Comparison of Two Tests for Detection of Extended – spectrum β – lactamase in Clinical Isolates

Abstract

Extended spectrum β-lactamase (ESBLs) producing bacteria are of great public health concern. It is also recognized that detection of ESBLs constitutes a problem for microbiological laboratories since detecting methods used in this context are not sensitive enough to deal with all clinical isolates. The aim of this study was to compare two methods used for detection of ESBLs, the double disc synergy test (DDST) and phenotypic confirmatory test (PCT) on the recovered isolates. Clinical specimens, including; urine, sputum, blood, wound swab, ear swab, high vaginal swab, and knee aspirate were collected from hospitalized patients in Khartoum State. The causative agents were characterized by phenotypic procedures and molecular typing. ESBLs were detected by DDST and PCT methods. Out of 120 collected specimens, 54 bacterial species were recovered. These are E. coli (46.3 %), K. pneumoniae (24.1%), K. oxytoca (3.7%), P. mirabilis (16.7%), P. vulgaris (7.4%) and E. cloacae (1.9%). Of these 16 and 17 isolates were found to be ESBLs- producers when tested by DDST and PCT respectively. On the other hand, 18 out of 54 isolates were ESBLs-producers when examined by PCR. The study concluded that there is no significant difference between DDST and PCT. Moreover, the two tests were rapid, easy to perform and cost-effective in screening ESBLs.