MSc (Microbiology) / Department of Microbiology / Background: The occurrence of microorganisms and endocrine disrupting chemicals
(EDCs) in water poses a serious concern due to their effects on humans, animals and
environment. In recent years, EDCs have been increasingly reported in rivers that
receive large amounts of wastewater effluents. Of all the EDCs, natural and synthetic
hormones are among those that are recognized for their potential to mimic or interfere
with normal hormonal functions of humans and animals. The present study aimed at
assessing the occurrence of these hormones in relation to the molecular diversity of
Aeromonas and evaluating the resistance of Aeromonas to antibiotics as well as to
assess anti-bacterial activity of two selected traditional medicinal plants.
Methods: Wastewater, water and fish samples were collected from various sources
(rivers, wastewater treatment plants, taps, and dams) for the detection of hormones
and isolation of Aeromonas species. The analysis of hormones from various organs
of the fish and from water samples was conducted, after extraction using enzymelinked
immunosorbent assays (ELISA). Different types of hormones including Estriol,
Estradiol, Ethinylesradiol and Testosterone were detected, and their concentrations
determined. Aeromonas spp were isolated rom the samples using microbiological
methods and Conventional PCR was used for genotyping as well as for detection of
the beta-lactamase genes. Kirby-bauer method was used to determine the
susceptibility profiles of Aeromonas to different antibiotics. Microdilution assay was
used to determine the Anti-bacterial activity of the plant (Annoniceae and Zornia
milneana) extracts against Aeromonas species.
Results: A total of 144 samples were collected from 23 different locations in two
countries: South Africa and Zambia. These included wastewater and treated
wastewater, River water, fish and tap water. 17α-ethinylestradiol (EE2) was detected
in most of the samples (92.7%) with concentrations varying from 0.59 ng/ml to 65
ng/ml. The hormones were also detected from drinking water, with testosterone
detected at high concentrations of up to 140 ng/ml in tap water. Most sewage treatment
plants were not able to remove the EE2 from the wastewater as the concentration of
this hormone in the final effluent was almost always higher than that in the influent.
These homones were also detected in drinking water at high concentrations of up to
53.49 ng/ml in the tap water for EE2 and 1777 ng/ml for E2. The overall detection of
Aeromonas species in the samples was 84.5%. A. caviae was the most prevalent
species accounting for 73.6%, followed by A. veronii with 64.6%. The bacteria were
completely resistant to cefuroxime accounting for 100% resistance. Aeromonas
isolates also showed high resistance to trimethroprim (88.7% for A. hydrophila),
cefazolin (highest 97.8% for A. cavie), and ceftazidime (83.9% for A. sobria). TEM was
the most prevalent beta-lactamase gene with detection rate of 87%. All isolates lacked
the presence of the CTX-M3 gene. Also, wastewater had the highest prevalence of A.
veronni and A. caviae accounting for 87.5% and 82.5% respectively. Multiple antibiotic
resistance was also observed with the Aeromonas isolates being resistant to up to 11
antibiotics. High prevalence of 77.1% of Aeromonas hydrophila was observed in the
presence of ethinylestradiol (EE2). Aeromonas veronii and Aeromonas caviae were
the most predominant species in the presence of total estriol, A. veronii had a
prevalence of 57.1% and A. caviae had a prevalence of 52.8%. Aeromonas hydrophila
and Aeromonas caviae had the lower prevalence in the presence of hormones with
the percentages of 26.1% and 27.8% respectively. The methanol extracts of both
Zornia milneana and Annona species showed good activity against the Aeromonas
spp with the lowest MIC of 0.078 mg/ml. Ethyl acetate extracts were the least effective.
Conclusion: This study has shown high occurrence of steroid hormones in all types
of environmental samples tested. These included tap water, river water, wastewater
and fish both in Zambia and South Africa. Therefore, steroid hormones constitute and
important health problem in the Southern African Sub-Region. The incapacity of the
wastewater treatment plants to remove EE2 is an important problem that needs to be
tackled immediately. The prevalence of Aeromonas species is very high in our
environmental water as well as in drinking water, with the highest prevalence observed
in fish and wastewater. It was also revealed that there is relationship between steroid
hormones and Aeromonas species, with the hormones supporting the growth of
Aeromonas species. The presence of beta-lactamase genes which causes
Aeromonas to be resistant to antibiotics was also noted. Methanol extracts of Zornia
milneana and Annona spp were the most effective against Aeromonas spp and could
serve as primary sources for the isolation of lead compounds. / NRF
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:univen/oai:univendspace.univen.ac.za:11602/1340 |
| Date | 18 May 2019 |
| Creators | Manavhela, Murendeni |
| Contributors | Samie, Amidou, Sichilima, Alfred |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | 1 online resource (xxiv, 179 leaves: color illustrations, color maps) |
| Rights | University of Venda |
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