Prostate calcifications: A case series supporting the microbial biofilm theory

Abstract

Purpose: Prostate calcifications are a common finding during transrectal prostate ultrasound in both healthy subjects and patients, but their etiopathogenesis and clinical significance are not fully understood. We aimed to establish a new methodology for evaluating the role of microbial biofilms in the genesis of prostate calcifications.

Materials and methods: Ten consecutive patients who had undergone radical prostatectomy were enrolled in this study. All of the patients presented with prostate calcifications during transrectal ultrasound evaluation before surgery and underwent Meares-Stamey tests and clinical evaluation with the National Institutes of Health Chronic Prostatitis Symptom Index and the International Prostate Symptom Score. At the time of radical prostatectomy, the prostate specimen, after removal, was analyzed with ultrasonography under sterile conditions in the operating room. Core biopsy specimens were taken from the site of prostate calcification and subjected to ultrastructural and microbiological analysis.

Results: The results of the Meares-Stamey test showed only 1 of 10 patients (10%) with positive cultures for Escherichia coli. Two of five patients (40%) had positive cultures from prostate biopsy specimens. Enterococcus faecalis, Enterococcus raffinosus, and Citrobacter freundii were isolated. Ultrastructural analysis of the prostate biopsy specimens showed prostate calcifications in 6 of 10 patients (60%), and a structured microbial biofilm in 1 patient who had positive cultures for E. faecalis and E. raffinosus.

Conclusions: Although the findings are supported by a low number of patients, this study highlights the validity of the proposed methodology for investigating the role of bacterial biofilms in the genesis of prostate calcification.

Keywords: Biofilms; Prostate; Prostate diseases; Prostatitis.

Fig. 1. (A) Prostate core biopsy specimen showing several calcifications (brighter areas) within the tissue (darker areas). (B) Calcifications varied in size from a few to several hundred micrometers. (C) At high magnification, the calcification surface showed a crystalline structure with protein residuals and a possible extracellular polymeric matrix from the microbial biofilm. Scanning electron microscopy images were realized by collecting the signal from back-scattered electrons, giving compositional contrast between tissue and calcifications. (A) ×39, (B) ×500, (C) ×10,000.

Fig. 2. (A) Prostate core biopsy specimen with calcifications and corpora amylacea (brighter areas) within the tissue (darker areas). (B) High-magnification details of some round-shaped structures, morphologically compatible with corpora amylacea. (C) Intratissual aggregate of microorganisms with coccoid morphology with extracellular polymeric matrix (microbial biofilm). Scanning electron microscopy images were realized by collecting the signal from back-scattered electrons (A) or secondary electrons to have the highest morphological detail. (A) ×100, (B) ×2,000, (C) ×8,000.