Susceptibility patterns and cross-resistance of antibiotics against Pseudomonas aeruginosa isolated from burn patients in the South of Iran.

Pseudomonas aeruginosa plays a prominent role in serious infections in burn patients. Rapid acquisition of multi-drug resistance leads to high morbidity and mortality, especially in burn centers. Ten antibiotics, which were widely used in our burn patients were selected. MICs for imipenem, mropenem, cefepime, ceftazidime, cafoparazone/sulbactam, ticarcillin/clavulanate, piperacillin/tazobactam, ciprofloxacin, tobramycin and amikacin to 70 strains of P. aeruginosa, which were isolated from burn patients were determined by the E-test method (AB Biodisk, Sweden). Extended-spectrum beta-lactamase, group I inducible beta-lactamases and metallo-beta-lactamase activities were also determined. Imipenem and meropenum were the most active in vitro antibacterial agents followed by ciprofloxacin (p<0.05), whereas, ticarcillin/clavulanate was the least active. Almost all (98-100%) of the resistant isolates also showed cross-resistance to cefepime. The majority of imipenem and meropenem resistant isolates (85-100% and 76-100%) demonstrated cross-resistance to all the other antibiotics. ESBLs were detected in only three (4.3%) isolates, whereas, inducible beta-lactamase was observed in eight (11.4%) isolates. Metallo-beta-lactamase was detected in none of the isolates. Almost all of the antibiotic resistant isolates also showed cross-resistance to the majority of penicillins and cephalosporins with or without beta-lactamase inhibitors, from which ticarcillin/clavulanate demonstrated this phenomenon at the highest level.