Frequency and risks associated with Clostridium difficile-associated diarrhea after pediatric solid organ transplantation: a single-center retrospective review.

BACKGROUND: Morbidity and mortality related to Clostridium difficile infection (CDI) has increased, but epidemiology and risk factors within pediatric solid organ transplant (SOT) recipients are uncertain. METHODS: A retrospective cohort study of SOT recipients age ≤18 years at transplantation from 2010 to 2013 was performed. Patients with CDI were compared with matched CDI-negative controls with diarrhea. RESULTS: Of 202 patients, the majority were male (58%) and Caucasian (77%). Kidney (42%) was the most common organ transplanted, followed by liver (38%), heart (17%), and multivisceral/intestine (3%). Age ranged from 3 weeks to 18 years (median 4.7 years, mean 6.6; interquartile range [IQR] 1.5-11.2). In 104 SOT recipients, at least 1 unformed stool was tested; 25 patients were positive for CDI. Most testing occurred by 60 days post transplant (mean 164, median 57, IQR 14-227). First negative tests occurred concurrently (mean 153, median 54, IQR 13-214) to the 25 patients with CDI (mean 199, median 65, IQR 32-238). In univariable analyses, age, gender, ethnicity, obesity, and calcineurin inhibitor choice were not associated with CDI. Liver recipients were more likely to have CDI (18.4% liver, 4.7% kidney, 8.8% heart, P < 0.01). Twenty CDI patients were matched to 35 controls. In multivariable analyses, neither recent hospitalization nor antibiotic duration or intensity was associated with CDI. Acid-blockade appeared protective (risk ratio 0.13, 95% confidence interval 0.02-0.78). CONCLUSIONS: CDI occurs in 12% of pediatric SOT recipients, but 24% of those tested with diarrhea were positive. In patients with diarrhea, prior hospitalization and antibiotic duration or intensity were not associated with CDI.

Extraosseous calcification. Evidence for abnormal pyrophosphate metabolism in uremia.

The inorganic constituents and crystalline features of extraosseous calcium-phosphate deposits obtained from dialyzed uremic and hypercalcemic patients were studied. Visceral calcification (heart, lung, and kidney) in hypercalcemic patients exhibited either an amorphous or apatitic X-ray diffraction pattern. Uremic visceral calcification consistently gave an amorphous diffraction pattern. Although the calcium content of uremic and hypercalcemic visceral deposits was similar, other inorganic constituents were different. The mean pyrophosphate was 11 +/- 11.8 and magnesium 4.91 +/- 3.86 mg/g in the uremic group as compared to 0.92 +/- 0.24 and 1.36 +/- 1.26 mg/g in the hypercalcemic group (P less than 0.025). After incineration hypercalcemic visceral deposits having an amorphous diffraction pattern were found to generate pyrophosphate supporting the presence of brushite in these deposits. The small amount of pyrophosphate in apatitic deposits from both uremic and hypercalcemic patients actually decreased after incineration and the pyrophosphate content of uremic visceral deposits was unchanged by incineration. It is concluded that in hypercalcemic patients the initial visceral deposit is brushite which is subsequently transformed to apatite. Arterial and tumoral calcium-phosphate deposits in uremic patients were also apatite. Uremic visceral calcium-phosphate deposits are an unique mineral high in magnesium with approximately 30% of the phosphorus present as pyrophosphate. The high pyrophosphate content of these deposits could alter their crystalline structure and prevent the transformation to apatite. The infrared features, high magnesium content of the deposit, and resistance of pyrophosphate in the deposit to hydrolysis by pyrophosphatase suggests that the pyrophosphate may be deposited as the magnesium salt.