Infections caused by staphylococci. Methicillin-resistant Staphylococcus aureus - pathogens of nosocomial infections: identification and genotyping
They belong to the Micrococcoceae family. The genus Staphylococcus includes 19 species, of which only a few are pathogenic for humans: S.aureus, S.epidermidis and S.saprophyticus. Diseases are caused by aureus, less often by epidermal and even less often by saprophytic staphylococci.
Morphology, physiology. Individual cells have the shape of a regular ball; when they multiply, they form clusters in the form of bunches of grapes (slaphyle - bunch of grapes). Size from 0.5 to 1.5 microns. In preparations from pathological material (from pus) they are located singly, in pairs or in small clusters. Staphylococcus aureus has the ability to form a delicate capsule.
Staphylococci are facultative anaerobes, but develop better in aerobic conditions, Gr+. On the surface of dense nutrient media they form round, convex, pigmented (golden, fawn, lemon yellow, white) colonies with smooth edges; in liquids - uniform turbidity. In laboratories, they use the ability of staphylococci to multiply in environments with large amounts (6-10%) of NaCl ( JSA). Other bacteria cannot tolerate such a concentration of salt; salt environments are selective for staphylococci. Strains of Staphylococcus aureus that produce hemolysins give colonies on blood agar, surrounded by a zone of hemolysis.
Staphylococci have a number of enzymes that break down many carbohydrates and proteins. The test for glucose fermentation under anaerobic conditions has differential diagnostic significance. Of the enzymes involved in the pathogenesis of staphylococcal infections, only plasmacoagulase and partially DNase are characteristic of S.aureus. Other enzymes (hyaluronidase, proteinase, phosphatase, muromidase) are variable (but are more often produced by S.aureus). Staphylococci synthesize bacteriocins. Resistant to penicillin (penicillinase).
Antigens. Cell wall substances: peptidoglycan, teichoic acids, protein A, type-specific agglutinogens, as well as a capsule of polysaccharide nature. Peptidoglycan shares common antigens with peptidoglycans from micrococci and streptococci. The antigenicity of teichoic acids is associated with amino sugars. Protein A of Staphylococcus aureus is capable of nonspecific binding to the Fc fragment of IgG, and therefore it is agglutinated by normal human serum. Staphylococci have 30 protein type-specific antigens. But intraspecific differentiation by Ar structure is not used in practice.
Pathogenicity. Toxins and enzymes have a damaging effect on the cells and tissues of the human body. Pathogenicity factors also include the capsule, which prevents phagocytosis and fixes complement, as well as protein A, which inactivates complement and inhibits opsonization when interacting with the Fc fragment of IgG.
S.aureus is capable of secreting a number of toxins, in particular leukocidin, which has a detrimental effect on phagocytic cells, mainly macrophages. Hemolysins (α, β, delta, γ) have a lysing effect on human and animal erythrocytes (rabbit, horse, sheep). The main one is α-toxin produced by S. aureus. In addition to hemolytic, this poison has a cardiotoxic effect and causes spasms coronary vessels and cardiac arrest in systole, it affects nerve cells and neurons, lyses cell membranes and lysosomes, which leads to the release of lysosomal enzymes.
The occurrence of staphylococcal food poisoning is associated with the action of enterotoxins produced by Staphylococcus aureus. There are 6 known antigens of various enterotoxins (ABCDEF).
Exfoliative toxins cause pemphigus, local bullous impetigo, and a generalized scarlet-like rash in newborns. The diseases are accompanied by intraepidermal detachment of the skin epithelium, the formation of merging blisters, the fluid in which is sterile. Focus staphylococcal infection It is most often located in the umbilical wound.
Exoverments: plasmacoagulase carries out plasma coagulation (proteins seem to be dressed in a fibrous cover that protects them from phagocytosis). Large concentrations of coagulase in the patient’s body lead to a decrease in peripheral blood clotting, hemodynamic disturbances, and progressive oxygen starvation of tissues.
Hyaluronidase promotes the spread of staphylococci in tissues. Lecithinase destroys lecithin, which is part of cell membranes, causing leukopenia. Fibrinolysin dissolves fibrin, delimiting the local inflammatory focus, thereby promoting generalization pathological process. The pathogenetic properties of other staphylococcal exoenzymes (DNase, muramidase, proteinase, phosphatase), which often accompany coagulase activity, have not yet been determined.
Ecology and distribution. In the first days of a person’s life, staphylococci settle on the mucous membranes of the mouth, nose, intestines, as well as on the skin, and are part of the emerging normal microflora of the human body.
Staphylococci constantly enter the environment from humans. They are present on household items, in the air, in water, in soil, and on plants. But their pathogenic activity is different, special attention is given to Staphylococcus aureus as potentially pathogenic for humans. Upon contact with a source of infection, not all people become carriers of S. aureus. The formation of bacterial carriage is facilitated by the low content of SIgA in nasal secretions and other manifestations of functional deficiency of the immune system. In such persons, resident carriage is formed, i.e. The nasal mucosa becomes the permanent habitat of staphylococci, on which microorganisms multiply intensively and are released into the environment in massive doses. IN medical institutions their source is patients with open purulent-inflammatory processes (the infection is transmitted by contact). This is facilitated by the long survival of staphylococci on surrounding objects.
They tolerate drying well, the pigment protects them from the harmful effects of sunlight (direct sun rays they are killed only after a few hours). At room temperature, they remain viable on patient care items for 35–50 days, and on hard equipment for tens of days. When boiled, they die instantly, are sensitive to disinfectants, to brilliant green, which allows it to be widely used for the treatment of superficial inflammatory skin diseases.
Pathogenesis of human diseases. Capable of infecting any tissue of the human body. These are local purulent-inflammatory processes (furuncles, carbuncles, wound suppuration, bronchitis, pneumonia, otitis media, sore throat, conjunctivitis, meningitis, endocarditis, enterocolitis, food poisoning, osteomyelitis). The generation of any form of local process ends with sepsis or septicopyemia. People with immunodeficiency conditions develop staphylococcal infections more often.
Immunity. Adults are resilient because... have natural protective mechanisms and specific antibodies that are acquired throughout life through contact with patients and carriers. In the process of staphylococcal infection, sensitization of the body occurs.
Both antimicrobial, antitoxic and antienzyme antibodies are important in the formation of immunity. The degree of protection is determined by their titer and site of action. Big role secretory IgA plays a role, providing local immunity of the mucous membranes. Antibodies to teichoic acids are detected in the blood serum of adults and children with severe staphylococcal infections: endocarditis, osteomyelitis, sepsis.
Laboratory diagnostics. The material (pus) is subjected to bacterioscopy and inoculated on nutrient media. Blood, sputum, and feces are examined using the bacteriological method. After isolating a pure culture, the species is determined based on a number of characteristics. In the case of S.aureus isolation, plasmacoagulase, hemolysin, and A-protein are determined.
Serodiagnosis: RP (alpha toxin), RNGA, ELISA.
To establish the source and routes of spread of infection, isolated cultures are phagotyped. Laboratory analysis certainly includes determining the sensitivity of the isolated culture or cultures to antibiotics.
Prevention and treatment. Prevention is aimed at identifying S.aureus carriers, mainly among personnel medical institutions, for the purpose of their rehabilitation. Particular attention is paid to the prevention of staphylococcal infections in newborns.
For the treatment of acute staphylococcal diseases, antibiotics are prescribed, the choice of which is determined by the sensitivity of the isolated culture to a set of drugs. For septic processes, anti-staphylococcal immunoglobulin or anti-staphylococcal plasma is administered. For the treatment of chronic staphylococcal infections (chroniosepsis, furunculosis, etc.), staphylococcal toxoid and autovaccine are used, which stimulate the synthesis of antitoxic and antimicrobial antibodies.
. Guidelines MUK 4.2.1890-04 “Determination of the sensitivity of microorganisms to antibacterial drugs.”Main epidemic strains and clones MRSA
|
The restriction results are presented in (34). Primer sets for type identification SCC mec
5.2.5.3. Identification of genes that determine the synthesis of enterotoxins A(sea), B(seb), C(sec) and toxic shock syndrome toxin (tst-H)To identify genessea, seb, secmultiplex PCR is used. The composition of the reaction mixture is standard. Primer concentration for gene detectionsea- 15 pkm/µl, seb, sec- 30 pkm/µl. To determine the gene tst - H concentration of MgCl 2 in the reaction mixture - 2.0 mM, primer concentration - 12 pkm/μl. Amplification mode No. 1 Primer sets for gene identificationsea, seb, sec
. Organization of epidemiological surveillance of nosocomial infections caused by MRSASurveillance of MRSAis an integral part of epidemiological surveillance of nosocomial infections and includes the following components: Identification, recording and recording of all cases of nosocomial infections caused by MRSAand confirmed by the results of microbiological studies; Identification of colonized patients MRSA (according to epidemic indications); Determination of the resistance spectrum of isolates MRSA to antibiotics, antiseptics, disinfectants and sensitivity to bacteriophages; Health monitoring medical personnel(carriage of epidemically significant strains, morbidity); Sanitary and bacteriological studies of objects environment for availability MRSA; Conducting molecular genetic monitoring, the purpose of which is to obtain data on the structure of hospital isolates, identify epidemically significant ones among them, as well as decipher the mechanisms of their circulation and spread in the hospital; Monitoring compliance with sanitary, hygienic and anti-epidemic regimes; Epidemiological analysis of morbidity and mortality from nosocomial infections, allowing us to draw conclusions about the sources, routes and factors of transmission, as well as conditions conducive to infection. The central link of epidemiological analysis should be molecular genetic monitoring. An epidemiological analysis based on its data will not only make it possible to correctly assess but also predict epidemic situations and, through early anti-epidemic measures, prevent outbreaks of nosocomial infections caused by MRSA. Organizational and methodological management of work on the prevention and control of nosocomial infections caused by MRSA , carry out structural divisions bodies and institutions carrying out state sanitary and epidemiological supervision in republics, territories, regions, districts and cities. Moscow and St. Petersburg. Federal executive authorities, including healthcare authorities, are involved in the implementation of a set of measures to prevent nosocomial infections, incl. caused by MRSA. |
. General information
In the last decade the problem nosocomial infections(HAI) has become extremely important for all countries of the world. This is due, first of all, to a significant increase in the number of hospital strains of microorganisms that are resistant to a wide range of antimicrobials. Despite the significant underestimation, in Russian Federation About 30 thousand cases of nosocomial infections are registered annually, with a minimum economic loss of more than 5 billion rubles annually. Among the causative agents of nosocomial infections, one of the first places still belongs to microorganisms of the genusStaphylococcus,the most pathogenic representative of which isS. aureus. The epidemiological situation is complicated due to the widespread spread in hospitals, as well as the appearance of clinical isolates in the community environmentS. aureus,oxacillin-resistant (ORSA or MRSA). MRSA capable of causing various clinical forms of nosocomial infections, including the most severe, such as: bacteremia, pneumonia, syndrome septic shock, septic arthritis, osteomyelitis and others, which require long-term and expensive treatment. The occurrence of complications caused by MRSA , leads to an increase in hospitalization time, mortality rates, and significant economic losses. It has been shown that the increase in the frequency of nosocomial infections observed in hospitals around the world is due to the spread of epidemic strains MRSA , many of which are capable of producing pyrogenic toxins - superantigens that suppress the immune response toS. aureus.
Since the late 90s of the last century, in Russian hospitals there has been an increase in the frequency of isolation MRSA , which in a number of hospitals reached 30 - 70%. This makes the use of many antimicrobial drugs ineffective and significantly worsens the quality of care. medical care to the population. Under these conditions, improving methods of epidemiological and microbiological monitoring aimed at identifying epidemically significant strains is becoming increasingly important.
. Characteristics of MRSA as pathogens of nosocomial infections
4.1. Taxonomy and biological features
Main epidemic strains and clones MRSA
|
The restriction results are presented in (34). Primer sets for type identification SCC mec
5.2.5.3. Identification of genes that determine the synthesis of enterotoxins A(sea), B(seb), C(sec) and toxic shock syndrome toxin (tst-H)To identify genessea, seb, secmultiplex PCR is used. The composition of the reaction mixture is standard. Primer concentration for gene detectionsea- 15 pkm/µl, seb, sec- 30 pkm/µl. To determine the gene tst - H concentration of MgCl 2 in the reaction mixture - 2.0 mM, primer concentration - 12 pkm/μl. Amplification mode No. 1 Primer sets for gene identificationsea, seb, sec
. Organization of epidemiological surveillance of nosocomial infections caused by MRSASurveillance of MRSAis an integral part of epidemiological surveillance of nosocomial infections and includes the following components: Identification, recording and recording of all cases of nosocomial infections caused by MRSAand confirmed by the results of microbiological studies; Identification of colonized patients MRSA (according to epidemic indications); Determination of the resistance spectrum of isolates MRSA to antibiotics, antiseptics, disinfectants and sensitivity to bacteriophages; Monitoring the health status of medical personnel (carriage of epidemically significant strains, morbidity); Sanitary and bacteriological studies of environmental objects for the presence MRSA; Conducting molecular genetic monitoring, the purpose of which is to obtain data on the structure of hospital isolates, identify epidemically significant ones among them, as well as decipher the mechanisms of their circulation and spread in the hospital; Monitoring compliance with sanitary, hygienic and anti-epidemic regimes; Epidemiological analysis of morbidity and mortality from nosocomial infections, allowing us to draw conclusions about the sources, routes and factors of transmission, as well as conditions conducive to infection. The central link of epidemiological analysis should be molecular genetic monitoring. An epidemiological analysis based on its data will not only make it possible to correctly assess but also predict epidemic situations and, through early anti-epidemic measures, prevent outbreaks of nosocomial infections caused by MRSA. Organizational and methodological management of work on the prevention and control of nosocomial infections caused by MRSA , are carried out by structural divisions of bodies and institutions carrying out state sanitary and epidemiological supervision in republics, territories, regions, districts and cities. Moscow and St. Petersburg. Federal executive authorities, including healthcare authorities, are involved in the implementation of a set of measures to prevent nosocomial infections, incl. caused by MRSA. |
Staphylococci are one of the most common groups of microorganisms that include saprophytes and pathogens of human and animal diseases. Despite the relative simplicity of detecting staphylococci in biological material from patients and environmental objects, numerous difficulties arise in practice. This is due to the fact that staphylococci are representatives normal microflora, therefore, staphylococcus in a smear is not always objective evidence of their etiological role in the development of the disease. It is also necessary to take into account the diversity of their manifestations, the degree of pathogenicity, and the wide variability under the influence of antibacterial agents, extreme variety of clinical forms.
That is why the diagnostic and treatment scheme for this infection cannot be universal, but must be developed taking into account the specifics of a particular nosological form of the disease. In addition, an important measure is the combined determination of qualitative and quantitative indicators of the content of pathogenic staphylococci in the test material.
Foodborne illnesses staphylococcal etiology in terms of the number of cases, they occupy one of the leading places among bacterial poisonings.
The norm of staphylococcus in a smear
Normally, staphylococcus must be present in the smear, since it is a representative of normal microflora. Its absence or low rate has the same negative impact on health as inflated indicators. It is customary to consider an indicator of up to 103 (10 in 3) as a norm. A violation is considered to be any deviation, both in the direction of increasing concentration and in the direction of decreasing it. An increase above this indicator is a pathological condition in which staphylococcus is released into the environment, even during quiet breathing.
Staphylococcus in a smear 10 in 3 - 10 in 5
Unit of measurement when carrying out quantitative analysis serves as CFU/ml - the number of colony-forming units in 1 ml of the biological material under study.
To carry out calculations and determine the degree of contamination, first count the number of homogeneous colonies that grew in a Petri dish after sowing. They must be identical in color and pigmentation. Then a recalculation is made from the number of colonies to the degree of contamination.
Let's look at specific example. For example, if 20 CFU grew in a dish, this means that 0.1 ml of the test material contained 20 colonies of microorganisms. Calculate total quantity microorganism can be done like this: 20 x 10 x 5 = 1000, or 103 (10 in 3). In this case, it is assumed that 20 is the number of colonies that grew on a Petri dish, 10 is the number of colony-forming units in 1 ml, taking into account the fact that only one tenth of the microorganisms were inoculated, 5 is the volume of physiological solution in which it was diluted try.
The concentration of 104, (10 in 4) is determined in a similar way, which many experts consider as a borderline state between relative norm and a pronounced pathology in which bacteremia and an acute inflammatory process develop. As absolute pathology the indicator considered is 105 (10 in 5).
ICD-10 code
B95.8 Unspecified staphylococci as the cause of diseases classified elsewhere
Causes of staphylococci in a smear
Staphylococcus will always be detected in a smear within normal limits, since it is a representative of normal microflora. Therefore, from the point of view of bacteriology, it makes sense to discuss the reasons for the increase in the quantitative indicators of staphylococcus. Thus, the concentration of staphylococcus increases primarily with reduced immunity. Normally, the immune system produces protective factors (histocompatibility complex, interferons, immunoglobulins, etc.) that stimulate normal condition mucous membranes, prevent the uncontrolled proliferation of bacterial flora, suppresses active growth.
Another reason is dysbiosis. In force various reasons the number of representatives of normal microflora decreases. As a result, " free space", which is immediately occupied by other microorganisms, including staphylococcus. It is one of the first microorganisms to colonize free space and securely attach to it. As a result, quantitative indicators increase sharply.
There are many causes of dysbiosis. Perhaps the most important thing is to take antibiotics, since there are practically no targeted antibiotics that specifically affect the causative agent of the disease. All of them are drugs with wide range actions. They have an effect not only on a specific pathogen, but also on the accompanying flora. Chemotherapy and antitumor treatment have a similar effect.
Hypothermia, overwork, constant nervous and mental stress, stress, and non-compliance with the daily routine contribute to a decrease in immunity and disruption of normal microflora. Inferiority and malnutrition, lack of vitamins, microelements, bad habits, unfavorable conditions residence and work.
Staphylococcus in a throat swab
A throat swab is taken when conducting preventive studies for workers in the catering and child care sectors, as well as for diagnostics infectious diseases(only if indicated). The main indication is the presence of inflammatory processes in the nasopharynx and pharynx.
The development of staphylococcal infections and food poisoning begins precisely with oral cavity and pharynx. Often the microorganism persists in the area of the pharynx, nasopharynx, and the person does not even suspect it, because early stages the pathological process may be asymptomatic. However, its amount is increasing, which may subsequently result in chronic pathology, severe inflammation, sore throat, swollen lymph nodes. In addition, with an increased concentration of the microorganism, it is released into the environment. As a result, a person becomes a bacteria carrier. In this case, the person himself may not get sick, but he infects the people around him.
If staphylococcus is detected in a throat smear, people are not allowed to work in food factories, culinary shops, or canteens, which helps avoid food intoxication. Also, bacteria carriers are not allowed to work with children, especially for early, preschool, younger age. Mandatory sanitation is carried out
Identifying the exact concentration of staphylococcus in a smear makes it possible to accurately determine the pathogen and diagnose the pathological process, and select the optimal treatment.
The material for research is collected using a sterile swab by passing it over the surface palatine tonsils. It is imperative that the material is collected on an empty stomach, or no earlier than 2-3 hours after a meal. It is imperative to collect the material before antibiotic therapy, otherwise the results will be distorted.
Then, in a laboratory setting, the test material is inoculated onto nutrient media. The material must be sown within the next 2 hours after collection. The optimal medium for inoculating staphylococcus is milk-salt agar and yolk agar.
, , , , , , , , , , ,
Staphylococcus in a nasal swab
A nasal swab is taken when examining certain categories of workers (working with children, in the field of catering). The collection is made with a sterile swab from the nasal mucosa. In this case, a separate tampon is used for each nostril. At the same time nasal cavity should not be treated with anything, washing should not be carried out the day before. The collection is made before antibiotic therapy, otherwise the result will be invalid.
The analysis takes on average 5-7 days. After collecting the material, it is inoculated directly onto the surface of the nutrient medium. For inoculation, 0.1 ml of washing is used. It is convenient to use Baird-Parker medium, on which staphylococcal colonies are very easy to recognize by their opalescent sheen and black colonies. In general, the choice of environment is determined by the laboratory assistant, depending on the laboratory's facilities and individual research goals, specialization and degree of qualification. The ratio of seed and nutrient medium is 1:10. Then incubate under thermostatic conditions.
Then, on day 2-3, reseeding is carried out on slanted agar, and a pure culture is isolated. Further studies are carried out with it (biochemical, immunological), the main properties are determined, the culture is identified, the concentration is determined, and, if necessary, sensitivity to antibiotics.
Separately, microscopy is performed, which makes it possible to determine an approximate preliminary assessment of the smear, identify it by characteristic morphological and anatomical features species affiliation of the microorganism. You can also detect other signs of pathology: signs of inflammation, neoplasm.
A person is given only finished result indicating the type of microorganism, degree of contamination, and sometimes sensitivity to antibacterial drugs.
Staphylococcus in a vaginal smear
They are detected because they are permanent inhabitants of the skin and mucous membranes. Diseases that are caused by staphylococci are of the nature of autoinfection, that is, they develop when the basic parameters of the human biochemical cycle change, hormonal levels, microflora, damage to mucous membranes, pregnancy. Less commonly, they are a consequence of exogenous penetration of infection (from the external environment).
Staphylococcus in a smear from the cervical canal
They can be detected against the background of dysbacteriosis, which develops during pregnancy, decreased microflora, and disruption of the hormonal cycle. Since staphylococcus is characterized by a wide range of sources of infection and multiple organs, they can be easily transported in the blood and cause inflammation outside the main source. Often the development of staphylococcal infection is a consequence of antibiotic therapy, physiotherapy, and surgical interventions.
Risk factors
People with a pathological focus of infection in the body are at risk. For example, a staphylococcal infection can develop in the presence of caries in the oral cavity, inflammation of the tonsils, chronic and incompletely cured diseases respiratory tract, genitourinary organs, in the presence of purulent-septic wounds, burns, damage to the skin and mucous membranes. Great danger represent catheters, implants, grafts, prostheses, since they can be colonized by staphylococcal infection.
The risk factor is reduced immunity, impaired endocrine system, dysbacteriosis, diseases gastrointestinal tract. The risk group also includes people who have recently had surgery, after serious illnesses, after antibiotic therapy, chemotherapy.
A separate group consists of people with immunodeficiencies, AIDS, other infectious diseases, and autoimmune pathologies. Newborn children (due to immature microflora and immune system) and pregnant women (due to hormonal changes) are at risk. Women in labor and postpartum women, since currently in hospitals and maternity hospitals serious danger represent nosocomial strains of staphylococcus that live in external environment, acquired multiple resistance and increased pathogenicity. They are quite easy to become infected with.
People who do not follow a daily routine, do not eat enough, and are exposed to nervous and physical stress and overexertion are at risk.
A special group is represented medical staff, biologists, researchers who work with various cultures of microorganisms, including staphylococcus, have contact with biological fluids, tissue samples, feces, are in constant contact with both infectious and non-infectious patients.
This should also include laboratory technicians, nurses, nurses, sanitary inspection officials, pharmacists, developers of vaccines and toxoids, and their testers. Employees are also at risk agriculture dealing with animals, products of livestock and poultry slaughter, which also act as a source of infection.
, , , , ,
Symptoms of staphylococci in a smear
Symptoms directly depend on the location of the source of infection. Thus, with the development of a respiratory tract infection, colonization of the mucous membrane of the oral cavity and nasopharynx first occurs. This manifests itself in the form of inflammation, swelling, hyperemia. Pain appears when swallowing, soreness, burning in the throat, nasal congestion, and a runny nose accompanied by yellow-green mucus, depending on the severity of the pathology.
As the infectious process progresses, signs of intoxication develop, the temperature rises, weakness appears, the body's overall resistance decreases, immunity decreases, as a result of which the pathological process only worsens.
Signs may develop systemic damage organs. Along the descending respiratory tract, the infection descends, causing bronchitis, pneumonia, pleurisy with severe cough, copious secretion of sputum.
When an infection develops in the area of the genitourinary tract and reproductive organs, irritation of the mucous membranes first develops, itching, burning, and hyperemia appear. Gradually, the pathological process progresses, inflammation, pain, and discharge appear. white with a specific smell. There is pain when urinating, a burning sensation. The progression of the disease leads to the development of an intense infectious process that spreads to the rectum, perineum, internal organs.
When the inflammatory process is localized on the skin and wound surface, the wound festers, a specific smell appears, local, and then local and general body temperature may increase. The source of infection is constantly spreading, the wound “gets wet”, does not heal, and grows all the time.
With the development of staphylococcal infection in the intestinal area, signs appear food poisoning: nausea, vomiting, diarrhea, indigestion, stool, loss of appetite occur. Pain and inflammation appear in the gastrointestinal tract: gastritis, enteritis, enterocolitis, proctitis. With the generalization of the inflammatory process and increasing signs of intoxication, body temperature rises, chills and fever develop.
First signs
Known early symptoms, which are harbingers of the disease. They develop as the concentration of staphylococcus in the blood increases, and appear long before real symptoms appear.
Thus, the development of staphylococcal infection is accompanied by increased heart rate and breathing, tremors in the body, chills, and fever. When walking, increased load, a load on the heart and lungs may be felt, slight shortness of breath. May appear headache, migraine, nasal and ear congestion, less often - tearing, sore and dry throat, dry skin and mucous membranes.
Feelings often appear elevated temperature, however, when measured it remains normal. A person quickly gets tired, performance decreases sharply, irritation, tearfulness, and drowsiness appear. Concentration and ability to concentrate may decrease.
, , , , , , , , , ,
Staphylococcus aureus in a smear
Staphylococcus aureus, S. aureus, is a common causative agent of inflammatory and infectious diseases of the internal organs of humans and animals. More than 100 nosoological forms of diseases caused by this pathogen are known. The pathogenesis of Staphylococcus aureus is based on a whole complex of toxic substances and aggression factors, enzymes that are produced by microorganisms. In addition, it has been established that the pathogenicity of the microorganism is due to genetic factors and environmental influences.
It is worth emphasizing that Staphylococcus aureus has multiorgan tropism, that is, it can become the causative agent of a pathological process in any organ. This manifests itself in the ability to cause purulent-inflammatory processes in the skin, subcutaneous tissue, lymph nodes, respiratory tract, urinary system, and even the musculoskeletal system. It is a common causative agent of foodborne diseases. The special significance of this microorganism is determined by its role in the etiology of nosocomial infections. Among Staphylococcus aureus, methicillin-resistant strains often arise, which are highly resistant to the action of any antibiotics and antiseptics.
It is quite easy to recognize in a smear, since it has the appearance of gram-positive cocci, the diameter of which varies from 0.5 to 1.5 microns, located in pairs, short chains or clusters in the form of a bunch of grapes. Immobile, do not form spores. Grows in the presence of 10% sodium chloride. Surface structures are capable of synthesizing a number of toxins and enzymes that play important role in the metabolism of microorganisms and determine their role in the etiology of staphylococcal infections.
It is also easy to recognize in a smear by such morphological features as the presence of a cell wall, membrane structures, capsule and flocculent factor. An important role in pathogenesis is played by aglutinogen A, a protein that is evenly distributed throughout the entire thickness of the cell wall and is connected to peptidoglycan by covalent bonds. The biological activity of this protein is diverse and is an unfavorable factor for the macroorganism. It is capable of reacting with mucous immunoglobulin, forming complexes that are accompanied by damage to platelets and the development of thromboembolic reactions. It is also an obstacle to active phagocytosis and contributes to the development of an allergic reaction.
Staphylococcus epidermidis in a smear
For a long time it was believed that Staphylococcus epidermidis was not pathogenic. But recent research has confirmed that this is not the case. Is a representative of normal microflora skin and can cause illness in some people. This is especially true for people with reduced immunity, after burns, damage to the integrity of the skin, and with various wounds. As a result of the development of staphylococcal infection, a purulent-septic inflammatory process develops quite quickly, zones of necrosis, erosion, ulcers, and suppuration appear.
It is quite easy to recognize in a smear by the formation of pigmented colonies with a diameter of up to 5 mm. They form cocci and can be single or combined into polycompounds resembling bunches of grapes. They can grow in both aerobic and anaerobic conditions.
, , , , , ,
Hemolytic staphylococcus in a smear
The hemolytic properties of staphylococcus are its ability to lyse blood. This property is ensured by the synthesis of plasmacoagulase and leukocidin - bacterial toxins that break down the blood. It is the ability to split and coagulate plasma that is the leading and constant criterion by which pathogenic staphylococci are quite easy to identify.
The principle of the reaction is that plasmacoagulase reacts with plasma Co-factor, forms coagulazothrombin with it, which converts thrombinogen into thrombin with the formation of a blood clot.
Plasmocoagulase is an enzyme that is quite easily destroyed by proteolytic enzymes, for example, trypsin, chemotrypsin, and also when heated to a temperature of 100 degrees or higher for 60 minutes. Large concentrations of coagulase lead to a decrease in the ability of blood to clot, hemodynamics are disrupted, and oxygen starvation fabrics. In addition, the enzyme promotes the formation of fibrin barriers around the microbial cell, thereby reducing the efficiency of phagocytosis.
Currently, 5 types of hemolysins are known, each of which has its own mechanism of action. Alpha toxin is not active against human erythrocytes, but lyses erythrocytes of sheep, rabbits, pigs, aggregates platelets, and has a lethal and dermonecrotic effect.
Beta toxin causes lysis of human erythrocytes and exhibits a cytotoxic effect on human fibroblasts.
Gamma toxin lyses human red blood cells. Its lytic effect on leukocytes is also known. Does not have toxic effects when administered intradermally. At intravenous administration leads to death.
Delta toxin differs from all other toxins in its thermolability, wide spectrum of cytotoxic activity, and damages red blood cells, white blood cells, lysosomes and mitochondria.
Epsilon toxin provides the widest possible area of effect, lysing all types of blood cells.
Coagulase-negative staphylococcus in a smear
The importance of coagulase-negative staphylococci in the development of pathology of internal organs is beyond doubt. Researchers believe that this group is responsible for the development of pathology of the urogenital tract in approximately 13-14% of cases. They are pathogens of skin and wound infections, conjunctivitis, inflammatory processes and sepsis in newborns. The most severe form of infection is endocarditis. The number of such complications has especially increased due to the high prevalence of heart surgeries during installation artificial valves and shunting of blood vessels.
Considering biological properties, it is advisable to note that the microorganisms are cocci with a diameter of no more than 5 microns, do not form pigments, and can grow in both aerobic and anaerobic conditions. Grows in the presence of 10% sodium chloride. Capable of hemolysis, nitrate reduction, possess urease, but do not produce DNAase. Under aerobic conditions they are capable of producing lactose, sucrose, and mannose. Not capable of fermenting mannitol and trehalose.
The most important is Staphylococcus epidermidis, which is one of the leading clinically significant pathogens. Causes septicemia, conjunctivitis, pyoderma, infections urinary tract. Also among coagulase-negative strains there are many representatives of nosocomial infections.
, , , , , ,
Staphylococcus saprophyticus, saprophytic in a smear
Refers to coagulase-negative strains that are capable of existing in both aerobic and anaerobic conditions. Actively multiply in the wound surface, in damaged areas of the skin, with severe burns, with foreign body V soft tissues, in the presence of transplants, prostheses, and invasive procedures.
Often lead to the development toxic shock. This effect is due to the action of endotoxins. Often develops when using sorbent tampons in women during menstruation, in the postpartum period, after abortions, miscarriages, gynecological operations, after long-term use barrier contraception.
The clinical picture is presented sharp increase fever, nausea, sharp pain in muscles and joints. Later, characteristic spotty rashes appear, most often generalized. Developing arterial hypotension accompanied by loss of consciousness. The mortality rate reaches 25%.
Fecal staphylococcus in smear
It is the main causative agent of foodborne diseases. Well preserved in the environment. The main route of transmission is fecal-oral. It is released into the environment with feces. Enters the body with poorly cooked food, with dirty hands, unwashed products.
The mechanism of action is due to staphylococcal enterotoxins, which are heat-stable polypeptides formed during the proliferation of enterotoxigenic strains, staphylococci in food, intestines and artificial nutrient media. They exhibit high resistance to the action of food enzymes.
The enteropathogenicity of toxins is determined by their connection with the epithelial cells of the stomach and intestines and their effect on the enzymatic systems of epithelial cells. This, in turn, leads to an increase in the rate of formation of prostaglandins, histamine, and an increase in the secretion of fluids into the lumen of the stomach and intestines. In addition, toxins damage membranes epithelial cells, increasing the permeability of the intestinal wall to other toxic products of bacterial origin.
Virulence of fecal enteropathogenic staphylococci is regulated by the genetic apparatus bacterial cell in response to environmental factors, which allows the microorganism to quickly adapt to environmental conditions, which allows the microorganism to quickly adapt to changing conditions when moving from one microbiocenosis to another.
Differential diagnosis
When determining the role and significance of various representatives of the genus Staphylococcus in the etiology of human purulent-inflammatory diseases, despite their relative simplicity, their detection is associated with numerous difficulties. This is due to the fact that staphylococcus is a representative of normal microflora that inhabits various biotopes human body. It is necessary to clearly distinguish between endogenous staphylococcus, which develops inside the body, and endogenous, which penetrates the body and from the environment. It is also important to understand which biotopes human body is typical for it, and where it is a representative of the transient flora (introduced by chance).
It is also important to take into account the high variability of the microorganism under the influence various factors, including antibiotics. Taken into account great variety clinical manifestations and nosological forms. Therefore, there is a universal diagnostic scheme for staphylococcal infection. It's easier to explore those biological media, which are normally sterile (blood, urine, cerebrospinal fluid). IN in this case detection of any microorganism or colony is a pathology. The most difficult is the diagnosis of diseases of the nose, pharynx, intestines, and testing for bacterial carriage.
In the very general view The diagnostic scheme can be reduced to the correct collection of biological material and its bacteriological primary seeding on an artificial nutrient medium. At this stage, preliminary microscopy can be performed. By studying the morphological and cytological features of the sample, it is possible to obtain certain information about the microorganism and, at a minimum, carry out its generic identification.
To get more detailed information it is necessary to isolate a pure culture and conduct further biochemical, serological and immunological studies with it. This allows you to determine not only the generic, but also the species, as well as determine the biological identity, in particular, serotype, biotype, phagotype and other properties.
, , [
In some mild cases, antibiotic therapy may not be necessary to correct the condition. It may just be necessary to normalize the microflora. This is observed with dysbacteriosis. In this case, probiotics and prebiotics are prescribed, which normalize the state of microflora by reducing the amount pathogenic flora and increasing the concentration of representatives of normal microflora.
Symptomatic therapy is rarely used, since it is usually sufficient to eliminate the infection, and associated symptoms will disappear on their own. In some cases, additional measures are prescribed, for example: painkillers, anti-inflammatory, antihistamines, antiallergic drugs. At skin diseases external agents are used: ointments, creams. Physiotherapy, folk and homeopathic remedies may be prescribed.
Vitamin therapy is not carried out, since vitamins act as growth factors for microorganisms. The exception is vitamin C, which must be taken at a dosage of 1000 mg/day (double dose). This will increase immunity, resistance, and resistance of the body to adverse factors.
Medicines
The treatment of infectious diseases must be taken seriously. Self-medication should not be practiced; it often has disastrous consequences. There are many nuances to consider before starting treatment. Only a doctor can do this best.
It is important to take precautions: do not treat the infection “blindly”, even with a pronounced clinical picture. It is necessary to carry out bacteriological examination, isolate the causative agent of the disease, select the most optimal antibiotic directly for it, determine the required dosage that will completely suppress the growth of the microorganism.
It is also important to go through full course even if the symptoms have disappeared. This is because if you stop treatment, the microorganisms will not be completely killed. Surviving microorganisms will quickly acquire resistance to the drug. At reuse it will be ineffective. Moreover, resistance to the entire group of drugs will develop, and to similar drugs(due to the development of cross-reaction).
Another important precaution is that you should not reduce or increase the dosage on your own. The reduction may not be effective enough: the bacteria will not be killed. Accordingly, they are short terms mutate, acquire resistance and more high degree pathogenicity.
Some antibiotics may also have side effect. The stomach and intestines are especially sensitive to antibiotics. Gastritis, dyspeptic disorders, stool disorders, and nausea may develop. Some have a negative effect on the liver, so they need to be taken together with hepatoprotectors.
Below are antibiotics that have worked well in treating staph infections with minimal side effects.
Amoxiclav is effective in the treatment of staphylococcal infections of any location. It is used in the treatment of respiratory diseases, genitourinary system, intestines. Take 500 mg per day for three days. If necessary, the course of treatment is repeated.
Ampicillin is prescribed mainly for diseases of the upper and lower respiratory tract. The optimal dosage is 50 mg/kg body weight.
Oxacillin is effective both for local inflammatory processes, and with generalized infection. It is a reliable prevention of sepsis. Prescribed 2 grams every 4 hours. Administered intravenously.
For purulent-inflammatory skin diseases, chloramphenicol ointment is used externally, applying it in a thin layer to the damaged surface. Also, chloramphenicol is taken orally, 1 gram three times a day. With severe generalization of the infectious process, chloramphenicol is administered intramuscularly, 1 gram every 4-6 hours.
Suppositories for Staphylococcus aureus
Used mainly for gynecological diseases, infections of the genitourinary tract, less often – with intestinal dysbiosis with inflammation of the rectum. Prescribe and select candles optimal dosage only a doctor can, because misuse there is a high risk of complications and further spread of infection. Suppositories are not prescribed without preliminary tests. The indication for their use is exclusively staphylococcus in the smear.
]Important to know!
Hospitalization is mandatory for patients with severe and moderate forms of the disease, including patients who cannot be isolated and proper care at home. The regimen depends on the clinical form of the disease. No diet required.
