Assessment Of Vibrio Speciesandplesiomonas Shigelloides Incidences, With Their Antibiotics Resistant Genes And Physicochemical Qualities Of Selected Rivers In Southwest Nigeria
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2017
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Abstract
This study determined the physicochemical and heavy metal concentrations of selected rivers and evaluated the prevalence and antibxiogram profile of the Vibrio species and Plesiomonasshigelloidesselected rivers in Southwest Nigeria. It also characterized the antibiotic resistance determinants in the bacteria species and evaluated the health risk potentials of these bacteria with regards to different water uses. This was with a view to providing information on the seasonal distribution of these contaminants and overall pollution status of the study area.
A total of 144 water samples collected over a period of twelve calendar month between February 2015 and January 2016 from four rivers (Asejire, Ona, Dandaru and Erinle rivers, Southwest Nigeria) were analysed for physicochemical parameters comprising; Temperature, pH, Electrical Conductivity (EC) and Total Dissolved Solids (TDS), Turbidity, Nitrate, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD), Nitrate (NO3-) and Phosphate (PO43-). Heavy metals: Cadmium (Cd), Lead (Pb), Chromium (Cr), Arsenic (As) and Manganese (Mn) concentrations were determined using Atomic Absorption Spectrophotometry method. Human health risk assessments were evaluated using USEPA protocol. Vibriospp. andPlesiomonasshigelloides were isolated and confirmed using Polymerase Chain Reaction (PCR) and further characterised for their antibiogram profile. The resistant isolates from both organisms were screened for resistance determinantwith 11 genes each using PCR technique.
The result showed that heavy metal concentrations which had highest values recorded for As (0.016 mg/L) at Asejire reservoir, Cd (0.022 mg/L) at Ona, Cr (0.063 mg/L) at Dandaru, Pb (0.018 mg/L) and Mn (0.190 mg/L) both at Erinle river respectively exceeded the prescribed limit for drinking water. Physicochemical parameter of water results showed temperature (31oC) and turbidity (11 mg/L) were highest at Asejire reservoir and exceeded the prescribed limits while pH (7.25), BOD (1.45 mg/L) and NO3-(0.89 mg/L) were lowest at Ona river. Human health risk assessment of heavy metals showed that the carcinogenic risks through ingestion of water from these rivers and the reservoir were as much as the non-carcinogenic risks. Vibrio (n=315)andPlesiomonasshigelloides (n=66)were confirmed by PCR. Vibrio speciation confirmed presence of V. vulnificus(13.3%), V. harveyi(2.2%), V. parahaemolyticus(17%), V. cholerae (2.2%) and V. mimicus(4.4%) V. hollisae(n=1) with high predominance of species during rainy months. Vibrio isolates were resistance to erythromycin (95%), sulphamethoxazole (94%), rifampicin (92%), doxycycline (82%), tetracycline (75%), amoxicillin (45%) and cephalothin (43%), and variedly susceptible to others antibiotics. Likewise, P. shigelloides isolates were resistant to sulphamethoxazole (100%), erythromycin (93%), ampicillin (90%), cephalotin (82%), streptomycin (64%), and chloramphenicol (58%), amoxicillin (53%), cefotaxime (50%), tetracycline (49%), neomycin (38%), trimethoprim + sulphamethoxazole (36%). The multiple antibiotic resistance indices of both organisms exceeded the standard threshold limit of 0.2. Prevalence and distributions of 11 resistance determinant were obtained as follows for P. shigelloides: [sulfonamides (sulI (18%), sulII (20%), dfr1 (70%), dfr(18) (5% )], [beta-lactams; (ampC 37%)], [tetracyclines(tetA (78%), tetE (57%)], [phenicols; (catII (16%), cmlA1 (11%)] and [aminoglycosides; (aphA2 (36%) and strA (67%)], for Vibrio; [sulfonamides (sulI (19%), sulII (33%)], [beta-lactams; (ampC 39%; blaOXA (27%), blapse (11%)], [tetracyclines (tetA (28%), tetE (20%), tet39 (8%)] and [aminoglycosides; (aacC2 (24%), aphA1 (14%),strA (39%)]. Strong positive correlations between Cd and blapse, Cr and sulII(Vibrio spp.) and As and aphA2 (P. shigelloides) were observed.
This study concluded that pollution by heavy metals, Vibriospp, P. shigelloides and their antibiotic resistance determinants in the selected rivers and the reservoir posed potential public health risk which indicated that the selected river water were not potable without treatment.
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physicochemical, concentrations, antibxiogram, antibxiogram, Southwest, Nigeria