Q-222. Detection of Giardia duodenalis Assemblages and Human-Specific Bacteroides Fecal Markers in Sewage-Polluted Waters from Caracas, Venezuela

L. J. Querales, L. C. Caraballo, H. Takiff, W. Q. Betancourt;
Inst. Venezolano de Investigaciones Cientificas (IVIC), Caracas, VENEZUELA.

Giardia is a protozoan parasite frequently detected in human fecal samples submitted to diagnostic laboratories in Caracas, Venezuela. However, little is known about the occurrence of species and genotypes associated with human infection. Molecular analysis of Giardia spp. provides information on the distribution of host-adapted genotypes of public health importance, and these genotypes can be used to differentiate sources of fecal contamination in environmental waters. In this study, the presence of G. duodenalis assemblages was determined in urban sewage and sewage-polluted waters by nested PCR amplification and sequence analysis of the tpi gene. Human-pathogenic assemblage occurrence and the presence of the general and human-specific Bacteroides fecal markers (HF183, B. thetaiotaomicron) were compared. Samples of urban sewage (n=12) and sewage-polluted environmental waters (n=24) were concentrated by centrifugation (1,800 X g, 15 min). DNA extraction was performed by two different procedures: (i) the freeze-thaw method in the presence of Chelex-100 for sucrose-purified Giardia cysts, and (ii) a silica based DNA extraction procedure for the Bacteroides fecal markers. The two human-pathogenic Giardia assemblages (A and B) were found in all urban sewage and sewage-polluted waters. The general and human-specific Bacteroides fecal markers (HF183) were also detected in all samples. We conclude that HF183 might be used as a marker of human pathogen contamination in waters. This is the first molecular study of Giardia and Bacteroides fecal markers in Venezuela. Further research is warranted in order to establish new molecular approaches for detection and genetic characterization of waterborne protozoan pathogens and potential surrogate indicators in this geographical region. Future studies should consider how these tools could be employed to yield epidemiological insights about human pathogens in aquatic environments.