Antibiotic sensitivity and plasmid profiles of Pseudomonas aeruginosa

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.

Cross sectional study

Samples of burns, wound pus, urine, blood, sputum, stool and aspirates were obtained from Harare Hospital (n = 120) and Parirenyatwa Hospital(n = 80).

Male and female patients either admitted or attending clinics.

P. aeruginosa isolates obtained were resistant to commonly used antibiotics in this environment. The resistance may be plasmid-dependent.

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); polymyxinb (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 10(6), 1.8 x 10(6), 2.9 x 10(6) and 7.4 x 10(6) Da showed multiple resistance to the drugs that were tested.

This study reveals an emergence of multiple antibiotic-resistant strains of P. aeruginosa. The traditional drugs gentamicin, carbenicillin, 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.