GES-11-producing Acinetobacter baumannii clinical isolates from Tunisian hospitals: Long-term dissemination of GES-type carbapenemases in North Africa.

Acinetobacter baumannii is an emerging threat in healthcare facilities owing to its ability to be multidrug-resistant (MDR) and to be involved in outbreaks. GES-type extended-spectrum ß-lactamases (ESBLs) have been increasingly identified in A. baumannii. In this study, clinical A. baumannii isolates were characterised using standard biochemical methods and antibiotic susceptibility testing. Antibiotic resistance genes were sought by PCR and sequencing. Genetic support was characterised using S1 nuclease pulsed-field gel electrophoresis (PFGE) mapping, conjugation and electroporation assays. The genetic environment was investigated by PCR, and genetic relatedness was investigated by PFGE. Two MDR A. baumannii clinical isolates susceptible only to colistin and rifampicin were isolated from a tracheal aspirate of a 49-year-old woman hospitalised in 2006 at the Military Hospital of Tunis, Tunisia, and from a tracheal aspirate of a 53-year-old man hospitalised in 2010 at the Institut Orthopédique Mohamed El Kassab of Tunis, Tunisia. PCR revealed that the two isolates harboured the acquired carbapenemase blaOXA-23 and ESBL blaGES-11 genes along with chromosomally-encoded blaOXA-51 and blaADC-like genes. PFGE revealed that these A. baumannii isolates were unrelated; nevertheless, plasmid analysis revealed a similar sized plasmid following electrophoresis of the isolates. In addition, A. baumannii CIP70.10 transformants displayed similar resistance patterns. blaGES-11 was integron-borne and the ISAbaI element was identified upstream of blaOXA-23 and blaADC-like. Here we described two unrelated clinical A. baumannii isolates producing GES-11 ESBL and OXA-23 carbapenemase from two Tunisian hospitals. This work further illustrates the emergence of GES-type ß-lactamases in A. baumannii in North Africa as early as 2006.

First characterisation of plasmid-mediated quinolone resistance-qnrS1 co-expressed bla CTX-M-15 and bla DHA-1 genes in clinical strain of Morganella morganii recovered from a Tunisian Intensive Care Unit.

PURPOSE: Aim of this study was to show the emergence of the qnr genes among fluoroquinolone-resistant, AMPC and ESBL (extended-spectrum-beta-lactamase) co-producing Morganella morganii isolate. MATERIALS AND METHODS: A multi resistant Morganella morganii SM12012 isolate was recovered from pus from a patient hospitalized in the intensive care unit at the Military hospital, Tunisia. Antibiotic susceptibility was tested with the agar disk diffusion method according to Clinical and Laboratory Standards Institute guidelines. ESBLs were detected using a standard double-disk synergy test. The characterization of beta-lactamases and associated resistance genes were performed by isoelectric focusing, polymerase chain reaction and nucleotide sequencing. RESULTS: The antimicrobial susceptibility testing showed the high resistance to penicillins, cephalosporins (MICs: 64-512 µg/ml) and fluoroquinolones (MICs: 32-512 µg/ml). But M. morganii SM12012 isolate remained susceptible to carbapenems (MICs: 4-<0.25 µg/ml). The double-disk synergy test confirmed the phenotype of extended-spectrum ß-lactamases (ESBLs). Three identical ß-lactamases with pI values of 6.5, 7.8 and superior to 8.6 were detected after isoelectric focusing analysis. These ß-lactamases genes can be successfully transferred by the conjugative plasmid. Molecular analysis demonstrated the co-production of bla (DHA-1), bla (CTX-M-15) and qnrS1 genes on the same plasmid. The detection of an associated chromosomal quinolone resistance revealed the presence of a parC mutation at codon 80 (Ser80-lle80). CONCLUSION: This is the first report in Tunisia of nosocomial infection due to the production of CTX-M-15 and DHA-1 ß-lactamases in M. morganii isolate with the association of quinolone plasmid resistance. The incidence of these strains invites continuous monitoring of such multidrug-resistant strains and the further study of their epidemiologic evolution.

Identification of plasmid-encoded extended spectrum beta-lactamases produced by a clinical strain of Proteus mirabilis.

Emergence and dissemination of multiresistant strain of Proteus mirabilis have made infections treatment more difficult that this bacterium is responsible. The aim of this study is to determine the implication of the enzymatic mechanism and to describe the properties of ESBLs (extended spectrum beta-lactamases). A clinical strain of Proteus mirabilis SM514 isolated in the intensive care unit at the Military hospital in Tunisia during the period 2004 was found to be highly resistant to cephalosporins and penicilins. Cells sonicate of the isolate hydrolysed cefotaxime more efficiently than ceftriaxone and ceftazidime and had three beta-lactamases bands of approximate of isoelectric points (pI) of 5.4; 5.6 and superior to 7.6. The specific activities (AS) vary from 5.26 to 7.77U/mg of protein respectively for cefotaxime and the benzylpenicillin. These activities are inhibited by the clavulanic acid and the sulbactam. The values of the IC(50) are respectively 3.7 and 11.7muM. Only the beta-lactamases of pI 5.4 and superior to 7.6 hydrolyze the cefotaxime. Transformant produces the ESBLs of pI 5.4; 7.45 and greater than 7.6. The genes coding for this enzymes are carried by a transferable plasmids.