Treatment of Acinetobacter Infections

• Acinetobacter is a gram-negative coccobacillus
• resistance pattern in Malaysia:

First Line Therapy

• broad-spectrum cephalosporin (ceftazidime or cefepime), a combination beta-lactam/beta-lactamase inhibitor (ie, one that includes sulbactam), or a carbapenem (eg, imipenem, meropenem, or doripenem).
• Emergence of resistance during therapy has been observed with ampicillin-sulbactam, cephalosporins, and carbapenems when used as single agents . For this reason, these agents are sometimes used in combination with an antipseudomonal fluoroquinolone or an aminoglycoside. 
• However, there are no clinical data demonstrating that combination therapy either reduces the risk of emergent resistance during therapy or improves clinical outcomes in cases of Acinetobacter infections

Alternative for Resistant Agent

• Polymyxins (polymyxin B and colistin [polymyxin E]) are the most commonly used agents for Acinetobacter isolates resistant to first-line agents
• Colistinhas been used with some success for the treatment of Acinetobacter pneumonia, bacteremia, and meningitis
• In a meta-analysis of four studies (244 patients) evaluating treatment of ventilator-associated pneumonia due mainly to Acinetobacter baumannii but also Pseudomonas aeruginosa, clinical improvement rates, 28-day mortality, and ICU lengths of stay with intravenous colistin were similar to those observed with a comparator agent (carbapenem or high-dose ampicillin-sulbactam)

 Combination therapy

• Combination antimicrobial therapy is used to increase the likelihood of adequate empiric antibiotic coverage before drug susceptibility testing results are known, to decrease the risk of emergent resistance, and to improve outcomes in multidrug or extensively drug-resistant infections
• but there are no definitive clinical data to support its use for these purposes. 
• Combination therapy (colistin plus Rifampicin) did not decrease the 30 day mortality rate (43.3 versus 42.9 percent with colistin alone) or the infection-related death rate (21.5 versus 26.6 percent) despite increasing the likelihood of microbiological cure (60.6 versus 44.8 percent)
• Other combinations that have favorable effects on multi- and extensively-drug resistant isolates in vitro or in small case series include a carbapenem with colistin and tigecycline with colistin
• However, some recommends that the use of a single agent is not adequate, particularly since resistance can develop during therapy leaving no therapeutic alternatives.

Summary of Treatment

 NAG 2014

ICU Antibiotic Guideline 2012

 References:

1. www.uptodate.com
2. NAG 2014
3. Malaysian ICU Antibiotic Guideline 2012