Abstract

Drinking water from hand-pump-fitted borehole sources is considered as safe and suitable for human use due to a purification property of the soil. However, the water from these sources can be contaminated as a result of inadequate treatment and waste disposal from humans and livestock. This study aimed to determine the bacterial contamination level of drinking water from hand-pump-fitted borehole sources, the associated risk factor and its antimicrobial susceptibility pattern. Seventy-five hand-pump-fitted boreholes were selected randomly. Total coliforms and Escherichia coli count from water samples were performed using membrane filtration technique. MacConkey agar media was used for both samples and isolates were identified by standard microbiological methods. Antimicrobial susceptibility testing was carried out against seven antibiotics. About 11 (15%) hand-pump-fitted boreholes drinking water and 32 (42.6%) of swab samples showed culture positive. The colony counts for total coliforms and E. coli from water samples were 20–140 CFU/100 mL and 40–80 CFU/100 mL, respectively. E. coli, Enterobacter, Klebsiella, Citrobacter, Salmonella, and Pseudomonas sp. were the predominant isolated bacteria. E. coli and Salmonella sp. were found to be sensitive to all antibiotics and high level resistance was revealed by Klebsiella sp.

INTRODUCTION

Water is essential for the existence of humans and all living things and hence a satisfactory (adequate, safe and accessible) supply must be available to all. Water used for domestic purposes must be clean and not contain any microorganism, parasites and other substances which can pose danger to human health (WHO 2011; Alvarez-Bastida et al. 2018). Safe water supply and sufficient sanitation to secure health are among the essential human rights. However, many people do not have access to safe drinking water and risk to waterborne diseases is a critical public health problem in many developing countries (Chowdhury et al. 2016; Khalid et al. 2018). So securing safe drinking water for all is one of the significant difficulties of the 21st century. In a recent report, close to a billion people mostly living in the developing world do not have access to adequate and safe drinking water (Khalid et al. 2018).

Control of the microbial quality of drinking water should be a priority in all countries, given the immediate and potentially devastating consequences of waterborne infectious diseases (WHO/UNICEF 2017). Contaminated water serves as a mechanism to transmit communicable diseases such as cholera, typhoid and guinea worm infection (WHO 2013; Khalid et al. 2018). Around 88% of diarrhea cases worldwide are linked to unsafe water, inadequate sanitation or insufficient hygiene. Most cases of diarrheal illness and death occur in developing countries with an estimated annual incidence of 4,600 million episodes and cause 2.2 million deaths every year (WHO 2011).

Almost 6.1 billion people (89% of the world population) have used an improved drinking water source. This is 1% more than the 88% Millennium Development Goal target (UNICEF 2012). Improved sources of drinking water in developed countries has reached 99%. In contrast, in the developing world – especially in sub-Saharan countries – the coverage is still low (63%) with 51% and 84% coverage rates among rural and urban populations, respectively. Moreover, above 40% of all people globally who lack access to safe drinking water live in sub-Saharan Africa (UNICEF 2012). According to the WHO report (WHO 2013), 49% of the total population in Ethiopia used improved drinking water sources by the end of 2011. Access to improved drinking water in the urban population of Ethiopia is higher (97%) when compared with rural communities (39%).

Hand-pump-fitted boreholes are among the main sources of drinking water for the community. Globally the number of people using hand-pump-fitted boreholes grew from 1 billion in 1990 to 1.3 billion in 2010 in both urban and rural areas (UNICEF 2012). According to UNICEF/WHO (2011) report, about 30% (996 million) of the population use hand-pump-fitted boreholes water as a drinking water source. Out of the total hand-pump-fitted borehole users, 80% (almost a billion people) are rural populations (UNICEF 2012). In southern Asia, 56% of the rural population and 46% of the total population rely on hand-pump-fitted boreholes. In rural sub-Saharan Africa, 32% of people who use an improved drinking water source rely on hand-pump-fitted boreholes. This is far less than the global average including the south Asia coverage of water supply through hand-pump-fitted boreholes and tube wells (UNICEF/WHO 2011).

In Ethiopia, hand-pump-fitted boreholes, pipeline supplies, protected dug wells and protected springs are the main sources of drinking water for the community. These sources of drinking water serve more than 5% of the total Ethiopian population. Around 5% of the total population of Ethiopia and around 40% of the Tigray population rely on hand-pump-fitted boreholes (Tadesse et al. 2010). According to the baseline survey report from the Tigray region in 2011, there were 3,655 hand-pump-fitted borehole sources, 4,944 hand-dug wells fitted with hand pumps, 1,265 developed spring sources, and 186 motorized water sources. Hand-pump-fitted boreholes cover about 36% of the total sources. Hand-pump-fitted boreholes should be continuously monitored for WHO standards to provide safe drinking water for the community.

In Ethiopia, there is not enough data on the bacteriological quality of water from hand-pump-fitted boreholes sources in rural areas. Thus, evaluation of the bacteriological quality of these water sources will provide benchmark data about the bacteriological status and might enable insight into the development of further protective and treatment measures. Furthermore, information obtained from the present study might help in maintaining hand-pump-fitted borehole hygiene and determine the sources of contamination.

MATERIALS AND METHODS

Study area

The study was conducted in Kola Tembien district, which is found in central zone Tigray, 908 km from the capital city of Addis Ababa, and has an area of 147,000 hectares and a total population of 138,216. The area is situated in 13°39′N, 39°10′E and bordered on the north by Werie-Leke, in the east by Hawzen and Degua Tembien, in the south by Tankua Abergele and in the west by Tselemti and Naeder Adet. The administrative center for this district is Abiy Addi (Figure 1).

Figure 1

Map of the study area.

Figure 1

Map of the study area.

Groundwater (hand-dug, hand-pump-fitted boreholes) and spring water are the main sources of drinking water in the Kola Tembien rural area. There are 222 shallow hand-pump-fitted boreholes, three deep hand-pump-fitted boreholes, 193 hand-dug and 19 spring water wells in the area. However, out of the 222 hand-pump-fitted boreholes, only 202 are functional. From the district population, 119,000 individuals use these principal sources of water. However, the rest of the population of the district use other sources such as streams, rivers, and lakes.

Design and data collection of hand-pump-fitted boreholes

A cross-sectional study was conducted from September to November 2014. All hand-pump-fitted boreholes found in the Kola Tembien district were used as drinking water sources. From the 21 kebeles (administrative areas of at least 500 families) of the district which have hand-pump-fitted boreholes for drinking water sources, 75 of the sources were selected randomly from each kebele. The sample size was determined using single proportion formula, 
formula
(1)
where n is size of sample, Z is value of the standard variate at a given confidence level and to be worked out from the table showing area under normal curve, Xp is sample proportion that is contaminated, Xq is sample proportion that is not contaminated, N is total population, and d is acceptable error (the precision).

Sample size was calculated using the proportion value of contamination level of the hand-pump-fitted boreholes found in Tigray region from the study conducted by WHO in 2010 in Ethiopia. So p= 27.5%, q = 1−p = 72.5%, N = 202 hand-pump-fitted boreholes, d = 5% and n = 122.

Since, the total numbers of hand-pump-fitted boreholes in the district are less than 10,000, so a correction formula is used and calculated as follows: 
formula
(2)

Therefore, 75 hand-pump-fitted borehole sources of drinking water were sampled out of 202 from the district, so nc = 75.

Sample collection, transportation and processing

Twenty-five milliliters (mL) of drinking water and swab samples from the mouth of hand-pump-fitted boreholes were collected aseptically in sterile glass bottles and test tubes containing Cary-Blair medium, respectively. A sanitary risk assessment sheet or checklist was completed. Both types of samples were immediately transported using the cold box transport system to a Tigray regional laboratory for analysis.

Enumeration of total coliforms and E. coli from drinking water

Membrane filtration (MF) method was used to determine the degree of contamination (total coliforms and fecal coliforms) of drinking water samples. 10 mL of a water sample for each test was filtered through a sterile cellulose membrane filter with a pore size of 0.45 μm to retain the indicator bacteria and then the membrane filter was transferred to a sterilized plate containing MacConkey agar (Oxoid, UK). Petri dishes were incubated at 37 °C for 24 h and 44 °C for 16 h for total coliforms and fecal coliforms (Escherichia coli), respectively (Cheesbrough 2006; Doyle & Erickson 2006). Finally, the colonies were counted using a digital colony counter.

Bacterial identification from mouth swab samples

All swab samples were inoculated on MacConkey agar (Oxoid, UK). The plates were incubated in an anaerobic atmosphere at 37 °C for 24 h. Biochemical tests were performed on colonies from MacConkey (Oxoid, UK) for final identification of the isolates. Isolates from all culture-positive water and mouth swab samples were identified based on the standard culture and morphological characteristics in combination with indole production, H2S production, gas production, citrate utilization, motility test, lysine decarboxylation, lysine deamination and carbohydrate utilization tests (Vandepitte 2003).

Antimicrobial susceptibility test

Antimicrobial susceptibility test of isolates was performed on Mueller-Hinton agar (MHA) (Oxoid, UK) using a standard protocol for the Kirby Bayer disc diffusion technique. The antimicrobials tested include Amikacin (30 μg), Ampicillin (10 μg), Ceftriaxone (30 μg), Chloramphenicol, (30 μg), Ciprofloxacin (5 μg), Gentamicin (10 μg) and Tetracycline (30 μg). Pure culture was enriched in nutrient broth and incubated at 37 °C for 3 h to a turbidity of 0.5 McFarland standards. The MHA plate was inoculated using the sterile cotton swab. The antibiotic disks were applied using sterile forceps with an average distance of 30 mm from each other. The agar plate was left on the bench for 30 min to allow for diffusion of the antibiotics and the plates were incubated at 37 °C for 24 h. Susceptibility patterns were determined by measuring the diameter of the zone of inhibition using a ruler and comparing with the Clinical and Laboratory Standards Institute interpretive performance standard for antimicrobial disk susceptibility testing (Cockerill 2013). The results were recorded as susceptible, intermediate or resistant. Quality control was performed using E. coli ATCC™ 25922 (American Type Culture Collection; Oxoid, UK).

Quality control

The standard operating procedure was followed during sample collection, transportation and analysis. Media were sterilized before samples inoculated and also recommended control strains were used for all culture media and biochemical tests. Sanitary assessment sheets were checked for completeness.

Data entry and analysis

The data were entered and analyzed using computer software SPSS version 20 and the results were displayed using tables. Associations between different risk factors were determined using odds ratio in 95% confidence interval (CI) with p values less than 0.05 being considered statistically significant.

Ethical consideration

The study protocol was evaluated and approved by the Research Ethics Review Committee of College of Health Sciences, Mekelle University. Moreover, a letter of cooperation was written to Tigray regional water resources and energy bureau. During visiting of the drinking water sources, health education was given to the users on how to practice appropriate sanitation, hygiene, open defecation and waste disposal.

RESULTS

All 75 hand-pump-fitted boreholes sampled were located down the hill from agricultural land which might help to get water from an aquifer within a short distance from the surface. All sampled hand-pump-fitted borehole sources in the district were used solely for drinking and domestic purposes. The drainage channels of all studied hand-pump-fitted boreholes were not clean. There were no cracked cap, latrine, animal breeding or compost within a 10 m radius of the sources. Just one hand-pump-fitted borehole had a pond within a 10 m vicinity. In 30 (40%) of the sources, there were mini-gardens surrounding or within a 10 m radius. Around half (50.7%) of the studied hand-pump-fitted boreholes were not treated.

Bacterial contamination of drinking water

From the total of 75 drinking water samples from hand-pump-fitted boreholes, around 11 (15%) were positive for total coliforms with colony count 20–140 CFU/100 mL and from these positive samples, E. coli was isolated in three water samples with colony count 40–80 CFU/100 mL (Table 1). Based on WHO (2011) permissible values for drinking purposes, drinking water from these 11 hand-pump-fitted borehole sources was not bacteriologically safe or potable. The water from these sources free from E. coli and total coliforms were within WHO (2011) and Health Canada (2007) permissible values, which is zero CFU/100 mL.

Table 1

Total coliform and E. coli counts obtained for drinking water from hand-pump-fitted borehole sources

Code Site name Total coliform E. coli 
HPFBH1 Addi-bokri 0.60 × 102 
HPFBH5 Mesgole 1.40 × 102 0.80 × 102 
HPFBH12 Grat-htsa 0.90 × 102 
HPFBH18 Kechemo1 0.50 × 102 0.50 × 102 
HPFBH29 Weynako 1.00 × 102 0.40 × 102 
HPFBH33 Daero-nashim1 0.60 × 102 
HPFBH36 Goneo 0.70 × 102 
HPFBH40 Wshako 1.30 × 102 
HPFBH46 May welihans 0.20 × 102 
HPFBH60 Adarash 0.30 × 102 
HPFBH72 Serwegerebgereb 0.40 × 102 
Code Site name Total coliform E. coli 
HPFBH1 Addi-bokri 0.60 × 102 
HPFBH5 Mesgole 1.40 × 102 0.80 × 102 
HPFBH12 Grat-htsa 0.90 × 102 
HPFBH18 Kechemo1 0.50 × 102 0.50 × 102 
HPFBH29 Weynako 1.00 × 102 0.40 × 102 
HPFBH33 Daero-nashim1 0.60 × 102 
HPFBH36 Goneo 0.70 × 102 
HPFBH40 Wshako 1.30 × 102 
HPFBH46 May welihans 0.20 × 102 
HPFBH60 Adarash 0.30 × 102 
HPFBH72 Serwegerebgereb 0.40 × 102 

HPFBH, hand-pump-fitted borehole.

Isolation and antibiotic susceptibility patterns of bacteria from hand-pump-fitted borehole water

A total of 13 enteric bacteria isolates belonging to four genera was recovered from the 11 positive water samples from hand-pump-fitted borehole sources. Among these isolates Klebsiella sp. (38.5%) was the predominant pathogen followed by E. coli and Enterobacter (23% each) and Citrobacter sp. (15%). The antimicrobial susceptibility pattern of bacterial isolates showed that a significant number of isolates were resistant to Ampicillin (23%) and Tetracycline (8%). However, all bacterial isolates (100%) were sensitive to Amikacin, Ceftriaxone, Chloramphenicol, Ciprofloxacin and Gentamicin (Table 2).

Table 2

Antibiotic resistance patterns of isolates from hand-pump-fitted borehole sources of drinking water in Kola Tembien district, 2015

Isolates Antibiotics
 
AK (30 μg)
 
AMP (10 μg)
 
CFT (30 μg)
 
CAF (30 μg)
 
CIP (5 μg)
 
TTC (30 μg)
 
GEN (10 μg)
 
E. coli (n= 3) 
Klebsiella sp. (n = 5) 2 (40%) 3 (60%) 1 (20%) 1 (20%) 3 (60%) 
Enterobacter sp. (n = 3) 1 (33%) 2 (67%) 
Citrobacter sp. (n = 2) 
Total (n = 13) 13 3 (23%) 10 (77%) 13 13 13 1 (8%) 1 (8%) 11 13 
Isolates Antibiotics
 
AK (30 μg)
 
AMP (10 μg)
 
CFT (30 μg)
 
CAF (30 μg)
 
CIP (5 μg)
 
TTC (30 μg)
 
GEN (10 μg)
 
E. coli (n= 3) 
Klebsiella sp. (n = 5) 2 (40%) 3 (60%) 1 (20%) 1 (20%) 3 (60%) 
Enterobacter sp. (n = 3) 1 (33%) 2 (67%) 
Citrobacter sp. (n = 2) 
Total (n = 13) 13 3 (23%) 10 (77%) 13 13 13 1 (8%) 1 (8%) 11 13 

n, number of drinking water sample from hand-pump-fitted borehole sources with bacterial isolates; AMK, Amikacin; AMP, Ampicillin; TTC, Tetracycline; CFT, Ceftriaxone; CAF, Chloramphenicol; CIP, Ciprofloxacin; GEN, Gentamicin; R, Resistant; I, Intermediate; S, Sensitive. Values represent 100% of samples were sensitive unless otherwise stated.

Associated risk factors for the contamination of hand-pump-fitted borehole water

Out of the total hand-pump-fitted borehole drinking water sources found positive for total coliforms and E. coli, around 40% had a mini-garden within 10 m of the radius of the sources. The presence of a mini-garden within a 10 m radius of the source was significantly associated with bacterial contamination of drinking water from hand-pump-fitted boreholes (COR = 5.1, 95% CI: 1.23–21.1). However, this association was not statistically significant with lack of treatment in the adjusted odds ratio analysis (AOR = 3.02, 95%: 0.64–14.3).

Roughly 82% of contaminated drinking water from hand-pump-fitted borehole sources was not treated. The lack of treatment versus the contamination rate of drinking water from hand-pump-fitted borehole sources was statistically significant in the binary model analysis (COR = 5.4, 95% CI: 1.1–27.2). However, lack of treatment was not statistically significant in the adjusted odds ratio (AOR = 3.25, 95% CI: 0.6–18.2) with the presence of a mini-garden and contamination of the hand-pump-fitted borehole mouth.

Bacteria isolation from the mouth of the hand-pump-fitted boreholes was significantly associated with bacterial isolation from drinking water (COR = 4.4, 95% CI: 1.1–18.4). However, this association was not statistically significant with lack of treatment in the adjusted odds ratio (AOR = 2.2, 95% CI: 0.45–10.8).

Bacterial contamination and antibiotic susceptibility patterns of the mouth of a hand-pump-fitted borehole sources

Of the total mouth swab samples from hand-pump-fitted boreholes, approximately 43% (32) were culture positive. From these culture positive swabs, a total of 42 bacterial isolates belonging to six genera were recovered. Among these isolates, Klebsiella sp. (40%) was the predominant pathogen followed by Enterobacter sp. (29%), E. coli (10%) and Citrobacter, Salmonella and Pseudomonas sp. (7% each). The antimicrobial susceptibility pattern of bacterial isolates showed all isolates were found sensitive to Amikacin, Ciprofloxacin and Gentamicin. However, a significant number of isolates (26%, 17%, 10% and 7%) were resistant to Ampicillin, Tetracycline, Chloramphenicol and Ceftriaxone, respectively (Table 3).

Table 3

Prevalence antibiotic resistance patterns of isolates from hand-pump-fitted borehole mouths in Kola Tembien district, 2015

Isolates Antibiotics
 
AK (30 μg)
 
AMP (10 μg)
 
CFT (30 μg)
 
CAF (30 μg)
 
CIP (5 μg)
 
TTC (30 μg)
 
GEN (10 μg)
 
E. coli (n = 4) 
Klebsiella spp. (n = 17) 17 6 (35%) 11 (65%) 2(12%) 15 (88%) 1 (6%) 1 (6%) 15 (88%) 17 3 (18%) 1(6) 13 (76%) 17 
Enterobacter spp. (n = 12) 12 3 (25%) 9 (75%) 12 1 (8%) 11 (92%) 12 2 (17%) 10 (83%) 12 
Citrobacter spp. (n = 3) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 
Salmonella spp. (n = 3) 
Pseudomonase spp. (n = 3) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 
Total (n = 42) 42 11 (26%) 31 (74%) 3 (7%) 39 (93%) 4 (10%) 1(2%) 37 (88%) 42 7 (17%) 1(2) 31 (81%) 42 
Isolates Antibiotics
 
AK (30 μg)
 
AMP (10 μg)
 
CFT (30 μg)
 
CAF (30 μg)
 
CIP (5 μg)
 
TTC (30 μg)
 
GEN (10 μg)
 
E. coli (n = 4) 
Klebsiella spp. (n = 17) 17 6 (35%) 11 (65%) 2(12%) 15 (88%) 1 (6%) 1 (6%) 15 (88%) 17 3 (18%) 1(6) 13 (76%) 17 
Enterobacter spp. (n = 12) 12 3 (25%) 9 (75%) 12 1 (8%) 11 (92%) 12 2 (17%) 10 (83%) 12 
Citrobacter spp. (n = 3) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 
Salmonella spp. (n = 3) 
Pseudomonase spp. (n = 3) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 1 (33%) 2 (67%) 
Total (n = 42) 42 11 (26%) 31 (74%) 3 (7%) 39 (93%) 4 (10%) 1(2%) 37 (88%) 42 7 (17%) 1(2) 31 (81%) 42 

n, number of swab sample from the mouth of hand-pump-fitted borehole sources with bacterial isolates; AMK, Amikacin; AMP, Ampicillin; TTC, Tetracycline; CFT, Ceftriaxone; CAF, Chloramphenicol; CIP, Ciprofloxacin; GEN, Gentamicin; R, Resistant; I, Intermediate; S, Sensitive. Values represent 100% of samples were sensitive unless otherwise stated.

Associated risk factors for bacterial contamination of the mouth of a hand-pump-fitted boreholes

Out of the 30 mouth swab samples from the mouth of hand-pump-fitted boreholes located within 10 m the radius from the mini-garden, 19 (63%) of them were culture positive for bacterial growth. The presence of a mini-garden in the surrounding area was statistically significant with bacterial contamination of the mouth of the hand-pump-fitted boreholes, P = 0.034 (AOR = 3.099, 95% CI: 1.090–8.0808). Therefore, the chance of contamination of the mouth of a hand-pump-fitted borehole in the presence of a mini-garden within a 10 m radius was three times when compared with the absence of a mini-garden within a 10 m radius. This may be a result of the dumping of household waste in mini-garden areas.

Out of 38 mouth swab samples from the mouth of a hand-pump-fitted boreholes, which were not treated, 22 (58%) were positive for bacterial growth. Although statistical analysis of the lack of treatment versus bacterial contamination of a hand-pump-fitted borehole source's mouth was significant in the binary model analysis (COR = 3.713, 95% CI: 1.407–9.795), the lack of treatment was not statistically significant when adjusted to the presence of a mini-garden in adjusted odds ratio analysis (AOR = 2.662, 95% CI:0.944–7.508).

DISCUSSION

Bacteriological analysis

Bacteriological analysis of water using indicator organisms (total coliforms and E. coli) determines the potability of drinking water. In our study, total coliforms and E. coli were found in 11 (15%) and 3 (4%) of hand-pump-fitted borehole water sources with a range of 20–140 and 40–80 CFU/100 mL, respectively (Table 1). These exceed the WHO (2011) and Health Canada (2007) maximum permissible limit (0 CFU/100 mL) for drinking water. Based on the colony count of E. coli in 100 mL of drinking water sample, three were an intermediate risk to the people who use these sources. The presence of total coliforms in groundwater indicates that the groundwater sources may be vulnerable to contamination by more harmful microorganisms.

The present findings on the instances of contamination of drinking water from the studied sources coincides with reports from South Darfur, Sudan of 11.3% (Eltahir & Abdelrahman 2013). However, this is lower than the results reported in Nigeria (Bello et al. 2013) and South Africa (Samie et al. 2011) found 100% contamination of drinking water from hand-pump-fitted borehole sources. In addition, in Ghana and Nigeria the total coliform contamination found in hand-pump-fitted borehole drinking water is approximately 63% and 40%, respectively (Odonkor & Addo 2013). In contrast, our finding is higher than the zero percent contamination rates reported from Malawi (Jabu 2005). Many factors contribute to the observed differences in contamination rates among the studies of the drinking water. Agricultural sources, organic wastes, infiltration of irrigation of water, septic tanks, pit latrine around the sources, treatment barriers, biofilm development within the sources and personal hygiene are all possible reasons for a high contamination rate by total coliforms and E. coli (Aydin 2007; Bello et al. 2013). However, in the present study, these sources of contamination, with the exception of treatment barrier and agricultural sources, were absent. Therefore, the lower contamination rate of drinking water from hand-pump-fitted boreholes may be due to the absence of risk factors found in previous studies.

In the present study, Klebsiella sp. was the predominant isolate from the drinking water sample. However, studies conducted in Nigeria found Klebsiella sp. in drinking water to be the second most isolated species with an isolation rate of 17% (Aydin 2007; Bello et al. 2013). In this study, E. coli and Enterobacter sp. were the second most isolated species from drinking water samples. However, similar studies in Nigeria found E. coli to be the most isolated (33%) from drinking water from hand-pump-fitted borehole sources and other studies in Nigeria reported Enterobacter sp. (28.85%) as most frequently isolated bacterial species from drinking water from hand-pump-fitted borehole sources (Bello et al. 2013). Although there is no evidence that Enterobacter sp. are transmitted through drinking water, it is plausible that the organism could be present in poorer quality water and may occasionally cause community-acquired infections.

Citrobacter sp. is reported to occur in environments such as water, sewage, soil and food. Although there is no evidence that these bacteria are transmitted through drinking water, Citrobacter sp. may sometimes acquire the ability to produce an enterotoxin and thus become an intestinal pathogen (Sneath et al. 1986). In this study, Citrobacter sp. was the least isolated organism from drinking water samples from hand-pump-fitted borehole sources.

Antibiotic susceptibility pattern

An antibiotic susceptibility test was done for all bacteria isolated from water samples and all E. coli and Citrobacter sp. were sensitive to all antibiotics. A recent study conducted in Nigeria on similar sources found that 100% of E. coli was sensitive to Ciprofloxacin and Gentamicin (Bello et al. 2013). In contrast, other parallel studies in South Africa and Nigeria showed E. coli resistant to Ampicillin, Amikacin, Gentamicin, Ceftriaxone, Ciprofloxacin, Tetracycline and Chloramphenicol (Samie et al. 2011; Bello et al. 2013). Klebsiella sp. from the water samples was sensitive to all tested antibiotics except Ampicillin and Tetracycline. In addition, all Enterobacter sp. from water samples was sensitive to all tested antibiotics except Ampicillin (Table 2). Our findings agree with studies conducted in Nigeria (Bello et al. 2013; Odeyemi et al. 2017).

An antibiotic susceptibility pattern was performed for all bacteria isolated from swab samples and E. coli and Salmonella sp. were sensitive to all tested antibiotics (Table 3). A similar study conducted in Nigeria also found E. coli and Salmonella sp. were 100% susceptible to Chloramphenicol, Ciprofloxacin and Gentamicin (Bello et al. 2013). Klebsiella sp. from swab samples were sensitive to Amikacin, Ciprofloxacin and Gentamicin. Contrary to our findings, a similar study conducted in Nigeria showed Salmonella sp. was resistant to Ampicillin, Gentamicin and Tetracycline (Odeyemi et al. 2017).

All Enterobacter sp. from swab samples were sensitive to Amikacin, Ceftriaxone, Ciprofloxacin and Gentamicin. However, 25% of Enterobacter sp. was resistant to Ampicillin, 16.7% Tetracycline and 8.3% Chloramphenicol (Table 3). A similar study conducted in Nigeria also found Enterobacter sp. resistance to Chloramphenicol, Ciprofloxacin and Gentamicin (Bello et al. 2013).

Citrobacter and Pseudomonas sp. showed 100% susceptibility to Amikacin, Ciprofloxacin and Gentamicin, but also, all Citrobacter sp. were sensitive to Ceftriaxone. However, 33% of Pseudomonas sp. was resistant to Ampicillin, Chloramphenicol, Tetracycline and Ceftriaxone and also 33% of Citrobacter sp. was resistant to Ampicillin, Chloramphenicol, and Tetracycline. Our findings also agree with recent studies conducted in Brazil and Ethiopia (Lourenço et al. 2007; Abera et al. 2014).

CONCLUSIONS

In this study, we found that 11 (15%) hand-pump-fitted borehole sources were not suitable for drinking with regard to the WHO recommended guideline values for drinking water. Swab samples from 43% of hand-pump-fitted borehole mouths were culture positive for E. coli, Klebsiella, Enterobacter, Citrobacter, Pseudomonas and Salmonella sp.. These bacteria, except Pseudomonas and Salmonella sp., are all similar to the bacteria isolated from drinking water. Therefore, regular microbial assessment of all borehole drinking water sources should be carried out in the district seasonally and health education should be given to the community to practice appropriate sanitation, hygiene and waste disposal.

In future, it is important to ensure that incidences of microbial contamination are identified in advance/earlier so that remedial action can be taken by responsible bodies. There should be regular maintenance and rehabilitation of hand pumps on boreholes. Government and other stakeholders should fulfill its basic responsibility of providing safe drinking water to communities particularly in developing countries.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the support of Kola Tembien district water and energy bureau for their support and providing free transport during the sample collection. The authors would like to acknowledge the staff of Tigray Regional Laboratory and Ayder Referral Hospital Microbiology Laboratory for providing facilities.

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