Abstract

Aeromonas producing extended-spectrum ß-lactamases (ESBLs) have been reported in many countries, but there is no information on the prevalence of ESBL-producing clinical Aeromonas in South African. A total of 230 isolates of Aeromonas hydrophila were isolated from 660 stool samples and 709 water samples collected in different municipalities in Limpopo province, South Africa over a period of three month. Isolates were screened for the production of ESBLs by the double disk diffusion test and for AmpC production by assessing resistance to cefoxitin. bla_SHV,bla_TEM , bla_CTX-M and bla_CMY-2 were isolated from all ESBL-positive and cefoxitin-resistant isolates. Only 21 isolates were found to be ESBL producers. All 21 isolates were screened for the production of bla_SHV, bla_TEM, bla_CTX-M and bla_CMY-2 ESBLs. Only (1/21) was found to produce bla_{TEM 63} and bla_CMY-2. All transconjugants were resistant to amoxicillin, piperacillin, the cephalosporins and aztreonam but remainedsusceptible to cefoxitin and imipenem. Crude extracts of ß-lactamase-producingtransconjugants were able to reduce the diameters of inhibition zones around disks containing penicillin, but had no effect on such zones around cefoxitin, imipenem and amoxicillin-clavulanate disks. In conclusion, the occurrence of ESBLs in A .hydrophila emphasizes the importance of constant surveillance of clinical isolates to determine the prevalence of antibiotic resistance genes.

Key words: Extended-spectrum b-lactamases- Aeromonas hydrophilia , antibiotics , resistance.