Introduction. In some cases, there is a dissociation between the severity of complaints, physical examination data, and levels of contamination of the biomaterial in the differential diagnosis of various categories of prostatitis (NIH-NIDDK, 1995). Patients note the presence of pronounced symptoms when verifying the threshold indicators of microbial load (104-105 CFU / ml) of prostate secretion or post-massage urine in a few observations. However, clinical manifestations and deviations in objective indicators are not so significant in some patients with higher titers of contamination.
Purpose of the study. To evaluate the relationship between the microbial load indices and the degree of pathomorphological changes in the prostate tissue during infection with the «reference» uropathogen E. coli in various titers under experimental conditions
Materials and methods. Animal model was carried out using the FELASA protocols. Experimental individuals: 16 «New Zealand» rabbits, weight: 3580 [3480; 3695] (3300–4410), age: 25 [24; 26] (23–28) weeks. Uropathogen used: E. coli. Titers: 103 CFU / ml, 105 CFU / ml, 107 CFU / ml. Infection pathway: inoculation of the uropathogen was performed through urethra according to the modified technique of J.C. Nickel. Randomization: all lab animals were evenly divided into 4 groups of 4 animals, taking into account the initial titer of the uropathogen and the observation period - experimental groups 1 (103 CFU / ml), 2 (105 CFU / ml), 3 (107 CFU / ml); group 4 was control (Sol.NaCl 0.9%). Observation terms: 1, 3, 7 and 14 days, after which the animals were euthanized and dissected. 4 biopsies (1A-1D) for bacteriological (MacConkey agar - «HiMedia», India) and 2 biopsies (P1-P2) for morphological (Hematoxylin-eosin - «BlikMediklProduction», Russia; magn. 10x, 40x, 100x, 400x) studies were formed from various parts of the prostatic complex (prostate + proprostate + paraprostate). A three-point grading system was used for morphometric assessment of destructive changes in the prostate tissue in different groups. Analytical processing of the results was carried out using the software packages Microsoft 365 («Microsoft», USA) and Statistica 10.2 («StatSoft Inc.», USA) by methods of descriptive and nonparametric statistics.
Results. The maximum total absolute / median values of the seeding of biopsy specimens of the prostatic complex were revealed (∑ titer, 1A-1D) in group 1 and amounted to 76 lg CFU / ml / 5.00 [4.00; 5.25] lgCFU / ml, in group 2 defined as intermediate - 57 lgCFU / ml / 3.50 [3.00; 4.00] lgCFU / ml, and in group 3 were minimal - 48 lgCFU / ml / 3.00 [3.00; 3.25] lg CFU / ml according to the indicators of bacteriological research in the period from 1 to 14 days. Nevertheless, it was found that the cumulative maximum degree of histological changes in the prostate was recorded in group 2 (∑ p. - 84), in group 1 it was defined as intermediate (∑ p. - 68), and in group 3, it was the smallest (∑ p. - 64) according to the data of pathomorphological studies. When comparing daily changes in the seeding values and nominal indicators of inflammatory lesions in the prostate tissue, only in group 1, the trend graphs had a synchronous trend - an increase in microbial load led to the formation of more severe pathomorphological transformations on the day 7; in group 2, destructive changes were significant, and the rates of contamination, on the contrary, were minimal on the day 7; in group 3 a pronounced pathomorphological transformations in the tissues were noted on the day 3 and 7, but the microbial load of the tissues gradually decreased from the day 1. Also, differences in the increase in the “reactivity” of changes in the affected tissues were determined: in groups 1 and 3, a torpid reaction was revealed, accompanied by the development of moderate inflammatory changes on the day 1 and an “abrupt” increase in the intensity of destruction by the day 3; in group 2, in turn, a rapid reaction was determined, that characterized by the formation of a more pronounced destructive process already from the day 1.
Conclusion. It was found that the parameters of contamination do not fully reflect the nature and severity of pathological changes in the prostate. Low titers of the uropathogen induce the development of an inflammatory process comparable in the severity of changes with that at higher concentrations. On the contrary, inoculation of obligate pathogenic titers does not always lead to a pronounced increase in microbial load but causes significant inflammatory changes in the prostate.

Keywords: bacterial prostatitis, causative uropathogens, experimental modeling, diagnosis of prostatitis, microbial load, prostate secretion, post-massage urine