The main goal of this study is to alert researchers who work with cell cultures for the risk of contamination by structures called nanobacteria (NB). NB are tiny structures with size varying from 80 to 500 nm, commonly occurring in clusters and producing a biofilm which contains carbonate or hydroxyl apatite. The most likely source of cell culture contamination by such organisms is serum used as supplement in culture media. The presence of NB leads to a progressive culture deterioration with accumulation of granules (probably phagocytized NB) in cytoplasmic vacuoles, an increasing number of dead cells in the supernatant and degeneration of cells that remained attached to the bottom of the vessel. NB can also be found in culture supernatants where they are found in clusters with variable size and displaying brownian movement. In this study, 19 cell lineages, 8 batches of sera and 1 batch of growth supplement from different sources were analyzed. Samples from sera were cultured in Eagle's Minimum Essential Medium (E-MEM) or incubated directly at 37ºC. Tests carried out to detect the presence of extracellular bacteria, Mycoplasma sp and viruses were all negative. Analysis by scanning electron microscopy (SEM) revealed tiny oval structures less than 500 nm in size, isolated or in small groups, in all material analyzed except in one fetal bovine serum batch.
Purpose: Identifying the source of stone formation in recurrent stone formers has always been a big problem. Material and Methods: In this study kidney stones from 52 patients were submitted to direct examination by scanning electronic microscopy (SEM) after manual fracture and 27 calculi were cultured in Eagle’s Minimum Essential Medium (E-MEM) and Brain-Heart Infusion (BHI) for eight weeks at 37°C in 5% CO<sub>2</sub> atmosphere. Twenty-seven powdered and demineralized stones were suspended in sterile PBS, filtered through 0.22 m-pore-size sterile filters Millex (Millipore, Massachusetts, USA) and submitted to DNA extraction (Quiagen-Brazil). Platinum PCR SuperMIX (GIBCO-BRL), primers (Invitrogen), and Ultra Pure Water (Advanced Biotechnologies, Columbia, MD) were used for PCR (Polymerase Chain Reaction), which was generally conducted for 30 or 35 cycles with annealing of primers for 40 sec at 55°C and extension for 1 min at 72°C. Results: In 36 out 52 (69%) kidney stones it was detected the presence of biofilm coating the mineral surface of the stone when examined by SEM, consisting of coccoid particles, isolated or clustered, with diameter of 500 nm or less. Eleven out 27 (41%) kidney stone cultures produced white-colored sediment on the bottom of the tubes after eight-week incubation, revealing tiny structures similar to those observed directly by SEM. These structures were similar in size and morphology to spherical apatite particles previously observed in human kidney stones and named as nanobacteria (NB). No PCR products were observed in the samples. Conclusion: We found a strong correlation between renal stones and calcifying nanoparticles (CNP) in this study and these results open a new insight on this area to explore the etiology of stone formation. Whether NB/CNP are truly microorganisms or self-propagating mineral compounds is still controversial and its contribution, if any, in apatite nucleation and crystal growth remains uncertain
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