Detection of blaSHV and blaTEM beta-lactamase genes in multi-resistant Pseudomonas isolates from environmental sources

The activity of 13 antimicrobials was studied, to determine multiple antimicrobial resistances, against 208 Pseudomonas strains (125 Pseudomonas sp and 83 Pseudomonas aeruginosa) isolated from river and aquaculture samples. Isolates were confirmed with API 20 NE. Isolates from both sources reported high resistance rates for similar antibiotics. These were: Ampicillin (100, 100%), cefuroxime (96.8, 81.9%), streptomycin (93.6, 78.6%), cefotaxime (93.6, 77.1%), for river water and aquaculture samples respectively. While resistances were high for ofloxacin, norfloxacine, mezlocillin, ceftazidime, kanamycin and enrofloxacine (70 to 85.5%) among the river water isolates, they were moderate among the aquaculture isolates (50 to 69.4%). Ninety seven (97.2%) percent of isolates from river water and 78.9% from aquaculture were resistant to at least three or more antimicrobials and were termed multiresistant. Results of plasmid profiling showed the presence of multiple plasmids ranging in size between 639 and 11845 bp. Preliminary tests for beta-lactamase detection by double-disk approximation were positive with high resistances to imipenem, aztreonam, cefpodoxime and cefotaxime. PCR of amplified genomic DNA was positive for the detection of blaSHV and bla(TEM) beta-lactamase genes. However, up to 50% of all isolates tested were found to be resistant to the beta-lactamase inhibitor of combination amoxicillin+clavulanic acid. The results infer the presence of multi resistant organisms as well as genes conferring beta-lactamase resistance in environmental samples.