Distribution of class 1 and class 2 integron types among ESBL-producing Enterobacteriaceae recovered from Portuguese hospitals

Abstract number: p924

Machado  E., Cantón  R., Baquero  F., Sousa  J., Coque  T., Peixe  L.


To analyse the overall prevalence and distribution of class 1 and class 2 integron types among ESBL-producing Enterobacteriaceae from different Portuguese nosocomial environments.


We studied 105 ESBL-producing Enterobacteriaceae recovered from patients attending at Portuguese hospitals (Oct 2002–May 2004): 41 Klebsiella pneumoniae (KP), 6 Klebsiella oxytoca, 37 Escherichia coli (EC), 10 Enterobacter aerogenes (EA), 3 Enterobacter cloacae, and 8 Proteus mirabilis (PM). Bacterial identification was performed by the Vitek System. Antibiotic susceptibility was performed by the standard disk diffusion method. ESBL expression was searched by the double disk synergy test. Characterization of ESBL was performed by IEF, PCR for blaTEM, blaSHV, blaCTX-M, and sequencing. Class 1 and 2 integrons were searched by PCR, typed by RFLP using AluI and TaqI as restriction enzymes, respectively, and identified by sequencing (one per RFLP type).


ESBL among the isolates studied were identified as 53 TEM, 28 SHV, and 25 CTX-M. Class 1 integrons were more prevalent than class 2 integrons (70% vs 5%). Presence of class 1 integrons was higher among TEM (46/53, 87%) than among the other ESBL—types-producing isolates (19/28, 68% for SHV; 7/25, 28% for CTX-M), and among KP, EA, and PM isolates (85%, 100%, and 100%, respectively). Class 2 was only detected among TEM-producing EC and PM (5/53, 10%). Eight different class 1 integrons were found, each containing different gene arrangements: A) aacA4, B) aadA1, C) aadA2, D) dfrA10-aadA1, E) dfrA17-aadA5, F) drfA12-orfF-aadA2, G) aac3Ia''-orfX- -aadA1, and H) aac6'Iic-orf. Type A was the most frequently found and observed in all TEM-24 producing isolates. Type B was associated to isolates producing SHV-55. For CTX-M-producing isolates we only detected the presence of Type E (3 CTX-M-14), and F (1 CTX-M-15). Types C, D, G, and H were only detected in isolates harbouring SHV-2, TEM-52, TEM-110 and SHV-12, respectively. Only one class 2 integron type was found (dfrA1-sat1-aadA1). Ten isolates harboured two class 1 integrons of different size and in four strains was observed simultaneous presence of class 1 and 2 integrons.


Class 1 integrons are widely distributed among ESBL-producing Enterobacteriaceae from Portuguese hospitals. A low diversity of integron types was observed, some of them being detected only in strains producing a specific ESBL which suggests their co-transference in mobile elements.

Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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