Guidance

[Withdrawn] Working party guidance on the control of multi-resistant Acinetobacter outbreaks

Published 29 August 2006

This guidance was withdrawn on 24 January 2023

This guidance is out of date. See further information on Acinetobacter spp. bacteraemia.

1. Background

Many hospitals in England are encountering problems with multi-resistant Acinetobacter spp. Attempts to limit the spread of such strains led to calls for guidance on control. In the absence of national guidelines and a systematic review of the subject, this expert guidance was developed by a working group representing the Association of Medical Microbiologists (AMM), British Society for Antimicrobial Chemotherapy (BSAC), Public Health England (formerly Health Protection Agency), Hospital Infection Society (HIS), Infection Control Nurses Association (ICNA), and Department of Health (DH).

It was issued on the Health Protection Agency website in June 2005 and further views were explored at 2 meetings of infection control teams from many of the affected hospitals, and relevant experts. This is the first update of the guidance and it is our intention to review it periodically in the light of new evidence for prevention and control.

2. Definitions

These vary in the literature. The working party has defined multi-resistant Acinetobacter spp ‘ MRAB’ as Acinetobacter spp isolates that are resistant to any aminoglycoside (eg gentamicin) and to any third generation cephalosporin (eg ceftazidime, cefotaxime). Those isolates that are additionally resistant to imipenem and/or meropenem are designated ‘MRAB-C’. Most MRAB-C are strongly clonal and belong to the South East clone (SE clone), or OXA-23 clone 1 lineages, both of which are established in multiple hospitals in London and southeast England. OXA-23 clone 1 is consistently susceptible only to polymyxin and, perhaps, tigecycline. Carbapenem susceptibility is variable in the SE clone, but it too is resistant to most antibiotics.

Antibiotic prescribing policies and audit should be in place for the treatment of these infections, although we are aware that this is not the case for some hospitals. Furthermore, some Trusts do not perceive a need for prevention and control measures, provided at least one aminoglycoside and a carbapenem are still active against the strain(s). Infection control teams in some other countries certainly take these more susceptible isolates seriously and the working group is also of this opinion.

3. Guidance for MRAB and MRAB-C incidents

Where a single patient is found to be colonised or infected, then ideally s/he should be contact isolated in a side-room and infection control and antimicrobial prescribing reviewed (see below). Risk assessment of the case should be performed and numbers and results of clinical specimens from other patients on the ward/unit reviewed to inform whether screening of other patients is indicated.

Risk factors for colonisation or infection should be reviewed, including intensive care or burns unit admissions, prolonged length of hospital stay, presence of surgical and other wounds, broad spectrum antibiotic treatment including carbapenem usage (see below), urinary and vascular catheters, ventilation and parenteral nutrition.

Where there is more than one patient isolate of a similar antibiogram on the same ward/unit, an outbreak team should be convened and an investigation undertaken. Case definitions should be agreed and dates of admission and discharge, ward and bed locations of all infected and colonised patients documented, along with time line analysis of patient activity such as movement to, and from, theatre, and for bronchoscopy.

There should be regular outbreak meetings with all relevant healthcare workers and senior managers to feedback key information, review the success of interventions and make new plans, as appropriate.

Choice of antibiotic will normally be governed by local information about trends in antibiotic resistance or a known sensitivity of the organism. A cluster of MRAB should trigger a review of antibiotic prescribing and, where cases are continuing, an audit of antimicrobial usage should be undertaken and the findings discussed with the relevant healthcare workers.

Efforts should be made to minimize antimicrobial prescribing in general and broad-spectrum agent use in particular. Specific recommendations regarding restriction of named antibiotic classes, such as carbapenems for MRAB-C, may be appropriate in some circumstances, but will need local assessment and review.

Patient and environmental screening strategies should be agreed locally, including monitoring the effectiveness of interventions. Screening sites that have been advocated include the nose, throat, perineum and any wounds, sputa, tracheostomy sites, the hair-line (to detect dispersers), faeces and ante-cubital fossa.

Appropriate isolates should be referred to the reference laboratories, after discussion with them, for further characterisation and typing to explore epidemiological hypotheses and the success or otherwise of interventions.

Risk assessment should be performed for all cases, and an isolation strategy and any other interventions agreed with the Infection Control Team, all relevant healthcare workers, and senior managers.

Where patients infected or colonised with MRAB, or exposed to it but screened and thought to be clear, are being transferred to another hospital, clinical staff should ensure that the receiving area is aware of the patient’s MRAB status and the context of the MRAB exposure, and the Infection Control Team at that hospital should be informed. This needs to happen before the transfer takes place. Colonisation with MRAB, as for other multiple-resistant organisms, must never be a reason for refusing admission if there are clear clinical reasons for the transfer.

All infection control procedures should be reviewed and re-inforced or corrected, including hand decontamination, correct use of gloves, suctioning practices, and device usage. Some centres recommend the use of patient decontamination regimens using antiseptic preparations, such as chlorhexidine or triclosan, to reduce the bacterial loads on patients.

Instruments or equipment (eg writing materials, sphygmomanometers, stethoscopes, lifting slings, and resuscitator bags) should be designated for affected patients. If possible, single-patient use items are to be preferred. Alternatively, such items should be decontaminated suitably before use on another patient. Special attention should be paid to ventilator circuits, suction catheters and humidifiers. A cluster of MRAB cases should trigger an audit and review of these measures and root cause analysis may also help identify and address the factors contributing to acquisition and transmission of infection in a hierarchical way.

The area in which the patient was cared for should be cleaned after the patient’s discharge according to the local disinfection policy (see below).

Methods of cleaning should remove dirt without redistributing it, including the use of damp dusting, vacuum cleaners with high efficiency filters fitted to their exhausts and single-use, or thermally disinfectable, mops.

Especial attention should be paid to horizontal surfaces and dust-collecting areas, bedclothes, curtain rails, beds, tables, ventilators, sinks, doorknobs, and telephones. Curtains should be changed as part of the terminal clean after an infected/colonised patient leaves. Where a curtain forms a common divider between two beds, it should be changed when one patient leaves. Easily decontaminated computer keyboards, for example those with flat sealed membranes, should be used. Electrical equipment that generates static need particular attention.

Acinetobacter can contaminate stock items stored in a patient’s room. Following a patient’s departure, any such items in a room should be decontaminated adequately or disposed of. All unused disposable items such as packets of unopened gloves, needles etc, should be discarded. Stocks of these should thus be kept to the minimum needed for the care of that patient, so that wastage is minimised .

The infection control team should make a decision on whether a disinfectant is needed: chlorine-based agents ( eg sodium dichloroisocyanurate) at 1,000 ppm available chlorine with a compatible anionic detergent if required should be recommended. In case of corrosion problems, 70% alcohol should be used.

Pillows, duvets, mattress covers and mattresses should be similarly disinfected or discarded if damaged. Therapy beds need specialist cleaning (eg high quality thermal washing/disinfection). Special mattresses must be cleaned after patient use according to manufacturers’ instructions.

Where cases are continuing, rather than closing and emptying the affected units, infected/colonised patients can be cohorted in distinct areas with totally separate ancillary facilities such as sluices and cleaning equipment. Faced with this situation, we recommend that the cohorted area has its own nursing staff. We are aware that some hospitals have extended this cohorting to physiotherapists and medical staff. Where this is not possible, it is even more important that nursing staff enforce strict infection control discipline for all visiting staff.

One should consider closing affected wards and performing thorough decontamination of the environment and all equipment once the final patient has left, as part of a terminal clean. MRAB can survive well in dust, much of which originates from patients’ skin. Thus it is important to remove all dust as part of this terminal clean.

This terminal clean should be co-ordinated by the Infection Control Team or link staff because, although easily accessible hard surfaces are cleaned by normal domestic staff, other items, such as electrical equipment, mattress and pillow covers and high surfaces such as air vents, will often require cleaning by other staff groups.

Some Infection Control teams have noticed that outbreaks have tended to occur at times of staff pressure, particularly nursing and cleaning. The importance of adequate staffing needs to be an issue identified on the Trust risk register as appropriate.

Further useful information and references can be found on the John Hopkins Medicine website.

4. Appendix: Acinetobacter media

A trial of selective media carried out. Berlau et al. Eur J Clin Microbiol & Infect Dis 1999, 18: 179-83, found that a minimal salt acetate (MSA) medium was marginally superior in selectivity over the Leeds Acinetobacter medium of Jawad et al. J Clin Microbiol 1994, 3: 2353-8.

The formula of MSA is as follows:

• Salt solution. 20g NH 4Cl, 4g NH 4NO 3, 8g Na 2SO 4, 12g K 2HPO 4, 4g KH 2PO 4, 0.4g MgSO 4.7H 2O per litre of deionised water.
• Agar base. 20g/L Agar No.3 (Oxoid)
• Add 250 ml of salt solution to 750 ml of agar base, 10 ml of 20% glucose solution and sodium acetate to 1% final concentration.

Break swabs in 5ml of 1% acetate salt solution [the above salt solution, 250ml, sterile distilled water, 750ml 10ml of 20% glucose sodium acetate to final concentration 1%], shake vigorously overnight at 30°C and plate suspension on MSA agar.

This medium permits good growth of all Acinetobacter spp. known at the time of formulation but was suppressive of a wide range of gram negative rods with the exception of Pseudomonas spp.

Further selection against P. aeruginosa may be achieved by incorporating meropenem 5 mg/L and for gram positives, vancomycin 5 mg/L (Parthasarathy P, Soothill J, J Hosp Infect 2005, 61: 357-8) but this has not as yet been confirmed independently.These workers make the media up freshly and we cannot yet advise on shelf life.

Dr Ty Pitt (Laboratory of Healthcare Associated Infection, PHE) would recommend the use of MSA preceded by enrichment in the above 1% acetate salt solution for screens of environmental and clinical specimens. If one is seeking carbapenem resistant strains then the inclusion of meropenem (5mg/L) would provide further specific selection.

We suggest that you test this media on isolates from your local outbreak at high (~1000 cfu) and low (~100 cfu) inocula before using it for screening. Dr Ty Pitt would be happy to receive feed-back from hospitals using the media on shelf life, sensitivity, and specificity.

4.1 Working Party members

The Members of the Working Party are:

• Prof. Barry Cookson (PHE, AMM): Chairman
• Dr Bernadette Gergonne (EPIET Fellow, PHE):Secretary
• Dr Stephen Barrett (HIS)
• Dr Paul Chadwick (BSAC)
• Dr Georgia Duckworth (PHE)
• Ms Carly Hall (ICNA)
• Mr Peter Hoffman (PHE)
• Dr Robert Hill (PHE)
• Dr Alan Johnson (PHE)
• Dr Deirdre Lewis (PHE)
• Dr David Livermore (PHE)
• Dr Geoff Ridgway (DH)
• Dr Bharat Patel (PHE)
• Dr Tyrone Pitt (PHE)
• Dr Louise Teare (AMM)
• Dr David Tompkins (PHE)
• Dr Kevin Towner (NHS)