Antibiotic sensitivity and plasmid profiles of Pseudomonas aeruginosa

Objective: To determine the susceptibility of Pseudomonas aeruginosa to commonly used antibiotics and to study the relationship between antibiotic resistance and the plasmid profiles of the organism. Design: Cross sectional study Setting: Samples of burns, wound pus, urine, blood, sputum, stool and aspirates were obtained from Harare Hospital (n=120) and Parirenyatwa Hospital(n=80). Subjects: Male and female patients either admitted or attending clinics. Main Outcome Measures: P. aeruginosa isolates obtained were resistant to commonly used antibiotics in this environment. The resistance may be plasmid-dependent. Results: P aeruginosa is prevalent in burns (76.7%) and wounds (67.5%) and in their respective hospital wards. The isolates of P. aeruginosa were resistant to gentamicin (65.5%); carbenicillin (61.9); polymyxin-b (53.0%); ciprofloxacin (61.1%) and ceftriazone (70.8%); but showed high sensitivity to tazocin (89.4%) and nalidixic acid (59.3%) and cotrimoxazole (54.9%). All the isolates resistant to the antibiotics tested possessed plasmid DNA. Strains with four plasmids of molecular weight of approximately, 1.5 x 10⁶, 1.8 x 10⁶, 2.9 x 10⁶ and 7.4 x 10⁶ Da showed multiple resistance to the drugs that were tested. Conclusion: This study reveals an emergence of multiple antibiotic-resistant strains of P. aeruginosa. The traditional drugs gentamicin, carbenicilllin, ciproflaxacin, and polymyxin-b used for treatment of P. aeruginosa infections may no longer be reliable. Therefore, a newer drug such as tazocin and other rarely used drugs such as nalidixic acid should be considered for P. aeruginosa antibiotic therapy.