DEVELOPMENT OF RESISTANCE DURING ANTIMICROBIAL THERAPY - A REVIEW OF ANTIBIOTIC CLASSES AND PATIENT CHARACTERISTICS IN 173 STUDIES

The incidence of emergent resistance and clinical factors affecting it s development were evaluated by retrospective review of 173 studies en compassing over 14,000 patients. Eight antibiotic classes and 225 indi vidual treatment regimens were evaluated. Emergent resistance occurred among 4.0% of all organisms and 5.6% of all infections treated. It ap peared to be significantly more frequent with penicillin and aminoglyc oside monotherapy, with significantly lower rates associated with imip enem-cilastatin, aztreonam, and combination therapy. Clinical failure also appeared to be significantly more likely to occur after emergence of resistance among organisms treated with fluoroquinolones or aminog lycosides. Infections associated with higher resistance rates were cys tic fibrosis, osteomyelitis, and lower respiratory tract infections. R esistance was most common in patients in intensive care units or recei ving mechanical ventilation. It was also significantly frequent among studies performed in university or teaching hospitals. Organisms assoc iated with high resistance rates were Pseudomonas aeruginosa, Serratia , Enterobacter, and Acinetobacter sp. Factors such as infection type, underlying diseases, type of institution, and specific pathogens warra nt consideration when examining emergent resistance.