Methicillin-resistant staphylococcus. Antibiotic resistance

Author:
Nikolaeva Lyubov Viktorovna, veterinarian of the dermatological department of the Bely Klyk clinic, Moscow.

Treatment regimens for common skin infections are widely published in the press and have been successfully used in veterinary practice. Treatments are readily available and there is a wide choice. There is much less data on resistant infections, as well as fewer drugs and regimens to treat them. In cases of common infections, empirical treatment is often used, based on knowledge of the natural susceptibility of the most common pathogens. For resistant infections, culture data must be taken into account; the treatment approach may be different. This article will discuss the main mechanisms of resistance for staphylococci for some antibiotics, recommendations for the prevention of resistance. More often Staphylococcus pseudintermedius is cultured from the skin of small domestic animals (so far laboratories indicate it as St. intermedius) than Staphylococcus aureus. These species usually have predictable sensitivity to β-lactam antibiotics, such as first and third generation cephalosporins, and to amoxicillin in combination with clavulanic acid. Since many staphylococci have the ability to use the β-lactamase enzyme to act on the β-lactam ring of the above antibiotics, it is necessary to use inhibitors of this enzyme, for example clavulanic acid or sulbactam, together with some of them. Cephalosporins are more resistant to β-lactamase, so inhibitors are usually not added to them, unlike amoxicillin, which is rarely effective without clavulanic acid. Oxacillin is also a β-lactam antibiotic, but is almost never used in practice. Most staphylococci are also sensitive to fluoroquinolones, lincosamides (clindamycin, lincomycin), erythromycin, trimethoprim-sulfonamides. According to some data, resistance to these groups was detected in 25% of cases.

Etiology and epidemiology

Staphylococcus haemolyticus on blood agar

Hemolytic staphylococcus is a gram-positive, non-motile coccus, located randomly or in clusters in the smear. It is a facultative anaerobe: it can exist without access to air. It does not form spores and grows on nutrient media containing blood. Typically, microbiology laboratories use blood agar to determine the main property of the microbe - the ability to cause hemolysis of red blood cells. The bacteria are resistant to freezing, heat, sunlight and some chemicals. The optimal temperature for the life of staphylococcus is 30-37°C. The microbe quickly adapts to the effects of antibiotics and antiseptics.

Staphylococcus haemolyticus uses endotoxin, enzymes and hemolysins as pathogenicity factors, due to which the development of purulent sore throat, pharyngitis, bronchitis, pneumonia and other inflammatory diseases of internal organs occurs. Under the influence of staphylococcal toxin, metabolism at the cellular level is disrupted, the general condition of patients worsens, and neurological symptoms appear.

Hemolytic staphylococcus is widespread in nature. Most of the inhabitants of our planet are bacteria carriers. It is considered a normal inhabitant of the human body and does not pose any danger to persons with strong immunity. Individuals with an active immune system are reliably protected. The process of staphylococcus reproduction and acquisition of pathogenic properties is suppressed by the normal microflora of the macroorganism. With a decrease in general resistance and a weakening of protective forces, the microbe causes various diseases. Pathogenic strains can enter the body from the outside as a result of contact with a bacteria carrier.

Factors that increase the pathological activity of the microbe:

• Unsanitary conditions,
• Overpopulation,
• Unhealthy food,
• Chronic stress
• Physical inactivity,
• Hypovitaminosis,
• Existing chronic diseases
• Violation of hygiene standards and rules,
• Dysbacteriosis,
• Weak immunity,
• Uncontrolled use of antibacterial drugs.

Staphylococcus haemolyticus causes purulent inflammatory diseases of the respiratory system, which are difficult to treat. It is detected during bacteriological examination of the throat discharge in patients with tonsillitis in 70% of cases. In chronic tonsillitis, hemolytic staphylococcus is cultured in approximately 50% of those examined. Bacteria are super-resistant. They remain in the tonsils and nasopharynx in an inactive state even after a course of antimicrobial therapy and are transmitted to susceptible people.

Mechanisms and ways of spreading hemolytic staphylococcus:

1. An aerosol mechanism realized by airborne droplets - as a result of communication with a sick person, especially when he often coughs and sneezes;
2. Contact mechanism, realized through contact and everyday life - through dirty hands, infected household and household items;
3. The fecal-oral mechanism, realized through the nutritional route - when consuming low-quality food products;
4. Blood contact route - when using non-sterile medical instruments,
5. The vertical path is during childbirth from mother to child.

The risk group for infection with hemolytic staphylococcus includes:

• Children,
• Aged people,
• Pregnant women,
• Persons with weakened immune systems,
• The lower strata of the population.

Microbes penetrate the human body and colonize the epithelium of the respiratory tract, but do not exhibit their pathogenic activity due to the full functioning of the immune system. Hemolytic staphylococcus in this state does not cause harm to health and is not detected in laboratory tests. Sometimes a minimum amount of bacteria is found that is safe for humans. When the immune defense weakens, the microbe becomes active, multiplies quickly and spreads throughout the body. When bacteria enter the blood, they exhibit their main pathogenic effect - they destroy red blood cells.

What is staphylococcus

Staphylococcus is a non-motile anaerobic bacterium that is conditionally pathogenic (that is, it causes harm to the body only under certain conditions). These microorganisms do not form spores and do not have a protective capsule.

They come in different sizes and colors, depending on the species. They are arranged in groups similar to a bunch of grapes. They are transmitted primarily through the air and almost always live on human skin, mucous membranes of the mouth, nose and throat.

Staphylococci produce various poisons, which, if they enter the human body, can cause an inflammatory process. If the immune system is weakened, then all body systems may be disrupted. First of all, these cocci affect the skin and respiratory organs, causing tissue necrosis. They poison the body, which can lead to toxic shock.

Different types of these parasites have different effects on human health. They are usually resistant to antibiotics and harsh weather conditions. Most often, children and the elderly suffer from these microorganisms.

Symptoms

Hemolytic staphylococcus is the causative agent of various respiratory diseases - sore throat, pharyngitis, pneumonia; urogenital tract - urethritis and prostatitis in men, cystitis or cervicitis in women; skin - impetigo, erysipelas; septic processes - endocarditis, abscesses, sepsis.

The incubation period for this infection lasts on average two days. First, patients' general condition worsens, and then catarrhal symptoms appear.

1. General symptoms of intoxication and asthenia during staphylococcal infection include: weakness, malaise, fever, nausea, flatulence, body aches, chills, poor health, lethargy, weakness, decreased appetite, cephalalgia, sleep disturbance.
2. When the respiratory system is affected, characteristic symptoms appear: mucopurulent secretion is released from the nose, the throat is sore, the mucous membrane turns red, the tonsils swell and become covered with purulent plaque, pain occurs, coughing with purulent sputum, sneezing. In children, tonsillitis caused by hemolytic streptococcus is often complicated by otitis media, lymphadenitis, and scarlet fever.
3. Inflammation of the genitourinary system in men caused by hemolytic staphylococcus is manifested by frequent urination with cutting pain and itching, the appearance of blood in the urine and other pathological impurities, discomfort in the perineum, purulent discharge from the urethra, and erectile dysfunction. In men, the microbe often causes inflammation of the prostate gland. It penetrates into the prostate secretion by hematogenous route from infected internal organs, by contact as a result of sexual intercourse, during invasive medical procedures, and in case of non-compliance with personal hygiene rules.
4. Symptoms of damage to the genital organs by hemolytic staphylococcus in women: discharge with an unpleasant odor, itching, a feeling of dryness in the vagina, pain during intercourse, burning in the genital tract, worsening at night, increased irritability of the mucous membrane.
5. Pustules or boils appear on the skin of patients , and abscesses form in the soft tissues.

Hemolytic staphylococcus is very dangerous for pregnant women. During pregnancy, the female body is vulnerable to various bacteria.
The microbe can settle in carious teeth, tonsil lacunae, and sinuses. That is why it is important to promptly sanitize existing foci of infection in the body. Staphylococcus haemolyticus during pregnancy can cause sepsis of the mother and child, which often ends in the death of both. The microbe is especially dangerous for newborns.
Infection occurs when a baby passes through the birth canal. The most severe manifestation of infection is pneumonia. Babies have a hard time suffering from the disease. Serious disturbances in vital processes often develop, and signs of respiratory failure increase. Pneumonia in newborns caused by hemolytic staphylococcus is accompanied by meningitis, neuralgia, and general intoxication.

ethnoscience

Traditional recipes for maintaining immunity
Traditional medicine is powerless in the fight against staphylococcal infection. All drugs prepared according to ancient recipes are considered auxiliary agents. Their use is aimed at strengthening the immune system and removing toxins from the body.

Women who have become victims of staphylococcal infection are recommended to use decoctions of medicinal herbs, consisting of: plantain, licorice root, thyme and string. But propolis tincture, which you can prepare yourself or buy ready-made at a pharmacy, has a special effect. Norm and rules of admission: 1 tsp. alcohol tincture in half a glass of water, three times a day.

Diagnostics

Diagnosis of diseases caused by hemolytic staphylococcus involves conducting a microbiological examination of biomaterial obtained from the patient. It is delivered to the laboratory within 2 hours from the moment of collection, immediately inoculated on nutrient media and incubated in a thermostat. After microscopy of the grown colonies and the accumulation of a pure culture, the final identification of the isolated microbe is carried out.

Bacteriological examination of biomaterial is carried out with the aim of isolating the causative agent of the pathology and determining its sensitivity to antibiotics. The material for the study is nasopharyngeal discharge, urine, smear from purulent skin formations, breast milk, vaginal secretion, feces, urethral discharge, prostate secretion. Inoculation is carried out on blood agar prepared from ordinary nutrient agar with the addition of defibrinated blood of a sheep, horse or cattle. The dishes are incubated in a thermostat for 24 hours, and then the nature of the grown colonies is described. They have a white or cream color and a pronounced zone of hemolysis along the periphery. Microscopy of Gram-stained smears is performed. Morphological and tinctorial properties are studied and additional tests are performed. In order to determine the massiveness of contamination, a quantitative analysis is carried out. The number of characteristic colonies on a Petri dish is counted and the value of colony-forming units is determined.

Normally, in a healthy person, the number of Staphylococcus haemolyticus should be no more than 103 CFU. If the indicators exceed 106 degrees, this indicates a high intensity of infection.

Additionally, all patients are prescribed to donate blood and urine for a general clinical analysis to identify signs of inflammation and organ damage. A general blood test reveals leukocytosis, neutrophilia, elevated ESR, and a urine test reveals proteinuria, leukocyturia, and bacteriuria. Phagotyping of staphylococcus - determining its sensitivity to phage viruses in order to prescribe appropriate treatment. PCR diagnostics allows you to determine the causative agent of the disease by DNA.

Treatment

Treatment of hemolytic staphylococcus is complex, long-term, etiotropic, and antimicrobial. Patients are advised to take antibiotics, immunomodulators, and desensitizing agents. Physiotherapy and local use of antiseptics and bacteriophages have a good effect.

Patients are treated by specialists of various profiles - dermatologists, ENT specialists, therapists, gynecologists, urologists, pediatricians and infectious disease specialists.

• Antibacterial drugs are prescribed after a special test for the sensitivity of the isolated microorganism to antimicrobial agents. Hemolytic staphylococcus has increased resistance to some antibiotics. The most commonly used penicillins are Amoxicillin, Augmentin, cephalosporins Cephalotin, Ceftriaxone, macrolides Azithromycin, Clarithromycin, as well as Vancomycin and Oxacillin. Antibiotic treatment begins when the number of colony-forming units of staphylococcus exceeds 10 to the power of 4. Antibiotic therapy usually lasts 10-14 days.
• If treatment with antibiotics does not produce positive results, a staphylococcal bacteriophage or toxoid is used. These drugs are especially effective for treating inflammation in the gastrointestinal tract and genitourinary system. The bacteriophage settles in the body and begins to feed on staphylococcus. In case of damage to the upper respiratory tract, gauze turundas soaked in bacteriophage are introduced into the nasal passages, and in case of damage to the intestines, enemas with this agent are used. A liquid solution of the bacteriophage in its pure form is injected into the urinary tract through a special catheter for urethritis or cystitis. In men, infection of the external genitalia is treated with lotions. Purulent sore throat is treated by irrigating the oral cavity with a bacteriophage. For otitis media, the solution is instilled into the patient's ear. To treat furunculosis, oral administration of the drug is prescribed in combination with bacteriophage injections.
• Immunomodulatory therapy is widely used in the complex treatment of hemolytic staphylococcus. Patients are prescribed "Likopid", "Imunorix", "Ismigen".
• Antihistamines relieve swelling and eliminate itching - Suprastin, Tavegil, Zyrtek.
• To normalize body temperature, antipyretics are used - “Ibuklin”, “Nurofen”, to relieve headaches - “Pentalgin”, “Analgin”. Symptomatic therapy is often supplemented with antispasmodics, bronchodilators, and mucolytics.
• In severe cases, detoxification methods are indicated - intravenous administration of saline and colloid solutions, oral use of Regidron.
• Local treatment consists of treating the nose with antiseptics “Furacilin”, “Chlorhexidine”, “Chlorophyllipt”, irrigating the throat with antimicrobial sprays, sucking lozenges and lozenges “Strepsils”, “Septolete”, “Doctor Mom”.
• A course of taking mineral and vitamin complexes improves the general condition of patients and helps them recover faster from illness.
• Physiotherapeutic procedures are prescribed after acute signs of inflammation have been relieved. The most effective are: ultraviolet irradiation, UHF, ultrasound, magnetic therapy, laser irradiation, hardware washing of the tonsils.
• Traditional medicine: alcohol and oil solutions of chlorophyllipt for gargling a sore throat; eating black currant berries to strengthen the immune system; infusion of burdock leaves for oral administration; applying apricot pulp to skin affected by staphylococcus; taking baths with apple cider vinegar; propolis tincture for gargling; aloe and echinacea extracts are powerful natural antibiotics and strong immunostimulants.

Complications of diseases caused by hemolytic staphylococcus develop in the absence of timely and complete therapy. These include sepsis, rheumatism, heart and kidney pathologies.

Risk factors for acquiring resistant infections

Currently, there are two ways of acquiring MRSA in humans: hospital-acquired infections (“hospital-associated”, HA-MRSA) and community-acquired (“community-associated”, CA-MRSA). These infections belong to different strains, have different molecular markers and types of the mec gene. Table 1 shows comparative data isolated from people in the United States.

Table 1

Small pets are more likely to develop MRSP because the microbe is more common on animal skin. Most often, this infection was detected in postoperative wounds and pyoderma, less often in otitis media, urinary tract infections and arthritis. There have been several reported cases of infections in humans associated with animal-derived MRSP. Elderly people and children, as well as people with various immunodeficiency conditions (HIV, chemotherapy, immunosuppressive treatment, etc.) may be especially susceptible. Measures to prevent the spread of resistant infections Even without signs of infection, an animal or person can be a carrier of a resistant strain, thus presenting a danger to others. If an infection occurs with this strain, treatment may be difficult due to drug resistance. If a resistant strain is detected in an animal, measures similar to those for other infectious diseases are taken. Hygiene is observed by the owners and, of course, by the staff of the clinic observing the patient. Hand sanitizers, disposable gloves, disposable towels are used, the room is treated with disinfectant solutions, the surfaces of examination tables or stationary cages are flambéed if possible. In the case of MRSA, owners are advised to test for carriage of the strain by taking a culture from a medical laboratory. The main places of carriage of staphylococci in humans are the nostrils, in dogs - the nostrils, pharynx and anus. Clinics recommend periodically taking swabs from surfaces for bacterial culture in order to monitor the emergence of resistant infections and the quality of disinfection. Particular attention is paid to decolonization, i.e. eliminating the carriage of a resistant strain. Antiseptics are intensively used - shampoos with 4% chlorhexidine for dogs, nasal ointments with mupirocin for dogs and people, although, of course, complete decolonization is not always possible to achieve. To prevent the emergence of resistant infections, guidelines have been created, mainly aimed at limiting the use of antibiotics.

One of the most popular guidelines was developed by the British Veterinary Association (www.bva.co.uk) and includes 8 points:

1. work with the client to avoid the use of antimicrobial agents (implementation of preventive programs, disease control, isolation of infected animals); 2. avoid the use of antibiotics in inappropriate cases (uncomplicated viral infections, monitoring the correct use of drugs by owners), underdosing; 3. choose the correct drug (identification of the microbe and prediction of its sensitivity, implementation of protocols in practice for the treatment of common infections, knowledge of the mechanisms of action and pharmacodynamics of antibiotics, use of antibiotics with the narrowest spectrum); 4. monitor antimicrobial sensitivity; 5. minimize the prophylactic use of antibiotics; 6. minimize preoperative use of antibiotics; 7. record and explain deviations from protocols; 8. report suspected treatment failure (possibly the first case of resistance).

Emerging difficulties in treating resistant infections make this problem the object of special attention throughout the world in both medicine and veterinary medicine. Resistant strains can be transmitted from humans to animals and vice versa. Bacteria are capable of exchanging genetic information with other strains and even with other types of bacteria, including genes that carry mutations. Bacterial resistance, which is increasingly occurring in small animals, needs to be taken seriously, and the prescription and use of antibiotics plays a significant role in this.

Literature:

1. Scott DW, Miller WH, Griffin CE Small Animal Dermatology, 6th edition, Philadelphia, WB Saunders Company, 2001;
2. Papich M. Strategies to manage antibiotic-resistant infections. Proceedings book, 23rd Annual Congress of the ESVD-ECVD on Veterinary Dermatology. 17-19 September 2009, Bled, Slovenia;
3. Federation of Veterinarians of Europe, Antibiotic Resistance & Prudent use of Antibiotics in Veterinary Medicine, 2009;
4. Lloyd DH MRSA in dogs and cats. Proceedings book, 25th Annual Congress of the ESVD-ECVD on Veterinary Dermatology. 8-10 September 2011, Brussels, Belgium;
5. Lloyd DH MRSP in dogs. Proceedings book, 25th Annual Congress of the ESVD-ECVD on Veterinary Dermatology. 8-10 September 2011, Brussels, Belgium;
6. 6. Kadlec K. Antimicrobial resistance of Staphylococcus pseudintermedius. Veterinary dermatology, Vol 23, N 4, 2012;
7. Scott Weese J. Staphylococcal control in the veterinary hospital. Veterinary dermatology, Vol 23, N 4, 2012;8. Papich M. Selection of antibiotics for methicillin-resistant Staphylococcus pseudintermedius: time to revisit some new drugs? Veterinary dermatology, Vol 23, N 4, 2012.

Prevention

Preventive measures to prevent infection with hemolytic staphylococcus and block its reproduction in the body:

1. Maintaining personal hygiene rules
2. Sanitation of foci of chronic infection - treatment of caries, tonsillitis, otitis media, sinusitis,
3. Strengthening the immune system - hardening, walking in the fresh air, proper nutrition, physical training, good sleep,
4. Preventive intake of vitamins and microelements,
5. Regular wet cleaning of the premises and frequent ventilation,
6. Use antibiotics only as prescribed by a doctor,
7. Prevention of stress and emotional overstrain,
8. Compliance with sanitary standards and hygiene rules in health care facilities,
9. Timely identification and isolation of patients,
10. Proper care of newborns.

Hemolytic staphylococcus is a bacterium that lives in various loci of the body of a healthy person. Microbes under normal conditions do not cause harm and are not dangerous. Under the influence of negative exogenous or endogenous factors, the immune system ceases to function normally and fully protect the body. Staphylococcus haemolyticus is activated and causes the development of the pathological process.

Preparations for staphylococcus

Complex immunoglobulin preparation

It is essentially dried protein from a donor's blood. Helps launch the body's defenses. Affects all types of staphylococci.

Antistaphylococcal immunoglobulin

The powdered substance, made from blood protein, is aimed at combating only the alpha exotoxin of staphylococcus. Has a short-term effect. The effect stops after the end of the course of treatment.

Anatoxin

Purified staphylococcal toxin. Injections help develop immunity not only against bacteria, but also against its poisons.

Bacterial lysates

Crushed staphylococcus bacteria. Once in the body, they cannot harm it, but they cause a reaction from the immune system. Can be used as a vaccine.

Baneocin, fucidin and other antibiotic-based ointments

Suitable for treating inflammation on the skin. Some ointments can be applied directly to the mucous membranes.