Antibiotic resistance among heterotrophic bacteria in Lagos Lagoon, Nigeria

Abstract

Antibiotic-resistant bacteria in the aquatic environment are considered reservoirs for drug-resistant genes. Therefore, culturable heterotrophic bacteria isolated from Lagos Lagoon surface waters between 2011 and 2012 were screened for their susceptibility to 14 commonly used antibiotics belonging to six major classes. The sampling stations had temperature, pH and salinity ranges of 28 to 33 °C, 8.2 to 8.1 and 14.6 to 20.1, respectively. The high microbial load of the sampling stations was evident, the mean most probable number being between 400 and 1 100 per 100 ml. The bacteria encountered were Pseudomonas sp., Citrobacter sp., Vibrio sp., Micrococcus sp., Streptococcus sp., Bacillus sp. and Aeromonas sp. Resistance to the tested antibiotics was widespread; the incidences of isolates resistant to ampicillin (55.3%) and amoxicillin (52.6%) were the most common, while all tested isolates were susceptible to the fluoroquinolones, with the exception of sparfloxacin which was resisted by 26.3% of the isolates. The frequency of resistant isolates for aminogylcosides, macrolides, phenicols and sulfonamides ranged between 2.6% and 18.4%. The most resistant strain had a multiple antibiotic resistance value of 0.57. Although susceptibility to some drugs was noted, resistance to the beta-lactam antibiotics suggests that bacteria in Lagos Lagoon harbour genes for resistance.

Keywords: antibiotic susceptibility, aquatic bacteria, multiple antibiotic resistance, surface water

African Journal of Aquatic Science 2013, 38(3): 331–336