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Nontuberculous mycobacteria cause severe pulmonary, vascular graft, and bloodstream infections after cardiac surgery. Patient prognosis remains poor because of delays in diagnosis and treatment. Complicated aortic root infections caused by nontuberculous mycobacteria have been mostly fatal. We describe a case of a 50-year-old man who developed an invasive Mycobacterium chimaera infection with an aortic root pseudoaneurysm after a Bentall-de Bono procedure for a Stanford type A aortic dissection.

Mechanisms for the incorporation of carbonate into minerals of the apatite group have been explored in both the geological and medical literature. An important problem with respect to biological apatite, which requires further clarification, is the hydroxyl content of the carbonated apatite of bone. Recent studies reveal bone apatite to contain only ∼20 mol.% of the hydroxyl content of stoichiometric hydroxylapatite, with negligible chloride or fluoride. We investigated the hypothesis that the development of vacancies in the hydroxyl channel sites is a charge-balancing mechanism for the substitution of carbonate ions into hydroxylapatite. Raman spectroscopic analyses of synthetic carbonated apatites (containing 1 to >15 wt.% carbonate) show that their hydroxyl ion concentration correlates inversely with carbonate concentration. The specific relationship between carbonate and hydroxyl concentration in these samples closely follows the theoretical relationship defined by type-B substitution of carbonate for phosphate in the apatite structure. However, the 6–8 wt.% carbonate concentration in bone apatite falls far short of accounting for all of the hydroxyl depletion that occurs in bone apatite. Some of the additional hydroxyl depletion in bone apatite might result from substitution of Na+ for Ca2+, but further mechanism(s), perhaps (HPO4)2– substitution, must also play a significant role.

The properties of carbonated hydroxyl and chloro lead apatites, Pb 10 (PO 4 ) 6 (OH) 2 and Pb 10 (PO 4 ) 6 Cl 2 , serve as models for the incorporation of carbonate into their medically important calcium analogs, and there is likely incorporation of carbonate in an insoluble lead phosphate phase during lead remediation. We have synthesized a series of carbonated lead hydroxyl- and lead chloro-apatites at 60–80 °C. The incorporation of carbonate into the apatite structure was documented by X-ray powder diffraction, IR and Raman spectroscopy, 207 Pb solid state NMR spectroscopy, and elemental analysis. The carbonate content was determined by combustion analysis and confirmed by Raman spectroscopic analysis. As carbonate content increases in hydroxyl lead apatite, Raman spectra show changes in the phosphate stretching modes at 925 and 950 cm −1 , an increase in intensity and downshift of a new peak at 1050 cm −1 , and changes in the spectral features of the O–H stretch at about 3560 cm −1 . The variation in unit cell parameters for the chloro lead apatite as a function of carbonate content is similar to that documented for B-type substitution in calcium apatites. The 207 Pb NMR spectra corroborate B-type substitution. For the hydroxyl lead apatite, the changes in cell parameters suggest a combination of A- and B-type substitution. Solubilities of the carbonated lead apatites, determined by ICP-MS, increase slightly at low to moderate carbonate content, but more strongly at ca. 5.0 wt.% carbonate content. K sp values extrapolated to zero carbonate content reveal that the chloro lead apatite is indeed less soluble than the hydroxyl analog.

The syntheses of barium, cadmium, calcium, lead, and strontium apatites were performed in anhydrous polar organic solvents such as DMSO, anisole, pyridine, glacial acetic acid, ethanol, methanol, and DMF. Reactions took place under anhydrous conditions at temperatures ranging from 80 to 120 °C and for durations of 1–6 days. Ten apatites were synthesized in nonaqueous solvents and three (PbApF, PbApCl, SrApCl) were obtained using trimethylphosphate as the phosphate source. The use of nonaqueous solvents alleviates the formation of hydrogen phosphates which occurs in aqueous solution for some divalent cations. The limited solubility of even alkali metal salts in many of the solvents also produces nonapatitic double salts such as NaPb4(PO4)3, NaPbPO4, KPb4(PO4)3, Cd(OH)NO3, and NaBaPO4.

The recent definitive deuterium solid state NMR spectroscopic evidence for structural water in fluor- and hydroxylapatites has prompted our study of the conditions necessary for the removal and reincorporation of this important structural feature of apatites. Thermal gravimetric analysis of 20 synthetic carbonated calcium hydroxylapatite (CCaApOH) samples and nine carbonated calcium fluorapatite (CCaApF) samples has been used to determine the amount of structural and adsorbed water in each sample. No correlation between the weight percent and number of moles of structural water and the weight percent carbonate in CCaApOH and CCaApF has been found. In contrast, there appears to be a relationship between the amount of adsorbed water and the carbonate concentration in the fluorapatites prepared with a two hour digestion time, as well as in the hydroxylapatites prepared with one hour digestion periods, presumably due to the effect of carbonate on crystallite size. Structural water can be removed from the apatite lattice, primarily above 200 °C, but heating to over 550 °C is required for complete removal. This water can be partly reincorporated through an apparently kinetically-controlled process that is enhanced by an increase in time and/or temperature. We speculate that the incorporation of structural water occurs at the beginning of the formation of the apatite structure, approximately coincident with the incorporation of carbonate. We also speculate that water is both removed and reincorporated by proton transfers from water molecules to hydroxide ions.