Cartagena, Colombia, was one of the last cities in the Americas known to have endemic poliomyelitis. After 3 cases were identified in 1991, two approaches for detecting continued silent transmission of wild polioviruses within a high-risk community were used: stool surveys of healthy children and virologic analysis of community sewage. Wild type 1 polioviruses were isolated from 8% of the children studied and from 21% of sewage samples. The proportions of wild polioviruses, vaccine-related polioviruses, and nonpolio enteric viruses were similar for both approaches. Wild poliovirus sequences were also amplified directly from processed sewage samples by the polymerase chain reaction using primer pairs specific for the indigenous type 1 genotype. The last reported cases associated with wild polioviruses in the Americas occurred in Colombia (8 April 1991) and Peru (23 August 1991). Direct sampling for wild polioviruses in high-risk communities can provide further evidence that eradication of the indigenous wild polioviruses has been achieved in the Americas.
In order to isolate human enteric viruses from sewage, a study has been undertaken in Brazil. From 55 sewage samples, 433 virus strains have been isolated. These comprised 70.7% poliovirus, 19.2% echovirus and 7.6% coxsackievirus, 2.5% remained untyped. Five different methods were used for virus recovery: adsorption to and elution from membrane filters; acidic precipitation; concentration through membrane filters, with reconcentration by organic flocculation; concentration on aluminum hydroxide; aluminum sulfate precipitation. The sewage sample were plaqued in bottle cultures BS-C-1 cell line. This cell line allowed a recovery of 22 different serotypes of enteroviruses: the three poliovirus types, 14 types of echoviruses, four types of coxsackie B virus and one type of coxsackie A virus.
A rapid and sensitive method for the detection of wild poliovirus from sewage samples using the polymerase chain reaction (PCR) technique was investigated. To eliminate the toxicity of sample concentrates to the enzymatic system used in PCR, a methodology was developed for the purification of these concentrates, consisting of treatment with trichlorofluoroethane and Sephadex column chromatography. The viral RNA was extracted from the purified concentrates, submitted to PCR with primers specific for Brazilian wild poliovirus type 1 and for Sabin types 1, 2 and 3. The amplified products were detected by electrophoresis in vertical polyacrylamide gels and stained with ethidium bromide. The results suggest that sewage sampling for environmental surveillance, combined with the rapid and precise PCR technology, provides a powerful tool for assessment of the success of the poliovirus eradication programme.
The monitoring program for Enterovirus and Salmonella in raw and treated waters, from nine water treatment plants of Great São Paulo, Brazil, has been developed by CETESB- The São Paulo State Environmental Protection Agency under a contract with SABESP - Water Industry and Sewage Works Company, since 1976. For Salmonella analysis a total of 904 samples of raw water and 997 of treated water were analysed during these last 10 years. A percentage of 30.6 of 904 raw water samples revealed the presence of Salmonella. These pathogenic bacteria were absent in treated water. For Enterovirus, 383 samples of raw water were analysed, out of these 14.9% revealed the presence of virus. From a total of 366 viruses isolated 195 (53.3%) were Poliovirus, 79 (21.6%) were Echovirus, 30 (8.2%) were Coxsackievirus and 62 (16.9%) isolates were untyped. As far as treated water is concerned for the 10 year study, only 3 out of 975 samples were positive for viruses (Poliovirus type 2, Coxsackie A16, and one isolate untyped). Coliforms and Salmonella were not detected in these 3 samples. Residual chlorine was present. In the sample where Poliovirus type 2 was present, free residual chlorine was 1.5 mg/L and pH 9.2. This survey demonstrated that the conventional procedures for water treatment used by SABESP were in general efficient for Enterovirus and Salmonella removal.
A study has been undertaken to determine a suitable method for virus isolation from sewage samples in Sao Paulo State, Brazil. The samples were concentrated by the following methods: adsorption on aluminum hydroxide flocs; precipitation by aluminum sulfate; adsorption to and elution from membrane filters followed by organic flocculation; direct organic flocculation as a single-step concentration method and electropositive cartridge filter, AMF Cuno. The BS-C-1 cell line and the plaque technique were used for virus assay. Out of the methods employed, the Al(OH)3, method presented the best recovery rates (185.6 PFU), followed by AMF Cuno method (58.0 PFU), organic flocculation as a second-step concentration method (40.6 PFU), direct organic flocculation (24.3 PFU) and adsorption on Al2SO4). (6.0 PFU). From a total of 1,037 viruses isolated, 176 strains were identified: 110 were Coxsackie B virus (62.5%), 57 were poliovirus (32.4%) and 7 were Echovirus (4.0%). Two virus strains remained untyped.
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