The presence of GES enzymes in Pseudomonas aeruginosa strains isolated from patients in Warsaw hospitals

Abstract number: R2146

Objectives: The GES-type enzymes have been found mainly in P. aeruginosa, but such enzymes have been also isolated from Enterobacteriaceae. Generally, genes coding GES b-lactamases are located on class 1 integrons. The aim of this study was to identify strains producing GES-type ESBLs, among P. aeruginosa isolates from two Warsaw hospitals.

Methods: The MDR P. aeruginosa strains (n = 332) were isolated from clinical specimens obtained from patients in two Warsaw hospitals. The MICs values of b-lactams were determined by agar dilution method, according to CLSI recommendation. The presence of ESBLs was detected by a double-discs synergy test (DDST) with inhibitors: clavulanic acid, sulbactam, tazobactam and imipenem. The presence of integrons and genes coding GES-type ESBLs was detected by PCR. Gene cassettes were identified by sequencing of the obtained amplicons. Standard plasmid analysis was performed.

Results: The ESBL-type enzymes were detected among 53 isolates by DDST. Eighteen out of all tested isolates were resistant to all b-lactams. These strains (n = 71) were screened for the presence of genes coding ESBL-type enzymes. In 8 isolates (seven from hospital A and one from hospital B) bla genes coding GES-type enzymes were identified. All found blaGES genes are located in class 1 integrons. Moreover, seven of them are present on plasmid. Among strains from hospital A enzymes as GES-1 (in 5 strains), GES-5 (in one) and the new ESBL-type b-lactamase GES-15 were detected. The complete nucleotide sequence of blaGES-15 was determined (NCBI GenBank Acc. No GU208678). Sequencing showed that GES-15 was identical to GES-5 except one amino acid. All of above-mentioned seven strains are resistant to ceftazidime and cefepime. The GES-15 carrying strain exhibited the most clear inhibitor-sensitive phenotype. Moreover, blaGES-1 gene in one strain from hospital B was identified, also in this case blaGES-1 gene is located in class 1 integron on plasmid.

Conclusions: The new extended-spectrum b-lactamase GES-15 encoded by class 1 integron-located gene was found in P. aeruginosa clinical isolate. Moreover, the GES-5 producing P. aeruginosa strain was identified in Poland for the first time. The presence of plasmid-located blaGES-1, blaGES-5 and blaGES-15 genes, within integrons in 8 clinical isolates from two hospitals suggests the possibility of spreading these ESBLs in Polish hospitals.