Effectiveness of double disc synergy and disc replacement tests in the confirmation of extended spectrum β-lactamases (ESβLS) production

摘要

A total of 500 bacterial isolates (from various sources including stool, urine, sputum, swabs) obtained from Gombe State Specialist Hospital were used for this study. The isolates were separated into Gram positive (200) and Gram negative (300) representing 40% and 60% respectively. Biochemical tests confirmed the Gram negative isolates to be members of the family Enterobacteriaceae which included Klebsiella pneumoniae 60, Escherichia coli 98, Providencia spp. 32, Morganella morganii 32, Shigella spp. 14, Citrobacter freundii 14, Serratia marcescens 10 Salmonella paratyphi A 10, Yersinia enterolitica 8, Proteus vulgaris 4, Salmonella typhi 2 and Pseudomonas aeruginosa 16. Of the 300 Gram negative isolates subjected to screening (using Cefpodoxime (CPX 10μg, Oxoid England) and Cefotaxime (CTX 30μg, Oxoid England} for ESBL-production using the CLSI breakpoint, 250 (83.33%) were found to be positive for ESβLs which included K. pneumoniae 40, E. coli 92, Providencia spp 30, M. morganii 20, P. aeruginosa 14, Shigella spp 14, C. freundii 12, S. marcescens 6, Y. enterocolitica 6, S. paratyphi A 10, P. vulgaris 4 and S. typhi 2. However, one hundred and sixty four, 164 (65.6%) were confirmed (using Amoxicillin-clavulanate, 30μg Oxoid England) to be ESβL-producers based on Disc Replacement Method (DRM) which included K. pneumoniae 32(19.50%), E. coli 52(31.71%), Providencia Spp 20(12.20%), M. morganii 16(9.76%), P. aeruginosa 8(4.88%), Shigella Spp 12(7.32%), C. freundii 6(3.66%), S. marcescens 4(2.44%), S. paratyphi A 8(4.88%), Y. enterocolitica 6(3.66%), P. vulgaris 0, and S. typhi 0. This is higher than those confirmed by Double Disc Synergy Test (DDST) where only 96(38.4%) of ESBL-producers were detected which included K. pneumoniae 20(20.83%), E. coli 26(27.08%), Providencia Spp 14(14.58%), M. morganii 12(12.50%), P. aeruginosa 4(4.17%), Shigella Spp 4(4.17%), C. freundii 2(2.08%), S. marcescens 2(2.08%), S. paratyphi A 4(4.17%), Y. enterocolitica 6(6.25%), P. vugaris 0, and S. typhi 2(2.08%).The prevalence of ESBL producers detected in Gombe State Specialist Hospital based on this research was high and DRM (65.6%) was found to be a more effective confirmatory method than DDST (38.4%) with calculated value (17.78) being greater than the table value (11.07) at P=0.05 using Chi-square statistical analysis.