HYDROCARBON DEGRADING ABILITY AND PATHOGENICITYPATTERNOF STREPTOCOCCI FROM DIFFERENT ENVIRONMENTS AT THE FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE NIGERIA.

Abstract

A study was carried out to isolate streptococci associated with environmental and human samples collected from different environments within the Federal University of Technology, Akure, Ondo State, Nigeria and to analyze their antibiotic sensitivity pattern and hydrocarbon degradative abilities. The samples were analyzed microbiologically using standard microbiological techniques. Twenty-two isolates of twelve species were obtained from the study. The isolates were identified as Streptococcus pneumoniae (2), Streptococcus pyogenes (2), Streptococcus agalactiae (2), Streptococcus anginosus (2), Streptococcus salivarius (2), Streptococcus equi (1), Enterococcus avium (1), Enterococcus faecium (2),Enterococcus faecalis (2), Streptococcus mutans (2), Streptococcus oralis (2)and Streptococcus sanguis (2). The antibacterial activity of 13 commercial drugs against the isolates was assayed by Kirby-Bauer disc diffusion method and data on the diameter of inhibition zones produced by Streptococcus spp shows that the mean range of diameter inhibition zones observed were pefloxacin (12.20-26.60 mm), gentamicin (9.73-22.50 mm), septrin (8.00-24.17 mm), ampicillin (10.00-24.00 mm), amoxicillin (12.07-23.00 mm), cefuroxime (12.03-27.00 mm), ceftriaxone (15.13-27.67 mm), ciprofloxacin (9.03-25.37mm), streptomycin (9.47-24.07 mm), erythromycin (11.03-26.63 mm) tetracycline (12.10-26.63 mm), methicillin (13.80-22.10 mm) and vancomycin (12.53-25.20 mm). Among the antibacterial drugs tested pefloxacin, cefuroxime, ceftriaxone tetracycline and vancomycin showed maximum zone of inhibition against Streptococcus spp. All the isolates were found to produce lactic acid within 72 hours and the concentration of lactic acid produced increased with time. The concentration ranged from 0.54 g/L to 1.24 g/L. For the haematological studies, wistar albino rats were divided into three groups. The first group of rats was given the standard inoculum of Streptococcus agalactiae only and the second group was given standard inoculum Enterococcus faecium and the last group was given normal saline. Absolute white blood cell counts were significantly elevated after injection as compared with the control. There was reduction of body weight during active infection in those rats infected withEnterococcus faecium and Streptococcus agalactiae due to haemolysis. These organisms were further studied to determine their biodegrading activities on hydrocarbons (diesel, kerosene, crude oil and engine oil) using enrichment medium. The microbial growths were determined using spectrophotometer blanked at 600 nm. The biodegradative activity revealed that E. faecium was an effective degrader of crude oil while engine oil was effectively degraded by S. pyogenes and S. pneumoniae. Kerosene and diesel were degraded effectively by E. faecalis and S. pneumoniae. E. avium and S. equi also showed degradative abilities. It was observed from the result that the length of incubation had significant effect on degradation as well as the cell load. The cells were able to multiply within the days of study, indicating that they were able to degrade and utilize the oil for their growth and development, hence the concomitant increase in the concentration of the broth (turbidity) The level of utilization differed from one microbe to another (due to differences in their growth) and from one hydrocarbon substrate to the other, due to the obvious differences in their molecular sizes. There was gradual increase in the concentration of the broth which indicated bacterial growth hence degradation of hydrocarbons mostly between days 4 and 14 and gradual decline in the concentration of some of the broth suggests decrease in the bacterial population and that the hydrocarbon had been degraded, mostly between days 10 and 13. However, an important limiting factor is the slow rate of degradation which often limits the practicality of using microorganisms in remediating hydrocarbon impacted environment. Further research in this area can make a marked improvement.