Acinetobacter: Bactrim Dose

• 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.

Dosing

• No specific dosing based on treatment guideline due to high level of resistance and lack of studies
• Some protocols do use combination of doxycycline 100 mg twice daily with Trimethoprim sulphamethoxazole in a dose of 80 mg / 400 mg twice daily (modified according to renal functions ) for 7 days.
• Dosing can also be extrapolated from the general dosing guide, ie treat as severe infection (bacterial meningitis) 10-20 mg TMP/kg/day IV divided q6-12hr
• Another guide do recommend use of TMP dose of 160mg TDS-QID for acinetobacter related pulmonary infection

Recommendation

• Although TMP-SMX is not usually active against Acinetobacter spp., it might be considered in cases where there are no other options or based on sensitivity
• In view of higher resistance rate and lack of specific dose recommendations, dosing at a higher dose range can be considered for sensitive cases.

References:

1. Doxycycline and Co-trimethoxazole: A new combination for treatment of MDR Acinetobacter baumannii. Does it work? Int.J.Curr.Microbiol.App.Sci (2016) 5(1): 157-164
2. https://www.researchgate.net/publication/22755471_Intravenous_trimethoprim-sulfamethoxazole_in_the_treatment_of_serious_infections_in_children
3. Infection Control in the ICU Environment, By Robert A. Weinstein, Marc Bonten
4. http://reference.medscape.com/drug/bactrim-trimethoprim-sulfamethoxazole-342543