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Variation in the genetic environments of blaCTX-M-15 in Escherichia coli from the faeces of travellers returning to the United Kingdom

2011; Oxford University Press; Volume: 66; Issue: 5 Linguagem: Inglês

10.1093/jac/dkr041

1460-2091

H. Dhanji, RK Patel, R.A. Wall, Michel Doumith, Biren A. Patel, Russell Hope, David M. Livermore, Neil Woodford,

Veterinary medicine and infectious diseases

The genetic surroundings of blaCTX-M-15 in Escherichia coli recovered from faeces of travellers returning to the UK from overseas were compared with those among established UK strains to provide further insights into the spread of blaCTX-M-15 in the UK. From August 2006 to January 2008, 1031 faecal specimens were collected at the North West London NHS Trust from general practice patients with a clinical history of diarrhoea following recent international travel. Cefuroxime-resistant E. coli were isolated on cystine-lactose-electrolyte deficient agar and those that produced extended-spectrum β-lactamases (ESBLs) were identified by double disc synergy test (DDST). The molecular environments surrounding blaCTX-M-15 were investigated by PCR, DNA sequencing, gene cloning and northern blotting. 182/1031 (18%) E. coli isolated from returning travellers gave a positive DDST, and were confirmed by PCR to produce CTX-M ESBLs; 174 (96%) had blaCTX-M-15, including 21 belonging to clone ST131. Among these 174 isolates, the environment upstream of blaCTX-M-15 consisted of either: (i) an intact ISEcp1 (n = 108); (ii) various lengths of truncated ISEcp1 (n = 58); or (iii) a 24 bp remnant of ISEcp1 (n = 8). Two different promoters were found to transcribe blaCTX-M-15, resulting in different levels of cephalosporin resistance. E. coli with CTX-M-15 ESBL from returning travellers harboured previously seen UK blaCTX-M-15 genetic environments (intact or 24 bp remnant of ISEcp1) as well as blaCTX-M-15 genetic environments previously unseen in the UK (various lengths of truncated ISEcp1), which suggest overseas acquisition and highlight the difficulty of control in a time of population mobility and travel.