An unwanted import to the UK: a carbapenem-resistant clinical isolate of Acinetobacter baumannii producing metallo-ß-lactamase

Kevin J. Towner1,*, Thekli Gee1 and Tim Boswell2

1 Public Health Laboratory, University Hospital, Queen’s Medical Centre, Nottingham NG7 2UH; 2 Department of Microbiology, Nottingham City Hospital, Nottingham NG5 1PB, UK

Keywords: Acinetobacter, carbapenemase, carbapenems, metallo-ß-lactamase, resistance

Sir,

A recent survey published in the Journal of Antimicrobial Chemotherapy found that carbapenems remained active against 98% of Acinetobacter baumannii isolates collected during 2000 from 54 sentinel laboratories throughout the UK.1 However, numerous reports of carbapenem resistance in Acinetobacter spp. have now accumulated in other countries worldwide.2 Carbapenem-resistant strains of A. baumannii have mostly been sporadic in northern Europe, but appear to be endemic in some southern European countries, including parts of Spain.3 We report here details of an A. baumannii isolate imported into the UK that exhibited carbapenem resistance associated with production of a class B metallo- ß-lactamase.

The organism was isolated from the sputum of a 68-year-old lady who suffered from chronic obstructive pulmonary disease. The patient had been on holiday in Spain. Towards the end of her stay she developed an acute exacerbation of her lung disease that did not improve with antibiotics given to her by the hotel’s doctor. At the airport, about to embark on her return journey, her condition deteriorated and she was admitted to Alicante University Hospital. She was promptly intubated and ventilated for type II respiratory failure and was transferred to the ICU where she remained for 4 weeks. According to the eventual transfer letter (in Spanish), the patient was treated initially with cefotaxime and clarithromycin. During the course of her admission it was noted that >106 cfu of A. baumannii were isolated from a bronchial aspirate. The susceptibility pattern of the isolate at this stage was not mentioned in the transfer letter, but it was stated that she was also treated in Alicante with colistin. The patient was transferred from Spain to the Nottingham City Hospital ICU once her condition had stabilized. At this stage there were no obvious signs of infection and no antibiotic therapy was given. Three days after transfer, carbapenem-resistant A. baumannii (also multiply resistant to other agents) was isolated from sputum. Such an event is considered to warrant prompt microbiological and epidemiological interventions,4 and strict infection control isolation measures were immediately implemented. The patient was treated successfully with intravenous amikacin and nebulized colistin, despite what would be regarded as borderline susceptibilities (MICs 8–16 mg/L), and was eventually discharged. No similar isolates were obtained from other patients on the ICU at the same time, or in the 5 months subsequently.

The resistant organism was confirmed as A. baumannii by the technique of tRNA spacer fingerprinting.5 Examination of the isolate with MBL Etests (Cambridge Diagnostics Services, Cambridge, UK) revealed an imipenem MIC of 64 mg/L in the absence of EDTA and an imipenem MIC of <1 mg/L in the presence of EDTA, thereby indicating production of a metallo-ß-lactamase. PCR1 indicated that the enzyme was most likely to be a blaIMP derivative, but this needs to be confirmed by more detailed analysis. PCRs for blaVIM and blaOXA-type genes1 were negative. This finding is unusual as the majority of carbapenem-resistant isolates of A. baumannii from Spain produce class D OXA-type carbapenemases.

To our knowledge, the only previous confirmed report in the UK of a class B carbapenemase from a clinical isolate of Acinetobacter involved a strain of Acinetobacter junii—an organism associated only rarely with clinically significant infection—which expressed only borderline resistance to carbapenems.6 In contrast, the isolate of A. baumannii imported to Nottingham expressed relatively high-level resistance (imipenem MIC 64 mg/L) and it was fortunate that the organism did not spread to other susceptible patients and become established within the ICU. It is important to be aware that such enzymes are now apparently endemic in A. baumannii, particularly in certain parts of southern Europe and the Far East. Continued vigilance and screening of patients transferred from ICUs abroad, with implementation of appropriate infection control measures when necessary, are required to ensure that such unwanted imports are not introduced into (currently) problem-free geographical areas when patients are repatriated.

Footnotes

* Corresponding author. Tel: +44-115-970-9163; Fax: +44-115-942-2190; E-mail: ktowner{at}trent.phls.nhs.uk Back

References

1 . Henwood, C. J., Gatward, T., Warner, M., James, D., Stockdale, M. W., Spence, R. P. et al. (2002). Antibiotic resistance among clinical isolates of Acinetobacter in the UK, and in vitro evaluation of tigecycline (GAR-936). Journal of Antimicrobial Chemotherapy 49, 479–87.[Abstract/Free Full Text]

2 . Afzal-Shah, M., Woodford, N. & Livermore, D. M. (2001). Characterization of OXA-25, OXA-26, and OXA-27, molecular class D ß-lactamases associated with carbapenem resistance in clinical isolates of Acinetobacter baumannii. Antimicrobial Agents and Chemotherapy 45, 583–8.[Abstract/Free Full Text]

3 . Corbella, X., Montero, A., Pujol, M., Dominguez, M. A., Ayats, J., Agerich, M. J. et al. (2000). Emergence and rapid spread of carbapenem resistance during a large and sustained hospital outbreak of multiresistant Acinetobacter baumannii. Journal of Clinical Microbiology 38, 4086–95.[Abstract/Free Full Text]

4 . Richet, H. M., Mohammed, J., McDonald, L. C. & Jarvis, W. R. (2001). Building communication networks: international network for the study and prevention of emerging antimicrobial resistance. Emerging Infectious Diseases 7, 319–22.[ISI][Medline]

5 . Ehrenstein, B., Bernards, A. T., Dijkshoorn, L., Gerner-Smidt, P., Towner, K. J., Bouvet, P. J. et al. (1996). Acinetobacter species identification by using tRNA spacer fingerprinting. Journal of Clinical Microbiology 34, 2414–20.[Abstract]

6 . Tysall, L., Stockdale, M. W., Chadwick, P. R., Palepou, M.-F. I., Towner, K. J., Livermore, D. M. et al. (2002). IMP-1 carbapenemase detected in an Acinetobacter clinical isolate from the UK. Journal of Antimicrobial Chemotherapy 49, 217–8.[Free Full Text]