococcus saprophyticus and Staphylococcus xylosus, with the former being well known to cause urinary tract infections in immune-competent women. Novobiocin-susceptible strains include Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus lugdunensis, and Staphylococcus schle?eri among others and are implicated in native valve endocarditis, foreign body infections, and infections in immune-compromised patients. S. epidermidis is the predominant clinical isolate; however, S. hemolyticus, S. hominis, S. lugdunensis, and S. warneri also have been implicated in sepsis and S. haemolyticus in endocarditis and osteomyletis.
Catheter-related infections: S. epidermidis is the most frequently isolated CNSS in catheter-related infections.
- CSF shunt infections: S. epidermidis and S. aureus are the most frequently encountered isolates in shunt infections. Usually occur within 2 weeks of implantation or manipulation.
- CAPD (continuous ambulatory peritoneal dialysis) peritonitis: S. epidermidis by far the most commonly isolated organism. ~40% of patients having CAPD develop peritonitis within the first year.
- Endocarditis: Infection of native valves is uncommon (~5% of all cases of infective endocarditis). S. aureus accounts for the majority of cases of nosocomial infective endocarditis. Causes ~40% of cases of prosthetic valve endocarditis, usually associated with valve dysfunction. Site of infection is most frequently the valve sewing ring. Results in complications such as dehiscence, arrhythmias, obstruction of the valve orifice. This site is relatively protected from antibiotics. Indolent clinical picture with absence of classical features of endocarditis (peripheral emboli, multiple positive blood cultures). Most patients become infected at the time of cardiac surgery. Incubation time: 2-13 months.
- Infections in the immunocompromised: Particularly affects neonatal ICU patients and oncology patients, usually associated with use of foreign devices, especially central venous catheters.
- Urinary tract infection: S. saprophyticus can cause UTI. Almost invariably occurs in women aged 16-25 who are not sexually active.
Generally, Coagulase-negative staphylococcus infections can range from minor skin problems to food poisoning, fatal pneumonia, surgical wound infections and endocarditis.So technically speaking, signs and symptoms of CONS infections vary widely, depending on the location and severity of the infection. It is also a factor whether your illness results from direct infection with staph bacteria or from toxins the bacteria produce.
In order to diagnose a CONSinfection, a healthcare provider will begin by asking questions regarding patient's medical history. This will include questions regarding the person's:
- History of medical problems.
- Current medications, including antibiotics.
- Family history of recent illnesses.
The healthcare provider will also perform a physical exam to look for signs of a Coagulase-negative staphylococcus infection. If the healthcare provider suspects a CONS infection or another type of bacterial infection, he or she may recommend certain tests to confirm the diagnosis.
In order for a CONS infection to be diagnosed, the healthcare provider may obtain a sample from the infection site and send it to a laboratory for testing. It takes about 48 to 72 hours for the results to come back. If staph is found, the organism will be further tested to determine which antibiotic will be the most effective treatment.
Newer tests that can detect staph DNA in a matter of hours are becoming more widely available. This will help healthcare providers decide on the proper treatment for a person more quickly.
When diagnosing more serious infections inside the body, healthcare providers may recommend x-rays, a computed tomography (CT) scan, and/or blood tests.
According to the researchers, more than 80 percent of the strains of Coagulase-negative staphylococcus produce an enzyme called beta lactamase that makes them resistant to methicillin and oxacillin. Vancomycin, telavancin, linezolid and daptomycin are the most common antibiotics used to treat infections caused by CONS. Rifampin and gentamicin may be added to the regimen to prevent antibiotic resistance. The researchers also states that single antibiotic regimens are often ineffective to treat CONS urinary tract infections and a combination of drugs should be used. Also, if the laboratory tests reveal that the strain of Coagulase-negative staphylococcus is methicillin sensitive, then oxacillin, ciprofloxacin and trimethoprim/sulfamethoxazole can be used for the treatment.
To treat most invasive CONS infections, the antibiotics are administered intravenously for at least 6 to 48 hours to control the infection. This can be followed by oral administration of the antibiotics for 2 to 4 weeks for complete cure. Superficial infections, such as those of skin, can be treated with oral antibiotics for 7 to 14 days. Common side effects for most antibiotics include nausea, vomiting, diarrhea and loss of appetite.
Fluids: Drinking large amounts of fluids is a natural way of speeding up the recovery from many infections including those caused by CONS. The large amounts of fluids help improve blood circulation, thereby improve the functioning of the immune system. Fluids also help flush out bacteria in the urinary tract. Fluids are also used to treat low blood pressure and shock that are associated with CONS infections of the bloodstream. Fluids can be administered intravenously to seriously ill patients using hypodermic needles and intravenous bags.
Antipyretics: Many invasive Coagulase-negative staphylococcus infections can cause fever, and antipyretics are drugs that can be used to bring down the body temperature. Acetaminophen, ibuprofen and aspirin are the common antipyretics that are available in the pharmacy without prescription and can be taken as and when required. In case of severe infections, these drugs may administered intravenously at the hospital. Most antipyretics are safe if the dosage directions are followed properly. However, some drugs such as aspirin should not be given to children younger that 18 years of age due to the risk of a serious side effect known as Reye's syndrome that can cause swelling of liver and brain.
Surgery: Surgery and other invasive procedures may be required to treat severe Coagulase-negative staphylococcus infections, especially if the antibiotic therapy is not effective. Removal of the contaminated catheters or stunts is recommended. Surgical drainage of the infection or the removal of the infected tissue may be required to treat CONS infections of prosthetic valves.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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