Antimicrobial susceptibility profile of isolates of Aeromonas hydrophila from different sources: use of amylase activity as end-point indicator

Abstract

Antimicrobial susceptibility profile of 45 Aeromonas hydrophila isolates (from different sources) to 11 commonly used antimicrobial agents was determined by agar diffusion technique. Minimal inhibitory concentrations (MICs) of antimicrobial drugs were also determined using amylase property of Aeromonas as end-point indicator in broth dilution models. Results showed that there was no significant difference in the antimicrobial susceptibility of Aeromonas from clinical and other sources (P > 0.05). All the isolates (100%) were susceptible to quinolones (Ciprofloxacin and Ofloxacin), Gentamicin and Nitrofurantoin. Over 80% of the isolates were susceptible to Tetracycline, Streptomycin, Nalidixic acid and Ceftazidime. Ofloxacin and Gentamicin had the lowest “MIC90” values (0.25μg/ml and 0.5μg/ml respectively). The isolates were markedly resistant to Ampicillin (42 or 93%), with “MIC90” value of 128μg/ml; forty (89%) of the 45 isolates produced detectable levels of β-lactamase enzyme. The use of Amylase activity of Aeromonas for MIC determination was comparable, in efficiency, with the conventional visual estimation in broth dilution model.

Keywords: Antimicrobial susceptibility, amylase indicator, Aeromonas hydrophila

Journal of Biomedical Investigation Vol. 4 (2) 2006 pp. 49-53