Evaluation of Resistance in Clinical Isolates of E. coli, S. aureus, and P. aeruginosa against β-lactam Antibiotics and Gentamicin

Abstract

Background: To study the susceptibility pattern of β-lactam antibiotics and gentamicin in pathogenic clinical isolates with reference to the site of infection. Methods: In this descriptive study three prevalent clinical isolates were selected i.e., Escherichia coli, (n = 203) Staphylococcus aureus (n = 194) and Pseudomonas aeruginosa (n = 106). These were isolated from urine, pus, high vaginal swabs, and a miscellaneous group, comprised of blood and fluid. The antibiotics included in the study were from β-lactam group and gentamicin. Results: E. coli was mostly isolated from urine (n = 124), while S. aureus and P. aeruginosa were mostly isolated from pus samples. Among β-lactams the activity of imipenem was highly sensitive against all isolates as only 2.66 % of E. coli, 5.8% of S. aureus and none of P. aeruginosa isolates were resistant to imipenem. Highest resistance in these isolates was against ampicillin, where S. aureus was rather sensitive to this drug (44% ) as compared to E. coli (15% sensitivity) and P. aeruginosa (13%). Staphylococcus aureus isolates were more sensitive to amoxicillin/clavulanate (75%) as compared to E. coli (58%) & P. aeruginosa (41%). Pipracillin/tazobactam and 3rd generation cephalosporins were also comparatively more sensitive (10-20% resistance). Staphylococcus aureus isolates showed 76% sensitivity against gentamicin while 72% of P. aeruginosa isolates and 65% of E. coli isolates were sensitive to this drug.