Microbiology
Gram-negative rods (when growing) and coccobacillus (when not) and includes A. baumannii (most common human pathogen), A. haemolyticus, A. junii, A. johnsenii, A. lwoffi, A. radioresistens, and 15 others. (Review).
Epidemiologic Risks
Very hardy, found in diverse water and moist soils.
Usually a complication of hospitalization or nursing homeization (my neologism, if you use it you owe me a dollar). There is a particularly resistant strain of A. baumannii found in soldiers from Iraq and Afghanistan (PubMed) for which imipenem is the most reliable agent; may want to consider colistin. As of 2018 (Reference), however, there is little hope that our troops will be returning any time soon but the wounded can bring this bug home with them, yet another Homeland Security failure.
It is an increasing nosocomial/nursing home pathogen, often multi-drug resistant (PubMed).
Occasionally airborne spread.
Syndromes
Usually hospital-acquired infections of all types, most commonly pneumonia and bacteremia.
Reports of community-acquired pneumonia, associated with poor hosts (they serve Bud light) and warm, wet environments (PubMed).
Treatment
Treatment reviewOften resistance emerges during therapy with third-generation cephalosporins, know your local susceptibilities. Generally, Extended infusion imipenem/meropenem, cefepime, and ciprofloxacin are the best bet. However, resistant A. baumannii are rapidly increasing, in some areas as of 2006 as high as 40% resistant to beta-lactams.
For the MDR strains, consider tigecycline (PubMed) and colistin, amikacin, or minocycline (PubMed), which is not better or worse than tobramycin for efficacy or toxicity (Reference). Carbapenem-resistant organisms may be treated best with ampicillin/sulbactam (oddly it is susceptible to the sulbactam component of Unisin) > colistin (PubMed). Resistance may develop to tigecycline while on therapy (PubMed).
In vitro, colistin/meropenem, colistin/rifampicin, colistin/minocycline, and minocycline/meropenem are synergistic (Reference).
For colistin-resistant, perhaps the best option is colistin, a carbapenem, and ampicillin-sulbactam (PubMed ).
But get this. Colistin resistant A.baumannii has better outcomes than colistin sensitive strains, likely due to a fitness cost of colistin resistance. BUT. Adding meropenem to colistin in treating colistin-resistant strains increased mortality. Yeah. You read that right (PubMed).
Although in a randomized clinical trial, rifampin added nothing to colistin (PubMed) nor does adding meropenem (PubMed).
Colistin, and other antibiotic resistance, varies around the world, China the most, Germany the least (Pubmed).
Notes
Usually sensitive to third-generation cephalosporins, carbapenems, and quinolones.
As to its name, it means non-moving (akinetic)and the Wikipedia notes "The first element acineto-appears as a somewhat baroque rendering of the Greek morpheme ακίνητο-, commonly transliterated in English is akineto-, but actually stems from the French cinetique and was adopted directly into English."
Curious Cases
Relevant links to my Medscape blog
Last Update 12/18/20.