Contamination Status of Salmonella spp., Shigella spp. and Campylobacter spp. in Surface and Groundwater of the Kelani River Basin, Sri Lanka

: Waterborne diseases are a global problem that causes more than 2.2 million deaths annually. Therefore, the present study was focused on microbiological contamination of both ground and surface water by means of total coliform, Escherichia coli ( E. coli ), Salmonella spp., Shigella spp. and Campylobacter spp. Seventy two groundwater and 45 surface water sampling locations were selected to collect water from the head, transitional and meandering regions of the Kelani River Basin for a period of one year (both dry and wet seasons). The results of the study revealed that the entire Kelani River basin was contaminated with total coliform and E. coli bacteria and almost all the sampling locations exceed Sri Lanka Standards Institute (SLSI) guideline value given for drinking water (0 CFU / 100 mL). Further, in groundwater, 17 locations were positive for Salmonella spp., whereas only 2 locations were positive for Campylobacter spp. In surface water, 26 and three sampling locations were positive for Salmonella spp. and Campylobacter spp., respectively. In this study, 23 di ﬀ erent human pathogenic serovars were isolated and the Salmonella enterica serovar Kentucky was identiﬁed as the commonest type. Thus, the result of the study revealed that the consumption of raw water from the Kelani River Basin is unsafe and possible to cause gastrointestinal diseases.


Introduction
Globally, since 1990, 2.3 billion people have gained access to improved sources of drinking water [1]. Recent World Health Organization (WHO) statistics have shown that 87% of the developing countries have access to safe drinking water, leaving 748 million people unable to access the luxury and the amount is largely regional specific [1]. A recent study discovered that nearly one billion people in the world still practice open defecation and this situation is severe in many developing countries with poor sanitation practices following discharge of approximately 95% of their untreated sewage directly into surface waters [2,3]. In Sri Lanka, total annual water resources (AWR) are 50 km 3 and only 20% is used in agriculture, industry and domestic purposes [4]. Sri Lanka comprises of 103 major river basins and the calculated total drain area is around 59,245 km 2 [5]. Among the river basins in Sri Lanka, Kelani River Basin plays a major role providing water for irrigation, recreation, agriculture, industry and drinking [6] flowing through the capital cities of the country and it is providing around 80% of head, transition and meandering zones in the Kelani River Basin (6.746 • -7.234 • N, 79.851 • -80.780 • E) (Figures 1 and 2).
according to the manufacture's instructions and prepared media was stored in the cold room at [4][5][6][7][8] 105 °C until analysis [21]. Sampling controls were used to identify, measure and control sources of 106 contamination or error that may be introduced from the time of sample collection through sample 107 analysis. Therefore, field and media blanks were subjected for data evaluation and authentication.    16 Kelani river (Yatiyanthota) 31 Pusseli Oya 2 Sami male canal 17 We oya (Amanawala) 32 Kelani river (Ranala) 3 Kehelgamu oya (Norwood) 18 Ritigaha oya (Warawala) 33 Pahala bomariya ela 4 Dic oya 19 Gurugoda oya 34 Raggahawaththa oya River Basin (Figures 1 and 2; Tables 1 and 2). River water samples were collected from the river 100 banks and middle of the river where reachable to collect. In total, 2.5 liters of water sample was 101 collected to pre-cleaned sterilized amber color glass bottles with the help of sampling iron and 102 transported to the laboratory in an ice box and kept in a cold room (4-8 °C). Microbiological analysis 103 was performed within 24 hours of sample collection. Media preparation and sterilization were done 104 according to the manufacture's instructions and prepared media was stored in the cold room at [4][5][6][7][8] 105 °C until analysis [21]. Sampling controls were used to identify, measure and control sources of 106 contamination or error that may be introduced from the time of sample collection through sample 107 analysis. Therefore, field and media blanks were subjected for data evaluation and authentication.

Water Sampling
Sampling was conducted in both dry (February-March 2015) and wet (May-June 2015) seasons for 45 surface and 72 groundwater sampling locations (one sample from each location) in the Kelani River Basin (Figures 1 and 2; Tables 1 and 2). River water samples were collected from the river banks and middle of the river where reachable to collect. In total, 2.5 liters of water sample was collected to pre-cleaned sterilized amber color glass bottles with the help of sampling iron and transported to the laboratory in an ice box and kept in a cold room (4-8 • C). Microbiological analysis was performed within 24 hours of sample collection. Media preparation and sterilization were done according to the manufacture's instructions and prepared media was stored in the cold room at 4-8 • C until analysis [21]. Sampling controls were used to identify, measure and control sources of contamination or error that may be introduced from the time of sample collection through sample analysis. Therefore, field and media blanks were subjected for data evaluation and authentication.

Isolation and Identification of Pathogenic Bacteria
To enumerate of E. coli and coliform bacteria (Membrane Filtration method) 100 mL of the sample was filtered through 0.45 µm cellulose acetate membrane filter (Whatman Cat No: 7001 0004, D-47mm) using a manifold system (Elements, Australia, Reg DES 85628). The filter membrane was kept on the Membrane Lactose Glucuronide Agar (MLGA) plate and incubated at 37 ± 1 • C for 22 ± 2 h (Sri Lanka Standards Institution, 2013). For Salmonella and Shigella identification, Salmonella typhi and Shigella sonnei were used as positive controls obtained from the Medical Research Institute (MRI) Sri Lanka. The strains were maintained on nutrient agar (Oxoid CM003) slants under cold room condition at 4-8 • C. Buffered peptone water (BPW) (Oxoid CM0509) was used as primary enrichment for both Salmonella spp. and Shigella spp. One liter of water samples was filtered through 0.45 µm cellulose acetate membrane filter (Whatman Cat No: 7001 0004, D-47 mm) and the filter was dipped in sterile 90 mL buffered peptone water and incubated at 37 • C for 18 ± 2 hours. After incubation enriched broth (BPW) was inoculated to selective enrichment media. In total, 0.1 mL of enrichment broth into 10 mL of Rappaport Vassiliadis soya peptone broth (RVS) (Oxoid CM0866) and incubated at 41.5 • C for 24 ± 3 h and then 1 mL of enrichment broth was inoculated into 10 mL of Selenite cystine broth, (SCB) (Oxoid CM0395 and LP0121) and incubated at 37 • C for 24 ± 3 h. After the selective enrichment, colonies appeared on the disk was isolated onto Salmonella-Shigella agar (SSA) (Oxoid CM0533) and Xylose lysine deoxycholate agar (XLD) (Oxoid CM0469) following incubation at 37 • C for 24 ± 3 h. Suspected colonies of Salmonella spp. and Shigella spp. were identified based on colony appearances and the suspected colonies of Salmonella spp. and Shigella spp. were further subjected to the biochemical tests (Kligler iron agar, indole, urease, lysine decarboxylase, motility test) for confirmation [22][23][24].
Campylobacter jejuni sub sp. Jejuni (ATCC 33560) obtained from the Medical Research Institute (MRI) Sri Lanka and used as a positive control to evaluate presence Campylobacter spp. The strains were maintained on tryptose blood agar (Oxoid CM233) containing 10% (v/v) fresh sheep blood at 37 • C in the anaerobic jar with micro aerobic conditions created using Oxoid Gas Pack (CAMPYGEN CN0035). Bolton and Preston broths were used for the enrichment of the bacteria. Bolton broth (Oxoid SR183E and CM0983) and Preston (LAB 014, LAB M X114 and LAB M X115) enrichment broths were supplemented with 5% (v/v) fresh sheep blood (Medical Research Institute). One liter of water sample was filtered through 0.22 µm filter paper (Whatman Ltd, Japan, Cat No: 70010004, D-47 mm) and the filter disk was dipped in the sterile Preston/Bolton broth which contained 90 mL of broth in 100 mL glass bottles. Bolton broth contained sample was incubated at 37 • C for 44 ± 4 h while Preston broth contained sample was kept in the Incubator (EYELA, Japan, SLI-1000D) at 37 ± 1 • C for 22 ± 2 h and then kept at 41.5 ± 1 • C for further 22 ± 2 h. After 44 ± 4 h of incubation, a loop (10 µL) of bacterial was streaked on modified blood-free charcoal cefoperazone deoxycholate agar (mCCDA) (LAB 112) with selective supplement (LAB M X112) and then kept in the anaerobic jar (TOMY, SEIKO. Co. Ltd., Tokyo, Japan) with campy pack, (CAMPYGEN, Oxoid, CN0035) incubated at 41.5 • C for 44 ± 4 h under micro-aerobic condition [25]. Suspected colonies of Campylobacter spp. were identified following colony appearances. Further identification of suspected colonies of Campylobacter spp. was performed by gram staining and oxidase test.

Serotype Identification-Serological Identification Method
For serotype identification, isolated Salmonella spp. samples were sent to WHO National Salmonella and Shigella Center, Thailand.

Statistical Analysis
Data set was processed using Minitab version 15 statistical software. Two-way ANOVA and Pearson correlation tests were carried out for microbiological parameters for both ground and surface water sampling locations.

GIS Thematic Mapping
Collected data on microbiological parameters in the entire Kelani river basin were stored in a geographic information system (GIS) database. These data were digitized with a Sri Lanka survey department digital map created in 1999 at 1:50,000 scale. The inverse distance weighted interpolation (IDW) under spatial analyst tool in the ArcGIS 10.0 software was employed for the interpretation of data.

Results and Discussion
Water borne diseases due to various types of pathogenic bacteria, viruses and protozoa were recorded in many parts of the world and the majority of cases have been recorded from developing countries [26]. WHO and UNICEF (2014) reported that 4000 annual child deaths in some developing countries in the world due to consumption of contaminated surface and groundwater without proper treatment. Mahagamage and Manage [27] documented that the majority of respondents in head and transitional regions in the Kelani River Basin consumed spring water for their day to day activities such as drinking, bathing, cooking and washing. Specially, central highlands are rich in spring waters and most of the people who live in hilly regions depend on their own spring near homeland or public water schemes which supply water from spring sources. However, people live in the meandering region mainly depend on well water and treated-water, which is provided by National Water Supply and Drainage Board (NWSDB) where several intakes in the Kelani River Basin including Ambathale, Biyagama, Labugama tank and Kalatuwawa tank.
The results of the study revealed that almost all surface and groundwater samples collected were contaminated with total coliform and E. coli bacteria. In total, 83% of drinking groundwater sources recorded greater than 200 CFU (100 mL) of total coliform (TC) where 28% contaminated with E. coli, during the dry season ( Figure 3) following 83% and 25% TC and E. coli contamination during wet season (Figure 4). It was detected that E. coli contamination in surface water was high during the wet season compare to dry season ( Figure 4). Improper sanitary facilities, inadequate draining of wastewater and sewage, inefficient sewage and waste management, land use application of the fertilizer mix with sewage and contamination of groundwater due to toilet pits are major pathways of contamination of ground and surface water with faecal microorganisms in the Kelani River Basin.         Salmonella, Campylobacter and Shigella are common pathogenic bacteria find in the environment where sanitation is poor, since they are excreted by faeces of humans, farm animals and wild animals [26]. Salmonella cause salmonellosis, gastroenteritis, typhoid fever while Campylobacter cause Guillain-Barré syndrome and Shigella spp. causes shigellosis due to consumption of pathogenic contaminated water [19]. Numerous studies have shown that microbial pathogens, such as Salmonella and E. coli are relatively stable in groundwater [28][29][30] and surface water [31][32][33][34] and the contamination prevalence depends upon the vulnerability of water sources to anthropological activities such as bathing, washing and defecating [33,34]. The results of the study showed the occurrence of Salmonella and Campylobacter in some ground and surface water sources which may alarm possible root causes of susceptibility of gastrointestinal disease of people who consume contaminated water.
Among the other river basins in the Sri Lanka, the Kelani River Basin is the most urbanized and industrialized river basin and it has polluted by various point and non-point sources of pathogenic contaminates via municipal sewage and agricultural pollutants. Improper and poorly managed draining systems of wastewater and sewage into the environment and accidental sewage contamination of groundwater are the major pathways of contamination of aquifers by pathogenic or facultative pathogenic microorganisms [35]. In the present study, it was discovered that seventeen groundwater sampling locations were positive for Salmonella spp. where, two locations were positive for Campylobacter spp. (Table 3) and none of the locations were positive for Shigella contamination. Curiously, out of forty-five surface water sampling locations, twenty six sampling locations were contaminated with Salmonella spp. where only three locations were positive for Campylobacter spp. (Table 4). Further, it should be noted that 41% of the Salmonella spp. and Campylobacter spp. contaminated water sources are being directly used for drinking and other human consumption. Moreover, 23 types of different human pathogenic Salmonella serovars were isolated during the study and the Salmonella enterica serovar Kentucky was identified as the commonest. All the recorded serovars are human pathogens responsible to cause salmonellosis, gastroenteritis, typhoid fever and many more health impacts. Thus, awareness and provide safe drinking water is a must to safeguard people who consume such water sources in the river basin to prevent gastrointestinal diseases.  The occurrence of Salmonella enterica serovar Kentucky in the environment is rare [36]. However, in the present study, three groundwater sampling locations were positive for Salmonella serovar Kentucky in both dry and wet seasons (Table 3). Barua et al. [37], Fashae and Hendriksen [38] and Afema et al. [39] isolated Salmonella enterica serovar Kentucky from farm animals. Therefore, the leachate of farm effluent to the river basin might be a possible point source of such pathogens. In the present study, Moragahahena well, which is situated close to poultry and swine farm positive for Salmonella enterica serovar Kentucky. In surface water, four sampling locations namely, Nallathanniya, Getaheththa tributary, Wellampitiya and Kalu oya were positive for Salmonella enterica serovar Kentucky during dry season (Table 4). Further, it was found that Nallathanniya location was highly contaminated during the Sri pada season (religious festival season from December to May) due to poor sanitary conditions provided for pilgrims during the Sri-pada season [40]. Wellampitiya (Kiththampahuwa oya) and Kalu oya are the major drainage canals connected with KRB and these sampling locations were located in urban and industrial part of the basin. These drainage canals are open for sewage canals from some areas around. Hellole et al. [41] documented that Salmonella enterica serovar Kentucky contamination occurs through septic or direct connect of toilets into the main river. During the wet season, three sampling locations were positive for Salmonella enterica serovar Kentucky (Table 4) and out of three locations, Thalduwa (Seethawaka oya) and Eswaththa oya were used for bathing and washing purposes. Therefore, awareness and preventive measures should be taken to avoid pathogenic contamination in the KRB.
In the last two decades, Salmonella enterica serovar Weltevreden has appeared as a dominant foodborne pathogen globally; especially in South-East Asian countries, being increasingly isolated from water, vegetables, meat and seafoods [42][43][44]. In the present study, Salmonella enterica serovar Weltevreden was detected in two groundwater sampling locations (Table 3). Dias et al. [45] reported that coliform bacterial contamination was high in surface water of the head region of the Kelani River Basin due to human settlement with lower sanitary facilities. Alagal Oya (Gonagamuwa) location situated in the head region of the river basin which was heavily used for recreational purposes and contamination of Salmonella is possible (Table 4).
Ezekwe et al. [46] stated that groundwater sources in Nigeria used for drinking purposes are extremely polluted, especially in urban cities due to on-site sanitation systems such as septic tanks, pits and bucket latrines. The present study recorded S. enterica serotype Poona from groundwater sampling location located in Hingurala nearby toilet pits during the dry season (Table 3). Further, it was found that S. enterica serovar Newport during the wet season and this serovar has been recorded as a common causative agent for human salmonellosis in the United States and Europe [47]. Some studies have reported that the development of multidrug-resistant against Salmonella serotype Newport is spreading on an epidemic scale in both animals and humans [48] (Table 3).
Salmonella enterica serovar Typhimurium, are host generalists that occur in humans and many other mammalian species [49]. In the present study, Nawagampura and Badupola groundwater sampling locations were positive for pathogenic Salmonella enterica serovar Typhimurium (Table 3). Rop [50] documented that the causes of anthropological activities such as bathing and washing mainly contribute to the dispersal of pathogenic bacteria. During the study it was found that public and unprotected wells used for domestic consumption were polluted with Salmonella spp. Søborg et al. [51] reported that roadside soil can be contaminated with Salmonella spp. and it is possible to leach contaminated water into wells. Badupola groundwater location is being used for drinking purposes which is located close to the roadside and it was possible to get runoff water through the road to contaminate the groundwater. During the dry season of the study, Salmonella enterica serovar Typhimurium was isolated from four locations of the surface water (Table 4) and Vidulipura tributary which flows through estate sector is vulnerable to receive polluted water by sewage and toilet pits in the area due to poor sanitation facilities in the area. Further, Polo et al. [52] recorded that contamination of pathogenic bacteria may occur in surface water due to human activities. In the study, it was found that the Alagal Oya and Eswaththa oya are contaminated with Salmonella enterica serovar Typhimurium and such tributaries are being used for bathing and washing purposes. Raggahawaththa oya was highly polluted tributary in the river basin which flows through Biyagama industrial zone and the water source was contaminated with Salmonella enterica serovar Typhimurium. As per mentioned by Baudart et al. [53] Salmonella enterica serovar Typhimurium can tolerate a wide range of physico-chemical ranges in effluent water.
The genus Salmonella consists of two species, S. enterica, which is divided into six subspecies [54] and S. enterica subsp. diarizonae is one of the sub species whose occurrence in the environmental samples and outbreaks due to the species was less than other Salmonella spp. However, S. enterica subsp. diarizonae are naturally found in reptiles [55]. The results of the present study showed that some sampling locations were positive for this Salmonella spp. (Table 3). It was found that the Kandura (Koththellena) sampling location which was highly used for bathing was positive for S. enterica subsp. diarizonae during dry and wet seasons (Table 4).
Salmonella enterica serovar Angoda is a new Salmonella spp. recorded from Sri Lanka by Gulasekharam [56]. Thereafter, this species was reported in some locations of the world from different outbreaks [57]. In the present study, Levent location situated in the head region was positive for Salmonella enterica serovar Angoda (Table 3). Abrahams et al. [58] and Waithaka [59] described that high numbers of Salmonella were detected from the intestine of the ruminants and this may be a fact for contamination in Lavent location which was a rubber cultivating area with goats.
Nordmann et al. [60] documented of a Salmonella enterica serovar Waycross outbreak from Australia and a patient had a urinary tract infection in several years due to a Salmonella species. Salmonella enterica serovar Waycross is not a common bacterium for food and waterborne diseases and it was recorded from a Viharakumbura sampling location in the present study (Table 3).
Salmonella enterica subsp. enterica serovar Mbandaka was firstly isolated from human salmonellosis in the Congo in 1948 and it was ranked amongst the 20 most frequent serovars in humans in European countries and continents [61]. In the present study, Arangala location was positive for Salmonella Mbandaka (Table 3).
Dolman et al. [62] discovered the Salmonella enterica serovar Vancouver from the patient with high fever, vomiting and diarrhea and a few outbreaks were recorded worldwide. In the present study same species were recorded at Kannampella sampling location which was used as a public well and bacterial contamination is possible due to bathing and washing activities (Table 3).
Non-typhoidal Salmonella serovars are increasing in importance as significant pathogens of both humans and animals. Ben and AL-Gallas [63] documented that most commonly isolated Salmonella in Tunisia was Salmonella enterica serovars Corvallis. During the present study, Salmonella enterica serovars Corvallis was recorded from a Kambulumulla groundwater sampling location (Table 3) which is used for drinking purposes.
Moreover, enteric fever remains to be a public health problem in many parts of the world, especially in the developing countries including Sri Lanka. Enteric fever (i.e., Typhoid and paratyphoid fever) is a systemic disease resulting from infection with Salmonella enterica subsp. enterica serotype Typhi and Salmonella enterica subsp. enterica serotype Paratyphi A, B or C. Further, enteric fever is typically caused by consumption of food or water that has been contaminated by these pathogens and asymptomatic carriers, particularly food handlers who are the major source of these organisms [64]. Recent reports have documented that increased incidence of Salmonella enterica subsp. enterica Paratyphi B in Canada-Stratton et al. [65], Germany-Miko et al. [66], Italy-Mammina et al. [67] and Malaysia-Goh et al. [68]. Levings et al. [69] and Hernández et al. [70] recorded that fish and reptiles are a source of contamination of Salmonella enterica serovar Paratyphi B. However, Salmonella enterica serovar Paratyphi B Variety Java is a non-typhoidal strain of Salmonella, which causes gastroenteritis was recorded from four sampling locations (Pugoda river, Kelani River (Thaligama), Pusselli oya and Raggahawatta oya) during the study period.
Salmonella enterica serovar Bareilly was initially identified from India in 1928 [71] and it is known for its wide host range [72]. Some strains are clonal and can be detected in numerous sites throughout Southeast Asia and are given potential reservoirs associated with Salmonella Bareilly that include reptiles and other environmental sources [73]. Hoffmann et al. [74] documented that Sri Lanka is contaminated by this particular Salmonella serovar from India or Pakistan and imported food from other South Asian countries. The Gurugoda oya location was positive for Salmonella Bareilly and it is used for recreational, irrigation and livestock purposes ( Table 4). As per mentioned by WHO [75] water bodies used for irrigation and livestock purposes can easily be contaminated with Salmonella spp.
Sampling locations of Thalangama Lake and Diyawanna oya where stagnant water bodies directly receive several household drainage systems and agricultural effluent (Table 4). It was found that Diyawanna oya location was positive for Salmonella Litchfield during the dry season and Thalangama Lake was positive for Salmonella Manchester (Table 4). Polo et al. [52] documented that Salmonella is commonly present in sewage effluent that can contaminate recreational waters.
Keselgamu oya (Tientsin) was positive for Salmonella enterica subsp. enterica serovar Javiana (Table 4) and it is one of the top five most common serotypes of Salmonella and is a common food-borne pathogen [76].
Salmonella enterica serovar Stanley (S. Stanley) is a common serovar in Southeast Asia and in contrast, this serovar is relatively uncommon in Europe [77]. Due to international travel, human migration and food and livestock trade, Salmonella serovar Stanley was the second most common serovar in Thailand, accounting for 11% of all human salmonellosis cases from 2002 to 2007 [78]. The results of the study revealed that Sebastian canal (Kelanithissa) was positive for S. Stanley during the dry season of river basin (Table 4).
Salmonella enterica subsp indica is usually found in poikilotherms (including reptiles, amphibians and fish) and in the environment. Some of these organisms are occasionally associated with human diseases [79]. Interestingly, limited information is recorded for this Salmonella spp. and only Bangalawaththa sampling point was positive for Salmonella enterica subsp indica (Table 3).
Raggahawaththa oya (Meegawaththa) was positive for Salmonella Newport, Salmonella enterica serovar Weltevreden and Salmonella enterica serovar Paratyphi B Variety Java (Table 4). Further, Mahara and Sebastian canal sampling locations were positive for Salmonella spp. during the study period (Table 4). WHO [75] reported that the industrial and drainage water contains Salmonella spp. and it is possible to pollute other water sources of the environment. In the Sri Lankan context, most of the drainage canals were directly connected with some sewage canals from industries and commercial places. Therefore, the occurrence of pathogenic Salmonella is possible in surface water sources.
Campylobacter spp. has obtained considerable attention in the recent years as a significant cause of bacterial enteritis in humans. During the last couple of decades, Campylobacter jejuni and Campylobacter coli have been recognized as a common cause of gastroenteritis worldwide. Kelaniya and Ginigathhena groundwater sampling locations were positive for Campylobacter spp. during dry season (Table 3). Further, three surface water sampling locations were positive during the dry season and two were positive in wet season, including Hamilton canal which is a major drainage connect with several sewage canals (Table 4). However, Premarathne et al. [80] recorded that the favored environmental place for Campylobacter spp. is to be the intestinal tract of most of birds and mammals; Ugarte-Ruiz et al. [81] recorded that survival of Campylobacter spp. in surface water for a higher recovery of the organism in wide range of water quality changes. Medema et al. [82] documented similar results on Campylobacter spp. contamination in waters and reported contamination may have caused due to animals and faecal contamination of the catchment area with drainage directed into water sources.
However, it should highlight that no Shigella spp. positive sampling locations were recorded for both the ground and surface water in the Kelani River Basin during the study period.
According to Pearson correlation, a significant correlation was observed in TC and E. coli with Salmonella spp. Further, it was revealed that negative correlation of TC and E. coli with Pseudomonas spp. (Table 5). Two-way ANOVA revealed that there was no significant difference (p > 0.05) in two seasons for all microbial parameters and only TC and E. coli showed significant difference (p < 0.05) with groundwater sampling locations. In addition, Two-way ANOVA for surface water revealed that there was significant difference in two seasons for E. coli where Pseudomonas spp. Cam1ylobacter sp. and E. coli showed significant differences with surface water sampling locations.

Conclusions
The entire Kelani River Basin was contaminated with total coliform and E. coli bacteria and almost all the sampling locations exceed the standard value 0 CFU/100 mL) given by the SLS guideline for drinking water. High density of human population and poor sanitary conditions were identified as a major reason for contamination of high total coliform and E. coli bacteria in surface and groundwater of the head and meandering regions of the river basin. Identification of human pathogenic bacteria showed that seventeen locations of groundwater sources were positive for Salmonella spp. and only two locations were positive for Campylobacter spp. In surface water, twenty-six sampling locations were positive for Salmonella spp. and three sampling locations were positive for Campylobacter spp. It was found that, Salmonella spp. contamination in surface water was high during the wet season (42%) than the dry season (33%). In groundwater, Salmonella spp. contamination was higher during the dry season (17%) than the wet season (8%). Further, 23 types of different serovars were isolated during the study period where Salmonella enterica serovar Kentucky was the most common and all the serovars recorded were human pathogenic species which cause salmonellosis, gastroenteritis and typhoid fever. Interestingly, Shigella spp. was not recorded in either dry or wet season during the study period in both ground and surface water. The result of the study revealed that people and stakeholders within the premises of the river basin should be aware of both ground and surface water quality of the river basin.