~Dr Cedric Cheung
We all know antibiotic resistance is a major health problem. Take, for example, resistant Acinetobacter baumanii (AB) ventilator-associated pneumonia and bacteremia that are major issues in hospitals all over the world. What should clinicians do when confronted with a sputum or blood culture that grows out multi-drug resistant (MDR) AB? What would you do? Hopefully you would call an ID consult (shameless plug), but what should ID do?
Unlike methicillin resistant Staphylococcus aureus infections where there are many recently developed antibiotics to choose from, the pipeline of novel agents to treat infections due to MDR AB and other gram-negative rods like Klebsiella pneumoniae and Pseudomonas aeruginosa has been dry for decades. We can only resort to dusting off some long forgotten antibiotics like colistin (with all its nephro and neurotoxicity) or as in the December 2014 supplemental issue of Clinical Infectious Diseases, using minocycline (a tetracycline class antibiotic) for resistant AB infection. That’s right, the antibiotic probably best known for treating teenage acne is actually being considered to combat one of the meanest, nastiest scourges of the ICU.
Normally, it is probably best to use combination therapy of a carbapenem or ampicillin/sulbactam and colistin for empiric treatment of AB infection, as in vitro studies have shown synergistic effect. If susceptibility results show sensitivity to ampicillin/sulbactam, cefepime, or a carbapenem, de-escalation to monotherapy is reasonable. However, if the susceptibility report comes back as MDR AB, you’ve got a problem, and this is not an uncommon problem. A study of over 5000 AB isolates collected from 2007 to 2011 from different regions of the world showed alarming resistance rates to ampicillin/sulbactam (75%) , imipenem (63%), cefepime (78%), and amikacin (65%) . Thankfully, colistin still retains consistent activity against AB (99% susceptible), in addition, minocycline susceptibility was found to be decent (79%). Treating MDR AB is complicated, but most likely a combination of colistin plus something can be effective. This is where minocycline could come into play.
In a case series of 55 patients with MDR AB infection , the combination of colistin plus IV minocycline showed the best clinical success (74%). Other smaller case series showed similar results that seem to support the use of minocycline in these difficult to treat infections . In fact, one center is using colistin and minocycline as empiric therapy of AB infections until antibiotic susceptibility is known .
I apologize if this article was a little too “hardcore ID” for you, but my intention is to highlight the difficulties in treating superbugs such as AB and the need for novel treatments. If I ended it here, this would be just another depressing lament about antibiotic resistance. Stay tuned for part 2 of this article, where I will share the exciting story of the discovery of teixobactin published last month in Nature that could be a game changer.
Are resistant “superbugs” a real problem in your facility? Which ones in particular?
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1. Castanheira M, Mendes, RE, Jones RN. Update on Acinetobacter Species: Mechanisms of Antimicrobial Resistance and Contemporary In Vitro Activity of Minocycline and Other Treatment Options. Clinical Infectious Diseases 2014;59(S6):S367-73.
2. Goff DA, Bauer KA, Mangino JE. Bad Bugs Need Old Drugs: A Stewardship Program’s Evaluation of Minocycline for Multidrug-Resistant Acinetobacter baumanii Infections. Clinical Infectious Diseases 2014;59(S6):S381-7.
3. Ritchie DJ, Garavaglia-Wison A. A Review of Intravenous Minocycline for the Treatment of Multidrug-Resistant Acinetobacter. Clinical Infectious Diseases 2014;59(S6):S374-80.
Dr Cedric Cheung Bio
After graduating from Johns Hopkins University Cedric attended Albert Einstein College of Medicine. Fascinated by a 2 foot long Ascaris worm in a jar being passed around in parasitology class, he instantly fell in love with infectious diseases. So after completing his residency in internal medicine from New York University he returned to Einstein for his ID fellowship. He stayed in the Bronx working for St Barnabas Hospital in the Designated AIDS Center caring for HIV patients. He currently the director of HIV services for MSI Professional Services in China.