International Journal of Antimicrobial Agents 27 (2006) 505–512 Integron presence in a multiresistant Morganella morganii isolate Laura Rojas a , Teresa Vinuesa a , Fe Tubau a , Consol Truchero a,b , Roland Benz c , Miguel Vi˜ nas a,∗ a Section of Microbiology, Department of Pathology and Experimental Therapeutics, Campus de Bellvitge, University of Barcelona, Barcelona, Spain b Intensive Care Unit, Medical and Dental Schools and IDIBELL, Campus de Bellvitge, University of Barcelona, Barcelona, Spain c Lehrstuhl f¨ ur Biotechnologie, Theodor Boveri Institut, University of W¨ urzburg, W¨ urzburg, Germany Received 24 November 2005; accepted 12 January 2006 Abstract A multiresistant strain of Morganella morganii was isolated from a patient affected by several severe pathologies. The isolate was found to be resistant to the following antimicrobials: ampicillin, nalidixic acid, cefalothin, cefoxitin, ceftriaxone, ciprofloxacin, chloramphenicol, streptomycin, erythromycin, gentamicin, novobiocin, penicillin, rifampicin, tetracycline and violet crystal. Mechanisms leading to this multi- resistance were studied. Porins of M. morganii multiresistant and wild-type strains were analysed by sodium dodecylsulphate–polyacrylamide gel electrophoresis (SDS–PAGE) and were characterised by their ability to form channels in planar black lipid bilayers. The channels formed by porins from multiresistant and susceptible strains suggested that the porins of the multiresistant strain were not responsible for resistance. A 6.6 kb plasmid (pML2003) was detected, isolated and studied. pML2003 included two integrons. Direct sequencing revealed that one of the integrons contained two cassettes, aminoglycoside adenyltransferase (aadB) and chloramphenicol acetyltransferase (catB3) conferring resistance to aminoglycosides and chloramphenicol, respectively. The second integron contained carbenicillinase (blaP1b) and adenyltransferase (aadA2), which confer resistance to -lactamases and streptomycin, respectively. © 2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. Keywords: Morganella morganii; SDS–PAGE; Multiresistance 1. Introduction The opportunistic pathogen Morganella morganii is com- monly isolated from human faeces and is frequently involved in urinary tract infections [1]. It is currently isolated from patients located in hospital Intensive Care Units [2]. More- over, it has been involved in various infectious processes such as neonatal septicaemia [3], abdominal abscesses, biliary infections and primary bacteraemia [4–6]. In compromised patients, M. morganii has been involved in chorioamnioni- tis, diabetic foot infections, pyomyositis [7], pyoarthritis, pericarditis and meningitis [8]. Nosocomial infections have also been reported. It is assumed that this species is intrin- sically susceptible to most of the antibiotics active against Gram-negative bacilli, such as aminoglycosides, carbeni- ∗ Corresponding author. E-mail address: mvinyas@ub.edu (M. Vi˜ nas). cillin, chloramphenicol, ciprofloxacin and acid nalidixic, but is resistant to fosfomycin, colistin and some -lactams, usu- ally owing to a chromosomal cephalosporinase [9–12]. The role of salicylate in decreasing the production of -lactamase has been documented [13]. Other resistances to -lactams related to mutational overproduction of the species-specific AmpC enzyme [14] and the occurrence of an extended- spectrum -lactamase in M. morganii have been reported [15]. Integrons are site-specific recombination systems able to capture and mobilise antibiotic resistance genes and play a major role in the dissemination of antibiotic resistance genes in Gram-negative bacteria [16,17]. The essential components of the integron include the intI gene, a recombination site (attI) and a promoter (P ant ), which code for an integrase, insertion of gene cassettes and transcription of the inserted cassette, respectively. Gene cassettes usually contain a single open reading frame and a recognition site for the integrase 0924-8579/$ – see front matter © 2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved. doi:10.1016/j.ijantimicag.2006.01.006