Experimental examination of bacterial diseases

(1) Drug sensitivity test refers to clinical microorganisms.

(2) Combined drug sensitivity test with reference to clinical microorganisms.

(3) The principle and method of serum bactericidal test are the same as those of drug sensitivity test by tube dilution method. The patient's serum treated with antibacterial drugs was detected by the patient's own pathogenic bacteria. The maximum dilution of patient serum that can inhibit bacterial growth is serum bactericidal titer. It is generally believed that the serum bactericidal titer is higher than 1∶8, indicating that the treatment is effective, and it may fail if it is lower than 1∶4. This experiment has great reference significance for the prognosis of patients with severe infection (such as infective endocarditis) or neutropenia complicated with sepsis. But in this experiment, pathogenic bacteria must be obtained.

(IV) Determination of β -lactamase activity of bacteria Many pathogenic bacteria can produce β -lactamase and hydrolyze the β -lactam ring in the structure of penicillin and cephalosporin, making them lose their antibacterial activity, such as the resistance of Staphylococcus aureus, Neisseria gonorrhoeae and Influenza Bacillus to penicillin G or ampicillin. Therefore, it is of great reference significance for clinical drug selection to detect the production of β -lactamases while conducting drug sensitivity tests on the above bacteria. Determination methods include iodometry, microbiological method, acidity (pH) method, etc. Cefonitrothiophene (nitrocephalosporin or cephalosporin paper) method is the most sensitive and reliable, and the results can be obtained within a few minutes.

(5) Blood drug concentration monitoring or therapeutic drug monitoring (TDM). The intensity of drug action is directly proportional to the drug concentration in tissues and body fluids, and the latter is parallel to the blood drug concentration. Therefore, the determination of blood drug concentration can be used as an indirect index of drug concentration in infected sites. Therapeutic drug monitoring is to determine the drug concentration in body fluids, especially in blood, by using advanced and sensitive detection technology, so as to study the relationship between blood drug concentration and curative effect and toxicity, determine the best dose and administration interval, improve drug efficacy and reduce adverse reactions. In the application of antibacterial drugs, blood drug concentration monitoring is mainly suitable for drugs with low toxicity in therapeutic index, such as aminoglycoside antibiotics and vancomycin, or those who have or may have drug accumulation in the body during the application of chloramphenicol to newborns or infants, or when patients with renal dysfunction use antibacterial drugs excreted by their kidneys. Sometimes high-dose penicillin therapy should be monitored to prevent penicillin encephalopathy.

The methods for determining blood drug concentration include microbiological method, radioimmunoassay, enzyme immunoassay, fluorescence immunoassay, gas chromatography and high performance liquid chromatography. The latter has the advantages of rapidity, high specificity and high sensitivity, but it also has its own shortcomings and limitations, requiring special equipment and instruments.