Multi-drug resistance, verotoxin production and efficacy of crude stem bark extracts of Curtisia dentata among Escherichia coli (non-O157) and Acinetobacter species isolates obtained from water and wastewater samples

Abstract

Drug resistant diarrhea and nosocomial infections caused by verotoxic Escherichia coli and some Acinetobacter species has posed serious therapeutic challenges, especially in developing countries. The aim of this work is to investigate multi-drug resistance, verotoxin-production and susceptibility of E. coli and Acinetobacter spp. isolated from some water samples to crude stem bark extracts of Curtisia dentata. Culture of 62 water samples on Brilliance E. coli coliform selective medium (BECSM, Oxoid), Eosin Methylene Blue (EMB) agar, or Baumann’s enrichment medium (BEM) and Leeds Acinetobacter Medium (LAM) yielded 69 isolates of E. coli and 41 isolates of Acinetobacter spp. with 26 (53.06%) of the E. coli and 6 (14.63%) of the Acinetobacter haemolyticus isolates producing verotoxins, and no Acinetobacter lwoffii isolate produced the toxins. Multi-drug resistance index (MDRI) values of isolates ranged between 7 to 33.00% for both isolates with 12 (17.39%) of the E. coli and 10 (24.39%) of the Acinetobacter spp. resistant to 3 or more classes of the antibiotics. C. dentata stem bark extracts demonstrated low minimum inhibitory concentration (MIC) values of 150 to 300 µg/ml for E. coli and 150 to 2000 µg/ml for Acinetobacter spp. The plant also contained saponins, tannins, glycosides, anthraquinones, flavonoids, steroids, and phenols. The presence of verotoxic multidrug resistant E. coli and Acinetobacter spp. in the environments investigated calls for further surveillance of more water bodies and other environments. Proactive control measures need to be in place to curtail possible contamination of food and drinking water sources. Purification of C. dentata phytoconstituents, toxicological as well as in vivo studies for their antimicrobial potentials against pathogenic bacteria, should be carried out with a view of utilizing the plant in developing novel antibiotic substances.