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Acinetobacter: an old friend, but a new enemy

Many misconceptions concerning acinetobacter still appear repeatedly in the scientific and medical literature. Chief among these are the statements that A. baumannii is ubiquitous or highly prevalent in nature, that it can be recovered easily from soil, water and animals, and that it is a frequent skin and oropharyngeal commensal of humans. While these statements certainly apply to members of the genus Acinetobacter when considered as a whole, A. baumannii (and its close relatives of clinical importance) are not ubiquitous organisms. While it is certainly true that A. baumannii can be isolated from patients and hospital environmental sources during outbreaks, this species has no known natural…

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 Acinetobacter – the Bad, the Awful, and the Downright Ugly

Colonization with Acinetobacter spp. is relatively common in healthy individuals (15-43%), but increases substantially in hospitalized or other at-risk patients (up to 75%). Risk factors for A. baumannii colonization include intensive care unit (ICU) stay, recent surgery, mechanical ventilation, cancer, immunosuppressive treatment, presence of a central venous catheter, dialysis, and previous treatment with β-lactams (especially carbapenems) or fluoroquinolones. Differentiating between colonization and infection, however, is quite complex—especially in individuals in the ICU or who are on ventilators.

Articles of Interest

Another resistant bug rising: Acinetobacter

Because MRSA is a Gram-positive, we don't talk much here about the Gram-negatives — the two categories of bacteria have different cell-wall structures and thus are treated using different categories of drugs. (That structural difference causes them to react in different ways to a stain invented by a scientist named Gram in the 19th century.) But the resistance situation with Gram-negatives is at least as dire as with MRSA, possible more so, because there are fewer new drugs for Gram-negatives in the pharmacology pipeline (as discussed in a New Yorker article by Dr. Jerome Groopman last year.)

Clinical and Pathophysiological Overview of Acinetobacter Infections: a Century of Challenges

Acinetobacter is a complex genus, and historically, there has been confusion about the existence of multiple species. The species commonly cause nosocomial infections, predominantly aspiration pneumonia and catheter-associated bacteremia, but can also cause soft tissue and urinary tract infections. Community-acquired infections by Acinetobacter spp. are increasingly reported. Today, Acinetobacter infections have spread rapidly through hospitals across the globe. The highest density of infections occurs in intensive care units.

Multidrug Resistant Acinetobacter

Emergence and spread of Acinetobacter species, resistant to most of the available antimicrobial agents, is an area of great concern. It is now being frequently associated with healthcare associated infections.

Pan-resistant?? The rise of Acinetobacter

In the all-star annals of resistant bugs, A. baumanii is an underappreciated player. If people – other than, you know, disease geeks – recognize it, that is because it's become known in the past few years for its propensity to attack wounded veterans shipped to military hospitals from Iraq and Afghanistan, earning it the nickname "Iraqibacter."

The Invisible Enemy

In the taxonomy of bad bugs, acinetobacter is classified as an opportunistic pathogen. Healthy people can carry the bacteria on their skin with no ill effects – a process known as colonization. But in newborns, the elderly, burn victims, patients with depressed immune systems, and those on ventilators, acinetobacter infections can kill. The removal of Gadsden's spleen and the traumatic nature of his wounds made him a prime target.

Treatment of Acinetobacter Infections

Acinetobacter infections remain difficult to treat. The prevalence of drug-resistant strains is increasing, and treatment options are increasingly limited. Effective therapy remains likely when the organism is proven to be susceptible. Recent data would suggest that, for some agents, a single testing method may result in incorrect susceptibility results and lead the clinician to select a potentially ineffective agent. Because of some of the unusual and potentially toxic options, one must maintain a high index of suspicion for A. baumannii infection and select empirical therapy wisely.

Resources

CDC

Outbreaks of Acinetobacter infections typically occur in intensive care units and healthcare settings housing very ill patients. Acinetobacter infections rarely occur outside of healthcare settings.

Microbe Wild

Acinetobacter is a genus of opportunistic pathogens in the proteobacteria group, species of which are distributed in widespread, diverse habitats. It has garnered media attention because of an outbreak among soldiers in Iraq who contracted the species Acinetobacter baumannii.

StatPearls

Acinetobacter gained clinical significance in the 1960s with the increasing growth of Intensive care units at hospitals. Though Acinetobacter is an organism of low virulence, its ability to survive desiccation and persist in the environment for an extended duration of time makes it easily transmissible in the healthcare setting. Nosocomial spread by healthcare personnel, respiratory equipment like ventilators, and other devices has been reported frequently.