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A cross-sectional epidemiological method was adopted to investigate the four main urban …

Biology Articles » Hydrobiology » Bacteriological assessment of urban water sources in Khamis Mushait Governorate, southwestern Saudi Arabia » Results and discussion

Results and discussion
- Bacteriological assessment of urban water sources in Khamis Mushait Governorate, southwestern Saudi Arabia

Data recorded in Figure 1 indicated that total coliforms were not detected in any sample taken from bottled water. In the desalinated water, surface water, and well water, total coliforms were detected with percentages of 12.9, 80, and 100.0, respectively. However, log counts of total coliform bacteria (MPN/100 ml) in desalinated, surface, and well water were 0.0–1.60, 0.0-≥ 4.38, and 1.60-≥4.38, respectively. The log mean values were 3.79 ± 3.40 and 3.86 ± 3.22 (MPN/100 ml) in samples taken from surface and well water, respectively. In previous studies, total coliform bacteria were detected in different water sources with various mean values and percentages [28,31,23,33,34]. There was no significant correlation in the level of total coliforms between well and surface water. As previously cited, total coliform counts must not be detected in any 100 ml water samples [35,17,24,11]. Therefore, results of total coliforms recorded in the present study showed that all examined samples from wells (100.00%) and most surface water (80.00%) exceeded the guideline values recommended in accordance with international standards [3,17,24].

The most common group of indicator organisms used in water quality monitoring are coliforms. These organisms are representative of bacteria normally present in the intestinal tract of mammals including human, so they provide a general, albeit adequate, index of faecal contamination of drinking water [36,24,26,38]. Moreover, the presence of coliforms in drinking water could also indicate a breakdown of the treatment process [28]. The transportation of desalinated water by tanker does not contribute significantly. Such contamination obviously occurs during storage in the house reservoir (earth) and is possibly implicated, at least partly, in the increased prevalence of diarrhoea [23].

From the results recorded in Figure 2, it is evident that faecal coliforms were not detected in any samples taken from bottled water, while from desalinated water, only one out of 31 (3.23%) samples was found positive for faecal coliforms. However, 9 out of 15 (60.0%) and 29 out of 33 (87.88%) specimens were found positive for faecal coliforms in samples taken from surface and well water, respectively. The log counts of faecal coliforms (MPN/100 ml) ranged from 0.0 to 1.6; 0.0 to ≥ 4.38 and 0.0 to ≥ 4.38 in desalinated, surface, and well water, respectively. Logarithmic mean values (MPN/100 ml) were 3.47 ± 3.23 and 3.40 ± 3.08 in surface and well water, respectively. There was no significant correlation in the level of faecal coliforms between well and surface water. These results indicated that most samples taken from wells (87.88%) and surface water (60.00%) had higher faecal coliforms with respect to the international guideline value, in which drinking water must be free from faecal coliforms [22,17,24,11,26,9]. Different coliform counts were previously recorded in groundwater samples [28,31,23,39,40].

Indicators such as faecal coliforms are not the best, because their effectiveness will be minimised in geographical zones when the temperature is high [41,26,42]. However, well water is at risk of contamination, as indicated by the presence of faecal coliforms [43,24,5,7,11,44,20].

It is evident from Figure 3 that faecal streptococci were not detected in any samples taken from bottled water. Two out of 31 (6.45%) desalinated water samples, 8 out of 15 (53.33%) surface water samples, and 19 out of 33 (57.58%) well water samples were found positive for faecal streptococci. Logarithmic range values of faecal streptococci (MPN/100 ml), however, were 0.0–1.6, 0.0–2.18, and 0.00–3.38 in samples taken from desalinated, surface, and well water, respectively. The log mean values of faecal streptococci (MPN/100 ml) were 1.65 ± 1.07 and 2.28 ± 1.97 in surface and desalinated water. There was a significant correlation at p = 0.05 in the level of faecal streptococci between surface and well water. With regard to international guideline values, in which water must be free from faecal streptococci, 6.45% of the desalinated water, 53.33% of the surface water, and 57.58% of the well water was considered to be unfit for drinking purposes. Faecal streptococci were previously isolated with various frequencies [28,31,33]. Enterococcus species were formerly classified in the genus streptococci. They are primarily commensurate with residence in the intestine, though some also cause gastroenteritis, nosocomial infection, endocarditis, intra-abdominal infection, surgical wound infection, and urinary tract infections [45,46,19,17,24,11].

As regards the bacteriological examination of water sources carried out in this study, high total coliforms, faecal coliforms, and faecal streptococci in surface and most well water are considered an indication of recent faecal pollution from human or animal excreta, which may reflect the possibility of potential health hazards [42]. The primary risk of consuming untreated water is the transmission of communicable diseases by pathogenic organisms. Those present in aquatic environments can be of natural origin or may be discharged by humans and other warm-blooded animals. However, the water, which is not suitable for drinking, may be usable for irrigation or for other domestic purposes. Thus, it can be seen that each use of water imposes its own limits on the degree of pollution that can be considered acceptable [1,17,24]. Drinking only from desalinated water sources was associated with diarrhoea as compared with drinking only from bottled water or from any other sources [23]. Water from the valleys and wells of the study area was grossly polluted and was used regularly for purposes other than drinking [23,5-7].

The coliform group comprises strains of the four genera of the intestinal group: Escherichia, Enterobacter, Klebsiella, and Citrobacter. The number of Escherichia and Enterobacter remains much higher in the intestine than do the remaining two [1,26,9].

The frequency distribution of the different microorganisms isolated from the examined samples is given in Table 1. A total of 114 isolated bacteria included 10 from desalinated water, 45 from surface water, and 59 from wells. These were typed to be 23 Escherichia coli (E. coli), 13 Klebsiella pneumonia, 7 Klebsiella oxytoca, 20 Enterobacter cloacae, 6 Eenterobacter aerogens, 7 Eenterobacter agglomerans, 3 Enterobacter gergoviae, 10 Citrobacter freundii, 8 Citrobacter diversus, 12 Proteus vulgaris, and 5 Proteus mirabilis, with percentages of 20.18, 11.40, 6.14, 17.54, 5.26, 6.14, 2.63, 8.77, 7.02, 10.52, and 4.39, respectively. Most of these bacterial species had been previously isolated from different water sources, although their percentages varied [47,27,31,40,11].

It is clear that out of all possibilities, E. coli can best fulfil conditions possible to act as an ideal indicator of faecal pollution. These organisms survive longer in water than most pathogens, and thus can detect recent as well as earlier pollution. In terms of public health significance, E. coli has frequently been reported to be the causative agent of traveller's diarrhoea, urinary tract infection, haemorrhagic colitis, and haemolytic uraemia syndrome. Moreover, Klebsiella pneumonia is associated with pneumonia and upper respiratory tract infection. However, Enterobacter and Citrobacter species have also been previously reported as causes of cystitis, enteritis, pneumonia, diarrhoea, and food poisoning [48,17,24,11]. Proteus species are apparently of epidemiological importance in summer diarrhoea in infants and in food-borne outbreaks. Proteus vulgaris in association with other bacteria has been reported to be the causative agent of cystitis and pyelitis [48,25,17,24,11].

Based on the above assessments, although bottled water may be of good quality in the Khamis Mushait Governorate urban area, the public supply of both desalinated water distributed via an urban water network system to areas of city quarters and conventional water sources such as wells and surface water cannot be ignored by local water authorities. They should consider a proper regular monitoring programme (i.e. wells and surface water microbial source tracking system) to determine the primary sources of contamination, their contribution, health threat, and geographic distribution. In addition, they ought to make recommendations and to develop appropriate control measures to avoid any sudden public health risk from such a vital water source [23,11].

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