Organization of production of Russia-made Mueller-Hinton broth

Objective.

To develop a technology for producing Russia-made Mueller-Hinton broth and to compare its quality in terms of physicochemical and microbiological parameters with a foreign analog in trials using reference microbial strains sharing common and complex nutritional requirements.

Materials and Methods.

The work investigated casein acid hydrolysates and Mueller-Hinton broths (MHBs) produced by the Federal Budgetary Institution of Science SRCAMB (MHB–Obolensk) and by BD BBL (MHB–BD) through testing 7 test strains of E. coli ATCC 25922, S. aureus ATCC 29213, P. aeruginosa ATCC 27853, E. faecalis ATCC 29212, S. pneumoniae ATCC 49619, H. influenzae ATCC 49766, and C. jejuni ATCC 33560 against 21 antibiotics (Sigma) by the broth microdilution method procedure according to EUCAST methodology. The latter three strains were cultured in broth supplemented with 5% lysed horse blood (Ecolab) and 20 mg/l of β-NAD (Sigma). Totally 192 tests for each broth were carried out. Physicochemical and microbiological quality parameters were determined according to GOST R 70393-2022. The content of divalent metal ions was determined by inductively coupled plasma atomic emission spectrometrу.

Results.

A technology allowing the production of Russia-made MHB of the conventional composition based on hydrochloric acid casein hydrolysate with a standardized content of calcium, magnesium ions and a reduced content of manganese, zinc and thymidine ions has been developed. Physicochemical (pH, amine nitrogen, chlorides) and microbiological (sensitivity, microbial growth rate, stability of their basic biological properties, and antimicrobial susceptibility) quality parameters did not differ from those for MHB–BD. MIC values for MHB–Obolensk and MHB–BD were consistent with targets in 162 tests (84.4%) and 168 tests (87.5%), respectively, and differed from the target by +/-one dilution in 30 (15.6%) and 21 (11%) tests, respectively. In analyzing the combination of meropenem – P. aeruginosa in MHB–BD, MICs exceeded the admissible interval by one double dilution in three tests. The content of calcium, magnesium, manganese and zinc ions in the broths complies with international standards. However, the concentration of the latter in MHB-BD turned out to be three times higher and amounted to 1.1 mg/l being a possible cause of the error in determining the MIC of meropenem. The results obtained require further study involving microbial clinical strains in order to optimize admissible concentrations of zinc ions.

Conclusions.

Conventional a Russia-made MHB that meets the requirements of international standards has been developed. The broth is not inferior to its foreign analog in quality as shown in comparative studies using reference strains with common and complex nutritional needs.