Removal of Hepatitis B virus surface HBsAg and core HBcAg antigens using microbial fuel cells producing electricity from human urine

© 2019, The Author(s). Microbial electrochemical technology is emerging as an alternative way of treating waste and converting this directly to electricity. Intensive research on these systems is ongoing but it currently lacks the evaluation of possible environmental transmission of enteric viruses originating from the waste stream. In this study, for the first time we investigated this aspect by assessing the removal efficiency of hepatitis B core and surface antigens in cascades of continuous flow microbial fuel cells. The log-reduction (LR) of surface antigen (HBsAg) reached a maximum value of 1.86 ± 0.20 (98.6% reduction), which was similar to the open circuit control and degraded regardless of the recorded current. Core antigen (HBcAg) was much more resistant to treatment and the maximal LR was equal to 0.229 ± 0.028 (41.0% reduction). The highest LR rate observed for HBsAg was 4.66 ± 0.19 h−1 and for HBcAg 0.10 ± 0.01 h−1. Regression analysis revealed correlation between hydraulic retention time, power and redox potential on inactivation efficiency, also indicating electroactive behaviour of biofilm in open circuit control through the snorkel-effect. The results indicate that microbial electrochemical technologies may be successfully applied to reduce the risk of environmental transmission of hepatitis B virus but also open up the possibility of testing other viruses for wider implementation

Bacteriophages: update on application as models for viruses in water

Phages are valuable models or surrogates for enteric viruses because they share many fundamental properties and features. Among these are structure, composition, morphology, size and site of replication. Even though they use different host cells, coliphages and Bacteroides fragilis phages predominantly replicate in the gastro-intestinal tract of humans and warm-blooded animals where enteric viruses also replicate. A major advantage of phages is that, compared to viruses, they are detectable by simple, inexpensive and rapid techniques. In view of these features, phages are particularly useful as models to assess the behaviour and survival of enteric viruses in the environment, and as surrogates to assess the resistance of human viruses to water treatment and disinfection processes. Since there is no direct correlation between numbers of phages and viruses, phages cannot to a meaningful extent be used to indicate numbers of viruses in polluted water. The presence of phages typically associated with human and animal excreta indicates the potential presence of enteric viruses. However, the absence of these phages from water environments is generally a meaningful indication of the absence of enteric viruses. This is because phages such as somatic coliphages, F-RNA coliphages and B. fragilis phages generally outnumber enteric viruses in water environments, and they are at least as resistant to unfavourable conditions including those in water treatment and disinfection processes. However, using highly sensitive molecular techniques viruses have been detected in drinking water supplies which yielded negative results in conventional tests for phages. Initially, data on phages were rather confusing because a wide variety of techniques was used. However, techniques for the detection of phages are being standardised internationally. This applies in particular to somatic and F-RNA coliphages, and B. fragilis phages, which are most commonly used in water quality assessment. Reliable and practical techniques now available include direct quantitative plaque assays on samples of water up to 100 ml, and qualitative tests on 500 ml or more using highly sensitive enrichment procedures. WaterSA Vol.27(2) 2001: 251-26

Immunomagnetic separation of Escherichia coli O157:H7 from environmental and wastewater in South Africa

Recreational and drinking water supplies polluted with sewage have become an important source of E. coli O157:H7 infection. Immunomagnetic separation (IMS) has been extensively used for the isolation of E. coli O157:H7 from food and stool samples but not for samples such as wastewater. In this study the IMS method was used in combination with the E. coli O157:H7 selective media, immunoassays, biochemical tests and PCR, to assess the prevalence of E. coli O157:H7 in selected sewage and environmental water in South Africa. Environmental and wastewater were seeded with E. coli O157:H7 to determine the sensitivity and selectivity of the enrichment-IMS-selective agar method. Naturally occurring E. coli O157:H7 organisms were recovered from selected samples by means of IMS. The IMS concentrates were plated on three selective E. coli O157:H7 media. E. coli O157:H7 was detected in seeded sewage and river water samples with numbers as low as 1.2 cfu.ml-1. The IMS procedure was used to investigate the prevalence of E. coli O157:H7 in randomly selected sewage and river water samples in South Africa. A total of 91 sewage- and 40 river water samples were tested and 17.6% and 20% yielded suspected E. coli O157:H7 colonies on CT-SMAC agar medium respectively. PCR was used to confirm the presence of genes coding for Shiga toxin-1 (Stx1), Shiga toxin-2 (Stx2), enterocyte attaching and effacing genes (eaeA) and enterohaemolysin (hly). Standard immunoassay kits specific for the O157 and H7 antigen and a biochemical indole test were used for further E. coli O157:H7 confirmation. Three colonies from one sewage sample (1.1 % of all sewage samples) agglutinated with anti-E. coli O157 and H7 antiserum and contained the genes coding for Stx2, eaeA and hly. None of the colonies isolated from the river water samples were positive for E. coli O157:H7. CT-SMAC proved to have limited E. coli O157:H7 selective capabilities from samples such as sewage with high bacterial counts. Seeded sample experiments indicated that IMS is a suitable method for isolating E. coli O157:H7 from samples with high bacterial interference and low numbers of E. coli O157:H7. Evidence has been presented that the enrichment-IMS-selective agar procedure substantially increased the sensitivity of E. coli O157:H7 isolation compared to direct plating of test samples onto selective agar generally practised in the past. WaterSA Vol.29(4) 2003: 427-43