Drinking water quality along the distribution network and associated antibiotic resistance in Maun, Botswana

Maintaining the water quality in the distribution system is crucial to supplying safe drinking

water to consumers. The main aim of the study was to analyse physicochemical, bacteriological

parameters and investigate prevalence of antibiotic resistant bacteria and their antibiotic

resistance genes in the drinking water distribution system in Maun, Botswana. Forty-four water

samples were collected at different season interval and were tested for chlorine and turbidity and

the results showed that in May, September, January and March, turbidity and chlorine measured

1.0 NTU (0.2 mg/L), 1.1 NTU (0.5 mg/L), 1.0 NTU (0.2 mg/L), 2.7 NTU (0.1 mg/L)

respectively. The indicator organisms recorded were heterotrophic bacteria (37.7 %), total

coliforms (28 %), Faecal streptococci (18.9 %) while Escherichia coli was at 10.4 % and 5 %

for unusual isolates. Antibiotic susceptibility tests were performed on 150 isolates, which were

tested against 15 different antibiotics using the Kirby-Bauer diffusion test. Ninety-two percent of

the isolates were susceptible to at least one antibiotic and only one isolate (121-S5; E. coli)

showed resistance to all the antibiotics used. For multi-drug resistance (MAR) patterns, the most

prevalent antibiotic resistance pattern observed was AMP-AML-MEL-C-W-RD-TET-PENSTREP.

In addition, 92 % of the isolates were susceptible to meropenem followed by gentamicin

(88 %) and ciprofloxacin (81 %). The amplified 16S rDNA sequences were successfully used to

identify the 10 selected isolates. The presence of targeted ARGs (tetA, tetB, int1, strepB and

sul1) for both culture isolates and whole sample genome were established. Moreover,

metagenomic analysis confirmed the presence of some pathogenic bacteria such as

Mycobacterium tuberculosis, Legonillela sp, Cholera sp, Staphylococcus sp, Sphingosinicella sp.

and Pseudomonas sp. In conclusion, the results indicated the occurrence of indicator bacteria and

other non-culturable species in the drinking water as the water moves from the treatment plant to

lines that feed the consumers. The results also signified the presence of antibiotic resistant

bacteria and their resistance genes in the water samples. The data obtained may be thereof useful

in monitoring the integrity of the water quality in the distribution network after treatment.