Abstract: Twenty rainwater samples each were randomly collected from four geographical zones of Ondo State, Nigeria, which fall under a rain zone of 1200 mm annually. Eosin methylene blue agar was used to isolate Escherichia coli from the water, while nutrient agar was used for enumeration of total bacterial count and violet red bile lactose agar for Coliform bacilli. Escherichia coli isolates from the rainwater samples were subjected to antibiotic assay. Among the rainwater samples collected from each zone, Ondo State South had the highest (28.72%) E. coli occurrence. Also, the E. coli isolates from this zone were found less sensitive and resistant in most cases to the antibiotics. The average mean E. coli counts recovered from the rainwater samples ranged between 4.50-4. 80 (log cfu m-1). This count is above the recommended value (0/100 mL) in water quality by WHO standard. The E. coli isolates showed various degree of sensitivity to the antibiotics potency ranging from 0->10 mm diameter inhibitory halo. Meanwhile, nitrofurantoin, augmentin and amoxylin had very low potency on the isolated E. coli with 0 and 25%, respectively, while others had high potency of between 75-100% on the isolates.
INTRODUCTION
The availability of quality water dictates the quality of life since water is a basic requirement of life. Despite the various sources of water supply for human use, water quality is still a luxury in developing and underdeveloped countries. Water, like air resources and its regular and plentiful supply in an uncontaminated form, is essential for the survival and health of man and most living organisms (Kumar, 2002). Since water is very essential especially for domestic purposes, the use of rainwater is a common practice in most homes in both urban and rural areas in Ondo State, Nigeria, where portable water supply is a problem. However, it had been demonstrated vividly that water sources are able to be contaminated with Escherichia coil (Feachem, 2001; Chao et al., 2004). Justus (2002) observed that the pollution of water supply with human feaces has been recognized many years as public health problems. Rather it is becoming clearer that this is not only so as sewage from crowded communities can also affect the ecological balance of the surrounding environment. The immediate environment of water sources are the major source of contamination and this include the opening surrounding (Okafor, 2005). Among bacterial isolates of diarrhea, respiratory and commensal enteric pathogens (Kunin, 1993; Sack et al., 1997), antibiotic resistance is increasing particularly to first-line, inexpensive and broad-spectrum antibiotics. Also, the selection and spread of resistant organisms in developing countries which can often be traced to complex socioeconomic and behavioral antecedents, contributed to the escalating problem of antibiotic resistance worldwide (Okeke et al., 1999). Rainwater in its natural form supposed to be pure but the prevailing human activities such as uncontrolled waste disposal, drying up of ponds and rivers at times regulated by negative ecological distribution and the method of collection of rainwater in the area of study (6 ft or less) above ground level, could immensely contribute to the occurrence of intestinal and non-intestinal E. coli contamination of rainwater. Hence antibiotics are used for the treatment of both intestinal and non-intestinal Escherichia coil diseases, this research is therefore aimed at surveying antibiotic assay pattern of E. coli isolates from rainwater obtained from four different locations in Ondo State Nigeria.
MATERIALS AND METHODS
Collection of Rainwater Sample
Twenty rainwater samples each were randomly collected from the rural and
urban areas of the four geographical zones (North, South, East and West) of
Ondo State, Nigeria, between March and December, 2005. The rainwater samples
were collected during rain into sterile polypropylene bottles from mounted stands
of 6th above ground level. The bottles were allowed to fill up to the brim to
trap air, tightly covered and taken to the laboratory within 2 h for analysis.
Bacteria Analysis
Nutrient agar was used for the enumeration of total viable count. With Collins
et al. (1995) criteria, coliform count in the rain water samples was
detected, where 1 mL of each sample was serially diluted to tenfold dilution
and plated with violet red bile lactose agar and incubated at 37°C for 24
h. Red resultant colonies with up to 0.5 mm or larger in diameter were recognized
and counted as Coliform bacilli. Escherichia coli in the rainwater
sample was enumerated with eosine methylene blue agar, where 1 mL of each sample
was plated and incubated at 37°C for 24 h. Only colonies that demonstrated
green metallic sheen were recognized and identified as E. coli.
Antibiotic Assay
The fondiscs laboratory multor sensitivity discs (Gram negative) was used
to assay the sensitivity pattern of the isolated E. coli. The antibiotics
and its concentrations impregnated on the commercial disc arms are Augmentin
(AUG) 30 mg, Amoxycllin (AMX) 25 mg, Getriazone (CRO) 30 mg, Contrimoxazole
(COT) 25 g, Ciprofloxacin (CPX) 10 mg, Gentamycin (GEN) 10 mg, Nitrofurantoin
(NIT) 200 mg, Ofloxacin (OFL) 54 mg, Penfloxacin (PFX) 5 mg and Tetracycline
(TET) 30 mg. A concentrated 1 mL broth culture containing about 107-108
cells of the isolated E. coli in their log phase were pour plated with
nutrient agar on sterile petri plates. The plates were allowed to solidify and
stand for about 1 h, for the test organisms to be fully embedded in the medium.
With a sterile forceps, the sensitivity discs were aseptically taken and carefully
placed at the surface center of each seeded plates. They were incubated uninverted
at 37°C for 24 h. The inhibitory halo (s) were measured with plain plastic
ruler and were taken as an index of the degree of sensitivity.
RESULTS
The total bacterial mean counts in the rainwater samples ranges between 4.50-4.80
log cfu m-1. Ondo State East and West zones had the least bacterial
mean counts of 4.50 log cfu m-1 each and was highest in Ondo State
South with 4.80 log cfu m-1 (Table 1). The rainwater
samples obtained from Ondo State South also had the highest E. coli occurrence
with 28.72% (Table 2). Meanwhile, the total percentage occurrence
of E. coil in the rainwater collected from the four geographical zones
was 100%. The sensitivity pattern of the isolated E. coli to the antibiotic
is shown in (Table 3). The E. coli isolated from the
South zone had low response to the antibiotics potency, which denotes resistance
pattern of 40%, unlike the E. coli isolates from East and West zone with
high response of 80 and 70%, respectively to the antibiotics sensitivity (Table
3).
| Table 1: | Bacterial mean viable counts obtained from the rainwater sample (log cfu m-1) |
| *Values are means of three replicates | |
| Table 2: | Escherichia coli mean counts obtained from the rainwater samples (log cfu m-1) sample |
| *Values are means of three replicates | |
| Table 3: | Antibiotic assay on the isolated E. coli from the rainwater |
| AUG: Augmentin, AMX: Amoxicillin, CRO: Ceftriazone, COT: Contrimoxazole, CPX: Ciprofloxacin, GEN: Gentamycin, NIT: Nitrofurantoin, OFL: Ofloxacin, PFX: Pefloxacin, TET: Tetracycline, ++: Inhibitory halo >10 mm, +: Inhibitory halo<10 mm, - : No inhibition | |
DISCUSSION
The danger normally associated with drinking water is contaminations by chemicals, physical and biological means generated mainly by human activities. These human activities in most cases served as air pollution. Rainwater is often subjected to such contaminations as a result of air current and the already suspended particles matters in the atmosphere. Contaminants introduced into water supply perpetuate many diseases and examples of such pathogens are Salmonella sp., Shigella sp., Vibro cholera and E. coli (Tortora et al., 2002). However, hence, E. coli has been implicated in causing human diseases such as urinary track infection (Geoffry and Charles, 1990), traveler’s diarrhea (Twort et al., 1985), severe diarrhea in all age groups (Tortora et al., 2002) and many other diseases, there is need for their surveillance and possible methods of their suppression if they can not be avoided. It is very obvious that the achievement and maintenance of acceptable environment standards cannot be totally met in any community due to human activities resulting to microbial contaminations. Based on this factor, rainwater is liable to colonization with microbial cells introduced into it from the environment by windstorm or air current during rain. The quest of the people in reliably use of rainwater for domestic purposes, is that, it is less contaminated with microbial pathogens unlike surface and shallow well water which are easily contaminated from divers water runoff E. coli is the microbial agent usually employed as indicator of water borne pathogen (Chao et al., 2004). The result obtained from this study showed that the rainwater samples were contaminated with E. coli populations, which is far below the standard of drinking water quality (0/100 mL) as recommended by WHO (2001). Hence availability of portable water is scarce and the people depends mostly on well and rainwater, checking water borne diseases is of paramount important for the people’s health safety. Meanwhile, no related work has been carried out on rainwater being consumed by the people hence this work will add to the cautions in improving health care system in this area. The heaping up of wastes and their decomposition on the open ground surface, couple with human excrement on dump and non-dump sites and animal excrement on the street in the area of study (Akharaiyi and Omoya, 2004) could be responsible for the very high microbial load and the existence of E. coli contamination in the rainwater.
Despite the possibility of E. coli contaminating water sources, their absence in water can be avoided if sewages human and animals excrements in the environment can be controlled with much emphasis on their dangers as microbial contamination of quality water and foods.
Different sensitivity patterns were displayed by the isolated E. coli to the antibiotics used in this study. Contrimoxazole, Ciprofloxacin and Gentamycin, displayed high potency (100%) over the isolated E. coli genera than observed in the other antibiotics. Oyetao et al. (2007) observed that E. coli isolated from well water in Akure, Ondo State, Nigeria, were sensitive to norfloxacin, gentanycin, ciprofloxacin and chloramphemcol. Also, similar observation was recorded by Nazir et al. (2005) from E. coil isolates obtained from river, pond, drain and tap waters in Bangladesh. Residents of developing countries often carry antibiotic-resistant fecal commensal organisms (Calva et al., 1996) been majorly due to motives for self-medication and antibiotics misuse by lay persons, health professional and unskilled practitioners.
Apparently, health people in developing countries carry potentially pathogenic antibiotic resistant organisms asymptomatically (Woolfson et al., 1997). Several factors, such as urban migration with crowding and improper sewage disposal, encouraging the exchange of antibiotic-resistant organisms between people and the exchange of resistance genes among bacteria are among what that are responsible for the increase in the prevalence of resistant strains. Jawetz (1984), reported that the release of this multi-drug resistant E. coli through fecal materials, could eventually lead to the saturation of the environment with antibiotic resistant strains. Hence, this, however can lead to economic problem, a high knowledge of proper waste disposal and dangerous chemical substances in the environment should be acknowledge to avoid the indiscriminate spread of antibiotic resistant bacterial strains.