Veterynarna biotehnologija – Veterinary biotechnology, 2016, 28, 42-54 [in Ukrainian].
State Research Institute of Laboratory Diagnostics and Veterinary and Sanitary Expertise
Zaporizhzhya Regional State Laboratory of Veterinary Medicine
MECHANISM OF RESISTANCE METHODS OF DETECTION METHICILLIN-RESISTANT STAPHYLOCOCCUS (MRSA) (REVIEW)
Introduction. Staphylococcus aureus is the first among microorganisms which resistance to earlier smoothly acting antibacterials has been discovered. Since that time, the history of penicillinase research as the first among ß-lactamases has begun.
The goal of the work was to study the mechanism of resistance for methicillin-resistant staphylococci, to make a comparative analysis for existing methods of their detection, and to prove the optimal method for usage in microbiological laboratories of Ukraine.
Materials and methods. The material for the study was published data, reference laboratories data, research conferences reports of Health Ministry of Ukraine, the State Sanitary and Epidemiological Service of Ukraine, National Academy of Medical Sciences of Ukraine, as well as the World Health Organization (WHO) data.
Results of research and discussion. Antibiotic resistance of major infectious diseases’ pathogens is one of the most serious problems of modern medicine. The speed for emerging and spreading of microorganisms’ resistance to antibiotics is impressive. MRSA often is a causative agent for nosocomial infections (HA-MRSA-health care associated MRSA), which have become resistant to the most common antibiotics, and this seriously complicates treatment. More often a set of associated MRSA strains are found in people who haven’t been hospitalized and even in healthy children (CA-MRSA-community associated MRSA). A few years ago strains of MRSA (LA-MRSA-live stock associated MRSA) appeared in the the center of attention. For instance, MRSA SS398 clonal complex, most common in pigs, is of particular concern, as its asymptomatic carrier is also common among people who work with infected animals There have been outbreaks in horses, dogs and cats, mostly CA-MRSA, which may contribute to people, domestic animals and the environment contamination. Food of animal origin can often be contaminated by MRSA, resulting in creating the main way of transmission from farm animals to humans. Fruits and vegetables contaminated with feces of infected animals or polluted water can also be transfer factors. Today there are five research methods to determine microorganisms sensitivity to antibiotics. They are: - serial dilutions in broth and agar method; - disc diffusion method; - E-test; - automatic systems (complexes) for detection microorganisms and their sensitivity to antimicrobial agents; - molecular genetic method. Among the standardized methods for determining the microorganisms sensitivity to antibiotics there are serial dilutions and diffusion methods. In addition, automatic methods are becoming widespread. Diffusion methods, other than the above mentioned, also include the imposing of discs or E-test strips on solid growth medium. Also automated microbiological analyzers are used (VITEK2, MA120 Render, Autobac MS- 2,Cobas Micro, Quantum 2, Sceptor, etc.) to determine the microorganisms sensitivity. When these automated systems are used the results are obtained within 3–10 hours. One of the advantages of these automated systems is that they allow to get results simultaneously for about 18–20 antibiotics. These methods are widely used in microbiology laboratories, they correlate well with other methods. Molecular genetic method differs from all the others. It has very high precision because the polymerase chain reaction (PCR) can detect the presence of resistance in certain species and even strains in its genetic apparatus (circular DNA or plazmids). The strains of staphylococci resistant to oxacillin are considered to be resistant to all β-lactam antibacterials. If you receive questionable results, you should use additional methods such as molecular genetic one.
Conclusions and prospects for further research: 1. At present MRSA is considered to be one of the leading nosocomial pathogens; 2. MRSA strains can be identified both by classic microbiological methods and modern research methods: PCR, automated systems VITEK2, MA120 Render, Autobac MS-2, Cobas Micro, Quantum 2, Sceptor, etc. 3. Microbiological methods play an important role, as they are simple to apply, highly sensitive, widespread in use, affordable and do not require monitoring for the use of expensive instrumentation and test systems. Readily available consumables, equipment commom for any microbiological laboratory are used for work. 4. The easiest method of microbiological research remains disc diffusion method that can be used as a screening method, since it is sufficiently objective, based on the use of discs with antibiotics with known concentration. 5. When identified as methicillin resistant, the strain is considered to be resistant to all β-lactam antibiotics. It is necessary to use drugs of other groups for treatment, in this case the choice is glycopeptides.
Keywords: antibiotics, methicillin, oxacillin, resistance, staphylococcus, laboratory tests, mechanism of resistance.