Treated wastewater effluent as a potential source of virulent and antibiotic resistant Yersinia species in receiving surface water.
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Date
2015
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Abstract
Yersinia enterocolitica is a potentially pathogenic bacterium transmitted through the faecal-oral
route. Typical symptoms include those associated with gastrointestinal disease, although
infection can also lead to more serious and invasive illnesses, particularly in sensitive
populations. Previous studies have detected Y. enterocolitica in surface water in various parts of
the world, and studies have reported the intake of untreated water to be one of the potential risk
factors for Y. enterocolitica infection. This study investigated the antibiotic resistant patterns and
the virulence determinants of the previously identified Y. enterocolitica in treated wastewater
effluents and the receiving rivers. In addition, the antibiogram and virulence factors of these
isolates were determined in order to establish the possible effects posed by these isolates to the
users of receiving surface waters. Finally, the genetic relatedness of the isolates was established
by Random Amplified Polymorphic DNA (RAPD-PCR). The antibiotic susceptibility assays
revealed that the isolates were resistant to ampicillin (100%), amoxicillin (98%), cefuroxime
(96%), cefalothin (90%), streptomycin (93%), chloramphenicol (100%), tetracycline (100%) and
trimethoprim (100%). The calculated multiple antibiotic resistance (MAR) indices of the Y.
enterocolitica isolates ranged from 0.5-0.66, suggesting high multi-antibiotic resistance among
the isolates. A high prevalence (59%) of class 2 integrin was found among the isolates, with 26
and 6% of the isolates in possession of class1 and class 3, respectively. The integrase genes
detection showed that the isolates possessed 3 classes of integrons, detected in 59%, 26% and
6% of the isolates, respectively. The virulence determinant assays using crystal violet staining
showed that only 21% (15/70) of the isolates could retain the purple colour suggesting that they
may be the virulent strain of Y. enterocolitica. The negative MBL activity suggests that the tested
isolates do not demonstrate any hydrolytic activity for the degradation of cephalosporins.
Virulence gene detection via PCR showed that the most abundant gene is the ystA (56%)
followed by ail (34%), both chromosomally located. The plasmid located genes were detected in
3% of the isolates for both Vir/Lcr and yadA. The genotypic characterization of the tested
isolates revealed two main clusters (A and B), with cluster A comprising the majority of the
isolates (68%) and include the Y. enterocolitica positive control, whilst cluster B grouped 31% of
the isolates. had 31% similarity to the control.
Description
Master of Science in Microbiology. University of KwaZulu-Natal, Durban, 2015.
Keywords
Theses - Microbiology.