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Multi-resistant Acinetobacter baumannii
[Archive CMO Feature - Last updated: 09/02/05]

  • Last modified date:
    14 May 2007

The January 2004 edition of the Health Protection Agency's Communicable Diseases Report highlighted a potential risk for healthcare associated infection from an organism called Acinetobacter baumannii, which is resistant to many antibiotics.

Acinetobacters are environmental organisms that are widespread both in and outside healthcare premises. The main species associated with human infection is Acinetobacter baumannii.

In general, patients are more likely to be colonised rather than infected with A. baumannii. Susceptible patients are usually immunosuppressed or seriously ill due to other causes. Acinetobacters can occasionally cause infection in hospital patients- especially those who are already very ill, such as intensive care unit patients. It should be noted that the number of patients with serious bloodstream infections due to A. baumannii is much lower than Staphylococcus aureus (MRSA).

In the UK, the A. baumannii organism is not often a cause of death, but may complicate therapy. There have also been recent reports of more virulent strains circulating in France.

The Health Protection Agency is planning to review the situation in English acute NHS Trusts early in 2004 and is also preparing interim guidance on the control of the multi-resistant acinetobacter.

Frequently Asked Questions about Acinetobacters

What are acinetobacters?

Small gram negative cocco-bacilli- environmental organisms that were formerly classified with the Neisseriacae.

A. baumannii is widely prevalent in static water. It is frequently found in the hospital environment and easily cultured from fomites and other equipment, particularly in an outbreak situation.

What causes the spread of these organisms?

Healthcare associated infections can be caused by a variety of pathogenic micro-organisms. Unfortunately, most of these infections are not preventable and there are many contributory factors. In particular, advances in medical treatments that have improved survival rates can at the same time leave patients more vulnerable to infection.

Are they virulent?

Acinetobacters are organisms of low virulence. Most commonly, they are found colonising the skin, respiratory tract and urine of patients. Those who are most susceptible are: immunosuppressed; in intensive care and similar high-density environments; and/or on broad spectrum antibiotics, particularly those with little activity against A. baumannii.

Acinetobacters are occasionally invasive, causing wound infections, nosocomial pneumonia and urinary infection. They can cause infections in hospital patients, especially those who are already very ill, such as patients in intensive care units. The number of patients with serious bloodstream infections due to acinetobacter is much lower than those caused by MRSA. However, antibiotic resistant forms of A. baumannii occur and can be difficult to treat.

It is important to distinguish colonisation from infection to avoid the unnecessary use of antibiotics, which may make the clinical situation worse.

Is this a superbug?

Not really. Acinetobacters have been around in clinical practice for a long time. As stressed above, they are frequent colonisers and common contaminants of the environment. They have always been fairly antibiotic-resistant. Increased susceptibility of patients - e.g. those undergoing treatment for cancer or leukaemia- has increased the prevalence of colonisation.

Are they a real problem?

A. baumannii is intrinsically resistant to most commonly available antibiotics, hence it is able to survive in the hospital environment, and also to colonise susceptible patients on broad spectrum antibiotics. Strains that cause infection are liable to be more resistant than colonising strains. Injudicious use of antibiotics, particularly fluoroquinolones (e.g. ciprofloxacin) or carbapenems (e.g. imipenem) leads to the emergence of more resistant forms of colonising strains.

Occasional strains are resistant to ALL antibiotics currently available, including second-line aminoglycosides, such as amikacin, and extended spectrum cephalosporins. Recommended therapy is- when possible and prudent- to withhold antibiotics and allow the patient to recover.

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