Antimicrobial Resistance Trend of Bacteria from Clinical Isolates: An Eight-Year Retrospective Study at Dessie Regional Laboratory, Northeast Ethiopia

For decades, antimicrobials have proven useful for the treatment of bacterial infections. However, the immergence of antimicrobial resistance has become a major challenge to public health in many countries. The aim of this study was to investigate the antimicrobial susceptibility of bacterial isolates from clinical sources. A retrospective analysis of 1711 bacterial isolates was done at Dessie Regional Laboratory in the period 2003 - 2010. Antimicrobial susceptibility tests were done using disc diffusion technique as per the standard of Kirby-Bauer method. Escherichia coli with a figure 446 (26.1%), was the predominant isolate, followed by Staphylococcus aureus 429 (25.1%), Proteus spp. 303 (17.7%) and Pseudomonas spp. 290 (16.9%). These four species made up 85.8% of the organisms isolated from the clinical sources. The bacterial isolates showed high resistance rates to amoxicillin (85.4%) followed by tetracycline (84.1%) and erythromycin (73.5%). E. coli isolates showed resistance rates (>72 %) to amoxicillin, erythromycin and tetracycline. S. aureus isolates had resistance rates of 81.3% and 67.6% to amoxicillin and tetracycline, respectively. Proteus spp. showed resistance of >80% to amoxicillin, erythromycin and tetracycline. High resistance rates to erythromycin (91.6%) and amoxicillin (89.6%) were exhibited by Pseudomonas spp. Aconsiderable degree of resistance rates to tetracycline (85.2%), chloramphenicol (72.8%) and cotrimoxazole (72.5%) were also observed. However, most bacterial isolates were susceptible to ciprofloxacin, norflaxocin and gentamicin with resistance rates ranging between 4 - 9.6%. All bacterial isolates showed high multiple antimicrobial resistances. Increased trend of resistance rates to all antimicrobials except nitofurantoin was demonstrated. Four of the most frequently isolated bacteria exhibited high rates of resistance to amoxicillin, chlorampheniciol, cotrimoxazole, erythromycin and tetracycline. Ciprofloxacin, gentamicin and nitrofurantoin remain antimicrobials of choice for empirical therapy of infections in the study area. Increased trend of antimicrobial resistance and high multiple antimicrobial resistance calls for periodic screening for antimicrobial resistance for empirical therapy.Key words: antimicrobial resistance, bacterial isolates, disc diffusion technique, retrospective analysis, northeast Ethiopi