Identification and antibiotic susceptibility of bacterial isolates from burned patients

We retrieved bacterial blood isolates from 397 adult burned patients admitted over a 7-year period. Sixty-two patients (15.6 per cent) developed true-positive bacterial blood cultures (judged non-contaminants), and of these 30 (48.4 per cent) expired. Pseudomonas aeruginosa (24 isolates), Staphylococcus aureus (19) and Klebsiella pneumoniae (19) were the most frequent isolates. In vitro susceptibilities of 149 isolates were determined to 12 antibiotics (gentamicin, amikacin, ticarcillin, piperacillin, mezlocillin, azlocillin, cefazolin, cefotaxime, ceftazidime, cefoperazone, thienamycin and ticarcillin-clavulinic acid) using agar diffusion assay. Thienamycin proved the most active agent (97 per cent of isolates susceptible). Cefoperazone was the most active cephalosporin (95 per cent susceptible). Twenty-eight organisms demonstrated multiple drug resistance; patients with such organisms had a 71 per cent mortality. Thienamycin was the most active agent against such isolates (27/28 susceptible). Susceptibilities of all 149 isolates to combinations of antibiotics were calculated, assuming no synergism or antagonism; some combinations of third-generation cephalosporins with the newer penicillins may prove to be as effective as combinations including aminoglycosides.