Thermostability and in-vitro Antibacterial Activity of Aqueous Extracts of Tetrapleura tetraptera Pods on Multidrug Resistant Clinical Isolates

Abstract

The thermostability of aqueous extracts of Tetrapleura tetraptera pods (AETTP) and its in-vitro antibacterial activities on multidrug-resistant (MDR) clinical isolates were carried out using standard bacteriological and disc diffusion techniques. Eleven genera comprising Staphylococcus, Escherichia, Proteus, Streptococcus, Klebsiella, Pseudomonas, Citrobacter, Enterobacter, Salmonella, Enterococcus and Serratia were obtained from the clinical samples. The results showed that between 19 /35 (54.3%) and 30 /35 (85.7%) faecal isolates were sensitive to all the antibiotics, while Streptococcus pyogenes isolated from wound samples were highly sensitive to gentamycin, nalidixic acid, ciprofloxacin and ofloxacin. Less than 31 (32.6%) of the bacteria showed resistance to multiple antibiotics with 19 (20%) showing resistance to ≥ 4 antibiotics. The phytochemical screening and qualitative estimations of AETTP revealed the presence of alkaloids, anthraquinones, tannins, flavonoids, steroids, reducing sugar, saponins, cardiac glycoside and protein in varied concentrations. The MDR bacteria were markedly inhibited by 40 mgml-1 and 80 mgml-1 AETTP kept at 26ºC with inhibitory zones ranging from 10.3 ± 1.0 mm to 17.4 ± 2.2 mm, while decrease in the inhibitory zones were observed when AETTP boiled to 50ºC, 75ºC and 100ºC were used. The AETTP boiled to 1000C immensely lost its antibacterial activities, as ≥ 42.1% of the bacteria were resistant to AETTP. The MIC values of AETTP ranged from 5 to 40 mgml-1, while the MBC values ranged from 20 to 160 mgml-1. The highest MIC of 40 mgml-1 and MBC of 160 mgml-1 were obtained when the AETTP was tested against S. aureus (SAU5) and Salmonella spp (SSS2). Although, AETTP has antibacterial activities on both MDR Gram positive and Gram negative bacteria, could be used to develop a novel and broad-spectrum antibiotic for the treatment of MDR bacterial infections, its antibacterial activities could be markedly lost by high temperature.