VERTICAL TRANSMISSION OF BACTERIAL PATHOGENS FROM MUNICIPAL WASTE DUMPS TO WASTE SITE WORKERS: ROLE OF MOLECULAR AND PHENOTYPIC PROFILING OF ISOLATES

Having noticed some phenotypic similarities in bacteria isolates from hands or clothings of waste dump workers and those from the leacheates or topsoils of the dumpsites in Benin City, the need for further investigations in order to possibly establish a positive linkage between these bacteria strains became necessary. We therefore selected 8 pairs of phenotypically similar species from the site workers and dumpsites from 4 locations (University of Benin, Costain, Government Reservation Area and Benin Bye-pass) as our study bacterial candidates. The selected isolates (Bacillus subtilis, staphylococcus aureus, Escherichia coli, Proteus mirabilis, Klebsiella aerogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens) were tested in pairs and were tested for their susceptibilities to 10 antimicrobial agents and their resistogram patterns were consequently determined. The isolates were also assayed for presence of heat labile or heat stable enterotoxins and for their invasiveness. They were further subjected to Multiplex PCR runs with primers for genes coding for virulence and resistance to ampicillin, chloramphenicol, streptomycin, sulphonamide and tetracyclin. Phenotypic characterization of the bacteria isolates showed that similar species were invariably isolated from topsoils and leacheates at dumpsite and from the hands and clothings of site workers. The resistogram patterns showed that 5 out of the 8 pairs of strains tested were identical, thus suggesting possible vertical bacterial transmissions at the affected locations.Similarly, the pathogenicity assay profiles showed that 6 out of 8 paired strains gave identical results. However, results from the Multiplex PCR tests revealed that only the paired Pseudomonas aeruginosa strains appeared identical. We conclude that although there were phenotypic and molecular evidence of possible vertical transmissions of bacteria from waste dumps to the site workers, we suggest that the ultimate markers of similarity of strains may lie with genomic sequencing of bacteria that are being matched for strain similarity.