Background: Aeromonas species can cause a wide spectrum of illnesses varying from intestinal to extra intestinal
and vary in their susceptibility to different antibiotics. The current study was undertaken to characterize the third
generation cephalosporin-resistant strains of
Aeromonas spp. which were isolated from stool specimens.
Methods: Out of a total of 2780 stool samples, 29
Aeromonas spp. were identified, out of which, 9 were resistant
to ceftriaxone by the Kirby-Bauer antibiotic testing method. These strains were subjected to minimum inhibitory
concentration (MIC) determination by agar dilution for ceftriaxone. Phenotypic and genotypic testing of AmpC
beta-lactamase and extended spectrum beta-lactamase (ESBL) were performed. Gene transfer was carried out to
demonstrate transmissibility of these genetic elements by conjugation experiments.
Results: Out of the 29 strains, 9 showed MIC of ≥4 μg/ml. Seven out of 9 showed presence of blaCTX-M, while 2
more strains showed the presence of inducible AmpC beta-lactamase and presence of MOX gene. Gene transfer
experiments showed that these elements were transmissible to recipient (
Escherichia coli
J53 strain) in the presence
of ceftriaxone.
Conclusions: Dissemination of these resistance determinants like plasmids is pivotal in the spread of these
resistance genes into the aquatic environment into organisms like
Aeromonas. This may further limit the future
use of antibiotics for the treatment of diarrhoeal diseases. Hence, detection and antibiotic susceptibility testing
of
Aeromonas spp. should be performed when isolated from stool samples.
