Trimethoprim/sulfamethoxazole for Acinetobacter spp.: A review of current microbiological and clinical evidence

Clinicians nowadays are confronted with an epidemic of multidrug-resistant (MDR) Acinetobacter infections and are forced to consider every treatment alternative, including older antibiotic agents, not conventionally used. This review aimed to evaluate the published evidence on the antimicrobial activity and clinical effectiveness of trimethoprim/sulfamethoxazole (TMP-SMX) against Acinetobacter spp. Selected in vitro studies included antimicrobial surveillance reports, microbiological studies regarding the activity of TMP-SMX against MDR Acinetobacter isolates, and clinical studies published after the year 2000. Non-susceptibility rates for Acinetobacter spp. in surveillance studies ranged from 4% to 98.2%; in 23 of 28 studies, non-susceptibility to TMP-SMX was >50% and in a subset of 15 studies non-susceptibility was >70%. In studies regarding MDR Acinetobacter spp., non-susceptibility rates ranged from 5.9% to 100%; however, 19 of 21 studies reported >70% non-susceptibility. Extensively drug-resistant Acinetobacter baumannii complex had total (100%) resistance in five of six studies. Carbapenem-resistant Acinetobacter spp. had non-susceptibility rates to TMP-SMX of >80% in 22 of 26 studies. One study on polymyxin-resistant A. baumannii showed a susceptibility rate of 54.2% (13/24). Only seven case reports evaluated TMP-SMX for Acinetobacter spp. infections, mainly in combination with other agents; all cases were deemed therapeutic successes. Although TMP-SMX is not usually active against Acinetobacter spp., it might be considered in cases where there are no other options.