A method of evaluating the sensitivity of microorganisms to antimicrobial agents in the disk

 

(57) Abstract:

The invention relates to the field of medicine. The method is characterized by the fact that carry out sowing of the test culture in a nutrient medium, put it drives with antimicrobial drugs, measure the diameter of the zones of growth inhibition (JSR) microorganisms, measurement is conducted with the help of the device in the form of transparencies with 32 laps, with the difference between diameters of 1 mm and the definition JSR carried out by matching with the diameter of the fixture, with an assessment of the sensitivity of microorganisms is determined by the ratio of the sensitivity of the microorganism (KCHM), calculating it according to the formula

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when the value KCHM = 1 or more microorganisms belong to the group of sensitive, when the value KCHM less than 1 - to moderately-sensitive and-insensitive. The method allows to quantify the sensitivity of microorganisms to any antimicrobial agent, to compare KCHM to two or more drugs with the aim of selecting the most appropriate one for a specific patient, to control the sensitivity of a microorganism to the drug in the dynamics and, if necessary, to conduct timely replacement more effective. The method allows the

The present invention relates to the field of medicine, namely, medical Microbiology, and can be used to determine the sensitivity of the microorganisms isolated from patients and from the objects of the hospital environment, to antimicrobial agents.

The analogue of the present invention is a method of serial dilutions in liquid and solid mediums that give a quantitative measure of the sensitivity of microorganisms and to determine the minimum inhibitory concentration of antimicrobial drug ("Medical Microbiology" Ed. by Pokrovsky Century. And., Pozdeeva O. K. M., 1998, S. 162-163). However, this method is laborious, time-consuming, and therefore its use in the practice of the bacteriological laboratories of medical institutions is limited.

The prototype of the present invention is the method of standard drives, based on the diffusion of antimicrobial agents in agar (instructions for use disks for determination of sensitivity to antibiotics. M, 1986).

The method is simple, convenient, does not require much time and material costs. The sensitivity of microorganisms to antimicrobial agents in the and in the instructions, various JSR, depending on the magnitude of which microorganisms sensitivity are divided into 3 groups: resistant, moderately resistant and susceptible. To include sustainable strains of microorganisms whose growth is not inhibited by the drug at concentrations that are created in the body when using the maximum permissible doses. Moderately resistant relate strains to inhibit the growth of which require concentration created in the serum with the introduction of the maximum doses of the drug. To are sensitive strains whose growth is inhibited at concentrations of the drug detected in the blood serum of a patient using conventional doses of antibiotic. For a group of sensitive microorganisms" are only minimum values JSR. In practice, however, JSR can vary widely and, therefore, in this group it is impossible to identify the most sensitive microorganisms to a particular drug that can cause irrational of his choice and to degrade the effectiveness of patient treatment and the lengthening of the period of treatment.

JSR microorganisms are determined by the ruler in mm, While the results are not always accurate. Errors can birosca not always have the shape of a circle, and the determination can be performed either by the smallest and largest size. In addition, even if the zone of growth inhibition is circular, then measuring the diameter range may not overlap on the diameter of the zone.

Thus, although the method and has gained recognition and is used in almost all bacteriological laboratories of medical institutions, its major drawback is that with its help we can obtain only a qualitative description of the sensitivity of microorganisms.

The aim of the invention is to improve the accuracy and providing a quantitative assessment of the sensitivity of microorganisms to antimicrobial agents in the disk.

This goal is achieved by the fact that defined as in the beginning, when necessary in the treatment process, the criterion of sensitivity of microorganisms (KCHM) calculated by the formula:

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when the value KCHM = 1 or more microorganisms belong to the group of sensitive, when the value KCHM less than 1 - to moderately-sensitive and-insensitive.

A method of evaluating the sensitivity of microorganisms to antimicrobial agents in the disk is as Abram 100 mm, put the disks containing the antimicrobial agents of industrial production. After incubation in a thermostat for 18-20 hours at 35-37oC spend the definition JSR our proposed device. For this device, including 32 of the circle located on the transparent film, the diameters specified in the heart, respectively, from 9 to 40 mm, which differ from each other by 1 mm (see drawing), is applied to the outer surface of the bottom of the Petri dishes and moved to align one of the circles defined by the zone of growth inhibition of microorganism drive around with a drug. The figure in the center of the circle coinciding with the designated area, and is its diameter. In the case where the area of stunting has the shape of a circle, on the device selected in the circle in which the designated area fits their largest size. Received JSR microorganism to a specific antimicrobial agent, and the corresponding value KCHM find in our proposed table ' Criterion of sensitivity of microorganisms to antimicrobial agents in the disk, depending on the diameters of zones of growth inhibition of microorganisms developed for practical use KCHM and facilitate the work of staff bacteriological respectively moderately sensitive and sensitive microorganisms (indicated above the line) and the corresponding criteria of the sensitivity of microorganisms (indicated below the line). Whichever KCHM selects the optimal antimicrobial drug.

Example. Patient W., 32 years, operated 12.01.99, about gangrenous-perforating appendicitis with diffuse purulent peritonitis. On the 4th day after the operation, General condition, temperature up to 39oidentified festering wound. JSR St.aureus isolated from a patient from a wound, drive around with gentamicin on the environment AGV, measured using the proposed device, 24 mm Corresponding to the diameter KCHM on the table equal to 1.5. This microorganism belongs to the group of sensitive. JSR drive around with erythromycin 24 mm Corresponding to the diameter KCHM table a 1.1. This microorganism belongs to the group sensitive. Therefore, the selected aureus sensitive to gentamycin, and erythromycin; however, sensitivity to gentamicin above. Therefore, the patient was recommended gentamicin. 7 days after treatment, General condition of the patient improved, the temperature decreased to 37.2oremained scant purulent discharge from the wound. Re bacteriological analysis showed that JSR St.aureus drive around with gentamicin 16 mm KCHM = 1, the microorganism of Taka decreased. Replacement of gentamicin on another antibiotic with higher KCHM (Cefotaxime, KCHM= 1,4). As a result of antibiotic therapy with this drug, the patient's condition was satisfactory, the pus from the wound stopped, postoperative wound healed. The patient was discharged 19 days after surgery. Thus, this method allows comparison of the sensitivity of the microorganism to multiple drugs, as well as a comparison of the sensitivity of the microorganism to one drug in the treatment process.

The proposed criterion of sensitivity of microorganisms allows you to give a quantitative description of the sensitivity of microorganisms to any antimicrobial agent, to compare KCHM to two or more drugs with the aim of selecting the most appropriate one for a specific patient, to control the sensitivity of a microorganism to the drug in the dynamics and, if necessary, to conduct its timely replacement by a more efficient, which will reduce the number of postoperative complications, mortality from hospital-acquired infections, to reduce the duration of patients ' stay in hospital, and therefore reduce the cost of treatment.

The proposed device is, the quick and accurately obtain the result. The chart allows you to quickly translate JSR microorganisms in the numeric index of the criterion of sensitivity of microorganisms to facilitate the physician's choice of drug for effective antibiotic therapy.

A method of evaluating the sensitivity of microorganisms to antimicrobial agents in the disk, including planting the test culture in a nutrient medium, applied to the disks containing the antimicrobial agents, the measurement of the diameters of zones of growth inhibition (JSR) microorganisms, characterized in that the measurement is conducted with the help of the device in the form of transparencies with 32 laps, located on it, which differ from each other by 1 mm diameters specified in the heart, and determination JSR studied culture is produced coincidentally with the diameter of the fixture, with an assessment of the sensitivity of microorganisms is determined by the ratio of the sensitivity of the microorganism, hoping it according to the formula

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where KCHM - coefficient of the sensitivity of the microorganism;

JSR - diameter zones of stunting,

when the value KCHM=1 or more microorganisms belong to the group of sensitive, when the value KCHM less than 1 moderately h

 

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