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Staphylococcus aureus tests from nose and throat, blood, urine, feces, breast milk
Last reviewed: 04.07.2025
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The first question: why do we need a staphylococcus test? Because the activation of this opportunistic bacterium and especially the pathogenic 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, colonies of St. aureus inhabiting the nasal passages and armpits, groin and perineum can cause superficial skin lesions and abscesses of any localization, deep intraorgan infections, as well as extensive nosocomial (hospital) infections in surgery and obstetrics. Staphylococcus saprophyticus (St. saprophyticus) is involved in the development of acute inflammation of the urinary tract. Epidermal staphylococcus (St. epidermidis) is a common commensal of human skin - penetrating through its damage inside, it is capable of infecting the blood (with the development of sepsis) and the inner lining of the heart with the development of its inflammation (endocarditis).
Considering that about a third of people may be asymptomatic carriers of staph, and that its ability to form biofilms allows it to survive in adverse conditions on many surfaces, the need to test for Staphylococcus aureus in some cases becomes obvious.
Next, about how a staph test is taken and where you can take it, how often to take a staph test, whether the results can be erroneous, and other useful information.
Indications for the procedure
Today, the main indications for this bacteriological study are related to:
- with the need to identify the cause of the inflammatory disease;
- with differentiation of infections in non-specific inflammatory diseases;
- with determination of sensitivity to antibacterial drugs to ensure the effectiveness of their use;
- with preparation for surgery (to reduce the risk of postoperative complications).
A staphylococcus test in adults and children, taken two weeks after the last dose of antibiotics, makes it possible to assess 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 submitted for bacterial culture.
A pediatrician may prescribe a staphylococcus test for an infant in case of acute inflammation of the mucous membrane of the larynx or pharynx, as well as the intestines (with diarrhea of unknown etiology).
Among all the necessary tests that pregnant women undergo when they visit a women's clinic to register, a staphylococcus test during pregnancy is done when problems with the bladder arise, vaginal discharge that is not typical for this condition appears, or the expectant mother has a history of inflammatory diseases of staphylococcal origin.
Technique of implementation
To confirm the diagnosis, a sample of the patient's biomaterial is placed in a Petri dish - on a culture medium (called a seed). This can be a liquid or gel, which provides nutrition for the growth of bacteria. For S. aureus, a mixture of agar, mannitol and 7-9% sodium chloride solution is used. The dishes 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 must be stained with a Gram stain - to confirm that these are gram-positive cocci.
Further specific tests are carried out for diagnostic identification of clinical isolates – tests with urea, nitrates, catalase, coagulase. Positive reactions serve as biochemical evidence of the presence of Staphylococcus aureus in the sample being studied.
The technique for conducting an analysis for staphylococcus is quite complex, and the multi-stage process is associated with the need to differentiate it from similar microorganisms present in the studied biomaterial, and to determine whether a given strain of bacteria belongs to enterotoxigenic or non-toxic species.
In emergency situations, clinical laboratories perform rapid analysis for Staphylococcus aureus using the PCR (polymerase chain reaction) method, which helps to detect bacteria in real time and determine their quantity.
Staphylococcus carriage test
A nasopharyngeal staph culture test is very important: its results most often reveal the presence of S. aureus bacteria, which do not manifest themselves in a healthy person with a strong immune system, but can pose a risk of infection to others. And the level of staph colonization among health care workers, dialysis patients, and people with diabetes is higher than among the general population.
An estimated 30-35% of adults and most children are periodically healthy carriers of S. aureus in the nasopharynx, but nearly 15% of healthy adults are persistent carriers.
In the latter case, a staphylococcus test is mandatory for the medical record (sanitary record or Special medical record - form of primary accounting documentation No. 1-OMK), which - according to the Cabinet of Ministers of Ukraine Resolution No. 559 of 23.05. 2001 - must be held by workers of certain professions (their list is attached). This is a bacterial culture for staphylococcus or an analysis for carriage of staphylococcus S. aureus, for which a sample of nasal exudate (sowing from the nose) or mucous secretion of the oropharynx (throat swab) is examined.
We clarify the order number for taking a test for staphylococcus regarding preventive medical examination - this is the order of the Ministry of Health of Ukraine No. 280 (dated July 23, 2002) “Before organizing obligatory preventive medical examinations of practitioners of other professions, industries and organizations whose activities are related to public services and may lead to an increase in infectious diseases.”
How often should I take a staph test? People whose profession involves the possibility of spreading bacteria are required to take it once every six months (some – once a year). For ordinary patients, this test is prescribed by a doctor. In most cases, he or she will also tell you where to take the staph test: in the laboratory of the medical institution where the patient has applied, or in a separate accredited laboratory.
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What tests are taken for staphylococcus?
Depending on the localization of the pathology, the symptoms of its manifestation and the preliminary diagnosis, the following biomaterials can be taken for bacteriological examination:
- smear from the mucous membrane of the nasal cavity and pharynx;
- smear from the outer mucous membrane of the eyeball (conjunctiva);
- sample of expectorated secretion (sputum);
- discharge from the ear canal;
- urine (the average portion of urine excreted after waking up in the morning);
- stool sample;
- smear from the vagina (vaginal), from the cervical canal (cervical);
- anal swab (rectal);
- discharge from the wound (purulent exudate);
- a sample of breast milk from a lactating mother.
A blood test for staphylococcus (which is taken in a laboratory or in a patient's hospital room before antibiotic treatment) involves subsequent bacterial culture of the sample on a culture medium and examination under a microscope. Moreover, for greater accuracy in determining the infectious agent, a repeat test for staphylococcus is often performed.
The presence of staphylococci in the blood of persistent carriers can be determined by significantly higher titers of antistaphylococcal serum antibody, detected by two-stage protein precipitation or enzyme-linked immunosorbent assay (ELISA).
In severe forms of acne or folliculitis, a staphylococcus test on the face may be required (a smear is taken from the elements of the rash), and in the case of diffuse furunculosis, to determine the treatment tactics, dermatologists may prescribe a skin test for staphylococcus.
How to get tested for staph?
Urine analysis, stool analysis for staphylococcus, and breast milk analysis for staphylococcus are collected in sterilized dry containers with a lid (for milk, you will need two containers - one for each mammary gland).
Preparation for stool collection involves performing the necessary hygiene procedures and stopping the use of laxatives or probiotics (if any) at least three days before. Two days before urine collection, stop taking diuretics.
The following can be taken directly in the laboratory: sputum analysis, analysis from the pharynx, throat and nose for staphylococcus. In this case, a pharynx smear is taken no earlier than 4 hours after eating; before the throat smear, do not drink or eat for two hours; before the nasal smear, do not rinse it or put any drops in it for three hours. And 10 hours before submitting sputum, you should drink a couple of extra glasses of water.
How a staphylococcus test is taken – vaginal or rectal swabs – is clear: this is the responsibility of the specialist doctor who prescribes the test, who collects the biomaterial and sends the appropriately packaged samples to the laboratory.
It is difficult to say exactly how long it takes to conduct a staph test: only laboratories have clear instructions on the regulations for conducting microbiological studies of each sample.
Decoding the analysis for staphylococcus
The standard interpretation of the staph test contains information about the number of bacteria and their growth. If an increase in their colonies is detected, this is a positive staph test, and when there is no active growth, this is a negative staph test.
In this case, normal indicators of the number of microorganisms correspond to CFU (colony forming units) in one milliliter of the studied biomaterial less than 102-103 CFU/ml, that is, when 102 -103 (100-1000) colony forming units were counted in one milliliter of thestudied biomaterial.
Carriage of S.aureus is recognized at 103-104 CFU/ml, and for identifying the cause of the inflammatory disease, a significant indicator is ≥ 105 CFU/ml.
The presence of 10 million microbial bodies of Staphylococcus aureus in 1 ml of nasal exudate poses an epidemic danger.
Is it possible to get a staph test wrong? It is possible, since this bacterium is usually present on the skin and mucous membranes, and the test is not always confirmed.
One of the problems that can prevent obtaining a reliable result is the insufficient level of sterility of laboratory equipment during inoculation (introduction of the taken biomaterial into the nutrient medium). The slightest doubts about the result force laboratory specialists to conduct a repeat analysis for staphylococcus.
How to cheat a staph test? Before a nasal swab, thoroughly rinse your nasal passages, and if you are going to take a throat swab, rinse your throat with an antiseptic several times the day before.