African Journal of Biomedical Research Ibadan Biomedical Communications Group ISSN: 1119-5096 Vol. 6, Num. 2, 2003, pp. 79-84

African Journal of Biomedical Research, Vol. 6, No. 2, May, 2003, pp. 79-84

ANTIBIOTIC SENSITIVITY PROFILE OF MICROORGANISMS ENCOUNTERED IN THE LAGOS LAGOON , NIGERIA

AJAYI A. O ¹* AND AKONAI K.A ²

¹ Department of Microbiology, Adekunle Ajasin University , P.M.B. 01, Akungba-Akoko, Ondo State .
² Department of Microbiology, Obafemi Awolowo University , Ile-Ife , Osun State Nigeria
*Corresponding Author.

Received: December 2002
Accepted in final form: March 2003

Code Number: md03015

ABSTRACT  

The Lagos Lagoon is an area of salt and brackish water situated in the western part of Nigeria . The in vitro antibiotic sensitivity profiles of microbial isolates encountered in the 24 designated sampling sites of the Lagos Lagoon were determined. 46 (60%) of these microorganisms tested showed multiple antibiotic resistance. This included the enteric gram negative short rods such as Klebsiella spp., Enterobacter spp.and Escherichia coli. The prevalence of multiple antibiotic resistant microorganisms in fresh water as well as marine environment may be important, since their presence indicates recent contamination with sewage. This resistant organisms may contaminate fish and other products within the food chain and if such are consumed by humans, it may become part of the individual flora. The Lagos Lagoon is populated with pathogenic bacteria and the pathogenic organisms are more likely to be found in area of low salinity than in areas of high salinity. The enteric organisms found in most areas showed multiple antibiotic resistances, which is significant healthwise.  

Keywords: antibiotic, microorganisms, lagoon, Lagos , Nigeria

INTRODUCTION

The Lagos Lagoon is an area of salt and brackish water separated from the adjacent sea by a low-lying sand or shingle barrier. The high level of urbanization and industrialization of the city of Lagos and its environs with inevitable generation of domestic and industrial wastes have led to biological consequences in the coastal aquatic environment (Ajao 1990). The Lagos Lagoon is situated in the western part of Nigeria . The central body of the Lagoon is located between longitude 3 0 23' and 3 0 40'E and latitude 6 0 22' and 6 0 28'N. it is the largest of the four Lagoon system of the Gulf of Guinea Coast (Webb. 1958).

The importance of the Lagoon and estuaries as sources of fishery products and as desirable recreation areas is now being recognized with increasing awareness. This is coupled with global increase in population and resultant waste generated. In the estuaries a large part of conversion of solar energy into plant life take place and it is where many of the commercially harvested marine animals begin their lives (Halasi-Kun, 1981; Webb, 1958).

The discharge of raw sewage into the Lagoon has important health implication (Akpata and Ekundayo 1978; Halasi-kun, 1981). The occurrence of the enteric organisms and other microorganisms in the Lagos Lagoon may lead to contamination of aquatic life and other food products, thereby causing possible health hazard unto those that consume these products. Thus, in the cause of treatment or control of infectious disease that can originate from this source, the study of the antibiotic sensitivity profile of the organisms encountered becomes of importance. Similarly, with recent scientific and biotechnological discoveries, various strains of microorganisms with unique physiological and biochemical characteristics has emerged from our environments (Prescott et al ,2002), Thus much attention is focused on assessing impacts such organisms have on the ecological environment. Their clinical effects on human health, industrial values and other socio-economic importance are also considered

MATERIALS AND METHODS

Sample collection from study site: Specific sites were mapped out on the Lagos Lagoon for the study with the assistance of the Nigerian Institute for Oceanography and Marine Research (NIOMR). Twenty four sampling point were located, with the aid of a compass, from where surface water and sediment samples were collected. Sterile plastic container was used in collecting the water with the aid of a Ruttner standard water sampler, 8cm diameter and 50cm long, capacity 500ml. A "Metal grab" was employed in collecting the sediment, part of this was packed into sterile plastic nylon seals and kept together with the water samples in the cooler. All stations were sampled in February and June period.

Laboratory procedure: The salinity of the water sample was determined using salinometer. According to Okafor (1986), the major property of marine is its high salinity (or sodium chloride content) which reaches 3.5% in the open ocean and it varies in the Lagoon. Salinity is recorded as gram of solid per kilogram of water (0/00) by marine scientists. The antibiotic sensitivity profile of each isolate was also determined. The water samples were analysed within 36 hours of sample collection.

Discrete microbial colonies were obtained employing a millipore membrane filter technique for the surface water while a pour plate technique was used to get isolated colonies from the sediment sample. The bacterial colonies that grew on the medium plates were incubated at 37° C for 18-24 hours. After incubation a gram stained film of each discrete microbial colony was prepared. Each bacterial isolate was identified based on their morphological characteristics, their colour, and arrangement of vegetative cell and possession of spores (Robert et al 1984; Kotzekidou, 1996). Each isolate was preserved on nutrient agar slopes for further characterization, identification and research purposes.

Antibiotic Sensitivity Test: The in vitro antibiotic susceptibility testing of bacteria isolates was performed using the standardized disc agar diffusion method described by Bauer et al . (1996). Paper disc medium (PDM), Antibiotic sensitivity agar (AB BIO DISK, Solna , Sweden ) was the Plating medium used.

Placement of disc: Antibiotic disc were placed at equidistance from each other on the plate with the aid of a pair of sterile forceps. Each disc was then pressed firmly onto the agar with the sterile forceps to ensure complete contact with the agar. The plates were inverted and placed in the refrigerator for 30minutes to allow for diffusion of the antibiotics into the agar. They were removed and incubated at 35 0 C for about 18hours. The antibiotic discs (AB BIODISK, Solna , Sweden ) that were used for this test include:

Gentamicin - 30 μ g/disc;

Nalidixic acid - 30 μ g'disc;

Tetracycline - 30 μ g/disc;

Trimethoprim+Sulfamethoxazole1-2+23.8 μ g/disc;

Trimenthoprim - 1.2 μ g:

Spectinomycin - 30 μ g;

Ampicillin - 10 μ g;

Sulfamethoxazole - 23.8 μ g;

Chloramphenicol - 30 μ g;

Streptomycin - 30 μ g.

Reading and Interpretation of Results

The portion between the end point and the areas showing no visible growth was taken as the zone of growth inhibition and was measured by means of a ruler diagonally in millimeters from the underside of the plates. Scanty growths near the edge of the inhibition zones were regarded as resistant strains. AB Biodisk manual for interpretive zone diameter standards were used to interpret the diameter of zone inhibition. Isolates were then scored as either sensitive or resistant.

RESULTS

Samples used for analysis were obtained from 24 sites in the Lagos Lagoon. The salinity of the Lagoon water was determined and expressed in part per thousand (PPT). For the month of February the range was from 4PPT to 14.7PPT. During the month of June the Salinity ranged from zero (0) value of fresh water to a high of 12PPT. The average salinity during the mouth of February was 7.6PPT for the entire period of sampling compared with a significantly lower mean of 2.03PPT recorded during the month of June (Table 1).

The in vitro antibiotic sensitivity test was performed for all the bacterial isolate to (Tables 2&3). Table 4 shows the pattern of antibiotic resistance. A total of 77 strains were tested with 46 (60%) of the strains showing multiple antibiotic resistance. Moreover, it will be observed in the result summarized in table 4 that both the Bacillus and enteric group of organisms which are the predominant microbial strains encountered showed much of the multiple antibiotic resistance in this study. The pathogenic organisms are observed to be found in areas of low salinity than in areas of high salinity (Table 1-3).

DISCUSSION

The in vitro antibiotic sensitivity profile of microbial isolates encountered in the Lagos Lagoon marine environment was determined. Twenty four stations were mapped out in the Lagoon by the Nigeria Institute for Oceanography and Marine Research (NIOMR) Lagos and samples were obtained at these sites.

The salinity profile in this shallow Lagoon probably delinated the limits of distribution of stenohaline and euryhaline species during the two periods when samples were collected. Tidal influence and seasonal rainfall have been reported to cause salinity fluctuation of 20% diurnal and 34% annually (Hill and web, 1958).

Table 1 shows that the Lagoon salinity was low during the month of June compared with relatively high salinity recorded for February in most of the designated stations. These periodic changes in salinity could have influenced seasonal distribution of microorganisms (Olaniyan 1957; Sandison and Hill, 1966; Fagade and Olaniyan, 1974).

Table 1: Salinity profile of Lagos Lagoon surface water

ND = Not Determined

The in vitro antibiotic sensitivity profile of the isolates were determined; 46 (60%) of these microorganisms tested showed multiple antibiotic resistance. This included the enteric gram negative short rods such as klebsiella sp., Enterobacter sp., and Escherichia coli;.

The prevalence of multiple antibiotic resistant microorganisms in fresh water as well as marine environment may be important, since their presence indicates recent contamination with sewage.

Table 2: Antibiotic Sensitivity Profile for Lagos Lagoon Sediment Samples:

TABLE 3: Antibiotic Sensitivity Profile for Surface Water Samples

LEGEND: S : Sensitive R : Resistant

Antibiotics: G M- Gentamycine; NA- Nalidixic Acid; TS- Trimethoprim + Sulfamethoxazole TR- Trimethoprime; AM- Ampicillin; SM- Streptomycin SC- Spectinomycin; SX- Sulfamethoxazole; CL- Chloramphenicol.

The resistant organisms may also contaminate fish and other products within the food chain and if such are consumed by humans, it may become part of the individual's flora. As a result of selective pressure, such organisms may establish themselves within the individuals and became the predominant microflora. In the event of infection caused by such organisms, treatment will be difficult. Individuals coming in contact with the water and with open sores or sounds may be exposed to contamination with resistant organisms.``

In conclusion, this study shows that Lagos Lagoon is populated with pathogenic bacteria and that the pathogenic organisms are more likely to be found in areas of low salinity than in areas of high salinity. The enteric organisms found in most areas showed multiple antibiotic resistances which is significant health wise. If such organisms are consumed by marine organisms, they could spread within the food chain. The study also indicates the prevalence of multiple antibiotic resistant bacteria isolates in natural water probably as in this study through contamination with human wastes. The results of antibiotic sensitivity profile of microbial strains encountered in Lagos Lagoon that is ecologically marine in nature should be helpful for health-care administrators in proper monitoring of our natural waters and suggest possible solutions to problems that may arise from resistant microbial strains that could invade our communities from these sources

TABLE 4 : Pattern of Antibiotic Resistance

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