Wastewater post-treatment for simultaneous ammonium removal and elemental sulfur recovery using a novel horizontal mixed aerobic-anoxic fixed-bed reactor configuration.

A novel horizontal mixed anoxic-aerobic fixed-bed reactor configuration based on nitrification coupled with autotrophic denitrification using hydrogen sulfide as an electron donor was developed. The nitrification removal efficiency (RE) reached values greater than 99% but was slightly affected by the accumulation of dissolved sulfur species in the liquid phase. The denitrification RE reached 99% with a H2S inlet load of 28.6 g S m-3 h-1, although the use of aluminum polychloride (PAC) as a sulfur coagulant in the anoxic zone affected the buffering capacity of the system and resulted in a decrease in the RE. The performance of the reactor was primarily affected by the buffering capacity of the system, and this effect could be controlled with an increase in the NaHCO3 concentration. The recovery of biogenic elemental sulfur was possible using PAC as a coagulant, although the solid collected at the bottom of the settling tank contained only 1.5% S0.

Human leukocyte antigen DR markers as predictors of progression to liver transplantation in patients with chronic hepatitis C.

OBJECTIVE: Because many patients with chronic viral hepatitis do not progress to end-stage liver disease, it is possible that host factors such as human leukocyte antigen (HLA) differences are important. Our aims were to determine HLA marker-specific rates of progression to liver transplantation among patients with chronic hepatitis C; and to determine if polymerase chain reaction (PCR)-based HLA DRB1 typing can be performed on stored serum samples. METHODS: Forty-two hepatitis C virus RNA-positive liver transplant patients and 87 untransplanted patients were included in a Cox proportional hazards model to test whether the occurrence of certain HLA DRB1 markers were associated with progression to liver transplantation. HLA DRB1 typing was performed on stored serum samples using a PCR method. RESULTS: There were no differences among the HLA DRB1 markers with regard to the HLA marker-specific rate of progression to transplantation among patients with chronic hepatitis C. CONCLUSIONS: HLA DRB1 markers do not appear to be associated with progression of disease in chronic viral hepatitis C. It is possible to perform PCR-based HLA DRB1 typing on stored frozen serum samples.

Early detection of hepatitis C allograft reinfection after orthotopic liver transplantation: a molecular and histologic study.

After orthotopic liver transplantation (OLT), patients with chronic hepatitis C virus (HCV) infection show nearly universal persistence of viremia and reinfection of the liver, but identifying the point at which the liver is reinfected morphologically can be difficult. One tool that may potentially be useful to detect reinfection is reverse transcriptase-polymerase chain reaction (RT-PCR), which has proven to be highly sensitive for detecting HCV RNA in formalin-fixed paraffin-embedded liver tissue. Our purpose was to gain insight into the time frame of HCV reinfection by assaying for HCV RNA in serial posttransplant liver biopsy specimens. Our study population consisted of 14 patients who underwent liver transplantation for hepatitis C and had confirmed HCV RNA in pretransplant serum, absence of HCV RNA in donor livers, and available consecutive posttransplant liver allograft specimens. We performed RT-PCR for HCV RNA in serial posttransplant liver biopsy specimens, beginning at 1 week until at least one biopsy from each tested positive. HCV RNA was detected in liver tissue by RT-PCR in 1-week post-OLT liver samples in 6 of 14 (42.8%) patients, the earliest being 5 days post-OLT. Eventually, each of the remaining eight samples became RT-PCR positive as well; the first detections occurred in these at 3 weeks (three cases), 4 weeks (three cases), 48 weeks (one case), and 144 weeks (one case). Histologic identification of hepatitis C recurrence was relatively insensitive in relation to these molecular data. These data suggest that (1) HCV RNA reinfection is nearly universal after liver transplantation in patients with chronic hepatitis C infection, (2) molecular reinfection by HCV occurs at a variable interval post-OLT, with the majority of allograft livers reinfected as early as 1 week, and (3) morphologic features of hepatitis C are usually appreciable at the time of "molecular" recurrence.

Reverse transcriptase-polymerase chain reaction fails to detect peripheral-blood hepatitis C RNA in formalin-fixed liver tissue.

Currently, one of the major indications for liver transplantation is infection with hepatitis C virus (HCV). Many studies have suggested that recurrent infection with HCV is universal after transplantation. Fastidious techniques, such as reverse transcriptase-polymerase chain reaction (RT-PCR), have proved to be highly sensitive for detecting HCV RNA in serum and in fresh-frozen and formalin-fixed paraffin-embedded (FFPE) liver tissue. In this study, we wanted to determine whether the identification of HCV RNA in liver tissue by RT-PCR might reflect the detection of circulating HCV RNA in blood within the tissue, rather than implying true tissue infection. We performed RT-PCR for HCV RNA in FFPE liver biopsy specimens taken from 14 donor allografts shortly before and immediately after implantation into recipients. The recipients were known to have HCV RNA in serum and explanted liver tissue, as determined by RT-PCR. We were unable to detect HCV RNA in any of the study samples, either before or after transplantation. In a related study, qualitative and quantitative HCV RNA analyses were performed by RT-PCR and branched DNA (bDNA) amplification, respectively, on serum samples collected pretransplantation and immediately posttransplantation from 10 other patients who underwent transplantation for hepatitis C. HCV RNA was detected in all serum samples before and after transplantation by RT-PCR; however, the bDNA assay detected HCV RNA in only 6 of 10 samples pre-orthotopic liver transplantation (OLT) and in none of the immediately post-OLT samples. In our system, despite the RT-PCR detection of HCV RNA in serum before and after the transplantation, HCV RNA is not detectable in the peripheral blood that accompanies formalin-fixed liver tissue. This implies that RT-PCR detection of HCV RNA in tissue reflects true liver infection, rather than contamination by HCV RNA in accompanying peripheral blood.

Effects of formalin fixation and prolonged block storage on detection of hepatitis C virus RNA in liver tissue.

It has been suggested that prolonged formalin fixation and block storage adversely affect hepatitis C virus (HCV) ribonucleic acid (RNA) detection in tissue by reverse transcriptase-polymerase chain reaction (RT-PCR). We attempted to determine whether short-term perfusion fixation (3-5 days) or prolonged formalin storage adversely affects the detection of HCV RNA in paraffin-embedded tissue in comparison with 24-h fixation. Also, we examined the effects of prolonged storage of paraffin blocks on the sensitivity for HCV detection. We performed RT-PCR in formalin-fixed explanted livers from 20 liver allograft recipients known to be HCV positive (10 with specimens stored for 2-4 years and 10 with specimens stored for > 4 years). We compared the results of perioperative needle liver biopsy specimens fixed overnight with liver sections fixed by perfusion for 3-5 days and bulk liver tissue stored in formalin for years (mean, 6.25 years; range, 2-11 years). HCV RNA was detected in 100%, 85%, and 0% of specimens fixed for 24 h, 3-4 days, and years, respectively. We conclude that HCV can be readily detected in tissue fixed by formalin overnight, sensitivity decreases slightly with intermediate-length fixation, and HCV is rendered undetectable by prolonged fixation. In addition, retention of formalin-fixed tissue in paraffin blocks does not affect the sensitivity of HCV detection.