Phenotypic and Molecular Detection of Extended Spectrum β-Lactamase in Pseudomonas aeruginosa

Abstract

Detection of extended spectrum β-lactamases (ESBLs) is a major challenge for the clinical microbiology laboratory due to the variable affinity of these enzymes for different substrates and inoculums effect. The present study was designed to detect the ESBLs in Pseudomonas aeruginosaisolates from hospitalized patientsand to evaluate their susceptibility pattern to antibiotics. In this study, 350 specimens were collectedincludingwound swabs, eye swabs, nasal swabs, ear swabs, urine and sputum from hospitalized patientsin Khartoum State hospitals. The specimens were cultured on appropriate culture media.The isolates were identified by their colonial morphology, Gram’s stain and biochemicalidentification tests using the API 20E identification system. The presence of ESBL enzymes weredetected by phenotypictechnique using double disc synergy and combined disc methods. TEM, SHV, and CTX-M genes were detected by polymerase chain reaction technique. The results revealed that 65 clinical isolates of Ps. aeruginosa were recovered. Only3(4.6%) of the isolateswere ESBL positivewhen examined by double disc synergy test and combination disc test. Detectionof ESBLgenes by PCR showed that only the gene CTX-M waspresent. It is concluded that Ps. aeruginosa in general has ability to produce ESBLs as well as members of Enterobacteriaciae, but in limited cases. Further studies utilizing multiplex PCR for the detection TEM, SHV and CTX-M genes in ESBL producing Ps. aeruginosa are highly recommended.