The first question: why do we need an analysis for staphylococcus aureus? And then, that activation of this opportunistic bacterium and especially pathogenic Staphylococcus aureus (Staphylococcus aureus) leads to tissue damage by microbial toxins and enzymes with the development of almost a hundred diseases. In addition, individual strains secrete enterotoxins - the cause of mass food staphylococcal intoxications and toxic shock syndrome.
Under certain conditions of the colony St. Aureus, inhabiting the nasal passages and axillary cavities, the groin and perineal areas, can cause superficial skin lesions and abscesses of any location, deep intraorganic infections, and extensive nosocomial (hospital) infections in surgery and obstetrics. Staphylococcus saprophytic (St. Saprophyticus) is involved in the development of acute inflammation of the urinary tract. Epidermal staphylococcus (St. Epidermidis) - the usual commensal of human skin - penetrating through its damage inside, is able to infect blood (with the development of sepsis) and the inner shell of the heart with the development of its inflammation (endocarditis).
If we consider that about a third of people can be asymptomatic carriers of staphylococcus, and its ability to form biofilms allows it to survive in adverse conditions on many surfaces, the need for some cases to make an analysis for Staphylococcus aureus becomes evident.
Further on how to take an analysis of staphylococcus and where you can pass it, how often to take an analysis for staphylococcus, whether its result is erroneous and other useful information.
Indications for conduction
To date, the main indications for conducting this bacteriological study are related:
with the need to identify the cause of the inflammatory disease;
with differentiation of infections in nonspecific inflammatory diseases;
with the definition of sensitivity to antibacterial drugs to ensure the effectiveness of their use;
with preparation for surgical intervention (to reduce the risk of postoperative complications).
The analysis for staphylococcus in adults and children, given two weeks after the last reception of antibiotics, makes it possible to evaluate the effectiveness of antimicrobial therapy and prevent chronic inflammation.
In most cases, tests for staphylococcus in children are necessary if children often suffer from bronchitis or pneumonia: sputum is given for bacause.
The pediatrician can prescribe an analysis for staphylococcus in the infant in case of acute inflammation of the laryngeal mucosa or pharynx, as well as the intestines (with diarrhea of unknown etiology).
Against the background of all the tests required by pregnant women when applying to a women's consultation for registration, analysis of staphylococcus during pregnancy is done when there are problems with the bladder, there are uncharacteristic vaginal discharge for this condition, or the future mother had inflammatory diseases staphylococcal origin.
Techniques for conducting
To confirm the diagnosis, the patient's biomaterial sample is placed in a Petri dish - on the culture medium (which is called sowing). It can be a liquid or gel that provides nutrition for the growth of bacteria. For S. Aureus a mixture of agar, mannitol and 7-9% sodium chloride solution is used. The plates are then incubated overnight at + 37 ° C. After 48 hours yellowing of the agar plate on one side and typical golden colonies of S. Aureus are observed. They are necessarily stained with a Gram stain - to confirm that it is Gram-positive cocci.
Further, specific tests are carried out for the diagnostic identification of clinical isolates - tests with urea, nitrates, catalase, coagulase. Positive reactions serve as biochemical evidence of the presence in the test sample of Staphylococcus aureus.
The technique for carrying out the analysis for staphylococcus is quite complex, and the multistage process is associated with the need to differentiate it from similar microorganisms present in the biomaterial under study and to determine whether this bacterium belongs to enterotoxigenic or non-toxic species.
In emergency situations, rapid analysis of staphylococcus aureus by PCR (polymerase chain reaction) is carried out in clinical laboratories, which helps detect bacteria in real time and determine their number.
Analysis for carriage of staphylococcus aureus
Very important is the analysis of the staphylococcus culture from the nasopharynx: according to its results, the presence of S. Aureus bacteria is most often detected, which does not manifest itself in a healthy person with strong immunity, but may pose a danger of infection for others. And the level of colonization by staphylococci among medical workers, patients on dialysis and people with diabetes is higher than among the general population.
Approximately 30-35% of adults and most children are periodically healthy carriers of S. Aureus in the nasopharynx, but almost 15% of healthy adults are persistent carriers.
In the latter case, an analysis is required for staphylococcus aureus (sanitary book or special medical book - the form of the primary accounting documentation No. 1-OMC), which - by Cabinet of Ministers resolution No. 559 of 23.05. 2001 - there must be employees of certain professions (their list is attached). This is a bacterial staphylococcus or a test for the carriage of S. Aureus staphylococcus, for which a sample of nasal exudate (nasal seeding) or a mucous secretion of the oropharynx (smear from the pharynx) is examined.
We specify the number of the order for the analysis of staphylococcus, concerning the preventive medical examination - this is the order of the Ministry of Health of Ukraine №280 (from 23.07.2002). "The organization of obedient profiaktic medical examinations in prerequisites for vocational training, vibrobnits and organisations, yazana z obesluvovannanym populated area and can call to the widening of infectious wilderness. "
How often to take an analysis for staphylococcus aureus? Persons, whose profession is associated with the possibility of spreading bacteria, are supposed to take it every six months (some - once a year). To ordinary patients, the delivery of this test is prescribed by a doctor. In most cases, he also tells you where to pass the analysis for staphylococcus: in the laboratory of the medical institution, where the patient addressed, or in a separate accredited laboratory.
What analyzes hand over on a staphilococcus?
Depending on the localization of the pathology, the symptoms of its manifestation and the preliminary diagnosis for bacteriological research, such biomaterials as:
A smear from the mucous membrane of the nasal cavity and from the pharynx;
A smear from the outer mucosa of the eyeball (conjunctiva);
a sample of a clearing secretion (sputum);
discharge from the auricle;
Urine (the average portion of urine released after waking up in the morning);
a swab from the vagina (vaginal), from the cervical canal (cervical);
smear from the anus (rectal);
discharge from the wound (purulent exudate);
a sample of breast milk of a lactating mother.
A blood test for staphylococcus aureus (which is taken in the laboratory or in the hospital ward of patients prior to the initiation of antibiotic treatment) involves a subsequent tank sowing its sample on a culture medium with microscopic examination. And for greater accuracy of the definition of an infectious agent, a repeated analysis for staphylococcus is often performed.
Determine the presence of staphylococci in the blood in persistent carriers can be at significantly higher titers of antistaphylococcal serum antibodies detected by two-stage protein precipitation or ELISA.
In severe forms of acne or folliculitis, staphylococcal analysis may be required on the face (a swab from the elements of the rash is taken), and for diffuse furunculosis - to determine the tactics of treatment - dermatologists can prescribe skin analysis for staphylococcus aureus.
How to pass the test for staphylococcus aureus?
Urinalysis, stool analysis for Staphylococcus aureus, as well as analysis of breast milk for staphylococcus are collected in sterilized dry containers with a lid (for milk, two containers - separately for each breast) will be needed.
Preparation for the delivery of stool is to perform the necessary hygienic procedures and stop at least three days after the application of the laxative or probiotic (if any were taken). Two days before the delivery of urine stop taking diuretics.
Can be taken directly in the laboratory: sputum analysis, analysis of throat, throat and nose on staphylococcus. In this case, a smear from the pharynx is done not earlier than 4 hours after eating; Before a smear from a throat two hours do not drink and do not accept food; Before a smear from a nose it or him do not wash out and do not instill in anybody within three hours. And for 10 hours before the delivery of sputum, you should drink a couple of extra glasses of water.
How to take an analysis of staphylococcus a vaginal or a rectal smear is understandable: it is the competence of the examining physician who takes the sampling of the biomaterial and transmits the images to the laboratory, as appropriate.
It is difficult to say exactly how much the staphylococcus is being analyzed: clear instructions on the regulations for microbiological studies of each sample are only available in laboratories.
Analysis of Staphylococcus aureus
The standard interpretation of the staphylococcus analysis contains information on the number of bacteria and their growth. If an increase in their colonies is detected, this is a positive test for staphylococcus, and when there is no active growth, a negative analysis for staphylococcus occurs.
At the same time, the normal indicators of the number of microorganisms correspond to CFU (colony forming units) in one milliliter of the investigated biomaterial less than 102-103 cfu / ml, that is, when 10 2 -10 3 (100-1000) colony forming units were counted in one milliliter of the investigated biomaterial .
The carriage of S. Aureus is recognized at 103-104 cfu / ml, and to detect the cause of the inflammatory disease, a significant figure is ≥105 cfu / ml.
Epidemic danger is the presence of 10 million microbial bodies of Staphylococcus aureus in 1 ml of nasal exudate.
Whether there is an error the analysis on a staphilococcus? It happens, because this bacterium is usually present on the skin and mucous membranes, and the analysis is not always confirmed.
One of the problems that can prevent the achievement of a reliable result is an inadequate level of sterility of laboratory equipment during inoculation (introduction of the biomaterial into the nutrient medium). The slightest doubts as a result force the laboratory specialists to conduct a repeated analysis for staphylococcus aureus.
How to cheat the test for staphylococcus aureus? Before the swab from the nose, rinse the nasal passages carefully, and if a smear from the pharynx is to be applied, several times rinse the throat with an antiseptic.
Last update: 25.06.2018
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Medical expert editor
Portnov Alexey Alexandrovich
Education: Kiev National Medical University. A.A. Bogomolets, Specialty - "General Medicine"
Staphylococcus was discovered in 1878 by R. Koch and in 1880 by L. Pasteur in a purulent material. L. Pasteur, after infecting a rabbit, finally proved the role of staphylococcus as a pathogen of purulent inflammation.
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