The main aim of the study was to analyse the impact of physico-chemical
parameters on drinking water quality, biofilm formation and antibiotic resistant
bacteria in the drinking water distribution system in Mafikeng, North West Province,
South Africa. Another objective was to isolate and characterise Pseudomonas and
Aeromonas species from drinking water distribution system and detect the virulence
gene determinants in the isolates by PCR analysis. The physico-chemical data
obtained were subjected to statistical analysis using Excel 2007 (Microsoft) and
SPSS (version 14.0) programmes. Pearson’s correlation product of the moment was
used to determine the correlation between EC, TDS, pH and temperature. The two
tailed test of significance (p<0.05) was used in order to determine the significance of
the result. Antibiotic susceptibility tests were performed using Kirby-Bauer disk
diffusion method. Cluster analysis based on the antibiotic inhibition zone diameter
data of different organisms isolated from different sites was determined and was
expressed as dendograms using Wards algorithm and Euclidean distance of
Statistica version 7. Specific PCR was used to determine the identities of
presumptive Pseudomonas and Aeromonas species through amplification of the
gyrB, toxA and the ecfX gene fragments. Virulence gene determinants for the
confirmed Pseudomonas and Aeromonas species were detected by amplifying the
exoA, exoS and exoT genes and the aerA and hylH gene fragments, respectively. A
Gene Genius Bio imaging system (Syngene, Synoptics; UK) was used to capture the
image using GeneSnap (version 3.07.01) software (Syngene, Synoptics; UK) to
determine the relative size of amplicons.
Physico-chemical parameters were monitored from three drinking water sources
three times a week and bacteriological quality was monitored weekly for four months
from raw and treated drinking water. Water samples were analysed for pH,
temperature, total dissolved solids (TDS) and electric conductivity (EC). Bacterial
consortia from drinking water samples were isolated using selective media and
enumerated. The results revealed a good chemical quality of water. However, the
microbial quality of the water is not acceptable for human consumption due to the
presence of Pseudomonas, Aeromonas, faecal coliforms (FC), total coliforms (TC)
and Heterotrophic bacteria. The results showed that the drinking water is slightly
alkaline with pH value ranging between7.7 to 8.32. What is of concern was the
microbial quality of the water. Pseudomonas sp., faecal coliforms (FC), total
coliforms (TC) and heterotrophic bacteria were present in some of the treated water
samples. The most significant finding of this study is that all drinking water samples
were positive for Pseudomonas sp.(>100/100ml), but also that when one considers
the TDS it demonstrates that water from the Modimola Dam has an impact on the
quality of the mixed water.
The prevalence and antibiotic resistance profiles of planktonic and biofilm bacteria
isolated from drinking water were determined. The susceptibility of these isolates
was tested against 11 antibiotics of clinical interest and the multiple antibiotic
resistance (MAR) patterns were compiled. The most prevalent antibiotic resistance
phenotype observed was KF-AP-C-E-OT-K-TM-A. All isolates from all samples were
susceptible to ciprofloxacin. However, all faecal coliforms and Pseudomonas spp.
were susceptible to neomycin and streptomycin. On the contrary all organisms
tested were resistant to erythromycin (100%) trimethoprim and amoxycillin. Cluster
analysis based on inhibition zone diameter data could not differentiate the various
isolated into sample types. The highest prevalence of antibiotic resistant isolates was
observed in Modimola Dam and Molopo eye.
Biofilms were investigated in both raw water and treated drinking water sources for
the presence of faecal coliforms, total coliforms, Pseudomonas spp., Aeromonas
spp. and heterotrophic bacteria based on conventional microbiology and molecular
methods. Drinking water biofilms were grown twice and the biofilm developing device
containing copper and galvanized steel coupons were utilized.
The Mini Tap filter, a home water treatment device which can be used at a single
faucet, under constant flow was used during the second collection of treated water
samples from cold water taps. Scanning electron micrograph revealed the existence
of biofilms in all the sites investigated and the highest density was obtained on
galvanized steel coupons.
Isolates were tested against the antibiotics ampicillin (10μg), cephalothin (5μg),
streptomycin (10μg), erythromycin (15μg), chloramphenicol (30μg), neomycin (30
μg), amoxycillin (10 μg), ciprofloxacin (5 μg), trimethoprim (25μg), kanamycin (30μg),
and oxytetracycline (30μg). The multiple antibiotic resistance profiles and the
presence of virulence related genes were determined. Various types of drug
resistance and presence of virulence genes were observed. The most prevalent
resistance phenotype observed was KF-AP-C-E-OT-TM-A.
In conclusion, the results indicated the occurrence of faecal indicator bacteria in the
drinking water destined for human consumption. Faecal indicator bacteria are the
major contributors of poor drinking water quality and may harbour opportunistic
pathogens. This highlighted survival of organisms to treatment procedures and the
possible regrowth as biofilms in plumbing materials. The detection of large proportion
of MAR Aeromonas and Pseudomonas species which possessed virulent genes was
a cause of concern as these could pose health risks to humans. The data obtained
herein may be useful in assessing the health risks associated with the consumption
of contaminated water. / PhD (Microbiology), North-West University, Potchefstroom Campus, 2014
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/15452 |
| Date | January 2014 |
| Creators | Mulamattathil, Suma George |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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